A vehicle

Abstract

A vehicle is provided with a ratio of the front overhang to the width of less than 0.48 and a ratio of the front overhang to the rear overhang is less than 0.82. The vehicle may be an electric vehicle

Description

TECHNICAL FIELD The present disclosure relates to a vehicle. Aspects of the invention relate to a vehicle. BACKGROUND It is known to provide an electric vehicle comprising an electric drive system including one or more electric motors and one or more traction batteries for supplying electrical power to the one or more electric motors, and associated power electronics and / or electrical control systems. The electric drive system is packaged inside a body of the vehicle formed from one or more body panels. The packaging of the components of the electric drive system within the vehicle may impact the dimensions of external surfaces of the body of the vehicle, which may in turn affect the aerodynamic performance of the vehicle. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a vehicle as claimed in the appended claims. According to an aspect of the present invention there is provided a vehicle comprising: a body having a front surface forming a front extent of the vehicle; and a front road wheel having a front wheel centreline, wherein a front overhang to width ratio of the vehicle, defined as a ratio of a distance between the front wheel centreline and the front extent of the vehicle to the width of the body, is less than 0.48, such as less than or equal to 0.44. According to another aspect of the present invention there is provided a vehicle comprising: a body having a front surface forming a front extent of the vehicle and a rear surface forming a rear extent of the vehicle; a front road wheel having a front wheel centreline; and a rear road wheel having a rear wheel centreline, wherein a front overhang to width ratio of the vehicle, defined as a ratio of a distance between the front wheel centreline and the front extent of the vehicle to the width of the body, is less than 0.48, such as less than or equal to 0.44, and wherein a rear overhang is defined as a distance between the rear wheel centreline and the rear extent of the vehicle, wherein a ratio of the front overhang relative to the rear overhang is less than 0.82, e.g. less than 0.8 or less than or equal to 0.76. For some vehicles, it may be desirable to reduce a front overhang to width ratio of the vehicle, e.g. in order to improve a packaging solution for packaging components for systems of the vehicle within an under bonnet space of the vehicle. Reducing the front overhang to width ratio of the vehicle may reduce aerodynamic performance of the vehicle, which can be offset by reducing a ratio of the front overhang relative to rear overhang relative. In particular, reducing the ratio of front overhang relative to rear overhang may improve pressure recovery at the rear of the vehicle body for a given vehicle length and without impacting vehicle system packaging. The body may comprise a roof surface defining an upper extent of the vehicle. A height to length ratio of the vehicle, defined as a ratio of a height of the roof surface above a ground surface to the distance between the front and rear extents of the vehicle may be less than 0.28, such as less than or equal to 0.27. Reducing a height to length ratio of the vehicle may reduce aerodynamic drag of the vehicle to further offset reduction in aerodynamic performance of the vehicle from reducing the front overhang to width ratio of the vehicle. A wheelbase of the vehicle, defined as a distance between the front wheel centreline and the rear wheel centreline in the longitudinal direction of the vehicle may be greater than or equal to 3m, such as greater than or equal to 3.2m. Increasing the wheelbase of the vehicle may be advantageous, particularly for vehicles with a low front overhang to width ratio, by enabling turbulence, generated as exterior air flow passes over the front road wheel of the vehicle, to dissipate sufficiently before reaching the rear wheel of the vehicle. The vehicle may be an electric vehicle, such as a Battery Electric Vehicle. Improving packaging of systems of the vehicle within the under bonnet space of the vehicle may be advantageous for electric vehicles, as it may allow batteries, and battery controllers and / or power electronics to be packaged together within the under bonnet space. The vehicle may further comprise a front bulkhead arranged between an under bonnet space of the vehicle and an interior cabin of the vehicle. A battery, and / or a battery controller and / or associated power electronics for controlling charging and discharging battery, may be arranged between the front wheel centreline and the front bulkhead. Packaging of batteries, and battery controllers and / or power electronics within the under bonnet space of the vehicle, e.g. between the front wheel centreline and the front bulkhead, may enable the height of the vehicle to be further reduced, e.g. compared to previous packaging solutions for these components, thereby improving overall aerodynamic performance of the vehicle. A maximum dimension of the front and / or rear road wheel between a rim portion of the road wheel and a centre point of the road wheel may be less than or equal to 6mm in a lateral direction of the vehicle. Reducing the maximum dimension of the front and / or rear road wheel between a rim portion of the wheel and a centre point of the wheel may reduce flow separation of an exterior flow of air over the wheel, which