💥💥💥 How to define free inlet and outlet in Ansys Fluent?

 A free inlet is a type of boundary condition that allows the fluid to enter or exit the domain depending on the pressure difference. It is suitable for external or unconfined flows, such as wind tunnel simulations or open channel flows.

To define a free inlet in Ansys Fluent, you can use the pressure inlet boundary condition and set the total (stagnation) pressure to zero. This will allow the fluid to flow in or out of the domain depending on the local pressure gradient. You will also need to specify the total temperature, turbulence parameters, and other scalar properties of the flow at the inlet. For more details, please refer to this guide.

Alternatively, you can use the velocity inlet boundary condition and set the velocity magnitude to zero. This will also allow the fluid to flow in or out of the domain depending on the pressure difference. However, you will need to use a user-defined function (UDF) to update the velocity direction at each time step, based on the local flow direction. For more information, please see this forum post.

How to define free outlet in Ansys Fluent?

A free outlet is a type of boundary condition that allows the fluid to exit the domain freely without any restriction. It is suitable for external or unconfined flows, such as jet flows or exhaust flows.

To define a free outlet in Ansys Fluent, you can use the pressure outlet boundary condition and set the gauge pressure to zero. This will allow the fluid to flow out of the domain based on the local pressure gradient. You will also need to specify the backflow properties of the flow at the outlet, such as temperature, turbulence parameters, and other scalar quantities. For more details, please refer to this guide.

Alternatively, you can use the outflow boundary condition and set the mass flow rate to zero. This will also allow the fluid to flow out of the domain without any restriction. However, you will need to ensure that there is no reverse flow at the outlet, as the outflow boundary condition does not account for backflow. For more information, please see this forum post.

What is the difference between pressure outlet and outflow?

The difference between pressure outlet and outflow boundary conditions in Ansys Fluent is that:

• Pressure outlet allows you to specify the static (gauge) pressure at the outlet, and the software will calculate the mass flow rate based on the pressure gradient. You also need to define the backflow properties in case of reverse flow at the outlet. This boundary condition is suitable for cases where the outlet pressure is known or important for the simulation results.
• Outflow assumes a zero diffusion flux for all flow variables except the pressure, and the software will calculate the pressure at the outlet based on the mass conservation. You do not need to define the backflow properties, but you need to ensure that there is no reverse flow at the outlet. This boundary condition is suitable for cases where the flow is fully developed and the outlet pressure is not known or important for the simulation results.

For more information, please refer to this guide or this forum post.

What is the difference between pressure inlet and velocity inlet?

The difference between pressure inlet and velocity inlet boundary conditions in Ansys Fluent is that:

• Pressure inlet allows you to specify the total (stagnation) pressure at the inlet, and the software will calculate the mass flow rate based on the pressure gradient. You also need to define the backflow properties in case of reverse flow at the inlet. This boundary condition is suitable for cases where the inlet pressure is known or important for the simulation results¹.
• Velocity inlet allows you to specify the velocity magnitude and direction at the inlet, and the software will calculate the total pressure based on the mass conservation. You do not need to define the backflow properties, but you need to ensure that there is no reverse flow at the inlet. This boundary condition is suitable for cases where the inlet velocity is known or important for the simulation results².

For more information, please refer to this guide or this forum post.