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EFFECT OF TURBULENT HEAT FLUX MODELS ON PREDICTION OF FILM COOLING CHARACTERISTICS

DOI: 10.1615/ICHMT.2008.CHT.1260
14 pages

Farzad Bazdidi-Tehrani
School of Mechanical Engineering, Iran University of Science and Technology, Tehran 16846-13114, Iran

Mehran Rajabi Zargarabadi
Department of Mechanical Engineering Semnan University

Abstrakt

The present paper investigates the importance of turbulent heat flux modeling in predicting film cooling from a row of cylindrical holes. A three-dimensional symmetry case is examined with a film hole length-to-diameter ratio of 1.75 and an injection angle of 35°. The low Reynolds second moment closure model in combination with three different turbulent heat flux models is employed for simulating the turbulent flow and heat transfer. The simple eddy diffusivity (SED) with a constant Prandtl number, the generalized gradient diffusion hypothesis (GGDH) and the higher-order GGDH (HOGGDH) are examined for modeling the turbulent heat flux, ui θ. Comparisons of turbulent heat flux components calculated by these models show that the major difference is for the streamwise turbulent heat flux. The SED model gives the minimum magnitude for both wall-normal and spanwise components of turbulent heat flux in comparison with the GGDH and HOGGDH models. Also, these models have a significant effect on the prediction of film cooling effectiveness. Applying the GGDH and HOGGDH models causes the predicted film cooling effectiveness in the downstream region to decrease as compared with the SED model. However, in the near injection-hole region the SED model represents the minimum (slightly lower) predictions of film cooling effectiveness. This is due to the significant effect of streamwise component of turbulent heat flux.

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