WO2018041890A1

WO2018041890A1 - Apparatus and method for reducing soiling on a vehicle

Info

Publication number: WO2018041890A1
Application number: PCT/EP2017/071755
Authority: WO
Inventors: Matthew OSBORNE; Ross Turner; Rob Lawrence; Lara SCHEMBRI PUGLISEVICH
Original assignee: Jaguar Land Rover Limited
Priority date: 2016-09-05
Filing date: 2017-08-30
Publication date: 2018-03-08
Also published as: DE112017004445T5; GB2553359A; GB2553359B; GB201615033D0

Abstract

Embodiments of the present invention provide a vehicle comprising a spoiler and a method for reducing soiling on the rear of the vehicle. The spoiler comprises a channel to direct airflow from the top of the vehicle to underneath the spoiler. The directed airflow forms a vortex which rotates down the rear surface of the vehicle, then upwards towards the spoiler. The rotation of the vortex may further reduce soiling of the rear of the vehicle.

Description

Apparatus and Method for Reducing Soiling on a Vehicle

TECHNICAL FIELD

Aspects of the invention relate to a vehicle, to a use of a spoiler, and to a method of reducing soiling on a vehicle.

BACKGROUND

Vehicles driving in wet or dirty conditions are often subject to soiling, particularly on the rear portion of the vehicle. This is because dirt or water is sprayed from vehicle tyres or picked up in the airflow moving around the vehicle. Some dirt particles, particularly smaller dirt particles or water spray can become entrained into the airflow behind the vehicle as it moves forwards. The dirt or spray is then circulated in a wake behind the vehicle where it can be deposited onto the rear of the vehicle. It will also be appreciated that dirt or spray may be deposited on other surfaces of the vehicle.

One way to mitigate against soiling is to provide mud flaps which cover a portion of the wheel to reduce the water or dirt that is thrown directly from the tyres, or thrown up from the ground when the tyres pass through standing water. This however, has little or no effect on the spray or dirt particles that become entrained into the wake.

Another way to mitigate against soiling is to shape the body of the vehicle to minimise the size of wake left behind the vehicle. This approach however is often not possible or ineffective owing to other design constraints on body shape, in particular, for sports utility vehicles (SUVs) or similar vehicle body types, which inherently have a high incidence of soiling. Furthermore, again owing to design constraints, the reduction of the wake size achievable by this approach is often small.

It is an object of embodiments of the invention to at least mitigate one or more of the problems of the prior art. SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a vehicle, a use of a spoiler and a method for reducing soiling on the rear of a vehicle as claimed in the appended claims.

According to an aspect of the invention, there is provided a spoiler comprising: a channel to direct airflow from above the top of the vehicle to below the spoiler when the vehicle is in motion to reduce soiling on the rear surface.

According to an aspect of the invention, there is provided a vehicle with a rake angle between 30 to 60° to the vertical; the vehicle comprising a spoiler which extends in the horizontal direction by at least 200 mm when from the rear surface, the spoiler comprising: a channel to direct airflow from above the top of the vehicle to below the spoiler when the vehicle is in motion, so that airflow exiting the channel forms a vortex where the airflow moves downward approximately parallel to the rear surface of the vehicle and is then circulated upwards towards the rearmost edge of the spoiler, to reduce soiling on the rear surface. By redirecting air to form a vortex that circulates downward over the rear surface, and outwards, towards the rear of the spoiler (i.e. counter-clockwise when viewed from the left side of the vehicle), the spoiler can reduce soiling by redirecting clean air from the top of the vehicle into the region rearward of the rear surface, therefore reducing airflow from the sides, and in particular, below the vehicle which would otherwise carry dirt onto the rear surface of the vehicle. The circulation of the airflow in the vortex as described provides improved reduction of soiling in comparison to other flow patterns below the spoiler.

The vortex may also reduce drag by increasing airflow in the region immediately rearward of the spoiler. This reduces the amount of airflow from over the top of the spoiler that would otherwise stagnate behind the spoiler and thus may reduce the pressure drag.

Thus, as explained above, a spoiler that forms a vortex as described herein can provide improved suppression of soiling on the rear surface of a vehicle. Use of a spoiler to form the vortex as described herein may also improve drag. In an aspect, there is a method comprising providing a spoiler to a vehicle, the spoiler having a channel; and wherein when the vehicle is in motion, the spoiler directs airflow from the top of the vehicle to below the spoiler through the channel, to form a vortex where airflow is directed downwards, approximately parallel to the rear surface of the vehicle, and circulated up towards the rear face of the spoiler.

In an aspect, there is the use of a spoiler as defined herein to reduce soiling on a rear surface of a vehicle. In an aspect, there is a vehicle comprising: a first spoiler comprising a channel to direct airflow from above the top of the vehicle to below the first spoiler to reduce soiling on the rear surface; and a second spoiler attached to an attachment point on the underbody of the vehicle, the second spoiler protruding downward from the underbody, to alter the airflow transmitted along the centre of the vehicle underbody when the vehicle is in motion, to suppress the airflow that exits from the rear of the vehicle underbody from forming a vortex proximal to the rear surface of the vehicle, to reduce soiling on the rear of the vehicle by dirt suspended in the airflow, compared to soiling for the vehicle without the second spoiler. In embodiments, the first spoiler redirects airflow through the channel when the vehicle is in motion, so that airflow exiting the channel forms a vortex where the airflow moves downwards parallel to the rear surface of the vehicle and is circulated upward towards the rearmost edge of the first spoiler, to reduce soiling on the rear surface.

In embodiments the second spoiler may be any spoiler as described in UK application number 1615019.5, the content of which is herein incorporated by reference. In an aspect, there is a method of reducing soiling comprising: using a first spoiler on a vehicle to direct airflow from the top of a vehicle to below the spoiler so that the redirected airflow channel forms a vortex where the airflow moves downward parallel to the rear surface of the vehicle and is circulated upward towards the rearmost edge of the first spoiler; and also altering the airflow transmitted along the centre of the vehicle underbody, to cause a reduction of soiling on the rear of the vehicle by dirt carried in the airflow. Redirecting the airflow over the top of the vehicle and altering the airflow under the vehicle underbody provide a combined effect on the suppression of soiling that is significantly greater than expected. In embodiments, a second spoiler (a vehicle underbody spoiler) may be deployed to the vehicle underbody to protrude downward from the vehicle underbody, to alter the airflow transmitted along the centre of the vehicle underbody.

