Fluid Flow and Fluid Properties Flashcards

Vocabulary practice flashcards covering fundamental definitions, fluid flow regimes, classification of fluids, and physical fluid properties from CHPE3302 Fluid Flow.

Fluid Mechanics

The study of fluids either at rest (fluid statics) or in motion (fluid dynamics) and the subsequent effects of the fluid on boundaries.

Fluid

A substance in the liquid or gas phase that lacks the ability to resist deformation forces and deforms continuously under the action of a shear stress, no matter how small.

Normal Stress

The normal component of a force acting on a surface per unit area; in a fluid at rest, the normal stress is called pressure.

Shear Stress

The tangential component of a force acting on a surface per unit area ($\tau = \frac{F}{A}$), which develops when fluid particles in motion move relative to each other with different velocities.

External Flow

The flow of an unbounded fluid over a surface, such as over a plate, a wire, or a pipe.

Internal Flow

The flow in a pipe or duct where the fluid is completely bounded by solid surfaces.

Open-Channel Flow

The flow of liquids in a pipe or duct where the duct is only partially filled with liquid and forms a free surface.

Laminar Flow

The highly ordered fluid motion characterized by smooth layers of fluid, typically occurring in high-viscosity fluids at low velocities.

Turbulent Flow

The highly disordered fluid motion occurring typically at high velocities and characterized by velocity fluctuations.

Transitional Flow

A fluid flow condition that alternates between being laminar and turbulent.

Forced Flow

Fluid flow where a fluid is made to flow over a surface or in a pipe by external mechanical means such as a pump or a fan.

Natural Flow

Fluid motion caused by natural means, such as the buoyancy effect where warmer, lighter fluid rises and cooler, denser fluid falls.

Primary Dimensions

Basic physical dimensions selected as fundamental baselines, such as mass ($m$), length ($L$), time ($t$), and temperature ($T$).

Secondary Dimensions

Derived physical dimensions expressed in terms of primary dimensions, such as velocity ($V$), energy ($E$), and volume ($\mathcal{V}$).

Intensive Properties

Properties of a system that are independent of its mass, such as temperature ($T$), pressure ($P$), and density ($\rho$).

Extensive Properties

Properties of a system whose values depend on the size or extent of the system, such as total mass ($m$) and total volume ($\mathcal{V}$).

Density

The ratio of mass to volume at a point ($\rho = \frac{m}{\mathcal{V}}$), expressed in SI units as $kg\,m^{-3}$ or $kg/m^3$.

Specific Volume

The volume per unit mass ($\nu = \frac{\mathcal{V}}{m} = \frac{1}{\rho}$), which is the reciprocal of density.

Specific Weight

The weight per unit volume of a substance ($\gamma = \frac{W}{\mathcal{V}} = \rho g$), expressed in SI units as $N\,m^{-3}$ or $N/m^3$.

Specific Gravity

The dimensionless ratio of the density of a substance to the density of a standard substance at a specified temperature (typically water at $4\,^\circ\text{C}$, where $\rho_{\text{H}_2\text{O}} = 1000\,kg/m^3$).

Newton's Law of Viscosity

The physical law stating that shear stress between adjacent fluid layers is directly proportional to the velocity gradient ($\tau = \mu \frac{du}{dy}$).

Newtonian Fluids

Fluids for which the rate of deformation is linearly proportional to the shear stress, maintaining a constant dynamic viscosity (e.g., water, air, benzene).

Non-Newtonian Fluids

Fluids that do not obey Newton's law of viscosity, meaning their viscosity changes when the gradient in flow speed or shear rate changes.

Bingham Fluids

Non-Newtonian fluids that resist small shear stress and behave as solids until a specific yield stress is achieved, after which they flow (e.g., toothpaste, jellies).

Pseudoplastic Fluids

Shear-thinning non-Newtonian fluids whose viscosity decreases as the rate of deformation or shear stress increases (e.g., blood, ketchup).

Dilatant Fluids

Shear-thickening non-Newtonian fluids whose viscosity increases as the rate of deformation or shear stress increases (e.g., cornstarch, printing inks).

Rheopectic Fluids

Time-dependent non-Newtonian fluids whose viscosity increases over time under a constant shear rate or stress duration.

Thixotropic Fluids

Time-dependent non-Newtonian fluids whose viscosity decreases over time under a constant shear rate or stress duration (e.g., clays, honey).

Kinematic Viscosity

The property characterizing mass and viscous behavior defined as dynamic viscosity divided by fluid density ($\nu = \frac{\mu}{\rho}$), expressed in SI units as $m^2/s$.

Surface Tension

An effect caused by cohesive intermolecular forces in the surface layer of a liquid that causes that layer to behave as a stretched elastic membrane ($\sigma$).

Capillarity

The ability of a liquid to flow in narrow spaces without external assistance and opposing gravity, depending on liquid cohesion and adhesion to vessel walls.

Gauge Pressure

Pressure measured by a gauge relative to atmospheric pressure, excluding atmospheric pressure ($P_g = P_{abs} - P_{atm}$).

Absolute Pressure

The total pressure exerted on a system measured relative to absolute zero pressure ($P_{abs} = P_{atm} + P_g$).