SPECIFICATION AERODYNAMIC STRUCTURE FOR VEHICLE Technical Field [0001] The present invention relates to an aerodynamic structure for a vehicle for adjusting airflow within a wheel house. Background Technology [0002] There is known an aerodynamic stabilizer that is structured by fixing a baffle to the front side or the vehicle width direction inner side of a wheel within a wheel house of an automobile (see, for example, Japanese National Publication No. 2003-528772). Further, the technology disclosed in the specification of British Patent Application Publication No. 2265785 is known. Disclosure of the Invention Problems to be Solved by the Invention [0003] However, in the conventional technique as described above, because the baffle projects-out from the wheel house, there are various limitations such as avoiding interference with the wheel and the like, and it is difficult to obtain a sufficient airflow adjusting effect. [0004] In view of the above-described circumstances, an object of the present invention is to provide an aerodynamic structure for a vehicle that can effectively adjust airflow within a wheel house. Means for Solving the Problems [0005] In an aerodynamic structure for a vehicle relating to a first aspect of the present invention, an airflow collision wall that extends in a vehicle width direction and faces toward a lower side in a vehicle body vertical direction, a lower wall that extends downwardly in the vehicle body vertical direction from a rear end portion in a vehicle body longitudinal direction of the airflow collision wall, and an upper wall that extends upwardly in the vehicle body vertical direction from a front end portion in the vehicle body longitudinal direction of the airflow collision wall, are provided further toward a rear side in the vehicle body longitudinal direction than a rotational axial center of a wheel within a wheel house, and a projecting height, in the vehicle body longitudinal direction and with respect to a corner portion formed by the airflow collision wall and the lower wall, at at least one portion in the vehicle width direction of a corner portion formed by the airflow collision wall and the upper wall is gradually changed along the vehicle width direction. [0006] In accordance with this aspect, accompanying rotation of the wheel, airflow from the
I
rear of the wheel into the wheel house arises. A portion of this airflow collides with the airflow collision wall. Due thereto, the pressure around s concave (groove) portion formed by the airflow collision wall and the lower wall rises, and flowing-in of air to the wheel house is suppressed. Further, because the airflow collision wall is positioned further rearward than the rotational center of the wheel, flowing-in of air to the wheel house accompanying rotation of the wheel is suppressed at the upstream (entrance) side, and discharging of air, that has flowed-into the wheel house, from the side is suppressed. [0007] Further, in an aerodynamic structure for a vehicle having the airflow collision wall as described above, the corner portion of the airflow collision wall and the upper wall is a convex portion that is convex toward the wheel side, and it is easy for stones and the like, that are scattered-up by the wheel that rotates, to collide therewith. However, in the present aerodynamic structure for a vehicle, because the projecting height of the convex portion is gradually changed along the vehicle width direction, injury (damage) due to the aforementioned stones and the like can be mitigated. Namely, at the portion whose projecting height is low for example, there can be made to be a structure in which the strength with respect to collision of the aforementioned stones or the like is increased or the probability of collision with stones or the like is decreased. [0008] In this way, in the present aerodynamic structure for a vehicle, airflow within a wheel house can be adjusted effectively. [0009] In the aerodynamic structure for a vehicle of the above-described aspect, the airflow collision wall, the wheel house is formed such that a vehicle width direction inner side portion is positioned further toward a rear side in the vehicle body longitudinal direction than a vehicle width direction outer side portion, and at the at least one portion in the vehicle width direction including a vehicle width direction inner end of the corner portion formed by the airflow collision wall and the upper wall, the projecting height is gradually changed so as to become smaller the further toward an inner side in the vehicle width direction. [0010] In accordance with this aspect, in light of the relationship with the envelope of the wheel for example, the inner side portion of the wheel house is positioned further toward the rear side in the vehicle body longitudinal direction than the vehicle