Experimental characterization of Non-Linear Interactions of a Compliant Wall with a Turbulent Boundary Layer
Abstract
The objective of this experimental study is to characterize the non-linear interactions of high Reynolds number turbulent boundary layers with compliant walls, and the resulting radiation of dipole noise from the deformable interface. The focus is on cases involving two-way coupling between the flow and the compliant coating, namely when the flow-induced wall deformations are large enough to modulate the flow and turbulence in the inner part of the boundary layer. To maximize the surface response, theoretical predictions are used for matching the compliant layer thickness and properties with those of the boundary layer. The experiments will be performed in the recently-constructed stable water tunnel extension to the JHU refractive index-matched facility, utilizing a unique suite of integrated instruments that simultaneously measure the timeresolved 3D flow structure and pressure distribution in the boundary layer along with the spatial distribution of surface deformation. The surface deformation is mapped at high resolution using Mach Zehnder Interferometry (MZI). The velocity and acceleration measurements are performed using tomographic particle image velocimetry (TPIV), augmented by particle tracking forenhancing the spatial resolution of the data. The time-resolved pressure distribution is computed by spatially integrating the of material acceleration utilizing in-house codes that minimize the effects of experimental errors. The dipole noise radiated from the surface is determined by integrating the pressure distribution and its time derivatives. The proposed studies are guided byrecent measurements showing that in cases of two-way flow-deformation coupling, the nearinterface profiles of mean velocity and Reynolds stresses differ substantially from those of smooth or rough wall boundary layers. Specifically, the wall-deformation waves with an amplitude of several wall units cause a sharp decrease in mean velocity and a substantial increase in turbulence and shear stresses in the inner part of the boundary layer. Accordingly, we propose to: (i) Elucidate the observed phenomena by performing simultaneous measurements of time-and spatiallyresolved deformation, 3D flow structure, pressure, and dipole noise for a variety of flow and wall properties. The two-way coupled flow-deformation interactions and associated scaling trends will be quantified by statistical data analysis involving correlations and conditional sampling. (ii) Characterize the wall deformations, boundary layer structure, pressure, and noise in regions of inhomogeneities and discontinuities in the properties of the compliant wall. Included are steps, gaps, and tailored strips of compliant wall properties that differ from those of the surroundingsurface. Based on theoretical modeling, the thickness, length, and properties of these strips will be selected to maximize or potentially suppress the interactions with the boundary layer. (iii) Measure the attenuation of the pressure fluctuations as they propagate across the compliant surface, focusing in particular on non-linear flow-deformation interactions, and compare the results to theoretical predictions, which are based on linear analysis.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 24, 2019
- Source ID
- N000141912096
Entities
People
- Joseph Katz
Organizations
- Johns Hopkins University
- Office of Naval Research
- United States Navy