Surface Pressure Measurements on an Aerofoil in Transonic Flow
DEN 302 Applied Aerodynamics
SURFACE PRESSURE MEASUREMENTS ON AN AEROFOIL IN TRANSONIC FLOW
Abstract
The objective of this exercise is to measure the pressure distribution across the surface on an aerofoil in a wind tunnel. The aerofoil is tested under several different Mach numbers from subsonic to supercritical. The purpose of measuring the pressure distributions is to assess the validity of the Prandtl-Glauert law and to discuss the changing chracteristics of the flow as the Mach number increases from subsonic to transonic.
As a result of the experiment and computation of data, the aerofoil was found to have a critical Mach number of M=0.732. Below this freestream Mach number the Prandtl-Glauert law predicted results very successfully. However, above this value, the law completely breaks down. This was found to be the result of local regions of supersonic flow and local shockwaves.
Contents
Abstract 2 Apparatus 2 1.Induction Wind Tunnel with Transonic Test Section 2 2.Aerofoil model 3 3.Mercury manometer 3 Procedure 3 Theory 3 Results 4 Discussion 8 Transonic Flow 8 Analysis 9 Conclusion 11 Bibliography 11
Apparatus
1.Induction Wind Tunnel with Transonic Test Section
The tunnel used in this experiment has a transonic test section with liners, which, after the contraction, remain nominally parallel bar a slight divergence to accommodate for boundary layer growth on the walls of the test section. The liners on the top and bottom are ventilated with longitudinal slots backed by plenum chambers to reduce interference and blockage as the Mach number increase to transonic speeds. The working section dimensions are 89mm(width)*178mm(height).
The stagnation pressure , p0∞, is close to the atmospheric pressure of the lab and with only a small error ,is taken to be equal to the settling chamber pressure. The reference staticpressure, p∞, is measured via a pressure tapping in the floor of the working section, well upstream of the
SURFACE PRESSURE MEASUREMENTS ON AN AEROFOIL IN TRANSONIC FLOW
Abstract
The objective of this exercise is to measure the pressure distribution across the surface on an aerofoil in a wind tunnel. The aerofoil is tested under several different Mach numbers from subsonic to supercritical. The purpose of measuring the pressure distributions is to assess the validity of the Prandtl-Glauert law and to discuss the changing chracteristics of the flow as the Mach number increases from subsonic to transonic.
As a result of the experiment and computation of data, the aerofoil was found to have a critical Mach number of M=0.732. Below this freestream Mach number the Prandtl-Glauert law predicted results very successfully. However, above this value, the law completely breaks down. This was found to be the result of local regions of supersonic flow and local shockwaves.
Contents
Abstract 2 Apparatus 2 1.Induction Wind Tunnel with Transonic Test Section 2 2.Aerofoil model 3 3.Mercury manometer 3 Procedure 3 Theory 3 Results 4 Discussion 8 Transonic Flow 8 Analysis 9 Conclusion 11 Bibliography 11
Apparatus
1.Induction Wind Tunnel with Transonic Test Section
The tunnel used in this experiment has a transonic test section with liners, which, after the contraction, remain nominally parallel bar a slight divergence to accommodate for boundary layer growth on the walls of the test section. The liners on the top and bottom are ventilated with longitudinal slots backed by plenum chambers to reduce interference and blockage as the Mach number increase to transonic speeds. The working section dimensions are 89mm(width)*178mm(height).
The stagnation pressure , p0∞, is close to the atmospheric pressure of the lab and with only a small error ,is taken to be equal to the settling chamber pressure. The reference staticpressure, p∞, is measured via a pressure tapping in the floor of the working section, well upstream of the
Bibliography: H.H.Hurt, J. (1965). Aerodynamics for Naval Aviators. Naval Air Systems Command. Mason. (2006). Transonic aerodynamics of airfoils and wings. Virginia Tech. Motallebi. (2012). Surface Pressure Measurements on an Aerofoil in Transonic Flow. London: Queen Mary University of London.