A SYSTEMATIC COMPUTATIONAL METHODOLOGY APPLIED TO A 3-DIMENSIONAL FILM-COOLING FLOWFIELD

Numerical results are presented for a three-dimensional discrete-jet i n 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 computatio nal model of the physical problem, including simultaneous, fully ellip tic solution of the crossflow, film-hole, and plenum regions; high-qua lity three-dimensional unstructured grid generation techniques, which have yet to be documented for this class of problems; the use of a hig h-order discretization scheme to reduce numerical errors significantly ; and effective turbulence modeling, (2) a three-way comparison of res ults to both code validation quality experimental data and a previousl y documented structured grid simulation; and (3) identification of sou rces of discrepancy between predicted and measured results, as well as recommendations to alleviate these discrepancies. Solutions were obta ined with a multiblock, unstructured/adaptive grid, fully explicit, ti me-marching, Reynolds-averaged Navier-Stokes code with multigrid, loca l rime stepping, and residual smoothing type acceleration techniques. The computational methodology was applied to the validation test case of a row of discrete jets opt a flat plate with a streamwise injection angle of 35 deg, and two film-hole length-to-diameter ratios of 3.5 a nd 1.75. The density ratio for all cases was 2.0, blowing ratio was va ried from 0.5 to 2.0, and free-stream turbulence intensity was 2 perce nt. The results demonstrate that the prescribed computational methodol ogy yields consistently more accurate solutions for this class of prob lems than previous attempts published in the open literature. Sources of disagreement between measured and computed results have been identi fied and recommendations made for future prediction of film-cooling pr oblems.