There is a need for buoyancy engines to modulate sensor depth for optimal positioning and station-keeping. Previously, our group developed a highly efficient Ionic Buoyancy Engine that does not have any moving parts and that may be miniaturized. The engine is an osmotic pump triggered by an electric potential change applied to electrodes in an internal closed chamber. This leads to a local reduction in the ionic concentrations near a semipermeable membrane, which in turn triggers water displacement. In this study a coupled finite element model is used to solve the electrical, chemical, osmotic pressure, and fluid domains. The Nernst-Planck and Poisson equations predict the electro-chemical activities; the osmotic pressure, based on thermodynamic considerations, predicts the pressure across the semi-permeable membrane; and finally, a laminar fluid model is implemented to predict the displacement of water. The model is compared with our previous experimental data, in particular, the effect of the surface area of the electrode and the applied electric potential. In both cases the trends in both models were matching. Finally, the numerical model is used to predict the behavior of the engine due to change in chamber size.
James Akl, Fadi Alladkani, and Barbar Akle, "Ionic buoyancy engines: finite element modeling and experimental validation," Proc. SPIE 10966, Electroactive Polymer Actuators and Devices (EAPAD) XXI, 109661E (Presented at SPIE Smart Structures + Nondestructive Evaluation: March 07, 2019; Published: 19 March 2019); https://doi.org/10.1117/12.2515390.
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