Numerical Simulation of Underwater Runoff Propagation in the Heraklean Peninsula Coastal Zone

Abstract

The problem of waste water propagation from the underwater source over the Heraklean Peninsula coastal zone is studied based on the three-dimensional numerical model simulating a break on the Sevastopol major municipal sewage trunk line. The calculations are made for three types of density stratification obtained by R/V Biryuza in September, 2015 and May, 2016. The outlet depth varied from 15 to 30 m. Numerical simulation was carried out on a uniform rectangular grid with 20 m horizontal step and 1 m vertical discreteness. Time integration step was 5 s, total integration time was 12 h. The effect of positive buoyancy in the model was created by fresh water inflow. It is revealed that the wastewater rising to the surface depends on the features of density stratification. The main factor preventing the polluted water from rising is the presence of the density drop layers above the outlet. The general trend consisting in increase of the polluted layer area accompanied by weakening of density stratification and decrease of current velocities is observed. It is found that the wastewater field close to the outlet consists of a stem and a jet oriented along the direction of the ambient current. As the current velocity increases, the top of the stem lowers and the jet sinks, its transverse size simultaneously decreases.

Keywords

• coastal zone of the Crimea
• wastewater
• underwater outlet
• density stratification
• numerical simulation