A Systematic Computational Methodology Applied to a Three–Dimensional Film–Cooling Flowfield

Abstract

Numerical results are presented for a three–dimensional discrete–jet in crossflow problem typical of a realistic film–cooling application in gas turbines. Key aspects of the study include: (1) Application of a systematic computational methodology that stresses accurate computational model of the physical problem, including simultaneous, fully–elliptic solution of the crossflow, film–hole, and plenum regions; high quality 3–D unstructured grid generation techniques which have yet to be documented for this class of problems; the use of a high order discretization scheme to significantly reduce numerical errors; and effective turbulence modelling; (2) A three–way comparison of results to both code validation quality experimental data and a previously documented structured grid simulation; and (3) Identification of sources of discrepancy between predicted and measured results, as well as recommendations to alleviate these discrepancies. Solutions were obtained with a multi–block, unstructured/adaptive grid, fully explicit, time–marching, Reynolds averaged Navier–Stokes code with multi-grid, local time stepping, and residual smoothing type acceleration techniques. The computational methodology was applied to the validation test case of a row of discrete jets on a flat plate with a streamwise injection angle of 35°, and two film–hole length–to–diameter ratios of 3.5 and 1.75. The density ratio for all cases was 2.0, blowing ratio was varied from 0.5 to 2.0, and free–stream turbulence intensity was 2%. The results demonstrate that the prescribed computational methodology yields consistently more accurate solutions for this class of problems than previous attempts published in the open literature. Sources of disagreement between measured and computed results have been identified, and recommendations made for future prediction of this class of problems.