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In practical applied aerodynamics, solutions of unsteady time-accurate three-dimensional flows involving multiple bodies in relative motion are frequently required. Typical examples include the store/airframe separation from aircraft or the rotor-fuselage interaction problem in helicopter aerodynamics. Several research works have been previously conducted for the simulation of the complicated unsteady...
Summary The use of overset grids in CFD started more than two decades ago, and has achieved tremendous success in handling complex geometries[6]. In particular, overset grids have the advantage of avoiding grid remeshing when dealing with moving boundary flow problems. In this paper, two particular unstructured grids are advocated for moving boundary flow simulation, i.e., the use of overset adaptive...
A numerical approach is described that simplifies and automates the CFD solution process so that Earth scientists can utilize high-resolution Navier-Stokes flow solvers as a research tool to investigate wind events on the Earth’s surface. The current approach utilizes the OVERFLOW-2 structured overset RANS code. A genetic algorithm is used to obtain an optimal multi-zone overset grid system that reduces...
Summary Motivated by observations of relativistic jets in galactic X-ray sources and in radio galaxies, we embark on a numerical survey of relativistic jet streams. We use second order, shock-capturing discretizations in finite volume treatments for relativistic hydro- and magnetohydrodynamic flows in combination with adaptive mesh refinement (AMR). We ensure physical consistency between the primitive...
Numerical methods have become an essential tool for investigating combustion processes. In spite of the advances in solution algorithms and computer hardware, the solution of combusting flows can still place severe demands on available computational resources. In the previous work, Northrup and Groth [1] and Gao and Groth [2] have developed a parallel adaptive mesh refinement (AMR) algorithm that...
Summary A reactive solver based on a time splitting method has been coupled with an AMR platform. After having tested the solver potentiality, a diffusion flame/shock interaction is presented with AMR.
The behaviour of thin liquid films whether forced to spread or deposited as a distinct pattern on the surface of a substrate, is of enormous significance to many manufacturing and biological processes. The topic of the present study is the flow of continuous thin liquid films over surfaces containing topographical features. In the electronics sector (displays, printed circuits, micro-devices, sensors...
Summary A meshless solver LSFD-U (Upwind-Least Squares Finite Difference) has been evaluated for its performance on point distribution obtained from Cartesian like grids generated using a novel grid stitching strategy. The scheme performs well for inviscid and laminar viscous flow computations. The procedure lacks robustness for turbulent flows, because of non-positivity of viscous discretization...
The Immersed Boundary (IB) method simplifies the grid generation process for the simulation of flows with complex and/or moving solid boundaries by avoiding the need for a body-fitted mesh. The IB technique was originally developed for incompressible flows [1, 2, 3] using Cartesian grids. Recently, some of the authors have extended the IB technique to compressible flows [4] using the preconditioned...
In this paper, a new external forcing terms estimation in the virtual boundary method is proposed. In the usual virtual boundary method with feedback and direct forcing terms estimations, the unphysical oscillations near the boundary appear in the pressure field.In order to remove these unphysical oscillations, the new direct forcing terms are added not only near the boundary but also inside the boundary...
The numerical methods for the solution of the compressible Euler and Navier-Stokes equations can be classified by the mesh they use as structured grid methods, unstructured grid methods, Cartesian grid methods, and gridless methods. Each of these methods, advocated, promoted, developed, and used by their respective supporters, has its own advantages and disadvantages. The structured grid methods have...
Summary Conventional error indicators can be effectively employed for grid refinement, but provide no information on error levels in the domain, and consequently no “termination criterion”. Error estimators, on the other hand give reasonable estimate of error distribution and serve to decide suitable “termination criterion”. In this paper, we discuss the design of a new residual–based error referred...
Grid adaptation is a very powerful tool for optimizing CFD calculations. Unfortunately the typical isotropic adaptation used for 3D flows may result in excessive number of elements. The reason for this is that during refinement of the grid around, e.g. the shock wave the grid cells becomes smaller uniformly in all directions. It means that after splitting N cells in the direction normal to the shock...
Flow around an airplane includes various scales; from micro-scale near the surface to macro-scale around the airplane. The macro-scale flow basically determines the surface pressure distribution around an airplane. The microscale flow dynamics also has a significant contribution to such as the skin friction, the flow separations and the aerodynamic noise generation. Current CFD has become a powerful...
Summary A modification is proposed to the equations of linear elasticity as used to deform Euler and Navier-Stokes meshes. In particular it is seen that the equations do not admit rigid body rotations as solutions, and it is shown how these solutions may be recovered by modifying the constitutive law. The result is significantly more robust to general deformations, and combined with incremental application...
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