EXPERIMENTAL-EVIDENCE OF HOMOGENEOUS SUPERFLUID TURBULENCE IN LARGE-PORE POROUS-MEDIA

Experimental results are presented for counterflow and isothermal cofl ow through large-pore porous materials, with porosities greater than 9 0% and permeabilities of order 10(-11) m2. Counterflow velocities rang ing from 0.06 to 0.14 m/s were obtained. Because of the large-pore geo metry, and the velocity range investigated, the superfluid is fully tu rbulent. The counterflow data are well described by the two-fluid mode l using the Schwarz model of homogeneous mutual friction, with a large r, empirically-modified, mutual friction coefficient. The same mutual friction model is applied to the coflow results, assuming that dissipa tion due to superfluid vortex interaction with the wall of the porous media is negligible. In this case, the normal-fluid and superfluid vel ocities are coupled through the mutual friction, and relative velociti es are calculated from pressure drop measurements. For mass flow veloc ities in the range 0.00 to 0.10 m/s, we calculate relative velocities up to 0.07 m/s, and normal-fluid velocities in excess of 0.04 m/s. An interesting feature of the coflow pressure drop, as a function of the normal-fluid velocity, is that it is larger than the counterflow press ure drop by the ratio of the total density to the normal-fluid density .