Wind tunnel flow quality needs to be characterized to match flight conditions because freestream disturbance levels have a significant effect on transition behavior. The characterization of wind tunnel flow quality usually involves direct measurements of freestream turbulence and acoustic disturbance levels and comparison to predetermined criteria. However, these measurements may not fully capture the relevant flow physics. The goal of this research is to design a device for characterizing wind tunnel flow quality in the National Transonic Facility, a cryogenic wind tunnel capable of high Reynolds numbers. The characterization will be based on the transition location on the device and is a more direct way of comparing wind tunnel flow quality to actual flight conditions.
Three codes aree used to develop and characterize the transition body. MSES is used to calculate pressure distributions and to do inverse design calculations. Swept wing boundary layer profiles are computed using Wingbl2, and then LASTRAC is used to perform linear parabolic stability equation calculations to determine the disturbance growth.
The final design is successful at balancing various transition mechanisms and delays transition to 60% chord for a Mach number of 0.4 and a Reynolds number of 60 million. Tollmien-Schlichting waves are damped below a critical N-factor of 9 at the leading edge, and crossflow growth at the leading edge is also reasonably damped. With this result, the body can be used to characterize the flow quality by observing which transition mechanism becomes dominant. The behavior of the body for a range of Reynolds numbers and angles of attack is determined, and results confirm that stationary crossflow becomes more dominant at lower (more negative) angles of attack.
|Commitee:||Choudhari, Meelan, Manno, Vincent|
|School Location:||United States -- Massachusetts|
|Source:||MAI 47/05M, Masters Abstracts International|
|Keywords:||Flow quality, Stability, Transition|
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