Introduction to Wind Tunnel
ABSTRACT
The basic concept and operation of subsonic wind tunnel was demonstrated in this experiment by conducting airfoil drag analysis on a NACA 0015 airfoil. The small subsonic wind tunnel along with apparatus such as, the manometer rake, the inclined manometer and the pitot - static tube were used with different baffle settings to record varying pressure readings. To achieve this objective, some assumptions were made for the lower range of subsonic flow to simplify the overall analysis. From the obtained aerodynamic measurements using a pitot-static tube mounted ahead of the airfoil at the test section, the actual velocity was determined and by relating it to the theoretical velocity, the velocity coefficient was calculated. The velocity coefficient varies for each baffle setting by a factor of decimals, thus the velocity coefficient can be used as a correction factor. Further, the coefficients of drag were calculated for the following angles of attack, 10o, 15o, and 20o and were compared with the published values.
INTRODUCTION
The wind tunnel is an absolute necessity to the development of modern aircrafts, as today, no manufacturer delivers the final product, which in this case can be civilian aircrafts, military aircrafts, missiles, spacecraft, and automobiles without measuring its lift and drag properties and its stability and controllability in a wind tunnel. Benjamin Robins (1707-1751), an English mathematician, who first employed a whirling arm to his machine, which had 4 feet long arms and it, spun by falling weight acting on a pulley however, the arm tip reached velocities of only few feet per second. [4]
Figure 1: Forces exerted on the airfoil by the flow of air and opposing reaction on the control volume, by Newton’s third law. [1]
This experiment will determine drag forces experienced by a NACA 0015 airfoil, subjected to a constant inlet velocity at various baffle settings with varying angles of attack.
DATA ANALYSIS, THEORATICAL BACKGROUND
The basic concept and operation of subsonic wind tunnel was demonstrated in this experiment by conducting airfoil drag analysis on a NACA 0015 airfoil. The small subsonic wind tunnel along with apparatus such as, the manometer rake, the inclined manometer and the pitot - static tube were used with different baffle settings to record varying pressure readings. To achieve this objective, some assumptions were made for the lower range of subsonic flow to simplify the overall analysis. From the obtained aerodynamic measurements using a pitot-static tube mounted ahead of the airfoil at the test section, the actual velocity was determined and by relating it to the theoretical velocity, the velocity coefficient was calculated. The velocity coefficient varies for each baffle setting by a factor of decimals, thus the velocity coefficient can be used as a correction factor. Further, the coefficients of drag were calculated for the following angles of attack, 10o, 15o, and 20o and were compared with the published values.
INTRODUCTION
The wind tunnel is an absolute necessity to the development of modern aircrafts, as today, no manufacturer delivers the final product, which in this case can be civilian aircrafts, military aircrafts, missiles, spacecraft, and automobiles without measuring its lift and drag properties and its stability and controllability in a wind tunnel. Benjamin Robins (1707-1751), an English mathematician, who first employed a whirling arm to his machine, which had 4 feet long arms and it, spun by falling weight acting on a pulley however, the arm tip reached velocities of only few feet per second. [4]
Figure 1: Forces exerted on the airfoil by the flow of air and opposing reaction on the control volume, by Newton’s third law. [1]
This experiment will determine drag forces experienced by a NACA 0015 airfoil, subjected to a constant inlet velocity at various baffle settings with varying angles of attack.
DATA ANALYSIS, THEORATICAL BACKGROUND
References: [1] Walsh, P., Karpynczyk, J., “AER 504 Aerodynamics Laboratory Manual” Department of Aerospace Engineering, 2011 [2] Hannon, J [5]Fig.1, Wind tunnel set up with instrumentation, created by authors, 2012 APPENDIX ρ Density air (ideal gas law) laboratory conditions; 22.5 C (295.65K), 29.49 inHg (99853.14Pa): ρ=pRT=99853.14Pa287JkgK(295.65K)≅1.1768 kgm3