Implicit algebraic model for predicting turbulent heat flux in film cooling flow

• Published in: International journal for numerical methods in fluids Vol. 64; no. 5; pp. 517 - 531
• Main Authors: Rajabi-Zargarabadi, Mehran, Bazdidi-Tehrani, Farzad
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 20.10.2010; Wiley
• Subjects: Applied sciences; Energy; Energy. Thermal use of fuels; Engines and turbines; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; film cooling; implicit algebraic model; second moment closure; turbulent heat flux; Turbulent flow; Heat flow; turbulent heat flux; Modeling; implicit algebraic model; second moment closure; Cooling system; Algebraic method; Numerical simulation; Film cooling; Gas turbine; Mesh generation; Heat transfer
• ISSN: 0271-2091; 1097-0363
• DOI: 10.1002/fld.2157

The present study addresses a new effort to improve the prediction of turbulent heat flux in the film cooling flow by applying the implicit algebraic flux (IAF) model of Rogers et al. A three‐dimensional symmetry case is investigated using a film hole length‐to‐diameter ratio of 1.75 and an injection angle of 35∘. The low Reynolds number second moment closure (SMC) model with a wall‐reflection term is employed for simulating the turbulent flow field right up to the wall. Results obtained from the IAF model are compared with two other algebraic turbulent heat flux models, namely, the simple eddy diffusivity (SED) with a constant turbulent Prandtl number and the generalized gradient diffusion hypothesis (GGDH). Comparisons of the turbulent heat flux components calculated by these models show that the major difference appears in the streamwise turbulent heat flux. These models demonstrate a significant effect on the prediction of film cooling effectiveness. The SED model with a constant prescribed value for the turbulent Prandtl number fails to predict the cooling air spreading in the lateral direction while by employing the GGDH and IAF models, the spreading of the cooling air and the decay of the effectiveness in the core region are reasonably predicted. A combination of the SMC and IAF models for simulating the turbulent flow and heat transfer is capable of predicting the streamwise and lateral film cooling effectiveness in very good agreement with the available experimental data. Copyright © 2009 John Wiley & Sons, Ltd.