考虑颗粒动态尺度影响的固液相间阻力修正模型研究

Investigation on Drag Force Modification Model Considering Influence of Particle Dynamic Scale for Solid-liquid Two-phase Flow

摘要:

阻力模型是影响悬移质固液两相流固相浓度分布计算结果的重要因素，现有的相间阻力模型未考虑颗粒动态尺度引起的周围流体湍流强度改变对颗粒运动和扩散的影响，导致固相浓度计算结果与试验值相比仍有误差。为此，针对悬移质固液两相流，采用流体湍流强度变化率与颗粒动态尺度的表达式，对MTE-Wen-Yu模型进行修正得到改进的PDS-MTE-Wen-Yu模型。通过圆管内固液两相流数值计算对改进模型进行了验证。结果表明，在不同进口流速、不同进口固相浓度和不同固相颗粒粒径时，相比于Wen-Yu模型和MTE-Wen-Yu模型，PDS-MTE-Wen-Yu模型计算得到的固相浓度分布与试验值更加吻合，计算精度更高。在湍流核心区，PDS-MTE-Wen-Yu模型和MTE-Wen-Yu模型的计算精度基本相同；但在近壁区内，PDS-MTE-Wen-Yu模型具有更高的计算精度。但是，随着颗粒粒径和固相浓度的增大，由于大粒径颗粒的惯性增大，湍流改变对颗粒的影响随之降低，PDS-MTE-Wen-Yu模型的计算误差逐渐增大。在固液两相流压力场计算时，MTE-Wen-Yu模型和PDS-MTE-Wen-Yu模型计算得到的压力降基本相同，都更接近试验值，但仍存在一定的误差。因此，PDS-MTE-Wen-Yu模型具有较高的计算精度，更适用于固相颗粒粒径较小的低浓度悬移质固液两相流固相浓度和小流速、低浓度固液两相流压力场的计算。

Abstract:

The drag force model of Euler-Euler two-phase flow numerical method is an important factor affecting the calculation results of the solid concentration distribution in suspended load sediment solid-liquid two-phase flow. The existing interphase drag force model does not consider the influence of the turbulence intensity change of the surrounding fluid caused by the particle dynamic scale on the movement and diffusion of particle, resulting in the calculated error of the solid concentration compared with the experimental value. To this end, the improved drag force modified model PDS-MTE-Wen-Yu model was obtained by modifying the MTE-Wen-Yu model with the correlation expression of the fluid turbulence intensity change ratio and particle dynamic scale for sediment-laden flow. The improved drag force modified model was verified by the solid-liquid two-phase flow numerical simulation in circular pipes. The results showed that for the numerical simulations of solid-liquid two-phase flow with different particle diameters, different flow velocities and different solid concentrations, the solid concentration distribution calculated by the PDS-MTE-Wen-Yu model was more consistent with the experimental values and the calculation accuracy was higher compared with that of the Wen-Yu model and MTE-Wen-Yu model. The calculation accuracy of PDS-MTE-Wen-Yu model and MTE-Wen-Yu model was basically the same in the turbulent core region, while the PDS-MTE-Wen-Yu model owned higher calculation accuracy in the near-wall region. However, the calculation error of the solid concentration distribution obtained by PDS-MTE-Wen-Yu model was gradually increased with the increase of particle diameter because of the increased inertia of large size particle and the decrease influence of turbulence intensity change on large size particle. For the pressure field of solid-liquid two-phase flow, the pressure drop calculated by the MTE-Wen-Yu model and the PDS-MTE-Wen-Yu model was basically the same. Both of them were closer to the experimental values compared with the Wen-Yu model, but there were still some errors with the experimental values. Therefore, the PDS-MTE-Wen-Yu model owned higher calculation accuracy. It was more suitable for the solid concentration calculation in the suspended load sediment solid-liquid two-phase flow with small diameter particle and the pressure field calculation of the solid-liquid two-phase flow with the small flow velocity and the low solid concentration.