Suboptimal control of transient nonisothermal viscoelastic fluid flows

Suboptimal control of transient viscoelastic fluid flows in a 4 to 1 planar contracting channel is investigated. The control mechanism is based on heating or cooling the fluid along a portion of the boundary of the flow domain. In order to perform the control, a nonisothermal model for viscoelastic fluids is used consisting of the Phan-Thien-Tanner model with relaxation time and elastic viscosity depending on temperature [following an exponential dependency, the Williams-Landel-Ferry model]. Moreover, the momentum, mass, and constitutive equations are coupled with the heat equation forming the so-called primal system. The goal of the control is to reduce the large recirculation zones at the corners of the contraction. The suboptimal strategy utilized for this purpose is the so-called "instantaneous control" method. (C) 2001 American Institute of Physics.