Proceedings of the Eleventh (2001) International Offshore and Polar Engineering Conference Stavanger, Norway, June 17-22, 2001 Copyright © 2001 by The International Society of Offshore and Polar Engineers ISBN 1-880653-51-6(Set); ISBN 1-880653-53-2 (Vol. ll); ISSN 1098-6189 (Set) An Experimental Study of Heated Surface Jet in a Wave Environment M. Di Natale and D. Vicinanza The Second University of Naples Aversa (Caserta), Italy ABSTRACT This paper presents an experimental study on a heated jet discharged into a stagnant ambient and in a wave environment for small Richardson numbers. Improving a previous research (Di Natale and Vicinanza, 2000), extensive measurements of veloeity and temperature profiles in lateral direction have been carried out. The aim of the work was firstly to study the hehaviour of heated jet-wave interaction and secondly to work out equations to predict the variation of velocity and temperature excess correlated with some dimensionless parameters. KEY WORDS: Heated jet, wave environment, velocity profiles, temperature profiles, thermograph, current meter. INTRODUCTION In the last years the increase in electric power request have intensified the problem of discarding heated water rejected by the plant cooling system. When this operation is not well controlled, the receiving waterbodies (lakes, rivers, coastal areas) present induced water temperature changes, with relevant water quality modifications. The most important consequence of increased temperature is the decreased solubility of oxygen in the receiver that it is essential for many forms of aquatic life. Even though international laws give criteria on thermal discharges, fixing the temperature excess ranges, some countries still rely on it for economical reasons. Three dimensional surface heated jets discharged into a stagnant ambient have been studied experimentally by many authors (Wiegel et al., 1964; Jen et al., 1966; Hayashi and Shuto, 1967; Stefan, 1972; Pande and Rajaratnam, 1977; Wiuff, 1978) considering different outlets (circular, rectangular or square) and source Richardson numbers (small, moderate or large), Rio, where: g" h o • AP°~pa Rio = U2 ° [1] in which g is the acceleration due to gravity, ho is the depth of outlet section, Apo is the difference in mass densities of the hot water discharge/9o and the ambient Pa, and Uo is the velocity at the outlet. Particularly interesting are the measurements made by Pande and Rajaratnam (1977) for moderate and large Rio (0.15+ 1.14). The Authors found that (mean) velocity and (mean) temperature profiles in the lateral direction are similar and well described by the exponential (Gaussian) following equations: -0.693( ff-.)2 urns - e ~ b,, ) ttmm [21 --=e [31 AT., where urns and Umm are the generic and maximum surface velocity; Airs = Ts- ira and ATm = Tin- ira being T~ and Tm the generic and maximum surface temperature and Ta the ambient temperature; bu and br are the values ofy where um~= 0.5 u~m and AT~ = 0.5 zlTm. Moreover they correlated the decay Of velocity and excess temperature with the dimensionless longitudinal distance from the outlet, x/~ o , and the source Richardson numbers: Umm 5.68" R~/o 3 ~ = (Rio = 0.15+0.56) [41 Umm = 1.43' R~o 1/6 Umso ~/~o~/3 (Rio = 0.79+1.14)[51 AT m 4.42.R//o 3 396