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利用二维PIV测速技术研究了射流孔口与壁面距离对合成射流涡环撞击壁面过程的影响,分析了涡环撞击壁面的演化规律,给出了流场的统计特性.研究结果表明,不同的孔口与壁面距离的差异,最终体现在涡环靠近壁面时涡量强度及撞击速度的差异;基于孔口直径的无量纲距离接近或小于合成射流无量纲冲程时,涡环撞壁会在壁面附近诱导产生二次涡结构.因此,合适的孔口与壁面距离对涡环撞击壁面效果起着至关重要的影响.流场统计特性分析表明,涡环撞壁后形成壁面射流,其时均速度最大值衰减速率和射流半宽度扩展速率随孔口与壁面距离的增加而减小.无量纲化的壁面射流速度型均表现出自相似特性,并且与壁面层流射流的理论曲线吻合较好.
The influence of the distance between the jet orifice and the wall on the impact of synthetic jet vortex ring on the wall was studied by two-dimensional PIV velocimetry. The evolution of the vortex ring impinging on the wall was analyzed and the statistical properties of the flow field were given. The results show that different The difference of the distance between the orifice and the wall eventually shows the difference between the vorticity and the impact velocity when the vortex ring is close to the wall. When the non-dimensional distance based on the orifice diameter is close to or smaller than the dimensionless stroke of the synthetic jet, And the secondary vortex structure is induced nearby.Therefore, the appropriate distance between the orifice and the wall plays an important role in the effect of the vortex ring striking the wall.The statistical analysis of the flow field shows that the wall jet is formed after the vortex ring collides with the wall, The maximum velocity decay rate and half-width jet velocity decrease with the increase of the distance between the orifice and the wall, and the non-dimensional wall jet velocities exhibit self-similar characteristics and agree well with the theoretical curve of the wall-surface fluid jet.