Inlet-Outlet Total Temperature - Boundary Conditions

Inlet-Outlet Total Temperature is a temperature boundary condition that provides an outflow condition for total temperature. Essentially, it works similarly to Inlet-Outlet. It defines Zero Gradient for the outlet patch, but switches to Total Temperature when the reverse flow is detected on the outlet patch. The user-specified value needs to be defined in case of reverse flow.

Similarly to Total Temperature, the Inlet-Outlet Total Temperature boundary condition is used to calculate the static temperature at the domain boundary, but only when the reverse flow occurs. Otherwise, Zero Gradient is applied.

Inlet-Outlet Total Temperature boundary condition adapts the temperature field depending on the flow direction at the outlet. Under normal outflow conditions, a Zero Gradient condition is applied, which effectively extrapolates the total temperature from the interior of the domain to the patch.

The critical scenario occurs when reverse flow is detected, particularly at high velocities. In this case, the boundary condition imposes the user-specified Total Temperature, ensuring that the thermal contribution of the fluid’s kinetic energy is accurately captured.

The Inlet-Outlet Total Temperature boundary condition calculates the static temperature at the patch only when reverse flow occurs.

The formula linking total and static temperature is as follows:

\(T_p = \frac{T_0}{1 + \frac{\gamma -1}{2 \gamma} \psi |\vec u|^2}\)

where:
\(T_o\) – total temperature
\(T_p\) – static temperature at the patch
\(\gamma\) – specific heat capacity ratio
\(\psi\) – flux
\(\vec u\) – velocity vector

Inlet-Outlet Total Temperature can be selected from the drop-down menu in Boundary Condition panel. The User needs to provide the Total Temperature \(T_0\) - Figure 1.

In this section, we propose boundary conditions that are alternative to Inlet-Outlet Total Temperature. While they may fulfill similar purposes, they might be better suited for a specific application and provide a better approximation of physical world conditions.