In embodiments, the second spoiler alters the airflow transmitted along the centre of the vehicle underbody so that airflow exiting from the rear of the vehicle underbody is supressed from forming a vortex proximal to the rear surface of the vehicle, to reduce soiling on the rear of the vehicle by dirt suspended in the airflow, compared to soiling for the vehicle without the spoiler. In embodiments, the channel is at an angle of between ± 10° to the rake angle of the rear surface of the vehicle. This may provide optimum angles for establishing the vortex.

In embodiments, the at least one channel has a length of at least 10 mm. This may provide optimum channel length for establishing the vortex, if the channel length is too short, the airflow passing through it may be diffused as it emerges from the channel. In embodiments, the channel has a length between 20 and 80 mm, or between 30 and 60 mm. In embodiments, the at least one channel comprises forward and rearward facing faces with a spacing of at least 10 mm there-between. This may provide a channel with a spacing for establishing an optimum vortex, by ensuring an optimum amount of air is redirected. In embodiments, the at least one channel comprises a forward facing face having an upper edge and a rearward facing face having an upper edge which is between 10 mm and 20 mm lower than the upper edge of the forward facing face. In embodiments, the upper edge of the rearward face may be between 0 and 20 mm lower that the upper edge of the forward facing face, or between 5 and 15 mm lower.

In embodiments, the lowermost edge of the forward facing face and/or the rearward facing face of the channel comprise sharp edges with radii less than 20 mm. The uses of sharp edges in these positions induce a clean separation of flow and therefore provide optimum conditions for establishing a vortex. Advantageously, the sharp edges promote the generation of a jet of air by inducing a clean separation of flow thus stopping the airflow from diffusing.

In embodiments, the spacing between the forward facing face and the rearward facing face is between 10 and 30 mm, measured at the narrowest point of the channel. In embodiments, the forward facing face and rearward facing face of the channel are at an angle between ±20° relative to each other.

In embodiments, the at least one channel extends between 50 and 95 % of the total width of the spoiler, where width is the dimension perpendicular and horizontal to the direction of travel of the vehicle.

In embodiments, the spoiler redirects between 10 and 30 percent of the airflow within five times the size of the width of the channel exit from above the top of the vehicle when the vehicle is travelling between 30 and 180 km/h, so that it passes through the spoiler channel.

In embodiments, the mean velocity of the airflow through the channel is from 30% to 80% of the freestream velocity when the vehicle is travelling between 30 kph and 180 kph.

In embodiments, the flow rate through the channel is from 0.1 to 0.5 m³/s when the vehicle is travelling between 30 to 100 km/h.

In embodiments, the air exits the channel with a velocity of between 6 and 20 m/s when the vehicle is travelling between 50 to 100 km/h.

In embodiments, the spoiler redirects between 10 and 30 percent of the airflow within a layer from the top of the vehicle, the height of which is five times the size of the width of the channel exit. The spoiler redirects between 10 and 30 percent of the airflow within the layer when the vehicle is travelling between 30 and 180 km/h, and wherein the redirected airflow is redirected through the channel. In embodiments, a portion of the vehicle may extend beyond the rear surface of the vehicle in the rearward direction. The spoiler may extend at least 200 mm when measured from a plane formed by the rear surface to the rearmost portion of the spoiler, inclusive of the portion of the vehicle that extends beyond the rear surface in the rearward direction.

In embodiments, the airflow exiting the channel is a free rectangular jet. This is advantageous as the free rectangular jet helps to maintain the centreline momentum of the airflow leaving the channel which reduces the likelihood of the airflow attaching to the rear surface of the vehicle. The detached airflow may be circulated upwardly towards the spoiler, due to the rake angle of the vehicle, which promotes the generation of a vortex.

In embodiments, the second spoiler is adapted so that when it is deployed on a vehicle underbody, the spoiler body protrudes from the underbody of the vehicle between 10 and 60 mm.

In embodiments, the body of the second spoiler comprises a planar member. In embodiments, the second spoiler is adapted so that when it is deployed on a vehicle underbody, a planar surface of the spoiler is orientated perpendicular to the direction of travel of the vehicle.

In embodiments, the second spoiler is formed from a flexible material with sufficient stiffness to resist airflow and be deformable to ground contact.

In embodiments, the second spoiler comprises attachment means adapted to releasably or movably attach the spoiler to the underbody of the vehicle. In embodiments, the second spoiler is attached to an attachment point on the underbody of the vehicle so that the spoiler can be deployed rearward of the rear axle of the vehicle.

In embodiments, the second spoiler is attached to an attachment point on the underbody of the vehicle so that the second spoiler can be deployed to protrude beyond the ground line of the vehicle, wherein the ground line is a line or plane parallel to the road surface and coincident with the lowest rigid component of the underbody.

In embodiments, the second spoiler is attached to an attachment point on the underbody of the vehicle so that the second spoiler can be deployed to protrude beyond the departure line of the vehicle, wherein the departure line is a line or plane from the points in which the rear tyres contact the road to the rearmost portion of the vehicle. In embodiments, the attachment point is on a battery box of the underbody of a vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described by way of example only, with reference to the accompanying figures, in which:

Figure 1 shows a cross section of an embodiment of the invention; Figure 2 shows an alternative view of an embodiment of the invention;

Figure 3 shows a plan view of an embodiment of the invention;

Figure 4 shows a side view of an embodiment of the invention;

Figure 5 shows a side view of an aspect of an embodiment of the invention;

Figure 6 shows a side view of an aspect of an embodiment of the invention; and Figure 7 shows sections from a computational fluid dynamics model of a vehicle not of the invention and of an embodiment of the invention. Image A, is of a vehicle with no spoiler attached; image B is of the same vehicle with a spoiler of the invention.

