Fluid Mechanics

The study of fluids - liquids and gases. Involves velocity, pressure, density and temperature as functions of space and time

Absolute or Dynamic Viscosity Online Converter

Convert between dynamic or absolute viscosity units - Poiseuille, Poise, centPoise and more

Absolute, Dynamic and Kinematic Viscosity

Dynamic, absolute and kinematic viscosities - convert between CentiStokes (cSt), centipoises (cP), Saybolt Universal Seconds (SSU) and degree Engler

Air - Altitude, Density and Specific Volume

The density and the specific volume of air varies with elevation above sea level

Air - Temperature, Pressure and Density

Air density for pressure range 0 - 1000 psi and temperature range 30 - 600 deg F

Air Duct Components and Minor Loss Coefficients

Minor loss - pressure or head loss - coefficients for air duct distribution systems components

Archimedes' Law

The forces acting on a body submerged in liquid

Baumé's Hydrometer

Degree Baumé converted to Specific Gravity

Bernoulli Equation

Conservation of energy - non-viscous, incompressible fluid in steady flow

Bulk Modulus and Fluid Elasticity

Introduction and definition of Bulk Modulus Elasticity - commonly used to characterize compressibility of fluids


The resultant force acting on a submerged body


Capillarity or capillary action is the ability of a narrow tube to draw a liquid upwards against the force of gravity

Carbon Dioxide Concentration in Rooms

Carbon dioxide concentration in rooms can be used to indicate air quality and ventilation system efficiency

Cauchy Number

Introduction to the Cauchy Number

Cavitation - an Introduction

Cavitation occurs in fluid flow systems where the local static pressure is below vapor pressure

Cavitation Number

An introduction to and a definition of the Cavitation Number

Center of Gravity - Center of Buoyancy

Stability - center of gravity and center of buoyancy

Chezy Equation

Conduits flow and mean velocity - the Chezy equation

Colebrook Equation

Calculating friction loss coefficients in pipes, tubes or ducts

Compressible Gas Flow - Entropy

Calculating entropy in a compressible gas flow

Compression and Expansion of Gases

Isothermal and Isentropic compression and expansion processes

Conservation of Mass

The Law of Conservation of Mass states that mass can neither be created or destroyed

Darcy-Weisbach Pressure and Head Loss Equation

The Darcy-Weisbach equation can be used to calculate the pressure or head loss due to friction in ducts, pipes or tubes

Density of a Liquid - when Changing Pressure and Temperature

Density and specific volume of a liquid when changing pressure or temperature

Density, Specific Weight and Specific Gravity

An introduction to density, specific weight and specific gravity - formulas with examples

Drag Coefficient

The drag coefficient express the drag of an object in a moving fluid

Dynamic Absolute Viscosity Converting Chart

Absolute Dynamic viscosity converting chart - with units like Poiseuille - Poise - centiPoise and more

Dynamic Pressure

Dynamic pressure is the kinetic energy per unit volume of a fluid

Dynamic Viscosities for some common Liquids

Absolute or dynamic viscosities for some fluids

Energy and Hydraulic Grade Line

The hydraulic grade and the energy line are graphical presentations of the Bernoulli equation

Entrance Length and Developed Flow

The entrance length is the length in a tube or duct after an obstruction until the flow velocity profile is fully developed

Equation of Continuity

The Equation of Continuity is a statement of mass conservation

Equation of Mechanical Energy and Bernoulli

The mechanical energy equations in terms of Energy per Unit Mass, Energy per Unit Volume and Energy per Unit Weight involving head

Equations in Fluid Mechanics

Common fluid mechanics equations - Bernoulli, conservation of energy, conservation of mass, pressure, Navier-Stokes, ideal gas law, Euler equations, Laplace equations, Darcy-Weisbach Equation and more

Equivalent Diameter

Convert rectangular and oval duct geometry to a equivalent circular diameter - online calculator with imperial and SI-units

