Experimental Study of the Spanwise Vortex Resonance Hypothesis for Turbulent DragReduction over a Flat Plate in Salt Water

摘要

A series of tests was conducted by the Naval Undersea Warfare Center (NUWC)Division, Newport, RI, to assess the effectiveness of utilizing magnetohydrodynamic (MHD) technology for turbulent drag reduction. Methodologies applied in previous experiments conducted by Princeton University and McDonnell Douglas Technologies Inc. (MDTI) were examined. The matrix of specific test cases used in these earlier experiments was repeated, and the Princeton/MDTI magnetic plate (instrumented with electrodes and magnets) was provided to NUWC for these tests. The electrodes were pulsed in a specific pattern using an electrical controller constructed by NUWC based on the algorithm provided by researchers at MDTI. The plate was placed in the NUWC water tunnel, and careful measurements of skin friction (using hot-film anemometry) and integrated drag were made. A drag balance was designed and constructed by NUWC specifically for these tests to assess Princeton's and MDTI's reports of drag reduction. The results obtained in the NUWC test series showed no integrated drag reduction based on force balance data. Analysis of the hot-film data showed skin friction reduction for only selected test cases. Detailed probability density function and spectral analyses were consistent with skin friction reduction. A future program for evaluating flow control by electromagnetic forces is offered.