Investigação do escoamento ao redor de um corpo rombudo de parede hidraulicamente rugosa e que troca calor com o meio fluido: simulação numérica utilizando o método de partículas de temperatura

Abstract

This work investigates two-dimensional flows with subcritical Reynolds number around a circular cylinder with rough surface and kept heated at a constant temperature; the analyses include mechanisms of mixed convection heat transfer. The numerical approach discretizes the vorticity field and the heat by using particles, which characterizes a purely lagrangian description.The work contributes to the scientific literature in two ways: i) implementation of an accelerator algorithm to incorporate LES-type turbulence modeling for the temperature field, and ii) proposition of a surface roughness model for the thermal boundary layer. The second contribution is made possible through LES-type turbulence modeling, allowing that roughness effects for different average surface roughness heights interfere on behavior of pressure, drag and lift coefficients, of the boundary layer separation angle, and heat transfer from body surface to fluid domain. Those parameters are of great interest for engineering design involving various devices subject to external flows, where there is heat exchange with the fluid domain. Simulations were performed for a Reynolds number of Re = 100,000, Prandtl number of Pr = 0.71, and average surface roughness heights of ε/D = 0.001 and 0.007. The results showed that mixed convection heat transfer impacts the fluid dynamic loads in a complex manner, increasing the drag coefficient and heat transfer via Nusselt number behavior. For the latter dimensionless number, the value obtained for the simulation in the smoothed cylinder case showed some discrepancy with the expected experimental date, indicating the need for a more detailed energy balance on the thermal boundary layer. However, by implementing roughness effects, an increase in the Nusselt number was observed in proportion to the experimental results, indicating that the new two-dimensional roughness model is sensitive and provides physically consistent results. The three characteristic kinds of particles interaction consume a high computational time, which also required the use of parallel processing in OpenMP-Fortran.