Euler Equations

The behavior of ideal compressible gas can be described with Euler equations

Euler Number

Introduction to the Euler Number used in fluid mechanics

Flow Coefficient Cv and Flow Factor Kv

Comparing the flow coefficient Cv with the flow factor Kv

Flow Section Channels - Geometric Relationships

Geometric relationships in flow channels - area, wetted perimeter and hydraulic diameter

Fluid Mechanics - Imperial and SI Units Dimensions

Imperial (USCS) and SI dimensions and units terminology in fluid mechanics

Friction Coefficient with Laminar Flow

Laminar flow and friction coefficient

Froude Number

Introduction to the Froude Number

Gas Mixtures and Properties

Special care must be taken for gas mixtures when using the ideal gas law, calculating the mass, the individual gas constant or the density

Gases - Ratios of Specific Heats

Ratios of specific heats for gases in constant pressure and constant volume processes

Hazen-Williams Coefficients

Hazen-Williams coefficients for common piping materials

Hazen-Williams Equation - calculate Head Loss in Water Pipes

Friction head loss (ftH2O per 100 ft pipe) in water pipes can be estimated with the empirical Hazen-Williams equation

Heating Systems and Steel Pipes - Pressure Loss Diagram

Steel pipes and tubes - pressure loss diagram for hot water heating systems

Hydraulic Diameter

Hydraulic diameters of pipes and ducts

Hydrostatic Force acting on a Submerged Surface

Thrust forces acting on submerged surfaces

Hydrostatic Pressure

Depth and hydrostatic pressure

Ideal Gas Law

The density of a gas is related to temperature and pressure

Isentropic Flow

Constant entropy flow is called isentropic flow

Jet Discharge Propulsion

Propulsive force or thrust induced by an incompressible jet flow

Kinematic Conversion Diagram

Convert between Centistokes, Saybolt and Redwood seconds

Kinematic Viscosity - Online Converter

Convert between different kinematic viscosity units - centistokes, poise, lentor and more

Laminar, Transitional or Turbulent Flow

When calculating heat transfer or pressure and head loss it is important to know if a fluid flow is laminar, transitional or turbulent

Laplace Equation

The Laplace equation is important in fluid dynamics describing the behavior of gravitational and fluid potentials

Lift and Drag

Body - like an airfoil - in a fluid flow and lift and drag

Liquid Flow when Draining Containers or Tanks

Liquid velocity and volume flow

Liquids - Kinematic Viscosities

Kinematic viscosities of some common liquids - motor oil, diesel fuel, peanut oil and many more

Mach Number

Introduction to the Mach Number

Major Loss Online Calculator using the Darcy-Weisbach Friction Loss Equation

An online major loss calculator based on the Darcy-Weisbach friction loss equation. Energy (or head) loss is expressed in length units

Major loss in Ducts, Tubes and Pipes

Major loss - head loss or pressure loss - due to friction in ducts, pipes and tubes

Manning's Formula for Gravity Flow

Manning's equation for calculating gravity flow in open channels

Manning's Roughness Coefficients

Manning's roughness coefficients for common materials

Mass and Weight

Mass and Weight - the Gravity Force

Minor Loss Coefficients in Pipes and Tubes Components

Minor loss coefficients for common used components in pipe and tube systems

Minor Loss in Pipe or Duct Components

Minor loss, pressure or head loss in pipe, tube and duct system components

Mixing Fluids

Mass and temperature in mixed fluids

Mixtures, Solutions and Suspensions

The difference between mixtures, solutions and suspensions

Moody Diagram

A Moody diagram that can be used to estimate friction coefficients

Moody Friction Flow Factor

Online Moody friction flow factor calculator - as used in the Darcy-Weisbach major loss equation

Motor Oils - Dynamic Viscosity

Dynamic viscosities for motor oils SAE 10 to 50 - temperature range 0 - 100 deg C

