A double diffusive lock-exchange flow with small density difference

Abstract

An experiment on center lock-exchange flow is carried out when the density difference is very small. Two cases (one-component fluid and two-component fluid) are investigated for comparison. The experimental results indicate that there is a substantial difference in appearance between one-component gravity currents and two-component currents when the density difference is extremely small. For a large initial density difference Δϱ0, either current spreads with constant velocity proportional to √Δϱ0. When Δϱ0 becomes small, different tendencies are noticeable in the current velocity in these two cases. For the one-component case, U decreases to zero as Δϱ0 approaches zero. For the two-component case, U also becomes small, but does not tend to zero, as Δϱ0 approaches zero. This suggests that even if the initial water densities are exactly the same, double diffusive effects can produce inhomogeneity of density and induce the current.