width direction outer side portion. Therefore, even in cases in which, usually, a peak portion is formed by an airflow collision wall and an upper wall (and the inner side wall that covers the corner portions thereof from the vehicle width direction inner side) at the vehicle width direction inner end of the wheel house, in the present aerodynamic structure for a vehicle, this peak portion is no longer formed or the projecting height of the peak portion is low, and therefore, injury 2 (damage) to the peak portion can be mitigated. [0011] In the aerodynamic structure for a vehicle of the above-described aspect, at the at least one portion in the vehicle width direction, including a vehicle width direction inner end of the airflow collision wall, of the corner portion formed by the airflow collision wall and the upper wall, the projecting height is gradually changed so as to become smaller the further toward the inner side in the vehicle width direction by inclining a front end portion or a rear end portion in the vehicle body longitudinal direction with respect to the vehicle width direction. [0012] In accordance with this aspect, because the projecting height of the corner portion of the collision wall and the upper wall is gradually changed continuously, a corner portion (step portion) or the like is not formed along the way of the gradually changed structure. Effects of the Invention [0013] As described above, the aerodynamic structure for a vehicle relating to the present invention has the excellent effect of being able to effectively adjust airflow within a wheel house. Brief Description of the Drawings [0014] Fig. I is a perspective view showing, in an enlarged manner, a portion of an aerodynamic structure for a vehicle relating to an embodiment of the present invention. Fig. 2 is a side sectional view schematically showing the schematic overall structure of the aerodynamic structure for a vehicle relating to the embodiment of the present invention. Fig. 3 is a plan sectional view along line 3-3 of Fig. 1. Fig. 4 is a side sectional view showing, in an enlarged manner, a portion of the aerodynamic structure for a vehicle relating to the embodiment of the present invention. Fig. 5A is a perspective view of an automobile to which the aerodynamic structure for a vehicle relating to the embodiment of the present invention is applied. Fig. 5B is a perspective view of an automobile relating to a comparative example with the embodiment of the present invention. Fig. 6 is a plan sectional view corresponding to Fig. 3 and showing an aerodynamic structure for a vehicle relating to a first modified example of the embodiment of the present invention. Fig. 7 is a plan sectional view corresponding to Fig. 3 and showing an aerodynamic structure for a vehicle relating to a second modified example of the embodiment of the present invention. Fig. 8 is a perspective view showing an aerodynamic structure for a vehicle relating to a comparative example with the embodiment of the present invention. 3 Preferred Forms for Embodying the Invention [0015] An aerodynamic structure 10 for a vehicle relating to an embodiment of the present invention will be described on the basis of Fig. I through Fig. 5. Note that arrow FR, arrow UP, arrow IN and arrow OUT that are written appropriately in the respective drawings respectively indicate the forward direction (direction of advancing), the upward direction, the vehicle width direction inner side and the outer side of an automobile S to which the aerodynamic structure 10 for a vehicle is applied. Hereinafter, when merely the top, bottom front, back and the inner and outer sides in the vehicle width direction are indicated, they correspond to the directions of the aforementioned respective arrows. Further, in this embodiment, the aerodynamic structure 10 for a vehicle is applied respectively to left and right front wheels 15, rear wheels 16 that serve as wheels, but because the respective aerodynamic structures 10 for a vehicle are basically structured similarly (symmetrically in the case of the left and the right), hereinafter, mainly one of the left and right aerodynamic structures 10 for a vehicle for the front wheels will be described. [0016] A front portion of the automobile S to which the aerodynamic structure 10 for a vehicle is applied is shown in Fig. 2 in a schematic side sectional view seen from a vehicle width direction inner side. Further, the front portion of the automobile S is shown in Fig. 3 in a schematic plan sectional view. As shown in these drawings, the automobile S has a front fender panel 12 that structures the vehicle body thereof. A wheel arch 12A, that is formed in the shape of a substantially semicircular arc that opens downward in side view for allowing steering of the front wheel 15, is formed in the front fender panel 