Liquid helium at 4.2 K has a viscosity that is about 40 times smaller than that of water
at room temperature, and about 600 times smaller than that of air at atmospheric
pressure. It is therefore a convenient fluid for generating in a table-top apparatus
turbulent flows at high Reynolds numbers that require large air and water facilities.
Here, we produce turbulence behind towed grids in a liquid helium chamber that is
5 cm2 in cross-section at mesh Reynolds numbers of up to 7×105. Liquid nitrogen is
intermediate in its viscosity as well as refrigeration demands, and so we also exploit
its use to generate towed-grid turbulence up to mesh Reynolds number of about
2×104. In both instances, we map two-dimensional fields of velocity vectors using
particle image velocimetry, and compare the data with those in water and air.
