Engineering topics

Wygnanski, Israel

Publications and source records attributed to Wygnanski, Israel.

4 records

NASA NTRS2020

Flow Control Applications

Flow control has a long history with many successes across a plethora of applications. This report addresses the characteristics of the approaches that are actually used, why they are used, the many approaches that are not used, and why. Analysis indicates ways forward to increase applicability/usefulness, and efficiency of flow control research. Overall, greater and more effective progress in flow control requires utilization of far more detailed information early in the research process regarding application details and requirements.

Bushnell, Dennis M.↗

NASA NTRS2013

Sweeping Jet Actuators - A New Design Tool for High Lift Generation

Active Flow Control (AFC) experiments performed at the Caltech Lucas Wind Tunnel on a generic airplane vertical tail model proved the effectiveness of sweeping jets in improving the control authority of a rudder. The results indicated that a momentum coefficient (C(sub u)) of approximately 2% increased the side force in excess of 50% at the maximum conventional rudder deflection angle in the absence of yaw. However, sparsely distributed actuators providing a collective C(sub u) approx. = 0.1% were able to increase the side force in excess of 20%. This result is achieved by reducing the spanwise flow along the swept back rudder and its success is attributed to the large sweep back angle of the vertical tail. This current effort was sponsored by the NASA Environmentally Responsible Aviation (ERA) project.

Graff, Emilio↗

NASA NTRS2013

Performance Enhancement of a Vertical Tail Model with Sweeping Jet Actuators

Active Flow Control (AFC) experiments performed at the Caltech Lucas Adaptive Wall Wind Tunnel on a 12%-thick, generic vertical tail model indicated that sweeping jets emanating from the trailing edge (TE) of the vertical stabilizer significantly increased the side force coefficient for a wide range of rudder deflection angles and yaw angles at free-stream velocities approaching takeoff rotation speed. The results indicated that 2% blowing momentum coefficient (C(sub mu) increased the side force in excess of 50% at the maximum conventional rudder deflection angle in the absence of yaw. Even C(sub mu) = 0.5% increased the side force in excess of 20% under these conditions. This effort was sponsored by the NASA Environmentally Responsible Aviation (ERA) project and the successful demonstration of this flow-control application could have far reaching implications. It could lead to effective applications of AFC technologies on key aircraft control surfaces and lift enhancing devices (flaps) that would aid in reduction of fuel consumption through a decrease in size and weight of wings and control surfaces or a reduction of the noise footprint due to steeper climb and descent.

Seele, Roman↗

NASA NTRS2010

Control of Vortex Breakdown in Critical Swirl Regime Using Azimuthal Forcing

We finally go back to the four swirl cases and see how the flow responds to either forcing m = -1 or m = -2. On the left we see the flow forced at m = -1 We see that the PVC locks onto the applied forcing also for lower swirl number causing this high TKE at the jet center. The amplification of this instability causes VB to occur at a lower swirl number. The opposite can be seen when forcing the flow at m=-2 which is basically growing in the outer shear layer causing VB to move downstream . There is no energy at the center of the vortex showing that the precessing has been damped. The mean flow is most altered at the swirl numbers were VB is unstable.

Oberleithner, Kilian↗