Computational fluid dynamics

An overview of computational fluid dynamics (CFD) activities at the Langley Research Center is given. The role of supercomputers in CFD research, algorithm development, multigrid approaches to computational fluid flows, aerodynamics computer programs, computational grid generation, turbulence research, and studies of rarefied gas flows are among the topics that are briefly surveyed

Coupled flight dynamics and CFD - demonstration for helicopters in shipborne environment

The development of high-performance computing and computational fluid dynamics methods have evolved to the point where it is possible to simulate complete helicopter configurations with good accuracy. Computational fluid dynamics methods have also been applied to problems such as rotor/fuselage and main/tail rotor interactions, performance studies in hover and forward flight, rotor design, and so on. The GOAHEAD project is a good example of a coordinated effort to validate computational fluid dynamics for complex helicopter configurations. Nevertheless, current efforts are limited to steady flight and focus mainly on expanding the edges of the flight envelope. The present work tackles the problem of simulating manoeuvring flight in a computational fluid dynamics environment by integrating a moving grid method and the helicopter flight mechanics solver with computational fluid dynamics. After a discussion of previous works carried out on the subject and a description of the methods used, validation of the computational fluid dynamics for ship airwake flow and rotorcraft flight at low advance ratio are presented. Finally, the results obtained for manoeuvring flight cases are presented and discussed

Computational Fluid Dynamics Analysis Into the Improvement of Seakeeping Characteristics of a Fast Craft Using AXE-Bow

It is obviously understood that hull shape affects the movement characteristics and operability of a ship. There are several ways which can be conducted in order to improve the operability of a ship one of those is by improving ship bow. Recent development known as AXE-Bow was introduced by Delft University of Technology in collaboration with DAMEN Shipyard, in the Netherlands. It was reported that the AXE-Bow can improve the seakeeping characteristics of the vessel at higher speed (Froude number above 0.60), such as reduce vertical acceleration. The current work is carried out numerically using Computational Fluid Dynamics (CFD) approach together with the use of CFD code called Hydrostar provided by Bureau Veritas (BV). The overall results showed that there are good agreement between CFD method and the work by Delft University of University and DAMEN Shipyard. Comparative studies were also carried out with published data and demonstrated similar finding

Computational Fluid Dynamics of Crosswind Effect on a Flare Flame

This paper presents the results obtained from the application of computational fluid dynamics (CFD) to modelling the crosswind effect on a turbulent non-premixed flame. A pre-processor software GAMBIT was employed to set up the configuration, discretisation, and boundary conditions of the flame being investigated. The commercial software Fluent 6.3 was used to perform the calculations of flow and mixing fields as well as combustion. Standard k-ε and eddy dissipation models were selected as solvers for the representation of the turbulence and combustion, respectively. The results of all calculations are presented in the forms of contour profiles. During the investigation, the treatment was performed by setting a constant velocity of fuel at 20 m/s with varied cross-wind velocity and by keeping the cross-wind velocity constant at 1.1 m/s with varied fuel velocity. The results of the investigation showed that the standard k-ε turbulence model in conjunction with Eddy Dissipation Model representing the combustion was capable of producing reliable phenomena of the flow field and reactive scalars field in the turbulent non-premixed flame being investigated. Other results of the investigation showed that increasing the velocity of the crosswind, when the fuel velocity was kept constant, significantly affected the flow field, temperature and species concentrations in the flare flame. On the other hand, when the velocity of the fuel was varied at the constant crosswind velocity, the increasing velocity of the fuel gave positive impact as it enabled to counteract the effect of crosswind on the flare flam

Area preservation in computational fluid dynamics

Incompressible two-dimensional flows such as the advection (Liouville) equation and the Euler equations have a large family of conservation laws related to conservation of area. We present two Eulerian numerical methods which preserve a discrete analog of area. The first is a fully discrete model based on a rearrangement of cells; the second is more conventional, but still preserves the area within each contour of the vorticity field. Initial tests indicate that both methods suppress the formation of spurious oscillations in the field.Comment: 14 pages incl. 3 figure

Computational fluid dynamics and aerothermodynamics

Approximations applicable to the radiating, reacting, and conducting stagnation region of a hypervelocity vehicle were incorporated into a method for rapidly obtaining approximate solutions. This solution utilizes a coordinate system based upon the origin of the radiative losses and includes in a phenomenologically correct manner the effects of chemical and thermal nonequilibrium, and nonequilibrium, nongray radiative transfer. Results were presented which demonstrate the usefulness of the method and indicate which radiation parameters require further study and definition. Excellent comparisons were obtained with published results for the Fire2 data. An axisymmetric nonequilibrium inverse method was modified and extended and used to investigate and compare various vibration dissociation chemistry coupling models and radiative heat transfer approximations. The similarities, differences, and consequences of using these models in the Aero-assist Orbital Transfer Vehicles flight regime will be discussed

Computational fluid dynamics and aerothermodynamics

At the present time the efforts on this project are organized into two areas: the development of an approximate stagnation point solution and approximate flowfield studies which can be used to develop and investigate shock jump, electron temperature, radiation, vibration-dissociation coupling, and chemistry models. Progress in each area is discussed

Distributed computational fluid dynamics

Computational fluid dynamics simulations of relevance to jet-engine design, for instance, are extremely computationally demanding and the use of large-scale distributed computing will allow the solution of problems that cannot be tackled using current resources. It is often appropriate to leave the large datasets generated by CFD codes local to the compute resource in use at the time. This naturally leads to a distributed database of results that will need to be federated as a coherent resource for the engineering community. We describe the use of Globus and Condor within Cambridge for sharing computer resources, progress on defining XML standards for the annotation of CFD datasets and a distributed database framework for them

A combined experimental and computational fluid dynamics analysis of the dynamics of drop formation

This article presents a complementary experimental and computational investigation of the effect of viscosity and flowrate on the dynamics of drop formation in the dripping mode. In contrast to previous studies, numerical simulations are performed with two popular commercial computational fluid dynamics (CFD) packages, CFX and FLOW-3D, both of which employ the volume of fluid (VOF) method. Comparison with previously published experimental and computational data and new experimental results reported here highlight the capabilities and limitations of the aforementioned packages