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Feasibility of Con rolling Cavity Shape <br />In initial model studies, using both direct and reverse circulation, attempts were made to <br />duplicate actual field cavities whose dimensions were known through sonar log surveys. Figure 1 <br />depicts the type of cavities obtained (3). Reproducibility of exac[ shapes was not achieved, though <br />it was possible to duplicate the general configurations in every case. This inability to reproduce <br />the exact shape of the field cavities in [he laboratory models undoubtedly was due to the large re- <br />duction in the scaling factor. <br />Through the use of quarter and half sections, which permit[ed visual observation of the <br />washing process, flow Jibes were [raced by the addition of colored dyes to the inlet water. In the <br />case of reverse circulation, [he inlet water rises and tends to remain near the top of the cavity due <br />to gravity segregation. Continued circulation displaces it towards [he sides. As the fluid in- <br />creases in density i[ flows down [he sides of [he cavity. While the process of solution continues, <br />convection and diffusion take place simultaneously, causing flow towards the center of the hole. <br />Reverse circulation generally affords the most efficient use of the circulating water due to its tor- <br />tuous path in the cavity. <br />Figure 1. Cans o; `.:odel C,•. ¢ies. <br />2~5 <br />