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Boundary condition setting

Updated: June 20, 2021

In XSim, you can set the boundary condition to the analyzed shape's region in the "Flow Boundary Condition" page. Select the region in navigation view on left side of the window and click Set button to set the boundary condition.

'Flow Boundary Condition' page
"Flow Boundary Condition" page

The boundary conditions that can be set are as follows.

Table 1. The boundary conditions that can be set
Boundary conditionDescription
Fixed flow velocitySets the flow velocity at the region as a 3-dimensional vector. The unit is m/s.
Fixed mass flow rateSets the flow rate through the region in mass. The unit is kg/s.
Fixed volume flow rateSets the flow rate through the region in volume. The unit is m3/s.
Fixed normal direction velocitySets the flow velocity at the region as a scalar value. The direction of the flow is normal to the region. The unit is m/s.
Fixed static pressureSets the static pressure at the region. The unit is Pa.
Fixed total pressureSets the total pressure (=static pressure + dynamic pressure) at the region. The unit is Pa.
Natural inflow/outflowSet the region as a surface with inflow/outflow can be occur. Either inflow or outflow is determined by the calculated flow near the surface.
Slip wallSets the region as a frictionless wall.
Stationary wallSets the region as a wall with zero velocity.
Moving wallSets the region as a wall with a constant velocity. The velocity is set by a 3-dimensional vector in m/s.
Rotating wallSets the region as a wall with a constant rotational speed. This is defined by the rotation axis and the rotation speed (in °/s). This condition is usually used to set a cylindrical or spherical region.
SymmetrySets the region as plane of symmetry and the exact same flow is occurring in reverse from the opposite side.
Boundary face mappingSets the pair of region and the flow velocity and pressure on one region will be mapped to the other.

For thermal analysis, the following thermal boundary conditions can be set to the walls (slip wall, stationary wall, moving wall, and rotating wall).

Table 2. The thermal boundary conditions that can be set
Boundary conditionDescription
AdiabaticSets the wall to be insulated with no heat transfer.
Fixed temperatureSets the wall to keep a constant temperature. The unit is K (Kelvin).
Fixed heat fluxSets the heat flux (the amount of heat that crosses a unit area in a unit time) and the initial temperature. The units are W/m2 and K.
Fixed heat sourceSets the heat generation rate and initial temperature. The units are W and K.
Fixed heat transfer coefficient Sets the heat transfer coefficient (that depends on the flow and wall surface conditions), the initial temperature, and the temperature outside the analysis area. The units are W/(m2・K), K, and K, respectively.