TECHNICAL FIELD
The present description relates generally to watercraft lifting bodies that generate buoyant lift and dynamic lift during watercraft operation.
BACKGROUND/SUMMARY
Hydrofoils and lifting bodies have been used in watercrafts to enhance various aspects of watercraft performance such as increasing seakeeping and sea-kindliness, which may be particularly useful for watercrafts that are intended to operate in rough prevailing seas. For instance, attempts have been made to design certain hydrodynamic lifting bodies to achieve increased added mass motion damping, reduced friction drag by increasing dynamic lift that reduces hull immersion and hull wetting, and increased wave excitation dampening.
The inventors have recognized a need to further increase seakeeping and the full load displacement of watercrafts in comparison to previous watercraft lifting bodies. To elaborate, the inventors have specifically recognized that further increasing the watercraft's full load displacement enables the watercraft to achieve increased payload and fuel capacity, increased watercraft efficiency, or some combination thereof. The inventors have also recognized a desire to enhance watercraft motion control using motion stabilizing systems that employ active control surfaces.
The inventors have developed a watercraft system to achieve at least a portion of the aforementioned watercraft performance characteristics. The watercraft system includes, in one example, a lifting body configured to attach to a hull of a watercraft and generate dynamic lift during watercraft operation. In the watercraft system, an aspect ratio of the lifting body is less than two. Further, in the watercraft system, the lifting body includes multiple parabolic curves that define a leading edge of the lifting body. Even further in the watercraft system, the lifting body has a chord that decreases from a center of the lifting body to each lateral edge of the lifting body. Additionally, in the watercraft system, the lifting body twists from a central section to each of the lateral edges. Designing the lifting body with the aforementioned characteristics allows the watercraft to achieve increased efficiency and increased full load operating displacement which correspondingly increases watercraft payload capacity. In particular, the lifting body described above mitigates bow wave making at lower speeds (e.g., critical speeds), increases dynamic lift, and generates strong downwash. Additionally, designing the lifting body with twist and a profile that tapers the chord and fore-aft cross-section decreases drag for a given lift and root bending moment, thereby increasing the hydrodynamic efficiency of the lifting body in comparison to previous lifting bodies. Utilizing the lifting body with a twist in conjunction with a tapered chord and fore-aft cross-section in the watercraft enhances aspects of the watercraft's handling performance. The watercraft's customer appeal may be expanded as result of the handling performance gains, efficiency gains, and increased payload capacity.
Further, in another example, a watercraft system is provided that includes a lifting body which is configured to generate dynamic lift during watercraft operation in addition to static lift, also referred to as buoyancy. The lifting body includes two opposing lateral portions that extend laterally outward and aft from a central section. Further, in the watercraft system, the two opposing lateral portions generate a greater amount of dynamic lift than the central section, which produces primarily static lift. The lifting body described above allows increased volume to be placed forward in the lifting body and allows a stronger restoring moment to be applied to the hull. Further, the central section may have a higher volume than the lateral portions, thereby increasing wave cancellation due to the forward placement of the higher volume central section. To elaborate, the lifting body's low-speed bulbous bow effect is enhanced, and the lifting body's bow wave drag at lower speeds is reduced.
In yet another example, a watercraft system is provided that includes a lifting body that is coupled to a watercraft hull and configured to generate dynamic lift during watercraft operation. The watercraft system further includes a hydrofoil that is coupled to the watercraft hull and positioned behind the lifting body in a fore-aft direction. Further, in the watercraft system, the hydrofoil has a higher vertical location on the watercraft hull in comparison to the lifting body. In this way, the lift is able to be distributed in a lifting body structure that can be effectively incorporated into larger watercrafts, if desired. However, it will be appreciated that the lifting body described above and the other lifting bodies described herein may be incorporated into a wide variety of watercrafts of varying sizes and types. Further, the use of the lifting body and the hydrofoil in the manner described above allows the downwash of the watercraft to be magnified, thereby reducing the watercraft's frictional drag due to hull unwetting.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a watercraft with a first example of a lifting body that is coupled to a hull of the watercraft.
FIGS. 2A-2D are different views of the lifting body, depicted in FIG. 1.
FIG. 3 is a cross-sectional view of the lifting body, depicted in FIG. 1.
FIG. 4 is a graph of an exemplary twist (rotated about a leading edge) vs span corresponding to the lifting body, depicted in FIG. 1.
FIG. 5 is a bell-shaped lift distribution curve corresponding to the lifting body, depicted in FIG. 1.
FIGS. 6A-6D are different views of a second example of a lifting body.
FIG. 7 is a cross-sectional view of the lifting body, depicted in FIGS. 6A-6D.
FIG. 8 is a graph of an exemplary twist (rotated about a leading edge) vs span corresponding to the lifting body, depicted in FIGS. 6A-6D.
FIG. 9 is a bell-shaped lift distribution curve corresponding to the lifting body, depicted in FIGS. 6A-6D.
FIGS. 10A-10D are different views of a third example of a lifting body.
FIG. 11 is a perspective view of a watercraft with the lifting body, depicted in FIGS. 10A-10D, coupled to a hull.
FIGS. 12A-12D are different views of a fourth example of a lifting body.
