Local Energy Dissipation Rate in an Agitated Vessel-a Comparison of Evaluation Methods

Abstract

There are two main groups of local turbulent energy dissipation rate (epsilon) evaluation methods, namely (i) velocity gradient methods and (ii) fitting the energy spectrum function. We calibrated our measurements and then applied these methods to evaluate epsilon from our measurements. The experiments were carried out in the region below the impeller, wherewe assumed the existence of local isotropic turbulence, which is the main assumption for all epsilon evaluation methods. However, the results differed from each other. Predictions obtained by the methods dealt with here are compared on the basis of our experimental program, which also brings in data obtained on relatively large vessels 0.3 and 0.4 m in inner diameter and two liquid viscosities under fully developed turbulence (Re > 50 000).