Thermal Effects on Wake Dynamics and Transport Processes in Compressible Flow Over Heated 2D Cylinder and 3D Sphere

Thermal effects on wake dynamics and the transport characteristics of energy and vorticity in compressible flow over a heated two-dimensional cylinder and a heated three-dimensional sphere are investigated using Direct Numerical Simulations (DNS) with the fully compressible Navier–Stokes equations. Simulations are performed at Reynolds numbers of 40, 80, and 150, with free-stream Mach numbers of 0.2 and 0.4, and surface-to-free-stream temperature ratios, TR, ranging from neutral (1.0) to high (3.0). A second-order robust ghost-cell immersed boundary method is employed to represent the heated surface of the bluff bodies. 2D cylinder simulations suggest that as TR increases, internal energy generation due to heat diffusion and the conversion of internal energy into kinetic energy become significantly more pronounced. Moreover, at high TR, significantly altered vorticity fields are observed, characterized by oppositely signed vorticity structures emerging upstream of the attached shear layer near the cylinder's leading edge. Analysis of the vorticity transport equation reveals that this behavior arises from baroclinic torque, defined by the cross product of the density and pressure gradients, is becoming non-negligible mechanism with increased TR. Wake dynamics are further characterized using wall-normal profiles at various surface angles and streamwise profiles at several transverse locations downstream, highlighting strong sensitivity of the flow field to TR. Finally, we discuss the effects of transitioning from two-dimensional cylinder geometry to three-dimensional sphere geometry.