Fluid: A substance that can flow and take the shape of its container, including liquids and gases.

Units: Standard quantities used to specify measurements, such as meters for length or seconds for time.

Basic Dimensions: Fundamental physical quantities such as mass, length, time, and temperature used to define all other quantities.

Dimensionally Homogeneous: An equation in which all terms have the same dimensions or units.

Density: The mass per unit volume of a substance, typically measured in kilograms per cubic meter (kg/m³).

Specific Weight: The weight per unit volume of a substance, often expressed as force per unit volume (N/m³).

Specific Gravity: The ratio of the density of a substance to the density of a reference substance, usually water for liquids.

Ideal Gas Law: A relation between pressure, volume, and temperature for an ideal gas, given by the equation PV=nRTPV = nRTPV=nRT.

Absolute Pressure: The total pressure measured relative to a complete vacuum.

Gage Pressure: The pressure measured relative to the local atmospheric pressure.

No-Slip Condition: The assumption that fluid in direct contact with a solid surface has zero relative velocity to the surface.

Rate of Shearing Strain: The rate at which adjacent layers of fluid move relative to each other, causing deformation.

Absolute Viscosity: A measure of a fluid's resistance to flow or deformation, also known as dynamic viscosity.

Newtonian Fluid: A fluid that exhibits a constant viscosity regardless of the applied shear stress.

Non-Newtonian Fluid: A fluid whose viscosity changes depending on the shear rate or stress applied.

Kinematic Viscosity: The ratio of absolute viscosity to fluid density, typically measured in m²/s.

Bulk Modulus: A measure of a fluid's resistance to compression, defined as the ratio of pressure change to relative volume change.

Speed of Sound: The speed at which pressure waves travel through a fluid, dependent on the medium's properties.

Vapor Pressure: The pressure at which a liquid is in equilibrium with its vapor at a given temperature.

Surface Tension: The force per unit length acting along the surface of a liquid, due to intermolecular forces, that minimizes surface area.

Pascal’s Law: A principle stating that pressure applied to a confined fluid is transmitted uniformly in all directions.

Surface Force: A force that acts on the surface of a fluid, such as pressure or shear force.

Body Force: A force that acts throughout the volume of a fluid, such as gravity or electromagnetic forces.

Incompressible Fluid: A fluid with a constant density, regardless of changes in pressure or temperature.

Hydrostatic Pressure: The pressure exerted by a fluid at rest due to the weight of the fluid above a given point.

Distribution: The manner in which a quantity, such as pressure or velocity, varies across a region of a fluid.

Pressure Head: The height of a column of fluid that produces a specific pressure at its base.

Compressible Fluid: A fluid whose density changes significantly when subjected to pressure changes, such as gases.

U.S. Standard Atmosphere: A model representing the average atmospheric pressure and temperature at different altitudes in Earth's atmosphere.

Atmosphere: A unit of pressure equivalent to the average pressure at sea level, approximately 101.3 kPa.

Absolute Pressure: The total pressure measured relative to a complete vacuum, including atmospheric pressure.

Gage Pressure: The pressure measured relative to atmospheric pressure, excluding the atmospheric component.

Vacuum Pressure: A pressure that is lower than the atmospheric pressure, often measured in reference to a vacuum.

Barometer: An instrument used to measure atmospheric pressure, typically using a column of mercury or other liquid.

Manometer: A device used to measure pressure differences between two points in a fluid, often using a liquid column.

Bourdon Pressure Gage: A mechanical device that measures pressure using the deformation of a curved, flexible tube.

Center of Pressure: The point where the total force due to pressure acts on a submerged surface.

Buoyant Force: The upward force exerted on an object submerged in a fluid, equal to the weight of the displaced fluid.

Archimedes’ Principle: The principle that states that a body submerged in a fluid experiences a buoyant force equal to the weight of the fluid it displaces.

Center of Buoyancy: The point where the buoyant force acts on a submerged or floating object, corresponding to the center of mass of the displaced fluid.

Steady Flow: A type of fluid flow where the velocity at any given point does not change over time.

Streamline: A path traced by a fluid particle that represents the direction of the fluid flow at every point.

Bernoulli Equation: A principle that relates pressure, velocity, and elevation in a moving fluid, showing energy conservation along a streamline.

Elevation Head: The potential energy per unit weight of a fluid due to its height above a reference point.

Pressure Head: The height of a fluid column that corresponds to a particular pressure exerted by the fluid.

Velocity Head: The kinetic energy per unit weight of a fluid due to its velocity.

Static Pressure: The pressure exerted by a fluid at rest or moving with no net flow velocity.

Dynamic Pressure: The pressure associated with the kinetic energy of a moving fluid, given by 12ρv2\frac{1}{2} \rho v^221​ρv2.

Stagnation Point: The point in a fluid flow where the velocity is zero, and all kinetic energy is converted to pressure energy.

Stagnation Pressure: The pressure at a stagnation point, representing the sum of the static and dynamic pressures.

Total Pressure: The sum of static pressure and dynamic pressure in a fluid flow, also called stagnation pressure.

Pitot-Static Tube: A device used to measure fluid flow velocity by comparing stagnation pressure and static pressure.

Free Jet: A fluid stream that discharges freely into the air or another fluid, unaffected by boundaries.

Volume Flowrate: The volume of fluid passing through a given cross-sectional area per unit time, typically measured in cubic meters per second (m³/s).

Continuity Equation: A mathematical statement of mass conservation in fluid flow, stating that the product of cross-sectional area and velocity is constant along a streamline.

Cavitation: The formation of vapor bubbles in a fluid due to a local drop in pressure below the vapor pressure, often leading to damage.

Flowmeter: A device used to measure the flowrate or quantity of fluid passing through a pipe or channel.

Hydraulic Grade Line: A line representing the sum of the pressure head and elevation head of a fluid at various points along its flow.

Energy Line: A line representing the total mechanical energy (including pressure, velocity, and elevation) per unit weight of a fluid throughout its flow.