12. Although not illustrated, a fender apron is joined to the inner side of the front fender panel 12, and a wheel house inner is provided at the fender apron. Due thereto, a wheel house 14, that is disposed such that the front wheel 15 can steer, is formed at the front portion of the automobile S. [0017] Further, a fender liner 18, that, in side view is formed in a substantially circular arc shape that corresponds to the wheel arch 12A and has a slightly larger diameter than the wheel arch 12A and that, in plan view, is formed in a substantially rectangular shape that covers and hides the front wheel 15, is disposed at the inner side of the wheel house 14. Accordingly, the fender liner 18 is accommodated within the wheel house 14 so as to not be exposed from the wheel arch 12A in side view. The fender liner 18 covers the substantially upper half portion of the front wheel 15 from the front, above and the rear, and prevents mud, small stones, and the like from hitting the fender apron (the wheel house inner) and the like. The fender liner 18 is made of a resin formed by, for example, resin molding (injection molding or vacuum molding), or is a structure in which a nonwoven fabric is used as the substrate or as 4 the surface material. [0018] Further, the fender liner 18 structuring the aerodynamic structure 10 for a vehicle has concave portions (groove portions) 20 that open to the front wheel 15 side as seen in side view. In this embodiment, the concave portions 20 are provided at a portion of the fender liner 18 which portion is positioned at the rear side of the front wheel 15 (a portion that overlaps the front wheel 15 in the vehicle body vertical direction). More specifically, as shown in Fig. 2, the concave portions 20 are provided over a portion or the entirety within region A that is further rearward and downward than portion C that an imaginary straight line ILI, that forms an angle 0 (-a* <0 < 900) with a horizontal line HL that passes through a rotation axis RC of the front wheel 15, intersects among the portion of the fender liner 18 that is further rearward than the rotation axis RC of the front wheel 15. [0019] At the upper limit side of the range of setting the concave portions 20, it is preferable to make the angle 0 be less than or equal to 50* and more preferable to make the angle 0 less than or equal to 400, and in this embodiment, the angle 0 is around 30*. Further, an angle cc, that prescribes the lower limit side of the range of setting the concave portions 20, is an angle formed by an imaginary straight line IL2, that connects the rear lower end portion of the wheel house 14 from the rotation axis RC of the front wheel 15, and the horizontal line HL. The rear lower end portion of the wheel house 14 can be made to be, for example, the rear lower end of the fender liner 18. [0020] As shown in Fig. 1 and Fig. 2, the concave portion 20 opens toward the front wheel 15 side as described above, and forms a substantially triangular shape as seen in side view whose width along the peripheral direction of the fender liner 18 (the wheel house 14) becomes a maximum at the opening portion 20A. More specifically, the concave portion 20 is structured to have an airflow guiding wall 22, that extends substantially upward from a lower edge 20B of the opening portion 20A, and an airflow collision wall 24, that extends from a rear upper end 22A of the airflow guiding wall 22 toward an upper edge 20C of the opening portion 20A. [0021] The length of the side surface (the length of a side of the triangle) of the airflow collision wall 24 is made to be small with respect to the airflow guiding wall 22. Due thereto, as shown in Fig. 1, the airflow guiding wall 22 extends in a direction substantially along airflow F so as to guide the airflow F (the airflow substantially along a tangent direction of the front wheel 15), that arises accompanying rotation of the front wheel 15 (rotation in the direction of arrow R that is the direction of causing the automobile S to advance forward), to within the concave portion 20. On the other hand, the airflow collision wall 24 extends so as 5 to face the airflow F, and the airflow F that flows-into the concave portion 20 collides therewith. [0022] Due to the above, at the aerodynamic structure 10 for a vehicle, there is a structure in which a portion of the airflow F is blocked by the concave portion 20 and the pressure within the concave portion 20 rises, and accompanying this, the pressure between the opening portion 20A of the concave portion 20 and the front wheel 15 rises. Due to this rise in pressure, at the aerodynamic structure 10 for a vehicle, flowing-in of the airflow F into the wheel house 14 is suppressed. [0023] Further, as shown in Fig. 1 through 3, the plural (two in this embodiment) concave portions 20 are provided at the fender