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Simulation of dissolution of matter and flow in restricted geometries
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1  Department of Pharmacy, Faculty of Health Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark

Abstract: Numerical analysis has been utilized for several decades1 for solving problems where conventional analytical equations fail due to e.g. complex geometry of the dissolution vessel2. Furthermore, numerical analysis enables the visualization of the formed concentration gradients that persist during dissolution testing. Numerical analysis utilizing finite element modeling (FEM) can thus help to elucidate the dissolution process that is occurring in highly complex geometries. The FEM method can be computationally solved by the coupling of a laminar flow problem with a transport problem. The model can be solved as a stationary study by evaluating the Navier-Stokes equation for the fluid flow and the mass balance equation for the transport problem. A FEM simulation was subsequently performed for a flow through cell geometry designed for dissolution testing and the calculated dissolution rate was compared to the experimentally obtained dissolution rate. It was found that the FEM method provided excellent agreement with the experimentally obtained data. Thus, the FEM method provides new possibilities for the investigation of dissolution processes in complex geometries and encompasses the capability to visualize various phenomena related to the dissolution mechanisms. This platform could in future also be suitable for studying more complex dissolution phenomena where micelles are present in the solvent phase. Future simulations supported by dissolution studies will also explore compounds that exhibit solvent mediated recrystallization. 1. Bredehoe.Jd; Pinder, G. F. Mass-Transport in Flowing Groundwater. Water Resources Research 1973, 9, 194-210. 2. Kaunisto, E.; Nilsson, B.; Axelsson, A. Drug dissolution rate measurements - evaluation of the rotating disc method. Pharmaceutical Development and Technology 2009, 14, 400-408.
Keywords: Simulation, Dissolution