DETAILED DESCRIPTION As used herein, the term "vehicle" may refer to any land vehicle. A vehicle may include amongst others, any automobile, for example, cars, vans, lorries or other goods vehicles. As used herein, the term "top of the vehicle" refers to the uppermost surfaces of the vehicle. Which, for example, in the case of many vehicle types may include the roof of the vehicle.

As used herein, the term "airflow" refers to the movement of air relative to the vehicle. References herein to direction or movement of airflow may generally refer to the average or bulk movement airflow in a region and may not necessarily be limited to individual streamlines

As used herein, the term "vertical" may refer to the vertical axis of the vehicle, i.e. the axis common with the height of vehicle, i.e. height of vehicle when on horizontal surface.

As used herein, the term "boundary layer" refers to a layer of stationary or slow moving air relative to the velocity of the main airflow uninfluenced by viscosity in the vicinity of a solid surface.

As used herein, "rear" refers to the tail end of the vehicle, which is the end facing the rearward direction. As used herein, the term "rear surface" refers to the surfaces of the body of the vehicle at the rear of the vehicle which are facing the rearward direction. In particular, this term may refer to the upper rear surface or panel under the first spoiler, for example, a rear windscreen. As used herein "rear of the vehicle" may include all of the surfaces facing the rearward direction of the vehicle, including the rear surface. As used herein, the term "rearward" refers to the direction opposite to the normal forward direction of travel of the vehicle, i.e. away from the rear surface of the vehicle. The converse applies for "front", "front surfaces" and "forward".

As used herein, the term "spoiler" includes any apparatus on an external surface of a vehicle to alter or 'spoil' the airflow near to the spoiler. The spoiler may alter airflow by providing an obstacle that causes the airflow to change path.

As used herein, the term "underbody" refers to the surface beneath the vehicle facing the road. A vehicle underbody may comprise an irregular surface formed from exposed components of the vehicle, or may comprise a panel, covering the underbody components of the vehicle.

As used herein, the term "motion" refers to the forward direction of the vehicle. Motion may also specifically refer to the condition where the forward direction is greater than 20 km/h or 30 km/h or 40 km/h or 50 km/h or 60 km/h or 70 km/h or 80 km/h or 90 km/h or 100 km/h or 1 10 km/h or 120 km/h.

As used herein, the term "vortex" refers to a region of airflow that rotates about a central axis.

As used herein, the term "soiling" includes any deposition of a dirt on the vehicle. As used herein, the term "dirt" includes any unwanted substance that may be deposited on the vehicle. This may include but is not limited to water, mud or fine particulates. The dirt may be carried in air, in water carried in the air, in droplet or aerosol form, for example.

As used herein, "attached airflow" is airflow that has not separated from the object it is travelling over. Attached airflow may be laminar or turbulent airflow. As used herein, separated airflow is where high velocity air moving along the vehicle underbody is replaced with lower velocity recirculating air. Flow separation occurs when the flow encounters an adverse pressure gradient along a surface and the flow slows down at the surface or reverses in direction separating the higher velocity flow away from the surface. The separation contains recirculating air, airflow at lower velocities and typically lower pressures.

As used herein, the term "centre of vehicle underbody" includes but is not limited to the region on the vehicle underbody excluding the wheels. "Centre of vehicle underbody" may be considered to be the region between the suspension arms on the underbody of the vehicle. "Centre of vehicle underbody" may be considered to be the region of the vehicle underbody within 5 cm, 10 cm, 15 cm, 30 cm, 40 cm, 50 cm, 70 cm or 80 cm either side of the centreline.

As used herein "airflow transmitted along the centre of the vehicle underbody" includes airflow that passes underneath at least a portion of the centre of the vehicle underbody. This may include only airflow that flows within 15 cm, 10 cm, 5 cm or 2 cm beneath the centre of the vehicle underbody. This may include only airflow that is not part of the wakes from the wheels.

As used herein, the term "airflow that exits from the rear of vehicle underbody" includes but is not limited to airflow that has travelled under at least part of the centre of the vehicle underbody and has passed rearward out from under the centre of vehicle underbody.

As used herein, the term "supress" includes but is not limited to reducing the magnitude or diameter of a vortex, lowering the height of a vortex, moving a vortex rearward, and/or preventing the formation of a vortex.

As used herein, the term "centre of vehicle underbody" includes but is not limited to the region on the vehicle underbody excluding the wheels. "Centre of vehicle underbody" may be considered to be the region between the suspension arms on the underbody of the vehicle. "Centre of vehicle underbody" may be considered to be the region of the vehicle underbody within 5 cm, 10 cm, 15 cm, 30 cm, 40 cm, 50 cm, 70 cm or 80 cm either side of the centreline. As used herein "airflow transmitted along the centre of the vehicle underbody" includes airflow that passes underneath at least a portion of the centre of the vehicle underbody. This may include only airflow that flows within 15 cm, 10 cm, 5 cm or 2 cm beneath the centre of the vehicle underbody. This may include only airflow that is not part of the wakes from the wheels.

As used herein, the term "rear stagnation point" may be considered as the point behind the vehicle where the airflow reaches zero velocity when averaged over time. The rear stagnation point is in the centre of the region of high pressure created when the recirculating air in the wake behind the vehicle is directed to the rear surface of the vehicle. A spoiler, vehicle and method in accordance with embodiments of the present invention will now be described with reference to the accompanying Figures.

With reference to Figure 1 and Figure 2, a vehicle 2 may comprise a body having a rear surface 14, and an underbody 34. The rear surface 14 of the vehicle is a region susceptible to spoiling by dirt entrained in the wake behind the vehicle 2 when it moves forwards. The rear surface 14 of the vehicle 2 may comprise a rear window and/or body panelling. A spoiler 4 is shown in figure 1 attached to the top of the rear surface 14.

The rear surface 14 of the vehicle 2 may have a rake angle between 20 and 70°, or between 30 and 60°, or between 40 and 50° when measured to the vertical. The rake angle is considered to be the angle between the panel beneath the spoiler 4 and the vertical when a section along the centreline is considered (as shown in figure 2, by angle Θ). Where the panel beneath the spoiler 4 is curved, the average angle of the panel is used, as is the angle at the centreline

The spoiler 4 extends over the rear surface 14, which, in combination with the rake angle of the rear surface 14, provides a volume 1 1 beneath the spoiler in which a vortex can be formed.

