Three-Dimensional Separated Flows Around Inclined Bodies of Revolution
Abstract
SOW Three-dimensional flow separation and reattachment, which have substantial effects onhydrodynamic performance of maneuvering bodies, are a challenge to predict and control at high Reynoldsnumbers. The difficulties are associated with sensitivity of the location of separation and dimensions of theseparated region to pressure gradients, Reynolds number, boundary layer structure, surface roughness, andturbulence level. The primary objective of this joint effort with the University of Michigan, Navyresearchers, and several numerical groups, is to characterize of the flow around an inclined 3m long, 0.5 mdiameter, 6:1 prolate spheroid at a body length-based Reynolds number of 1.5x106 to 5x107, incidenceangles varying between 0 to 20, with and without boundary layer tripping. The measurements will beperformed in the Large Cavitation Channel. The second related objective involves the proper use oftripping to force early transition to turbulence and prevent premature laminar separation at moderateReynolds number. The placement and geometry of trips as well as their impact on the location andnature of flow separation around inclined axisymmetric bodies have not been established. Hence, aparallel study will characterize the flow and turbulence generated by trips at relevant adverse pressuregradient boundary layers.The LCC tests involve two stereo particle image velocimetry (SPIV) systems. High-resolutionmeasurements of the mean flow and Reynolds stresses in the boundary layer upstream, at, and downstreamof the separation line will be performed using a miniature system installed inside the model. Theresolution of mean flow profiles will b affectingtransition from close to open separation, and tripping effects. The optical setup includes internal cameras,microscopic imaging through curved boundaries requiring extensive calibrations, fiber-guided illuminationand data transmission, as well as local seeding. A 2nd SPIV system, which will be based on adaptingavailable instrumentation, will be submerged behind the model to measure the evolution of mean flow andReynolds stresses in axial planes covering the separated region. Data analysis will evaluate the effects ofReynolds number, tripping method, and incidence angle on the wake structure and turbulence. The purchaseand manufacturing of equipment will take place in early FY 21, leaving less than eighteen months for testingand calibration of the instruments until the middle of FY 22. The measurement campaigns will take placein FY 22 and FY 23. The measured data will be complemented by LES performed by another group,which uses an adjoint-based method to infuse the experimental data into the simulations to minimizethe differences between them. This procedure will provide an unprecedented detailed view of 3Dseparation around the prolate spheroid.The parallel study will characterize the effect of tripping on the location and nature of flowseparation in an adverse pressure gradient boundary layer under relevant conditions. The experimentswill be performed in the JHU refractive index matched water tunnel in a setup that enables 3D timeresolvedvelocity, pressure and wall stress measurements, from the trip to the point of separation. Thecompletely characterized flow field will be instrumental for interpreting trends of the flow around the6:1 prolate spheroid, and for guiding the selection of the type and placement of the trips. Hence,preliminary SPIV measurements will be completed prior to the LCC campaign to assist in theselection of tripping strategy for the prolate spheroid. Subsequently, 3D time resolved tomographics, trip location, and configuration.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 15, 2021
- Source ID
- N000142112046
Entities
People
- Joseph Katz
Organizations
- Johns Hopkins University
- Office of Naval Research
- United States Navy