The classical, complete Navier-Stokes equations (including inertia) for non-Newtonian viscosity are the slowest but most complete solver option. Inertia is the mass-velocity term in the momentum equations. This means that if fluid has a velocity, it will tend to keep that velocity, unless some other force acts upon it. Other forces can include the viscous forces (stresses) which come from shear deformation. In the particular case of injection molding of polymers, the viscous stresses are very large compared to the inertia terms. This is because of the relatively high viscosity of polymer melt (compared to other fluids such as air) and the narrow cavities through which polymers are injected. This is equivalent to saying: In injection molding, the Reynolds number of the flow is usually much less than one and so inertia terms are not significant.
Generally, use the inertia option when the Reynolds number is expected to be greater than 1. Even then, consider whether your analysis needs to have this accuracy. There might be high velocities in a small gate region, but if the gate is only a small contribution to the total injection pressure, there may be little difference in results with or without inertia.
If the inertia term is removed from the momentum equations, the calculations are simplified and so make some analysis speed improvement. Since in most cases, the dropping of the inertia term will make no difference to injection molding predictions, this option is a good choice for most users. A Navier-Stokes analysis without inertia terms is sometimes called a Stokes analysis. The speed saving is about 10% to 30%.
By default, the inertia option is turned off.
In most molding situations, the force of gravity is insignificant compared to other forces, such as those brought about by injection and stress. If you need to model the effects of gravity, you can turn on this option.
Using a GPU (Graphics Processing Unit) card enables the analysis to perform numerical intensive calculations on the card itself, resulting in a faster analysis time for 3D flow analyses. When this option is used in conjunction with parallelization, greater speed improvements can be achieved.
By default, GPU technology is turned on.