Theoretical Background
FEniCS is an open-source package for automated computational modelling to solve partial differential equations using finite element methods. FEniCS consists of several building blocks and is implemented in both C++ and Python.
FEniCS has a friendly and easy-to-use syntax, which simply represents the weak-form of the partial differential equation. However, developing in the FEniCS environment requires a background in Python programming and PDE analysis.
Composite on Clouds is built on top of FEniCS, with improving the solver by adding a visualization core and many different capabilities to help the user with creating an analysis, modifying parameters, and interpreting the results.
For more information on FEniCS and a tutorial on solving PDEs using this tool, look at here
The basic idea of the control volume finite element approach is to use a discretized equation to locally account for the mass conservation equation. Each node has a volume of influence, and the mass conservation describes the change in fluid mass storage for the volume which is balanced by the input and output of mass through the volume surfaces. For a pressure-driven flow, the flux of mass depends on the physical properties of each control volume and the distribution of the pressure in the domain.
In the CV-FEM method, the domain is discretized with finite elements and after that, a representative volume is assigned to each node. In the numerical simulation, the pressure is solved in the available region, region with resin, and then velocity is calculated based on Darcy's law. The velocity is used to find the flux of resin to the nearby control-volumes. The time-step is assumed to be the time required to fill one CV. Using the velocity and time-step, we update the saturation of resin for each CV. The flow-front is determined by processing the saturation in the current time-step. As the flow-front moves in the domain, the available region expands.
In many RTM methods, a distribution layer is used on top of the actual preform to help in the flow process. Composite on Clouds uses an averaging method to find the permeability of the domain, considering the permeability and thickness of each preform in each section.
In high-pressure RTM, the pressure in some points of the preform might exceed a maximum value and some layers of preform fabric would move due to this high pressure. In order to help the designer to optimize the preform geometry and eliminate fibre wash, we added a high-pressure profile contour to the outputs of each analysis. By analyzing this contour, the designer can find the high-pressure points and change the geometry in such a way to reduce the pressure in those regions. The following figure shows the high-pressure distribution in a b-pillar composite part (similar to the test-case mentioned here).
