Recent and ongoing research programs in the Fluid Mechanics Laboratories at Lehigh Unniversity have addressed problems of national needs under the auspices of the following agencies and industrial concerns.

• OFFICE OF NAVAL RESEARCH: FLOW-STRUCTURE INTERACTIONS IN WAVES AND CURRENT. Wakes from stationary and oscillating cylinders are generated in steady current and in waves. They influence the loading and vibration of towing cables, offshore structures, and offshore drilling platforms. The phenomena addressed in these investigations also have application to heat transfer processes in heat exchanger tube banks and power plant systems, as well as unsteady loading of tall buildings.
• OFFICE OF NAVAL RESEARCH: FLOW-ACOUSTIC COUPLING PHENOMENA IN CAVITY SYSTEMS. Flow past cavity configurations is currently under investigation, with the primary emphasis of determining the mechanisms leading to flow-induced vibration and noise generation. Instabilities within the cavity, even in presence of fully-turbulent inflow, are the origin of strong coupling with acoustic resonant modes of the system. Related applications include noise and vibrations in pipe and valve combinations in power plants, free-surface instabilities and erosion phenomena in river embankments, instabilities in solid fuel rocket combustors, and pulsation instabilities in automobile muffler units.
• OFFICE OF NAVAL RESEARCH: INSTABILITIES DUE TO FLOW PAST PERFORATED PLATES. Flow past perforated and slatted plates, having a relatively high area ratio, and bounded by a closed cavity, can give rise to highly organized, self-sustained oscillations. These types of oscillations involve new types of shear flow instabilities, and serve as sources of flow-induced noise and vibration. Related applications include flow-induced oscillations due to openings in hulls of ships and in fuselages of aircraft, as well as transpiration due to flow past porous and perforated surfaces in automobile muffler systems and in combustion systems.
• NATIONAL SCIENCE FOUNDATION: VORTEX-BODY INTERACTIONS. Interactions of vortices with corners, wedges and leading-edges of blading are the origins of vibration, noise and unsteady heat transfer. Related applications include vortex-aircraft encounter near and at airports leading to disruption of flight trajectories, and leading-edge heat transfer mechanisms in turbomachinery.
• NATIONAL SCIENCE FOUNDATION: SHALLOW WATER VORTEX SYSTEMS. Vortex formation and interaction in shallow liquid (water) flows typical occur in two-phase manufacturing systems, shallow rivers, channels and lakes, with application to mixing processes, free-surface resonant instabilities and bottom erosion and sediment transport.
• AIR FORCE OFFICE OF SCIENTIFIC RESEARCH: BUFFETING OF AERODYNAMIC SURFACES AND PERFORMANCE OF UNMANNED COMBAT AIR VEHICLES (UCAVs). Vortex formation from swept wings at high angle-of- attack is under investigation, with application to loss of control during severe maneuvers and buffeting of the aerodynamic surfaces and appendages located in downstream regions of the flow. Related applications include instabilities occurring in turbomachinery inlet and outlet chambers, as well as two-phase separation processes in cyclone separators.
• NASA-LANGLEY RESEARCH CENTER: FLOW STRUCTURE IN MULTIPLE CYLINDER AND WHEEL SYSTEMS. Flow instabilities and turbulence in the gap region between, and downstream of, a tandem two-cylinder system is a major source of noise generation in heat exchanger assemblies, clusters of tall buildings. Related applications include minimization of the drag of a cab-trailer system in a tractor-trailer unit, and noise generated in the four-wheel bogie of the landing gear of a Boeing 767 aircraft.
• PRATT AND WHITNEY: WAKE-BLADE INTERACTION IN AIRCRAFT TURBOMACHINERY. Wakes generated in aircraft engine configurations are a major source of noise generation and detailed understanding of the wake structure is crucial in minimizing tonal noise. Related applications include noise generation in radial and axial flow pumping systems in manufacturing and power plants.
• VOLKSWAGEN FOUNDATION: FLOW-INDUCED OSCILLATIONS. Unsteady wakes, jets and mixing layers serve as sources of flow-induced vibration and noise generation. For example, shear layer instabilities in the gap region of the sunroof of an enclosed automobile and in the seats of large-scale power plant valves call for an understanding of the underlying flow physics, in order to allow effective attenuation and control. Related applications involve impinging jets and high-speed machining applications, as well as mixing processes occurring in reacting flow systems.