Abstract A three-dimensional Computational Fluid Dynamics (CFD) model was developed to study the shear stress induced by spherical cap bubbles on industrial scale hollow fibres. Simulations and experimental data were compared for water and a 0.5 g/L xanthan gum solution that mimicked the rheological behaviour of activated sludge. The model was built on a pilot-scale membrane tank configured with five 1.5 m long hollow fibre membranes. 58–290 ml spherical cap bubbles were sparged into the system at frequencies from 0.2 to 1 Hz. The Volume of Fluid (VOF) method coupled with the Realizable k–e turbulent model was used to simulate the transient behaviour of cap bubbles rising in a Newtonian and a viscous shear-thinning liquid. CFD prediction of root mean square (RMS) shear stress induced by pulsed bubbles exhibited an inverse relationship with experimental observations of membrane fouling. At a constant flux of 25 L/m2/h (LMH), fouling decreased from 5.1 to 3.9 kPa/min as simulated RMS shear stress increased from 0.04 to 0.25 Pa. Shear fluctuations, which are considered to be beneficial for the cleaning of membranes, were less pronounced for a non-Newtonian fluid compared to in water. Increasing pulse bubble size from 115 ml to 290 ml led to a 80% increase of RMS shear stress, and therefore improved the fouling control efficiency.

中文翻译：

---

对膜污染的脉冲气泡控制的见解：气泡大小和频率的影响

摘要 开发了一个三维计算流体动力学 (CFD) 模型来研究球冠气泡在工业规模中空纤维上引起的剪切应力。对水和模拟活性污泥流变行为的 0.5 g/L 黄原胶溶液的模拟和实验数据进行了比较。该模型建立在配置有五个 1.5 m 长中空纤维膜的中试规模膜罐上。58–290 ml 球冠气泡以 0.2 到 1 Hz 的频率喷射到系统中。流体体积 (VOF) 方法与 Realizable k-e 湍流模型相结合，用于模拟在牛顿流体和粘性剪切稀化液体中上升的帽状气泡的瞬态行为。由脉冲气泡引起的均方根 (RMS) 剪应力的 CFD 预测与膜污染的实验观察结果呈反比关系。在 25 L/m2/h (LMH) 的恒定通量下，随着模拟的 RMS 剪切应力从 0.04 增加到 0.25 Pa，污垢从 5.1 kPa/min 减少到 3.9 kPa/min。剪切波动，这被认为有利于膜的清洁, 与在水中相比，对于非牛顿流体来说不那么明显。脉冲气泡尺寸从 115 ml 增加到 290 ml 导致 RMS 剪切应力增加 80%，因此提高了污垢控制效率。这被认为有利于膜的清洁，与在水中相比，对于非牛顿流体则不太明显。脉冲气泡尺寸从 115 ml 增加到 290 ml 导致 RMS 剪切应力增加 80%，因此提高了污垢控制效率。这被认为有利于膜的清洁，与在水中相比，对于非牛顿流体则不太明显。脉冲气泡尺寸从 115 ml 增加到 290 ml 导致 RMS 剪切应力增加 80%，因此提高了污垢控制效率。