Film Cooling Analysis Using DES Turbulence Model

Abstract

The complex dynamic nature of the spanwise vortices in film cooling of turbine blades makes it necessary to accurately model the flow field temporally and spatially using detailed simulation techniques like direct numerical simulation or large eddy simulation of turbulence. Although, the later requires less computational effort and thus can simulate flows at higher Reynolds number than direct simulation, both these methods remain very expensive. As a viable alternative, this paper presents a Spalart-Allamaras based detached eddy simulation (DES) that is applied to a film cooled flat plate for the first time. The numerical model uses an unstructured grid system to resolve the dynamic flow structures on both sides of the plate as well as inside the hole itself. Detailed computation of a single row of 35 degree round holes on a flat plate has been obtained for blowing ratio of 1.0, and a density ratio of 2.0. The DES solution is also benchmarked with Reynolds averaged Navier-Stokes formulation for the same blade-hole configuration. The comparison shows that the DES simulation, which makes no assumption of isotropy downstream of the hole, greatly enhances the realistic description of the dynamic mixing processes.

The swept rule for breaking the latency barrier in time advancing PDEs

“…In designing jet engine combustors [6], unsteady reacting flow equations are solved to help reduce emission and mitigate dangerous vibrations. In designing gas turbine blades [7,8], unsteady aero and thermodynamic equations are solved to design cooling mechanisms for increased component life and overall engine efficiency. In all these applications, the unsteady equations need to be solved long enough to reproduce the chaotic, multiscale fluid dynamics.…”

Investigation of density ratio effects on normally injected cold jets into a hot cross flow

“…Roy et al [15] performed a flat plate film cooling analysis using a Spalart-Allamaras based detached eddy simulation (DES) approach. Their numerical model included an unstructured grid system to resolve the dynamic flow structures on both sides of the plate as well as inside the hole itself.…”

Applications of Eddy Resolving Methods

“…To capture the shear layer growth the standard LES filter scale is modified to ignore azimuthal grid spacings. Such a strategy is likely to have helped in the film cooling DES of Roy et al (2003) discussed above. Comparison is made with mean velocity and pressure profiles.…”

“…The agreement with heat transfer measurements is encouraging. Roy et al (2003) explore the use of SA DES for film cooling. A single row of 35 • holes in a flat plate is considered.…”