# Farfield

A farfield volume zone defines the outer boundaries of your computational domain. It establishes the limits where freestream conditions are applied and ensures proper flow development around your geometry.

# Available Options

Option Description Applicable
Type Method of constructing the farfield always
Symmetry plane Whether to perform a half-domain symmetrical simulation always
Volume to include Which domain side to include Symmetry plane is On
Method Method for determining farfield shape Type is Automated farfield
Width Width of the wind tunnel (Y-direction) Type is Wind tunnel
Height Height of the wind tunnel (Z-direction) Type is Wind tunnel
Inlet X position X-position of the tunnel inlet Type is Wind tunnel
Outlet X position X-position of the tunnel outlet Type is Wind tunnel
Floor Z position Z-position of the tunnel floor Type is Wind tunnel
Floor geometry Type of floor configuration Type is Wind tunnel
Friction patch X X-range of the friction patch on the floor Floor geometry is Fixed floor
Friction patch width Width of the friction patch Floor geometry is Fixed floor
Center belt X X-range of the central moving belt Floor geometry is Center-belt wind tunnel or Wheel-belt wind tunnel
Center belt width Width of the central moving belt Floor geometry is Center-belt wind tunnel or Wheel-belt wind tunnel
Front wheel belts X X-range of the front wheel belts Floor geometry is Wheel-belt wind tunnel
Front wheel belts Y Y-range (inner to outer) of the front wheel belts Floor geometry is Wheel-belt wind tunnel
Rear wheel belts X X-range of the rear wheel belts Floor geometry is Wheel-belt wind tunnel
Rear wheel belts Y Y-range (inner to outer) of the rear wheel belts Floor geometry is Wheel-belt wind tunnel

# Detailed descriptions

# Type

Setting allowing the user to choose between generating the farfield in the workflow and providing the farfield as a part of uploaded geometry.

Possible selections:

  • Automated farfield - Farfield generated by Flow360 around the geometry
  • User defined farfield - Farfield geometry provided by the user, has to be assigned to an appropriate boundary condition in Boundary conditions
  • Wind tunnel - Analytic wind tunnel geometry with configurable dimensions and floor types

Notes:

  • Wind tunnel option is only available with Geometry AI.
  • By default, the volume mesher will grow boundary layers on User defined farfield and Wind tunnel boundaries. Use Passive Spacing to project or disable boundary layer growth.

# Symmetry plane

Toggle to enable half-domain simulation with a symmetry boundary condition at Y=0.

  • Default: Off

Notes:

  • When enabled, the domain is split at Y=0 and only one half is meshed and simulated
  • Significantly reduces computational cost for symmetric geometries
  • Only available when using Geometry AI with the beta volume mesher

# Volume to include

Specifies which side of the Y=0 plane to retain when symmetry plane is enabled.

Possible selections:

  • Full body - Keep the entire domain without applying symmetry (overrides the symmetry plane toggle behavior)
  • +Y - Keep the positive Y side of the domain
  • -Y - Keep the negative Y side of the domain

Note: The geometry must span across Y=0 for this setting to take effect.

# Method

Method of defining the size of an auto-generated farfield.

Possible selections:

  • Auto: Automatically determines appropriate farfield dimensions based on geometry (default radius is 50× the maximum bounding box dimension)
    • Generates a full sphere if geometry extends across Y=0
    • Creates +Y semi-sphere if geometry is entirely above Y=0
    • Creates -Y semi-sphere if geometry is entirely below Y=0
  • Quasi-3D: Creates a thin disk for quasi-3D simulations
    • Both sides of the farfield disk are treated as symmetric planes

# Wind tunnel parameters

The following parameters define the wind tunnel geometry when Type is set to Wind tunnel.

# Width

Width of the wind tunnel in the Y-direction.

  • Default: 10 m
  • Units: Length

# Height

Height of the wind tunnel in the Z-direction.

  • Default: 6 m
  • Units: Length

# Inlet X position

X-coordinate of the tunnel inlet plane.

  • Default: -20 m
  • Units: Length

Note: Must be less than Outlet X position.

# Outlet X position

X-coordinate of the tunnel outlet plane.

