Keywords: entropy generation, numerical simulation, second law analysis, turbine blades, external heat convection, flow losses, transitional subsonic flows, fluid flow, turbulent irreversibilities
Reynolds Averaged Navier-Stokes-based numerical simulation of external heat convection and losses for transitional subsonic flows through a 2D turbine passage
The paper deals with the numerical simulation of fluid flow, heat transfer and losses of a 2D high turning turbine blade passage. The mathematical model of flow is based on the Reynolds Averaged Navier-Stokes (RANS) equations completed with the numerically friendly formulation of v²?f closure model of Lien and Durbin (1996) for turbulent momentum and the algebraic closure model of Rokni and Sunden (2003) for turbulent heat flux. The boundary layer transition is free and is triggered by the turbulence model and numerical procedure. According to the continuum level of second law statement, the flow losses are measured by the volumetric rate of entropy generation. The Reynolds averaged expression of the entropy source revealed the existence of mean and turbulent components of irreversibility. The numerical simulation emphasise that, by comparing with the other closure models, v²?f represents the better choice, even if it predicts the boundary layer transition too earlier. The irreversibility field analysis proved that the turbulent irreversibility components are responsible for more than half from the overall losses, therefore they cannot be neglected.