Prediction of turbulent oscillatory flows in complex systems

Publisher Summary The chapter discusses oscillatory flow in a complex geometry at transitional Reynolds numbers. A stochastically based time history reconstruction technique is used to enable comparisons with unfiltered turbulence intensity measurements. The performance of the standard k-e. and low and high Reynolds number k-l model variants is considered. Because of near wall grid distribution sensitivity, the k-e model is not found suitable for complex geometry, transitional Reynolds number flows such as those found in electronic systems. The high Reynolds number k-l model's constrained length scale diminishes the near wall grid distribution sensitivity giving similar results to those for the low Reynolds number variant. Predicted amplitudes and frequencies show significant differences when compared to measurements. If the predicted flow unsteadiness amplitudes are scaled to match the measurements and is incorporated into the stochastic reconstruction technique, an encouraging agreement is found with total intensity measurements. A multilevel convergence acceleration is found to give significant time savings for steady flows, and a novel differential equation-based wall distance algorithm is shown to be effective.