GPU-Accelerated High-Fidelity Implicit LES of Coanda Cylinder Flow Instabilities

This work covers multiple 3D Implicit Large Eddy Simulations covering two cases: The quiescent Coanda cylinder and the Coanda cylinder in a freestream. Previous works have shown RANS is insufficient in resolving Coanda jets, thus requiring higher fidelity tools. PyFR was chosen due to its demonstrated efficiency in running parallel computations on multiple GPUs. For the quiescent case we aim to capture unsteady flow structures observed experimentally around a Coanda cylinder placed in a water tank. Using dyes, image processing and PIV measurements, these experiments were able to capture streamwise counter-rotating vortices (Gortler instabilities) as well as some initial transient structures of interest. Due to the incompressible nature of the experimental setup the case was simulated using PyFR's artificial compressibility solver, making use of the acceleration capabilities available in dual time stepping and the synthetic turbulence generation capabilities of PyFR. In the case of the Coanda cylinder in a freestream our goal is to simulate the CoRe system (Coanda Reciprocating), a wind energy harvesting method involving the creation of reciprocating lift force on a cylinder by alternate blowing of air through opposing slots on a cylinder perpendicular to the wind direction. For the second case simulations were performed using PyFR's compressible solver due to the local Mach number crossing into the incompressible range. Simulations of the quiescent case were able to qualitatively capture both the counter rotating structures and the initial transients, though quantitative comparison of vorticity magnitude and vortex structure size shows a discrepancy from the experimental measurements. For the freestream case simulations were able to accurately capture the time averaged pressure distribution on the cylinder for momentum coefficients above 0.06, as well as the alternating lift force, though a large deviation in the drag force prediction was observed.