# Volume Zone

Volume zones in Flow360 allow you to define specific regions in your mesh with specialized properties. These zones can be used to control mesh refinement, specify boundary conditions, or define regions for physical modeling.

# 💨 Farfield Zone

# Overview

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

# Configuration Parameters

Parameter Description Default
Method Method for determining farfield size "Auto"

# Method Options

  • Auto: Automatically determines appropriate farfield dimensions based on geometry, 100 times the maximum dimensions of the geometry
    • 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

# ⭕️ Rotation Cylinder Zone

# Overview

A rotation cylinder volume zone is designed specifically for regions containing rotating components. It ensures proper mesh refinement and enables accurate simulation of rotating machinery.

# Configuration Parameters

Parameter Description Unit
Spacing axial Mesh spacing along the cylinder's axis length (e.g. m)
Spacing radial Mesh spacing in the radial direction length (e.g. m)
Spacing circumferential Mesh spacing around the circumference length (e.g. m)
Assigned cylinders Cylindrical components to which this zone applies -
Enclosed entities Additional geometric entities within the cylinder -

# Key Features

  • Generates concentric mesh structure ideal for rotating components
  • Can enclose other objects without intersecting them
  • Supports donut-shaped configurations for stationary centerbody placement
  • Compatible with Flow360's Rotation model

💡 Tips

General Guidelines
  • Start with coarser spacing and refine based on solution quality
  • Monitor solution convergence when adjusting zone parameters
  • Use symmetry planes when possible to reduce computational domain
  • Consider wake resolution requirements when defining zone extents

Farfield
  • The farfield boundary should typically be placed 20-100 characteristic lengths away from your geometry
  • For external aerodynamics, larger domains may be needed for wake development
  • Verify that the automatic sizing provides sufficient distance from your geometry
  • Consider computational resources when adjusting farfield size

RotationCylinder
  • Match spacing values to the expected flow features:
    • Use finer axial spacing in regions of strong axial gradients
    • Ensure adequate radial spacing for boundary layer resolution
    • Consider tip vortex resolution when setting circumferential spacing
  • Keep computational efficiency in mind when setting spacing values
  • Verify that assigned cylinders are properly aligned with rotation axes
  • Ensure enclosed entities are fully contained within the rotation cylinder

❓ Frequently Asked Questions

  • How far should I place the farfield boundary?

    The farfield boundary should typically be placed 20-100 characteristic lengths away from your geometry, depending on your specific case and flow conditions.

  • What spacing values should I use for rotation cylinders?

    The spacing values depend on your specific case, but should be fine enough to capture boundary layers and wake effects around rotating components while considering computational resources.

  • Can I have multiple rotation cylinders?

    Yes, you can define multiple rotation cylinder zones with different spacing parameters for different components.

  • 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.

🐍 Python Example Usage

 
import flow360 as fl
from flow360 import u

with fl.SI_unit_system:
    cylinder = fl.Cylinder(name="cylinder", axis=[1, 0, 0], center=[0, 0, 0], outer_radius=3, height=2)
    farfield = fl.AutomatedFarfield(method="auto")
    rotation_zone = fl.RotationCylinder(
        spacing_axial=1,
        spacing_circumferential=2,
        spacing_radial=3,
        entities=cylinder
    )

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