liner 18, so as to be parallel in the peripheral direction of the fender liner 18. In this embodiment, the lower edges 20B, the upper edges 20C of the opening portions 20A of the concave portions 20, that are adjacent in the peripheral direction of the fender liner 18, substantially coincide. Namely, the plural concave portions 20 are formed so as to form indentations and protrusions (wave shapes), that are triangular in sectional view, continuously in the peripheral direction of the fender liner 18. Of the plural concave portions 20, the concave portion 20 that is positioned the furthest rearward and downward is positioned at a rear lower end portion 18A of the fender liner 18. [0024] Accordingly, in this embodiment, with respect to the airflow collision wall 24 that structures the concave portion 20 that is positioned the furthest rearward and downward, the airflow guiding wall 22 of that concave portion 20 that is positioned furthest rearward and downward corresponds to the lower wall of the present invention, and the airflow guiding wall 22 of the concave portion 20 at the upper side corresponds to the upper wall of the present invention. On the other hand, with respect to the airflow collision wall 24 that structures the concave portion 20 at the upper side, the airflow guiding wall 22 of that concave portion 20 that is at the upper side corresponds to the lower wall of the present invention, and a general wall portion 28, that forms a general surface of the fender liner 18 that is continuous with the front end (the upper edge 20C of the opening portion 20A) of that airflow collision wall 24, corresponds to the upper wall of the present invention. [0025] Further, as shown in Fig. I and Fig. 3, the respective concave portions 20 extend along the vehicle width direction, and the vehicle width direction outer ends thereof are sealed by a side wall 26. In this embodiment, the concave portions 20 are formed so as to overlap over the entire width in the vehicle width direction with respect to the front wheel 15 that is positioned at the neutral position (posture). [0026] On the other hand, the vehicle width direction inner ends of the respective concave 6 portions 20 are made to be open ends that are open inwardly in the vehicle width direction. As shown in Fig. 3, in light of the relationship with a tire envelope Et, an inner end 18B in the vehicle width direction of the fender liner 18 (the wheel house 14) is positioned at the rear side in the vehicle body longitudinal direction with respect to an outer end 18C. The tire envelope Et shows the locus of the most outer side (side near the vehicle body) among the loci of the entire relative displacements with respect to the vehicle body including the steering and bouncing of the front wheel 15. In a vicinity of the vehicle width direction inner end of the fender liner 18, this tire envelope Et has a peak Ep at the most rear side in the vehicle body longitudinal direction. Therefore, as shown in Fig. 3, the inner surface of the rear portion of the fender liner 18 is inclined with respect to the vehicle width direction (refer to reference line W), so that the inner end 18B in the vehicle width direction is positioned at the rear side in the vehicle body longitudinal direction with respect to the outer end 18C. [0027] Further, at the aerodynamic structure 10 for a vehicle, a distance (projecting height H shown in Fig. 4) between a concave side ridgeline Rr, that is a corner portion between the airflow collision wall 24 (lower wall) and the airflow guiding wall 22 that structure the same concave portion 20, and a convex side ridgeline Rf, that is a corner portion between the airflow collision wall 24 and the airflow guiding wall 22 (upper wall) of the upper side concave portion 20 or the general wall portion 28, is gradually changed along the vehicle width direction as shown in Fig. 1 and Fig. 3. Concrete description is given hereinafter. [0028] As shown in Fig. 3, at the aerodynamic structure 10 for a vehicle, the concave side ridgeline Rr is formed substantially along the vehicle width direction (the reference line W), and the convex side ridgeline Rf (the upper edge 20C) is inclined with respect to the vehicle width direction (the reference line W) such that a vehicle width direction inner end Rfi is positioned at the rear side in the vehicle body longitudinal direction with respect to a vehicle width direction outer end Rfo. In this embodiment, the airflow collision wall 24 is formed in a substantially triangular shape as seen in plan view, so that the vehicle width direction inner end Rfi substantially coincides with the concave side ridgeline Rr. [0029] In this embodiment, the fender liner 18 has a flange 30 that faces the front wheel 15 side and forms a peripheral edge portion. A slight step (a step of less than or equal to 3 mm) B is formed between the flange 30 and the vehicle width direction inner end of the concave portion 20. The step B is formed in a direction in which the vehicle width direction inner end of the concave portion 20 projects-out toward the front wheel 15 side more than a portion of the flange 30 which portion is positioned further toward the vehicle width direction inner side than the concave portion 20. 