may assist in reducing outflows that drive the wheel wake wider, thereby minimising aerodynamic losses from turbulent flow structures that cascade along the side of the vehicle, particularly when a front overhang to width ratio of the vehicle is low. An open area of the front and / or rear road wheel, between a rim portion of the wheel and a hub portion of the wheel, for air flow though the road wheel in an axial direction of the road wheel may be less than 15% of a total area of the road wheel between the rim portion and the hub portion. Reducing the open area of the front and / or rear road wheel may reduce flow separation of an exterior flow of air over the wheel, which may assist in reducing the outflows that drive the wheel wake wider, thereby minimising aerodynamic losses from turbulent flow structures that cascade along the side of the vehicle, particularly when a front overhang to width ratio of the vehicle is low. The front and / or rear road wheel may comprise a tyre mounted on a rim portion of the front and / or rear road wheel. A side-wall height of the tyre may be greater than 110mm. Increasing the side-wall height of tyres of the front and / or rear wheel may reduce flow separation of an exterior flow of air over the wheel and encourage reattachment of the flow to the body of the vehicle downstream of the wheel, thereby improving aerodynamic performance of the vehicle. The front and / or rear road wheel may comprise a tyre mounted on a rim portion of the front and / or rear road wheel. A maximum dimension from the rim portion to a side-wall of the tyre mounted on the rim portion may be less than 10mm in a lateral direction of the vehicle. Reducing the maximum dimension from the rim portion to the side-wall of tyre may reduce flow separation of an exterior flow of air over the wheel and encourage reattachment of the flow to the body of the vehicle downstream of the wheel, thereby improving aerodynamic performance of the vehicle. The vehicle body may comprise a side surface forming a lateral extent of the vehicle. An angle of a portion of the side surface between the rear road wheel and rear surface may be less than or equal to 28 degrees, such as less than or equal to 23 degrees, relative to a longitudinal direction of the vehicle. Reducing an angle of the portion of the side surface may reduce flow separation of an exterior flow of air over the side surface, thereby improving pressure recovery at the rear surface of the vehicle and reducing vehicle drag. The body may comprise a rear corner edge between a side surface of the vehicle and the rear surface. The rear corner edge may be substantially vertical and may extend vertically over substantially the full height of the side surface. A rear corner edge extending vertically over substantially the full-height of the rear corner edge of the vehicle may improve stability of the air flow separating from the lateral side surface at the rear corner, and associated rear wake flow structures. This may improve pressure recovery at the rear surface reducing drag of the vehicle. The width of the vehicle may be greater than 1,99m, such as greater than or equal to 2.001 m. Increasing the width of the vehicle may enable packaging of components of vehicle systems to be improved. The front overhang of the vehicle may be less than 0.9m, such as less than or equal to 0.877m. Reducing the front overhang may enable packaging space in an under bonnet space of the vehicle to be improved. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 is a schematic perspective view of a vehicle according to an example of the invention; FIG. 2a is a schematic top cross-sectional view of a vehicle according to an example of the invention; FIG. 2b is a schematic side view of a vehicle according to an example of the invention; FIG. 3 is a schematic rear perspective view of a vehicle illustrating a rear ring vortex of a vehicle wake; FIG. 4 is a schematic cross-sectional view of a wheel of the vehicle according to an example of the invention; FIG. 5 is a pressure plot depicting an example pressure variation over a portion of a rear surface of a body of the vehicle. DETAILED DESCRIPTION A vehicle 1 in accordance with an embodiment of the present invention is described herein with reference to the accompanying Figures 1,2 and 3. In some, but not necessarily all examples, the vehicle 1 is a passenger vehicle, also referred to as a passenger car or as an automobile. In other examples, embodiments of the invention can be implemented for other applications, such as commercial vehicles. The vehicle 1 comprises one or more vehicle structures 12 which may collectively be referred to as a vehicle body, e.g. body in white, ora portion of the body in white. The vehicle body 12 may comprise the vehicle structures coupled together, for example using welding and / or riveting. In particular, the vehicle structures 12 may comprise one or more front body panels 12a forming a front surface 14 of the vehicle and one or more rear body panels 12b forming a rear surface 16 of the vehicle. The front of the vehicle 1 may be defined by the usual intended direction of travel of the vehicle 1 in normal, e.g. non-reversing, operation. A longitudinal direction of the vehicle X may be defined as extending between the front and rear of the vehicle. A lateral direction Y of the vehicle may be defined as the direction perpendicular to the longitudinal direction of the vehicle X and a vertical direction Z, e.g. when the vehicle is standing on a horizontal ground surface 300. The vehicle