Type: Semester project
Ahmed bodies are generally accepted approximations for automobiles, providing simplified geometry to study the effects of various parameters on the flow across the body. As observed in experimental studies, the presence of ground generates an inherent asymmetry in the vertical direction, hence creating a vertically deflected wake at lower Reynolds number. On increasing Reynolds number, the wake gradually switches to a horizontally deflected wake [1].
In the absence of ground, Zampogna and Boujo [2], numerically observed the presence of two bifurcations, i.e. two modes becoming unstable and leading to vertically and horizontally deflected wakes
In this project, we propose a more physically accurate scenario with a moving ground to simulate a moving bluff body. We expect to observe similar symmetry breaking and would like to study the effect of ground clearance on the bifurcations.
Firstly, we will compute the baseflow using FreeFEM solver for a range of ground clearances. Then, we will use linear stability analysis to determine the critical Reynolds numbers for the Pitchfork and Hopf bifurcations.
References:
[1] Grandemange, Mathieu & Cadot, Olivier & Gohlke, Marc. (2012). Reflectional symmetry breaking of the separated flow over three-dimensional bluff bodies. Physical review. E, Statistical, nonlinear, and soft matter physics. 86. 035302. 10.1103/PhysRevE.86.035302.
[2] Zampogna, G. A., & Boujo, E. (2023). From thin plates to Ahmed bodies: linear and weakly nonlinear stability of rectangular prisms. Journal of Fluid Mechanics, 966, A19. doi:10.1017/jfm.2023.426
Supervisors: Atharva Lagwankar & Edouard Boujo