Research on the Structure of Complex 3-D Turbulent Flows Using the Comprehensive Laser-Doppler Velocimeter

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

PROPOSAL NO.: CBET - 0730774 PRINCIPAL INVESTIGATOR: SIMPSON, ROGER L. INSTITUTION: VIRGINIA POLYTECHNIC INSTITUTE AND STATE UNIVERSITY NANOFLUIDICS OF SURFACE-DRIVEN LIQUID FLOW AND ITS APPLICATION FOR NANOFABRICATION In this research program, the new comprehensive laser-Doppler velocimeter (CompLDV) experimental technique will measure simultaneously and precisely the instantaneous vector velocity, acceleration, and position of submicron-sized particles within the Kolmogorov scales of high Reynolds number 3-D turbulent flows at a high data rate of at least 100,000 samples per second. The CompLDV novel design superimposes converging and diverging fringe patterns to determine the 3-D location of a given particle passing through the 200 micron diameter measurement volume within 5 microns uncertainty. Measurements can be made within 5 microns of a solid wall to determine the surface skin friction. For 3-D flows, these transport equations are required to account for: (1) the variable anisotropy of the eddy viscosities, (2) the lags between the mean flow and the turbulence field, and (3) the strong relation between the important shearing stresses and velocity fluctuations (Simpson, 1996). Work planned here will examine the horseshoe vortex structure for this wing/body test case flow and for a vortex generator flow to provide quantitative data to better explain and model the 3-D turbulence structure of embedded mean stream-wise vortices common in practical applications. In addition, in this research experimental statistical information on the global unsteadiness of the flow and the length scales of the various sized eddies are needed and will be obtained using multi-point LDV measurements to compare with large-eddy simulations (LES), These data and results will be shared with European Research Community on Fluids, Turbulence and Combustion (ERCOFTAC) and other collaborators. The broader impacts of this planned research advances discovery and understanding and enhances the infrastructure of turbulence research by continuing to develop a new type of instrument that can provide fundamental low uncertainty information for the first time on the turbulence energy dissipation rate and the velocity/pressure-gradient correlation and other previously unmeasured quantities for well-defined high Reynolds number three-dimensional turbulent boundary layers. Collaborations between the PI and turbulence modelers have already been established. The planned graduate student will interact with these researchers also in helping to develop turbulence models from the data. Graduate students from Germany and other modeling researchers are expected to be involved in the discussions of these results. The knowledge and insights gained from the planned three-dimensional flows will permit more credible models for the velocity/pressure-gradient correlation and dissipation rate at high Reynolds numbers, which are needed for weather prediction and better estimates of the turbulence generated aero-acoustic noise sources.