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Shocks, Shock-Boundary Layer Interaction, And Transonic Flutter

Electronic Theses of Indian Institute of Science

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Title Shocks, Shock-Boundary Layer Interaction, And Transonic Flutter
 
Creator Karnick, Pradeepa Tumkur
 
Subject Aerodynamics
Airfoil
Transonic Flutter
Shock-Boundry Layer
Airplanes
Turbulent Viscous Flow
Flutter Boundary
Shock Dynamics
Aeroelasticity
Euler Flow
Turbulence
Transonic Flow
Aerospace Engineering
 
Description Transonic utter is an aeroelastic instability characterized by part-chord shocks over an airfoil and single mode oscillations leading to a drop in the utter boundary. We present a numerical study that examines the influence of shocks, shock-boundary layer interactions, and three-dimensional flow features on the transonic utter boundary. Using energy concepts we show that shocks and shock-boundary layer interactions have a profound influence on the stability of an aeroelastic system. Viscosity stabilizes the aeroelastic system through thickness effects up-to the bottom of the transonic dip. Beyond, shock induced separation not only stalls the aeroelastic system, but also makes it oscillate about a new equilibrium position. In this region, where viscous effects are dominant, the inviscid utter boundary shows multiple utter points. Modal contributions to the response of the aeroelastic systems |viscous and inviscid | indicate that viscosity restricts higher mode participation. Restriction of higher modes by viscosity is responsible for the elimination of multiple utter points that are present in the inviscid case. Multiple forcing frequencies are observed in those regions of the utter boundary where viscous effects are dominant. Further, the shock dynamics exhibit shock-reversal where-in the shock motion predicted by the viscous simulation is 180_ out of phase relative to that of the inviscid case. At Mach numbers beyond the shock-stall region the shock moves close to the trailing edge of the airfoil, and inviscid and viscous simulations predict almost a similar utter boundary. Three-dimensional transonic flow structures on a finite-span wing aeroelastic model de-stabilizes it relative to an equivalent two-dimensional model.
 
Contributor Venkatraman, Kartik
 
Date 2017-09-27T06:28:37Z
2017-09-27T06:28:37Z
2017-09-27
2014
 
Type Thesis
 
Identifier http://etd.iisc.ernet.in/handle/2005/2688
http://etd.ncsi.iisc.ernet.in/abstracts/3509/G25863-Abs.pdf
 
Language en_US
 
Relation G25863