Fluid Mechanics

Intensive properties

those that are independent of the mass of the system, such as temperature, pressure, and density

Extensive properties

those whose values depend on the size- or extent- of the system. Total mass, total volume V, and total momentum are some examples

Density

mass per unit volume

Specific volume

volume per unit mass

Specific gravity

the ratio of the density of a substance to the density of some standard substance at a specified temperatures

Specific weight (weight density)

the weight of unit volume of a substance

Viscosity

a property that represents the internal resistance of a fluid to motion or the “fluidity”

Drag force

the resistance a fluid imposes on a body as it flows in the same direction, with its magnitude influenced by viscosity

Newtonian fluids

fluids for which the rate of deformation is linearly proportional to the shear stress. Examples are water, air, gasoline, and oils

Non-Newtonian fluids

the relationship between shear stress and rate of deformation is NOT linear. Examples are blood and liquid plastics

Mechanics

the study and analysis of matter through the macroscopic conservation laws of physics (mass, momentum, energy, second law)

Statics

the mechanical study and analysis of material that is fully at rest in a specific frame of reference

Dynamics

the application of Newton’s second law of motion to moving matter. Forces or accelerations through Newton’s law force balances

Fluid mechanics

the study and analysis of fluids through the macroscopic conservation of physics, conservation of mass, momentum (Newton’s 2nd law), and energy (1st law of thermodynamics), and the 2nd law of thermodynamics

Hydrodynamics

the study of the motion of fluids that can be approximated as incompressible (such as liquids, especially water, and gases at low speeds)H

Hydraulics

the hydrodynamics of liquid and vapor flow in pipes, ducts, and open channels. Exampels include water piping systems and ventilation systems

Gas dynamics

deals with the flow of fluids that undergo significant density changes, such as the flow of gases through nozzles at high speeds

Aerodynamics

The application of fluid dynamics to air, land, and water-going vehicles. Often the term is specifically applied to the flow surro9unding, and forces and moments on, flight vehicles in air

Fluid

a substance in the liquid or gas phase. Deforms continuously under the influence of a shear stress, no matter how small. When a constant shear force is applied, it never stops deforming and approaches a constant rate of strain. Stress to proportional to strain rate

Solid

a material that when sheared either deforms to a fixed static position (after which deformation stops) or fractures. Stress is proportional to strain

Angle of deformation

𝛼 (also called shear strain or angular displacement)

Stress

a component of force distributed over an area, determined by dividing the force by the area upon which it acts

Normal stress

the normal component of a force acting on a surface per unit area

Shear stress

the tangential component of a force acting on a surface per unit area

No-slip condition

the requirement that at the interface between a fluid and a solid surface, the fluid velocity and surface velocity are equal. A fluid in motion comes to a complete stop at the surface and assumes a zero-velocity relative to the surface

Velocity profile

a consequence of the no-slip condition is that all velocity profiles must have zero values with respect tot he surface at the points of contact between a fluid and a solid surface

Boundary layer

the flow region adjacent to the wall in which the viscous effects (and thus the velocity gradients) are significant

Drag

the force a fluid exerts on a surface in the flow direction

Flow separation

a phenomenon where a boundary layer adjacent to a surface is forced to leave, or “separate” from, the surface due to adverse pressure forces in the flow direction. Occurs in regions of high surface curvature, for example, at the rear of an automobile and other bluff bodies