Kodie-Ampaw, Joseph Kwabena (2025) Numerical Investigation of the Unsteady Turbulent Wake Regimes of a Notchback Ahmed Body. Masters thesis, Concordia University.
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Abstract
This study investigates the influence of Reynolds number on the unsteady turbulent wake regimes of a notchback Ahmed body with an effective backlight angle of 17.8°. Three-dimensional improved delayed detached eddy simulations (IDDES) were conducted at two Reynolds numbers, Reh = 10000 (denoted as Re1E4) and Reh = 50000 (Re5E4), representing symmetric and fully asymmetric flow regimes, respectively. Detailed aspects of the wake dynamics, including the mean flow, Reynolds stresses, large-scale anisotropy, global instabilities, and the pumping motion (i.e., quasi-periodic expansion and contraction) of reverse flow regions, are used to characterize the effects of Reynolds number. The results showed that, unlike Re1E4, the wake of Re5E4 is associated with asymmetric reattachment on the deck and a directional bias of the vortical structures towards one side of the body. This asymmetry significantly enhances turbulence anisotropy and causes a spanwise imbalance in turbulence production in Re5E4 compared to Re1E4. The pumping motion of the reverse flow regions was found to be synchronized between the bubbles over the slant and behind the back for Re1E4, but out of phase for Re5E4. Additionally, for Re5E4, frequent contractions on one side of the body were accompanied by expansions on the opposite side, a behavior not prevalent in Re1E4.
| Divisions: | Concordia University > Gina Cody School of Engineering and Computer Science > Mechanical, Industrial and Aerospace Engineering |
|---|---|
| Item Type: | Thesis (Masters) |
| Authors: | Kodie-Ampaw, Joseph Kwabena |
| Institution: | Concordia University |
| Degree Name: | M.A. Sc. |
| Program: | Mechanical Engineering |
| Date: | 27 August 2025 |
| Thesis Supervisor(s): | Essel, Ebenezer Ekow |
| Keywords: | Ahmed body, Flow Separation, Unsteady Wake dynamics, Vortex shedding |
| ID Code: | 996042 |
| Deposited By: | Joseph Kwabena Kodie-Ampaw |
| Deposited On: | 04 Nov 2025 17:13 |
| Last Modified: | 04 Nov 2025 17:13 |
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