Example 12: Room Ventilation

Ventilation in the room is analyzed.
Diffusion analysis simulates how air is replaced with another air by ventilation, where air before ventilation is “1” and air after ventilation is “0”.
See Diffusion Analysis of technical note for more information on air replacement in the transient analysis.
Steady-state mode of the fluid analysis and transient mode of the diffusion analysis are applied.
Unless specified in the list below, the default conditions are applied.

Item

Tab

Setting

Solver

Fluid Analysis [Bernoulli]

Analysis Type

Fluid Analysis

Steady-state Analysis

Timestep

Transient Analysis

Timestep: Specified

No.	Calculation step	Output interval	Timestep [s]
1	60	1	1

Setup Details

Fluid Analysis
Detailed Setting

Enable [Calculate quasi-steady state in the case of non-convergence].

Diffusion Analysis

Fluid Analysis

Diffusion Analysis Setting

Select Execute diffusion analysis

Analysis Type: Transient Analysis

Type and Unit of Diffusion Quantity: No Unit

Initial Value: 1

Meshing Setup

Mesh

General Mesh Size: 0.3 [m]

The air domain is shown as below. The model represents a room with a ventilator and a door. The door is assumed to be opened.

Body Number/Type	Body Attribute Name	Material Name
3/Solid	Room	000_Air *

* Available from the material DB

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Setting
Door/Face	Fluid	Inlet/Outlet	Natural inflow/outflow
Fan/Face	Fluid	Outlet	45 [m3/min]

Streamlines of the quasi-steady state are shown below.

The isosurface contours after 10 [s], 20 [s], and 30 [s] are shown as below. Specified value is 0.5.

The isosurface at 0.5 represents the boundary of old air and new air.

You can see the boundary moves from the door toward the ventilator over time.