Box

Box#

A box is a rectangular prism defined by its center point and size (dimensions). Boxes can be oriented in three-dimensional space using one of two transformation methods.

Available Options#

Option	Description	Applicable
Name	Identifier for the box	always
Center	Three-dimensional coordinates of the center point	always
Size	Dimensions of the box (length, width, height)	always
Transform methods	Method of defining the box orientation	always
Axes	Two orthogonal vectors defining orientation	Transform methods is `Principal Axes`
Axis of rotation	Rotation axis vector	Transform methods is `Axis & Angle`
Angle of rotation	Rotation angle around the axis	Transform methods is `Axis & Angle`

Detailed Descriptions#

Name#

Identifier for the box volume entity.

Required

Note: Names are not required to be unique, but using descriptive unique names is recommended for clarity.

Center#

Three-dimensional coordinates (X, Y, Z) defining the center point of the box.

Required
Units: Length

Size#

Three-dimensional dimensions (length, width, height) of the box along its principal axes.

Required
Units: Length

Note: The size corresponds to the full extent along each axis, not half-lengths.

Transform methods#

Boxes can be oriented in three-dimensional space using one of two methods:

Axes#

Defines the box orientation using two orthogonal vectors.

Required (when using this method)

Notes:

The two axes must be orthogonal (perpendicular) to each other

First axis (row 1) defines the primary direction (aligns with size X)

Second axis (row 2) defines the secondary direction (aligns with size Y)

Third axis is automatically computed to complete the right-handed coordinate system

Axis & Angle#

Defines the box orientation using a rotation axis and angle from the default orientation.

Axis of rotation#

The axis vector (X, Y, Z) around which the box is rotated.

Default: (0, 0, 1)

Note: The axis is normalized internally.

Angle of rotation#

The angle of rotation around the specified axis.

Default: 0 degrees
Units: Angle

Note: Positive angles follow the right-hand rule around the rotation axis.

💡 Tips

Use boxes for rectangular refinement zones in wakes or regions of interest
Align the box with the expected flow direction for wake capture
For rotated boxes, the Principal Axes method provides more intuitive control
Consider using multiple overlapping boxes for complex L-shaped or T-shaped regions

❓ Frequently Asked Questions

What happens if I don’t specify orientation?

The box will align with the global coordinate system axes (no rotation).
Can I resize a box after creation?

Yes, you can modify the size parameters at any time before meshing.
How do the axes relate to the size dimensions?

The first axis corresponds to size[0], the second axis to size[1], and the computed third axis to size[2].

🐍 Python Example Usage

import flow360 as fl

# Box using axis and angle rotation
box = fl.Box(
    name="wake_region",
    center=(2, 0, 0) * fl.u.m,
    size=(4, 1, 1) * fl.u.m,
    axis_of_rotation=(0, 1, 0),
    angle_of_rotation=15 * fl.u.deg
)

# Box using principal axes
box_axes = fl.Box.from_principal_axes(
    name="refinement_box",
    center=(0, 0, 0) * fl.u.m,
    size=(2, 1, 0.5) * fl.u.m,
    axes=[(1, 0, 0), (0, 1, 0)]
)

Box

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