Pressure Management on a Supercritical Airfoil in Transonic Flow
Pressure Management on a supercritical aerofoil in transonic flow
Abstract-At transonic speeds an aerofoil will have flow accelerate onwards from the leading edge to sonic speeds and produce a shockwave over the surface of its body. One factor that determines the shockwave location is the flow speed. However, the shape of an aerofoil also has an influence. The experiment conducted compared Mach flow over a supercritical aerofoil (flattened upper surface) and a naca0012 aerofoil (symmetrical). Despite discrepancies, the experiment confirmed the aerodynamic performance of a supercritical aerofoil being superior to a conventional aerofoil. A comparison of the graphical distributions demonstrates the more even pressure distribution on a supercritical aerofoil and a longer delay in shockwave formation. All of which, reflects the theory.
Table of Contents
Introduction 3 Apparatus 3
Induction Wind Tunnel with Transonic Test Section 3
Mercury Manometer 4 Procedure 4 Theory and Equations 5 Results 6 Discussion 10
Theory of Transonic Flight 10
Relating the Theory to the Experiment 11
Effectiveness of Supercritical aerofoils……………………………………………………………………...11
Limitations and Improvements 12 Appendix 13 References 14
Introduction
For any object travelling through a fluid such as air, a pressure distribution over all of its surface exists which helps generate the necessary lift. Lift is an aerodynamic force which is perpendicular to the direction of the aerofoil.
Transonic speeds result in the formation of shockwaves over the top surface of the aerofoil. This is due to accelerated flow over the surface region. We say this region is approximately between 0.8-0.9. Since the flow must accelerate and then will lose velocity following the shockwave the aerofoil will have a subsonic and sonic region. For the majority of commercial airlines this is not a desired region to cruise at given the instantaneous pressure distribution which passengers would
Abstract-At transonic speeds an aerofoil will have flow accelerate onwards from the leading edge to sonic speeds and produce a shockwave over the surface of its body. One factor that determines the shockwave location is the flow speed. However, the shape of an aerofoil also has an influence. The experiment conducted compared Mach flow over a supercritical aerofoil (flattened upper surface) and a naca0012 aerofoil (symmetrical). Despite discrepancies, the experiment confirmed the aerodynamic performance of a supercritical aerofoil being superior to a conventional aerofoil. A comparison of the graphical distributions demonstrates the more even pressure distribution on a supercritical aerofoil and a longer delay in shockwave formation. All of which, reflects the theory.
Table of Contents
Introduction 3 Apparatus 3
Induction Wind Tunnel with Transonic Test Section 3
Mercury Manometer 4 Procedure 4 Theory and Equations 5 Results 6 Discussion 10
Theory of Transonic Flight 10
Relating the Theory to the Experiment 11
Effectiveness of Supercritical aerofoils……………………………………………………………………...11
Limitations and Improvements 12 Appendix 13 References 14
Introduction
For any object travelling through a fluid such as air, a pressure distribution over all of its surface exists which helps generate the necessary lift. Lift is an aerodynamic force which is perpendicular to the direction of the aerofoil.
Transonic speeds result in the formation of shockwaves over the top surface of the aerofoil. This is due to accelerated flow over the surface region. We say this region is approximately between 0.8-0.9. Since the flow must accelerate and then will lose velocity following the shockwave the aerofoil will have a subsonic and sonic region. For the majority of commercial airlines this is not a desired region to cruise at given the instantaneous pressure distribution which passengers would
References: 1) http://www.southampton.ac.uk/~jps7/Aircraft%20Design%20Resources/aerodynamics/supercritical%20aerofoils.pdf 2) http://www.nasa.gov/centers/dryden/pdf/89232main_TF-2004-13-DFRC.pdf 3) http://en.wikipedia.org/wiki/Supercritical_airfoil 4) Scott, J., 2000 5) Motellabilabhandout