Home / Examples / Fluid Analysis [Bernoulli] / Example 13: Room Ventilation (Air Age Calculation)

Example 13: Room Ventilation (Air Age Calculation)

Ventilation in the room is analyzed.
Air age, air residual lifetime, and air lifetime are analyzed using diffusion analysis.
See Diffusion Analysis of technical note for more information about air age, air residual lifetime, and air lifetime.
Steady-state analysis of the fluid solver is applied and air age is solved by diffusion analysis.
Unless specified in the list below, the default conditions are applied.

Item	Tab	Setting
Solver	Solver	Fluid Analysis [Bernoulli]
Analysis Type	Fluid Analysis	Steady-state Analysis
Setup Details	Fluid Analysis Detailed Setting	Select [Calculate quasi-steady state in the case of non-convergence].
Diffusion Analysis	Fluid Analysis Diffusion Analysis Setting	Select Execute diffusion analysis Analysis Type: Air Age Analysis
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.

Isosurface contours of the air age are shown below. Specified values are 10[s], 20[s], and 30[s].

The isosurface indicates how far the air flows into the room from the door.

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

	Isosurface Contour
Air Age Specified Value for Isosurface: 10 [s]
Air Age Specified Value for Isosurface: 20 [s]
Air Age Specified Value for Isosurface: 30 [s]

Isosurface contours of the air age are shown below.

The place near the wall has larger values, indicating its ventilation will take longer time.

Isosurface contours of lifetime of the air [normalization] are shown below.

Efficient ventilation is achieved where the value is 1 or less.

The efficiency of ventilation is deteriorated where the value is greater than 1.

Near the wall, the value is 4 or more. Required ventilation is four times the usual.