FIG. 13 is a graph of an exemplary twist (rotated about a leading edge) vs span corresponding to the lifting body, depicted in FIGS. 12A-12D.
FIG. 14 is a bell-shaped lift distribution curve corresponding to the lifting body, depicted in FIGS. 12A-12D.
FIGS. 15-17 are different views of exemplary watercraft systems with a lifting body and a hydrofoil.
FIG. 18 is an example of a watercraft with a bulbous bow.
FIG. 19 is an example of a watercraft with a lifting body that replaces a bulbous bow.
DETAILED DESCRIPTION
Watercraft systems with lifting bodies that are designed to achieve increased efficiency, increased seakeeping, and enhanced watercraft control in comparison to previous lifting bodies are described herein. To elaborate, the lifting body technology described herein allows watercrafts to significantly increase their full load displacement (i.e., maximum loaded displacement without the impacts of increased resistance usually associated with overloaded watercraft) across a wide speed range. In broader terms, at low to moderate speeds (e.g., critical speeds where the Froude number (Fr)<0.6, in one specific example), the increase in watercraft full load displacement stems from the mitigation of bow wave generation. Conversely, at higher watercraft speeds, the lifting bodies generate dynamic lift, thereby causing the vessel to heave to a shallower operating draft and reduce hull immersion and compensate for any additional load. The diminished hull immersion mitigates both friction and pressure drag and reduces wake generation. Moreover, the stronger downwash generated by the lifting bodies at the bow (in comparison to previous lifting bodies) may cause the hull forebody (e.g., especially from the critical hull shoulder and aft therefrom) to be unwetted, thereby reducing pressure and friction drag. Additionally, the stronger downwash is able to cancel wave generation, and energy correspondingly, to reduce watercraft resistance. Still further, the lifting bodies described herein may also achieve a bulbous bow effect due to the added volume and displacement that is positioned forward of the bow, which provides destructive wave cancellation. Additionally, in some examples, the watercraft system may include an aft-balancing lift device. The lift from the lifting body generates a bow-up moment about the hull's center of gravity. The aft-balancing lift device functions to provide a restoring moment in relation to this bow-up moment. The aft-balancing device may take the form of an interceptor, a transom flap, a transom foil, a bilge foil, combinations thereof, and the like. In some examples, the lifting bodies may replace a bulbous bow in a watercraft or be added to a bulbous bow of a watercraft, in other examples. The lifting bodies may be attached to a hull of the watercraft using struts, in some embodiments. In these embodiments, the added mass from the lifting body strut and the lifting body itself counters undesirable watercraft motions (e.g., pitch, roll, and/or yaw), resulting in a more stable and efficient propulsion thrust line. This reduces the thrust loss component, which is known in the art as added resistance in a seaway. Still further, in some embodiments, watercraft motion control may be enhanced through the use of a motion stabilizing system in the watercraft. The motion stabilizing system may incorporate controllable trailing edge flaps on the lifting body and may also employ active control surfaces on the aft-balancing lift devices, in some cases.
US 2022/0135182 A1 to Loui et al. discloses different watercraft and lifting body configurations. The contents of US 2022/0135182 A1 are incorporated herein by reference. FIG. 1 shows a perspective view of an example watercraft 100 with a system 101 that includes a lifting body 102 which is designed to generate lift and a hull 104. As described herein, a lifting body is a hydrodynamic structure that generates dynamic lift. Further in some examples, the lifting body may additionally generate static lift. Alternatively, in another example, the lifting body may primarily generate dynamic lift.
The watercraft 100 includes a bow 106, a stern 108, a starboard side 110, and a port side 112. As described herein, fore refers to a direction extending toward the bow 106, while aft refers to a direction extending toward the stern 108. Additionally, inboard refers to a direction parallel to the y-axis, extending inward toward a centerline 114 of the watercraft 100. On the other hand, outboard refers to a direction parallel to the y-axis, extending outward away from the centerline 114 of the watercraft 100.
The watercraft 100 includes a single lifting body 102 in the illustrated example. However, additional lifting bodies, hydrofoils, combinations thereof, and the like may be included in the watercraft system in alternative examples, as discussed in greater detail herein with regard to FIGS. 15-17.
The lifting body 102 is designed to generate lift distribution profiles which taper near the lateral sides of the lifting body. The tapered lift distribution increases lifting body efficiency, seakeeping ability, and handling performance. Structural features which allow the lifting bodies to realize these the efficiency and handling performance gains are expanded upon herein.
The lifting body 102 may be directly coupled to the hull 104, in one example, or coupled to the hull using a strut or other suitable structures, in other examples. The lifting body 102 is designed to taper the lift generated during forward motion of the lifting body near the tips, as discussed in greater detail herein.
FIG. 1 further shows an aft-balancing lift device 116 that may be included in the watercraft system 101. The aft-balancing lift device 116 may be configured to balance lift that is generated by the lifting body 102. In the illustrated example, the aft-balancing lift device 116 is positioned above the lifting body 102. Using this aft-balancing lift device with this positioning allows a restoring moment to be applied to the hull. However, other suitable positions of the aft-balancing lift device have been envisioned. The aft-balancing lift device may be an interceptor, a transom flap, a transom hydrofoil, a bilge hydrofoil, combinations thereof, and the like.
