GB2353979A

GB2353979A - A vehicle aerodynamic stability device

Info

Publication number: GB2353979A
Application number: GB0021969A
Authority: GB
Inventors: Lionel Henry Townend
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-09-07
Filing date: 2000-09-07
Publication date: 2001-03-14
Also published as: GB0021969D0; GB9921148D0

Abstract

An aerodynamic stability device for a vehicle comprising aerodynamic surfaces or strakes (10), one on each side of the rear end of the vehicle. The rear end is also recessed and boat-tailed in regions (11), which thereby provides an overhang to the roof (12) which introduces swept leading edges (13) of the strakes (10). The wheel spats (21) can be of symmetrical section or cambered nose-in or cambered nose-out. A second set of strakes (22) is shown which may benefit aerodynamically, aesthetically or structurally by the provision of recessed bodywork over the rear wheel.

Description

2353979 VEHICLE AERODYNAMIC STABILITY DEVICE This invention relates to the

reduction of hazard and/or driver fatigue resulting from crosswinds by means of directional control and stability devices on a vehicle body.

Vehicle operation in a crosswind can give rise to the vehicle body turning "out of wind" (i.e. the nose or bows of the vehicle body moves laterally in the same direction as the crosswind is blowing). This is because the crosswind creates a region of high suction on the leeward side of the vehicle, and/or of raised pressure on the windward side, and because the regions of highest suction usually occur over the front 20% of the vehicle body length.

A vehicle such as an automobile may well continue on its intended path, but to the driver, the lateral movement of the front of the vehicle will give rise to the impression that the vehicle is veering off-course. This can lead to driver fatigue and/or to the driver making unwarranted steering corrections which are in fact unnecessary and can cause hazard to his own vehicle or to others.

It is known that the addition of a more or less upright or vertical fin (or fins) on top and at the rear of a vehicle can produce a reduction in the tendency to turn out of wind, but such fins are visually obtrusive, structurally weak and they can impose roll on a vehicle in the course of applying the required lateral force(s) and they can increase vehicle drag at certain wind -2conditions.

This patent describes an approach by which the effect of front end pressure and suction forces can be at least partly countered by forces produced on the side surfaces approaching the tail or stern of the vehicle, and by means which are stylistically acceptable.

According to the present invention, there is provided an aerodynamic stability device for a vehicle comprising one or more aerodynamic surfaces mounted in a generally streamwise and/or horizontal position adjacent to and/or mounted on a side of the vehicle to provide an overhang to the roof or a protruding ledge from the vehicle body thereby forming reentrant corner(s) or concavity into which and along which the airflow is taken at least in part from the airflow passing over the vehicle surface, and is eventually discharged from either or both of the vehicle roofflow and/or the vehicle sideflow.

The aerodynamic surfaces are mounted in a generally horizontal position both when viewed from the side and when viewed from in front/behind i.e. they are mounted so that the leading edges of the aerodynamic surfaces are not far from substantially horizontal or generally parallel to the roofline of the vehicle but they may also be upwardly or downwardly inclined from the horizontal along part or the whole of their length along the vehicle, for example to meet aerodynamic, aesthetic or constructional requirements of a particular vehicle design.

The aerodynamic surfaces may be mounted so as to be significantly swept along part or the whole of the leading and/or trailing edges of the aerodynamic surface, for example to meet aerodynamic, aesthetic or constructional requirements of a particular vehicle design, and in particular to avoid excessive protuberance or protrusion from the vehicle body by way of excessive width.

The aerodynamic surfaces are preferably mounted on the vehicle afterbody, i.e. on the rearmost half of the vehicle body, and may extend downstream of the vehicle body, and the local baseplane, but the upstream ends of the aerodynamic surfaces may start upstream of the halflength position.

The aerodynamic surfaces can be mounted directly to and/or contiguously with the side of the vehicle and may be attached as additional features to the side of existing vehicles. In addition or alternatively the side of the vehicle may be recessed so as to form a channel or trough in the side of the vehicle body adjacent to the aerodynamic surface. Recessing the vehicle body adjacent to the aerodynamic surface enables the provision of a more deeply reentrant vehicle side recess between the aerodynamic surface and the parts of the vehicle body beneath the aerodynamic surface sufficient to allow a substantial overhang on the aerodynamic surface which can thus project substantially out beyond the plane of the upper parts of the vehicle side. Recessing the vehicle body may provide advantages both in appearance and effectiveness of the device. The aerodynamic surface and recessed side of the vehicle can be profiled to achieve enhanced performance in terms of improved stability or reduced drag or both. In a preferred embodiment described hereinafter the vehicle is also profiled to have a partly boattail configuration, that the vehicle is tapered in the downstream direction so that the vehicle cross-section and width at certain levels diminish towards the vehicle baseplane.

