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WORKSHOP SCIENCE - CITS

EXERCISE 10 : Fluid Mechanics

Fluid mechanics is the study of fluid behavior (liquids, gases, and plasmas) at rest and in motion. Fluid
mechanics has a wide range of applications in mechanical and chemical engineering, in biological systems, and
in astrophysics.
(1)Fluid statics (fluid at rest), (2) Momentum and energy analyses (fluids in motion), and (3)Viscous effects and
all sections considering pressure forces (effects of fluids on boundaries).

Properties of Fluid (Density, Viscosity, Specific Weight, Specific Volume, Specific Gravity) With Their
Units:

The density of a fluid is defined as the ratio of the mass of the fluid its volume. The density of gases is dependent
on pressure and temperature, while the density of liquid remains constant. The density of water is 1000 kg. m-3
while density of air is 1.225 kg. Fluid Density is the mass per unit volume and is denoted by the Greek letter ρ
(rho). The old English system of units uses the slug for the unit of mass and feet for the unit of length.

The liquid which has the highest density is mercury, It has a density of about 13.546 grams per cubic centimeter.

Substance Density
Air (pair) pair 1.2kg/m 1.2 kg per m 3
3
Water (pwater) pwater 1000kg/m 1000 kg per m 3
3
Mercury (pHg)pHg 13600kg/m 13600 per m
3
3
Liquid has lowest density is Petrol.

• Petrol is a transparent liquid that is used primarily as a fuel in internal combustion engines.
• It consists mostly of organic compounds obtained by the fractional distillation of petroleum.
Viscosity: Viscosity is a measure of a fluid’s resistance to flow. The SI unit of viscosity is Poiseuille (PI). Its
other units are Newton-second per square meter (Ns m-2) or Pascal-second (Pa s.) The dimensional formula of
viscosity is [ML-1T-1].
A highly viscous fluid tends to be thick, like honey or cold maple syrup. Compared to a relatively non-viscous fluid,
such as water, highly viscous liquids flow much more slowly. Viscosity is represented by the symbol ղ “eta”, and
the use of the Greek letter mu (μ) is also common.

Hence, the SI unit of Viscosity is (N·s/m2).

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CITS : WCS - Mechanical - Exercise 9