Fluid Mechanics, Hydraulics, and Soil Mechanics Review

Practice flashcards covering essential vocabulary and concepts from Fluid Mechanics, Hydraulics, and Geotechnical Engineering lecture notes.

Practical fluids

Fluids that possess viscosity, surface tension, and compressibility.

Specific weight of water

Defined as $1000\,kg/m^3$ at a temperature of $4^{\circ}C$, a normal pressure of $760\,mm$, and at mean sea level.

Cohesion

The property due to which molecules of fluids get attracted to each other, causing falling drops of water to become spheres.

Adhesion

the attraction between fluid molecules and a surface, such as the walls of a glass tube.

Compressibility

The property of fluids that causes them to change volume under external pressure.

Specific weight of sea water

A value higher than that of pure water due to its dissolved salts.

Newtonian fluid

A type of fluid to which water belongs.

Barometers

Instruments specifically used to measure atmospheric pressure.

Piezometers

Instruments used to measure very low pressure.

Manometers

Instruments used to measure pressure in water channels, pipes, and similar conduits.

Differential manometers

Instruments used to measure the difference in pressure between two points.

Vacuum pressure

Pressure that is less than atmospheric pressure; also known as suction pressure or negative gauge pressure.

Gauge pressure

The value calculated as Absolute pressure $-$ Atmospheric pressure.

Metacentre

The point that must be above the centroid for a floating body to attain stable equilibrium.

Centre of buoyancy

The centroid of the volume of fluid displaced by a floating or submerged body.

Steady flow

Flow in which the conditions, such as velocity or pressure at a point, do not change with respect to time.

Uniform flow

Flow where the size and shape of the cross-section remain constant over a particular length.

Continuity equation

An equation based on the principle of conservation of mass that relates the mass rate of flow along a stream line.

Stream line flow

Flow in which each liquid particle has a definite path and the paths of adjacent particles do not cross.

Bernoulli's equation assumptions

Includes uniform velocity across cross-sections, no external forces except gravity, and no energy loss during flow.

Reynold number ($R_e$)

The ratio of inertia forces to viscous forces; in pipes, flow is laminar if $R_e < 2100$ and turbulent if $R_e > 3000$.

Froude number

The ratio of inertia forces to gravitational forces acting in a flow.

Hydraulic radius

A value equal to the area divided by the wetted perimeter ($A/P$).

Pitot tube

An instrument used for measuring the velocity of flow.

Ideal fluid

A theoretical fluid that is both frictionless and incompressible.

Hydraulic jump

A phenomenon in an open channel where a rapidly flowing stream abruptly changes to a slowly flowing stream, causing a distinct rise of the liquid surface.

Metacentric height

The distance between the metacentre and the centre of gravity of a body.

Degree of consolidation

A value that is directly proportional to time and inversely proportional to the square of the drainage path.

Terzaghi's bearing capacity factors

The factors $N_c$, $N_q$, and $N_{\gamma}$, which are functions of the angle of internal friction.

Degree of saturation ($S$)

The ratio of the volume of water to the volume of voids; its valid range is expressed as $0 \leq S \leq 100\%$.

Plastic state

The state of a soil mass when its natural water content lies between the liquid limit and the plastic limit.

Permeability of clayey soil

The property most suitably determined using the falling head method.

Voids ratio ($e$)

The ratio of the volume of voids to the volume of solids in a soil mass.

Porosity ($n$)

The ratio of the volume of voids to the total volume of a soil mass or soil sample.

Rankine's theory

A theory of earth pressure that assumes the back of the retaining wall is vertical and smooth.

Optimum water content

The moisture content at which maximum dry density is achieved; it decreases as compaction energy increases.

Sensitivity

The ratio of the compressive strength of unconfined undisturbed soil to that of remoulded soil.

Plasticity index ($PI$)

The numerical difference between the liquid limit and the plastic limit; soil is of medium plasticity if $7 < PI < 17$.

Active earth pressure

The lateral pressure exerted by the soil when a retaining wall moves away from the backfill.

Passive earth pressure

The lateral pressure exerted by the soil when a retaining wall moves towards the soil.

Coefficient of consolidation ($C_v$)

A soil property that is affected by both compressibility and permeability; for clays, it normally decreases as the liquid limit increases.

Well graded soil

A soil that has a coefficient of curvature between $1.0$ and $3.0$ and contains particles of all sizes.

Specific gravity of soil

The ratio of the weight of a given volume of soil solids to the weight of an equal volume of distilled water.

Quick condition

A phenomenon occurring when seepage pressure equals the submerged weight of soil, reducing effective pressure to zero; also called boiling condition or quick sand.

Coefficient of compressibility ($a_v$)

The ratio of the change in void ratio to the change in effective stress ($strain/stress$).

Westergaard analysis

An analysis method used specifically for calculating stresses in stratified soils.

Negative skin friction

A downward force on piles caused by the relative settlement of soft clay soils, which decreases pile capacity.