The study of fluid mechanics is important in numerous fields of engineering, including civil,

environmental, agricultural, irrigation, mechanical, aerospace, nuclear, chemical, petroleum,

biomedical, fire protection, and automotive engineering. The fundamental principles

of fluid mechanics include three basic units of study: fluid statics, fluid kinematics, and fluid

dynamics (Section 1.2). The physical properties/characteristics of a fluid system, along with

the fluid kinematics and fluid dynamics, will determine the type of fluid flow (Section 1.3).

The physical quantities of fluid flow (geometrics, kinematics, and dynamics) and the physical

properties/characteristics of fluids (mass density, specific gravity, specific weight, viscosity,

surface tension, vapor pressure, and bulk modulus) are expressed using four

primary dimensions (force or mass, length, time, and temperature) and a specific system

of units (metric or English) (Section 1.4). Most fluid properties vary with temperature and

pressure, while the acceleration due to gravity varies with altitude and thus atmospheric

pressure. As such, it is important to distinguish between two types of pressure scales

(Section 1.5), define the conditions of standard atmosphere (Section 1.6), and define the standard

reference for standard atmospheric pressure (Section 1.7). Furthermore, it is important

to highlight Newton’s second law of motion in the definition of the acceleration due to gravity

(Section 1.8) and to note that the dynamic forces acting on a fluid element include those

due to gravity, pressure, viscosity, elasticity, surface tension, and inertia (Section 1.9). And,

finally, the physical properties of fluids are presented in Section 1.10.

The fundamental principles of fluid mechanics can be subdivided into three units of study:

fluid statics, fluid kinematics, and fluid dynamics. Fluid statics deals with fluids at rest,

while fluid kinematics and fluid dynamics deal with fluids in motion. Fluid statics is based

upon the principles of hydrostatics, which yield the hydrostatic pressure equation. Fluid

kinematics is based upon the principle of conservation of mass, which yields the continuity

equation. And fluid dynamics is based upon the principle of conservation of momentum

(Newton’s second law of motion), which yields the equations of motion, known as the

energy equation and the momentum equation. The energy equation may alternatively be

based on the principle of conservation of energy (the first law of thermodynamics). Furthermore,

fluid dynamics also includes the topic of dimensional analysis, which yields the resistance equations.