The application is the US national phase of International application No. PCT/CN2018/113737, titled “SPOILING APPARATUS FOR TRIGGERING TURBULENT TRANSITION BY AUTONOMOUS DISTURBANCE AND SPOILERS” filed on Nov. 2, 2018, which claims the priority to Chinese Patent Application No. 201811007947.X, titled “SPOILING APPARATUS FOR TRIGGERING TURBULENT TRANSITION BY AUTONOMOUS DISTURBANCE AND SPOILERS”, filed on Aug. 31, 2018, with the China National Intellectual Property Administration, both of which are incorporated herein by reference in their entirety.
The present disclosure relates to a spoiler apparatus for triggering turbulence transition to by autonomous disturbance, and a spoiler thereof, which pertains to the technical field of vehicle resistance control.
A vehicle needs to overcome resistance when navigating in the air and underwater. The resistance against the vehicle mainly includes frictional resistance on a surface of the vehicle and pressure drag. For a vehicle at a low speed, the pressure drag accounts for most of the resistance, and is mainly caused by a flow of a vortex shedding at bottom of the vehicle. Due to the shedding vortex, pressure at the bottom of the vehicle cannot rise back to an ambient pressure, resulting in a large pressure drag. Moreover, the vehicle is subject to unnecessary vibration forces due to periodic large-scale fluctuation of the pressure at the bottom of the vehicle.
In order to reduce the pressure drag, it is required to effectively eliminate the vortex shedding at the bottom of the vehicle. The main cause of the vortex shedding at the bottom of the vehicle is that surface layer energy of the flow is too low to resist strong adverse pressure gradient caused by a deflection of the flow at the bottom, thereby resulting in a local flow separation and generating a vortex flow. Therefore, the solution for eliminating the vortex shedding at the bottom to reduce the pressure drag is to improve, upstream of the bottom, a flow of a surface layer on the surface of the vehicle to trigger a flow state transition from laminar to turbulent, thereby enhancing the energy of the flow at the surface layer and avoiding the vortex shedding generated at the bottom.
However, additional resistance is usually generated in triggering the flow state transition from laminar to turbulent. Therefore, the problem to be solved in engineering design is to find a solution with which the transition from laminar to turbulent can be effectively triggered without generating additional resistance, the surface layer energy can be increased and the vortex shedding at the bottom can be eliminated, thereby reducing the resistance against the vehicle.
An object of the present disclosure is to reduce the resistance against the vehicle and improve overall performance by providing a spoiler apparatus for triggering turbulence transition by autonomous disturbance, and a spoiler, which can generate a large circumferential disturbance with small structural changes and effectively trigger turbulence transition.
The object of the present disclosure is achieved by the following technical solutions.
A spoiler apparatus for triggering turbulence transition by autonomous disturbance is provided, which includes a groove, a spoiler, and an elastic member,
where the groove is provided upstream of a bottom surface of a vehicle,
the spoiler is provided in the groove, one end of the spoiler is fixed in the groove via a swing shaft, and another end of the spoiler is connected to a bottom of the groove via the elastic member and is rotatable about the swing shaft, and
an outward pushing force on the spoiler generated by the elastic member in a maximally compressed state is balanced with a pressure in a critical state of flow.
Preferably, the spoiler is configured as a flow-guiding plane structure having a continuously increasing curvature, where an upstream portion of the spoiler is parallel to a flow incoming direction, and a downstream portion of the spoiler is parallel to a circumferential direction.
Preferably, an inner side surface curve, an outer side surface curve, or a center curve of the spoiler is determined by:
Preferably, a limiting structure is provided at one end of the spoiler to limit a maximum opening angle and a minimum compressed height of the spoiler.
Preferably, multiple dovetail grooves are provided in parallel to each other on a surface of the spoiler.
Preferably, a centerline of each of the multiple dovetail grooves is determined by:
(4) calculating coordinates (X, Y) of an inner side surface curve, an outer side surface curve, or a center curve as follows:
X=x·X1
Y=y·Y1.
Preferably, an opening width of each of the multiple dovetail grooves is not less than 2 mm, an opening angle of each of the multiple dovetail grooves ranges from 60 to 90 degrees, and an opening depth of each of the multiple dovetail grooves is 0.5 to 1.0 times the opening width.
Preferably, multiple protrusions are provided on the surface of the spoiler at equal distance along the flow incoming direction, where two ends of each of the multiple protrusions are larger than the middle of the protrusion, widths of the two ends are 0.1 to 0.2 times an inter-protrusion distance, two side surfaces of each of the multiple protrusions each have a shape of circular arc having a central angle ranging from 30 to 60 degrees, and the inter-protrusion distance is 0.5 to 2.0 times a width of the spoiler.
Preferably, an outer surface of each of the multiple protrusions has a shape of circular arc, and a central angle of the circular arc ranges from 60 to 90 degrees.
Preferably, multiple randomly-sized side-edge saw teeth are formed on an inner side surface of the spoiler.
