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Browsing by Author "Wosnik, Martin"

Now showing 1 - 3 of 3
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    Experimental and Numerical Investigation of Large Scale Structures in Cavitating Wakes
    (American Institute of Aeronautics and Astronautics, 2006-06) Arndt, Roger E.A.; Wosnik, Martin
    Cavitation is a design consideration for a broad variety of devices handling liquids. In many cases, unstable operation is caused by cavitation-induced flow instabilities. Complex cavitation characteristics are observed in many types of fluid machinery. Examples range from the high- pressure fuel pumps in the Space Shuttle Main Engine to a variety of hydroturbines. In addition there is an increasing interest in very high performance marine vehicles that must operate in the cavitating regime. Associated with the deleterious effects of performance breakdown, noise, and vibration, there is a possibility of erosion. The purpose of this research is to investigate the two- phase flow structure in the wake of a hydrofoil undergoing unsteady partial cavitation using an integrated experimental/numerical approach. This topic provides both numerical and experimental challenges. A two-dimensional NACA 0015 hydrofoil was selected for study, because of its previous use by several investigators around the world. The simulation methodology is based on a Large Eddy Simulation (LES), using a barotropic phase model to couple the continuity and momentum equations. The complementary experiments were carried out at two different scales in two different water tunnels. Tests at the St. Anthony Falls Laboratory (SAFL) were carried out in a 0.19x0.19m2 water tunnel and a geometrically scaled up series of tests was carried out in the 0.3x0.3 m2 water tunnel at the Versuchsanstalt für Wasserbau (VAO) in Obernach, Germany. The tests were designed to complement each other and to capitalize on the special features of each facility.
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    Investigation of a Low-Drag Partially Cavitating Hydrofoil: Water Tunnel Tests
    (St. Anthony Falls Laboratory, 2003-09) Hansberger, Jon; Wosnik, Martin; Wang, Hong; Arndt, Roger E.A.
    This project is based on a request made to the Saint Anthony Fall Laboratory by Dr. Eduard Amromin on behalf of Mechmath, Inc. The work was performed under a sub-contract as part of a Phase I SBIR contract with the Defense Advanced Research Projects Agency (DARPA). Details of the design are supplied in the progress report from Mechmath and Amromin et al (2003). This hydrofoil is designed to take advantage of the drag reduction that would be possible with a stabilized cavity on the suction side of the profile. In the configuration currently under review the suction side is on the lower surface, hence the design is optimized for negative angles of attack. Figure 1.2 depicts the theoretical pressure distribution at angle of attack -3o.
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    Testing of a 1:6 Scale Physical Model of the Large, Low-Noise Cavitation Tunnel (LOCAT)
    (St. Anthony Falls Laboratory, 2006-11) Wosnik, Martin; Arndt, Roger
    As part of the conceptual and detailed design phases leading to the construction of the LOw Noise Large CAvitation Tunnel (LOCAT) at the Maritime and Ocean Engineering and Research Institute (MOERI) of the Republic of Korea, an experimental analysis and verification of the design was carried out at the St. Anthony Falls Laboratory (SAFL). This report describes pressure and velocity measurements performed at a 1:6 scale physical model at SAFL using air as a working fluid. The physical model is used to check the overall flow quality, including measurements of pump inflow, and to investigate contraction, diffuser and turning vane performance. High spatial resolution mean velocity and turbulence profiles were taken at 44 locations in the model, and mean pressure was measured at 183 locations. Here these results are summarized, and recommendations are made based on the experimental observations. The results of the physical model can be used for comparison to numerical simulations at model Reynolds number, which can then be extrapolated to prototype Reynolds numbers to predict the performance of the full scale LOCAT.