The watercraft 100 may further include a control system 150 with a controller schematically depicted at 152. The controller 152 may include memory 154 and a processor 156. The memory 154 may store instructions executable by the processor 156 to perform control strategies, such as maneuvering strategies. Furthermore, the controller 152 may further receive control inputs from a watercraft operator to maneuver the watercraft as well as various watercraft sensors. The memory may include known data storage mediums such as volatile and non-volatile memory, such as random access memory (RAM) and read only memory (ROM), respectively, and the like. Further, the processor may include one or more microprocessors. The controller 152 may send control signals, commands, etc. to controllable components such as the adjustment mechanism and receive signals from sensors and/or components in the watercraft. It will therefore be understood that the controller 152 may be in electronic communication (e.g., wired and/or wireless communication) with the sensors and controllable components.
FIGS. 2A-2D shows different views of the lifting body 102, depicted in FIG. 1. The lifting body 102 provides both static and dynamic lift to the watercraft.
FIG. 2A shows the lifting body 102 with a central section 200. The central section 200 may have a parabolic shape. To elaborate, a leading edge 202 of the lifting body 102 and specifically the central section 200 has multiple parabolic curves 204 that define the shape of the leading edge. Although three parabolic curves are explicitly illustrated in FIG. 2A, it will be understood that the lifting body 102 as well as the other lifting bodies described herein with parabolic curves have a multitude of parabolic curves that define the shape of the leading edge. The lifting body 102 twists from the central section 200 to lateral edges 208, as discussed in greater detail herein with regard to FIGS. 3 and 4.
The lifting body 102 may further include a control surface 210 (e.g., a flap) at a straight portion 211 of a trailing edge 212. The control surface 210 may be configured to be adjusted in response to control commands to alter the lift generated by the lifting body 102. In this way, watercraft control is enhanced. It will be appreciated that the straight portion 211 of the trailing edge 212 allows for integration of the control surface 210 into the lifting body 102. In one example, the control surface 210 may include, at its base, a pivot/hinge about which the control surface can rotate, structural reinforcement at pivot/hinge area, an actuator to induce rotation of control surface, a coupler between the actuator and the control surface (e.g., a pushrod, a lever, a gear, combinations thereof, etc.), and the like. In other examples, the control surface may have alternate components and/or configurations. For instance, the control surface may use shape memory alloys and the like.
The trailing edge 212 and the other trailing edges of the lifting bodies described herein may be conformal trailing edges. To elaborate, the lifting bodies may have a nonlinear spanwise twist distribution for compatibility with trailing edge flap integration. This enables the use of a constant spanwise cross-section flap with a straight, single horizontal axis of rotation. Further, lifting body fabrication is simplified due to the constant spanwise cross-section. Further, the discontinuities at the lifting body and the flap hinge location are reduced due to the non-linear spanwise lift distribution. Further, the flaps function as control surfaces to facilitate hydrodynamic performance gains across a wider range of operating conditions.
FIG. 2B shows the lifting body 102 with the central section 200, the lateral edges 208, and the control surface 210. A lateral width 214 and a fore-aft length 216 are depicted in FIG. 2B. An aspect ratio defined as the width/length may be less than two. In this way, the lifting body is able to be more easily incorporated into or coupled to the hull.
A center of lift 218 of the lifting body with regard to a fore-aft direction is further depicted in FIG. 2B. The center of lift may be in the range of 40%-65% from the leading edge, in one example. In this way, the lifting body may achieve increased dynamic lift at lower to moderate Froude numbers. However, the center of lift may be arranged in an alternate location, in other embodiments.
A center 220 of the lifting body 102 with regard to a lateral direction is further indicated in FIG. 2B. A chord of the lifting body 102 decreased from the center 220 to the lateral edges 208, as discussed in greater detail herein.
Viewing planes A-A′ and B-B′, shown in FIG. 2B, indicate the cross-sections 302 and 300, shown in FIG. 3, respectively. Specifically, the cutting plane B-B′ is located at the lifting body's root, and cutting plane A-A′ is adjacent to one of the lateral tips of the lifting body.
FIGS. 2C and 2D show the lifting body 102 with the leading edge 202 with the parabolic curves 204. The central section 200 of the lifting body 102 is further depicted in FIGS. 2C and 2D. Lateral edges 208 of the lifting body are further illustrated in FIGS. 2C and 2D.
FIG. 3 depicts cross-sections of the lifting body 102 in fore-aft cutting planes. To elaborate, a fore-aft cross-section of the lifting body's root is indicated at 300, and a fore-aft cross-section of the lifting body's tip is indicated at 302. As shown, the cross-section of the lifting body decreases from the root to the tip. More generally, the fore-aft cross section of the central section differs in profile from the fore-aft cross section of the lateral edges. A tip chord 304 and a root chord 306 are further indicated in FIG. 3. The ratio between the tip chord and the root chord may be in the range between 0.1 and 0.5, in one specific example. Further, in one example, the lifting body may vary in volumetric distribution and span/sweep, be incorporated into anhedral or dihedral sections, and be asymmetric in plan, which may be particularly desirable when the lifting body is used in a multi-hull watercraft such as a catamarans and trimarans, for instance.