Preferably, 5 to 50 grooves are evenly provided on the vehicle in the circumferential direction.
Preferably, the spoiler covers no more than half of a circumferential length of the vehicle.
A spoiler is further provided, which is configured as a flow-guiding plane structure having a continuously increasing curvature, where an upstream portion of the spoiler is parallel to a flow incoming direction, and a downstream portion of the spoiler is parallel to a circumferential direction.
Preferably, an inner side surface curve, an outer side surface curve, or a center curve of the spoiler is determined by:
Preferably, a limiting structure is provided at one end of the spoiler to limit a maximum opening angle and a minimum compressed height of the spoiler.
Preferably, multiple dovetail grooves are provided in parallel to each other on a surface of the spoiler.
Preferably, an outline curve of each of the multiple dovetail grooves is determined by:
Preferably, an opening width of each of the multiple dovetail grooves is not less than 2 mm, an opening angle of each of the multiple dovetail grooves ranges from 60 to 90 degrees, and an opening depth of each of the multiple dovetail grooves is 0.5 to 1.0 times the opening width.
Preferably, multiple protrusions are provided on the surface of the spoiler at equal distance along the flow incoming direction, where two ends of each of the multiple protrusions are larger than the middle of the protrusion, widths of the two ends are 0.1 to 0.2 times an inter-protrusion distance, two side surfaces of each of the multiple protrusions each have a shape of circular arc having a central angle ranging from 30 to 60 degrees, and the inter-protrusion distance is 0.5 to 2.0 times a width of the spoiler.
Preferably, an outer surface of each of the multiple protrusions has a shape of circular arc, and a central angle of the circular arc ranges from 60 to 90 degrees.
Preferably, multiple randomly-sized side-edge saw teeth are formed on an inner side surface of the spoiler.
Compared with the conventional technology, the present disclosure has the following advantages.
In order to reduce resistance against a vehicle, turbulence transition is triggered upstream of a bottom of the vehicle to increase flow energy of a surface layer and eliminate vortex shedding at the bottom, thereby reducing the resistance at the bottom. Moreover, it is required to effectively trigger the transition to turbulence with little additional resistance. Therefore, it is proposed to install a spoiler which can be automatically sprung out upstream of the bottom. By using predetermined compression force of a spring, the spoiler can be automatically sprung out from a groove in a case that flow speed is low, and then the spoiler disturbs the flow to trigger a flow state transition from laminar to turbulent. In order to achieve a large disturbance with little additional resistance, a shape of the spoiler is configured as a high-order smooth curve, guiding the flow from an axial direction to a circumferential direction to generate circumferential disturbance, thereby triggering the transition more effectively. Furthermore, dovetail grooves are provided on the surface of the spoiler to reduce flow resistance against the spoiler. Alternatively, randomly distributed saw teeth are provided on a side edge of the spoiler, or waistdrum-shaped protrusions are provided on the surface of the spoiler, thereby realizing the disturbance of the flow with little additional resistance.
Referring to
The spoiler 3 is a sheet-like structure having a constant width and a continuously increasing curvature, which is sickle-shaped. A head portion of the spoiler 3 is parallel to a flow incoming direction, and a tail portion of the spoiler 3 is parallel to the circumferential direction, thereby guiding an incoming flow to the circumferential direction. A width of the spoiler 1% to 10% of a circumference of the vehicle, and the spoiler covers no more than half of the circumference of the vehicle.
In order to reduce resistance in guiding the flow to the circumferential direction, a high-order continuous curve is required for an outline of the spoiler. In an embodiment, an outline curve (an inner side surface curve, an outer side surface curve, or a center curve) of the spoiler is configured as a high-order continuous curve. A dimensionless equation of the higher-order continuous curve is given as follows:
y=xn(1−x)(1+n−nx)+x (1)
In equation (1), a typical value of n is 0.5, and a recommended range of n is 0.3 to 0.7. x ranges from 0 to 1. After obtaining y, based on a horizontal length X0 and a vertical height Y0 of each curve according to the design requirement, coordinates X and Y of an actual curve are obtained by using equations (2) and (3), as shown in
X=x·X0 (2)
Y=y·Y0 (3)
A spoiler structure is provided on the surface of the spoiler. In one embodiment, multiple dovetail grooves 3-3 may be provided in parallel to each other on the surface of the spoiler to form the spoiler structure as shown in
The outline curve of the spoiler is configured as a high-order continuous curve. An outline curve of the dovetail groove is obtained based on the same curve equations (1), (2), and (3) and a same calculation algorithm as the outline curve of the spoiler.
An opening width h1 of the dovetail groove is usually not less than 2 mm, an opening angle β of the dovetail groove ranges from 60 to 90 degrees, and an opening depth d1 of the dovetail groove is 0.5 to 1.0 times the opening width.
In a case that a flow velocity of a fluid and a density of the fluid are high, a force exerted by the fluid is greater than a restoring force of the compressive spring 4, thereby restricting the spoiler 3 within the groove 2. In this case, the spoiler 3 is closed within the groove 2, the flow is in a turbulent state, and it is not required to spring up the spoiler 3. A lower limiting side surface 3-2 of the spoiler prevents the spoiler from being pressed too low by the flow.
