scholarly journals Large Eddy Simulation of Heat Transfer Performance Enhancement due to Unsteady Flow in Compound Channels

2011 ◽  
Vol 23 (2) ◽  
pp. 132-138 ◽  
Author(s):  
Seong-Ho Hong ◽  
Jong-Keun Shin ◽  
Young-Don Choi
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Unsteady Flow ◽  
Heat Transfer Performance ◽  
Performance Enhancement ◽  
Transfer Performance ◽  
Compound Channels ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Large-Eddy Simulation and Conjugate Heat Transfer in a Round Impinging Jet

2014 ◽  
Author(s):  
Francis Shum-Kivan ◽  
Florent Duchaine ◽  
Laurent Gicquel
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Large Eddy Simulation ◽  
Unsteady Flow ◽  
Conjugate Heat Transfer ◽  
Wall Jet ◽  
Hybrid Strategy ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Features

This study addresses and evaluates the use of high fidelity Large Eddy Simulation (LES) for the prediction of Conjugate Heat Transfer (CHT) of an impinging jet at a Reynolds number of 23 000, a Mach number of 0.1 and for a nozzle to plate distance of H/D = 2. For such simulations mesh point localization as well as the turbulent model and the numerical scheme are known to be of primary importance. In this context, a compressible unstructured third order in time and space LES solver is assessed through the use of WALE sub-grid scale model in a wall-resolved methodology. All simulations discussed in this document well recover main unsteady flow features (the jet core development, the impinging region, the deviation of the flow and the wall jet region) as well as the mean statistics of velocity. Convergence of the wall mesh resolution is investigated by use of 3 meshes and predictions are assessed in terms of wall friction and heat flux. The meshes are based either on full tetrahedral cells or on a hybrid strategy with prism layers at the wall and tetrahedral elsewhere. The hybrid strategy allows reaching good discretization of the boundary layers with a reasonable number of cells. Unsteady flow features retrieved in the jet core, shear layer, impinging region and wall jet region are analyzed and linked to the unsteady and mean heat flux measured at the wall. To finish, a LES based CHT computation relying on the finer grid is used to access the plate temperature distribution. Nusselt number profiles along the plate for the isothermal and the coupled cases are also provided and compared.

scholarly journals Assessing IDDES-Based Wall-Modeled Large-Eddy Simulation (WMLES) for Separated Flows with Heat Transfer

Fluids ◽  
2021 ◽  
Vol 6 (7) ◽  
pp. 246
Author(s):  
Rozie Zangeneh
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Large Eddy Simulation ◽  
Skin Friction ◽  
Heat Fluxes ◽  
Separated Flows ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Isothermal Wall

The Wall-modeled Large-eddy Simulation (WMLES) methods are commonly accompanied with an underprediction of the skin friction and a deviation of the velocity profile. The widely-used Improved Delayed Detached Eddy Simulation (IDDES) method is suggested to improve the prediction of the mean skin friction when it acts as WMLES, as claimed by the original authors. However, the model tested only on flow configurations with no heat transfer. This study takes a systematic approach to assess the performance of the IDDES model for separated flows with heat transfer. Separated flows on an isothermal wall and walls with mild and intense heat fluxes are considered. For the case of the wall with heat flux, the skin friction and Stanton number are underpredicted by the IDDES model however, the underprediction is less significant for the isothermal wall case. The simulations of the cases with intense wall heat transfer reveal an interesting dependence on the heat flux level supplied; as the heat flux increases, the IDDES model declines to predict the accurate skin friction.

scholarly journals Large-Eddy Simulation Study of Flow and Heat Transfer in Swirling and Non-Swirling Impinging Jets on a Semi-Cylinder Concave Target

2021 ◽  
Vol 11 (15) ◽  
pp. 7167
Author(s):  
Liang Xu ◽  
Xu Zhao ◽  
Lei Xi ◽  
Yonghao Ma ◽  
Jianmin Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Wall Temperature ◽  
Target Surface ◽  
Impinging Jets ◽  
Small Scale ◽  
Complex Flow ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Large Eddy

Swirling impinging jet (SIJ) is considered as an effective means to achieve uniform cooling at high heat transfer rates, and the complex flow structure and its mechanism of enhancing heat transfer have attracted much attention in recent years. The large eddy simulation (LES) technique is employed to analyze the flow fields of swirling and non-swirling impinging jet emanating from a hole with four spiral and straight grooves, respectively, at a relatively high Reynolds number (Re) of 16,000 and a small jet spacing of H/D = 2 on a concave surface with uniform heat flux. Firstly, this work analyzes two different sub-grid stress models, and LES with the wall-adapting local eddy-viscosity model (WALEM) is established for accurately predicting flow and heat transfer performance of SIJ on a flat surface. The complex flow field structures, spectral characteristics, time-averaged flow characteristics and heat transfer on the target surface for the swirling and non-swirling impinging jets are compared in detail using the established method. The results show that small-scale recirculation vortices near the wall change the nearby flow into an unstable microwave state, resulting in small-scale fluctuation of the local Nusselt number (Nu) of the wall. There is a stable recirculation vortex at the stagnation point of the target surface, and the axial and radial fluctuating speeds are consistent with the fluctuating wall temperature. With the increase in the radial radius away from the stagnation point, the main frequency of the fluctuation of wall temperature coincides with the main frequency of the fluctuation of radial fluctuating velocity at x/D = 0.5. Compared with 0° straight hole, 45° spiral hole has a larger fluctuating speed because of speed deflection, resulting in a larger turbulence intensity and a stronger air transport capacity. The heat transfer intensity of the 45° spiral hole on the target surface is slightly improved within 5–10%.

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