Research Of Aerodynamic Drag Reduction Characteristics Of The Variation Arc Traveling Wave Surface

With the increasing of automobile quantity, energy consumption is rapidly rising and energy crisis is growing. A large proportion of car’s fuel consumption is used to overcome its aerodynamic drag. Therefore, one effective way to save energy is to reduce air resistance of automobiles. Bionic non-smooth drag reduction technology provides a new method to reduce the aerodynamic drag.Based on the study of bionic non-smooth drag reduction technology and inspired by the desert surface morphology, a new non-smooth surface--variation arc traveling wave surface was extracted. The three-dimensional model of variation arc traveling wave surface and CFD numerical wind tunnel were built by CATIA. In order to ensure the consistency of flow field, the smooth surface and the non-smooth surface were disposed respectively on the top and bottom surfaces of numerical wind tunnel. The model was meshed by ANSYS Meshing and the numerical simulation of flow field was calculated by Fluent in ANSYS Workbench co-simulation system. The relative errors between theoretical friction coefficient and friction coefficient measured by numerical simulation were less than 2% under different velocities, which verified the feasibility of numerical wind tunnel, meshing method and numerical solution scheme.Diversified research methods were adopted to study the influence on drag reduction of design parameters of variation arc traveling wave surface and flow velocity. By analyzing the results of orthogonal test, the important order of factors in the traveling wave unit, which influenced the drag reduction effect of variation arc traveling wave surface, were in the order of:depth, eccentricity-depth ratio (The ratio of eccentricity and depth), width-depth ratio (The ratio of width and depth). Drag reduction rate increased with depth, while first increased and then decreased with eccentricity-depth ratio and width-depth ratio. By the ANOVA of the results of orthogonal test, a conclusion could be draw that the depth decides the drag reduction effect of variation arc traveling wave surface. The optimal sizes of traveling wave unit were:depth (0.6mm), eccentricity-depth ratio (0.5), width-depth ratio (5). By analyzing the results of control variables test, it was found that the drag reduction rate increased with the arrangement pitch of traveling wave unit. In order to study how the interaction of the shape and the arrangement pitch of traveling wave unit influenced the drag reduction effect, the two factors interacted test of depth and arrangement pitch was arranged. By analyzing the results of interact test, it was found that the drag reduction rate was maximum when the shape and the arrangement pitch were both in the best state. Besides, the deeper the variation arc traveling wave was, the greater impact the drag reduction rate subjected to arrangement pitch was. And the denser the variation arc traveling wave was, the greater impact the drag reduction rate subjected to its depth was. The drag reduction rate was linearly proportional to fluid velocity in range from 26m/s to 35m/s.For further study of the drag reduction mechanism of variation arc traveling wave surface, flow characteristics of wind tunnel model were analysed. It could be concluded that variation arc traveling wave surface increased the thickness of boundary layer, formed "roller bearing" effect, promoted the near-wall airflow to form coherent structures and suppressed turbulence pulsations of near-wall airflow, which reduced the frictional resistance of surface.