Direct Numerical Simulation of Compressible Flows Aroundspherical Bodies Using the Immersed Boundary Method

AIAA AVIATION 2022 Forum

During atmospheric entry, the flow environment around capsules or space debris is characterized by complex fluid thermochemistry and gas-surface interactions (GSI). Computational fluid dynamics (CFD) simulations of these conditions are crucial in the design process of such objects. A promising approach for the simulation of complex geometries is the use of immersed boundary methods (IBM) and adaptive mesh refinement techniques (AMR). These methods offer reliable and efficient mesh generation and adaptation with minimal user intervention. To that end, this paper presents the recent developments of two IBM-AMR solvers coupled with the same external thermochemistry library for the accurate modelling of such complex flows including GSI. Several verification and validation cases are presented, which demonstrate the performance of the solvers. Results are analyzed in comparison with a body-conforming solver that uses the same thermochemistry library to achieve a consistent assessment of the underlying numerical methods. A good agreement between all the solvers is indicated with certain discrepancies arising due to the differences in surface treatments.

Thermal and Fluids Analysis Workshop (TFAWS) (NASA), 2017

Computational Fluid Dynamics (CFD) solutions have played an important role in the design of modern air and space transportation. CFD is also playing a significant role in the designing of new devices, such as, hypersonic airframes and propulsion systems, scramjet and ramjets. CFD is now providing the much needed guidance to designers, since analytical solutions are not available and in many cases, experimental conditions cannot be reproduced. CFD provides useful information, such that, when used along with traditional wind tunnel data enhances the understanding of pertinent fluid phenomena. However, notwithstanding its importance over the last two decades, CFD have so far failed to provide a unique method capable of solving a wide range of fluid dynamic problems, accurately, efficiently and inexpensively. The research conducted herein seeks to enhance current CFD capability by eliminating this major drawback. A CFD survey concluded that a novel scheme called Integro-Differential Scheme (IDS) Ferguson et al. 1 may have the capability to alleviate the limitations CFD currently experiences. The focus of this research is therefore to demonstrate that IDS has the capability to solve a wide variety of CFD problems accurately, efficiently and inexpensively. In particular, the focus of this paper is to demonstrate that the IDS methodology has the capability of accurately predicting complex flow physics under realistic conditions. To this end, this paper focuses on the accuracy with which the IDS captures the complex flow physics associated with multiple shock interactions in the midst of boundary layer separation and flow field expansion. Further, in efforts to directly highlight this capability, a set of Flow Physics Extraction Functions (FPEF) were developed and implemented. These functions use the primitive variables to detect shocks and expansion waves, separation and recirculation zones, and zones with high unsteadiness and vortices. The FPEF approach supplements the traditional way of exploring datasets using contour plots of primitive variables. The two problems of interest are: (i) the 'inviscid-viscous' interactions associated with the boundary layer at the leading edge of a hypersonic flat plate, and (ii) the interactions due to the injection of a high pressure sonic jet into supersonic cross flow. The results obtained from this study are very encouraging, as they demonstrated that the IDS has the capabilities of accurately predicting the fluid physics associated with complex fluid flows under realistic Reynolds numbers.

Aerospace Science and Technology, 2005

In the aerodynamic industrial design process, the use of numerical simulation, including viscous effects, is of ever increasing importance. As simple, standard Boussinesq-viscosity turbulence models have proven insufficient to correctly predict complex flow situations, attention is drawn to more reliable approaches towards the modelling of turbulence. This work aims at assessing the potential of Explicit Algebraic Reynolds Stress Models (EARSM) for application-oriented aerodynamic computations. To this end, two different EARSM are investigated on a variety of configurations in sub-and transonic steady flow, ranging from 2D aerofoils to 3D wing/body-configurations. Is is demonstrated that an increased over-all simulation quality is achieved. Thus, while their overhead with respect to standard linear approaches remains limited, EARSM constitute a valuable extension to the model range available to the aerodynamic design engineer.  2005 Elsevier SAS. All rights reserved.

