Study On Drag Reduction Of Revolution Body With Dimple And Convex Tubercle

With the development of technology and society, energy issue has become increasingly prominent. It will increase velocity, and decrease the cost of energy, the noise and vibration by reducing drag force, and it is widely used in fields such as transportation facility, military and sports. It is turbulent flow on surface region of fast-moving carrier, and in variety of turbulent drag reduction methods, bionic drag reduction is an environmental and feasible one.Based on the method that combine numerical simulation with theoretical analysis, flow fields with revolution body were simulated using CFD software STAR-CCM+, and the drag reduction efficiency of bionic non-smooth surface with dimples or convex tubercles.Five types of non-smooth surface revolution body with different size of dimple with different velocity10～300m/s were simulated, as well as two types of non-smooth surface revolution body with different size of convex tubercle with a velocity of120m/s, the mesher trimmer and prism layer mesher were used for grid discretization, SST k-ω turbulence model and second-order upwind scheme were used for accurate simulations.The following results were obtained:1. With the increase of velocity, both pressure force and shear force increased, and pressure force increased much more than shear force.2. Model A、B、D reduced the total drag force in,different velocity studied in the paper; model C increased drag force when the Re number was3.4×105～8.4×105; model E increased drag force when the Re number was4.2×104, and it decreased drag force when the Re number was1.7×105-1.3×106.3. All the5dimple models achieved excellent effect at the velocity of300m/s, when the Reynolds number was1.3×106, and model B reduced the total drag force by11.14%.4. The drag reduction effects of different models were similar when the Re number was3.4×105～8.4×105.5. The basic method for bionic non-smooth surface to reduce drag was boundary control. There was low-speed rotating flow inside the dimple, and the rotating flow generated the vortex cushioning effect and driving effect, which reduced shear force; the viscous sublayer at the leeward of convex tubercle changed, so the Reynolds stress had primary effect rather than viscous shearing stress, thus reducing the shear force.6. The convex tubercles affected pressure force in two ways:convex tubercles would influence the adverse pressure region at the bottom the revolution body; adverse pressure region would be produced at the leeward of convex tubercle, thus increasing pressure force.