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 0, either current spreads with constant velocity proportional to 0. When 0 becomes small, different tendencies are noticeable in the current velocity in these two cases. For the one-component case, U decreases to zero as 0 approaches zero. For the two-component case, U also becomes small, but does not tend to zero, as 0 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.