Journal of Hydraulic Engineering

A submerged, negatively buoyant radial jet, discharging horizontally beneath a free surface into water of initially uniform density, was studied experimentally and theoretically. The situation relates to the operation of an ocean thermal energy conversion plant and is an example of buoyancy and confinement offering opposing influences on jet trajectory. For shallow submergence, the jet is attached to the free surface while for large submergence or greater (negative) buoyancy, the jet is detached. An experimental program yielded data on jet trajectory, temperature, velocity and discharge conditions associated with transition between attached and detached regimes. A hysteresis effect was noted as the conditions for attachment and detachment were different. Dimensional analysis yielded a single parameter of primary importance and two parameters of secondary importance in describing jet behavior. An integral jet analysis based on a spreading assumption was successfully adapted to include induced velocity and pressure effects on jet behavior.

The phenomenon of wave refraction due to current is an important factor in the longshore current generation and the wave transformation in the vicinities of narrow strait and river mouth. The existing numerical models of wave refraction due to current are all for regular waves. A numerical model is proposed for the computation of the change of the directional spectral density of irregular waves due to current‐depth refraction. The wave action equation is applied as the basic equation, in which the wave direction is introduced as the fourth independent variable. Several sample computations show that this model can explain the change of the directional spectra due to current. It is found that the significant wave height changes more rapidly than that of the corresponding regular waves having the same wave height, period and direction as those of the irregular waves. The change of a mean wave direction of the irregular waves is different from that of the corresponding regular waves.

The effects of free and forced convection mechanisms on evaporation rates from open water bodies is examined. Examination of measurements from seven water bodies (from very small to tens of square kilometers) indicates that evaporation resulting from forced convection progresses at its theoretical value for a wide range of ambient conditions. On the other hand, free convection effects are sensitive to the windspeed and water surface to air temperature difference. Based on the analysis presented, a new evaporation equation is obtained.

A method is proposed which can be used to couple the two phenomena of plume rise and gravitational spreading in obtaining an integrated solution to the mixing in wastewater plumes from multiple port diffusers. Explicit solutions are obtained for the special case of two‐dimensional pure plumes in either uniform or linear density profiles. These solutions are of practical importance in providing estimates of initial dilution for both design calculations and environmental monitoring purposes.