Development and Validation of Optimal Forcing Analysis Capability

Abstract

The goal of this thesis is to develop and validate the global optimal forcing analysis in our in-house massively parallel unstructured grid solver, MPCUGLES, for the eventual application to a jet in crossflow. Global optimal forcing analysis provides the capability of identifying the optimal time-periodic forcing shape and forcing frequency that causes the greatest energy gain of a flow. Forcing a jet at the preferred frequency can, in specific configurations, cause significant spreading, and forcing at the preferred frequency of a jet in crossflow may provide the same results. To validate the optimal forcing method, the lid-driven cavity problem at Re = 100 was subject to forcing and compared to the results of Brynjell-Rakola (2017). The energy gain at multiple frequencies was shown, as well as the forcing and response profiles of the optimal and sub-optimal singular values. The gain results show excellent agreement with the reference material, validating the method for a simple flow in which all boundaries were walls. The method was then validated for spatially evolving flows once applied to the Blasius boundary layer at Re = 1000. In validating this problem, the need for adjusted boundary conditions became necessary. The results showed good agreement with the reference material of Monokrousos (2010). The work presented was able to identify the correct trends in the forcing and response profiles for each frequency, as well as find the optimal forcing frequency successfully.