Academic Projects

This page presents the Academic Projects to date

Vorticity Streamfunction based 2D laminar NS solver

Cylinder vortex shedding at Re 100. Cylinder is rotated initially to excite unstable modes and drive a limit-cycle shedding regime (streamlines shown).
Airfoil mesh snapshot
Far-field O-grid for the airfoil. Mesh generated using pyHyp.
Unsteady simulation at Re 100 for a high angle-of-attack airfoil. Streamlines highlight the separated flow region.

This project was an outcome of a graduate course on CFD I took at the University of Tennessee, Knoxville under the guidance of Dr. Kivanc Ekici. In this project, we made a direct Navier–Stokes solver with no turbulence closure; the flow is treated as laminar, and the fidelity is governed by the chosen grid and time-step. The solver has the following capabilities:

  • Unsteady restart and time marching with BDF-2 scheme.
  • Finite differenced end to end.
  • Grid transformation techniques to convert O grid or C grid into uniform rectangular 2D grid.
  • Fully coupled fully implicit vorticity streamfunction formulation.
  • Uses Jacobian to march NSE in time with pseudo time stepping and Newton like iterations per time step.
  • Can be extended to any geometry that supports body-fitted grid (Eg: Airfoil as shown in video).
Download the full report ↗ Get the code here ↗

Transonic Buffet

2D transonic buffet for the OAT15A airfoil simulated using ADflow.
3D extruded wing OAT15A airfoil transonic buffet simulated using ADflow.

2D and 3D simulation of the shockwave boundary layer interaction (SWBLI) based shock oscillation phenomenon termed transonic buffet. This is part of an ongoing project and also a part of my contributions to ADflow solver and I am the first to simulate this using ADflow.

ADflow ↗

Linear Stability Analysis using ADflow

Unsteady vortex shedding using ADflow
Unsteady vortex shedding using ADflow at Re 100.
Unstable eigenmodes comparison
Unstable eigenmodes from ADflow compared with Marquet et al.
OAT15A eigenmode density contour
Density contour for base flow of OAT15A transonic buffet at Mach = 0.73, Reynolds = 3.2 Mil, angle of attack = 4° and the corresponding unstable eigenmode.

This is part of an ongoing project and also a part of my contributions to ADflow solver. In this work, I used ADflow solver's in built automatic differentiation tools to extract the finite volume residual-state Jacobian and use it for linear stability analysis. A formal GitHub repository for the code is in progress. Below are the key contributions in this work:

  • Simulated cylinder vortex shedding canonical case and performed LST for the steady unstable base flow at different Reynolds numbers.
  • Benchmarked eigenvalues and eigenmodes from LST against those in literature - See Marquet et al. for the classic sensitivity analysis reference.
  • Performed the LST analysis for transonic buffet (see the work in window above this for the unsteady simulation for buffet).
Click here to download report ↗ ADflow ↗