Prediction of heat transfer from impinging knife-jets using a dynamic subgrid stress model

2003 ◽  
Vol 3 (1) ◽  
pp. 22
Author(s):  
T. Cziesla ◽  
H. Chattopadhyay ◽  
N. K. Mitra ◽  
G. Biswas
Keyword(s):  
Heat Transfer ◽  
Stress Model ◽  
Subgrid Stress

Numerical Simulation of Flow and Heat Transfer Past a Turbine Blade With a Squealer-Tip

2002 ◽  
Author(s):  
Huitao Yang ◽  
Sumanta Acharya ◽  
Srinath V. Ekkad ◽  
Chander Prakash ◽  
Ron Bunker
Keyword(s):  
Heat Transfer ◽  
Reynolds Stress ◽  
Pressure Ratio ◽  
Reynolds Stress Model ◽  
Leakage Flow ◽  
Stress Model ◽  
Tip Leakage Flow ◽  
Transfer Coefficients ◽  
Model Calculations ◽  
Flow And Heat Transfer

Numerical calculations are performed to simulate the tip leakage flow and heat transfer on the squealer (recessed) tip of GE-E3 turbine rotor blade. A squealer tip with a 3.77% recess of the blade span is considered in this study, and the results are compared with the predictions for a flat-tip blade. The calculations have been performed for an isothermal blade with an overall pressure ratio of 1.32, an inlet turbulence intensity of 6.1%, and for three different tip gap clearances of 1%, 1.5% and 2.5% of the blade span. These conditions correspond to the experiments reported by Azad et al. [1]. The calculations have been performed for three different turbulence models (the standard high Re k-ε model, the RNG k-ε and the Reynolds Stress Model) in order to assess the capability of the models in correctly predicting the blade heat transfer. The predictions show good agreement with the experimental data, with the Reynolds stress model calculations clearly providing the best results. Substantial reductions in the tip heat transfer and leakage flow is obtained with the squealer tip configuration. With the squealer tip, the heat transfer coefficients on the shroud and on the suction surface of the blade are also considerably reduced.

scholarly journals Rotating Flow and Heat Transfer in Cylindrical Cavities With Radial Inflow

2012 ◽  
Author(s):  
B. G. Vinod Kumar ◽  
John W. Chew ◽  
Nicholas J. Hills
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Stress ◽  
Integral Method ◽  
Eddy Viscosity ◽  
Reynolds Stress Model ◽  
Stress Model ◽  
Rotating Disc ◽  
Flow And Heat Transfer ◽  
Viscosity Models

Design and optimization of an efficient internal air system of a gas turbine requires thorough understanding of the flow and heat transfer in rotating disc cavities. The present study is devoted to numerical modelling of flow and heat transfer in a cylindrical cavity with radial inflow and comparison with the available experimental data. The simulations are carried out with axi-symmetric and 3-D sector models for various inlet swirl and rotational Reynolds numbers upto 2.1×106. The pressure coefficients and Nusselt numbers are compared with the available experimental data and integral method solutions. Two popular eddy viscosity models, the Spalart-Allmaras and the k-ε, and a Reynolds stress model have been used. For cases with particularly strong vortex behaviour the eddy viscosity models show some shortcomings with the Spalart-Allmaras model giving slightly better results than the k-ε model. Use of the Reynolds stress model improved the agreement with measurements for such cases. The integral method results are also found to agree well with the measurements.

