Experimental Study and Numerical Simulation on Drag Reduction Characteristic of Bionic Jetting Surface

摘要

According to the characteristic on the bionics theory of the non-smooth surface that can reduce the friction resistance of a body,theoretical analysis of bionic jetting surface was studied based on the shark gill slits,and the bionic jetting surface model was built.Experimental study and numerical simulation were carried out on gyroidal objects of bionic jetting surface to study its drag reduction characteristics and drag reduction mechanisms through the experiment and simulation method.In many groups of different rotation speeds,the friction torque on a smooth surface experiment model and jetting surface experimental models were tested by using torque signal coupler,and then the jetting drag reduction characteristic curves and the friction torque characteristic curves was obtained.The numerical simulation was used with SST k-ωturbulence model for the model at the optimum rotation speed,the characteristics of the smooth surface and the jetting surface were analyzed.Results showed that the bionic jetting surface has remarkable drag reduction effect,and the drag reduction rate is related to the rotational speed of the experimental model,the jetting aperture and the jetting velocity.The calculating results were close to the experimental results,the numerical simulation results were a little higher than the experimental results,but the value was in the allowed error range,which dictated the calculating way is right.The numerical simulation conforms to the experiments on the drag reduction rate,it will further verify the drag reduction characteristics of the bionic jetting surface.The surface of jetting flow thickens the viscous bottom of the boundary layer in the downstream field of the jetting hole,and decreases the wall shear stress.Meanwhile,there is some low-speed vortex in the downstream field which further thickens the viscous bottom and decreases the wall shear stress,and this is the reason why friction resistance decreases.The experimental and numerical simulation approaches could be a support for using this drag reduction technique of bionic jetting surface on underwater vehicles in future applications.