. "Near-and Far-Field CFD for a Naval Combatant Including Thermal-Stratification and Two-Fluid Modeling." Twenty-First Symposium on Naval Hydrodynamics. Washington, DC: The National Academies Press, 1997.
The following HTML text is provided to enhance online
readability. Many aspects of typography translate only awkwardly to HTML.
Please use the page image
as the authoritative form to ensure accuracy.
Twenty-First Symposium on NAVAL HYDRODYNAMICS
which must be addressed. By using systematic verification analysis, numerical uncertainties can be made relatively small. However, improvement in numerics is required, particularly, efficiency and accuracy. Modeling uncertainties are daunting and their estimation requires EFD validation data which, unfortunately, is very difficult to obtain. For single-phase flow, modeling uncertainty is due to geometry, turbulence, wave-breaking, and free-surface boundary conditions. In contrast, there are many areas of concern for two-phase flow. The accumulation of bubbles in the boundary layer suggests that other possible mechanisms of interfacial momentum and mass transfer may be important in this region, such as bubble-bubble collision and interfacial pressure, Einstein forces, dissolution, and breakup. Some of these models will require incorporation of an approach to handle polydisperse bubble populations: a formidable computational challenge.
To accurately predict bubbly-wake signatures, much future work remains. For the near-field RANS, farther improvements in both numerics and models will be made in conjunction with work on more complex single-phase flows, e.g., unsteady flow. Also, capability to resolve appendages, calculate sinkage and trim, and employ more sophisticated propeller-hull interaction methods must be incorporated. The lack of strong thermal-hydrodynamic interaction suggests that a variety of common and in-situ temperature profiles be studied. In certain environments, salinity fields may need to be included in the transport and density calculations. Finally, work on two-fluid modeling will focus on extending the method for nonzero Fr, development of a coupled multigroup scheme to calculate bubble-size distribution, including bubble breakup and dissolution, and inclusion of propulsor effects on the bubble size distribution.
ACKNOWLEDGMENTS
This research was sponsored by Office of Naval Research Grants N00014 –93–1–0052 (Iowa), N00014–96-AF00002 (NSWC CSS), and N00014–91-J-1271 (RPI) under the administration of Dr. E.P. Rood. The computations were performed on the Naval Oceanographic Office, NASA Numerical Aerodynamic Simulation Program, and San Diego Supercomputer Center supercomputers. The assistance of Dr. Rood and Ms. Margo Frommeyer is especially acknowledged.
REFERENCES
1. Tahara, Y. and Stern, F., “A Large-Domain Approach for Calculating Ship Boundary Layers and Wakes for Nonzero Froude Number”, Proc. of the CFD Workshop, Tokyo, March, 1994; also, to appear Journal of Computational Physics.
2. Stern, F., Kim, H., Zhang, Z., Toda, Y., Kerwin, J. and Jessup, S., “Computation of Viscous Flow around Propeller-Body Configurations: Series 60 CB=0.6 Ship Model, Journal of Ship Research, Vol. 38. No. 2, June, 1994
3. Bonetto, F., Drew, D., and Lahey, R.T., “A Numerical Simulation of a Turbulent Two-Phase Jet Using a Multidimensional Two-Fluid Model,” in review, International Journal of Numerical Methods in Fluids.
4. Carrica, P., Bonetto, F., Drew, D., and Lahey, R.T., “Gas-Liquid Two-Phase Flow Around a Ship,” in preparation, International Journal of Multiphase Flow.
5. Lahey, R.T., and Drew, D.A., “The Current State-of-the-Art in Modeling of Vapor/Liquid Two-Phase Flows,” ASME paper 90-WA/HT-13, 1990.
6. Smith, R.W., and Hyman, M., “Convective-Diffusive Bubble Transport in Ship Wakes,” NCSCTN 857–87, 1987.
7. Hyman, M., “Modeling Ship Microbubble Wakes,” CSS/TR-94/39, 1994.
8. Hyman, M., Influence of Temperature Stratification On The Development of Surface Ship Micro-Bubble Wakes,” NCSCTN 1017–90, 1990.
9. Stern, F., Paterson, E., and Tahara, Y., “CFDSHIP-IOWA: Computational Fluid Dynamics Method for Surface-Ship Boundary Layers, Wakes, and Wave Fields,” IIHR Report 666, Iowa City, Iowa, Februrary 1996.
10. Lopez de Bertodano, M., “Turbulent Bubbly Two-Phase Flow in a Triangular Duct,” Ph.D. Thesis, Rensselaer Polytechnic Insitute, Troy, NY, 1992.
11. West, E.E., “Reisitance Characteristics and Appendage Orientation Data for DE 1052 Represented by Model 4989,” DTNSRDC/SPD-C-011_H01, Unclassified 3/13/81, September 1964.
12. Day, W.G.Jr. and Hurwitz, R.B., “Propeller-Disk Wake Survey Data for Model 4989 Representing the FF 1052-Class Ship in a Turn and with a Bass Dynamometer Boat,” DTNSRDC/SPD-0011–21, December 1980.
13. Ratcliffe, T., and Lindenmuth, W.T., “Kelvin-Wake Measurements Obtained on Five Surface Ship Models,” DTRC-89/038, 1990.
