Free Surface for Rotating Components

Rotating Region is a powerful feature that is used to simulate the fluid-driving motion of rotating components. In SOLIDWORKS Flow Simulation 2021, Rotating Region can be combined with the Free Surface feature.

For this thruster, we are solving the torque and power requirements when it interacts with two separate fluids simultaneously.

But first what is the free surface feature?

Flow Simulation allows modelling the flow of two immiscible fluids with a free surface. Liquids are considered immiscible if they are completely insoluble in each other. A free surface is an interface between immiscible fluids, for example, a liquid and a gas (any pair of fluids belonging to gases, liquids or non-Newtonian liquids are allowed excluding gas-gas contact).

*Bear with me for a minute for some technical detail.

Free surfaces are modelled with the Volume of Fluid (VOF) technique by solving a single set of momentum equations and tracking the volume fraction of each of the fluids throughout the domain.

The VOF technique is based on the concept of a fluid volume fraction αq (q = 0…Nq – 1), which must have a value between 0 and 1. In a two-phase system, for example, in mesh cells (control volumes) of liquid α0 = 0 and α1 = 1, while in cells of gas α0 = 1 and α1 = 0. The location of a free surface is where αq changes from 0 to 1. In each control volume, the volume fractions of all phases sum to unity:

where Nq is the number of immiscible fluids (component phases).

Let’s get back to free surface with rotating components. Why is this such a big deal? Well for one we can now gain more insight on product performance with your rotating equipment.

In addition, you can simulate fluid flow subjected to rotating systems as mixers for items such as consumer products, pharmaceuticals, and food.

It is very easy to enable this, In the study setting Sliding is chosen for the Rotating Region, while Free Surface is enabled, and now let SOLIDWORKS do the rest.

Improve your simulation-driven design tasks with expanded capabilities and even more efficient results processing with SOLIDWORKS Flow Simulation 2021. For more information get in touch with us at We have experts waiting to assist you.

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