The spoiler 4 may extend in the horizontal direction by at least 200 mm, 300 mm, 400 mm, 500 mm or 600 mm. The spoiler 4 may extend by an amount not exceeding 500 mm, 600 mm, 700 mm, 800 mm or 900 mm. The spoiler 4 may extend by any range using any combination of the aforesaid values. The extent of the spoiler 4 in the horizontal direction may be measured in the horizontal direction from the rear most part of the spoiler 4 to the plane formed by the rear surface 14 as shown in figure 2 by dimension 28. The spoiler 4 provides a barrier to prevent airflow travelling rearward over the top of the spoiler 4 mixing with air recirculating in the vortex formed in the volume 1 1 beneath the spoiler 4 it is thus advantageous that the spoiler 4 extends by at least 200mm to promote the formation of a vortex in the volume 1 1 when the vehicle 2 is in motion.

The spoiler 4 comprises a channel 6 which directs airflow from above the top of the vehicle 2 to below the spoiler 4, as illustrated by arrow 8 in figure 1 . The channel 6 may be a slot or other passage through the spoiler 4, the channel 6 may be bounded by walls within the spoiler 4 only or be bounded in part by the vehicle body, for example. By redirecting airflow towards the rear surface, 14, soiling of the rear surface 14 can be reduced. The airflow redirected by the spoiler 4 forms a jet of air that is directed over the rear surface 14 into the volume 1 1 beneath the spoiler 4. The jet of air helps to preserve momentum within the airflow in the direction of the channel 6 which mitigates against the airflow attaching to the rear surface 14 of the vehicle 2. The jet of air may be a free rectangular jet.

The top line or roof of a vehicle 2 may extend in the rearward direction beyond the rear surface 14 of the vehicle 2. In this case, the extent of the spoiler 4 in the horizontal direction is inclusive of the portion of top line or roof of the vehicle that extends beyond the plane of the rear surface 14. Extending the top line or roof of the vehicle 2 beyond the rear surface 14 is advantageous as it prevents the jet of air exiting the channel 6 from attaching to the rear surface 14 of the vehicle 2, thus the detached airflow exiting the channel 6 may be circulated upwardly towards the spoiler 4 more efficiently. This promotes the efficient generation of a vortex in the volume 1 1 .

The channel 6 produces a jet of air to establish a vortex, typically a free rectangular jet. Thus, air flowing through the channel 6 exits from the channel 6 where the majority of the airflow flows approximately parallel to the rear surface 14 of the vehicle 2 and is then circulated upwards towards the rear face 10 of the spoiler. Circulating the airflow upwards towards the rear face 10 of the spoiler 4 encourages the formation of a vortex within the volume 1 1 beneath the spoiler 4. The body of the spoiler 4 also raises the angle of the airflow that flows from the top of the rearward edge as it separates from the vehicle 2. This airflow then enters the wake behind the vehicle 2 at a lower point than it would have without the spoiler 4. This creates a stagnation point further down the rear of the vehicle body and may also create conditions which favour the vortex 12 to rotate in the desired direction. The vortex 12 provides a substantial reduction of soiling by redirecting dirty air from under the vehicle underbody away from the rear surface 14.

The channel 6 is positioned rearward to the plane formed by the rear surface 14. The exit to the channel 6 may be positioned rearward from the plane formed by the rear surface when measured in the horizontal direction. The spacing may be between 5 mm and 900 mm, or between 10 mm and 500mm or between 15 mm and 400 mm or between 50 mm and 300 mm, or between 100 mm and 200 mm or any range comprising any of the aforementioned values. Positioning the channel 6 rearward of the plane formed by the rear surface 14 is advantageous as it reduces the chance of the jet attaching to the rear surface 14. If the jet of air attaches the rear surface 14 it is harder to recirculate the air upwardly towards the rear surface of the spoiler 4 to generate the vortex 12. The vortex 12 forms against rear surface 14 and rotates downward and then outward from the rear surface 14, or as shown in figure 1 , rotates counter clockwise when viewed from the left side of the vehicle 2. This means the vortex 12 may comprise clean air from the top of the vehicle and may protect the rear surface 14 of the vehicle 2 from the dirty air circulated up from the ground in the wake behind the vehicle.

The rotating of vortex 12 may also reduce drag by increasing the pressure immediately rearward of the spoiler, because additional airflow is directed to this region. The increase of pressure in this region may reduce the pressure drag of the vehicle 2.

A spoiler which extends in the horizontal direction by at least 200 mm when measured from a plane formed by the rear surface 14, the spoiler 4 comprising a channel 6 to direct airflow from above the top of the vehicle 2 to below the spoiler 4 when the vehicle 2 is in motion may be used to form a vortex 12 where the airflow moves downward approximately parallel to the rear surface 14 of the vehicle 2 and is circulated upward towards the rearmost edge of the spoiler, which reduces soiling on the rear surface 14 of the vehicle 2. Thus soiling on the rear of a vehicle may be reduced by a method comprising attaching a spoiler 4 to the vehicle 2, the spoiler 4 having a channel 6; and wherein when the vehicle 2 is in motion, the spoiler 4 directs airflow from the top of the vehicle 2 to below the spoiler 4 through the channel 6, to form a vortex 12 where airflow is directed downwards, approximately parallel to the rear surface 14 of the vehicle 2, and circulated up towards the rear face of the spoiler 4.

In embodiments, the spoiler may comprise a rear face which extends downward at least 200 mm in the vertical direction. The rear face may extend at least 500 mm, or 700 mm, or 900 mm, and may optionally extend no more than 600 mm, 800 mm, 1200 mm and/or any range with any combination of the aforesaid values. The rear surface may provide bulk that may additionally encourage the vortex to form and may reduce the amount of air that passes over the rear airflow from over the spoiler to stagnate rearward of or beneath the spoiler.

