Direct Measurements of Dissipation Rate and Determination of the Velocity/pressure-gradient Correlation in Complex High Reynolds Number Turbulent Flows

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PROPOSAL NO.: CTS-0233653PROPOSAL TYPE: INVESTIGATOR INITIATEDPRINCIPAL INVESTIGATORS: ROGER L. SIMPSONINSTITUTION: VIRGINIA POLYTECHNIC INST. DIRECT MEASUREMENTS OF DISSIPATION RATE AND CORRELATIONS IN COMPLEX TURBULENT FLOWSThere is a clear need to greatly improve turbulent flow models for practical three-dimensional high Reynolds number turbulent flows in order to facilitate development of robust and accurate computational tools. Improvements will have a great impact on the design calculations of all fluid machinery, including aircraft, submarines, jet engines, etc. as well as the prediction of atmospheric and ocean flows. Some terms in the governing Reynolds-averaged equations used in many models have never been directly measured and the underlying theoretical ideas are highly uncertain.This program will provide a major experimental breakthrough. A newly designed type of laser-Doppler velocimeter is being used and further developed that can determine instantaneously the three components of position, velocity, and acceleration of multiple particles that follow the flow within a 200 micron measurement volume. Not only will the instantaneous position of the particles be determined to within 1 micron (0.00004 inches) uncertainty, but the instantaneous rate-of-deformation and angular velocity of the flow will be obtained, leading to the determination of the instantaneous values of important terms in the fundamental equations. The information is important for improved turbulence modeling. The experimental technique will be used to obtain data for three fundamental building block flows: 2-D flat plate zero mean pressure gradient boundary layers (momentum thickness Reynolds number in the range 7,000 to 23,000), two-dimensional turbulent boundary layers with isolated roughness, and three-dimensional rough-wall boundary layers. The experimental results from this proposed research will be the first available data sets with complete measurements of all turbulent quantities in the Reynolds-averaged modeling equations at relatively high Reynolds numbers. This research will have a number of broad impacts. Significant interaction and collaboration with turbulence modelers is planned, which will broadly disseminate the results for enhanced scientific and technical understanding. Other broad impacts are the education of US undergraduate and graduate students in the use of this cutting-edge research technique, significant contributions to research infrastructure by developing a new instrument, and benefits to society through advancements in turbulence modeling for practical applications.