Navier-Stokes Equations

The Navier-Stokes equations are the fundamental partial differentials equations used to describe incompressible fluid flows


Gas flow through nozzles - sonic chokes

Oil Viscosity - Convert Values

Convert between common oil viscosity units

Orifice, Nozzle and Venturi Flow Rate Meters

The orifice, nozzle and venturi flow rate meters use the Bernoulli Equation to calculate the fluid flow rate using pressure difference through obstructions in the flow

Pascal's Laws

Pascal's laws relates to pressures in fluids

Pipes - in Serie and Parallel

Pressure loss in pipes in series and parallel

Pipes and Fluid Flow Velocities

Calculate fluid flow and pipe velocities in pipes and tubes

Poiseuille's Formula

The volume flow discharged through a smooth-walled circular pipe

Prandtl Number

The Prandtl Number is a dimensionless number approximating the ratio of momentum diffusivity to thermal diffusivity


Introduction to pressure - psi and Pa - online pressure units converter

Pressure Coefficient

The ratio of pressure forces to inertial forces

Pressure Energy

Pressure energy in a incompressible fluid

Pressure Gradient Diagrams

A pressure gradient diagram is a graphical presentation of the static pressure throughout a fluid flow system

Pressure Units - Online Converter

Convert between pressure units like Pa,  bar, atmosphere, pound square feet, psi and more

Pump Affinity Laws

Turbo machines affinity laws are used to calculate volume capacity, head or power consumption in centrifugal pumps with changing speed - rpm - or wheel diameters

Pumps, Compressors, Blowers and Fans

Comparing pumps, compressors, blowers and fans

Reynolds Number

Introduction and definition of the dimensionless Reynolds Number - with online calculators


A measure of the maximum amount of a solute that can be dissolved in a solvent

Specific Work of Turbo Machines - Pumps, Compressors and Fans

Specific work from pumps, fans, compressors and turbines

Speed of Sound Formulas

Calculation formulas for velocity of sound - sonic velocity - in gases, fluids or solids

Static Pressure and Pressure Head in Fluids

Static pressure and pressure head

Stokes' Formula

The force of viscosity acting on a smooth sphere

Strouhal Number

Introduction to the Strouhal Number

Surface Tension

Surface tension of liquids like water, mercury, oils and more

Technical Terms in Fluid Mechanics

Some of the most commonly used technical terms in fluid mechanics

The Individual and Universal Gas Constants

The Individual and Universal Gas Constants used in fluid mechanics and thermodynamics

Total Pressure or Head Loss in Pipe or Duct Systems

Major and minor loss in pipe, tubes and duct systems

U-Tube Manometer

The inclined and vertical u-tube manometers are inexpensive and common in the differential pressure measurement with flow meters like pitot tubes, orifices and nozzles

Velocity Head

Dynamic pressure and velocity head

Viscosity Converting Chart

Convert between viscosity units like Centiposes, milliPascal, CentiStokes and SSU

Viscous Liquids - Friction Loss

Friction loss in steel pipes - for fluids with viscosities ranging 32 - 80000 SSU

Water - Absolute or Dynamic Viscosity

Absolute or dynamic viscosity of water in centipoises for temperatures between 32 - 200oF

Water - Dynamic and Kinematic Viscosity

Viscosity of water at temperatures ranging 0 - 100 oC (32 - 212 oF) - Imperial and SI Units

Water Flow in Tubes - Reynolds Number

Clean cold waterflow in pipes and the Reynolds number

Water Systems - Valves and Kv diagram

Kv diagram for sizing control valves

Water and Speed of Sound

Speed of sound in water at temperatures ranging 32 - 212oF (0 - 100oC) - Imperial and SI units

Weber Number

Introduction to the Weber Number

Wind Energy

Available wind energy

Wind Power

Power generated from the wind

Wind Shear

Wind slowed down at the surface by trees and obstructions - wind shear

Wind Turbine Power Calculator

Online wind turbine calculator

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