body 12 may further comprise side body panels, e.g. left and right side body panels 12a, 12d, forming lateral side surfaces, e.g. left and right lateral side surfaces 18, 20, of the vehicle body. As illustrated, the lateral side surfaces 18, 20 of the vehicle body may be substantially parallel with the longitudinal direction X of the vehicle. In particular, portions of the lateral side surfaces 18, 20 of the vehicle body between front and rear road wheels 106a, 106b, 106c, 106d of the vehicle, described in greater detail below, may be substantially parallel with the longitudinal direction X. The vehicle body may further comprise a roof panel 12e forming a roof, or upper surface 22 of the vehicle body. In other arrangements, one or more of the body panels mentioned above may be combined as integral components. For example, one or more of the side body panels may be integral with one or more of the front and / or rear body panels. Further, in other arrangements, the vehicle 1 may comprise any other combination of structures 12, e.g. body panels and / or other structures, forming the front surface 14, rear surface 16, lateral side surfaces 18, 20 and roof surface 22 of the vehicle body. The front surface 14 of the vehicle body defines a front extent of the vehicle, e.g. a forward most point, line or plane of the vehicle in the longitudinal direction X of the vehicle. The rear surface 16 of the vehicle body defines a rear extent of the vehicle, e.g. a rearward most point, line or plane of the vehicle in the longitudinal direction X of the vehicle. Similarly, the lateral side surfaces, e.g. the left and right lateral side surfaces 18, 20, may form lateral extents of the vehicle in either lateral direction, e.g. laterally outwards most points, lines or planes in either lateral direction Y relative to a longitudinally extending centreline of the vehicle. Although in the example depicted in Figure 1, the vehicle 1 comprises wing mirrors 2, which protrude laterally outward from the vehicle body, e.g. relative to the lateral side surfaces 18, 20, for the purposes of the present specification, the lateral extents of the vehicle may not be defined by the wing mirrors. In other words, the lateral extents of the vehicle may be defined ignoring, or not including, the wing mirrors 2. The roof surface 22 may form an upper extent of the vehicle, e.g. an upper most point, line or plane of the vehicle, from a ground surface 300 on which the vehicle is standing, in the vertical direction Z. The vehicle 1 may comprise a vehicle cabin 8 in which vehicle occupants may sit. For example, one or more seats 4 may be provided within the vehicle cabin 8 to support a passenger and / or an operator, e.g. driver, of the vehicle 1. The vehicle cabin 8 may be an interior space of the vehicle, and may be at least partially defined by the vehicle structure 12. The vehicle cabin 8 may be positioned towards the front of the vehicle 1, and may extend across substantially the full width of the vehicle 1. The vehicle 1 may further comprise an under bonnet space 10, which may comprise an interior space defined by the vehicle body 12 forward of the vehicle cabin 8. The under bonnet space 10 may be closed, e.g. at an upper extent of the under bonnet space, by a bonnet panel 11 of the vehicle body 12. The under bonnet space 10 may be configured to house components of one or more system of the vehicle, such as components of the drive system 100, described below. The vehicle 1, e.g. the vehicle body 12, may comprise a front bulkhead 9, which may be arranged to separate the under bonnet space 10 from the vehicle cabin 8. Referring now, in particular, to Figure 2, the vehicle 1 may comprise a drive system 100, which may be referred to as a powertrain of the vehicle. The drive system 100 may comprise one or more electric motors 102 and one or more batteries 104, e.g. traction batteries, for supplying power to the electric motors 102. The electric motors 102 may be drivingly coupled to one or more wheels, e.g. front road wheels 106a, 106b of the vehicle via one or more, e.g. respective, driveshafts 108a,108b to enable the electric motors to supply drive torque to the road wheels. The electric motors 102, or other electric motors of the drive system 100, may be configured to selectively receive drive torque from the road wheels 106a, 106b via the drive shafts 108a, 108b and charge the batteries 104, e.g. when the vehicle is decelerating. In other words, the electric motors 102, or other electric motors of the drive system 100, may be configured to perform regenerative braking of the vehicle. The drive system 100 may further comprise one or more battery controllers 103 and / or power electronics 105, for controlling charging and discharging of the one or more batteries, e.g. as electrical power is supplied to and optionally received from the electric motors, and / or is received via a charging plug provided on the vehicle for connecting the vehicle to an external electrical power supply to charge the traction batteries 104. In the arrangement illustrated, rear road wheels 106c, 106d are not configured to be driven by, or selectively drive, the one or more electric motors 102. However, in other arrangements, the rear road wheels 106c, 106d may be operatively coupled to the one or more electric motors provided on the vehicle, e.g. via driveshafts 108c,108d so that the rear road wheels can be driven by the one or more electric motors and the one or more electric motors can receive drive torque from the road wheels 106a, 106b via