In embodiments, the vortex may be formed when the vehicle 2 is travelling at certain speeds. In this case, the amount the spoiler 4 extends and the rake angle of the vehicle 2 may be used to configure the spoiler 4 so that the vortex appears at the desired speed. In addition, the channel size and offset of the uppermost edge of the forward facing face to the uppermost edge of the rearward facing face of the channel may be used also. The desired speed may be considered to be the speed (or range of speeds) at which rate of soiling of the rear surface is most problematic. Values of the aforesaid parameters may be established using methods known in the art, for example computationally e.g. by using computational fluid dynamics simulations or experimentally, e.g. by using wind tunnel testing. In embodiments, the channel has an angle of ±10° to the angle of the rear surface 14 of the vehicle 2. In alternative embodiments this may be ±15°, ±10°, ±5°, ±1 ° or parallel thereto. The angle of the channel 6 relative to the rear surface 14 may be considered to be the angle formed between the rear surface 14 and the line which equally bisects the channel, when viewed from the side.

In embodiments, the at least one channel 6 has a length of at least 10 mm. The channel length may be at least 20 mm, 30 mm, 40 mm, 60 mm, 80 mm or 100 mm. The channel length may provide a suitable length in which the exiting flow exits in a 'jet' form, which may help form a vortex. Values of the aforesaid parameter may be established using methods known in the art, for example, computationally by using computational fluid dynamics simulations.

In embodiments, the at least one channel 6 comprises forward and rearward facing faces 16, 22 with a spacing of at least 10 mm there between measured across the narrowest dimension of channel 6 (as shown by dimension W on figure 2). The spacing may alternately be between 5 and 20 mm, 10 and 30 mm, 15 and 40 mm and 20 and 50mm, or ranges with any combination of the aforesaid values. Spacing may be used to determine the amount of airflow entering the channel. Values of the aforesaid parameter may be established using methods known in the art, for example, computationally by using computational fluid dynamics simulations. As shown in Figure 2, the exit to the channel 6 may be divergent. Having a divergent exit to the channel 6 encourages detachment of the airflow as it exits the channel 6 which helps the airflow to form a free rectangular jet that is detached from the rear surface 14.

In embodiments, the at least one channel 6 comprises a forward facing face 16 having an upper edge 18 and a rearward facing face 22 having an upper edge 24 which is between 10 mm above and 20 mm lower than the upper edge 18 of the forward facing face 16. This distance between upper edges 18 and 24 is referred herein as "offset". The offset may be measured perpendicular to the top line of the vehicle where it is incident to the channel 6 as shown in figure 2 by dimension H. In embodiments of the invention the offset is between 0mm and 15mm in height.

In embodiments, the lowermost edge of the forward facing face 16 and/or the rearward facing face 22 of the channel 6 comprise sharp edges with radii less than 20 mm. This may provide clean detachment of the flow from the spoiler 4 as the airflow exits the channel 6. This helps to form a free rectangular jet of air that is directed over the rear of the vehicle 104. The free rectangular jet is detached from the rear surface 14 and the spoiler 4 of the vehicle 2 which helps prevent the jet diffusing and forming a diffuse airflow. The free rectangular jet has higher centreline momentum than an equivalent wall bounded jet or diffuse airflow which is advantageous as the higher centreline momentum helps maintain the jet of air which may then be circulated upwardly towards the spoiler to efficiently form the vortex 12. In embodiments, the forward facing face 16 and rearward facing face 22 of the channel 6 are at an angle between ±20° relative to each other. Where either face is not straight the average angle of the face may be considered. In embodiments, the channel may taper towards or from the exit of the spoiler. In embodiments, the at least one channel 6 extends between 50 and 95 % of the total width of the spoiler 4, where width is the dimension perpendicular and horizontal to the direction of travel of the vehicle 2. With reference to figure 3 a spoiler 4 is shown attached to a vehicle 2. The spoiler comprises a channel 6 comprising 3 sections. The width of the channel is the cumulative width of these sections 32. The total width of the spoiler 4 is shown by dimension 30. In embodiments, the spoiler 4 is configured so that it redirects between 10 and 30 percent of the airflow that is moving within a layer above the top of the vehicle 2, where the height of the layer above the top of the vehicle is five times the size of the width of the channel 6, wherein the redirected air is redirected through the spoiler channel 6, when the vehicle 2 is travelling between 30 and 180 km/h, or optionally between 50 and 100 km/h or any range with any combination of the aforesaid values. The spoiler may be configured by changing the offset, channel spacing, channel angle or other parameters mentioned herein. These may be determined by using computational fluid dynamics simulations or other methods known in the art.

In embodiments, the spoiler 4 is configured so that the velocity of the airflow through the channel 6 is between 30% and 80% of the freestream velocity, when the vehicle 2 is travelling between 30 kph and 180 kph, or optionally between 50 and 100 km/h or any range with any combination of the aforesaid values. The spoiler may be configured by changing the offset, channel spacing channel angle or other parameters mentioned herein. These may be determined using by using computational fluid dynamics simulations or other methods known in the art.

In embodiments, the volume of air through the channel 6 is from 0.1 to 0.5 m³/s when the vehicle 2 is travelling between 30 and 100 km/h, or optionally between 50 and 100 km/h or any range with any combination of the aforesaid values. The spoiler may be configured by changing the offset, channel spacing, channel angle or other parameters mentioned herein. These may be determined by using computational fluid dynamics simulations or other methods known in the art.

In embodiments, the vehicle further comprises a spoiler 50 on the underside 52 of the vehicle 2, see for example figure 4.

The underbody spoiler 50 may be protrude downward from the underbody 52, so that when the vehicle is in motion, the airflow transmitted along the centre of the vehicle underbody is altered by the underbody spoiler, so that the airflow that exits from the rear of the vehicle underbody is supressed from forming a vortex proximal to the rear surface of the vehicle, to reduce soiling on the rear of the vehicle by dirt suspended in the airflow, compared to soiling for the vehicle without the underbody spoiler. The underbody spoiler alters the airflow exiting from the underbody of the vehicle, and in particular, may alter the airflow moving approximately parallel to the centreline of the vehicle. By providing an underbody spoiler that can be deployed in an operative configuration that protrudes downward from the vehicle underbody, the formation of vortices proximal to or against the rear surfaces of the vehicle body may be supressed. In particular, supressing vortices which form close to the road surface which tend to recirculate dirty air. Suppression may include, for example, displacing the vortices downward or rearward from the rear surfaces of the vehicle, preventing vortices from forming or reducing the diameter, magnitude or the amount of air in the vortex. By supressing the airflow exiting from the vehicle underbody from forming vortices proximal to the vehicle body, the soiling on the rear surface of the vehicle may be reduced. This may occur partly because circulation of the airflow containing dirt from the road surface against the rear surface of the vehicle is reduced. By supressing vortices proximal to the rear surfaces formed from air exciting the vehicle underbody, an increased amount of air flow from over the top of the vehicle may circulate against the rear surfaces instead, airflow from over the top of the vehicle may contain less dirt and so reduce the soiling on the rear surface of the vehicle.