7 [0030] Further, as shown in Fig. I and Fig. 2, the aerodynamic structure 10 for a vehicle is provided with guide grooves 34 that serve as peripheral direction grooves provided in the fender liner 18 so as to open toward the front wheel 15 side. Portions of the guide grooves 34 that are further toward the vehicle body longitudinal direction front side than the (concave portion 20 that is positioned the most upward and forward of the) concave portions 20 are proximal ends 34A, and the longitudinal directions of the guide grooves 34 are along the peripheral direction of the fender liner 18, and the portions of the guide grooves 34 that are in a vicinity of a front lower end portion 18D of the fender liner 18 are final ends 34B. The guide grooves 34 do not communicate with the concave portions 20. [0031] The groove floors of the guide grooves 34 at the proximal ends 34A and the final ends 34B are respectively tapered, and smoothly continue with the general wall portion 28 (the open surfaces of the concave portions 20 and the guide grooves 34) that forms the general surface of the fender liner 18, and the airflow along the peripheral direction of the concave portions 20 (the wheel house 14) smoothly enters therein and exits therefrom. As shown in Fig. 1, in this embodiment, the plural (two) guide grooves 34 that are parallel in the vehicle width direction are provided. These guide grooves 34 are structured so as to guide the airflow, that is directed from the rear toward the front along the inner periphery of the fender liner 18, so as to make the airflow flow-in from the proximal ends 34A and be discharged from the final ends 34B. In other words, a pair of walls 34C, that face the vehicle width direction at the respective guide grooves 34, are structured so as to prevent airflow directed in the vehicle width direction from arising. Note that the above shows an example in which two of the guide grooves 34 are provided, but merely one guide groove 34 may be provided or three or more may be provided. [0032] To supplement description of the aerodynamic structure 10 for a vehicle for the rear wheel 16, as shown in Fig. 5A, at the automobile S, the wheel house 14 is formed at the inner side of a wheel arch 36A of a rear fender panel 36, and the rear wheel 16 is disposed within the wheel house 14. The aerodynamic structure 10 for a vehicle for the rear wheel 16 is basically structured similarly to the aerodynamic structure 10 for a vehicle for the front wheel 15, except that the tire envelope Et of the rear wheel 16 that is not the steering wheel (or at which the steering angle is small) is different from the tire envelope Et of the front wheel 15 that is the steering wheel. Namely, the aerodynamic structure 10 for a vehicle for the rear wheel 16 is structured by forming the concave portions 20, the guide grooves 34 at a rear wheel house liner that covers the rear wheel 16 (in the following description, this liner will be called the fender liner 18, without being differentiated from that for the front wheel 15). 8 [0033] Further, as shown in Fig. 2 and Fig. 5A, the aerodynamic structures 10 for a vehicle are provided with spats 32 that extend in the vehicle width direction and are disposed respectively at the front sides of the front wheels 15 and the rear wheels 16. The spats 32 are structured so as to prevent traveling wind, that accompanies traveling of the automobile S, from flowing into the wheel houses 14. The aerodynamic structure 10 for a vehicle may be a structure that is not provided with the spats 32. [0034] Operation of the present embodiment will be described next. [0035] At the automobile S to which the aerodynamic structure 10 for a vehicle of the above-described structure is applied, when the front wheel 15 rotates in the direction of arrow R accompanying the traveling of the automobile S, airflow F, that is dragged in by this rotation of the front wheel 15 and flows-in substantially upward into the wheel house 14 from the rear of the front wheel 15, is generated. A portion of this airflow F is guided by the airflow guiding walls 22 and flows-into the concave portions 20, and collides with the airflow collision walls 24. Therefore, a portion of the airflow F is blocked, the pressure within the concave portions 20 rises, and the range of this rise in pressure extends to the space between the concave portions 20 and the front wheel 15. Due thereto, at the aerodynamic