Under cover

1. An under cover for covering a base face of a vehicular body, comprising:

a dent part; and

a protruding part, the dent part and the protruding part being formed alternately in series on a lower face of the under cover in at least a forward-rearward direction of a vehicle, the dent part and the protruding part having a cross section formed into a serial curved face,

wherein relative to a road surface, the protruding part is positioned substantially as high as or higher than another under cover in a forward position of the under cover in the forward-rearward direction of the vehicle;

wherein the under cover is configured such that, when a small turbulence occurs in an inner part of the dent part and a turbulence layer attributable to the turbulence is formed substantially entirely below the lower face of the under cover, the turbulence layer allows an entire air flow to be spaced apart from the lower face of the under cover; and

wherein the under cover has a plurality of dent parts and protruding parts formed alternately in the forward-rearward direction of the vehicle such that a continuously wavy surface is formed.

2. The under cover according to claim 1 , wherein relative to the road surface, the protruding part is positioned substantially as high as a suspension link in a rearward position of the under cover.

3. The under cover according to claim 1 , wherein the dent part has an inner face formed substantially into a hemisphere.

4. The under cover according to claim 1 , wherein the dent part and another protruding part are formed alternately in a widthwise direction substantially perpendicular to the forward-rearward direction of the vehicle.

5. The under cover according to claim 1 , wherein the under cover is a floor under cover disposed below the base face which is a floor panel of the vehicular body.

6. The under cover according to claim 1 , wherein the under cover is formed with a plate body having a first bent part and a second bent part which are bent upwardly, respectively, at a front end and a rear end of the plate body in the forward-rearward direction of the vehicle.

7. The under cover according to claim 1 , wherein a minimum step difference between one of the dent parts and one of the protruding parts is about 5 mm, and

wherein a maximum step difference between another of the dent parts and another of the protruding parts is about 30 mm.

8. The under cover according to claim 1 , wherein a slope angle of an inner face of still another of the dent parts is from 5° to 45°.

9. The under cover according to claim 8 , wherein the slope angle of the inner face of the still another of the dent parts is from 10° to 20°.

10. The under cover according to claim 1 , wherein the another under cover is an engine under cover in a forward position in the forward-rearward direction of the vehicular body.

11. The under cover according to claim 1 , wherein the dent parts and the protruding parts formed alternately in series on the lower face of the under cover form the continuously wavy surface without one or more horizontal flat surfaces being formed therebetween.

12. The under cover according to claim 1 , further comprising a plurality of dent parts and protruding parts formed alternately in a widthwise direction substantially perpendicular to the forward-rearward direction of the vehicle such that a continuously wavy surface is formed.

13. The under cover according to claim 12 , wherein the plurality of dent parts and protruding parts formed alternately in the widthwise direction form the continuously wavy surface without one or more horizontal flat surfaces being formed therebetween.