An immersed boundary method for coupled multi-physics simulations (original) (raw)
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A Conjugate-heat-transfer Immersed-boundary Method for Turbine Cooling
Energy Procedia, 2015
The first high pressure stage of a modern gas turbine operates at very high temperatures that require complex blade-cooling systems to guarantee high performance and efficiency of the gas turbine while maintaining a very low level of energy losses, though using compressed air for cooling. An accurate and efficient conjugate heat transfer (CHT) solver is thus necessary to compute the flow and temperature fields of the air within the cooling channels and of the gas around the blades-by means of the Navier-Stokes and energy equations-as well as the blade temperature field, by means of the heat conduction equation. Due to the very high geometrical complexity of the cooling channels within the blades, generating a body fitted mesh for the three domains-air, gas and blade-is extremely difficult and time consuming. Nevertheless, many turbine bladecooling simulations have been performed with success, though at large computational cost, see, e.g., [1]. A promising alternative approach is provided by the Immersed Boundary (IB) method, which discretizes both the solid and fluid fields by means of a single Cartesian grid, thus reducing the grid generation process to a relatively simple and quick task-an interesting review of the IB method and its application is provided in [2]. The CFD group at the Department of Mechanics, Mathematics and Management of the Polytechnic of Bari has chosen such an approach, by first developing and improving an accurate and efficient IB method for the compressible Navier-Stokes equations [3, 4], and later extending it with success to solve CHT problems [5]. At present, these works are limited to two-dimensional serial calculations. The aim of this work is to extend the two-dimensional IB solver to three-dimensions, using a new IB least-squares reconstruction, an advanced data structure and a parallel solver, so as to obtain a computational tool capable of computing very complex CHT problems within reasonable computational times.
An Immersed Boundary Method for Complex Flow and Heat Transfer
Flow, Turbulence and Combustion, 2007
The need to predict flow and heat transfer problems requires a flexible and fast tool able to simulate complex geometries without increasing the complexity of the flow solver architecture. Here we use a finite volume code that uses a direct solver with pressure correction. A new immersed boundary method (IBM) is used for a geometry consisting of a square body in a flow. The method is applied to flow cases with and without heat transfer. The obstacle simulated in the domain is implemented by local forcing of the flow with a procedure that adjusts locally the shear stress at the position of the object in conjunction with a non-penetration condition on the body walls. This approach has already been successfully applied by Breugem and Boersma (Phys. Fluids 17:15, 2005). We extend it for the case of heat transfer between body and flow. Comparison with other methods has been carried out as well. However, the proposed method can not be simply extended to immersed boundaries not aligned with the grid.
International Journal of Chemical Engineering, 2017
The current work focuses on the development and application of a new finite volume immersed boundary method (IBM) to simulate three-dimensional fluid flows and heat transfer around complex geometries. First, the discretization of the governing equations based on the second-order finite volume method on Cartesian, structured, staggered grid is outlined, followed by the description of modifications which have to be applied to the discretized system once a body is immersed into the grid. To validate the new approach, the heat conduction equation with a source term is solved inside a cavity with an immersed body. The approach is then tested for a natural convection flow in a square cavity with and without circular cylinder for different Rayleigh numbers. The results computed with the present approach compare very well with the benchmark solutions. As a next step in the validation procedure, the method is tested for Direct Numerical Simulation (DNS) of a turbulent flow around a surface-m...
An immersed boundary method for simulation of flow with heat transfer
International Journal of Heat and Mass Transfer, 2013
In this work, the hybrid immersed boundary method is extended with immersed boundary conditions for the temperature field. The method is used to couple the flow solver with a shell heat transfer solver. The coupling back to the shell is handled by a heat source, calculated from Fourier's law. Natural convection in a square cavity with and without a hot circular cylinder, and free air cooling of an electrically heated plate are studied. For all cases an excellent agreement with numerical and experimental data is obtained. The proposed method is very well suited for many industrial applications involving natural convection.
