Evaluation of particle migration models based on laser Doppler velocimetry measurements in concentrated suspensions

This study compares the predictions of several suspension temperature models of particle migration to laser Doppler velocimetry measurements in a concentrated suspension of noncolloidal spheres. We compare the shear rate, concentration, and suspension temperature profiles in narrow-gap Couette flow. The models predict the observed macroscopic shear rate and concentration profiles well at moderate bulk particle concentration but diverge from one another and from the data at high concentrations. In addition, the predictions of the models compare poorly with suspension temperature measurements. Most of the models greatly underpredict the magnitude of the scalar temperature, capturing instead only the magnitude of the smaller two diagonal components of the temperature tensor. Also, the models do not predict the observed variation of the suspension temperature with particle concentration. Our investigation shows that both neglect of suspension temperature anisotropy and qualitative choices of model coefficients contribute to discrepancies between the model predictions and data, of which the neglect of anisotropy is more important. (C) 2004 The Society of Rheology.