Thermal Fronts in Heated Water Discharges

by Vahid Alavian, (A.M.ASCE), Assistant Prof.; Dept. of Civ. Engrg., Univ. of Illinois, Urbana-Champaign, Ill.,
John A. Hoopes, (M.ASCE), Prof.; Dept. of Civ. and Environmental Engrg., Univ. of Wisconsin, Madison, Wis.,

Serial Information: Journal of the Hydraulics Division, 1982, Vol. 108, Issue 5, Pg. 707-725

Document Type: Journal Paper


Large scale, periodic motions known as thermal fronts, which are observed in surface, heated water discharges were investigated in a laboratory model. Characteristic length scales corresponding to various regions of flow in a heated water discharge are evolved from the kinematic mass, momentum, and buoyancy fluxes and the ambient velocity considerations. A one-dimensional, wave type model, describing the velocity of propagation of fully-developed thermal fronts, is developed. Experiments show that thermal fronts become fully developed in the far field region of the discharge mixing zone where the horizontal motions due to the discharge buoyancy and to the ambient water velocity dominate the discharge behavior. The mean behavior of the heated discharges with thermal fronts is found to be similar to heated discharges without thermal fronts. The measured velocities are in good agreement with the one-dimensional, wave model predictions. Criteria for the discharge densimetric Froude number and discharge-ambient velocity ratio are developed for the occurrence of thermal fronts.

Subject Headings: Thermal pollution | Water discharge | Thermal properties | Thermal analysis | Wave velocity | Motion (dynamics) | Buoyancy | Surface waves

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