High Speed (50 kHz) Tomographic PIV System for 3D Measurements of Complex Unsteady Flows and Pressur
Abstract
This proposal request funding for components of a high speed (50 kHz) tomographic particle image velocimetry (PIV) system aimed at g,reatly enhancing our ability to probe complex flows. It will be used for measuring the unsteady 3D flow and pressure fields around s,hrouded naval propulsors and axial compressors, and in the inner part of high Reynolds number boundary layer over rough and complian,t walls. Experimental characterization of flow instabilities, turbulence, pressure fluctuations, unsteady forces, and radiated noise, in such systems is a major challenge owing to their three-dimensionality, unsteadiness, as well as scale and geometric complexity w,h, inception in propulsors, performance deterioration off design conditions in compressors, as well as an increase in drag and noise i,n rough and compliant wall boundary layers is quite limited. To address this challenge, and generate a complete experimental databas,e for elucidating the processes involved, the experiments at JHU are performed in a unique refractive index matched facilities, wher,e the refractive index of the acrylic rotor blades or rough walls are matched with that of the fluid, an aqueous solution of NaI. Th,ments using optical sensors everywhere within the sample volume. It includes the narrow tip gap in turbomachines, inside endwall cas,ing grooves aimed to suppress tip leakage cavitation inception or stall, and between sub millimeter roughness elements in the inner, part of a turbulent boundary layer. This facility has already been used extensively for characterizing a series of complex flows, p,roviding unique data and insight that cannot be obtained from any other source. So far, all the turbomachinery data and most of the, boundary layer data has been obtained using planar measurement techniques, such as stereo-PIV. Owing to limitations in the spatio-t,emporal resolution of our current decade-old system, our applications of tomographic PIV have been limited to low-speed flows, simpl,e geometries, and confined domains. The requested components include four state of the art high speed cameras (Phantom V2640) and a, dual-head laser (Laser Photonics Model DM100-532) needed for assembling a 50 KHz tomographic PIV system that will greatly enhance o,ur capabilities. By tracking e.g. well over 104 tracer particles in time while maintaining a spatial resolution of 200 m in a field, of view of 3.0x3.0x1.0 cm3, this system will enable us to perform time-resolved volumetric 3D velocity measurements at a spatio-tem,poral resolution sufficient for characterizing instabilities and unsteady vortical structures in the tip region of propellers and co,mpressors. Furthermore, it will enable us to calculate the distribution of material acceleration, and then integrate in spatially to, obtain the 3D pressure distribution at a resolution sufficient for: (i) elucidating the flow mechanisms affecting cavitation incept,ion in tip leakage flows of ducted propellers and potential mechanisms to suppress it involving e.g. casing treatment; (ii) measurin,ll as the effect of casing treatment aimed at suppressing the stall; (iii) after increasing magnification using microscopic digital, holographic microscopy, measuring the forces on roughness elements in the inner part of high Reynolds numbers turbulent boundary l,ayers; and (iv) characterizing the non-linear coupling between flow and wall deformation in compliant wall boundary layers. The unpa,ralleled data and insight derived from these measurements will greatly enhance our understanding and ability to model complex unstea,dy flows relevant to naval systems.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 13, 2022
- Source ID
- N000142212338
Entities
People
- Joseph Katz
Organizations
- Johns Hopkins University
- Office of Naval Research
- United States Navy