Understanding Dynamic Viscosity: Poise and Centipoise
Dynamic viscosity, often referred to as absolute viscosity, measures a fluid's internal resistance to flow when an external force is applied. In the CGS (centimeter-gram-second) system, the primary unit is the Poise (P), named after the French physicist Jean Léonard Marie Poiseuille.
Because the Poise is a relatively large unit for many common fluids, the Centipoise (cP) is the standard unit used in industrial and laboratory settings. By definition, 1 Poise is equal to 100 Centipoise. The relationship is expressed as:
\(1 \text{ P} = 100 \text{ cP}\)
\(1 \text{ cP} = 0.01 \text{ P}\)
Practical applications of these units include:
Chemical Engineering: Determining pump sizing and pipe friction losses.
Quality Control: Measuring the consistency of paints, lubricants, and food products.
Fluid Dynamics: Calculating Reynolds numbers to determine flow regimes (laminar vs. turbulent).
Poise to Centipoise Conversion Reference Table
Poise (P)
Centipoise (cP)
0.1
10
0.5
50
1.0
100
2.0
200
5.0
500
10.0
1000
20.0
2000
50.0
5000
100.0
10000
500.0
50000
1000.0
100000
Conversion Example: 10 Poise to Centipoise
To convert a value from Poise (P) to Centipoise (cP), multiply the value by the conversion factor of 100. Follow these steps:
Identify the given value: \(10 \text{ P}\).
Apply the conversion formula: \(\text{Value in cP} = \text{Value in P} \times 100\).
The Poise is a large unit; for context, water at 20°C has a viscosity of approximately 1 cP (0.01 P). Using Centipoise allows engineers to work with whole numbers rather than small decimals, reducing the risk of calculation errors in technical specifications.
The SI unit for dynamic viscosity is the Pascal-second (Pa·s). The conversion is 1 cP = 0.001 Pa·s, or 1 mPa·s. Therefore, 1 cP is exactly equivalent to 1 millipascal-second.
"On fait la science avec des faits, comme on fait une maison avec des pierres ; mais une accumulation de faits n'est pas plus une science qu'un tas de pierres n'est une maison." "Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science than a heap of stones is a house." — Henri Poincaré (French Mathematician, Theoretical Physicist & Mining Engineer)