The flow of liquid helium II through a tube packed with rouge powder has been investigated under gradients of temperature and pressure. The flow rate, the heat current and the pressures at the ends of the tube as well as at an intermediate point have been determined at various temperatures. In flow under a thermal gradient a similar character to that earlier established for flow through narrow slits has been observed. Up to a certain critical velocity which depends on temperature, the flow is free of friction, while at higher velocities, dissipation sets in. The flow under gravity differed completely in its behaviour from the observations with the slit, since dissipation occurred at all velocities. This inconsistency in the flow phenomena has been discussed but no satisfactory explanation can be offered.
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Chandrasekhar et al. (1953) studied this question.