Influence of Surface Waves on Outfall Dilution

Abstract

The influence of surface waves on the dilution of buoyant discharges is investigated. The relevant dimensionless variables are derived. In the case of stagnant unstratified environments, it is shown that the dilution depends on six dimensionless variables. An experimental program is conducted to determine the relationship between surface wave parameters and the dilution relative to the no‐wave case. The dimensionless variables kept constant in the study are assigned values that are characteristic of operating ocean outfalls and are not wave‐related. The results indicate that in shallow outfalls, in a typical persistent wave environment, the surface dilution is significantly higher than for the no‐wave case. In particular, it is verified that, for an outfall in a depth of 7.7 m with persistent waves whose amplitude is 30 cm and whose period is 5 s, the surface dilution is twice that for the nowave case. This difference is quite important to the economics of shallow outfalls, especially with the gentle offshore slopes found in the southeastern United States.