Jae Wan Ahn

Web-Based Integrated Research Environment for Aerodynamic Analyses and Design

e-AIRS[1,2], an abbreviation of ‘e-Science Aerospace Integrated Research System,’ is a virtual organization designed to support aerodynamic flow analyses in aerospace engineering using the e-Science environment. As the first step toward a virtual aerospace engineering organization, e-AIRS intends to give a full support of aerodynamic research process. Currently, e-AIRS can handle both the computational and experimental aerodynamic research on the e-Science infrastructure. In detail, users can conduct a full CFD (Computational Fluid Dynamics) research process, request wind tunnel experiment, perform comparative analysis between computational prediction and experimental measurement, and finally, collaborate with other researchers using the web portal. The present paper describes those services and the internal architecture of the e-AIRS system.

Use of e-Science Environment on CFD Education

‘e-Science’ represents the global collaborations of people and shared resources to solve new and challenging problems in science and engineering (Hey & Trefethen, 2003) on the basis of the IT infrastructure, typically referred to as the Grid (Foster & Kesselman, 1999). As we can easily infer, e-Science initially meant a virtual environment where a new and challengeable research can be accomplished using latest infrastructures. That virtual environment usually has a form of a web portal page or an independent application with a bunch of computer scientific components inside: high-end application researches include large-scale computations for complex multi-physical mechanisms, coupled works of computation and experiments for design-to-development processes, and/or data-intensive researches. The infrastructure consists of computational and experimental facilities, valuable datasets, knowledge, and so on. Researchers can be referred to as a core component of e-Science environment as their discussions and collaborations are promoted by, managed by and integrated to the environment. Meanwhile, the meaning of ‘e-Science’ is becoming broader nowadays. Though e-Science first intended to enrich high-end research activities, it is soon proven to be also effective on academic activities as a cyber education system. (On the other hand, use on inter-disciplinary collaborative researches is not much vitalized as expected, because of diverse preference on internal workflow, I/O and interface among research domains.) Thus, the term ‘e-Science’ is rather used to represent ‘all scientific activities on high performance computing and experimental facilities with the aid of user-friendly interface and system middleware’ these days. As a virtual academic system for aerospace engineering, ‘e-AIRS’ (e-Science Aerospace Integrated Research System) has been designed and developed since 2005. After three years’ development, e-AIRS educational system is finally open, where non-experts can intuitively conduct the full process of computational and experimental fluid dynamic study. Also, the

The Slip-Wall Boundary Conditions Effects and the Entropy Characteristics of the Multi-Species GH Solver

Starting from the Eus GH(Generalized Hydrodynamic) theory, the multi-species GH numerical solver is developed in this research and its computatyional behaviors are examined for the hypersonic rarefied flow over an axisymmetric body. To improve the accuracy of the developed multi-species GH solver, various slip-wall boundary conditions are tested and the computed results are compared. Additionally, in order to validate the entropy characteristics of the GH equation, the entropy production and entropy generation rates of the GH equation are investigated in the 1-dimensional normal shock structure test at a high Knudsen number. 초 록

Hypersonic Rarefied Flow Simulations Using the Generalized Hydrodynamic Equations for Multi-species Gases

*† ‡ On the basis of the Eu’s generalized hydrodynamic (GH) theory for diatomic gas and multi-species gas, computational models are developed for the numerical simulation of hypersonic rarefied gas flows. The rotational non-equilibrium effect of diatomic molecules is taken into account by introducing excess normal stress associated with the bulk viscosity. Starting from the development of the diatomic GH computational model, the multi-species GH theory is applied to a multi-species gas including 5 species; O2, N2, NO, O, N. Two kinds of GH theories (diatomic GH model for single species gas and multi-species GH model for monatomic gas) are combined to derive the general formulation of the multi-species GH theory considering collision between monatomic and diatomic molecules. The multi-species GH model includes diffusion relation due to the molecular collision and thermal phenomena. Two kinds of GH models are developed for an axi-symmetric flow solver. By comparing the computed results of diatomic and multi-species GH theory with those of the Navier-Stokes equations and the DSMC results, the accuracy and physical consistency of the GH computational models are examined.

Numerical Analysis of Hypersonic Flow over a Double-Cone Geometry Using Eu's GH Equations

Eus GH(Genera1ized Hydrodynamic) equations are presented for analyzing a hypersonic flow over a double-cone geometry which shows various aerodynamic phenomena such as shock-shock interaction, shock-boundary layer interaction, etc. In order to analyze rarefied hypersonic flow, axisymrnetric generalized hydrodynamic equations are developed and validated by Rothe nozzle flow problem. Two kinds of solid surface boundary conditions nonslip and Langmuirs slip BC are examined, too. The hypersonic rarefied flow results acquired by GH equations are compared with experimental data and Navier-Stokes equations calculations with slip and nonslip boundary conditions. The calculations by GH equations show the more accurate flow predictions than those of NavierStokes equations, and GH equastion with some assumptions was able to be found that it is a useful tool to analyze rarefied hypersonic flows.