Date of Award
12-1-2025
Document Type
Thesis
Degree Name
M.S. in Engineering Science
First Advisor
Wen Wu
Second Advisor
Shan Jiang
Third Advisor
Yiwei Han
School
University of Mississippi
Relational Format
dissertation/thesis
Abstract
This thesis examines two wall-bounded flow configurations: laminar boundary layer separation over a fully porous bump and turbulent wall jet development along an inclined ramp. These cases evaluate how surface permeability, turbulence level and pressure gradient effects shape shear layer evolution, momentum transport and large-scale organization. High fidelity simulations provide detailed analysis of mean fields, fluctuations, velocity profiles, TKE and Reynolds stresses. The results show how laminar and turbulent environments govern separation, entrainment and downstream development through distinct physical mechanisms.
In the laminar porous bump case, resolved pore flow reorganizes the separation process. A favorable pressure gradient on the windward side draws near-wall fluid into the porous material while the adverse pressure gradient on the lee side ejects it, with the greatest outflow near the crest. This outward flux creates an upward cross flow jet that lifts the separating shear layer away from the surface. The added momentum weakens near-wall reverse flow and reduces mean shear across the separating layer. By delaying shear layer roll up and the formulation of roller vortices that normally promote reattachment, the porous bump increases separation and shifts reattachment farther downstream than a solid bump.
In the turbulent wall jet case strong near-wall momentum preserves attachment even under the adverse pressure gradient created by the ramp. Instantaneous wall-normal velocity fields show sweep and burst activity concentrated near the jet core, where vertical momentum exchange drives rapid spreading. Mean fields confirm the absence of a recirculation bubble. Instead the jet thickens and rises as it entrains surrounding fluid. Normalized velocity profiles collapse in the inner region while outer region deviations reflect downstream diffusion. TKE and Reynolds stress fields show a persistent energetic zone along the shear interface.
Together these two flows demonstrate how surface characteristics and turbulence state reshape boundary layer behavior. The porous bump alters laminar separation through suction and injection process, while the wall jet maintains an attached structure governed by turbulent transport and geometric deflection. The combined analysis clarifies momentum redistribution, entrainment and shear layer dynamics across contrasting flow regimes.
Recommended Citation
Bridge, Grace, "Separating Flows Over Complex Bumps" (2025). Electronic Theses and Dissertations. 3505.
https://egrove.olemiss.edu/etd/3505