Princeton Cavity Experiment

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Degrees

• Doctor of Philosophy in Fluid Dynamics, Princeton University, 1982
  
• Master of Science in Fluid Dynamics, Princeton University, 1979
  
• Bachelor of Engineering in Mechanical Engineering, Stevens Institute of Technology, 1976

Scientific and Professional Society Memberships

• American Institute of Aeronautics and Astronautics, Associate Fellow
• American Physical Society, Fellow
• American Society of Mechanical Engineers

Honors and Awards

• Alexander von Humboldt Fellow, Berlin, 2009
• Fellow, American Physical Society, 2006
• IIT Sigma Xi Award for Excellence in Research, 2006
• Honeywell Advanced Technology Achievement Award, 2006
• IITRI Fellow, 1998
• Stryker Outstanding Student Organization Advisor Award, 1990
• MAE Dept. Excellence in Teaching Award, 1988
• Alexander von Humboldt Fellow, Stuttgart, 1982
• Stevens Institute of Technology, Book Award, 1976
• Guggewnheim Fellowship, Princeton University, 1976

Field of Specialty

Experimental fluid mechanics and aerodynamics with emphasis on active flow control, control of acoustic tones in cavities, airfoil performance enhancement, rotating machinery, fluidic oscillators for flow metering, and biomedical applications.

Research Interests

• AFOSR - Physics of Energy Extraction Mechanisms from Unsteady Flows
  
  The objective of our research is to study the fundamental flow physics and energy transfer mechanisms associated with gusting flows over micro air vehicles (MAV). Due to MAV's small size and flight envelope, gusting flows create large amplitude perturbations that induce unsteady, nonlinear flow phenomena such as flow separation, dynamic stall, and hysteresis. We argue that these effects present a serious design challenge, as well as an opportunity to exploit energy extraction in order to increase range, payload, and endurance. Classical theories for gust and energy extraction are based on steady, low angle-of-attack aerodynamics that are incomplete or incorrect for MAV.
  
  We are using both wind tunnel experiments and numerical simulations to document unsteady nonlinear flow phenomena occurring in strong gusts over low-aspect ratio wings at low to moderate Reynolds number. New understanding coming from these studies will be used to develop practical analytical models for energy exchange. Experiments are conducted in an unsteady flow wind tunnel that simulates flight with longitudinal and transverse gust components by controlling wing motion with a three-degree of freedom captive trajectory system. The experiments are complemented with direct numerical simulations of the three-dimensional, unsteady flow around the wing. Experimental and computational data provide the necessary information on the detailed flow structures that lead to time delays associated with the long relaxation times required for a wing to respond to transient input, and that can be exploited to optimize energy extraction.
  
  The broader impact of the research is to extend the endurance and range of MAV by reducing the power required to fly in a gusting flow. The results will also aid MAV design by providing a detailed database of three-dimensional and time dependent flows around low aspect ratio wings under gusting conditions.
  
  
• AFOSR - Closed-Loop Control of Vortex Formation in Separated Flows with Application to Micro/Unmanned Air Vehicles

Selected Publications

Srinivasan, K., Panickar, P., Raman, G., Kim,B.-H., and Williams, D. R., "Study of Coupled Supersonic Twin Jets of Complex Geometry Using Higher-Order Spectral Analysis," Journal of Sound and Vibration, Vol. 323, Issues 3-5 (2009) pp. 910-931.

Cattafesta III, L. N., Song, Q., Williams, D. R., Rowley, C. W., and Alvi, F. S., "Active Control of Flow-Induced Cavity Oscillations," Progress in Aerospace Sciences, Vol. 44 (2008) pp. 479-502.

Williams, D. R., "Supersonic Cavity Response on Open Loop Forcing," invited paper published in book Active Flow Control, series: Notes on Numerical Fluid Mechanics and Multidisciplinary Design (NNFM), R. King (Ed.), Springer-Verlag, Vol. 95, XIII (2007) 440 p.

Kim, B.-H., and Williams, D. R., "Nonlinear Coupling of Fluctuating Drag and Lift on Cylinders Undergoing Forced Oscillations," J. Fluid Mech., Vol. 559 (2006) pp. 335-353.

Rowley, C. W., Williams, D. R., Murray, R. M., Colonius, T., and MacMartin, D. G., "Linear Models for Control of Cavity Flow Oscillations," J. Fluid Mech., Vol. 547 (2006) pp. 317-330.

Rowley, C. W., and Williams, D. R., "Dynamics and Control of High-Reynolds-Number Flow over Open Cavities," Annual Review of Fluid Mechanics, Vol. 38 (2006) (article by invitation).

Kim, B.-H., Williams, D. R., Emo, S., and Acharya, M., "Modeling Pulsed-Blowing Systems for Flow Control," AIAA J., Vol. 43, No. 2 (2005) pp. 314-325.

Bernhardt, J. E., and Williams, D. R., "Closed-Loop Control of Forebody Flow Asymmetry," J. Aircraft, Vol. 37, No. 3 (2000) pp. 491-498.

Williams, D. R., "Symmetry Relations for Nonlinear Pressure Interactions on Oscillating Cylinders," Physics of Fluids, Vol. 10, No. 6 (1998) pp. 1243-1245.

Bernhardt, J. E., and Williams, D. R., "Proportional Control of Asymmetric Forebody Vortices," AIAA J., Vol. 36, No. 11 (1998) pp. 2087-2093.

Williams, D. R., Mansy, H., and Abouel-Fotouh, A., "Three-Dimensional Subharmonic Waves during Transition in the Near-Wake Region of a Cylinder," Physics of Fluids, Vol. 8 (1996) pp. 1476-1485.

Mansy, H., Yang, P.-M., and Williams, D. R., "Quantitative Measurements of Three-Dimensional Structures in the Wake of a Circular Cylinder," J. of Fluid Mech., Vol. 270 (1994) pp. 277-296.

Mansy, H., Yang, P.-M., and Williams, D. R., "Oblique and Parallel Wave Interaction in the Near Wake of a Cylinder," Phys. Fluids A, Vol. 7 (1993) pp. 1657-1660.

Bernhardt, J., and Williams, D. R., "The Effect of Reynolds Number on Vortex Asymmetry about Slender Bodies," Phys. Fluids A, Vol. 5 (1993) pp. 291-293.

Mansy, H., Amato, C., and Williams, D. R., "The Response and Symmetry Properties of a Cylinder Wake Subjected to Localized Surface Excitation", J. Fluid Mech., Vol. 234 (1992) pp. 71-96.

Mansy, H., and Williams, D. R., "Symmetry of Interacting Modes in a Cylinder Wake," Phys. Fluids A, Vol. 3 (1991) pp. 2047-2049.