structure 10 for a vehicle, the flow-in resistance of air into the wheel house 14 from the rear of the front wheel 15 increases, and the flowing-in of air into that wheel house 14 is suppressed. [0036] Similarly, at the automobile S to which the aerodynamic structure 10 for a vehicle is applied, due to the rise in pressure around the concave portions 20 that arises due to a portion of the airflow being blocked by the airflow collision walls 24 due to rotation of the rear wheel 16, the flow-in resistance of air into the wheel house 14 increases, and the flowing-in of air into that wheel house 14 is suppressed. [0037] Further, another portion of the airflow F passes the setting region of the concave portions 20 and flows into the wheel house 14. At least a portion of the airflow F attempts to flow at the outer peripheral side due to centrifugal force and flows-into the guide grooves 34, and is guided by the guide grooves 34 and discharged from the final end 34B sides. [0038] In this way, in the aerodynamic structure 10 for a vehicle relating to the embodiment, because the concave portions 20 suppress flowing-in of air into the wheel house 14, the airflow F that attempts to flow into the wheel house 14 from beneath the floor of the automobile S is weak, and disturbance of the airflow at the periphery of the wheel house 14 is prevented (is adjusted). Concretely, as shown in Fig. 5A, airflow Ff beneath the floor is prevented from being disturbed, and the smooth airflow Ff is obtained beneath the floor. [0039] Further, the amount of air that flows into the wheel house 14 decreases, and the 9 amount of air that is discharged from the side of the wheel house 14 also decreases. In particular, because the concave portion 20 is disposed at a rear lower edge portion 14A that is the furthest upstream portion where the airflow F flows into the wheel house 14, in other words, because the airflow F is blocked at the furthest upstream portion, the amount of air that is discharged from the side of the wheel house 14 can be decreased further. For these reasons, at the automobile S, airflow Fs along the side surface is prevented from being disturbed, and the smooth airflow Fs is obtained at the side surface. [0040] Due to the above, at the automobile S to which the aerodynamic structure 10 for a vehicle is applied, a reduction in air resistance (the CD value), an improvement in driving stability, a reduction in wind noise, a reduction in splashing (water being scattered-up from the road surface by the front wheel 15, the rear wheel 16), and the like can be aimed for due to the operation of the concave portions 20. [0041] Further, at the aerodynamic structure 10 for a vehicle, because the guide grooves 34 are provided forward of the concave portions 20, the airflows at the inner side and at the side of the wheel house 14 are adjusted. Concretely, because the airflow F within the wheel house 14 flows along (parallel to) the direction of rotation of the front wheel 15, the rear wheel 16 due to the guide grooves 34, disturbance of the airflow within the wheel house 14 (the application of air force to the front wheel 15, the rear wheel 16) is prevented. Further, because discharging of air that has gone via the side of the wheel house 14, i.e., the wheel arch 12A, 36A, is suppressed, the smooth airflow Fs is obtained at the automobile S. [0042] Therefore, at the automobile S to which the aerodynamic structure 10 for a vehicle is applied, a reduction in air resistance, an improvement in the driving stability, a reduction in wind noise, a reduction in splashing, and the like can be aimed for also due to the operation of the guide grooves 34. Accordingly, at the automobile S in which the aerodynamic structures 10 for a vehicle are provided so as to correspond to the front wheels 15, the rear wheels 16 respectively, as shown in Fig. 5A, at both the front portion and the rear portion of the vehicle body, the smooth airflows Ff, Fs that do not have blowing-out that causes disturbance at the side surfaces and beneath the floor are obtained, and these flows merge smoothly at the rear of the vehicle body (refer to arrow Fj). [0043] To supplement explanation by comparison with a comparative example shown in Fig. 5B, at a comparative example 200 that is not provided with the aerodynamic structures 10 for a vehicle, the airflows F are generated within the wheel houses 14 accompanying the rotation of the front wheels 15, the rear wheels 16, and this flowing-in causes disturbance of the airflow Ff beneath the floor directly behind the front wheels 15, the rear wheels 16 (the 10 portions where the airflows into the wheel houses 14 are generated). Further, the airflows F that have flowed into the wheel houses 14 go via the wheel arches 12A and are discharged out to the sides of the vehicle body (refer to arrows