Fluid Dynamics

Flashcards on Fluid Dynamics

Fluid

A substance that offers no permanent resistance to deforming forces.

Fluid Statics

Concentrates on fluids at rest; includes atmospheric pressure, liquid pressure, Archimedes' principle, and Pascal's law.

Fluid Dynamics

Concerns the fluid in motion; important applications include river flow, water distribution systems, gas pipelines, aviation, and motion underneath the surface of water.

Hydrodynamics

The study of the flow of liquid.

Hydrostatics

The study of liquid at rest.

Laminar Flow

Fluid particles moving steadily in smooth paths in layers, with each layer moving smoothly past adjacent layers with no mixing. Streamlines do not cross each other.

Turbulent Flow

The flow or path of the fluid particles are irregular, their direction is always changing or whirling. The speed of the fluid at a point is continuously undergoing changes in both magnitude and direction.

Equation of Continuity

A₁v₁ = A₂v₂; Describes the relationship between area and speed of fluid flow. The larger the area, the slower the speed; the smaller the area, the faster the speed.

Bernoulli's Equation

Relates the pressure, flow speed, and height for the steady (laminar) flow of an ideal incompressible fluid.

Magnus Effect

A particular manifestation of Bernoulli's theorem associated with a spinning object moving through a fluid, causing a difference in pressure on opposite sides of the spinning object and producing deflection.

Viscosity

The resistance to fluid motion (or internal resistance of fluid). It arises when there is relative motion between layers of the fluid.

Dynamic Viscosity

Measure fluid's resistance to flow when an external force is applied.

Kinematic Viscosity

Measure the resistive flow of a fluid under the weight of gravity; more useful than dynamic viscosity.

Newton's Law of Viscosity

States that the shear stress between two adjacent layers of fluid is directly proportional to the negative value of the velocity gradient between the same two adjacent fluid layers.

Stokes' Law

Expresses the drag force resisting the fall of small spherical objects through a fluid medium under the influence of gravity: F = 6πηrv

Surface Tension

The tendency of the surface of a liquid to behave like a stretched elastic skin (or membrane). It is due to the attractive forces between liquid molecules called cohesion.

Cohesion

Forces between molecules of the same substance.