Soon-Heum Ko

Development of cactus driver for CFD analyses in the grid computing environment

The Grid Computing[1] has been paid much attention from researchers as an alternative to parallel computing for its unlimited number of potential resources available and as an easier way to build collaborative environments among multiple disciplines. However, the difficulty in establishing the environments and accessing and utilizing the resources has prevented application scientists from using Grid computing. Thus, the present study focuses on building PSE(Problem Solving Environment) which assists application researchers to easily access and utilize the Grid. The Cactus toolkit, originally developed by astrophysicists, is used as a base frame for Grid PSE. Some modules are newly developed and modified for CFD(Computational Fluid Dynamics) analysis. Simultaneously, a web portal, Grid-One portal, is built for remote monitoring/control and job migration. Cactus frame through the web portal service has been applied to various CFD problems, demonstrating that the developed PSE is valuable for large-scaled applications on the Grid.

e-AIRS: Construction of an Aerodynamic Integrated Research System on the e-Science Infrastructure

e-AIRS, an abbreviation of ‘e-Aerospace Integrated Research System’, is a virtual organization designed to support the aerospace engineering processes in the e-Science environment. As the first step toward a virtual aerospace engineering organization, the e-AIRS intends to give a full support to aerodynamic research processes. Currently, the e-AIRS can handle both the computational and experimental aerodynamic researches on the e-Science infrastructure. In detail, users can conduct the full CFD(Computational Fluid Dynamics) research processes, request wind tunnel experiments, perform the comparative analysis between computational and experimental resultants and finally collaborate with other researchers using the web portal. The current paper will describe those functions and the internal architecture of the e-AIRS system

Separation Analysis of Strap-ons in the Multi-stage Launch Vehicle Using the Grid Computing Technique

A numerical technique for simulating the separation dynamics of strap-on boosters is presented. Six degree of freedom rigid body equations of motion are integrated into the three-dimensional unsteady Navier-Stokes solution procedure to determine the dynamic motions of strap-ons. An automated Chimera overset mesh technique is introduced to achieve maximum efficiency for the relative motion of multiple bodies and each mesh is constructed as multi-block mesh for the representation of the after-body flow. Additionally, a new computing concept, called ‘the Grid computing technique’[1,2], is adopted to guarantee sufficient computing resources and a simple load balancing technique is proposed for an efficient computation in the Grid. As a validation of Chimera mesh technique implementation, computed results around the Titan IV launch vehicle is compared with experimental data and, as a validation of base flow analysis, the aerodynamic coefficients of a strap-on booster of KSR-Ⅲ is analyzed numerically. The complete analysis process is then applied to the KSR-Ⅲ, a three-stage sounding rocket researched in Korea. From the analyses, the base flow effect on separation motions of strap-on boosters are investigated and the different aerodynamic characteristics of inviscid and viscous flows at every time interval are examined. In addition, a guidance map of the jettisoning forces and moments for a safe separation is presented from various simulations of separation phenomena with different jettisoning conditions. Keyword : Separation Motion of Strap-on Boosters, Chimera Overset Mesh, The Grid, Base Flow

Separation Motion of Strap-On Boosters with Base Flow and Turbulence Effects

The authors would like to acknowledge the computing support of the Korea Institute of Science and Technology Information (KISTI) under “The Sixth Strategic Supercomputing Support Program,” with Kum Won Cho as the technical supporter. Also, the authors would like to acknowledge the financial support of the Bain Korea-21 program for the School of Mechanical and Aerospace Engineering Research at Seoul National University and the Korea National e- Science project.

CFD Analyses on Cactus PSE

Publisher Summary The chapter applies Cactus problem solving environment (PSE) to the analysis of computational fluid dynamics (CFD) problems. A specialized computer system that offers computational conveniences required for a specific problem is called PSE and, nowadays Nimrod/G, Triana, and Cactus are actively applied. From the understanding of the structure of Cactus, researchers developed CactusEuler3D arrangement, with general coordinate I/O routine that can utilize body-fitted coordinate in the Cactus frame. A Cactus-based CFD solver is validated by the analysis of the flow field around the wing. From these researches, Cactus PSE is shown to be applicable to CFD analysis and the possibility of multidisciplinary collaboration by Cactus framework is presented in the chapter. Simultaneously, the construction of computational environment, including the efficient visualization, job migration, and portal service are researched and successfully implemented. Eventually, those computational supporting environments with CFD solver on the Cactus framework will help the CFD researchers use the advanced computing technologies.

A Grid-based Flow Analysis and Investigation of Load Balance in Heterogeneous Computing Environment

Publisher Summary This chapter discusses the Grid-based flow analysis. The grid is a communication service that collaborates dispersed high performance computers so that they can be shared and used together. It enables the analysis of huge-sized problems with the reduction of computation time by collaborating high-performance computing resources in dispersed organizations. Thus, it focuses on the efficient flow calculation in the Grid. For large-scale computation, the separation motion of boosters attached on the multi-stage launch vehicle is analyzed by using 3D compressible unsteady Navier-Stokes flow solver and rigid body dynamics. Simultaneously, a simple load balance algorithm for heterogeneous computing environment is proposed and applied to a 3D problem that uses a multiblock mesh. Various possible applications of the Grid computing environment to CFD problems are investigated in the present discussion. For a precise analysis, base flow region is included in the computational domain.

Load Balancing for CFD Applications in Grid Computing Environment

The Grid is a communication service that collaborates dispersed high performance computers so that those can be shared and worked together. It enables the analysis of large-scale problem with the reduction of computation time by collaborating high performance computing resources in dispersed organizations. Thus, the present paper focuses on the efficient flow calculation using the Grid. To increase parallel efficiency, a simple load balance algorithm for the Grid computing is proposed and applied to various aerodynamic problems.

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