This proposal addresses subtopic 2.1.3 of the transformational tools and technologies (TTT) component of the 2018 NASA research announcement, benchmark experiments for CFD validation . A study of…

This federal contract award is a $599,220.19 cooperative agreement between Virginia Polytechnic Institute & State University (Virginia Tech) and the National Aeronautics and Space Administration (NASA) Shared Services Center. The agreement is funded under NASA's Transformational Tools and Technologies (TTT) component, specifically Subtopic 2.1.3 "Benchmark Experiments for CFD Validation".

The goal of the research is to produce detailed experimental data sets of smooth wall flows with separation that meet the exacting requirements for CFD validation. The 3-year effort will involve detailed measurements and calculations, including mean flow field, skin friction, velocity fluctuations, eddy viscosity, pressure fluctuations, and surface pressure statistics. This comprehensive dataset is intended to serve as a benchmark for validating CFD models of low Mach number, high Reynolds number turbulent boundary layer flows over bumps. The contract does not have a set-aside designation.

This proposal addresses subtopic 2.1.3 of the transformational tools and technologies (TTT) component of the 2018 NASA research announcement, benchmark experiments for CFD validation . A study of low mach number, high reynolds number flow of a plane turbulent boundary layer over bumps is proposed. The goal is to produce detailed experimental data sets of smooth wall flows with separation that, for the first time, meet the most exacting requirements of CFD validation as per oberkampf and smith (2017). To attain this goal, an intensive research program is proposed that brings together leading experts in experiments, computations and CFD validation. This effort will involve detailed measurements and calculations needed for full uncertainty quantification, experimental configuration design, and extensive documentation of the flow boundary conditions and boundary condition sensitivities. Detailed measurements on the bump flows will include the mean flow field, skin friction measurements, all second- and third-order velocity fluctuation moments, and eddy viscosity. Flow field pressure and pressure gradient fluctuations will be obtained simultaneously with instantaneous velocity to provide transport terms that include fluctuating pressure. Two point velocity correlations, and surface pressure fluctuation statistics and spectra will also be obtained. The proposed work is scheduled over a 3 year period: - year 1 will see the detailed characterization of the facility flow conditions and instrumentation. CFD simulation and collaborations with NASA and industry will determine the shape of the bump to be used and which flow conditions, measurement location and quantities need to be investigated. Finally, the experimental results will be used to perform a validation assessment of the CFD model of the flow in the empty wind tunnel. - year 2 will use the CFD model assessed in year 1 to determine the height of the bump required to produce fully attached flow, incipient separation and massively separated flow. The second bump will be tested in a manner similar to the first, and these experimental results will be used to further assess the CFD modeling. - year 3 will focus on further testing of the configurations with a view to investigate repeatability and reduce experimental uncertainty. This last test will also provide the opportunity to cover any flow sensitivity that may have been missed during years 1 and 2. Measurements will include mean pressure distributions on the test-section side walls, at least two planes of the inflow, mean and unsteady pressure measurements on the bumps, high-speed fluorescent particle image/particle tracking velocimetry, and laser doppler velocimetry. The scope required to conduct a rigorous, high reynolds number, benchmark validation study exceeds that described in the solicitation. The proposing team has obtained extensive additional support to close this GAP. Institutional support is provided by the crofton department of aerospace and ocean engineering at virginia tech, through the cost sharing of three months of effort by a post-doctoral researcher, 4.5 student years graduate student stipends, and over a month of technical support from a machinist. In addition, the virginia tech stability wind tunnel will perform many facility tasks and upgrades for conducting validation-quality studies at no cost to the project; and the stability tunnel will maintain and expand the capabilities and expertise developed as part of this work beyond the project end.