The accurate and repeatable computational fluid dynamics (ccfd)-based prediction of turbulent flow separation relevant to off-design aerodynamic configurations remains an important challenge. There is…

This is a Cooperative Agreement between the University of Notre Dame DU Lac and the National Aeronautics and Space Administration (NASA) with a ceiling value of $602,617. The purpose of the agreement is to conduct three archival benchmark smooth body flow separation experiments to validate computational fluid dynamics (CFD) models for predicting turbulent flow separation, which is an important challenge in off-design aerodynamic configurations.

The experiments will be performed at Mach 0.2 to allow for validation of compressible CFD solvers without the need for low-speed preconditioning. The proposed two-dimensional geometry consists of a flat turbulent boundary layer development plate followed by a large convex ramp surface with an adverse pressure gradient controlled by an adjustable flexible top tunnel wall. This geometry is designed to allow for comprehensive measurements of mean and turbulence flow quantities, including third-order moments, to fully characterize the flow physics. The experiments do not have any set-aside designations and are intended to provide high-quality benchmark data to support improved CFD modeling of turbulent flow separation.

The accurate and repeatable computational fluid dynamics (ccfd)-based prediction of turbulent flow separation relevant to off-design aerodynamic configurations remains an important challenge. There is a clear need for improved models that can accurately capture the essential flow physics associated with smooth body (adverse pressure gradient generated) flow separation and reattachment. We propose three archival benchmark smooth body flow separation experiments that will be used for CFD validation. These include (1) attached smooth body APG turbulent boundary layer flow, (2) APG turbulent boundary layer flow with incipient separation, and (3) APG turbulent boundary layer separation with a large region of separated flow extending over a significant fraction of the smooth body surface. The experiments will be performed at m = 0.2 so that compressible CFD solvers may be validated without the need for low-speed preconditioning. Prior to application of the APG, the inflow condition is a nominally zero pressure gradient turbulent boundary layer with reynolds number = 7.8 million and a momentum thickness reynolds number = 11,750 which is maintained identical in each experiment. The proposed two-dimensional geometry is elegant and consists of a flat turbulent boundary layer development plate followed by a large convex ramp surface with APG controlled by a fully adjustable flexible top tunnel wall. This geometry should pose no difficulty in mesh generation and an outer flow velocity boundary condition is measured so that no changes in the computational grid are needed between the three APG cases. Furthermore, the ramp radius of curvature is very large compared to the boundary layer thickness so that curvature effects are negligible and flow separation is determined solely due to the imposed APG. The experiment is designed to allow profiles of mean and turbulent flow quantities to be obtained with high spatial resolution. The direct measurement of skin friction distribution via oil film interferometry allows these profiles to be scaled using either inner or outer variables. A full suite of measurements will be undertaken to completely characterize the evolution of both the mean and turbulence flow quantities including all third-order moments in the reynolds stress transport equation. A standard method of experimental uncertainty propagation analysis is applied to all measured quantities.