Gas Turbine Blade Cooling Passage With V and Broken V Shaped Ribs

2016 ◽  
Author(s):  
Sourabh Kumar ◽  
Ryoichi S. Amano
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Gas Turbine ◽  
Heat Extraction ◽  
Design Stage ◽  
Stress Model ◽  
Cfd Simulations ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Cooling Passage

Gas turbine plays a significant role throughout the industrial world. Aircraft propulsion, land-based power generation, and marine propulsion are most notable sectors where gas turbines are extensively used. The power output in these applications can be increased by raising the temperature of the gas entering the turbines. Turbine blades and vanes constrain the temperature of hot gases. For internal cooling design, techniques for heat extraction from the surfaces exposed to hot stream are based on increasing heat transfer areas and the promotion of turbulence of the cooling flow. Heat transfer is enhanced for example due to ribs, bends, rotation and buoyancy effects; all characterizes flow within the channels. Computational Fluid Dynamics (CFD) simulations are carried out using turbulence models like Large Eddy Simulation (LES) and Reynolds stress model (RSM). These CFD simulations were based on advanced computing technology to improve the accuracy of three-dimensional metal temperature prediction that can be applied routinely in the design stage of turbine cooled vanes and blades. The present work is done to study the effect of secondary flow due to the presence of ribs on heat transfer. In this paper, it is obtained by casting repeated continuous V and broken V-shaped ribs on one side of the two passes square channel into the core of blade. Two different combinations of 60° V and Broken 60° V-ribs in the channel are considered. This work is an attempt to collect information about Nusselt number inside the ribbed duct. Large Eddy Simulation (LES) is carried out on the Inlet V and Inverted V outlet continuous and Broken Inlet V and Inverted V-rib arrangements to analyze the flow pattern inside the channel. Hybrid LES/Reynolds Averaged Navier-Strokes (RANS) modeling is used to modify Reynolds stresses using Algebraic Stress Model (ASM), and a CFD strategy is proposed to predict heat transfer across the cooling channel.

Prediction of traction in elastohydrodynamic lubrication

1998 ◽  
Vol 212 (5) ◽  
pp. 321-332 ◽  
Author(s):  
A. V. Olver ◽  
H. A. Spikes
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Iterative Scheme ◽  
Elastohydrodynamic Lubrication ◽  
Heat Transfer Analysis ◽  
Stress Model ◽  
Challenging Problem ◽  
Dimensionless Form ◽  
Limiting Shear Stress ◽  
Temperature And Pressure

The prediction of traction (friction) in lubricated rolling-sliding contacts remains a challenging problem despite the development of the realistic Maxwell-Eyring-limiting shear stress model by Johnson and co-workers in the 1980s. This is largely because there is a strong coupling between the elastohydrodynamic traction and the film temperature. An added complication is that the heat conducted into the rubbing surfaces, as well as influencing traction directly, also determines the temperature in the inlet to the contact and hence the thickness of the elastohydrodynamic film. In the present paper, the traction model of Johnson et al. is combined with a heat transfer analysis of the contacting bodies as well as the film thickness regression equation. In addition, the variations in the lubricant's rheological properties with temperature and pressure based upon the measurements of Muraki et al. have been included. The traction equation is expressed in dimensionless form and is solved using a simple iterative scheme, which in many cases allows estimation of the traction without the use of a computer. Closed-form equations for the friction are given for each of the traction regimes.

scholarly journals Computation of Turbulent Heat Transfer on the Walls of a 180 Degree Turn Channel With a Low Reynolds Number Reynolds Stress Model

2002 ◽  
Author(s):  
D. L. Rigby ◽  
A. A. Ameri ◽  
E. Steinthorsson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Reynolds Stress ◽  
Low Reynolds Number ◽  
Reynolds Stress Model ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Stress Model ◽  
Generalized Gradient ◽  
Low Reynolds

The Low Reynolds number version of the Stress-ω model and the two equation k-ω model of Wilcox were used for the calculation of turbulent heat transfer in a 180 degree turn simulating an internal coolant passage. The Stress-ω model was chosen for its robustness. The turbulent thermal fluxes were calculated by modifying and using the Generalized Gradient Diffusion Hypothesis. The results showed that using this Reynolds Stress model allowed better prediction of heat transfer compared to the k-ω two equation model. This improvement however required a finer grid and commensurately more CPU time.

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