By using a spoiler 4 in combination with an underbody spoiler 50 a reduction of soiling is achieved that is greater than when either spoiler is used alone. This is believed to occur because the combined effect on the vortices behind the vehicle achieves highly favourable flow patterns for the reduction of soiling.

In embodiments, the body of the underbody spoiler 50 is a planar member. This shape may provide a spoiler with simplified ease of construction, and is a shape that may provide good alteration of airflow for reduction of soiling. In embodiments, a planar surface of the underbody spoiler 50 is orientated perpendicular or substantially perpendicular to the direction of travel of the vehicle. By orientating the underbody spoiler 50 perpendicular to the air flow or close to it, further reduction of soiling may be achieved. In embodiments, the underbody spoiler 50 may protrude from the underbody between 5 and 80mm, or between 10 and 60 mm, or between 20 and 40mm, or a range with any combination of the aforesaid values. A protrusion of this amount may provide the improved reduction of soiling. the underbody spoiler 50 may be positioned or deployed between 0 cm and the rear most point of the vehicle underbody, or between 0 cm and 100 cm rearward of the rear axle, or between 20 cm and 80 cm rearward of the rear axle, or between 40 cm and 60 cm rearward of the rear axle, or between any combinations of the aforesaid end points.

With reference to Figure 5, a vehicle 104 may comprise a body having a rear 108, and an underbody 106. The rear of the vehicle body is a region of the vehicle susceptible to spoiling by dirt entrained in the wake behind the vehicle 104 when it moves. The rear of the vehicle 104 may comprise a rear window and body panelling. A vehicle underbody 106 may comprise an irregular surface formed from exposed components of the vehicle, or may comprise a panel, covering the underbody components of the vehicle. The rear 108 may encompass the rear surface 1 14, which may be considered the upper portion of the rear 108.

A vehicle typically comprises a reference line or plane called the ground line. The ground line is a line, or plane, parallel to the road surface and coincident with the lowest permissible rigid part of the underbody. The height of the ground line may also define the ground clearance height of the vehicle.

A vehicle typically comprises a reference line or plane called the departure line. The departure line is a line, or plane, from the points in which the rear tyres contact the road to the rearmost portion of the vehicle. The angle between departure line and ground, known as the departure angle is the maximum angle the vehicle can achieve when driving over obstacles or transitioning to steep ground.

With reference to Figure 5, a second spoiler 102 is shown attached to the underbody 106, of a vehicle 104. The spoiler comprises a body and an attachment means (not shown). The attachment means is for attaching the second spoiler to the vehicle. The second spoiler is shown deployed behind the rear axis 1 10 and is centred over the centreline of the vehicle. The second spoiler 102 is shown positioned rearward of the rear axis 1 10 by approximately 500 mm. The rearward distance of the second spoiler may be calculated by measuring the horizontal separation (i.e. distance parallel to the ground or ground line) between the centre of the rear axis and the second spoiler, as illustrated in figure 5, numeral 1 1 1 . The second spoiler shown in figure 5, comprises a body formed as a planar member, positioned so that it extends close to the ground line 1 12 and the departure line 1 14 of the vehicle. The second spoiler 102 is positioned so a planar face of the spoiler is orthogonal to the air direction when the vehicle is moving forward, i.e. perpendicular to the forward direction of the vehicle 104. In this particular embodiment, the second spoiler is shown mounted to the underbody by attaching the second spoiler 102 to the lowermost surface of the battery box 20 of the vehicle underbody.

'Deployed' in the context of the invention includes the spoiler being attached integrated or mounted to the underbody. 'Deployed' also includes the spoiler being moved from a position where it does not spoil the airflow (for example, with the spoiler body parallel to the air flow) to one where it can spoil airflow (for example, with the spoiler body perpendicular to the airflow). Figure 6 shows a vehicle 103 without a second spoiler fitted, in side view A and rear view B, and a vehicle 104 with a spoiler 102 fitted, in side view C and rear view D. In D the spoiler 2 is shown as the white rectangular region for which the longest dimension is the width and the shortest is the protrusion of the spoiler. Stream lines are drawn on side views A and C to illustrate the air flow that passes above and underneath the vehicle 103, 104 when it is moving forwards. As can be seen by a comparison of the stream lines between A and C, the effect of the second spoiler 102 is to alter airflow in rear wake. The second spoiler may achieve this by, creating a higher static air pressure in the airflow moving along the underbody of the vehicle, directly behind the spoiler and increasing acceleration of air to the sides and below the spoiler. This may supress the airflow exiting from along the centre of the vehicle underbody from forming a vortex proximal to or against the rear surface of the vehicle. This may move the vortex rearwards from the vehicle, lower is its axis or rotation, velocity of rotation or amount or airflow circulating, or prevent vortex formation. Suppression of a vortex may reduce entrained dirt in the airflow from reaching the rear of the vehicle, or may lower the height at which entrained dirt is deposited. The second spoiler may also separate the wakes formed behind the wheels from the rear wake. The spoiler may also cause increased airflow from the top of the vehicle proximal to the rear surface of the vehicle. The change in wake behind the vehicle may reduce entrainment of road spray in the wake and increases the amount of airflow from over the top or around the car that is circulated in the wake. This may further reduce the airflow from underneath the vehicle rising into the rear wake, thereby further reducing the amount of road spray entrained into the rear wake. A spoiler of the invention may protrude down into the higher velocity air flowing beneath the largely separated and low velocity airflow regions, which result from turbulent interactions with the underbody of the vehicle. The second spoiler 102 may be flexible, as illustrated in figure 5. The hatched lines 122, illustrate deflection of the spoiler, which may deflect if, for example, the vehicle drives over a high object. Because air flow speed increases the faster a vehicle is driven, a flexible spoiler may need to have sufficient rigidity to resist higher air speeds to maintain its position, but still be sufficiently flexible to deform when in contact with an object.

