Method for predicting diffusion of discharged warm water in the regions of coastal sea

The present situation of the researches that have been made for predicting the process and range of diffusion of warm drain is reviewed. This review is divided into eight sections. The first section deals with the present situation of warm drain from power plants. For the establishment of drainage standard, there are many difficult problems to be solved because water temperature differs in its nature from other regulation items. In the second section, the process of diffusion and cooling of warm drain is explained. The third section deals with the diffusion characteristics of warm drain in Japanese coastal sea due to water temperature. Two types of diffusion are known. One is dominant irregular current, and the other is periodical reciprocating stream. The fourth section deals with the methods of prediction of diffusion. Research methods and simulation models are described. The fifth section deals with the prediction with single layer model. Fundamental consideration on the simulation with single layer model and the numerical model for flow and thermal diffusion are discussed. The equations for computing diffusion coefficient are given. The sixth section deals with the adaptability of the method for predicting diffusion. Comparison between the result of prediction and the result of actual measurement is discussed on various cases, namely open sea, inland sea and bay. The problems of how to adapt simulation method for the cases are considered. Irregular wave action off-shore, blowing flow effect on the range of diffusion, and heat transfer between atmosphere and water surface for a large amount of cooling water of some 100 m3/sec should be considered. The seventh section deals with diffusion prediction by hydraulic model experiment. (Iwakiri, K.)