The overhang of the aerodynamic surface must be large enough to allow an airflow passing along the vehicle side and under the lower face of the aerodynamic surface to be sufficient to generate the required lateral force or loading.

The airflow passing under, over and around the aerodynamic surface and the local vehicle body can be taken entirely from the airflow passing over the surface of the vehicle. In alternative embodiments airflow passing under, over and around the aerodynamic surface(s) may additionally be taken from other sources, (for example from the vehicle ventilation system) and/or at some location along or at the initiation of the aerodynamic device an intake for feeding internal systems may be integrated into the design. The airflow passing under, over and around the strake is discharged into or along the edges of the vehicle baseflow, that is the flow immediately adjacent to the vehicle's rearward extremities and/or into the vehicle wakeflow, that is the flow surrounding the baseflow and extending down stream of the vehicle itself. In one embodiment described herein after the airflow is discharged adjacent to the base and sides of the vehicle.

It is recognised that the addition of the aerodynamic surfaces to a vehicle without either or both boattailing or recessing the sides can also be effective, but the preferred design uses both boattailing and recessing on the grounds of appearance and effectiveness and safety.

on a conventional vehicle, such as a road car, operating in a moderate crosswind the resultant lateral force will act on the vehicle at a point usually about 20 to 25% rearward of the front of the vehicle body and at high crosswind conditions at a point which can be some 40 to 45% rearward of the front of the vehicle body. The nearer to the front of the vehicle that a given resultant lateral force acts the greater the "turning out of wind" effect of the crosswind will be and conversely if the position at which a given resultant lateral force acts is moved rearwardly the less "turning out of wind" effect the crosswind will have on the vehicle. A rearward shift of only a few percent of the vehicle body length of the position at which the resultant lateral force acts on the vehicle body can produce a significant improvement in the behaviour of the vehicle in a crosswind. By use of the aerodynamic stability device according to the present invention it is possible to move rearwardly the position at which the resultant force acts typically by 5% or greater of the length of the vehicle body.

The lateral force provided by the aerodynamic surfaces may be altered by changing the degree of overhang, inclination to the horizontal or sweep of the aerodynamic surfaces. The lateral force provided by the aerodynamic surfaces may be increased by increasing the size of the aerodynamic surfaces or using a plurality of the devices if appropriately placed. The greater the lateral force provided by aerodynamic surfaces at a given rearward location the more the point on the vehicle body at which the resultant lateral force acts will be moved rearwardly.

The aerodynamic surfaces may be curved or straight in sideview and/or in front or rearview and may carry or be operated in conjunction with, such additional devices as slatted leading edges, leading edge (vortex) flaps or trailing edge flaps, as may be found appropriate for such purposes as increasing rear-end side force in crosswinds, reducing associated drags in and/or out of crosswinds, reducing overall vehicle drag in and/or out of crosswinds, and/or for influencing the extent to which flows may remain attached to (rather than undergoing aerodynamic separation from) the surfaces of the vehicle and its associated features including the aerodynamic surfaces themselves.

In this connection, it is recognised that, in certain cases, separation of the flow may be deliberately provoked by the use of sharp leading edges or surface profiling such as ridges, but for compliance with vehicle safety legislation of many countries the leading edges are generally taken herein to be blunt or rounded.

The aerodynamic surfaces will usually be deployed in one or more pairs with one member of each pair on each side of the vehicle. In certain applications, it is recognised that a specialist vehicle may operate (continuously or otherwise) in crosswind(s) from only one side and that a single aerodynamic surface and/or some lack of vehicle symmetry may be acceptable and more appropriate to such vehicle(s). It is also recognised that, in certain applications, the relative effectiveness as between one or the other of a pair of the aerodynamic surfaces will vary with operating condition and that one or both can (in principle and in practice) be of variable geometry perhaps under manual or "active" control.

In another aspect the invention provides a method of improving the aerodynamic stability of a vehicle by providing the vehicle with at least one aerodynamic stability device according to the present invention.

In another aspect the present invention provides a vehicle having improved aerodynamic stability including at least one aerodynamic stability device according to the present invention.

The present invention is applicable to any vehicle which is susceptible to crosswinds. Such vehicles include, but are not limited to, cars, vans, motorcycles, lorries and other road vehicles and including trailers or caravans which may be towed by such vehicles and therefore be considered to form part of the vehicle such as the trailer of an articulated lorry. The present invention is also applicable to other vehicles such as speed or power boats, hydrofoil craft, hovercraft, railway vehicles or magnetically levitated vehicles.

