Abstract
The origins of the velocity fluctuations in the test section of a wind tunnel are discussed. Vorticity (turbulence converted from upstream) can be reduced by a careful design of the settling chamber to almost any desired level. The amplitudes of pressure waves propagating round the tunnel circuit can also be reduced considerably. The lowest levels of the velocity fluctuations in wind tunnels are determined by those pressure fields that are created on the outer boundaries of the test section. These boundaries are the free shear layers in the case of free jet facilities and the turbulent boundary layers in the case of closed wall test sections. The lower limit for the rms velocity level is achieved in many open jet wind tunnels (typically 0.15%). The corresponding limit for low speed tunnels with closed test sections is smaller by a factor of at least twenty but not yet known.
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Michel, U., Froebel, E. Lower limit for the velocity fluctuation level in wind tunnels. Experiments in Fluids 6, 49–54 (1988). https://doi.org/10.1007/BF00226134
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DOI: https://doi.org/10.1007/BF00226134