the drive shafts 108a, 108b and charge the batteries 104. The rear road wheels 106c, 106d may be configured to be driven by, or selectively drive, the one or more electric motors 102 in addition or as an alternative to the front road wheels 106a, 106b. When the front and rear road wheels are operatively coupled to the one or more electric motors 102 provided on the vehicle, the rear road wheels may be coupled to the same or different electric motor(s) from the front road wheels. The wheels of the vehicle, e.g. the front and rear road wheels 106a, 106b, 106c, 106d, may be arranged within wheel wells 13 of the vehicle. The wheel wells 13 may comprise recesses formed in the vehicle body by the one or more side panels 12c, 12d. The wheels of the vehicle may thereby be at least partially recessed into the lateral side surfaces of the vehicle on either lateral side of the vehicle. The front and / or rear road wheels may protrude laterally outwards relative to the left and right side surfaces of the vehicle. However, as illustrated in Figure 2, a trailing edge 12f of the wheel well, e.g. at which the wheel well 13 meet the lateral side surfaces of the vehicle rearwards of the wheel, such as the rear road wheels 106c, 106d, may protrude outwardly relative to the corresponding wheel, or may be substantially aligned with an outer side pf the corresponding wheel in the lateral direction Y of the vehicle. The wheels, e.g. the rear road wheels 106c, 106d, may protrude outwardly relative to leading edge 12g of the wheel well, e.g. at which the wheel well 13 meets the lateral side surface of the vehicle forwards of the wheel, or may be recessed relative to the leading edge 12g. In the arrangement depicted, the vehicle 1 comprises four traction batteries 104 and a single electric motor 102 configured to provide drive torque to the left and right front road wheels 106a, 106b via respective drive shafts 108a, 108b. However, in other arrangements, the drive system 100 may comprise any other number of traction batteries and / or any other number of electric motors. For example, the drive system 100 may comprise an electric motor associated with each of the road wheels provided on the vehicle 1. Further, in the arrangement depicted, the vehicle 1 is an electric vehicle, e.g. a full electric vehicle, such as a battery electric vehicle. However in other arrangements, the vehicle may be a hybrid vehicle, such as a mild-hybrid, plug-in hybrid vehicle, or range extender electric vehicle, and the drive system 100 may further comprise an Internal Combustion Engine (ICE) drivingly couplable to the road wheels of the vehicle for providing drive to the wheels in addition, or as an alternative, to the one or more electric motors 102. In further arrangements, the electric motors and battery may be omitted, and the drive system may comprise the ICE only for providing drive to the road wheels 106a, 106b. In arrangements in which the drive system 100 comprises the ICE, the vehicle may further comprise a fuel tank for storing fuel to be combusted within the engine. As illustrated in Figures 1 and 2, components of the drive system 100, and in particular one or more of the batteries 104, and / or one or more of the battery controllers 103 and / or components of the power electronics 105, may be housed within the under bonnet space 10 of the vehicle, e.g. forward of the front bulkhead 9. In particular, the components of the drive system 100 may be housed within a portion 10a of the under bonnet space arranged between, e.g. longitudinally between, the front road wheels 106a, 106b, or a central axis Af of the drive shafts 108a, 108b of the front road wheels, and the front bulkhead 9. The central axis Af of the drive shafts 108a, 108b of the front road wheels may be referred to as the centreline of the front road wheels. Housing the one or more components of the drive system 100 within the under bonnet space 10, e.g. in the portion 10a, may be beneficial compared to previous arrangements in which the components of the drive system are housed in the vehicle rearward of the front bulkhead 9, such as in a space beneath a foot-well of a rear seat of the vehicle; beneath the rear seat; or in a ‘tunnel’ area formerly used to house the prop-shaft and exhaust routings on front-engine ICE vehicles. This may create the packaging space to move the rear seats, and therefore the rear occupant sitting position, downwards in the vertical direction Z, without adversely affecting their posture or comfort. Therefore, with reference to Figure 3, housing the one or more components of the drive system 100 forward of the front bulkhead may enable an overall height dimension DH of the vehicle, defined between the ground surface 300 on which the vehicle is standing and the upper extent of the vehicle, to be reduced. Reducing the overall height of the vehicle may improve weight distribution, overall vehicle aerodynamics, as described in greater detail below, which may be achieved whilst maintaining occupant comfort. In order to provide increased space between the front road wheels 106a, 106b, or the centreline Af of the front road wheels, and the front bulkhead 9 to house the components of the drive system, an axial length of the vehicle between the front bulkhead and front road wheels 106a, 106b, or the centreline of the front road wheels may be increased. A front overhang (FOH) dimension Dfoh of the vehicle may be defined as a dimension, in the longitudinal direction of the vehicle, between the centreline of the front road wheels and the front