A Brief Study of the Effect of Rigid Swept Surface Waves on Turbulent Drag
Speaker: Marie Denison, National Institute of Aerospace (NAI) / Science and Technology Corporation (STC)
Presentation
Abstract
Passive turbulent drag reduction techniques are of interest as a cost effective means to improve air vehicle fuel consumption. In the past, rigid surface waves slanted at an angle from the streamwise direction were deemed ineffective to reduce skin friction drag due to the pressure drag that they generate. A recent analysis seeking similarities to the spanwise shear stress generated by spatial Stokes layers suggested that there may be a range of wavelength, amplitude, and orientation in which the wavy surface would reduce turbulent drag. The present work explores the effect of swept wavy surfaces on skin friction and pressure drag by experiments and Direct Numerical Simulations (DNS). Plates with shallow and deep wave patterns were rapid-prototyped and tested using a drag balance in the 7x11 inch Low-Speed Wind Tunnel at the NASA Langley Research Center. The turbulent flow in channels with flat walls, swept wavy walls and spatial Stokes spanwise velocity forcing was simulated at a friction Reynolds number of two hundred. It is found that the drag offset between the wavy wall and the reference flat wall is within the experimental repeatability limit, whereas the channel DNS predict a slight drag increase for the shallow waves and a large pressure drag increase for the deep waves. DNS as well as oil vapor flow measurements indicate a slight deviation of the mean flow over the deep waves with respect to the inflow direction. The shortcomings of the linear model used for the estimation of the spanwise shear stress and drag are discussed.
In collaboration with Stephen P. Wilkinson and Ponnampalam Balakumar, Flow Physics and Control Branch at the NASA Langley Research Center.
Biography
Marie Denison recently joined the Science and Technology Corporation (STC) and the Advanced Modeling and Simulation branch at NASA Ames Research Center. Since 2014, she has been collaborating with the National Institute of Aerospace (NIA) and the Flow Physics and Control branch at the NASA Langley Research Center on the study of turbulent drag reduction techniques by DNS and on LES modeling. She received an M.S. degree in Aerospace Engineering from the University of Texas at Arlington, TX, where her research was focused on the receptivity of compressible flows to Dielectric Barrier Discharge actuation and on the development of a coupled plasma-compressible Navier and Stokes AMR solver. She received a Ph.D. degree in Electrical Engineering from the University of Bremen, Germany, with an emphasis on the computational modeling of Solid-State devices.