Numerical Prediction of Fluid Elastic Instability in Normal Triangular Tube Bundles With Multiple Flexible Circular Cylinders

Abstract

Prediction of fluidelastic instability onset is a great matter of importance in designing crossflow heat exchangers from the perspective of vibration. In the present paper, the threshold of fluidelastic instability has been numerically predicted by the simulation of incompressible, unsteady, and turbulent cross flow through a tube bundle in a normal triangular arrangement. In the tube bundle under study, there were single or multiple flexible cylinders surrounded by rigid tubes. A finite volume solver based on a Cartesianstaggered grid was implemented. In addition, the ghostcell method in conjunction with the greatsourceterm technique was employed in order to directly enforce the noslip condition on the cylinders' boundaries. Interactions between the fluid and the structures were considered in a fully coupled manner by means of intermittence solution of the flow field and structural equations of motion in each time step of the numerical modeling algorithm. The accuracy of the solver was validated by simulation of the flow over both a rigid and a flexible circular cylinder. The results were in good agreement with the experiments reported in the literatures. Eventually, the flow through seven different flexible tube bundles was simulated. The fluidelastic instability was predicted and analyzed by presenting the structural responses, trajectory of flexible cylinders, and critical reduced velocities.