The behaviour of warm water discharge at a temperature \(T_{m}\) horizontally into a homogeneous body of cold fresh water at a temperature \(T=0\) was investigated by means of a numerical model through lock-exchange. Water density here was taken to be a quadratic function of temperature. This work as presented here is practical and relevant to many fields of study and also enhances policy making towards the protection of the aquatic ecosystems. Such scenarios are evident in lakes, especially in holomictic lakes and warm discharge from thermoelectric power generating plants. Because the sudden increase in the water temperature after discharge will 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 studies. Cabbeling process was key as whenever fluid of different temperature come in contact and as well as the development of Kelvin-Helmholtz instability in the interaction surface. The general behaviours here are dependent of lock volume, density difference and Reynolds number. We noticed that the collapsing velocity of the denser fluid within the first time frame was high, higher than every fluid movement elsewhere. Relations that describes the various regimes of flow were also drawn, and as well as those for the spreading distance \(L_{d c}\) of the density current. However, 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. But for those where density difference is as a result of temperature, we believe that these results are a good starting point to better fathom and as well, gain more insight into such studies. Lastly, the consideration of barrier position is key, being that the lock volume is also believed to be a factor. Researchers can also gain more knowledge in terms of the dynamics of such flows.

Laminar plumes from a line source of warm water at the base of a shallow, homogeneous body of cold water (below the temperature of maximum density)were simulated by a computational model. The plume water undergoes buoyancy reversal as it mixes with the cold ambient. If this occurs before the plume has reached the ceiling of the domain, the plume flaps from side to side. Otherwise, it spreads along the ceiling and then sinks, with a vortex enclosed between the rising plume and the sinking flow. Some of the dense, mixed water from the sinking flow is re-entrained into the rising plume, while the rest flows outwards along the floor. However, with high source temperatures, a sufficient volume of warm water eventually builds up to also form a positively buoyant gravity current along the ceiling.

The behaviour of warm water discharge at a temperature higher then Tm horizontally into a homogeneous body of cold fresh water at a temperature lower then Tm was investigated by means of a numerical model. Water density here was taken to be a quadratic function of temperature. Thus cabbeling process was inevitable as positively buoyant water form surface current while penetrating the ambient water. The current halted as mixture became dense and sink. These results are very similar to the experimental study of warm discharge into cold water by Marmoush et al. [14] and Bukreev [22]. The results showed an initially sinking water at the point where the two water bodies meets within the first few time interval. Development of Rayleigh-Taylor instabilities was observed at the lower part of the surface current as lighter fluid penetrate further. The frontal head was found to being replenished by a surface flow of warm unadulterated water, but after much entrainment of ambient fluid and cabbeling then, this head halted and sink. On the floor, denser fluid advance in the same direction as the original surface current, with some degree of Kelvin-Helmholtz instability as it penetrates further. Relations were also drawn that describes the speed, the spread length of both surface current were obtained. Relation were also drawn that describes the final spread length of the surface current Lsm and the time taken to reach that final spread length Tsm as a function ϕin. This work as presented here is practical and relevant to many fields of study and also enhances policy making towards the protection of the aquatic ecosystems.

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 thepropagation of the frontal speed after the slumping phase.