Numerical simulation and verifications on thermal stratification in a stratified reservoir

Abstract

Taking Jinpen Reservoir in Xi'an as a study case,a numerical simulation method for thermal structure of a stratified reservoir was developed and validated against the field data. The development and characteristics of the thermocline under various conditions of short wave radiation and bulk extinction coefficient for short wave radiation was numerically investigated by using a commercially-available software of Fluent. The net total surface heat transfer is positive in spring and summer,while negative in autumn and winter. The long wave radiation mainly contributes to the net total surface heat transfer,while the short one controls the development of the thermocline. The depth of the thermocline increased and the temperature gradient over the thermocline decreased as the bulk extinction coefficient decreased,and the bulk extinction coefficient is positively related to the algae concentration. There was a maximum value of the surface short wave radiation for a certain reservoir,the temperature difference between the top and bottom of the thermocline increased when the short wave radiation was below the maximum radiation,but it decreased when the short wave radiation was beyond the maximum radiation. Moreover,a heat balance and a stable thermocline can't be easily developed under higher short wave radiation.