Unique approach for physical model studies of nitrogen gas supersaturation

High levels of dissolved gas downstream of Wanapum Dam on the Columbia River have required Public Utility District Number 2 of Grant County (the District) to investigate various approaches to reduce gas supersaturation levels. To evaluate the effectiveness of flow deflectors mounted on the spillway face the District had a physical model built of three bays of the Wanapum Spillway. The model was used to both qualitatively and quantitatively assess the performance of the flow deflectors. The qualitative evaluation was performed by visual observations of the flow patterns generated by each flow deflector downstream of the spillway. Whereas, the quantitative evaluation was performed by collecting an extensive data set describing velocity fields and bubble distributions. This data set was then analyzed numerically to predict the downstream concentration of gas supersaturation. The purpose of this paper is to describe the physical model study and the qualitative evaluation of the flow deflectors. A companion paper by Orlins and Gulliver (1996) describes the numerical model developed to analyze the velocity and bubble data.