Gravity

Use the Gravity Vector for buoyancy driven flows (natural convection) or when solving for hydrostatic pressure. Because most such analyses occur on Earth, make sure Earth is selected as the Gravity Method (it is by default) and indicate the direction of gravity in your model with a unit vector. For example, if your model is constructed such that “down” is in the negative Y direction, the unit vector for gravity should be:

0, -1, 0

For buoyancy driven flows or flows with hydrostatic pressure on other planets (or where the gravity is different from that on Earth), select Components as the Gravity Method, and enter the magnitude (in the analysis units) and the direction of the gravity vector.

Note: Be sure to choose a buoyancy material or set the density to vary with equation of state on the Material Dialog

A gravity vector is not needed for forced convection flows.

To include gravity as a force acting on a moving solid, assign a driving or resistive force equal to the force imparted from gravity. The gravitational force may be added to an additional driving or resistive force, if necessary. It is not necessary to specify a gravity vector on the Solve dialog for moving solids unless flow buoyancy is simulated.

Note: You can include both hydrostatic pressure and buoyancy in your analysis. However, depending on temperature gradients, the effects of the different phenomena could mask one another.

Example of setting a gravity vector