extent of the vehicle. In orderto maintain a desired overall length of the vehicle, e.g. defined between the front and rear extents of the vehicle, the FOH dimension of the vehicle may be reduced when increasing the axial length of the vehicle between the front bulkhead 9 and front road wheels 106a, 106b, or the centreline of the front road wheels. Additionally or alternatively, in orderto provide increased space for housing the components of the drive system within the portion 10a of the under bonnet space, a width of the vehicle, e.g. between the left and right lateral extents, may be increased. In order to provide a desirable packaging space for the components of the drive system within the portion 10a of the under bonnet space, the vehicle 1 according to the present disclosure has a ratio of FOH to width that is less than 0.48, such as less than or equal to 0.44. A low FOH to vehicle width ratio may be typically associated with higher aerodynamic drag. However, a height dimension Dh of the vehicle may be, such that an overall height to overall length ratio of the vehicle, e.g. defined as a ratio of a height of the roof surface above a ground surface to the distance between the front and rear extents of the vehicle in the longitudinal direction X is less than 0.28, such as less than or equal to 0.27. The vehicle 1 thereby provides for improved vehicle component packaging, e.g. for components of the drive system 100 of the vehicle, whilst improving aerodynamic performance of the vehicle, e.g. by reducing aerodynamic drag. The lower FOH to width ratio of a vehicle may be associated with higher aerodynamic drag when the vehicle is travelling in a forward direction, due to air passing around front corners of the vehicle between the front surface 14 of the vehicle and the lateral side surfaces 18, 20 of the vehicle over a shorter longitudinal distance. Additionally or alternatively, air flow passing over each lateral side surface of the vehicle, e.g. from the front of the vehicle towards the rear of the vehicle, may reach the front wheels 106a, 106b and associated wheel wells 13 formed in the lateral side surfaces after passing a shorter distance over the respective lateral side surfaces 18, 20 of the vehicle. In combination, these factors may lead to increased size of a region of separated flow created due to the air passing over the front wheels towards the rear of the vehicle. In other words, a dimension, e.g. in the lateral direction Y of the vehicle, of a turbulent flow region downstream of the front wheels may typically be greater when the FOH dimension Dfoh and / or FOH to width ratio of the vehicle is lower, and / or vehicle width is higher. Furthermore, the turbulent flow region may extend further downstream of the front wheels towards the rear wheels of the vehicle. Interaction between the turbulent flow region downstream of the front wheels with the rear wheels may further contribute to pressure losses and lack of pressure recovery at the rear surface 16 of the vehicle body. The vehicle 1 may have a wheelbase dimension Dwb, commonly referred to as the vehicle wheelbase, defined as a distance between the front wheel centreline Af and the rear wheel centreline Ar in the longitudinal direction X of the vehicle. When the FOH to width ratio of the vehicle is low, particularly, when the FOH to width ratio of the vehicle is less than 0.48, such as less than or equal to 0.44, arranging front and rear road wheels of the vehicle such that the wheelbase Dwb of the vehicle is greater than or equal to 3 metres, such as greater than or equal to 3.2 meters may provide sufficient distance between the front road wheels and the rear road wheels in the longitudinal direction X to allow turbulent flow structures in the air flow passing over the lateral side surfaces between the front and rear road wheels to dissipate sufficiently, such that the effect of flow separation caused by the front and rear wheels does not combine to provide a undesirably detrimental effect on vehicle drag, such as form / pressure drag applied at the rear surface 16 of the vehicle. A rear overhang (ROH) dimension Droh of the vehicle may be defined as a dimension, in the longitudinal direction X of the vehicle, between the central axis Ar of drive shafts 108c, 108d of the rear road wheels, e.g. the centreline of the rear wheels, and the rear extent of the vehicle. A large ROH of a vehicle may typically be associated with reduced vehicle drag. There are several mechanisms specific to vehicle aerodynamics that this may exploit. For example a large ROH may mitigate pressure losses and unsteadiness that the rear wheels have on the wake of the vehicle. Additionally or alternatively, having greater ROH may allow improved base pressure recovery (e.g. pressure acting onto the rear surface 16 from the vehicle’s wake) by moving a rear ring vortex 300 (illustrated in Figure 3) further from the body, e.g. the rear surface 16. Additionally or alternatively again, a longer ROH may allow a more favourable pressure gradient to control the boundary layer over the surfaces, e.g. the lateral side surfaces 18, 20, that go on to form the rear corner edges 16a, 16b (described below), this boundary layer may detach from the car at the rear surface 16 and form shear layers that further affect the drag of the vehicle. Minimizing the unsteadiness of these shear layers may provide for a stable wake, which may be associated with a low vehicle drag. A smaller ratio of the FOH of the vehicle to the ROH of the vehicle may therefore enable