The effects of a filter fabric calendering treatment and the permeability of filaments with regard to the particle deposition phe nomena onto or into filter fabrics at the initial stage of filtration are conducted quantitatively using a microscopic forces analy sis.The flow pattern and the resistance to fluid flow in the calendered interstices were obtained numerically using the fluid flow software FLUENT~(TM).Based upon numerical data for the continuous phase,a program was devised to simulate the tran sient behaviours of pore clogging and cake formation by way of the Lagrangian approach.This estimates the change of filtrate clarity during the initial stage of filtration for various calendered fabric porosities and various filament permeabilities.Results show that in the case of tightly woven filter cloths the flow is predominantly through the yarns of the cloth,while flow will generally be directed around the yams of a loosely woven cloth,especially if the yarn is twisted lightly.Therefore,nitra tions with tightly woven but loosely twisted yarn can increase the unfavourable.but inevitable,clogging problem.The simu lated results further show that although the filtration resistance of woven filter fabric increases alter calendering,the perme ability is rectified and the clogging of the filter pores is also improved.After the calendering of the filter fabric has taken place,only the cake formation mode(in accordance with the law of blocking for all types of pore)is evident.The critical concentra tion proposed by previous investigators is not observed for calendered filter fabrics.
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