On Generating Uniform Bottom Shear Stress. Part II: Shear Stress Inducing Devices

Controlling and uniforming bottom shear stress is an important issue in many technical apparatus applied in biotechnology, chemical and process engineering, medicine and also in marine sciences. The device used in the latter application, has been referred to as microcosm, and was studied in detail in part I of this study (Khalili et al, Recent patents in Chem. Eng., 2008). The present investigation deals with quantification of the ability of shear stress uniformity achieved by two other devices known as shear stress inducers, which consist of a cone rotating in a fixed cylindrical container. In a detailed numerical study, the effect of all influencing parameters -cone angle, distance between the cone-tip and the the bottom disk, and Reynolds number- were investigated. The results confirm that the performance of shear stress inducers strongly depends on the input parameters, and that the inducers can not be regarded as a universal device to generate optimal uniformity.