vehicle drag to be reduced for a particular overall vehicle length and FOH value. The vehicle 1 may have a ratio of FOH to ROH that is less than 0.82, e.g. less than 0.8 or less than or equal to 0.76. Referring again to Figure 2 in particular, in order to encourage reattachment of the air flow to the lateral side surfaces of the vehicle and / orto reduce flow separation during expansion of the airflow between the rear wheels 106v, 106d and the rear surface 16 of the vehicle body, rear portions of the lateral side surfaces of the vehicle body downstream of the rear wheels may be angled towards the longitudinal centreline of the vehicle at an angle a of less than 28 degrees, such as less than or equal to 23 degrees, relative to the longitudinal direction X of the vehicle. The angle a of the rear portions of the lateral side surfaces relative to the longitudinal direction X may vary along the length of the lateral side surfaces. The change in angle and / or curvature of the rear portion of the lateral side surfaces may be sufficiently low so as not to cause premature flow separation along the lateral side surfaces, e.g. upstream of the rear corner edges 16a, 16b (described below). The lateral side surfaces of the vehicle 18, 20, or rear portions thereof, may be substantially parallel with a vertical direction Z or may be angled relative to the vertical direction. Further, an angle of the lateral side surfaces of the vehicle relative to the vertical direction Z may vary along the length, e.g. longitudinal length, of the lateral side surface and / or over their vertical heights. The rear taper of the lateral side surfaces, angle a, also known as boat-tailing may begin ahead, e.g. forwards, of the rear wheel centrelines. In other words, the rear portion of the lateral side surfaces, which form the rear taper, may extend forwards of the rear wheel centrelines. The rear taper may affect the formation, size and strength of the vortices that bound the edges of the rear surface 16 of the vehicle and the pressure loss in the immediate vicinity of the rear of the vehicle. A desirable taper angle, which achieves a desirable effect on pressure loss, may be specific to each particular vehicle, but in general terms the desirable taper angle may balance the flow attachment over the rear of the vehicle and the relative position and pressure loss of each of the arms 301, 302, 303a, 303b of the rear ring vortex 300, shown in Fig 3, acting on the rear surface 16. The side vertical arms 303a, 303b of the rear ring vortex may be lower pressure and stronger than the upper and lower lateral arms 301, 302, so drag benefit can be achieved with attenuation of these flow features. The vehicle body 12 comprises rear corner edges 16a, 16b between the respective lateral side surfaces 18, 20 of the vehicle and the rear surface 16. Air flowing around the rear corner edges 16a, 16b may separate causing a region of turbulent flow downstream of the rear corner edges. A size of the turbulent flow regions downstream of the rear corner edges may affect air pressure over the rear surface 16 of the vehicle body, thereby influencing a magnitude of form / pressure drag on the vehicle. As illustrated, particularly in Figure 3, the rear corner edges 16a, 16b are substantially vertical and extend vertically over substantially the full height of the lateral side surfaces of the vehicle. In this way, a size of turbulent flow regions downstream of the rear corner edges may be reduced compared to differently configured rear corner edges. The rear corner edges 16a, 16b may be sharp corners, e.g. having a corner radius less than 15mm, for example, less than or equal to 10mm, such as approximately 3mm or greater. Additionally or alternatively, an obtuse, e.g. exterior, angle formed between the lateral side surfaces 18, 20 and the rear surface 16 of the vehicle body at the rear corner edges 16a, 16b may be greaterthan or equal to 195 degrees, such as approximately 205 degrees. The sharp, vertical, rear corner edges 16a, 16b may create well defined separation edges, which may improve consistency in where the air flow separates from the vehicle body, thereby reducing lateral unsteadiness in the shear layer that would otherwise happen from a highly curved surface on which a point at which the flow separates, e.g. a separation point, would vary in time. Also, the separation point being substantially constant in the X and Y directions of the vehicle may reduce unsteadiness created by cross-flow velocity gradients. In some arrangements, the configuration of the rear corner edges 16a, 16b, as detailed above, may combine beneficially with the increased ROH of the vehicle to reduce turbulent fluctuations that encapsulate the outer wake of the body. Referring now to Figure 4 in addition to Figure 3, in order to reduce flow separation caused in the flow passing over the front and / or rear wheels of the vehicle and / or to reduce the size of one or more regions of turbulent flow caused by the presence of the front and rear wheels in the flow path of flow over the lateral side surfaces, the wheels of the vehicle 1, e.g. the front and / or rear wheels 106a, 106b, 106c, 106d may comprise the wheel 400. The wheel 400 comprises a hub portion 410. The hub portion 410 may be a substantially central portion of the wheel, e.g. relative to a radial direction of the wheel. The hub portion 410 may be configured to facilitate coupling of the wheel 400 to a hub assembly of the vehicle. For example, the hub portion 410 may comprise a plurality of fastener openings