FIG. 4 shows a plot 400 of a use-case lifting body with twist on the ordinate and span on the abscissa. Twist is expressed in degrees, and although no numerical values are provided for span, the span increases from left to right. It will therefore be understood that the lifting body 102 shown in FIGS. 1-2D may have the twist and span profile exemplified in FIG. 4. However, other suitable profiles of the lifting body may be used, in other embodiments. The zero value of the span is indicated in the plot along with linear points of interest of both twist and span. In one use-case example, the lifting body's twist deviation may be approximately 5° (e.g., from −3° at the root to 2° at the tip), as measured from a horizontal plane. However, numerous twist and span combinations may be used. The lifting body's twist may be selected based on target handling characteristics. It has been found through computational fluid dynamics (CFD) modeling that if the lifting body has greater lift near the root and less lift near the tips, the lifting body's efficiency may not be sensitive to more granular adjustments to the lifting body's twist distribution. It will be appreciated that FIG. 4 depicts an example of a twist distribution that may result in a bell-shaped lift distribution. However, in alternate examples, other twist distributions may be used to achieve a bell-shaped lift distribution.
FIG. 5 shows a lift distribution plot 500 having a bell shape of an exemplary lifting body. Dynamic lift is on the ordinate and span is on the abscissa. Although no specific numerical values of lift and span are provided, lift and span increase along the corresponding axis. The bell-shaped plot may correspond the lifting body 102, shown in FIGS. 1-2D. To elaborate, the plot 500 includes a central convex section 502 and lateral concave sections 504. However, lifting bodies with alternate lift distribution curves lie within the scope of the disclosure. As shown, the bell-shaped lift distribution curve tapers near the lateral tip of the span. The tapered lift distribution allows vortices to be moved inward with a diminished magnitude to increase lifting body efficiency and handling performance.
FIGS. 6A-6D show another example of a lifting body 600. The lifting body 600 again includes a central section 602 and lateral edges 604.
In the example illustrated in FIG. 6A, the central section 602 has a parabolic shape. To elaborate, a leading edge 606 of the lifting body 600 and specifically the central section 602 has multiple parabolic curves 608 that define the shape of the leading edge. The lifting body 600 twists from the central section 602 to lateral edges 604, as discussed in greater detail herein with regard to FIGS. 7 and 8.
The lifting body 600 may further include a control surface 610 at straight portion 611 of a trailing edge 612. The control surface 610 may be configured to be adjusted in response to control commands from a controller to alter the lift generated by the lifting body 600. In this way, watercraft control is enhanced.
FIG. 6B shows the lifting body 600 with the central section 602, the lateral edges 604, and the control surface 610. A lateral width 614 and a fore-aft length 616 are depicted in FIG. 6B. An aspect ratio defined as the width/length may be less than two. In this way, the lifting body is able to be more easily incorporated into or coupled to the hull.
FIG. 6B specifically depicts a center of lift 618 of the lifting body with regard to a fore-aft direction. The center of lift may be in the range of 20%-40% from the fore end, in one example. In this way, the lifting body may achieve increased dynamic lift at moderate Froude numbers. However, the center of lift may be arranged in an alternate location, in other embodiments.
A center 620 of the lifting body 600 with regard to a lateral direction is further indicated in FIG. 6B. Again, a chord of the lifting body 600 decreased from the center 620 to the lateral edges 604, as discussed in greater detail herein.
Viewing planes C-C′ and D-D′, shown in FIG. 6B, indicate the cross-sections 702 and 700, shown in FIG. 7. Specifically, the cutting plane D-D′ is located at the lifting body's root, and cutting plane C-C′ is adjacent to one of the lateral tips of the lifting body.
FIGS. 6C and 6D show the lifting body 600 with the leading edge 606 with the parabolic curves 608. The central section 602 of the lifting body 600 is further depicted in FIGS. 6C and 6D. Lateral edges 604 of the lifting body are further illustrated in FIGS. 6C and 6D.
FIG. 7 depicts cross-sections of the lifting body 600 in fore-aft cutting planes. To elaborate, a fore-aft cross-section of the lifting body's root is indicated at 700, and a fore-aft cross-section of the lifting body's tip is indicated at 702. As shown, the cross-section of the lifting body decreases from the root to the tip. More generally, the fore-aft cross-section of the central section differs in profile from the fore-aft cross-section of the lateral edges. A tip chord 704 and a root chord 706 are further indicated in FIG. 7. The ratio between the tip chord and the root chord may be <0.1, in one example. The lifting body may vary in volumetric distribution and span/sweep, incorporate anhedral or dihedral sections, and be asymmetric in plan, which is desirable when integrating the lifting body into multi-hulled vessels such as catamarans or trimarans, for instance. FIG. 8 shows a plot 800 of a use-case lifting body with twist on the ordinate and span on the abscissa. Twist is expressed in degrees, and although no numerical values are provided for span, the span increases from left to right. It will therefore be understood that the lifting body 600 shown in FIGS. 6A-6D may have the twist and span profile exemplified in FIG. 7. However, other suitable profiles of the lifting body may be used, in other embodiments. The zero value of the span is indicated in the plot along with linear points of interest of both twist and span, although numerical values of the span are not specifically denoted. In one use-case example, the lifting body's twist deviation may be approximately 4° (e.g., from −2° at the root to 2° at the tip), as measured from a horizontal plane. However, numerous twist and span combinations may be used. The lifting body's twist may be selected based on target handling characteristics. It has been found through CFD modeling that if the lifting body has greater lift near the root and less lift near the tips, the lifting body's efficiency may not be sensitive to more granular adjustments to the lifting body's twist distribution. It will be appreciated that FIG. 8 depicts an example of a twist distribution that may result in a bell-shaped lift distribution. However, in alternate examples, other twist distributions may be used to achieve a bell-shaped lift distribution.
