Class: Viscosity

The Viscosity class is a subclass of Variable designed to represent a quantity of viscosity. It uniquely handles two different types of viscosity: dynamic and kinematic. The class automatically determines the viscosity type based on the provided units and performs conversions only within that type.

Supported Units

The class distinguishes between two sets of units for dynamic and kinematic viscosity.

Dynamic Viscosity Units

The base SI unit for dynamic viscosity is Pascal-second (P.s).

Unit	str	Conversion Factor to Pascal-second (Pa.s)
Pascal-second	Pa·s	1
milliPascal-second	mPa·s	10−3
centipoise	cP	10−3
poise	P	0.1

Kinematic Viscosity Units

The base SI unit for kinematic viscosity is meters-squared per second (m²/s).

Unit	str	Conversion Factor to meter-squared per second (m2/s)
meter-squared per second	m2/s	1
centimeter-squared per second	cm2/s	10−4
millimeter-squared per second	mm2/s	10−6
centistoke	cSt	10−6
stoke	St	10−4

Class Reference

class Viscosity(value, units='Pa·s')

A class for handling viscosity measurements. The type of viscosity (dynamic or kinematic) is determined automatically based on the units argument.

Parameters:

• value : float or int
  The numeric value of the viscosity. Must be a non-negative number.
• units : str, default='Pa·s'
  The unit of the provided value. Must be one of the supported units.

Raises:

• ValueError : If value is negative or if units is not a valid unit.

Examples:

# Create a Viscosity object for a dynamic viscosity of 1e-3 Pa·s  
>>> v1 = Viscosity(1e-3, units="Pa·s")

# Create a Viscosity object for a kinematic viscosity of 1 cSt  
>>> v2 = Viscosity(1, units="cSt")

Properties

Property	Type	Description
.value	float	The numeric value of the viscosity, always stored in its base SI unit (Pacdots for dynamic, m2/s for kinematic).
.original\value	float	The numeric value as provided during initialization.
.original\unit	str	The unit as provided during initialization.
.viscosity\type	str	Indicates the type of viscosity, either "dynamic" or "kinematic".

Methods

to(target_unit)

Returns a new Viscosity object converted to the target_unit. This method can only convert between units of the same viscosity type (e.g., dynamic to dynamic). The original object remains unchanged.

Parameters:

• target_unit : str
  The unit to convert to. Must be a valid unit for the object's viscosity type.

Returns:

• Viscosity
  A new Viscosity object with the converted value and target unit.

Raises:

• ValueError : If target_unit is not a valid unit for the viscosity type.

Examples:

# Initialize a dynamic viscosity of 1 Pa·s  
>>> v_Pa = Viscosity(1)

# Convert to centipoise (cP)  
>>> v_cP = v_Pa.to("cP")

>>> print(v_cP)  
1000.0 cP (dynamic)

String Representation

• __str__(self)
  Returns a human-readable string representation of the viscosity, rounded to six decimal places, using its original value, unit, and type.
• __repr__(self)
  Returns a string representation suitable for developers and debugging, showing the original value, unit, and viscosity type.