Fully Coupled Large Eddy Simulation-Conjugate Heat Transfer Analysis of a Ribbed Cooling Passage Using the Immersed Boundary Method

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
Tae Kyung Oh ◽  
Danesh K. Tafti ◽  
Krishnamurthy Nagendra
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Conduction ◽  
Immersed Boundary Method ◽  
Conjugate Heat Transfer ◽  
Immersed Boundary ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Cooling Passage ◽  
Fully Coupled

Abstract The study focuses on evaluating fully coupled conjugate heat transfer (CHT) simulation in a ribbed cooling passage with a fully developed flow assumption using large eddy simulation (LES) with the immersed boundary method (IBM-LES-CHT). The IBM-LES and the IBM-CHT frameworks are validated by simulating purely convective heat transfer in the ribbed duct, and a laminar boundary layer flow over a 2D flat plate with heat conduction, respectively. For the main conjugate simulations, a ribbed duct geometry with a blockage ratio of 0.3 is simulated at a bulk Reynolds number of 10,000 with a conjugate boundary condition applied to the rib surface. The nominal Biot number is kept at 1, which is similar to the comparative experiment. It is shown that the time scale disparity between turbulent fluid flow and heat conduction in solid can be overcome by using an artificially high solid thermal diffusivity. While the diffusivity impacts the instantaneous fluctuations in temperature and heat transfer, it has an insignificant effect on the predicted Nusselt number. Comparison between IBM-LES-CHT and iso-flux heat transfer simulations shows that the iso-flux case predicts higher local Nusselt numbers at the back face of the rib. Furthermore, the local Nusselt number augmentation ratio (EF) predicted by IBM-LES-CHT is compared with experiment and another LES conjugate simulation. The present LES calculations predict higher EFs on the leading face of the rib and show a different trend at the trailing face when CHT is activated.

LES-Conjugate Heat Transfer Analysis of a Ribbed Cooling Passage Using the Immersed Boundary Method

2019 ◽  
Author(s):  
Tae Kyung Oh ◽  
Danesh Tafti ◽  
Krishnamurthy Nagendra
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Immersed Boundary Method ◽  
Conjugate Heat Transfer ◽  
Heat Transfer Analysis ◽  
Front Face ◽  
Immersed Boundary ◽  
Nusselt Numbers ◽  
Boundary Method ◽  
Cooling Passage

Abstract The present study focuses on evaluating fully-coupled conjugate heat transfer simulation in a ribbed cooling passage with a fully developed flow assumption using LES with the immersed boundary method (IBM-LES-CHT). The IBM-LES and the IBM-CHT frameworks are validated prior to the main simulations by simulating purely convective heat transfer in the ribbed duct, and a laminar boundary layer flow over a 2D flat plate with heat conduction, respectively. For the main conjugate simulations, a ribbed duct geometry with a blockage ratio of 0.3 is simulated at a bulk Reynolds number of 10,000 with a conjugate boundary condition applied to the rib surface. The nominal Biot number is kept at 1, which is similar to the comparative experiment. As a means to overcome a large time scale disparity between the fluid and the solid regions, the use of a high artificial solid thermal diffusivity is compared to the physical diffusivity. It is shown that while the diffusivity impacts the instantaneous fluctuations in temperature, heat transfer and Nusselt numbers, it has an insignificantly small effect on the mean Nusselt number. Comparison between IBM-LES-CHT and iso-flux heat transfer simulations shows that the iso-flux case predicts higher local Nusselt numbers at the back face of the rib. Furthermore, the local Nusselt number augmentation ratio (EF) predicted by IBM-LES-CHT is compared to experiment and another LES conjugate simulation. Even though there is a mismatch between IBM-LES-CHT predictions and other two studies at the front face of the rib, the area-averaged EF compares reasonably well in other regions between IBM-LES-CHT prediction and the comparative studies.

scholarly journals High-Fidelity Multiphysics Simulation of a Confined Premixed Swirling Flame Combining Large-Eddy Simulation, Wall Heat Conduction and Radiative Energy Transfer

2017 ◽  
Author(s):  
Chai Koren ◽  
Ronan Vicquelin ◽  
Olivier Gicquel
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Large Eddy Simulation ◽  
Wall Temperature ◽  
Radiative Heat Transfer ◽  
Conjugate Heat Transfer ◽  
Radiative Heat ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Swirling Flame

A multi-physics simulation combining large-eddy simulation, conjugate heat transfer and radiative heat transfer is used to predict the wall temperature field of a confined premixed swirling flame operating under atmospheric pressure. The combustion model accounts for the effect of enthalpy defect on the flame structure whose stabilization is here sensitive to the wall heat losses. The conjugate heat transfer is accounted for by solving the heat conduction within the combustor walls and with the Hybrid-Cell Neumann-Dirichlet coupling method, enabling to dynamically adapt the coupling period. The exact radiative heat transfer equation is solved with an advanced Monte Carlo method with a local control of the statistical error. The coupled simulation is carried out with or without accounting for radiation. Excellent results for the wall temperature are achieved by the fully coupled simulation which are then further analyzed in terms of radiative effects, global energy budget and fluctuations of wall heat flux and temperature.

scholarly journals Fully Coupled Large Eddy Simulation of Conjugate Heat Transfer in a Ribbed Channel with a 0.1 Blockage Ratio

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2096
Author(s):  
Joon Ahn ◽  
Jeong Chul Song ◽  
Joon Sik Lee
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Conjugate Heat Transfer ◽  
Heat Transfer Analysis ◽  
Scale Model ◽  
Computational Domain ◽  
Blockage Ratio ◽  
Ribbed Channel ◽  
Large Eddy ◽  
Cooling Passage

