Numerical simulation has been performed to study the filling cavitybehaviour, in order to predict the velocity of the melt for the differentpressure–time (p–t) curves. The filling model involved the development and testing of a computer model based in new concept to simulatethe low pressure process – Element Compressor – developed within theframework of the NovaFlow&Solid package.2.1. Governing equations — fluid flow simulationGenerally, the molten flow in processes under low pressure conditions is considered as a laminar flow, incompressible, which meansthat the density of the fluid does not change in time or space underpressure or temperature. Moreover, in the present case the motionof fluid is governed by the principles of classical mechanics and thermodynamics for the conservation of mass, momentum and energy.Thus, the basic equations for the mass conservation law may be written as: