Numerical simulation and experimental study on drag reduction performance of bionic jet hole shape

Abstract

Since the lateral jet in a horizontal stream can reduce the friction of bionic jet surface, a bionic jet surface model is established by using the SST k- turbulence model in numerical simulation of bionic jet surface for jet hole with different shape, and experimental verification of the numerical simulation results is done. Results show that, when the flow length and span length of the jet hole are kept constant, the drag reduction of the third model with broken-line jet hole is the best; the broken-line jet hole is simplified to an arc-shaped hole, when its radius r=35mm, the drag reduction rate increases with jet velocity; furthermore, the best drag reduction can be obtained when r = 4 mm, the maximum drag reduction rate is 9.51%. Drag reduction is produced because the jet fluid injected to the lateral mainstream field through jet holes, would change the flow field structure of boundary layer near jet surface, and make the thickness of the underlying viscous sublayer in boundary layer increase. As a result, the gradient of normal velocity, perpendicular to jet surface, is decreased, and thus reduces the wall shear stress. Meanwhile, the low speed jet fluid is blocked at the boundary layer, reducing the sweep of high speed fluid on the wall, which contributes to the drag reduction.