What is it about?
In a transonic cruise flight, when an airliner flies at the critical Mach number (M < 1), then the flow over the upper surface reaches Mach 1 (sonic condition). And if an airliner goes beyond the critical Mach number, then the shock wave appears on the upper surface, which creates a drag on the wings and reduces the lift. If this aircraft further goes to a combination of increased Mach number and angle of attack, then the self-sustained shock oscillations accompanying intermittently separated flow behind the shock occurs and this phenomenon is called the transonic buffet.
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Photo by Jerry Zhang on Unsplash
Why is it important?
The transonic buffet is subjected to the self-sustained shock oscillation accompanying intermittently significant flow separation. Such a flow produces instability in the flow over the wing, which creates fluctuations in lift and drag. And fluctuations in load on the wing can create structural vibration, called buffeting, which may generate fatigue and adversely affects structural integrity. So buffet limits the flight envelope of a transonic flight.
Perspectives
The simulations were done with the open source CFL3D code and uses structured grids. The SA turbulence model is used. The unsteady simulations clearly show the shock oscillations in the schlieren images and the skin friction lines show flow separation initiated from almost 80% of chord. The shock amplitude was 2% and the shock oscillation Strouhal number
Kartik Venkatraman
Indian Institute of Science
I am thankful that our article is presented on the Kudos platform for wide range of audiences. I hope this article provides a good introduction to the transonic buffet and makes it an important problem for transonic flights. Despite the decade's research, the transonic buffet is yet to be understood well.
Magan Singh
Indian Institute of Science
Read the Original
This page is a summary of: Transonic buffet in the finite span Benchmark Supercritical Wing (BSCW), June 2022, American Institute of Aeronautics and Astronautics (AIAA),
DOI: 10.2514/6.2022-4172.
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