Large eddy simulations are performed to analyze the conjugate heat transfer of turbulent flow in a ribbed channel with a heat-conducting solid wall. An immersed boundary method (IBM) is used to determine the effect of heat transfer in the solid region on that in the fluid region in a unitary computational domain. To satisfy the continuity of the heat flux at the solid–fluid interface, effective conductivity is introduced. By applying the IBM, it is possible to fully couple the convection on the fluid side and the conduction inside the solid and use a dynamic subgrid scale model in a Cartesian grid. The blockage ratio (e/H) is set at 0.1, which is typical for gas turbine blades. Through conjugate heat transfer analysis, it is confirmed that the heat transfer peak in front of the rib occurs because of the impinging of the reattached flow and not the influence of the thermal boundary condition. When the rib turbulator acts as a fin, its efficiency and effectiveness are predicted to be 98.9% and 8.32, respectively. When considering conjugate heat transfer, the total heat transfer rate is reduced by 3% compared with that of the isothermal wall. The typical Biot number at the internal cooling passage of a gas turbine is <0.1, and the use of the rib height as the characteristic length better represents the heat transfer of the rib.

scholarly journals A Mixed-Fidelity Numerical Study for Fan–Distortion Interaction

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Yunfei Ma ◽  
Jiahuan Cui ◽  
Nagabhushana Rao Vadlamani ◽  
Paul Tucker
Keyword(s):  
Immersed Boundary Method ◽  
Numerical Study ◽  
Immersed Boundary ◽  
Fan Performance ◽  
Inlet Distortion ◽  
Eddy Simulation ◽  
Pressure Distributions ◽  
Large Eddy ◽  
Dynamics Method ◽  
Good Agreement

Inlet distortion often occurs under off-design conditions when a flow separates within an intake and this unsteady phenomenon can seriously impact fan performance. Fan–distortion interaction is a highly unsteady aerodynamic process into which high-fidelity simulations can provide detailed insights. However, due to limitations on the computational resource, the use of an eddy resolving method for a fully resolved fan calculation is currently infeasible within industry. To solve this problem, a mixed-fidelity computational fluid dynamics method is proposed. This method uses the large Eddy simulation (LES) approach to resolve the turbulence associated with separation and the immersed boundary method (IBM) with smeared geometry (IBMSG) to model the fan. The method is validated by providing comparisons against the experiment on the Darmstadt Rotor, which shows a good agreement in terms of total pressure distributions. A detailed investigation is then conducted for a subsonic rotor with an annular beam-generating inlet distortion. A number of studies are performed in order to investigate the fan's influence on the distortions. A comparison to the case without a fan shows that the fan has a significant effect in reducing distortions. Three fan locations are examined which reveal that the fan nearer to the inlet tends to have a higher pressure recovery. Three beams with different heights are also tested to generate various degrees of distortion. The results indicate that the fan can suppress the distortions and that the recovery effect is proportional to the degree of inlet distortion.

Large eddy simulation of an axial pump with coupled flow rate calculation using the sharp interface immersed boundary method

2019 ◽  
Vol 29 (7) ◽  
pp. 2253-2276
Author(s):  
Mohammad Haji Mohammadi ◽  
Joshua R. Brinkerhoff
Keyword(s):  
Large Eddy Simulation ◽  
Flow Rate ◽  
Immersed Boundary Method ◽  
Sharp Interface ◽  
Immersed Boundary ◽  
Inlet Flow ◽  
Content Type ◽  
Eddy Simulation ◽  
Inlet Flow Rate ◽  
Large Eddy

Purpose Turbomachinery, including pumps, are mainly designed to extract/produce energy from/to the flow. A major challenge in the numerical simulation of turbomachinery is the inlet flow rate, which is routinely treated as a known boundary condition for simulation purposes but is properly a dependent output of the solution. As a consequence, the results from numerical simulations may be erroneous due to the incorrect specification of the discharge flow rate. Moreover, the transient behavior of the pumps in their initial states of startup and final states of shutoff phases has not been studied numerically. This paper aims to develop a coupled procedure for calculating the transient inlet flow rate as a part of the solution via application of the control volume method for linear momentum. Large eddy simulation of a four-blade axial hydraulic pump is carried out to calculate the forces at every time step. The sharp interface immersed boundary method is used to resolve the flow around the complex geometry of the propeller, stator and the pipe casing. The effect of the spurious pressure fluctuations, inherent in the sharp interface immersed boundary method, is damped by local time-averaging of the forces. The developed code is validated by comparing the steady-state volumetric flow rate with the experimental data provided by the pump manufacturer. The instantaneous and time-averaged flow fields are also studied to reveal the flow pattern and turbulence characteristics in the pump flow field. Design/methodology/approach The authors use control volume analysis for linear momentum to simulate the discharge rate as part of the solution in a large eddy simulation of an axial hydraulic pump. The linear momentum balance equation is used to update the inlet flow rate. The sharp interface immersed boundary method with dynamic Smagorinsky sub-grid stress model and a proper wall model is used. Findings The steady-state volumetric flow rate has been computed and validated by comparing to the flow rate specified by the manufacturer at the simulation conditions, which shows a promising result. The instantaneous and time averaged flow fields are also studied to reveal the flow pattern and turbulence characteristics in the pump flow field. Originality/value An approach is proposed for computing the volumetric flow rate as a coupled part of the flow solution, enabling the simulation of turbomachinery at all phases, including the startup/shutdown phase. To the best of the authors’ knowledge, this is the first large eddy simulation of a hydraulic pump to calculate the transient inlet flow rate as a part of the solution rather than specifying it as a fixed boundary condition. The method serves as a numerical framework for simulating problems incorporating complex shapes with moving/stationary parts at all regimes including the transient start-up and shut-down phases.

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.

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