A flexible spoiler may be achieved for example, by using an inherently flexible material, such as a rubber or other flexible polymer. Flexibility can be varied by using different thickness or by cutting grooves or other points of weakness into the material. The spoiler may also comprise a rigid material such as a metal or polymer. The spoiler may be hinged to the underbody or comprise multiple hinges along its length, each hinge may act against a biasing means such as a spring to retain it in a deployed position. The second spoiler may protrude from the underbody, this may include but is not limited to protruding between 5 and 80 mm, or between 10 and 60 mm or between 20 and 40 mm, or any combination of the aforesaid values. The second spoiler may also protrude to the ground line, or protrude beyond the ground line. The second spoiler may also protrude to the departure line, or protrude beyond the departure line.

The width of the second spoiler may be between 100 mm and the width of the vehicle, or between 200 mm and 1000 mm, or between 500 mm and 300 mm, or a range of any combination of the aforesaid values. As used herein, "width" in reference to a spoiler includes the total span of the body of the spoiler in a direction perpendicular to the direction of travel of the vehicle and parallel to the ground. Specifically, this may refer to the largest overall dimension of the spoiler body in some embodiments.

The body of the second spoiler may comprise any shape capable of spoiling the airflow. This may include planar members, boxes, channels or hollow members, or any combination of these. The body of the spoiler may additionally comprise ridges, grooves or channels to direct airflow. A planar member provides a shape that can be retracted easily to lie flat against the underbody, it can also easily be made to be flexible. The body of the spoiler refers to the main portion of the spoiler that is exposed to airflow, i.e. excluding a portion for attaching the second spoiler to a vehicle.

Portions of the second spoiler may be orientated, shaped or arranged differently to the rest of the body of the spoiler to direct airflow, for example, the second spoiler may be configured so that a portion of the airflow is directed around the sides of the spoiler or towards the lateral edges of the vehicle.

The second spoiler may be positioned anywhere on the underbody of the vehicle. The second spoiler may be positioned between the front wheels or rear wheels, or rearward thereof. This position may permit air to pass between the wheels and the second spoiler which may cause an increase of airflow parallel to and rearward of the wheels to direct the wheel wakes outward which may further reduce soiling. The second spoiler may be positioned so as not to interact with turbulent airflow coming from the wheels, in particular, the rear wheels. The second spoiler may be centred over the centreline of the vehicle or positioned laterally. The second spoiler may be positioned between the rear axle and the rear edge of the vehicle. The vehicle may comprise one underbody (second) spoiler or more than one.

The second spoiler attachment portion may be attached to the vehicle using any known fastening method that provides a sufficiently secure connection. The second spoiler attachment portion may comprise fasteners or mounting points to facilitate attachment to the vehicle. Fasteners may include screws, clips, quick release systems and other known fastening systems. The vehicle may comprise a mounting point on the underbody. Mounting points may include pins, holes (for example, for screws) or any shape that may be aligned with a corresponding shape on the second spoiler. The second spoiler may be attached to the vehicle permanently, or releasably so that the spoiler can be detached from the vehicle. The second spoiler may also be movably attached to the vehicle underbody. Alternatively, the second spoiler may be incorporated into a component on the underbody, for example, a battery box may be shaped so that it includes a planar member that extends below the vehicle underbody.

The second spoiler may be configured so that it can be deployed in a position where it spoils airflow to reduce soiling, and to a portion where it does not spoil airflow. The spoiler, may comprise an attachment portion to attach the second spoiler to an attachment point on the vehicle. The attachment portion may enable attachment of the spoiler in any of the aforementioned positions. For example, the second spoiler may be connected to the vehicle underbody with a hinge. The hinge may permit the spoiler to move between a position where it extends into airflow under the vehicle underbody and one where it is retracted to lie flat against the vehicle underbody. The spoiler or vehicle may comprise clips or any other locking mechanisms which secure the spoiler in either of these positions. This may improve usability allowing the second spoiler to be deployed when reduction of soiling is required (e.g. wet road conditions), and retracted when not required, (e.g. dry conditions, or when maximum ground clearance is needed). In a similar manner, the second spoiler may be configured to be positioned in multiple positions between one of maximum protrusion into the airflow beneath the vehicle underbody, and one of minimum protrusion thereto. This may improve usability allowing the user to match protrusion and therefore extent the second spoiler interferes with the airflow, to the driving conditions, such as vehicle speed, or wind speed, or off-road use.

EXAMPLE Figure 7 shows computational fluid dynamics (CFD) images from a computational fluid dynamics model with taken from the centreline of a vehicle. Image A shows a vehicle 2 with a spoiler fitted but with no channel as described herein and image B shows a vehicle 2 with a spoiler 4 of the invention mounted on the top of the rear surface of the vehicle. The lines represent velocity distributions and flow paths along the centreline of the vehicle. 61 is an example of a high velocity region and 62 is an example of a low velocity region. 63 shows a vortex rearward of the rear surface and in the volume 1 1 beneath the spoiler where a spoiler of the invention 4 is fitted. Vortex 63 is rotating downward immediately rearward of the rear surface 14, further rearward, the vortex 63 is rotating upwards towards the spoiler 4. No similar vortex structure is evident in image A. Furthermore there is an increase of pressure immediately rearward of spoiler 4 in image B, which further reduces pressure drag.

The vortex 63 formed in the volume 1 1 beneath the spoiler 4 receives a clean jet of air from the channel 6 which passes over the rear surface 14 of the vehicle 2 and is circulated upward towards the rear surface of the spoiler 4 due to the rake angle of the vehicle 2 illustrated in Figure 7. The vortex 63 recirculates clean air over the rear surface 14 of the vehicle 2 thus mitigating soiling of the rear surface 14. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. The claims should not be construed to cover merely the foregoing embodiments, but also any embodiments which fall within the scope of the claims.

