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为研究涡旋射流对湍流边界层分离控制的机理,基于大涡模拟方法建立了具有涡旋射流、扩张角为14°的圆锥扩压器数值分析模型,计算结果与相应试验数据吻合良好,验证了计算模型的合理性与精确性。通过对特征截面上流场参数的详细分析,获得了射流导致的复杂涡系形成过程,发现了射流孔附近的强涡来源于剪切层涡,剪切层涡经过破碎和耗散,在射流下游近区发展为强弱不对称的反向涡对,在下游远区形成一个纵向涡旋,该涡旋将主流流场边界层外的高能流体卷入到边界层内,增加了边界层内部的流动能量,从而延缓或抑制了流动分离。与相同条件下未采用涡旋射流控制的扩压器相比,其压力恢复系数增加19.8%,表明涡旋射流是一种有效的边界层分离控制方法。文中还分析了不同射流孔数和射流倾斜角对于压力恢复系数的影响,发现选择合适的涡旋射流孔数及其射流倾斜角等参数,可以更有效的控制扩压器内流动分离。
In order to study the mechanism of separation and control of turbulent boundary layer by vortex jet, a numerical analysis model of cone diffuser with vortex jet and expansion angle of 14 ° is established based on the large eddy simulation method. The calculated results are in good agreement with the corresponding experimental data. Calculate the rationality and accuracy of the model. Through the detailed analysis of the flow field parameters in the characteristic cross section, the formation process of complex vortices caused by jet flow is obtained. It is found that the strong vortex near the jet hole originates from the shear layer vortex and the shear layer vortex is broken and dissipated. In the downstream region, there is a reverse vortex pair with asymmetric strength and weakness. A longitudinal vortex forms in the downstream long region. The vortex forms a high-energy fluid outside the boundary layer of the mainstream flow into the boundary layer, increasing the interior of the boundary layer Of the flow of energy, thereby delaying or inhibiting the flow separation. Compared with the diffuser without vortex jet control under the same conditions, the pressure recovery coefficient increases by 19.8%, which shows that vortex jet is an effective boundary layer separation control method. In this paper, the influence of different jet holes and jet tilt angles on the pressure recovery coefficient is also analyzed. It is found that choosing the appropriate vortex jet hole number and jet tilt angle can effectively control the flow separation in the diffuser.