In dynamical systems, instability means outputs or states increase without bounds. Structural beams become unstable with excessive compressive load. Atmospheric instability is a major component of Earth's weather systems
Dynamic viscosity describes fluid resistance to shearing flows. Viscosity is measured using viscometers and spans several orders of magnitude. Gases have lowest viscosities, thick liquids have highest
Non-Newtonian fluids have variable viscosity that changes with stress. Viscosity depends on shear rate or history, unlike Newtonian fluids. Constant coefficient of viscosity cannot be defined for non-Newtonian fluids
Fluid flow through pipes is commonly used in heating and cooling systems. Circular pipes are preferred for liquids due to pressure resistance. Noncircular pipes are used in heating systems with small pressure differences. Average velocity remains constant in incompressible flow
Viscosity measures fluid's resistance to movement through it. Low-viscosity fluids like water move easier than high-viscosity like honey. Viscosity results from molecular friction in fluids. Newton's equation for fluids expresses viscosity using force/area ratio
Viscosity measures internal friction of fluids, affecting flow behavior. Newton defined viscosity as force required to maintain fluid layer movement. Viscosity is measured in poise (1 poise = 100 centipoise) or Pascal-seconds