Kentaro YAGI

Numerical Analysis of Vertical Thermals Using the Turbulence Model

Yusuke FUKUSHIMA

Vertical thermals are related to prevention of the sea pollution and the diffusion of the wastewater. Thus, the study of the flow mechanism of vertical thermals is important to predict and prevent the environmental pollution. The numerical analysis of saline thermals was carried out using the k-ƒÃ turbulent model. The basic equations are discretized by the implicit method and the pressure equation is solved by the SIMPLE method. The numerical results are compared with the experiment of vertical gravity currents carried out by Fukushima and Tanaka (2001). The cases of the concentration of saline thermals of 1, 3 and 5% were analyzed. The travel speed of the saline thermals was compared with the experimental results. The analytical values decreased quickly at first as shown the experimental results. The numerical solutions of the width of the saline thermals are compared with the experimental results. At the salinity concentration of 3% and 5%, the width increased linearly which were coincided with the experimental results. In the case of the salinity concentration of 1%, both numerical and experimental results changes non-linearly. Thus the numerical analysis using the k-ƒÃ turbulence model can express the behavior of the vertical thermals well.