Home / How to Set Analysis Condition / Thermal Analysis [Watt] / Automatic Fluid Domain Creation

Automatic Fluid Domain Creation

When a solid domain has been created, automatically creates a fluid domain inside or outside the solid domain.

The details are explained below.

Fluid Domain Setting（common）

Setting Item

Note

Fluid Material

Selects, from the material DB, the material of the fluid to be automatically created.

To specify a new material, create the new material referring to [How to Create New Material Property] and select it.

Mesh Size of Fluid Domain

Set the mesh size of the fluid domain automatically.

If selected, the mesh size of the air domain to be automatically created is automatically determined as follows.

Mesh size: one-tenth of the longest part of the fluid domain

Mesh Size of Air Domain

To manually set the mesh size of the fluid domain to be automatically created, enter the intended mesh size.

Internal Flow specified (Fluid/Fluid-Thermal/Thermal Analysis)

・A fluid domain is created inside the solid domain.

・The fluid material is automatically set to the closed space.

・If there is an opening, lids (shown in yellow-green) with a flow boundary set must be created.

・If a material property or body attribute is set to the lid, the material applies to the internal fluid.

Refer to the tutorial-Fluid Analysis_2 (Bernoulli, Diffusion Analysis: Automatic Internal Fluid Creation)-
and the example-Example 24: Diffusion Analysis by Automatic Internal Flow Creation.

Automatic creation is schematically illustrated below.

Analysis Type	Automatically Created Fluid (Illustration)
Fluid Analysis/Fluid-Thermal Analysis
Thermal Analysis

	Solid Domain
	Automatically created fluid domain
	Sheet body with boundary conditions set (If 2D analysis/axisymmetric analysis, a wire body.)

External Flow specified (Fluid/Fluid-Thermal Analysis)

・A fluid domain is created surrounding the solid domain.

・The fluid material is automatically set to the surrounding fluid domain.

Refer to the tutorial-Fluid-Thermal Analysis (Bernoulli_Watt, Automatic External Fluid Creation)-
and the examples-Example 3: Cooling of IC by Forced Convection and Example 6: Cooling of IC by Natural Convection.

Fluid Domain Setting (dedicated to external domain)

Setting Item

Note

External Flow Direction

Specifies the flow direction of the external flow.

Automatic creation is schematically illustrated below.

L is a scale factor for the fluid domain. Multiplying the model length by the factor gives the length of the fluid domain.

Lb is a scale factor for the back, upper, or lower fluid domain. Multiplying the model length by the factor gives the length of the corresponding fluid domain.

External Flow Direction	Automatically Created Fluid (Illustration)
None
Natural convection in the +Z direction (heat source)
Natural convection in the -Z direction (heat absorber)
Forced convection in the +X direction
Forced convection in the -X direction
Forced convection in the +Y direction
Forced convection in the -Y direction
Forced convection in the +Z direction
Forced convection in the -Z direction

	Solid Domain
	Automatically created fluid domain
	Sheet body with boundary conditions set (If 2D analysis/axisymmetric analysis, a wire body.)

External Flow Velocity

This setting is available if forced convection is specified for the external flow direction.

Specify the velocity of the external flow in a specified direction.

Scale Factor for Fluid Domain L

Defines the size of the fluid domain created automatically by a scale factor (magnification ratio).

Multiplying the model length by the factor gives the length of the fluid domain.

The model length is the maximum of the lengths in the X, Y, and Z directions of the target model.

Scale Factor for Back, Upper, or Lower Domain of Fluid Lb

If [Natural convection in the +Z direction] is selected for the external flow direction, the external flow domain is extended upward.

If [Natural convection in the -Z direction] is selected for the external flow direction, the external flow domain is extended downward.

If [Forced convection] is selected for the external flow direction, the external flow domain is extended backward.

The fluid domain is stretched backward, upward, and downward by the model length multiplied by the scale factor for the backward, upward, and downward domains, respectively.

The model length is the maximum of the lengths in the X, Y, and Z directions of the target model.