Supplemental to Development and Application of High-End Engineering and Planetary CFD Models

Computational fluid dynamics (CFD) is a discipline that is perpetually in search of greater computer power and better algorithms. This search has intensified as the phenomena studied with CFD models have expanded from traditional problems studied by aerospace engineers and meteorologists to more diverse designs and more demanding challenges. For instance, the CFD group at the University of Kentucky (UK) has worked on traditional challenges like simulating the flow through a turbine cascade [Suzen et aI, 2000] and on nontraditional ones like evaluating means for noise reduction in inkjet printers [Xiong et aI, 2000]. Likewise, the Comparative Planetology Laboratory (CPL) at the University of Louisville (UofL) has expanded high-resolution atmospheric modeling from terrestrial applications to planetary applications such as Venus, Jupiter [Showman & Dowling 2000J, and Neptune [LeBeau & Dowling 1998J. High computational-cost CFD problems typically are solved at national supercomputer centers or similar facilities with limited accessibility. However, CFD design problems of a practical nature fall into this class regularly, requiring large corporations and universities to purchase expensive shared-memory supercomputers such as those built by SGI and HP. The high up-front cost of CFD analysis places the technology beyond the reach of many mainstream engineers and researchers. Thus, many projects that would gain long-term economic advantages from CFD simulations never realize their potential. CFD code and system developers who find a practical way to tip the balance of this equation to affordable simulations will enjoy strong demand for their results. Even those organizations with substantial computer budgets, such as large laboratories, industries, and operational weather-forecasting centers, stand to gain measurably from significantly cheaper and more efficient means of performing CFD calculations. We propose to develop inexpensive, high-performance clusters of PCs, or "Beowulfs" [Becker, et aI, 1995J, specialized for CFD applications, using the novel approach that the hardware, operating system, and application code are optimized together rather than separately. We recognize that in the past few years some positive claims have been made in favor of PC clusters in which the hype was bigger than the performance of the actual systems. However, we will prove by construction that by expertly engineering the PC cluster design, using and building tools to improve application performance, and restructuring the application code for the cluster, it is possible to make grand-challenge-c1ass CFD modeling accessible and affordable to mainstream engineers, scientists, and industrialists. A powerful prototype of such a system (KLAT2) was built at UK this year for only $40,000. This approach will be applied to three operational CFD codes developed in Kentucky that serve a range of NASA thermo-fluids investigations. The first is OVERFLOW, an established CFD solver based on Reynolds-Averaged Navier-Stokes (RANS) turbulence models. The second is LESTool, a next-generation CFD model employing advanced turbulence modes. The third is EPIC (Explicit Planetary Isentropic-Coordinate), an atmospheric model used to study planetary atmospheres. Three research groups from UK and UoiL will combine their talents with colleagues at NASA Ames, Langley, and JPL to carry out this concerted, groundbreaking CFD development and application effort.