不同冲击角度下淹没冲击水射流的数值计算

为了研究冲击角度对淹没冲击射流流场的影响,应用计算流体动力学软件Fluent,基于Wray-Agarwal(W-A)湍流模型,对完全充分发展的淹没冲击水射流进行数值计算.研究了在恒定喷嘴高度H/D=3,不同冲击角度(15°≤θ≤90°)条件下射流流场结构和速度分布.将数值计算得到的不同冲击角度下速度分布与PIV测量结果进行比较,验证了W-A模型的预测正确性,同时探讨了冲击角度对计算结果的影响.结果表明:冲击射流沿轴心线的速度v/v_b在势核区基本保持不变,在过渡区降低,在冲击区加速降低;射流在壁面射流区流动发生转向并沿着冲击壁面扩散;射流流场结构高度依赖于冲击角θ,随着冲击角度θ增大,壁面射流横向扩散增强,厚度逐渐减小;当θ=90°时,滞止点及顺流和逆流的过渡点与冲击原点重合;随着冲击角度θ减小,滞止点逐渐远离冲击原点;当θ<30°时,滞止点消失.

Numerical simulation of submerged impinging water jet at different impact angles

Numerical simulations of fully developed submerged impinging water jet were carried out by using the commercial CFD software ANSYS Fluent with the Wray-Agarwal(W-A)turbulence model to investigate the influence of impact angle on the jet flow field.The structure and velocity distribution of the flow field with a constant jet-to-plane distance H/D=3 and different impact angles(15°≤θ≤90°)were studied. A comparison was made between the numerical results and the experimental data obtained with PIV, then the reliability of the W-A turbulence model was validated, furthermore, the influence of impinging angle on the computational results was discussed. The results show that the impinging jet axial velocity V/V_b remains unchanged basically in the potential core region, decreases in the transition region, and drops off at an acceleration in the impact zone. The jet flow changes direction and diffuses along the wall in the near wall region.The jet flow field is largely dependent on the impact angle θ. With increasing θ, the horizontal diffusion of the jet is deteriorated and the thickness is thinned.At θ=90°, the stagnation point and the point of transition in the flow direction coincid with the impact origin. The stagnation point gradually moves away from the impact origin with decreasing θ, and it disappears at θ<30°.