###### Abstract
[14] prepared a BUT\(-\)172 modified polyamide composite forward osmosis membrane to improve the fouling resistance of the membrane filament and increase the membrane water productivity. [PERSON], [PERSON] et al. [15] investigated the effect of flushing conditions on membrane fouling and showed that gas jet\(-\)assisted backwashing improved membrane cleaning efficiency. [PERSON], [PERSON] et al. [16] studied the effect of colloidal particles and soluble polymers on membrane fouling, and the results showed that the decrease in particle size and the increase in the adhesion of gel-like flocs, due to the secretion of hydrophobic protein biopolymers, accelerated the fouling. Deposition and cake layer formation resulted in a better mitigation of membrane fouling. [PERSON], [PERSON] et al. [17] used aluminum chloride to prepare ultrafiltration nanocomposite membranes to increase the pores on the membrane surface, which increased the membrane of water productivity. [PERSON], [PERSON] et al. [18] studied the effect of shear stress generated by upstream aeration on aerobic granulation, and the results showed that appropriate shear stress is beneficial in the generation of a stable particle structure. [PERSON], [PERSON] et al. [19] studied the effect of sequencing changes in dissolved oxygen (DO) concentration on membrane permeability of underwater membrane bioreactors (MBR), and the results show that the rate of increase in transmembrane pressure (TMP) in the anoxic phase is always steeper than that in the aerobic phase, indicating that the rate of fouling in the anoxic phase is higher than that in the aerobic phase. [PERSON], [PERSON] et al. [20] used the computational fluid dynamics coupling method and the response surface method to compare the differences in the hydraulic performance of the full\(-\)effect membrane flow channel and the traditional inlet flow channel, and discussed the influence of the geometric parameters of the inlet flow channel and the inlet velocity on the hydraulic performance. The results showed that, compared with the traditional membrane flow channel, the pressure drop difference between the inlet and outlet, the average velocity, and the shear force, was greatly improved, and the concentration polarization efficiency and membrane fouling rate was effectively reduced. [PERSON], [PERSON] et al. [21], by using the method of simulation, explored the influence of the Taylor Reynolds number and Froude number on the gravitational acceleration of particles, and found that gravity drastically decreased the clustering of bidisperse particles, whereas it could increase the clustering of monodisperse particles. [PERSON], [PERSON] et al. [22] studied the influence of tracer particles on the diffusion rate in strongly turbulent water flow in the laboratory, and also compared measurements of this turbulent-relative dispersion with the longstanding work of [PERSON] and [PERSON], finding excellent agreement with [PERSON]'s predictions. [PERSON], L et al. [23] compared the experimental measurement and simulation data of the Lagrangian velocity structure function in turbulent flow, and resolved an apparent disagreement between observed experimental and numerical scaling in order to generate interest and awareness amongst other researchers so that they could consider these phenomena in their studies as well. In this paper, a simplified membrane bioreactor model is established and then simulated. The influence of different inlet velocities on particle distribution, velocity and pressure, are studied in the flow. The results of flow evaluation and particle concentration under different conditions could help develop new strategies to control membrane fouling and thus improve water productivity.