FIG. 9 shows a lift distribution plot 900 having a bell shape of an exemplary lifting body. Dynamic lift is on the ordinate and span is on the abscissa. Although no specific numerical values of lift and span are provided, lift and span increase along the corresponding axis. The bell-shaped plot may correspond the lifting body 600, shown in FIGS. 6A-6D. To elaborate, the plot 900 includes a central convex section 902 and lateral concave sections 904. However, lifting bodies with alternate lift distribution curves lie within the scope of the disclosure. As shown, the bell-shaped lift distribution curve tapers near the lateral tip of the span. As previously discussed, the tapered lift distribution allows vortices to be moved inward with a diminished magnitude to increase lifting body efficiency and handling performance.
FIGS. 10A-10D show another example of a lifting body 1000. The lifting body 1000 again includes a central section 1002 and lateral portions 1004. However, the lateral portions are moved rearward in relation to the central section, in comparison to the previously described lifting bodies, as elaborated upon herein.
FIG. 10A shows the lifting body 1000 with joints 1006 formed at mechanical interfaces between the central section 1002 and lateral portions 1004 of the lifting body. The joints 1006 function as geometric transitions that blend or morph the structure of the central section 1002 with the lateral portions 1004. These joints structurally reinforce the lifting body and specifically provide reinforcement to the higher lift lateral portions 1004.
The lateral portions 1004 produce additional dynamic lift during lifting body operation. As such, the lifting body 1000 may achieve greater dynamic lift than the lifting bodies shown in FIGS. 2A-2D and 6A-6D, in one example.
Further, the central section 1002 has a greater volume than the lateral portions 1004. Additionally, the central section 1002 has primarily static lift, in the illustrated example. Further, the central section 1002 has a more forward placement with regard to the lateral portions 1004 than the lifting bodies shown in FIGS. 2A-2D and 6A-6D. In this way, the wave cancellation may be increased, thereby enhancing low speed bulbous bow effect, and reducing bow wave drag at lower speeds.
In the illustrated example, each of the lateral portions 1004 include a control surface 1007 (e.g., a flap) at a straight portion 1008 of a trailing edge 1010. The control surfaces 1007 may be configured to be adjusted in response to control commands to alter the lift generated by the lifting body 1000. As previously indicated, the straight section of the trailing edge allows for integration of the control surface into the lifting body. However, in other examples, the control surfaces may be omitted from the lifting body.
The lateral portions 1004 have a rearward position with regard to the central section 1002. To elaborate, a fore sweep angle 1012 and an aft sweep angle 1014 of the lateral portions 1004 are depicted in FIG. 10B. In one example, the fore sweep angle 1012 may be in the range of 30°-75° and the aft sweep angle may be in the range from may be in the range of −15°-50°. In other examples, the fore sweep angle may be in the range of 45°-75° and the aft sweep angle may be in the range of 0°-45°.
A lateral width 1016 and a fore-aft length 1018 are depicted in FIG. 10B. An aspect ratio defined as the width/length may be less than two, similar to the other lifting bodies described herein. The lifting body may vary in volumetric distribution and span/sweep, incorporate anhedral or dihedral sections, and be asymmetric in plan, which may be desirable when integrating the lifting body into multi-hulled vessels such as catamarans or trimarans, for instance.
FIG. 10B specifically depicts a center of lift 1020 of the lifting body with regard to a fore-aft direction. The center of lift may be in the range of 65-85% from the fore end, in one example. In this way, the lifting body exhibits less pitching moment on the watercraft structure and enhanced alignment with hull structure. Further, the lifting body may require less restoring moment from the aft-balancing device. Consequently, there is less strain on the watercraft's longitudinal structure and more of the watercraft's hull is able to support the wing bending moment. The wing may be formed from the lateral portions of the lifting body.
Further, a chord of the lifting body 1000 again decreases from a center 1022 of the lifting body to each of the lateral edges 1024 of the lifting body.
FIGS. 10C and 10D depict a side view and a front view of the lifting body 1000, respectively, with the central section 1002 and the lateral portions 1004. The joints 1006 of the lifting body 1000 are further depicted in FIGS. 10 and 10D.
