Quantity Dimensions#

The ansys.units.quantity_dimensions module defines standard physical quantity dimensions, covering SI base quantities (such as mass and time) and many commonly used derived quantities (such as force, pressure, energy).

Overview#

A quantity dimension describes the physical nature of a value, such as length, time, or force. These dimensions are used internally in dimensional analysis, unit validation, and conversion.

This module provides a set of immutable, predefined dimension objects via the QuantityDimensions class. Each attribute of this class represents a Dimensions object composed from SI base dimensions.

These objects support symbolic operations such as multiplication, division, and exponentiation to allow for composition and comparison of dimensions.

Usage#

You do not create QuantityDimensions instances directly. Instead, you use the class-level attributes:

from ansys.units.quantity_dimensions import QuantityDimensions

# Access predefined dimensions
force = QuantityDimensions.FORCE
area = QuantityDimensions.AREA
pressure = QuantityDimensions.PRESSURE

# Perform dimensional checks
assert pressure == force / area

# Velocity has expected dimensional form: LENGTH / TIME
print(QuantityDimensions.VELOCITY)

# Dimensions can be compared or used in analysis
print(QuantityDimensions.ENERGY == QuantityDimensions.FORCE * QuantityDimensions.LENGTH)

Vector Quantities#

Certain quantities, such as velocity or momentum, are marked as vector quantities. For these, additional attributes are automatically generated:

  • <NAME>_X, <NAME>_Y, <NAME>_Z - Cartesian components

  • <NAME>_MAGNITUDE - scalar magnitude

Example:

QuantityDimensions.VELOCITY_X  # Cartesian component
QuantityDimensions.VELOCITY_MAGNITUDE  # Scalar form

These variants share the same dimensional structure as the base quantity.

Use Cases#

  • Validating consistency of physical equations and formulas

  • Enabling unit-aware computation and conversions

  • Providing structure to variable descriptors and unit systems