International Journal of Numerical Methods for Heat & Fluid Flow, 2015
Purpose – The purpose of this paper is to present a numerical method for the simulation of steady and unsteady incompressible laminar flows, including convective heat transfer. Design/methodology/approach – A node centered, finite volume discretization technique is applied on hybrid meshes. The developed solver, is based on the artificial compressibility approach. Findings – A sufficient number of representative test cases have been examined for the validation of this numerical solver. A wide range of the various dimensionless parameters were applied for different working fluids, in order to estimate the general applicability of our solver. The obtained results agree well with those published by other researchers. The strongly coupled solution of the governing equations showed superiority compared to the loosely coupled solution as inviscid effects increase. Practical implications – Convective heat transfer is dominant in a wide variety of practical engineering problems, such as coo...
An immersed-boundary method for compressible viscous flows
Computers & Fluids, 2006
This paper combines a state-of-the-art method for solving the preconditioned compressible Navier-Stokes equations accurately and efficiently for a wide range of the Mach number with an immersed-boundary approach which allows to use Cartesian grids for arbitrarily complex geometries. The method is validated versus well documented test problems for a wide range of the Reynolds and Mach numbers. The numerical results demonstrate the efficiency and versatility of the proposed approach as well as its accuracy, from incompressible to supersonic flow conditions, for moderate values of the Reynolds number. Further improvements, obtained via local grid refinement or nonlinear wall functions, can render the proposed approach a formidable tool for studying complex three-dimensional flows of industrial interest.
International Journal for Numerical Methods in Fluids, 2005
A large eddy simulation (LES) methodology for turbulent flows in complex rigid geometries is developed using the immersed boundary method (IBM). In the IBM body force terms are added to the momentum equations to represent a complex rigid geometry on a fixed Cartesian mesh. IBM combines the efficiency inherent in using a fixed Cartesian grid and the ease of tracking the immersed boundary at a set of moving Lagrangian points. Specific implementation strategies for the IBM are described in this paper. A two-sided forcing scheme is presented and shown to work well for moving rigid boundary problems. Turbulence and flow unsteadiness are addressed by LES using higher order numerical schemes with an accurate and robust subgrid scale (SGS) stress model. The combined LES–IBM methodology is computationally cost-effective for turbulent flows in moving geometries with prescribed surface trajectories.Several example problems are solved to illustrate the capability of the IBM and LES methodologies. The IBM is validated for the laminar flow past a heated cylinder in a channel and the combined LES–IBM methodology is validated for turbulent film-cooling flows involving heat transfer. In both cases predictions are in good agreement with measurements. LES–IBM is then used to study turbulent fluid mixing inside the complex geometry of a trapped vortex combustor. Finally, to demonstrate the full potential of LES–IBM, a complex moving geometry problem of stator–rotor interaction is solved. Copyright © 2005 John Wiley & Sons, Ltd.
Towards Conjugate Heat Transfer in Complex Geometries With an Immersed Boundaries Cartesian Solver
2004
ABSTRACT The Cartesian incompressible RANS solver with Immersed Boundaries, IBRANS, recently developed at Stanford, has been extended to include conjugate heat transfer modeling and used for the simulation of the electrical motor of an automotive engine cooling fan system. Such applications are particularly challenging as they involve very complex geometries with tight tolerances and rotating parts. The new conjugate heat transfer capability of IBRANS has been validated on heated cylinder flows.
Conjugate Simulation of Flow and Heat Conduction With a New Method for Faster Calculation
Volume 3: Turbo Expo 2004, 2004
A new conjugate simulation program for flow and heat conduction has been developed based upon a common CFD platform UPACS. It connects flow calculation blocks and solid blocks without using surface temperature values explicitly. The time-lag between flow simulation and heat conduction calculation which is a severe problem in conjugate heat transfer has been improved by introducing a heat conduction sub-step method. The developed program has been applied to simulations of new turbine cooling structures which are the integration of impingement and pin cooling device and revealed that the pin configuration changes the cooling efficiency.