Computational Fluid Dynamics Modelling of the Mixing of Sewage Sludge in an Anaerobic Digester

摘要

In this paper, the development of a CFD model to simulate the mechanical mixing ofrnsewage sludge at laboratory scale is reported. The paper considers the differentrnmethods by which the non-Newtonian nature of the sludge can be modelled (e.g.rnnon-Newtonian power law, Herschel-Bulkley model) and also considers the meansrnby which turbulence closure may be attained. The paper recommends a strategy forrnmodelling mechanically mixed sewage sludge at laboratory scale. Generated flowrnpatterns are analysed and conclusions drawn as to the effectiveness of mixing in thernlaboratory scale digester. Data relating biogas yield to different mixing regimes arernreported and combined with CFD model results. From this, conclusions regardingrnvelocity gradients and biogas yield are drawn.