The lifting body 1000 shown in FIGS. 10A-10D has more volume placed further forward than the lifting body 102, shown in FIGS. 2A-2D. Further, the lifting body 1000 has a greater amount of wing area that generates dynamic lift than the lifting body 600 shown in FIGS. 6A-6D. Further, the use of the joints 1006 which connect the central section 1002 to the lateral portions 1004 provides greater dynamic lift than the lifting bodies 102 and 600, shown in FIGS. 2A-2D and 6A-6D, respectively. Further, using a higher volume central section with a more forward placement increases wave cancellation. To elaborate, the higher volume central section enhances the hull's lower-speed bulbous bow effect and reduces bow wave drag at lower speeds. Additionally, designing the lifting body 1000 with a higher sweep and aspect ratio allows the lifting body's center of lift to be moved aft (when compared to the lifting bodies shown in FIGS. 2A-2D and 6A-6D), thereby decreasing the pitching moment on the watercraft and enabling better alignment between the lifting body and the hull, if desired. Consequently, the watercraft's longitudinal structure experiences less strain, and more hull structure is able to support the wing bending moment. Even further, the lifting body 1000 achieves a comparatively high lift to drag ratio, which reduces higher speed friction drag by reducing the hull's wetted area from heave and wing downwash. Still further, the lifting body 1000 achieves more efficient dynamic lift via the lateral portions than the center body section. Additionally, the lifting body 1000 exhibits a comparatively high wing sweep angle to mitigate cavitation, enabling higher watercraft speeds, if desired. To elaborate, the lifting body 1000 achieves reduced velocity over the top of the lifting body and increases the cavitation threshold of the lifting body. For instance, the watercraft may have a maximum speed of 35 knots or greater, in one use-case example.
The different lifting bodies described herein, when attached to a bow of a watercraft, generate a bow-up pitch moment at the center of gravity of the watercraft. This bow-up moment may be counteracted by a restoring moment from one of the aft lifting devices described herein. The further aft the center of lift of the lifting body moves, the smaller the bow-up moment for the same lift value. As such, the bow-up moment of the lifting body 1000 shown in FIGS. 10A-10D is less than the bow-up moment of the lifting body 600 shown in FIGS. 6A-6D, and the bow-up moment of the lifting body 600 is greater than the bow-up moment of the lifting body 102, shown in FIGS. 2A-2D.
FIG. 11 shows a watercraft 1100 with the lifting body 1000 coupled to a bow 1102 of the watercraft. To elaborate, a strut 1104 is used to attach the lifting body 1000 to the bow 1102 in the illustrated example. However, in other examples, the lifting body may be directly incorporated into the bow, which may be a bulbous bow, in one particular example. In such an example, the bulbous bow may be used as the center section.
The watercraft 1100 further includes an aft lifting device 1106. The aft lifting device 1106 is positioned rearward of the lifting body 1000, in the illustrated example. The aft lifting device 1106 functions to counteract (e.g., balance) the bow-up moment that is generated by the lifting body 1000. In this way, the moments about the watercraft's center of gravity are effectively managed, thereby enhancing watercraft handling performance.
FIGS. 12A-12D depict yet another example of a lifting body 1200. Specifically, as shown in FIG. 12A the lifting body 1200 again includes a central section 1202 and lateral portions 1204 that are connected to the central section via joints 1206. Further, the lifting body 1200 includes control surfaces 1208 on a trailing edge, similar to the other lifting bodies described herein. Parabolic curves 1210 that define the shape of a leading edge 1212 of the lifting body 1200 are illustrated in FIG. 12A.
FIG. 13 shows a plot 1300 of a use-case lifting body with twist on the ordinate and span on the abscissa. Twist is expressed in degrees, and although no numerical values are provided for span, the span increases from left to right. It will therefore be understood that the lifting body 1200, shown in FIGS. 12A-12D, may have the twist and span profile exemplified in FIG. 13. However, other suitable profiles of the lifting body may be used, in other embodiments. The zero value of the span is indicated in the plot along with linear points of interest of both twist and span. In one use-case example, the lifting body's twist deviation may be approximately 5° (e.g., from −3° at the root to 2° at the tip), as measured from a horizontal plane. However, numerous twist and span combinations may be used. The lifting body's twist may be selected based on target handling characteristics. It has been found through CFD modeling that if the lifting body has greater lift near the root and less lift near the tips, the lifting body's efficiency may not be sensitive to more granular adjustments to the lifting body's twist distribution. It will be appreciated that FIG. 13 depicts an example of a twist distribution that may result in a bell-shaped lift distribution. However, in alternate examples, other twist distributions may be used to achieve a bell-shaped lift distribution. The lifting body may vary in volumetric distribution and span/sweep, incorporate anhedral or dihedral sections, and be asymmetric in plan, which may be desirable when integrating the lifting body into multi-hulled vessels such as catamarans or trimarans, for instance.
FIG. 14 shows a lift distribution plot 1400 of an exemplary lifting body having a bell shape of a lifting body. Dynamic lift is on the ordinate and span is on the abscissa. Although, no specific numerical values of lift and span are provided, lift and span increases along the corresponding axis. The bell-shaped plot may correspond to the lifting body 1200, shown in FIGS. 12A-12D.
