Author: Vedant Kumar
Date/Time: July 18th, 2025 at 11:00 AM EST
Location: EGR-2164, Glenn Martin Hall | Zoom
Committee Members:
- Professor Johan Larsson, Chair
- Professor Cecilia Huertas Cerdeira
- Professor Amir Riaz
- Professor Jacob Wenegrat
- Professor Christoph Brehm, Dean’s Representative
Title of Dissertation:
Modeling and analysis of canonical turbulent shear flows
Abstract:
Turbulent flows are ubiquitous in engineering systems, however analyzing such flows around engineering-relevant geometries using turbulence-resolving simulations is difficult due to computational cost constraints. Therefore, to advance our ability to predict these flows, we need physics-based models that alleviate the computational cost while retaining high accuracy. The thesis contributes to this broad challenge by introducing two models for high-speed wall-bounded turbulent flows and through a detailed study of 3D effects in turbulent shear flows.
In Part I of this thesis, the modeling of high-speed wall-bounded turbulent flows is explored using different solution fidelities. First, a low-cost modular method is developed that estimates the mean velocity and temperature profiles, and hence the friction and heat transfer coefficients for a given Mach number, wall temperature and Reynolds number. The predictions
made by the proposed method produce up to 8 and 11% error in wall shear stress and heat flux with respect to DNS data, hence making it a useful tool for the preliminary engineering design
calculations of high-speed vehicles. Second, a new wall-model is developed with the goal of improving the prediction accuracy of wall heat flux over the current state-of-the-art for wall-modeled large eddy simulations of high-speed wall-bounded flows. The proposed model introduces two new modeling components: a simple model for the near-wall diffusion
of the turbulence kinetic energy, and an altered near-wall damping of the thermal eddy diffusivity. Both a priori and a posteriori tests are performed using reference DNS data of boundary layers up to Mach 10. The a priori errors for the proposed model are confined within 5%, although the a posteriori errors are larger, partly due to about 2% and 5% commutation error in the wall friction and heat transfer coefficients emerging from applying the wall-model on instantaneous data instead of averaged data.
In Part II of this thesis, a detailed study on three-dimensional effects in turbulent shear layers
is performed with the objective of increasing our basic understanding. The skewed shear layers are generated by shearing two misaligned boundary layers at their interface. In the long-time, a skewed shear layer approaches the planar shear layer state, provided that it is analyzed in the mean shear frame. The most prominent three-dimensional effect is the presence of a planar jet-like flow orthogonal to the mean shear direction, that decays slowly in time. Nonetheless, the decaying jet has limited influence on the overall shear layer once its relative strength diminishes. Consequently, the mean statistics of a skewed shear layer eventually evolve similar to a planar shear layer despite the continued presence of a spanwise jet.