Boundary conditions

Once the geometry of the control domain is defined, we have to proceed with setting the boundary conditions of the problem (access the Conditions menu as shown in example 1). The only condition to be applied in this example is the Velocity Field condition.

Velocity Field

The Velocity Field condition is used to fix the velocity in a surface to the velocity field given in the Data > Initial Data >RANSOL menu (fields Initial_Velocity_X, Initial_Velocity_Y and Initial_
Velocity_Z
). Those fields can define a space-time-variable dependant function and thus the Velocity Field condition can be used to specify a variable inflow. In order to do this, the corresponding Fix_Field flag has to be marked.

It is also possible to fix the Velocity (during the run) to the initial value of the function given in the above mentioned entries. In order to do this, the corresponding Fix_Initial flag has to be marked.

For this example this condition is going to be assigned to the inflow and lateral surfaces of the channel.

The options to be selected for the inflow surface are marked with “x” in the list below:

Fix Initial X

-

Fix Initial Y

-

Fix Initial Z

-

Fix Field X

x

Fix Field Y

x

Fix Field Z

x

The options to be selected for the lateral surfaces are marked with “x” in the list below:

Fix Initial X

-

Fix Initial Y

-

Fix Initial Z

-

Fix Field X

-

Fix Field Y

x

Fix Field Z

-

Pressure Field

Here we will apply the Pressure Field condition to the outlet surface of the domain. To these surfaces we will mark the Fix_Initial field. By doing this, pressure will be fixed to the initial value of the pressure function given in the corresponding Data > Initial Data >RANSOL window option.