This paper provides some of the last results obtained by the CFD group of the Department of Mechanics, Mathematics and Management at the Polytechnic of Bari in the development of Immersed Boundary (IB) methods. In particular, two main issues will be addressed about developing and testing two IB methods, using an advanced data structure, a very efficient solver, and an MPI parallelization for solving: i) the three-dimensional compressible Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations, coupled with the heat conduction equation, as a predictive tool for conjugate heat transfer problems, such as the refrigeration of the first stage blades of a gas turbine by film cooling; ii) fluid-body interaction problems in incompressible laminar flows. Both methods allow one to solve complex three-dimensional problems within reasonable computer time. Results obtained by the former method are presented for a two-dimensional unsteady conjugate heat transfer problem, already considered using the original scalar 2D code, whereas several problems involving rigid as well as deforming bodies within a fluid are solved using the latter method. All of these results demonstrate the merits of both solvers. Ongoing work concerns: applications of the compressible URANS solver to three-dimensional conjugate heat transfer problems characterized by subsonic, transonic and supersonic external flow; and extension of the incompressible flow solver to the URANS and large eddy simulations so as to tackle fluid-body interaction problems at higher values of the Reynolds number.

2005

The numerical simulation of internal and external flows using the Immersed Boundary Methods allows the insertion of bodies by a force field added to the Navier-Stokes equations source term. The geometries are formed by a lagrangean mesh that overlaps, without interference, the eulerian mesh which the flow are been solved. This metodology permits, for instance, the complete independence of the lagrangean geometry, suitable for very complex flow simulation such as fluid-structure interaction. However, the evaluation of the lagrangean force field is not trivial, and several approaches are found in the literature. The Physical Virtual Model PVM, a methodology to obtain the lagrangean force field, has shown very competitive when compared against the traditional methods. In this work, an extension to the PVM to 3D domains is proposed and the classical flow around a sphere was chosen as a test case. The numerical code was written in Fortran 90 for an in-house Beowulf-class cluster with a MPI parallel library. The Navier-Stokes equations were implicit discretized by the Finite Volume Method in a spatial and temporal second order approximation. The results for flow field topologies and drag coefficients were compared against those in the literature, up to a Reynolds number of 1000.

EPJ Web of Conferences, 2014

This work deals with a numerical simulation of 2D and 3D inviscid and laminar compressible flows around a DCA 18% profile. Numerical results were achieved on non-orthogonal structured grids by the authors' in-home code with an implemented FVM multistage Runge-Kutta method and an artificial dissipation. The results are discussed and compared with other similar ones (e.g. the results by G. S. Deiwert).

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.

A new computer program, called TranAir, for analyzing complex configurations in transonic flow (with subsonic or supersonic freestream) was developed. This program provides accurate and efficient simulations of nonlinear aerodynamic flows about arbitrary geometries with the ease and flexibility of a typical panel method program. The numerical method implemented in TranAir is described. The method solves the full potential equation subject to a set of general boundary conditions and can handle regions with differing total pressure and temperature. The boundary value problem is discretized using the finite element method on a locally refined rectangular grid. The grid is automatically constructed by the code and is superimposed on the boundary described by networks of panels; thus no surface fitted grid generation is required. The nonlinear discrete system arising from the finite element method is solved using a preconditioned Krylov subspace method embedded in an inexact Newton metho...

HAL (Le Centre pour la Communication Scientifique Directe), 2018

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Direct and Large-Eddy Simulation VI

The numerical simulation of internal and external flows using the Immersed Boundary Methods allows the insertion of bodies by a force field added to the Navier-Stokes equations source term. The geometries are formed by a lagrangean mesh that overlaps, without interference, the eulerian mesh which the flow are been solved. This metodology permits, for instance, the complete independence of the lagrangean geometry, suitable for very complex flow simulation such as fluid-structure interaction. However, the evaluation of the lagrangean force field is not trivial, and several approaches are found in the literature. The Physical Virtual Model PVM, a methodology to obtain the lagrangean force field, has shown very competitive when compared against the traditional methods. In this work, an extension to the PVM to 3D domains is proposed and the classical flow around a sphere was chosen as a test case. The numerical code was written in Fortran 90 for an in-house Beowulf-class cluster with a MPI parallel library. The Navier-Stokes equations were implicit discretized by the Finite Volume Method in a spatial and temporal second order approximation. The results for flow field topologies and drag coefficients were compared against those in the literature, up to a Reynolds number of 1000.