Specific embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which the term "strakell is used to describe the aerodynamic devices which form the subject of this invention and in which:

Figure 1 shows in perspective the use of strakes and a degree of boattailing and recessed sides on a vehicle of mainly orthodox appearance.

Figure 2 shows drawings of a vehicle in which the further application of the invention now includes a second set of strakes and spatting of the rear wheels, and repreprofiled sills to increase the depth of the spats and/or to permit airflow from one side of the other to flow more readily beneath the vehicle and thereby to the inner faces of the spats.

Figure 3 shows four views of a car such as a "peoplemover" but modified from its standard form by the addition of strakes.

Figure 4 shows a view from the rear of a model car to show a typical base cross-section.

Referring to Figures I and 2 the drawing, the car body comprises a conventional front end with aerodynamic surfaces or strakes 10, one on either side of the rear end which is recessed and boattailed in regions 11, and thereby provides an overhang to the roof 12 thereby introducing swept leading edges 13. The wheel spats 21, at the rear end of the vehicle can be of symmetrical section or cambered nose-in or cambered nose-out. In addition, and whether cambered or of symmetrical section, the spats may be inclined. A second set of strakes is also shown as 22, and these may benefit aerodynamically, aesthetically or structurally by the provision of recessed bodywork over the rear wheel.

It is recognised that if one or both pair(s) of strake(s) and/or the spats are correctly located and cambered, or if they are provided with additional devices such as slats or flaps, then the wake flow, base flow and base pressures on the vehicle may be favourably influenced, in the sense that the vehicle aerodynamic drag may fall. In particular, with the use of appropriate camber and with the correct incidence on the surfaces, a reduction in the aerodynamic drag relative to that of the unmodified vehicle may become possible, at least at some conditions.

It is also recognised that for vehicles such as hatchbacks or conventional saloon cars the roofline in side elevation may limit the rearward extent that a roof edge strake would ideally and in principle require, and it is in this type of application that a plurality of devices may be beneficial

Claims

1. An aerodynamic stability device for a vehicle comprising one or more aerodynamic surfaces mounted in a generally streamwise and/or horizontal position adjacent to and/or mounted on a side of the vehicle to provide an overhang to the roof or a protruding ledge from the vehicle body thereby forming reentrant corner(s) or concavity into which and along which the airflow is taken at least in part from the airflow passing over the vehicle surface, and is eventually discharged from either or both of the vehicle roofflow and/or the vehicle sideflow.

2. An aerodynamic stability device according to claim I wherein the leading edges of the device are substantially horizontal or parallel to the roofline of the vehicle.

3. An aerodynamic stability device according to claim I or claim 2 wherein the leading edges of the device are upwardly or downwardly inclined from the horizontal for at least part of their length along the vehicle.

4. An aerodynamic stability device according to any of claims 1 to 3 wherein the device is swept along part or the whole of the leading and/or trailing edges of the aerodynamic surface.

5. An aerodynamic stability device according to any of claims 1 to 3 wherein the aerodynamic surfaces are mounted on the rearmost half of the vehicle body.

6. An aerodynamic stability device according to claim 5 wherein the upstream end of the aerodynamic surface starts in the foremost half of the vehicle body.

7. An aerodynamic stability device according to any of claims 1 to 6 wherein the device is mounted directly to or contiguously with the side of a vehicle.

8. An aerodynamic stability device according to any of claims 1 to 7 wherein the device is mounted in or adjacent to a recessed portion of the side of a vehicle.

9. An aerodynamic stability device according to any of claims 1 to 8 wherein the leading edges of the device are rounded or blunt.

10. An aerodynamic stability device according to any of claims 1 to 9 wherein the device carries or is operated in conjunction with slatted leading edges and/or leading edge flaps and/or trailing edge flaps.

11. An aerodynamic stability device according to any of claims 1 to 10 wherein the device provides increased stability in conditions of crosswinds.

12. A method of improving the aerodynamic stability of a vehicle which comprises providing an aerodynamic stability device according to any of claims 1 to 10.

13. A method according to claim 12 wherein additional airflow passing over the aerodynamic device is provided.

14. A method according to claim 13 wherein the additional airflow is provided from the vehicle -12ventilation system.

15. A method according to any of claims 12 to 14 wherein the stability of a vehicle in conditions of crosswinds is improved.

16. A vehicle comprising one or more aerodynamic stability devices according to any of claims 1 to 10.

17. A vehicle according to claim 16 wherein a portion of the side of the vehicle is recessed adjacent to the device.

18. A vehicle according to claim 16 or claim 17 wherein the vehicle is profiled to have a partly boattail configuration.

19. An aerodynamic stability device substantially as hereinbefore described with reference to the accompanying drawings.

20. A vehicle as substantially as hereinbefore described with reference to the accompanying drawings.