for fasteners, or studding portions of the hub assembly, to pass though in order to couple the wheel 400 to the hub assembly. The hub portion 410 may be any desirable shape in order to facilitate coupling of the wheel to the hub assembly. In particular, the hub portion 410 may be generally circular in a cross-section taken perpendicular an axial direction of the wheel 400. The wheel 400 further comprises a rim portion 420 disposed about the hub portion. The rim portion is for supporting a tyre 450 on the wheel. The wheel 400 further comprises a plurality of spoke portions 430 extending between, e.g. radially between, the hub portion 410 and the rim portion 420, in order to support the rim portion 420 about the hub portion 410. The spoke portions 430 may have any desirable shape and may comprise, for example, solid beams or rods extending in radially between the hub portion and the rim portion. The spoke portion 430 may have a substantially constant cross-sectional shape in planes perpendicular to the radial direction of the wheel along the spoke portions 430. Alternatively, the cross-sectional shape of the spoke portions may vary along the length of the spoke portions between the hub portion and the rim portion. Flow separation and the formation of turbulent flow structures as the air flow passes over the wheels may be affected by airflow through the wheel into and out of the wheels well 13, e.g. in the axial directions of the wheels. The air flow through the wheels in the axial direction may be through open areas of the wheels formed between the rim portion and the hub portion of the wheel (in the radial direction of the wheel). The open areas through the wheels may be formed between, e.g. circumferentially between, the spoke portions of the wheels. In order to reduce the size of the separated flow region and the size of turbulent flow structures formed the wheels 400 of the vehicle 1, e.g. the front and rear road wheels 106a, 106b, 106c, 106d may have open areas which are less than 20% or less than 15% of a total area of the wheels between the rim portion and the hub portion. Further, as shown in Figure 4, in order reduce flow separation and the size of turbulent flow structures formed the wheels 400 of the vehicle 1 a maximum dimension of the wheels between the rim portion 420, e.g. a outside edge of the rim portion, and a centre point of the road wheel Dyr may be less than or equal to 6mm in a lateral direction Y of the vehicle. Additionally or alternatively, a maximum dimension from the rim portion 420, e.g. the outside edge of the rim portion, to a side-wall 452 of the tyre 450 mounted on the rim portion Dyt may less than 10mm in a lateral direction Y of the vehicle. Further, a side-wall height Dswh, e.g. a length of the side-wall 452 of the type in the radial direction of the wheel may be greater than 110mm. Each of these factors may individually, and in combination, reduce flow separation and / or encourage flow reattachment downstream of the wheel, and thereby reduce the size of turbulent flow structures formed downstream of the wheels. In particular, these factors may help to maintain flow attachment on a rearward outer face of the sidewall of the rear tyre, which may direct an angle of flow separation more towards the streamwise direction, and promote reattachment or earlier reattachment (i.e. at a point more upstream) on the lateral side surface, which may improve the ability of the features, as described above, to reduce vehicle drag. Figure 5 is a diagram illustrating pressure contours of a pressure distribution 500, e.g. a time-averaged static pressure distribution, over a portion of the rear surface 16 of the vehicle body. As illustrated, the pressure distribution comprises a first region 502, which may be located substantially centrally on the rear surface 16 of the vehicle body or portion thereof. In the first region 502, a pressure e.g. static pressure, of air may be at a maximum. The pressure distribution may further comprise second, third, fourth, fifth, sixth and seventh regions 504, 506, 508, 510, 512, 514 arranged in increasing outward positions relative to the first region 502. In the second, third, fourth, fifth, sixth and seventh regions 504, 506, 508, 510, 512, 514 the air pressure is sequentially reduced compared to in the first region 502. However, the air pressure within the second, third, fourth, fifth, sixth and seventh regions may remain above the free-stream, e.g. atmospheric pressure. The pressure distribution may further comprise eight, ninth, tenth, eleventh and twelfth regions 516, 518, 520, 522, 524 arranged in increasing outward positions relative to the seventh region 514. The air pressure within the eighth, ninth, tenth, eleventh and twelfth regions 516, 518, 520, 522, 524 is sequentially reduced compared to in the seventh region 514. Further, in the eighth, ninth, tenth, eleventh and twelfth regions 516, 518, 520, 522, 524, air pressure may be less than the free-stream, e.g. atmospheric pressure. Due to the measures described above for reducing flow separation and the formation of turbulent flow structures as the airflows over the roof surface and / or the lateral side surfaces between the front and rear surfaces of the vehicle, the regions of the pressure distribution 500 may be such that an average air pressure applied over the rear surface 16 of the vehicle body is positive, e.g. relative to the free-stream / atmospheric pressure, and vehicle drag may therefore be reduced. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

