Interface-resolved direct numerical simulations of the particle-laden turbulent flows in a square duct are performed with a direct-forcing fictitious domain method. The effects of the finite-size particles on the mean and root-mean-square (RMS) velocities are investigated at the friction Reynolds number of 150 (based on the friction velocity and half duct width) and the particle volume fractions ranging from 0.78% to 7.07%. Our results show that the mean secondary flow is enhanced and its circulation center shifts closer to the center of the duct cross section when the particles are added. The reason for the particle effect on the mean secondary flow is analyzed by examining the terms in the mean streamwise vorticity equation. It is observed that the particles enhance the gradients of the secondary Reynolds normal stress difference and shear stress in the near-wall region near the corners, which we think is mainly responsible for the enhancement in the mean secondary flow. Under a prescribed driving press...

中文翻译：

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有限尺寸中性浮力粒子对方管内湍流流动的影响

使用直接强制虚拟域方法对方形管道中充满颗粒的湍流进行界面分辨直接数值模拟。在摩擦雷诺数为 150（基于摩擦速度和半管道宽度）和颗粒体积分数范围为 0.78% 时，研究了有限尺寸颗粒对平均和均方根 (RMS) 速度的影响到 7.07%。我们的结果表明，当添加颗粒时，平均二次流得到增强，其循环中心更靠近管道横截面的中心。通过检查平均流向涡量方程中的项，分析了粒子对平均二次流的影响的原因。观察到颗粒增强了角附近近壁区域的二次雷诺法向应力差和剪切应力的梯度，我们认为这主要是平均二次流增强的原因。在规定的驾驶压力下...