Turan Mustafa, Sabah Eyup, Gulsen Hakki, Celik Mehmet S
Environmental Engineering Department, Civil Engineering Faculty, Istanbul Technical University, Ayazaga, Istanbul 80626, Turkey.
Environ Sci Technol. 2003 Sep 15;37(18):4288-92. doi: 10.1021/es020661r.
Effective cleaning of granular filters during backwashing processes needs maximum turbulence and maximum shear in the fluid particle field. The energy dissipation in a backwashed filter as a particulate fluidized bed arises due to the suspending and random motions of particles and turbulent fluctuations in the bed. Size, density, and sphericity of the filter materials greatly influence the fluidization behavior of the media. In this study, a new model is proposed for predicting the energy dissipation parameters namely the hydrodynamic shear stress (tau(a)), the velocity gradient (G(a)), the turbulence dissipation coefficient (C(a)), and the turbulence parameter (C(a)0.5/Re) in backwashing of filters for different types of filter materials (sand, anthracite, and glass ball). The hydrodynamic shear stress is the dominant mechanism of filter cleaning and appears to increase with increasing the density and size of the filter media particles. Using the basic set of data, a step by step procedure is developed to compute the velocity gradient G(a), the turbulence dissipation coefficient C(a), the hydrodynamic shear stress tau(a), and the turbulent parameter (C(a)0.5/ Re).
在反冲洗过程中，对粒状滤池进行有效清洗需要在流体颗粒场中实现最大程度的湍流和最大的剪切力。作为颗粒流化床的反冲洗滤池中的能量耗散，是由于颗粒的悬浮和随机运动以及床层中的湍流波动而产生的。滤料的尺寸、密度和球形度极大地影响了介质的流化行为。在本研究中，提出了一种新模型，用于预测不同类型滤料（砂、无烟煤和玻璃球）在滤池反冲洗过程中的能量耗散参数，即流体动力剪切应力（τ(a)）、速度梯度（G(a)）、湍流耗散系数（C(a)）和湍流参数（C(a)0.5/Re）。流体动力剪切应力是滤池清洗的主要机制，并且似乎随着滤料颗粒密度和尺寸的增加而增大。利用这组基本数据，开发了一个逐步程序来计算速度梯度G(a)、湍流耗散系数C(a)、流体动力剪切应力τ(a)和湍流参数（C(a)0.5/Re）。
