Fluid Mechanics Important Terms & Equations

Head Loss

the reduction in a fluid's total energy (or pressure) as it flows through a system due to friction and turbulence

Minor Losses

losses that occur in pipelines due to bends, elbows, joints, valves, etc.

Darcy’s Equation

to calculate head loss due to flow

Hydraulic Radius 

ratio of fluid conduit cross-sectional area of flow to its wetted perimeter

Bernoulli Equation

derived from the conservation of energy for a moving fluid

principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy

Continuity equation

Manning’s Equation

formula used to estimate the flow of water in an open channel, such as a stream or partially filled pipe

Surface Tension

Force / Length

Absolute Pressure

Atmospheric + Gauge

OR

Atmospheric - Vacuum

Manometer

Barometer

measures ATMOSPHERIC pressure

Energy Equation

Reynolds Number (Newtonian Fluid)

Laminar (<2,100), Turbulent (>10,000)

Hazen-Williams Equation

Used to calculate head loss due to friction in pipes

Force exerted by bend on fluid 

Venturi Meter

Used to measure the flow rate of a fluid (liquid or gas) in a pipe by converting pressure energy into velocity energy. It works by creating a pressure difference between the main pipe and a narrowed section called the throat, where fluid velocity increases and pressure decreases according to Bernoulli's principle

Venturi Effect

fluid's speed increases and pressure decreases as it flows through a constricted section of a pipe