Fi), and cause disturbance of the airflows Fs. For these reasons, disturbance is caused as well in Fj that merges at the rear of the vehicle body. [0044] In contrast, at the automobile S to which the aerodynamic structures 10 for a vehicle are applied, as described above, the flowing-in of air to the wheel houses 14 from the rear of the front wheels 15, the rear wheels 16 is suppressed by the concave portions 20, and the airflows that have flowed into the wheel houses 14 are adjusted at the guide grooves 34. Therefore, as described above, a reduction in air resistance, an improvement in the driving stability, a reduction in wind noise, a reduction in splashing, and the like can be realized. [0045] In particular, at the aerodynamic structures 10 for a vehicle, because the plural concave portions 20 are provided continuously, the flowing-in of air to the wheel houses 14 from the rear of the front wheels 15, the rear wheels 16 can be suppressed even more effectively. Namely, a sufficient airflow adjusting effect can be obtained by a compact structure that suppresses the amount of projection of the concave portions 20 toward the vehicle body inner portion side. Further, because the guide grooves 34 do not communicate with the concave portions 20, air does not flow from the concave portions 20 to the guide grooves 34 and the pressure of the concave portions 20 does not decrease, and the effect of suppressing the flowing-in of the airflows F to the wheel houses 14 and the effect of adjusting the airflows F that have flowed into the wheel houses 14 can both be established effectively. [0046] Further, at the aerodynamic structures 10 for a vehicle, because the concave portions 20 and the guide grooves 34 are positioned so as to be concave with respect to the general surface 28 of the fender liner 18, interference with the front wheel 15, the rear wheel 16 is not a problem. Accordingly, the concave portions 20, the guide grooves 34 can be designed on the basis of performances required from the standpoint of aerodynamics, without the dimensions and shapes or the arrangement and the like thereof being limited for preventing interference with the front wheel 15, the rear wheel 16. [0047] Further, at the aerodynamic structure 10 for a vehicle, because the projecting height H of the convex side ridgeline Rf with respect to the concave side ridgeline Rr is gradually reduced toward the vehicle width direction structure inner end, it is difficult to be damaged by flying stones or the like that are scattered-up by the front wheel 15, the rear wheel 16. This point will be described by comparison with a comparative example shown in Fig. 8. [0048] In an aerodynamic structure 100 for a vehicle relating to the comparative example 11 shown in Fig. 8, a fender liner 101 has concave portions 106 that are formed from airflow guiding walls 102 and airflow collision walls 104. A convex side ridgeline Rfc, that is the corner portion between the airflow collision wall 104 and the airflow guiding wall 102 of the upper side concave portion 106 or the general wall portion 28, extends substantially along the vehicle width direction (refer also to the imaginary line of Fig. 3). Further, in light of the relationship with the tire envelope Et, the fender liner 101 is a structure whose vehicle width direction inner end is positioned at the rear side in the vehicle body longitudinal direction with respect to the outer end. Therefore, for example, a side wall, that faces the side wall 26 and projects further forward than the convex side ridgeline Rfc, cannot be provided at the vehicle width direction inner end. Therefore, a peak portion P, that is formed from three surfaces that are the airflow collision wall 104, the airflow guiding wall 102 of the upper side concave portion 106 or the general wall portion 28, and the side wall that connects with the flange 30 (corresponding to the step B of the aerodynamic structure 10 for a vehicle), is formed at the aerodynamic structure 100 for a vehicle. It is easy for this peak portion P to be damaged by flying stones, sand, ice, or the like. [0049] For example, in a case in which the fender liner 18 is formed by vacuum molding of a resin, the peak portion P is easily formed as a thin-walled portion of the fender liner 18, and there is the concern that, if flying stones or the like collide, the formation of holes or the like will occur. Further, for example, in a case in which the fender liner 18 is formed by injection molding of a resin, the peak portion P can be formed to be thick-walled, but there is the concern that the surface will be whitened by scratches caused by flying stones and the appearance will deteriorate. Still further, for example, in a case in which the fender liner 18 is formed by using corrosion as the base material or as the surface material in order to obtain