Dissipation

Dissipation is the result of irreversible processes that take place in inhomogeneous thermodynamic systems. A thermodynamic dissipative process is one in which energy, internal, bulk flow kinetic, or system potential, is transduced from some initial form to some final form, the capacity to do mechanical work of the final form being less that that of the initial form. For example, transfer of energy as heat is dissipative because it is a transfer of internal energy from a body at one temperature to a body at a lower temperature. The second law of thermodynamics implies that this reduces the capacity of that internal energy to do mechanical work.

Thermodynamic dissipative processes are essentially irreversible. They produce entropy at a finite rate. In a process in which the temperature is locally continuously defined, the local density of rate of entropy production times local temperature gives the local density of dissipated power. Important examples of irreversible processes are: heat flow through a thermal resistance, fluid flow through a flow resistance, diffusion (mixing), chemical reactions, and electrical current flow through an electrical resistance (Joule heating). The concept of dissipation was introduced in the field of thermodynamics by William Thomson (Lord Kelvin) in 1852.

A particular occasion of occurrence of a dissipative process cannot be described by a single individual Hamiltonian formalism. A dissipative process requires a collection of admissible individual Hamiltonian descriptions, exactly which one describes the actual particular occurrence of the process of interest being unknown. This includes friction, and all similar forces that result in decoherency of energy—that is, conversion of coherent or directed energy flow into an indirected or more isotropic distribution of energy.

Waves or oscillations, lose energy over time, typically from friction or turbulence. In many cases the "lost" energy raises the temperature of the system. For example, a wave that loses amplitude is said to dissipate. The precise nature of the effects depends on the nature of the wave: an atmospheric wave, for instance, may dissipate close to the surface due to friction with the land mass, and at higher levels due to radiative cooling.

In computational physics, numerical dissipation (also known as "numerical diffusion") refers to certain side-effects that may occur as a result of a numerical solution to a differential equation. When the pure advection equation, which is free of dissipation, is solved by a numerical approximation method, the energy of the initial wave may be reduced in a way analogous to a diffusional process. Such a method is said to contain 'dissipation'. In some cases, "artificial dissipation" is intentionally added to improve the numerical stability characteristics of the solution.

A formal, mathematical definition of dissipation, as commonly used in the mathematical study of measure-preserving dynamical systems, is given in the article wandering set.

Other articles related to "dissipation":

Squally - Severe Weather - Squall Line Life Cycle - Dissipation
... From here, a general thinning of a squall line will occur with winds decaying over time, outflow boundaries weakening updrafts substantially and clouds losing their thickness. ...
Clausius–Duhem Inequality - Dissipation
... The quantity is called the dissipation which is defined as the rate of internal entropy production per unit volume times the absolute temperature ... Hence the Clausius–Duhem inequality is also called the dissipation inequality ... In a real material, the dissipation is always greater than zero ...
Dissipation - In Water Engineering
... Dissipation is the process of converting mechanical energy of downward-flowing water into thermal and acoustical energy ...
High Water - Physics - Dissipation
... also Tidal acceleration Earth's tidal oscillations introduce dissipation at an average rate of about 3.75 terawatt ... About 98% of this dissipation is by marine tidal movement ... Dissipation arises as basin-scale tidal flows drive smaller-scale flows which experience turbulent dissipation ...
Personal Internet Communicator - Technology - Hardware - Electrical Specs
... Input Voltage 12 VDC (Factory provided AC/DC converter) Power Dissipation 8 Watts (plus power supply's own dissipation) Total power Dissipation 12.7 Watts @ 100% CPU Load ...

Famous quotes containing the word dissipation:

Crowds without company, and dissipation without pleasure.
Edward Gibbon (1737–1794)

They had both noticed that a life of dissipation sometimes gave to a face the look of gaunt suffering spirituality that a life of asceticism was supposed to give and quite often did not.
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Life is hard, we say. An oyster’s life is worse. She lives motionless, soundless, her own cold ugly shape her only dissipation ...
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