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Film cooling flows are characterized by a row of jets injected at an angle from the blade surface or endwalls into the heated crossflow. The resulting flowfield is quite complex, and accurate predictions of the flow and heat transfer have been difficult to obtain, particularly in the near field of the injected jet. The flowfield is characterized by a spectrum of vortical structures including the dominant kidney vortex, the horse‐shoe vortex, the wake vortices and the shear layer vortices. These anisotropic and unsteady structures are not well represented by empirical or ad‐hoc turbulence models, and lead to inaccurate predictions in the near field of the jet. In this paper, a variety of modeling approaches have been reviewed, and the limitations of these approaches are identified. Recent emergence of Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES) tools allow the resolution of the coherent structure dynamics, and it is shown in this paper, that such approaches provide improved predictions over that obtained with turbulence models.

No abstract

This study investigates the performance of several existing turbulence models for the prediction of film coolant jet in a crossflow. Two-equation models employing k–ε and k–ω closures, broadly categorized as high-Reynolds-number formulations, low-Reynolds-number formulations, DNS-based formulation, and nonlinear formulations have been used to simulate the flow. In all, seven different turbulence models have been tested. Predictions with different models have been compared with experimental results of Ajersch et al. (1995) and with each other to critically evaluate model performance. The assessment of models has been done keeping in mind that all models have been formulated for wall-bounded flows and may not be well suited for the jet-in-a-crossflow situation. Close agreement with experimental results was obtained at the jet exit and far downstream of the jet injection region, but all models typically overpredicted the magnitude of the velocities in the wake region behind the jet. The present study clearly underscores the deficiencies of the current models, and demonstrates the need for improvements. [S0889-504X(00)03002-6]

This study investigates the performance of several existing turbulence models for the prediction of film coolant jet in a crossflow. Two equation models employing k-ε and k-ω closures, broadly categorized as high Reynolds number formulations, low Reynolds number formulations, DNS based formulation and non-linear formulations have been used to simulate the flow. In all, seven different turbulence models have been tested. Predictions with different models have been compared with experimental results of Ajersch et al. (1995) and with each other to critically evaluate model performance. The assessment of models has been done keeping in mind that all models have been formulated for wall bounded flows and may not be well suited for the jet-in-a-crossflow situation. Close agreement with experimental results was obtained at the jet exit and far downstream of the jet injection region, but all models typically overpredicted the magnitude of the velocities in the wake region behind the jet. The present study clearly underscores the deficiencies of the current models, and demonstrates the need for improvements.