Turbulent drag on a low-frequency vibrating grid in superfluid 4He at very low temperatures

Wepresentmeasurements of the dissipative turbulent drag on a vibrating grid in superfluid 4He over awide range of (low) frequencies. At high velocities, the dissipative drag is independent of frequency and is approximately the same as that measured in normal liquid 4He. We present measurements on a similar grid in superfluid 3He-B at low temperatures which shows an almost identical turbulent drag coefficient at low frequencies. However, the turbulent drag in 3He-B is substantially higher at higher frequencies. We also present measurements of the inertial drag coefficient for grid turbulence in 4He. The inertial drag coefficient is significantly reduced by turbulence in both superfluid and normal liquid 4He.