2-D hydrodynamic model simulating paddlewheel-driven circulation in rectangular shrimp culture ponds

This study surveyed and simulated paddlewheel-driven circulation in rectangular shrimp culture ponds. Paddlewheels are widely used for highly intensive culture ponds to improve reaeration and circulation. From flow measurements, the major circulation pattern was found to be a single large eddy with strong and weak flows, respectively, along the pond bank and the eddy centre. A two-dimensional depth integrated numerical model was refined to represent the circulation, with acceleration of the paddlewheel given as a shaft force divided by the water mass driven away by paddlewheel blades. The model was applied to a pond F, deploying a single paddlewheel and calibrated for a mass correction factor alpha in the range 15-20 and for a dimensionless eddy viscosity constant gamma of 6. The model was then applied to two ponds A and B, with four paddlewheels deployed at four corners, respectively. The measured and predicted currents were processed using regression analysis to show both the correlation coefficients and gradients; i.e. 0.9067, 1.0393 for direction and 0.6691, 0.8307 for speed in pond A and 0.8269, 1.0075 for direction and 0.7138, 0.9362 for speed in pond B. It was concluded from these results that the model could deal with the paddlewheel-driven jet flow in a simple way to that of using a mass correction factor alpha, first shown in this study and giving good prediction. Therefore, the model provides a useful tool to predict horizontal circulation and an insight into the circulation-related sedimentation and water quality in shrimp ponds. (C) 2004 Elsevier B.V. All rights reserved.