  • Default: 40 m
  • Units: Length

Note: Must be greater than Inlet X position.

# Floor Z position

Z-coordinate of the tunnel floor.

  • Default: 0 m
  • Units: Length

# Floor geometry

Specifies the type of floor configuration for the wind tunnel.

Possible selections:

  • Fixed floor - Static floor with a friction patch region where wall boundary conditions apply
  • Fully-moving road - Entire floor moves at freestream velocity to simulate road motion
  • Center-belt wind tunnel - Floor with a central moving belt surrounded by stationary regions
  • Wheel-belt wind tunnel - Floor with a central belt plus four additional wheel belt regions for automotive simulations

# Fixed floor parameters

The following parameters are available when Floor geometry is set to Fixed floor.

# Friction patch X

X-range (minimum, maximum) defining the extent of the friction patch on the floor.

  • Default: (-3, 6) m
  • Units: Length

Notes:

  • The friction patch applies wall boundary conditions within this X-range
  • Must be within the inlet and outlet X positions

# Friction patch width

Width of the friction patch centered at Y=0.

  • Default: 2 m
  • Units: Length

Note: Must be less than the wind tunnel width.

# Center-belt wind tunnel parameters

The following parameters are available when Floor geometry is set to Center-belt wind tunnel or Wheel-belt wind tunnel.

# Center belt X

X-range (minimum, maximum) defining the extent of the central moving belt.

  • Default: (-2, 2) m
  • Units: Length

Note: Must be within the inlet and outlet X positions.

# Center belt width

Width of the central moving belt centered at Y=0.

  • Default: 1.2 m
  • Units: Length

Note: Must be less than the wind tunnel width.

# Wheel-belt wind tunnel parameters

The following parameters are available when Floor geometry is set to Wheel-belt wind tunnel. These are in addition to the center belt parameters.

# Front wheel belts X

X-range (minimum, maximum) defining the extent of the front wheel belts.

  • Required
  • Units: Length

Note: Maximum X must be less than the minimum X of the rear wheel belts.

# Front wheel belts Y

Y-range (inner edge, outer edge) defining the lateral position of the front wheel belts.

  • Required
  • Units: Length

Notes:

  • The inner edge must be greater than half the center belt width
  • The outer edge must be less than half the wind tunnel width
  • Belts are symmetric about Y=0

# Rear wheel belts X

X-range (minimum, maximum) defining the extent of the rear wheel belts.

  • Required
  • Units: Length

Note: Minimum X must be greater than the maximum X of the front wheel belts.

# Rear wheel belts Y

Y-range (inner edge, outer edge) defining the lateral position of the rear wheel belts.

  • Required
  • Units: Length

Notes:

  • The inner edge must be greater than half the center belt width
  • The outer edge must be less than half the wind tunnel width
  • Belts are symmetric about Y=0

💡 Tips
  • Automated farfield is generally preferred for aerospace applications
  • Wind tunnel is ideal for automotive simulations requiring realistic ground effects
  • Use Wheel-belt wind tunnel floor geometry to match physical wind tunnel configurations with separate wheel pads
  • When using symmetry plane with wind tunnels, ensure your geometry is symmetric about Y=0

❓ Frequently Asked Questions

  • How do I choose between Auto and Quasi-3D farfield methods?

    Use Auto for full 3D simulations and Quasi-3D for 2D or axisymmetric cases where the flow is primarily in one plane.

  • When should I use the Wind tunnel farfield type?

    Use Wind tunnel for automotive CFD simulations where you need to model realistic wind tunnel conditions including moving floor/belts and proper inlet/outlet boundary conditions.

  • What is the difference between Fixed floor and Fully-moving road?

    Fixed floor has a stationary floor with a friction patch where boundary layer develops. Fully-moving road simulates the entire floor moving at freestream velocity, eliminating floor boundary layer effects—ideal for simulating on-road conditions.

  • How do wheel belts work?

    Wheel belts are small moving belt regions positioned under each wheel location. They move at freestream velocity to simulate tire contact with the road while the surrounding floor remains stationary.

← Mesh parameters →