College of Graduate Studies: Theses & Dissertations
Term of Award
Spring 2026
Degree Name
Master of Science, Mechanical Engineering
Document Type and Release Option
Thesis (open access)
Copyright Statement / License for Reuse
This work is licensed under a Creative Commons Attribution 4.0 License.
Department
Department of Mechanical Engineering
Committee Chair
Mosfequr Rahman
Committee Member 1
Marcel Ilie
Committee Member 2
Valentin Soloiu
Abstract
Transonic shock buffet predictions using the Shear Stress Transport (SST) k–ω turbulence model are known to be sensitive to the stress-limiter coefficient a₁, yet no systematic investigation of this sensitivity exists. This thesis presents a parametric study of a₁ for two-dimensional URANS simulation of shock buffet on the OAT15A supercritical airfoil at M = 0.73 and Re = 3 × 10⁶. Eleven a₁ values (0.25–0.37) are examined at α = 3.5°, and a matrix of five a₁ values across five angles of attack (3.0°–3.9°) maps the interaction with incidence. The results reveal that a₁ acts as a bifurcation parameter: a supercritical Hopf bifurcation threshold at a₁* ≈ 0.295 separates steady and oscillatory solutions, with the oscillation amplitude following Stuart–Landau scaling. Below the threshold, decreasing a₁ drives the solution through a period-doubling cascade from clean periodic oscillations to period-doubled states. The buffet onset angle exhibits a step-like dependence on a₁: for a₁ ≤ 0.28, the predicted onset agrees with the experimental value of 3.1°, while for a₁ ≥ 0.31 the onset shifts to higher incidence or vanishes. The bifurcation structure is angle-of-attack dependent, with the period-doubling cascade at α = 3.5° not generalizing to higher incidence. These findings provide the first quantitative basis for selecting a₁ in SST-based buffet computations, with a₁ = 0.27–0.28 recommended for the OAT15A airfoil.
Recommended Citation
Vowotor, Melinawo, "Influence of the SST k-ω Stress-Limiter Coefficient on Transonic Shock Buffet Prediction for the OAT15A Supercritical Airfoil" (2026). College of Graduate Studies: Theses & Dissertations. 3105.
https://digitalcommons.georgiasouthern.edu/etd/3105
Research Data and Supplementary Material
Yes
