NUCL350 Exam 1 Definitions

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=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.

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.

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

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.