FIG. 15 shows an example of a watercraft 1500 with a system 1501 that includes a lifting body 1502 and a hydrofoil 1504, each of which are coupled to a bow 1506. To expound, the lifting body 1502 is coupled to the bow via a strut 1508, and the hydrofoil 1504 is directly coupled to the bow 1506, in the illustrated example. Additionally, the hydrofoil 1504 is coupled to the bow at a location which is vertically higher and aft of the lifting body 1502. In some embodiments, the hydrofoil may be located with its leading edge above the intersection of the lifting body and the stem. However, other configurations are envisioned. Designing a watercraft system with the lifting body 1502 and the hydrofoil 1504 arranged in this manner increases bow wave interference and magnifies the downwash effect, thereby reducing frictional drag due to hull unwetting. Further, the lift is distributed over multiple foil surfaces to provide a sufficient structure for larger watercrafts (e.g., watercrafts >50 meters (m) in length), for instance, without designing the lifting body with an undesirable span and lift. In the illustrated example, the watercraft system 1501 includes extensions 1510 that join lateral tips 1512 of the lifting body 1502 and the hydrofoil 1504. In this way, the system is strengthened. Further, in the example illustrated in FIG. 15, an aft-balancing lift device 1514 is coupled to a stern 1516 of a hull 1518. In some embodiments, the hydrofoils may incorporate anhedral or dihedral sections. For example, hydrofoils may have an anhedral angle at the root section to match the deadrise of the bow where connected, such that the foils attach to the bow plate at 90°. This anhedral root section may deepen hydrofoil immersion. However, other attachment angles and configurations are also envisioned. In some embodiments, the hydrofoils may also be configured as canards.
FIGS. 16-17 show another example of a watercraft system 1600 with a lifting body 1602 and a hydrofoil 1604. The lifting body 1602 is coupled to a bow 1606 of a watercraft 1608 via a strut 1610, and the hydrofoil 1604 is directly coupled to the bow. Again, the hydrofoil 1604 is positioned rearward and vertically above of the lifting body 1602. However, in the watercraft system 1600 shown in FIGS. 16-17, the extensions which join the tips of the lifting body and the hydrofoil are omitted from the watercraft system 1600. Further, both the lifting body 1602 and the hydrofoil 1604 include flaps 1700 in the example illustrated in FIG. 17. However, in other examples, the flaps may be omitted from the lifting body and/or the hydrofoil. Using staggered hydrofoils allows the lift to be effectively distributed along the hull without demanding an excessively large span for the lifting body, which may be particularly useful for larger watercrafts. Further, the aft-balancing lift device magnifies the watercraft's downwash effect, thereby reducing the watercraft's frictional drag due to hull unwetting.
It will be appreciated, that the watercraft system 1600 and/or the other watercraft systems described herein may include additional hydrofoils which may be positioned vertically above and rearward of the hydrofoil 1604. Another hydrofoil 1605, rearward (in a fore-aft direction) of the hydrofoil 1604, is coupled to a hull 1607 in FIG. 16. However, the rearward hydrofoil 1605 may be omitted from the watercraft, in alternate embodiments.
The added mass from the strut 1610 and the hydrofoil 1604 counters undesirable ship motions (e.g., pitch, roll, and/or yaw) and results in a more stable and efficient propulsion thrust line. This reduces the thrust loss component, which is termed added resistance in a seaway. Watercraft motion control can be enhanced by employing a motion stabilizing system incorporating the controllable trailing edge flaps 1700, shown in FIG. 17. Additionally, in some examples, an aft-balancing lift device 1612, shown in FIG. 16, may have a control flap incorporated thereto to provide even greater watercraft control for countering undesirable motion during operation.
FIG. 18 shows a watercraft 1800 with a bulbous bow 1802. Any of the lifting bodies described herein may be coupled to or integrated with the bulbous bow 1802 in one example or used instead of the bulbous bow as shown in the watercraft 1900 depicted in FIG. 19. Using a lifting body in conjunction with the bulbous bow provides dynamic lift to the watercraft. Further, using the bulbous bow in conjunction with the lifting body provides added structural reinforcement to the lifting body to manage the relatively high expected slamming loads.
The watercraft lifting body technology described herein allows an increase in watercraft full load operating displacement from 20%-35%, in one specific use-case example, across a wide speed range. In general terms, at critical low speeds (e.g., Fr<0.6), the higher allowable displacement is due to the mitigation of bow wave making. At higher speeds, the lifting body and aft-balancing lift from devices such as interceptors, transom flaps, transom foils, bilge foils, or a combination thereof, generate dynamic lift between 20%-35% of the vessel's full load displacement, in certain use-case examples, causing the vessel to heave to a shallower operating draft, thereby reducing hull immersion. Having less hull immersed mitigates both friction and pressure drag and also reduces wake generation. The strong downwash at the bow generated by the lifting body causes the hull forebody (e.g., especially from the critical hull shoulder and aft therefrom) to be unwetted, thereby reducing pressure and friction drag. The downwash also suppresses spray formation, thereby further reducing drag therefrom. Furthermore, the downwash cancels wave energy/generation to reduce ship resistance. The lifting bodies described herein also achieve a bulbous bow effect due to the added volume/displacement positioned forward of the bow, which provides destructive wave cancellation. Further, the added mass from the lifting body strut and foil structure counters undesirable ship motions (e.g., pitch, roll, and/or yaw) that results in a more stable and efficient propulsion thrust line. This reduces the thrust loss component, which is termed added resistance in a seaway. Watercraft motion control can be enhanced by employing a motion stabilizing system incorporating controllable trailing edge flaps on the lifting body and also employing active control surfaces on the aft-balancing lift devices, if desired.
