Projects (out of date, updates coming soon)
Planned CRM-HLS test article.
Turbulent separated flows
The engineering simulation of turbulent separated flows remains challenging due, in part, to a lack of validation data needed to qualify new turbulence models. In aid of NASA’s CFD 2030 goals and in collaboration with with Boeing Company, we have undertaken the study of a newly proposed validation test case for turbulent separated flows. This geometry is three-dimensional, to minimize interactions with tunnel side walls, and incorporates the wind tunnel confinement in its definition. Results of initial studies on this geometry will be presented at SciTech 2020.
Now entering Phase II, this project will undertake detailed flowfield measurements using PIV. Stringent wind tunnel certification and uncertainty quantification will allow careful comparison between simulations using a wide range of turbulence models.
Publications:
O. Williams and A.J. Smits, “Asymmetries in nominally symmetric flows”, Annual Reviews of Fluid Mechanics
K. Manohar, H. Annamalai, O. Williams, C. Morton, R. Martinuzzi, “Unsteadiness in turbulent separated flow over a three-dimensional Gaussian Bump”. ArXiv, Submitted.
O. Williams et al. “Definition of a Simplified, Low-Cost, Constant Cross-Section High-Lift Wing Configuration Based on the Common Research Model (CRM-HLS)“ AIAA AVIATION.
K. Manohar, O. Williams, R. Martinuzzi, C. Morton, “Sensor-based temporal super-resolution for turbulent separated flows,”Experiments in Fluids.
O. Williams, H. Annamalai, T. Ozoroski, C. Roy, T. Lowe, “Comparison of hill-type geometries for the validation and advancement of turbulence models,” SciTech 2022, AIAA.
O. Williams, M. Samuell, M.Robbins, H. Annamalai, A. Ferrante (2021), “Characterization of separated flowfield over Gaussian speed-bump CFD validation geometry,” SciTech 2021, AIAA.
M.Robbins, M. Samuell, H. Annamalai, O. Williams (2021), “Overview of validation completeness for gaussian speed-bump separated flow experiments ,” SciTech 2021, AIAA.
O. Williams, Madeline Samuell, Sage Sarwas, Matthew Robbins and Antonino Ferrante (2020), “Experimental study of a CFD validation test case for turbulent separated flows,” SciTech 2020, AIAA
Datasets: Surface pressure on Speed Bump
Funded by the Boeing Company
Snortland et al (2019), EWTEC
Applications of unsteady foil aerodynamics
We are examining the effects of Reynolds number, blade geometry, array blockage, variable velocity control, and tip-speed ratio on cross-flow turbine hydrodynamics and performance. It is essential we link the unsteady flow structure around each turbine blade to overall turbine performance so that we can further optimize the control and configuration of future designs for maximum power production and reliability.
Publications:
A. Snortland, A. Hunt, A. Athair, O. Williams, B. Polagye, “Influence of the downstream blade sweep on cross-flow turbine performance,” Journal of Renewable and Sustainable Energy.
A.Athair, C. Consing, J. Franck, O. Williams, “Impacts of blade camber on cross-flow turbine performance and loading“, Wind Energy.
S. Hartke, A. Athair, O. Williams, J. Franck, “Dynamics of intracycle angular velocity control applied to cross-flow turbines”, Journal of Renewable and Sustainable Energy.
A. Snortland, K. Van Ness, J. Franck, A. Athair, O. Williams, B. Polagye, “Experimental identification of blade-level forces, torque, and pitching moment for cross-flow turbines,” Physical Review Fluids.
A. Hunt, A. Athair, O. Williams, B. Polagye, “Experimental validation of a linear momentum and bluff-body model for high-blockage cross-flow turbine arrays, Physical Review Fluids, 10.
Funded by NAVFAC, ARPA-e, DOE
In collaboration with Brian Polagye, PMEC.
From Williams et al (2018), JFM
Hypersonic Turbulence and Shock Interactions
Full description of ongoing efforts is coming soon.
Publications:
E. Jennis, L. Jones, O. Williams, “Thermodynamic Scaling of Supersonic Retropropulsion Flowfields”, Experiments in Fluids, 66
H. Lee, P. Martin, O. Williams, “Compressible boundary layer velocity transformation based on a generalized form of the total stress,” Physical Review Fluids.
O. Williams, D. Sahoo, M. Papageorge, A. J. Smits , “Effects of roughness on a turbulent boundary layer in hypersonic flow,” Experiments in Fluids.
C. Helm, P. Martin, O. Williams, “Characterization of the shear layer in separated shock/turbulent boundary layer interactions,”Journal of Fluid Mechanics, 2020
O. Williams, D. Sahoo, M. Baumgartner, A.J. Smits, “Experiments on the structure and scaling of hypersonic boundary layers,” Journal of Fluid Mechanics, 834, 237-270, 2018
O. Williams, A.J. Smits, "Effect of tripping on hypersonic turbulent boundary layer statistics", AIAA Journal, 55 (9), 3051-3058, 2017
Funded by AFOSR