Pascalosekunti

Pascalosekunti is a unit of dynamic viscosity. It is named after Blaise Pascal and the second (a unit of time). The pascalosekunti (symbol: Pa·s) is the SI derived unit for dynamic viscosity, equivalent to one pascal multiplied by one second. This unit is often used in fields such as fluid dynamics and rheology.

Dynamic viscosity, often denoted by the Greek letter eta (η), measures a fluid's internal resistance to flow. It describes the shear stress required to move one layer of fluid past another layer at a given velocity. A fluid with a high dynamic viscosity, such as honey, flows more slowly than a fluid with a low dynamic viscosity, such as water. The pascalosekunti quantifies this resistance.

The relationship between shear stress (τ), dynamic viscosity (η), and the velocity gradient (du/dy) is described by Newton's law of viscosity: τ = η (du/dy). In SI units, shear stress is measured in pascals (Pa), and the velocity gradient is measured in reciprocal seconds (s⁻¹). Therefore, dynamic viscosity has units of Pa·s.

The pascalosekunti is a relatively large unit, so its sub-multiples, such as the millipascalosekunti (mPa·s), are commonly used for many practical applications. For instance, water at room temperature has a dynamic viscosity of approximately 1 millipascalosekunti. This unit provides a standardized way to compare the flow properties of different liquids.