Claims

A vehicle comprising:

a rear surface of the vehicle with a rake angle between 30 to 60° to the vertical; and

a spoiler which extends in the horizontal direction by at least 200 mm when measured from a plane formed by the rear surface , the spoiler comprising:

a channel to direct airflow from above the top of the vehicle to below the spoiler when the vehicle is in motion, so that airflow exiting the channel forms a vortex where the airflow moves downward parallel to the rear surface of the vehicle and is circulated upward towards the rearmost edge of the spoiler, to reduce soiling on the rear surface.

A vehicle according to claim 1 , wherein the channel is at an angle of between ± 10° to the rake angle of the rear surface of the vehicle.

A vehicle according to any previous claim wherein the at least one channel has a length of at least 10 mm.

A vehicle according to any previous claim wherein the at least one channel comprises forward and rearward facing faces with a spacing of at least 10 mm there between.

A vehicle according to any previous claim wherein the at least one channel comprises a forward facing face having an upper edge and a rearward facing face having an upper edge which is between 10 mm above and 20 mm lower than the upper edge of the forward facing face.

A vehicle according to any previous claim wherein the channel has a length between 20 and 80 cm.

A vehicle according to any previous claim wherein the lowermost edge of the forward facing face and/or the rearward facing face of the channel comprise sharp edges with radii less than 20 mm.

8. A vehicle according to any previous claim wherein the spacing between the forward facing face and the rearward facing face is between 10 and 30 mm, measured at the top of the channel.

9. A vehicle according to any previous claim wherein the forward facing face and rearward facing face of the channel are at an angle between ± 20° relative to each other.

10. A vehicle according to any previous claim wherein the at least one channel extends between 50 and 95 % of the total width of the spoiler, where width is the dimension perpendicular and horizontal to the direction of travel of the vehicle.

1 1. A vehicle according to any previous claim wherein the spoiler redirects between 10 and 30 percent of the airflow that is moving within a layer above the top of the vehicle, where the height of the layer above the top of the vehicle is five times the size of the width of the channel, wherein the redirected air is redirected through the spoiler channel, when the vehicle is travelling between 30 and 180 km/h.

12. A vehicle according to any previous claim wherein the airflow velocity through the channel is between 30% and 80% of the freestream velocity, when the vehicle is travelling between 30 kph and 180 kph.

13. A vehicle according to any previous claim wherein the flow rate through the channel is 0.1 to 0.5 m³/s when the vehicle is travelling between 30 to 100 km/h.

14. A vehicle according to any previous claim wherein the air exits the channel with a velocity of between 6 and 20 m/s when the vehicle is travelling between 50 to 100 km/h.

15. A vehicle according to any previous claim which further comprises a spoiler on the underside of the vehicle.

16. A vehicle according to any previous claim, wherein a portion of the vehicle extends beyond the rear surface of the vehicle in the rearward direction, wherein the spoiler extends at least 200 mm when measured from a plane formed by the rear surface to the rearmost portion of the spoiler, inclusive of the portion of the vehicle that extends beyond the rear surface in the rearward direction.

17. A vehicle according to any previous claim, wherein the exit to the channel is positioned rearward from the plane formed by the rear surface between 10 and 500 mm, when measured in the horizontal direction.

18. A vehicle according to any previous claim, wherein the airflow exiting the channel is a free rectangular jet.

19. A vehicle comprising:

a first spoiler comprising a channel to direct airflow from above the top of the vehicle to below the first spoiler when the vehicle is in motion, to reduce soiling on the rear surface; and

a second spoiler attached to an attachment point on the underbody of the vehicle, the second spoiler protruding downward from the underbody, to alter the airflow transmitted along the centre of the vehicle underbody when the vehicle is in motion, to suppress the airflow that exits from the rear of the vehicle underbody from forming a vortex proximal to the rear of the vehicle, to reduce soiling on the rear of the vehicle by dirt suspended in the airflow.

20. The vehicle of claim 19, wherein the first spoiler is configured so that airflow exiting the channel forms a vortex where the airflow moves downward parallel to the rear surface of the vehicle and is circulated upward towards the rearmost edge of the first spoiler.

21. The use of a spoiler(s) as defined in any preceding claim to reduce soiling on the rear of a vehicle.

22. A method of reducing soiling on the rear of a vehicle comprising:

providing a vehicle with a spoiler, the spoiler having a channel; and wherein when the vehicle is in motion, the spoiler directs airflow from the top of the vehicle to below the spoiler through the channel, to form a vortex where airflow is directed downwards, parallel to the rear surface of the vehicle, and circulated up towards the rear face of the spoiler.

23. A method according to claim 22 wherein the spoiler redirects between 10 and 30 percent of the airflow within a distance equal to 5 times the size of the width of the channel exit, above the top of the vehicle, when the vehicle is travelling between 30 and 180 km/h, and wherein the redirected airflow is redirected through the channel.

24. A method according to any of claims 22 to 23 the airflow velocity through the channel is between 30% and 80% of the freestream velocity, when the vehicle is travelling between 30 kph and 180 kph.

25. A method according to any of claims 22 to 24 wherein the spoiler redirects air through the channel with a flow rate of 0.1 and 0.5 m³/s when the vehicle is travelling between 20 to 30 km/h.

26. A method according to any of claims 22 to 25 wherein the flow rate through the channel is 0.1 to 0.5 m³/s when the vehicle is travelling between 30 to 100 km/h.

27. A method according to any of claims 22 to 26 wherein the rear surface of the vehicle has an angle of from 30 to 60 degrees to the vertical.

28. A method according to any of claims 22 to 27 further comprising attaching a spoiler on the underside of the vehicle.

29. A method according to any of claims 22 to 28 wherein the channel has a length between 20 and 80 cm.

30. A method according to any of claims 22 to 29 wherein the channel is at an angle of ± 10° to the rake angle of the rear surface of the vehicle.

31. A vehicle, the use of a spoiler, or a method of reducing soiling on the rear of a vehicle, substantially as described herein and optionally with respect to the accompanying drawings.