Pascalsekunti

Pascalsekunti is the Finnish term for the pascal-second, the SI derived unit of dynamic (absolute) viscosity. It quantifies a fluid's internal resistance to flow under applied shear and is commonly denoted Pa·s, Pa s, or Pa·sec. As a derived SI unit, one pascal-second is equivalent to one newton-second per square meter (N·s/m²) and in base units to one kilogram per meter-second (kg·m⁻¹·s⁻¹).

Dynamic viscosity μ relates shear stress τ to shear rate γ̇ via τ = μ·γ̇, and it is related to kinematic viscosity ν by μ = ρ·ν, where ρ is fluid density. Practical measurements often use submultiples: 1 pascal-second equals 1,000 millipascal-seconds (mPa·s) and 1,000 centipoise (cP), so many common fluid viscosities are reported in mPa·s or cP. For reference, water at about 20°C has a dynamic viscosity near 1.0 mPa·s (≈0.001 Pa·s), while air at room temperature is on the order of 1.8×10⁻⁵ Pa·s.

The pascal-second is used across fluid mechanics, rheology, chemical engineering and meteorology to characterize lubricants, industrial fluids, polymers and gases. It complements other units of viscosity and provides a coherent representation within the SI system.