ABSTRACT HUMPHREY CTS-9504390 UNIVERSITY OF ARIZONA The flow through a helical coil has long been the principal paradigm for investigating laminarization phenomena. Placing a straight pipe downstream of a helical coil wherein the flow has been laminarized allows a well-posed investigation of retransition phenomena. This proposal seeks to investigate such a flow using laser-Doppler velocimery, to obtain the velocity data necessary for developing and testing, in parallel with the experiment, a direct numerical simulation approach aimed at predicting laminarization and retransition phenomena in general, and in coiled and straight pipes in particular. In many industrial chemical applications, the formation of hot spots inside reactors, and of polluting byproducts with their attendant negative environmental impact, is the outcome of non-uniform mixing. It is especially important to maintain good mixing, and to avoid the tendency towards laminarization which invariably arises in regions of reduced fluid motion. Hence, this study has the potential to aid in our understanding of mixing processes and ultimately in the control of such processes which would permit the reduction of unwanted side products.
