仿生射流孔形状减阻性能数值模拟及实验研究

针对横流中的侧向射流能够减小仿生射流表面摩擦阻力问题, 建立仿生射流表面模型, 利用SST k-ω湍模型对不同射流孔形状的仿生射流表面模型进行数值模拟, 并对数值模拟结果进行了实验验证. 结果表明: 当射流孔的流向长度和展向长度不变时, 3号模型的折线形射流孔减阻效果最好; 将折线形射流孔简化为圆弧形, 当r=3–5 mm时, 减阻率随着射流速度的增大而增大, 当r=4 mm时减阻效果最好, 最大减阻率为9.51%. 减阻原因: 通过射流孔向横向主流场中注入射流流体, 改变了射流表面附近边界层的流场结构, 使得边界层黏性底层厚度增加, 垂直于射流表面的法向速度梯度减小, 从而减小了壁面剪应力; 低速的射流流体被封锁在边界层内, 降低了高速流体对壁面的扫掠, 达到了减阻目的.

Numerical simulation and exp erimental study on drag reduction p erformance of bionic jet hole shap e

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-ω 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=3–5mm, 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.