Fluid Flow Operation Glossary of Terms

1. Glossary of Terms
1) Vapor Pressure: - The pressure of a vapor in contact with its liquid or solid form.
OR
Vapor Pressure: - The pressure exerted by vapor in thermodynamically equilibrium with
its condensed phase (solid or liquid) at a given temperature in a closed system.
Unit:-Pa, Torr ,Bar, mmHg
2) Partial pressure :- The pressure that exerted by the component in the same volume and
at the same temperature.
OR
Partial Pressure:- The pressure that would be exerted by one of the gases in a mixture if
it occupied the same volume and same temperature of its own.
Unit:-Pa, N/m2
3) Mole fraction(X) :- It is the ratio of the moles of the individual component to the total
moles of the mixture.
Mole fraction of “A” (XA) = (NA ) / (NA+NB+NC)
Where, NA, NB, NC = Moles of substances
4) Weight fraction(W):-It is the ratio of weight of the individual component to the total
weight of the mixture.
Weight fraction of A (WA) = (WA) / (WA+WB+WC)
Where, WA, WB,WC =weight of substance
5) Moles:- The mass in grams of the substance that is equal numerically to its molecular
weight.

2. 6) Gram moles:- The mass in grams of the substance that is equal numerically to its
molecular weight.
Na = Wa / Ma
Where, Na = Number of moles of “a”, Wa = Weght of a in gram, Ma = Molecular weight of a
7) Force(F):- Force is proportional to the mass(m) of product and acceleration (a).
F=m*A
Unit:- N or Kg.m/S2
8) Pressure(P):- Force per unit area
P = F/A
1 atm = 760 mmHg
=101325 Pa or N/m2
= 101.325 KPa or KN/ m2
= 1.103 bar
= 760 torr
= 10.33 mH2O
= 1.033 Kgf/cm2
= 14.7 Psi
9) Atmospheric pressure:-The atmospheric air excretes a normal pressure upon all surface
with which it is in contact.
10) Absolute pressure:-It is net pressure of system measure from zero level or datum is
called absolute pressure.
11) Gauge Pressure:- It is measured either about or below atmospheric pressure as datum.
12) Vacuum pressure:- The pressure of system below atmospheric pressure value (suction
pressure)is called vacuum pressure.
13) Surface Tension (σ ) = The Property of liquid surface film to exert tension is called
surface tension.

3. OR
Surface Tension:-The Force required to maintain a unit length of film in equilibrium.
σ = F/ l where, F= Force and l = length
Unit = N/m
14) Capillary:- If a tube of very fine diameter is immersed in liquid then there may be the
rise or fall of liquid level inside the tube depending upon the wetting and non-wetting
behavior of the liquid with the tube surface, this rise or fall of liquid level is a
phenomenon known as capillary and then the tube is very small diameter is said to be
capillary tube.
15) Viscosity (μ):- The resistance offered by a fluid to its continues deformation is called
viscosity.
μ = τ / f
Unit = N.S/m2
16) Shear Stress(τ) :-Force per unit area
17) Dynamic viscosity (μ):- Shear stress (τ) to unit rate of shear deformation.
μ = τ /(du/dy) = (shear stress / unit rate)
18) Kinematic viscosity (ν) :- Ratio of the viscosity(μ) of the fluid to its density(ρ).
ν = μ / ρ = Viscosity/ Density
19) Temperature (T):- It is the degree of hotness and coldness of the substance which can
be measured by indication or thermometer.
20) Heat (Q):-A form of energy which is in transit between hot source to a cold receiver by
driving force.
1 Cal = 4.186 Joule
21) Specific volume :- Volume per unit mass
22) Molar volume:- The volume occupied by one mole of gas is called molar volume.

4. 23) Dalton’s law:- Total pressure exerted by a gaseous mixture is equal to the sum of the
partial pressure of the component gas.
P= Pa +Pb + Pc
24) Ideal gas law: - The volume of gas is directly proportional to the number of moles(n) and
it is directly proportional to the absolute temperature and it is inversely proportional to
the pressure.
PV = nRT
V=nRT/P
Where, n=Number of mole of gas, T=Temperature, P=Pressure ,R=Gas constant
25) Density(ρ) = Mass of the fluid per unit volume
Unit:-gm/m3
,Kg/cm3
26) Weight density(w) = Weight of fluid per unit volume
27) Specific gravity (ρg ) = Ratio of the density of fluid to the density of a standard fluid(like
water)
ρg = ρfluid / ρwater
28) Pressure head:-The vertical height or the free surface about any point in a liquid at rest
is called pressure head.
h= P/ρg
29) Dynamic Head:- Energy required to set fluid in motion and to overcome any resistance
to that motion.
30) Average Velocity (u) :- Ratio of volumetric mass flow rate(Q) to the cross-section
area(A) of Condit.
31) Mass velocity (G) :- Ratio of mass flow rate(m) to the cross-section area(A) of Condit.
G= m / A =Mass flow rate/Cross section area.
32) Fully develop flow:-The flow with unchanging velocity distribution is called fully
develop flow.

5. 33) Potential flow:-The flow of incompressible fluid without presence of shear is called
potential flow.
34) Laminar flow:-At low velocity, the flow of fluid in the form of parallel stream which do
not interfere with each other .it is called laminar flow.(Re<= 2100)
35) Turbulent flow:- The flow of fluid in which a fluid flows erratically in the form of cross
current and eddies is called turbulent flow (Re>= 10000)
36) Transition flow:- The flow characteristic of laminar and turbulent flow.it is called
transition flow.(2100<= Re>= 10000)
37) Drag force (FD) :- The component of the total force (FR) in the direction of motion is
called Drag.
OR
Drag force:- Force exerted by the fluid in the direction of motion.
38) Lift force(FL) :- The component of the total force (FR) in the direction perpendicular to
the direction is known as lift force.
39) Buoyant force:-The force tending to lift up the body under such condition is called
buoyancy force.
40) Buoyancy:- An immersed body to be lifted up in the fluid because of an upward force
opposite to the action of gravity is called as buoyancy.
41) Critical velocity:-The velocity at which the flow changes from laminar to turbulent is
called critical velocity.
42) Fanning friction factor (f):-It is the ratio of the wall shear stress to the product of kinetic
energy of fluid and the density.
43) Fluidization:- An operation by which fine granular solids are transformed into a fluid
like state through contact with a fluid is known as fluidization.
44) Boundary layer:- Velocity profile in the flow due to shear stress at the wall.This is
called Boundary layer.
 Drag force to shear stress at wall surface at start is zero and maximum at
fully develop flow and after some time .it is constant.