A Numerical Study of the behaviour on Lock Volume Variations in Lock-Exchange Density Current in Cold Fresh Water

Abstract

The behaviour of warm discharge through lock-exchange was investigated numerically, with the assumption that density was taken as a quadratic function of temperature. Simulations were conducted eleven different times varying barrier position. This work as presented here is practical and can also enhance policy making towards the protection of the aquatic ecosystems. Such behaviours are evident in lakes, especially in holomictic lakes and warm discharge from thermoelectric power generating plants. The sudden increase in water temperature after discharge may leads to ”thermal shock” killing aquatic life that has become acclimatised to living in a stable temperate environment. The aim of this investigation is to better fathom and as well, gain more insight into such flows. The results show that regimes of flow is dependent on the size of the lock volume. The general behaviours here are dependent on lock volume, density difference and Reynolds number. Effects of back reflected waves on the propagation speed was not significant for small lock volume simulations. A rapid collapsing behaviour of fluid was noticed for simulations with small lock volume, and the velocity decreases with increase in lock volume in this same phase. Propagation speed is not totally independent of the lock volume. Cabbeling was also key at the point where water masses meet, and as well the development of Kelvin-Helmholtz instabilities. Relations that describes the various regimes of flow are given in Table (1 - 11). Though, there are little variations in the scaling laws as compared to the earlier studied cases where density difference was by the means of salt water. Lastly, it will be interesting if measures can be taken to eliminate the effect of this back reflected waves in other to properly fathom the behaviour in the propagation of the frontal speed after the slumping phase.