A description of fluid mechanics

When a shear stress is applied to the surface of the fluid, the fluid will continuously deform, i. The barometer invented in the 17th century by the Italian physicist and mathematician Evangelista Torricelliand still in use today, is a U-tube that is sealed at one end see Figure 1B.

fluid mechanics

This definition means regardless of the forces acting on a fluid, it continues to flow. As will be discussed in a later learning module, the results in either case must be scaled properly according to the rules of dimensional analysis.

Since the pressure at Q is just the atmospheric pressureit is equal to the pressure at a point immediately above the meniscus.

Fluid mechanics

A slightly less rigorous definition is that the drag of a small object being moved slowly through the fluid is proportional to the force applied to the object. A fluid at rest can have only normal stresses, since a fluid at rest cannot resist a shear stress.

If the rate of flow is very small, drops will form the nonspherical shapes suggested by Figure 4D before they detach themselves and fall. The static conditions are independent of the frame of reference.

The last three terms make up the convective acceleration, which is defined as the acceleration due to convection or movement of the fluid particle to a different part of the flow field.

Definition of 'fluid mechanics'

The torque also vanishes in 2A, and the prism can in principle remain indefinitely in that orientation as well; the equilibrium in this case, however, is unstable, and the slightest disturbance will cause the prism to topple one way or the other.

A pathline is an integrated pattern. In liquids the molecules are more or less in contact, and the short-range attractive forces between them make them cohere; the molecules are moving too fast to settle down into the ordered arrays that are characteristic of solids, but not so fast that they can fly apart.

Navier—Stokes equations Main article: Flow in which turbulence is not exhibited is called laminar. One can say that the solid at rest is able to resist the shear stress.

To obtain force, one must multiply each stress by the surface area on which it acts, since stress is defined as force per unit area. Some knowledge of the basic properties of fluids will be needed; a survey of the most relevant properties is given in the next section.

Pressure, velocity, acceleration, and all other flow properties are described as fields within the control volume. For instance, laminar flow over a sphere is steady in the frame of reference that is stationary with respect to the sphere.

There are a few liquids, known as liquid crystals, in which the molecules are packed together in such a way as to make the properties of the medium locally anisotropicbut the vast majority of fluids including air and water are isotropic.

Viscosity Viscosity is the fluid property that determines the amount of resistance of the fluid to shear stress. First, if the flow is unsteady, Q changes directly with respect to time. Steady vs unsteady flow[ edit ] Hydrodynamics simulation of the Rayleigh—Taylor instability [5] A flow that is not a function of time is called steady flow.

For a good illustration of this, consider the comparison of a fluid and a solid under application of a shear stress: Either description method is valid in fluid mechanics, but the Eulerian description is usually preferred because there are simply too many particles to keep track of in a Lagrangian description.Since fluid flow is a continuum phenomenon, at least down to the molecular level, the Eulerian description is usually preferred in fluid mechanics.

Note, however, that the physical laws such as Newton's laws and the laws of conservation of mass and energy apply directly to particles in a Lagrangian description.

Fluid mechanics, science concerned with the response of fluids to forces exerted upon them. It is a branch of classical physics with applications of great importance in hydraulic and aeronautical engineering, chemical engineering, meteorology, and zoology. Definition of fluid mechanics from the Collins English Dictionary Subordination When two or more clauses are joined by a conjunction other than and, but, or, or yet, one of the clauses is the main clause; the other clauses are subordinate clauses.

There are two branches of fluid mechanics: Fluid Statics or hydrostatics is the study of fluids at rest. The main equation required for this is Newton's second law for nonaccelerating bodies, i.e. Fluid Dynamics is the study of fluids in motion.

2 A Glossary of Terms for Fluid Mechanics E. T. Leighton D. T. Leighton University of Notre Dame In order to “walk the walk”, it is useful to first be able to “talk the talk”. Fluid mechanics, science concerned with the response of fluids to forces exerted upon them. It is a branch of classical physics with applications of great importance in hydraulic and aeronautical engineering, chemical engineering, meteorology, and zoology.

The most familiar fluid is .

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A description of fluid mechanics
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