An axis system with an x-axis, y-axis, and z-axis is provided in FIGS. 1-19 for spatial reference, when appropriate. In one example, the z-axis may be vertically aligned (e.g., parallel to gravitational axis), the x-axis may be longitudinally aligned, and the y-axis may be laterally aligned. However, other orientations of the axes are possible.
FIGS. 1-19 are drawn approximately to scale (aside from the schematically depicted components), although other relative component dimensions may be used, in other embodiments. Further, FIGS. 1-19 show the relative positioning of the various components of the watercraft system. If shown directly contacting each other, or directly coupled, then such elements may be referred to as directly contacting or directly coupled, respectively, at least in one example. Similarly, elements shown contiguous or adjacent to one another may be contiguous or adjacent to each other, respectively, at least in one example. As an example, components laying in face-sharing contact with each other may be referred to as in face-sharing contact. As another example, elements positioned apart from each other with only a space there-between and no other components may be referred to as such, in at least one example. As yet another example, elements shown above/below one another, at opposite sides to one another, or to the left/right of one another may be referred to as such, relative to one another. Further, as shown in the figures, a topmost element or point of element may be referred to as a “top” of the component and a bottommost element or point of the element may be referred to as a “bottom” of the component, in at least one example. As used herein, top/bottom, upper/lower, above/below, may be relative to a vertical axis of the figures and used to describe positioning of elements of the figures relative to one another. As such, elements shown above other elements are positioned vertically above the other elements, in one example. As yet another example, shapes of the elements depicted within the figures may be referred to as having those shapes (e.g., such as being circular, straight, planar, curved, rounded, chamfered, angled, or the like). Further, elements shown intersecting one another may be referred to as intersecting elements or intersecting one another, in at least one example. Further still, an element shown within another element or shown outside of another element may be referred as such, in one example. Elements offset or opposite from one another may be referred to as such, in one example. Unless otherwise indicated, the terms “approximately” and “substantially” may be construed to mean plus or minus five percent or less from a value or range.
In the following paragraphs, the subject matter of the present disclosure is further described. In one aspect, a watercraft system is provided that comprises a lifting body configured to generate dynamic lift during watercraft operation; wherein the lifting body includes: two opposing lateral portions that extend laterally outward and aft from a central section; and wherein the two opposing lateral portions generate a greater amount of dynamic lift than the central section. In one example, the central section may have a fore-aft cross-section that differs in profile from a fore-aft cross-section of the two opposing lateral portions. In another example, joints may be formed at mechanical interfaces between the central section and the two opposing lateral portions and function as transition regions. In yet another example, the lifting body may be coupled to a bow of a hull. In another example, the central section may be incorporated into the hull as a bulbous bow. In yet another example, the watercraft system may further comprise an aft lifting device positioned aft of the lifting body. In another example, the watercraft system may further comprise a strut that attaches the lifting body to the hull. In another example, the opposing lateral portions may be positioned aft of the central section. In another example, the central section may be laterally narrower than each of the two opposing lateral portions. In yet another example, a chord of the lifting body may decrease from a center of the lifting body to each of the lateral edges; and the lifting body may twist from the center to each of the lateral edges.
In another aspect, a watercraft system is provided that comprises a lifting body coupled to a watercraft hull and configured to generate dynamic lift during watercraft operation; and a first hydrofoil coupled to the watercraft hull and positioned behind the lifting body in a fore-aft direction; wherein the first hydrofoil has a higher vertical location on the watercraft hull in comparison to the lifting body. In another example, the lifting body and/or the first hydrofoil may twist from a center to each lateral edge of the lifting body and/or the first hydrofoil. In yet another example, the lifting body and the first hydrofoil may include lateral tips that are coupled via fore-aft extensions. In yet another example, the lifting body may be incorporated into a bulbous bow. In another example, the watercraft system may further comprise at least one control surface positioned at a trailing edge of the lifting body and/or the first hydrofoil, wherein the control surface is configured to be adjusted in response to control commands to alter the lift generated by the lifting body and/or the first hydrofoil. In another example, the watercraft system may further comprise a second hydrofoil, wherein the first hydrofoil and the second hydrofoil are positioned on opposing lateral sides of the watercraft hull. In another example, the first hydrofoil and the second hydrofoil may have anhedral root sections. In yet another example, the lifting body may include: two opposing lateral portions that extend laterally outward and aft from a central section; and the two opposing lateral portions generate a greater amount of dynamic lift than the central section. In another example, the watercraft system may further comprise an aft-balancing lift device coupled to a hull of the watercraft and configured to balance lift that is generated by the lifting body and the first hydrofoil. In yet another example, the lifting body may be coupled to a bow of a hull.
It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to jet boats, propeller boats, and other types of watercrafts which use a variety of propulsion systems. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.
The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.
Patent Application
20250010947
