1 A PERSPECTIVE ON NAVAL HYDRODYNAMIC FLOW SIMULATIONS 1 A. Arabshahi, M. Beddhu, W.R. Briley, J.P. Chen, A. Gaither, K. Gaither, J.M. Janus, M. Jiang, D. Marcum, J. McGinley, R. Pankajakshan, M. Remotigue, C. Sheng, K. Sreenivas, L.K. Taylor, and D.L. Whitfield Computational Fluid Dynamics Laboratory NSF Engineering Research Center Mississippi State University ABSTRACT A perspective of computational hydrodynamics is presented that is considered relevant to particular Naval hydrodynamic problems. This is not intended as a survey of the field in general; rather, it is a summary of the ongoing research and development of computa- tional tools in the Computational Fluid Dynamics Lab at Mississippi State University. A discussion is given of the enabling technologies on which most of the computa- tional tools are based. Example results are presented for submarines, surface ships, and propulsors, that at- tempt to illustrate the current status of certain Naval hydrodynamic computational capabilities. Some ob- servations and comments are offered relating to various needs and possible directions of future computational hydrodynamic research and development. 1.0 INTRODUCTION This invited paper deals primarily with the development and application of Reynolds Averaged Navier–Stokes (RANS) codes to Naval hydrodynamic problems. The paper discusses some of the computa- tional tools being developed in the CFD Lab that can be brought to bare on these hydrodynamic problems, and it also attempts to address some interesting but difficult underlying questions related to an assessment of present and future computational fluid dynamics (CFD) capabil- ities and requirements. Recent increases in computer speed have not reduced typical runtimes for complex or advanced simu- lations, primarily because decreases in computer memory cost have increased the memory available, which in turn has made it possible to obtain numerical NASA Langley Research Center. This support is gratefully This research was lead and sponsored by Dr. Pat Purtell and Dr. Edwin Rood of the Office of Naval Research. Some of the acknowledged. 1 research that is being leveraged into this hydrodynamic area was also sponsored by Dr. Kyle Anderson and Dr. Jim Thomas of the solutions to larger and far more complicated problems. The emergence of parallel computing is providing large global memory and runtimes which are reduced by mul- tiple processors, and this is also enabling the solution of larger and even more complicated problems. Three–di- mensional computations are now being performed rath- er routinely. In many cases, these computations have been and are being performed for either isolated compo- nents of complicated configurations or for steady state flows, and usually for both. Parallelization is now mak- ing it possible to obtain some reasonable measure of turnaround time for complete configurations in which all components are accounted for in their true interaction mode, and in some cases this is being done for both steady and unsteady flow situations. The complexity of flow configurations that are feasible will continue to in- crease, and along with this will come the need to address widely–varying time and length scales in the same physical problem. This, in turn, will invite further ad- vances in both solution methodology, computer hard- ware and computational software. The present paper is not intended as a survey of CFD for Naval hydrodynamics. Rather, it is primarily a summary of ongoing research in the CFD Laboratory of the NSF Engineering Research Center at Mississippi State University and through its associations with other agencies within the Navy, NASA, and Air Force. Some of the enabling technologies that have contributed to the development of certain hydrodynamic tools are first briefly reviewed in Section 2. Example results are then presented in Section 3 for simulations related to subma- rines, surface ships, and propulsors. Section 4 then of- fers some observations and comments relative to an as- sessment and suggested direction of CFD for Naval hydrodynamics. This section should be considered for no more than what it is, namely the opinions of the au- thors. Some conclusions are drawn in Section 5. 2.0 ENABLING TECHNOLOGIES This section reviews briefly the technologies that form the basis for the tools used for the computa- tional hydrodynamics results presented in the following