soundproofing performance, a deterioration in the appearance due to fluffing-up of the surface caused by flying stones or the like hitting the peak portion P, and a deterioration in the soundproofing performance due to holes being formed, are of concern. Moreover, for example, in cases in which the fender liner 18 is structured by a metal material or the concave portions 20 are formed in a sheet metal portion of the vehicle body instead of the fender liner 18, there is the concern that coatings (including anti-chip coating and anticorrosive coating) will be peeled-off due to flying stones or the like hitting the peak portion P and rust will arise at the exposed (exposed to the atmosphere) portions of the metal. [00501 In contrast, in the aerodynamic structure 10 for a vehicle, as described above, the projecting height H of the convex side ridgeline Rf with respect to the concave side ridgeline Rr is gradually decreased toward the vehicle width direction structure inner end. Therefore, 12 the peak portion P, that easily receives various types of injury (damage) as described above, is not formed, or the projecting height of the peak portion P is small, and therefore, damage due to flying stones and the like is suppressed. In other words, in the aerodynamic structure 10 for a vehicle, owing to the structure that the peak portion P is not formed or the projecting height of the peak portion P is small, the strength (resistance) with respect to collision of flying stones and the like increases, or the probability of collision with flying stones and the like decreases. Note that, in a structure in which the peak portion P or the step portion B is formed at the aerodynamic structure 10 for a vehicle, it is desirable to make the projecting height of the peak portion P, the step portion B with respect to the concave side ridgeline Rr be less than or equal to 3 mm, on the basis of the knowledge that the damage that the fender liner 18 receives due to flying stones is a maximum in cases in which the diameter of the flying stones is around 3 mm. [0051] Note that the above-described embodiment shows an example in which the convex side ridgeline Rf is inclined rectilinearly on the whole with respect to the concave side ridgeline Rr, and the projecting height H of the convex side ridgeline Rf with respect to the concave side ridgeline Rr is gradually changed. However, the present invention is not limited to the same, and may be the structures relating to the modified examples shown in Fig. 6, Fig. 7 for example. [0052] In an aerodynamic structure 40 for a vehicle relating to the modified example shown in Fig. 6, a portion of the vehicle width direction outer side of the convex side ridgeline Rf extends substantially along the vehicle width direction, and the vehicle width direction inner side portion of the convex side ridgeline Rf is inclined (the projecting height H is gradually changed) with respect to the concave side ridgeline Rr. A structure in which the peak portion P is not formed or the projecting height of the peak portion P is small is thereby realized. [0053] In an aerodynamic structure 50 for a vehicle relating to the modified example shown in Fig. 7, a portion of the vehicle width direction outer side of the convex side ridgeline Rf extends substantially along the vehicle width direction (is inclined to the same extent as the convex side ridgeline Rfc of the aerodynamic structure 100 for a vehicle), and the concave side ridgeline Rr is inclined with respect to the vehicle width direction (the convex side ridgeline Rf). A structure in which the projecting height H is gradually changed is thereby realized. Due to this structure as well, a structure in which the peak portion P is not formed or the projecting height of the peak portion P is small is realized. [0054] Further, the above-described embodiment shows an example in which two of the 13 concave portions 20 are provided, but the present invention is not limited to the same and can be structured, for example, to have one or three or more concave portions 20 in accordance with the required aerodynamic performances and the like. [0055] Moreover, the above-described embodiment shows an example in which the aerodynamic structure 10 for a vehicle has the guide grooves 34, but the present invention is not limited to the same and may be, for example, a structure that does not have the guide grooves 34. [0056] Still further, the above-described embodiment shows an example in which the concave portion 20 is disposed at the rear lower edge portion 14A of the wheel house 14, but the present invention is not limited to the same. For example, the concave portion 20 may be disposed at any portion at the rear side in the vehicle body longitudinal direction, with respect to the rotation axis RC of the front wheel 15, the rear wheel 16. 14