Listed below along with a quick description of concepts learned are a comprehensive experiments that should be done with subsonic tunnels by undergraduate programs. This list is compiled from programs at the University of Boulder, Colorado, the University of Iowa, Iowa City, the University of New South Wales, Sydney, the Indian Institute of Science, Bengaluru. Our managing Director Prof A. Prabhu was a member of the teaching staff at each institution.

 

EXPERIMENTS WITH SUBSONIC WIND TUNNEL:

• Calibration of wind tunnels

1. Wind speed against fan RPM.
2. Velocity distribution across test section.

• Flow Visualization

1. Flow past an 2-D Symmetric aerofoil
2. Flow past an 2-D Symmetric aerofoil at different angle of attack
3. Observe the flow separation with angle of attack and stall
4. Flow past on 2-D Cambered aerofoil at different angle of attack
5. Flow past a cylinder observe the separation pt and vortex shedding
6. Flow past a aircraft model at different angle of attack

• Boundary layer measurement (velocity distribution) with rake as well as traverse

• Distinguish between lam and turbulent boundary layer from mean velocity distribution.

• Growth rate of lam boundary layer

• Growth rate of turbulent boundary layer

• Velocity distribution in the wake

1. velocity distribution behind an aerofoil at different angle of attack
2. velocity distribution behind a cylinder
3. Measurement of momentum thicknesses behind aerofoil as well as cylinder
4. Observe the differences between that of an aerofoil and cylinder of the same thickness.

• Show velocity random variation for a turbulent flow, distinguish between lam flow and Turbulent flow (velocity distribution outside the Boundary layer and inside the turbulent boundary layer).

Hotwire anemometer has to be used for this experiment.

• Pressure Measurements

1. Pressure distribution on aerofoils at different angle of attack (symmetric as well as cambered)
2. Identify the separation points from the pressure distribution
3. pressure distribution on cylinder
4. measure base pressure behind the cylinder
5. Identify separation point on the cylinder

•  Force Measurements

1. Compute lift and drag from the pressure distribution on the aerofoil
2. Lift variation with angle of attack plot C_l (lift coefficient with α angle of attack)
3. Compute the drag on the cylinder from pressure distribution, calculate C_d (drag coefficient) on the cylinder.
4. show the drag variation with speed
5. Identify the critical speed for lam and turbulence separation
6. Use force balance for measurement of lift and drag of 2-D aerofoils.

      Draw C_l vs α (angle of attack) , C_d  vs α as well as C_l vs C_d

a.) Use force balance to measure the drag on the cylinder at different speeds.

       Draw the C_d vs speed, identify critical speed

b) Use force balance on aircraft model.

        Draw C_l vs α, C_d  vs α as well as C_l vs C_d curves.

        Identify stall