Definition, sources and lowest possible levels of wind-tunnel turbulence
Abstract
Wind tunnel turbulence is defined to include the fluctuations of all flow quantities in an empty tunnel test section. It can be separated into three modes, vorticity, entropy, and pressure. The pressure model is discussed in more detail. It is shown that contributions from the free shear layers of open test sections or the boundary layers of closed test sections are accompanied by much higher velocity fluctuations than plane sound waves. The lowest possible velocity fluctuation level in an open test section is determined by the pressure field generated by the free shear layer. The German-Dutch Wind Tunnel (DNW) is shown to reach this level. It is assumed that the lowest possible turbulence level in a closed test section is determined by the pressure field that is generated by the boundary layers in the test section. A spectral energy distribution and a Reynolds number scaling law for this contribution are derived.
- Publication:
-
In AGARD Wind Tunnels and Testing Tech. 12 p (SEE N84-23564 14-01
- Pub Date:
- February 1984
- Bibcode:
- 1984wttt.agarR....M
- Keywords:
-
- Pressure Distribution;
- Pressure Oscillations;
- Turbulence;
- Velocity Distribution;
- Wind Tunnels;
- Boundary Layers;
- Entropy;
- Flow Velocity;
- Reynolds Number;
- Scaling Laws;
- Shear Layers;
- Spectral Energy Distribution;
- Vortices;
- Fluid Mechanics and Heat Transfer