CFD modelling pond dynamic processes

Abstract

The parametric pond simulation methodology AUTOPOND was developed as a tool to evaluate the effect of aerators on the sediment quality in an aquaculture pond. The methodology is capable of simulating any combination of paddlewheels and propeller-aspirators in a single pond. Pond bathymetry is modelled with a smooth bottom and a piece-wise series of inclined banks, to generally represent any convoluted shoreline. Simulations predict that a paddlewheel imparts more circulation into a pond than a propeller-aspirator of the same motor horsepower. The propeller-aspirator concentrates an intensive effect in a localized scourhole, surrounded by relatively weak bottom stress. In contrast, paddlewheel simulations predicted a wide swath of high stress, followed by an equally extensive region of moderate stress. A simulation of the combined effect of two paddlewheels and four propeller-aspirators was produced to represent a 'real world' earthen mariculture pond stocked with P. monodon. Water currents and sediment conditions reported in the real pond were comparable with the results of the simulation. Given sufficient computational resources, it is now possible to investigate the interactions of pond geometry and aerator operation with a computer. Portions of pond bottoms found to experience high shear stress are now identified for reinforcement to prevent the sedimentation of sludge in otherwise productive zones. This would result in improved feed conversion and reduced ammonia levels. Ponds and aerators can now be objectively coordinated to achieve more productive culturing conditions