In a case that the flow velocity of the fluid and the density of the fluid are low, pressure of the fluid on the spoiler 3 is reduced. If the force exerted by the fluid is less than an elastic force of the compressive spring 4, the compressive spring 4 springs the spoiler 3 out from the groove. An upper limiting side surface 3-1 of the spoiler 3 prevents the spoiler from being sprung too much, ensuring that an opening angle of the spoiler is not larger than a maximum opening angle α. The upper limiting side surface 3-1 is provided with a protruding limiting portion, to prevent the spoiler from rotating beyond a set angle.
When the compressive spring 4 is compressed to an uttermost bottom, the elastic force generated by the compressive spring 4 is balanced with a pressure in a critical state of flow.
The critical state of flow is defined as follows. Reynolds number being 1E5 (the vehicle is navigating in water) or 1E6 (the vehicle is navigating in the air) is the critical state for transition to turbulence. If the Reynolds number is greater than the critical state Reynolds number, transition to turbulence will occur autonomously. If the Reynolds number is less than the critical state Reynolds number and the flow is not subjected to external disturbance, the transition to turbulence will not occur. If the Reynolds number is less than the critical state Reynolds number, a pressure of the flow is less than the elastic force of the compressive spring, the spoiler is sprung out by the compressive spring, disturbing the flow and triggering the transition to turbulence. If the Reynolds number is greater than the critical state Reynolds number, the pressure of the flow is greater than the elastic force of the compressive spring, the spoiler is kept within the groove, and the transition to turbulence occurs autonomously.
After being sprung, the spoiler protrudes from a surface layer of the flow. Due to the fact that the spoiler has a sickle-shaped outline and multiple parallel dovetail grooves are arranged on the surface of the spoiler, the spoiler disturbs the flow to generate a small vortex flow, part of the axial flow in the surface layer is guided to a circumferential direction to more effectively disturb the flow, trigger turbulence at the bottom of the vehicle and reduce the vortex shedding at the bottom of the vehicle, thereby reducing the resistance at the bottom. In an embodiment, side-edge saw teeth are formed on an inner side surface of the spoiler as shown in
In another embodiment, waistdrum-shaped protrusions 6 may be formed on the upper surface of the spoiler as shown in
An inter-protrusion distance d3 between the waistdrum-shaped protrusions 6 (distance between centerlines of two protrusions) is 0.5 to 2.0 times the width of the spoiler. The waistdrum-shaped protrusions 6 are have a larger size at two ends and a smaller size in the middle. An outer contour curve of the waistdrum-shaped protrusion has a shape of circular arc, a width d4 of the waistdrum-shaped protrusion is equal to the width of the spoiler and a central angle θ ranges from 30 to 60 degrees.
Referring to
Side-edge saw teeth on the spoiler can be used in combination with the waistdrum-shaped protrusions on the upper surface of the spoiler or with the dovetail grooves on the upper surface of the spoiler. The side-edge saw teeth are formed on the side surface of the spoiler, and the waistdrum-shaped protrusions are formed on the upper surface of the spoiler. Or, the side-edge saw teeth are formed on the side surface of the spoiler, and the dovetail grooves are formed on the upper surface of the spoiler.
The apparatus is applied in the vehicle to autonomously trigger the transition to turbulence, thereby reducing the resistance at the bottom, and providing a basis for reduction of resistance by the vehicle autonomously.
The above described are only some preferred embodiments of the present invention and the protection scope of the present disclosure is not limited to the above embodiments. Any modifications or replacements that can be easily conceived by those skilled in the art within the technical scope of the present disclosure should fall within the protection scope of the present disclosure.
Content in the present disclosure not described in detail belongs to common practice of those skilled in the art.
Number | Date | Country | Kind |
---|---|---|---|
201811007947.X | Aug 2018 | CN | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/CN2018/113737 | 11/2/2018 | WO |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2020/042351 | 3/5/2020 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
20020160669 | Spade | Oct 2002 | A1 |
20100266382 | Campe et al. | Oct 2010 | A1 |
Number | Date | Country |
---|---|---|
102501942 | Jun 2012 | CN |
102758728 | Oct 2012 | CN |
103204186 | Jul 2013 | CN |
104260823 | Jan 2015 | CN |
106542046 | Mar 2017 | CN |
107600354 | Jan 2018 | CN |
5669114 | Feb 2015 | JP |
Entry |
---|
Abbena et al., “Modern Differential Geometry of Curves and Surfaces with Mathematica”, 2017, CRC Press, pp. 53-59 (Year: 2017). |
International Search Report (English and Chinese) and Written Opinion (Chinese) of the International Searching Authority issued in PCT/CN2018/113737, mailed Apr. 28, 2019; ISA/CN. |
Number | Date | Country | |
---|---|---|---|
20210294285 A1 | Sep 2021 | US |