1. A vehicle comprising:a body having a front surface forming a front extent of the vehicle and a rear surface forming a rear extent of the vehicle;a front road wheel having a front wheel centreline; anda rear road wheel having a rear wheel centreline, wherein a front overhang to width ratio of the vehicle, defined as a ratio of a distance between the front wheel centreline and the front extent of the vehicle to the width of the body, is less than 0.48, and wherein a rear overhang is defined as a distance between the rear wheel centreline and the rear extent of the vehicle, wherein a ratio of the front overhang relative to the rear overhang is less than 0.82.

2. The vehicle of claim 1, wherein the body comprises a roof surface defining an upper extent of the vehicle, and wherein a height to length ratio of the vehicle, defined as a ratio of a height of the roof surface above a ground surface to the distance between the front and rear extents of the vehicle is less than 0.28.

3. The vehicle of claim 1 or 2, wherein a wheelbase of the vehicle, defined as a distance between the frontwheel centreline and the rear wheel centreline in the longitudinal direction of the vehicle is greater than or equal to 3m.

4. The vehicle of any of the preceding claims, wherein the vehicle is an electric vehicle.

5. The vehicle of claim 4, wherein the vehicle further comprises a front bulkhead arranged between anunder bonnet space of the vehicle and an interior cabin of the vehicle, and wherein a traction battery, and / or a traction battery controller and / or associated power electronics for controlling charging and discharging of the traction battery, are arranged between the front wheel centreline and the front bulkhead.

6. The vehicle of any of the preceding claims, wherein a maximum dimension of the front and / or rear road wheel between a rim portion of the road wheel and a centre point of the road wheel is less than or equal to 6mm in a lateral direction of the vehicle.

7. The vehicle of any of the preceding claims, wherein an open area of the front and / or rear road wheel, between a rim portion of the wheel and a hub portion of the wheel, for air flow though the road wheel in an axial direction of the road wheel is less than 15% of a total area of the road wheel between the rim portion and the hub portion.

8. The vehicle of any of the preceding claims, wherein the front and / or rear road wheel comprises a tyre mounted on a rim portion of the front and / or rear road wheel, wherein a side-wall height of the tyre is greaterthan 110mm.

9. The vehicle of any of the preceding claims, wherein the front and / or rear road wheel mounted on a rim portion of the front and / or rear road wheel, wherein a maximum dimension from the rim portion to a side-wall of the tyre mounted on the rim portion is less than 10mm in a lateral direction of the vehicle.

10. The vehicle of any of the preceding claims, wherein the vehicle body comprises a side surface forming a lateral extent of the vehicle, wherein an angle of a portion of the side surface between the rear road wheel and rear surface is less than or equal to 28 degrees, relative to a longitudinal direction of the vehicle.

511. The vehicle of any of the preceding claims, wherein the body comprises a rear corner edge between a side surface of the vehicle and the rear surface, wherein the rear corner edge is substantially vertical and extends vertically over substantially the full height of the side surface.10 12. The vehicle of any of the preceding claims, wherein the width of the vehicle is greater than 1.99m.

13. The vehicle of any of the preceding claims, wherein the front overhang of the vehicle is less than 0.9m.15A

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