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The effects of increased Reynolds number (Re) on clean and rough airfoils were investigated by wind tunnel experiments and by numerical simulation with an improved Navier-Stokes solver. By cooling the cryogenic wind tunnel in Cologne (KKK) of the German-Dutch Wind-Tunnel (DNW) down to 100 K, values of Re up to 10 × 106 were reached, based on a model chord of 500 mm. Whereas the clean surface configuration shows no drastic loss in maximum lift, the lift-to-drag ratio decreases from 95 to approximately 85, mainly due to an increase of drag. In contrast to that, rough surface configurations, including zig-zag tape for transition fixing and carborundum based distributed roughness around the nose, show increased performance for increased Re. In parallel, numerical simulations were carried out with a boundary layer stability code coupled to a Navier-Stokes solver. The trends in behaviour of the boundary-layer based properties were predicted well, in contrast to the separation pattern responsible for maximum lift.

Essential Tremor (ET) is a motion disorder which affects as many as one in 20-25 adults over the age of 40 [1]. Leblanc [2] proposed a device which consists of four linear actuators attached to a patient's wrist in an effort to actively suppress the tremor. This paper demonstrates experimentally a simplified version of that device. The system was tested on a stand designed to simulate an adult lower arm with a tremor in the horizontal plane. A single linear inertial actuator was attached to the "wrist" of the test stand. An accelerometer attached on the opposite side of the arm provided feedback to the controller. This paper demonstrates this system operating to produce 20%-60% vibration reduction in the 6-13 Hz bandwidth.

The combustor diffuser in a gas turbine engine must accept a high-speed, unsteady, distorted flow from the engine compressor. It must deliver flow to the combustor with minimum loss in total pressure and minimum velocity profile distortion. Both pressure recovery and outlet flow distortion characteristics of diffusers must be considered in design tradeoffs. The purpose of this investigation was to study the effects of nonuniform inlet velocity profiles on the inception of stall in two-dimensional plane-wall diffusers. Centrally-located “wake-type” inlet velocity profiles were chosen to simulate the flow conditions at the inlet of a combustor diffuser. The inlet distortion was characterized by dimensionless wake strength and wake width parameters. The experiments were performed on an open surface water table to make flow visualization possible. A centerline or pocket-type stall, such as previously reported in swirling flows, was observed for sufficiently severe inlet profile distortion. A new definition of first appreciable stall, based on a fraction of the exit area stalled, was introduced to characterize stalls which did not occur on a solid surface.

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