A two-way coupled Lagrangian moment approximation method for the simulation of Brownian fiber suspensions in turbulence is proposed. The flow equations are solved in an Eulerian manner. The influence of fibers on the fluid flow is taken into account by a non-Newtonian stress tensor. The fiber conformation and stresses are computed in a Lagrangian manner using the moment approximation method. The new method is used to simulate turbulent drag reduction in a plane channel. The results are compared with those of a direct Monte–Carlo solution of the Fokker–Planck equation, and a very good agreement is established. In comparison with the Newtonian flow case, the logarithmic region of the mean velocity profile shows a shift toward higher velocities, and velocity fluctuations in the streamwise direction are amplified, whereas the spanwise and wall-normal velocity fluctuations are attenuated, and the viscous sublayer is thickened. Small discrepancies between the results of the presented method and the reference data are conjectured to be mostly a consequence of the errors associated with the closure modeling, as also observed in previous Eulerian simulations.

提出了一种在湍流中模拟布朗纤维悬浮液的双向耦合拉格朗日矩逼近方法。流动方程以欧拉方式求解。非牛顿应力张量考虑了纤维对流体流动的影响。使用矩近似法以拉格朗日方式计算纤维的构型和应力。新方法用于模拟平面通道中湍流阻力的减小。将结果与Fokker-Planck方程的直接Monte-Carlo解的结果进行比较，并建立了很好的一致性。与牛顿流情况相比，平均速度分布的对数区域显示出向更高速度的偏移，并且沿流向的速度波动被放大，而翼展方向和壁法向速度波动减小，粘性子层增厚。推测该方法的结果与参考数据之间的微小差异主要是与闭合模型相关的误差的结果，正如先前在欧拉模拟中所观察到的。