# Operating Conditions

## Introduction

In the Operating Conditions panel one can define various reference values. The content of this panel depend on the OpenFOAM version being used and the solver that is currently selected. For certain solvers this panel is not visible at all.

## Gravitational Acceleration

The value of gravitational acceleration g vector can be changed. By default, this vector points in a negative Z direction. Additionally, for certain solvers and OpenFOAM version you can define the location of the reference height $$h_{ref}$$. This value is mainly used for multiphase solvers in boundary condition calculations and in most cases can be left with the default value.

## Reference Pressure

For incompressible solvers, if pressure is not fixed by a boundary conditions (by using Pressure Inlet or Outlet boundary conditions), you need to fix pressure in one of the computational cells. For the most cases you can leave the default values since in the case of incompressible solvers only pressure differences are important and not the absolute values.

### Reference Pressure Location

There are two ways to define where the pressure should be fixed:

• Cell

• Point

When you select the Cell option you need to specify the index of the cell.

When you select the Point option you need to specify the location where the pressure should be fixed.