Simultaneous Prediction of Solid Stress, Heat Transfer and Fluid Flow by a Single Algorithm

2002 ◽  
Author(s):  
D. B. Spalding
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Thermal Stresses ◽  
Turbine Blades ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Gas Turbine Blades ◽  
Flow And Heat Transfer ◽  
Solid Stress ◽  
Simultaneous Prediction

It is frequently required to simulate fluid-flow and heat-transfer processes in and around solids which are, partly as a consequence of the flow, subject to thermal and mechanical stresses. Often, indeed, it is the stresses which are of major concern, while the fluid and heat flows are of only secondary interest. Engineering examples of fluid/heat/stress interactions include: • Gas-turbine blades under transient conditions; • “Residual stresses” resulting from casting or welding; • Thermal stresses in nuclear reactors during emergency shut-down; • Manufacture of bricks and ceramics; • Stresses in the cylinder blocks of diesel engines; • The failure of steel-frame buildings during fires. It has been customary for two computer codes to be used for the solution of such problems, one for the fluid flow and the other for the stresses. Iterative interaction between the two codes is then employed, often with considerable inconvenience. It is often believed that FLUID-FLOW and SOLID-STRESS problems must be solved by different methods and different computer programs. This is not true, if the solid-stress problems are formulated in terms of DISPLACEMENTS. The lecture exemplifies and explains how both DISPLACEMENTS and VELOCITIES can be calculated at the same time. Also described, incidentally, are economical methods of simulating: thermal RADIATION between solids immersed in fluids; and TURBULENT CONVECTION at low Reynolds numbers in the same situation.

Large-Eddy Simulation With Zonal Near Wall Treatment of Flow and Heat Transfer in a Ribbed Duct for the Internal Cooling of Turbine Blades

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Sunil Patil ◽  
Danesh Tafti
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Reynolds Numbers ◽  
Large Eddy Simulations ◽  
Internal Cooling ◽  
Mean Flow ◽  
Flow And Heat Transfer ◽  
Turbulent Statistics ◽  
Large Eddy ◽  
Near Wall

Large eddy simulations of flow and heat transfer in a square ribbed duct with rib height to hydraulic diameter of 0.1 and 0.05 and rib pitch to rib height ratio of 10 and 20 are carried out with the near wall region being modeled with a zonal two layer model. A novel formulation is used for solving the turbulent boundary layer equation for the effective tangential velocity in a generalized co-ordinate system in the near wall zonal treatment. A methodology to model the heat transfer in the zonal near wall layer in the large eddy simulations (LES) framework is presented. This general approach is explained for both Dirichlet and Neumann wall boundary conditions. Reynolds numbers of 20,000 and 60,000 are investigated. Predictions with wall modeled LES are compared with the hydrodynamic and heat transfer experimental data of (Rau et al. 1998, “The Effect of Periodic Ribs on the Local Aerodynamic and Heat Transfer Performance of a Straight Cooling Channel,”ASME J. Turbomach., 120, pp. 368–375). and (Han et al. 1986, “Measurement of Heat Transfer and Pressure Drop in Rectangular Channels With Turbulence Promoters,” NASA Report No. 4015), and wall resolved LES data of Tafti (Tafti, 2004, “Evaluating the Role of Subgrid Stress Modeling in a Ribbed Duct for the Internal Cooling of Turbine Blades,” Int. J. Heat Fluid Flow 26, pp. 92–104). Friction factor, heat transfer coefficient, mean flow as well as turbulent statistics match available data closely with very good accuracy. Wall modeled LES at high Reynolds numbers as presented in this paper reduces the overall computational complexity by factors of 60–140 compared to resolved LES, without any significant loss in accuracy.

High-Pressure Gas Turbine Vane Turbulent Flows and Heat Transfer Predicted by RANS/LES/DES

2017 ◽  
Author(s):  
Ping Dong ◽  
R. S. Amano
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Gas Turbine ◽  
Turbulent Flows ◽  
Film Cooling ◽  
Turbine Blades ◽  
Suction Side ◽  
Gas Turbine Blades ◽  
Flow And Heat Transfer ◽  
Turbine Vane

The lifetime of the modern gas turbines greatly depends on the durability of hot section components operating at high temperatures. Film cooling is key to air cooling technologies in modern gas turbine and widely used in high-temperature and high-pressure blades as an active cooling scheme. The requirements of accurate prediction of aerodynamic flow and heat transfer in gas turbine blades lay the essential foundation of cooling effectiveness improvement and working life estimation. In recent days, Large Eddy Simulations (LES) is considered as a useful tool to predict turbulent flows and heat transfer around gas turbine blades, but, comparing to the Reynolds-Averaged Navier–Stokes (RANS) methods, the LES method usually needs more computing resource and depends on computational power and mesh quality. In this paper, LES/DES (Detached Eddy Simulation) predictions were compared to RANS prediction with interest in the accuracy and improvement of turbulent flow and heat transfer phenomena around NASA’s C3X high-pressure gas turbine vane with leading edge cooling film. RANS/LES/DES were detailed and further investigated to assess their ability to predict flow and heat transfer in boundary layer around C3X vane. The current predictions showed that the mix between film cooling injections and free stream resulted in complex flow and heat transfer in the boundary layer on the external vane surface. The predictions of the aerodynamic load along the C3X vane with RANS/LES/DES were almost identical and agreed well with the experimental results. However, the heat transfer predictions with RANS/LES/DES were different. The transition prediction showed the best agreement with the experiment data in the most region. The LES prediction only partially agreed with the experimental data before separation point on the suction side and mild pressure gradient region on the pressure side. The DES and RANS predictions agreed with the experiment data after separation point on the suction side and most region on the pressure side.

Turbulent Flow and Heat Transfer in Variable Geometry U-Bend Blade Cooling Passage

2009 ◽  
Author(s):  
Krishna Guntur ◽  
R. S. Amano ◽  
Jose Martinez Lucci
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Thermal Stresses ◽  
Model Simulation ◽  
Turbine Blades ◽  
Higher Order ◽  
Secondary Flows ◽  
Gas Turbine Blades ◽  
Cooling Passage ◽  
Les Model

In modern gas turbine blades it has been a common practice to use cooling passages in gas turbine blades. In cooling processes blades have excessive thermal stresses, causing creep, oxidizing and also melting in some cases. Therefore fully understanding of the flow characteristics in the U-bend is important in designing cooling passages. The interactions between secondary flows and separation lead to very complex flow patterns. To accurately simulate these flows and heat transfer, and to improve the cooling performance, both refined turbulence models and higher-order numerical schemes are indispensable tools for turbine designers. It is the conventional belief and practice that the usage of a proper turbulence model and a reliable numerical method achieves accurate computations. The three-dimensional turbulent flows and heat transfer in a square U-bend duct are numerically studied by using a Large Eddy Simulation (LES) model. Simulation using k-ω, k-ε and RSM models has been previously reported, and used here to compare with the LES simulation. The finite volume method incorporated with higher-order bounded interpolation scheme has been employed in the present study. The objective of this study is to validate the simulation of LES model with the experimental results. Three different Reynolds numbers, 36000, 60000 and 100000, were used. This study concludes that the RSM is a better model, for Re = 36,000 and 60,000.

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