耗散

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In thermodynamics, dissipation is the result of an irreversible process that takes place in homogeneous thermodynamic systems. A dissipative process is a process in which energy (internal, bulk flow kinetic, or system potential) is transformed from some initial form to some final form; the capacity of the final form to do mechanical work is less than that of the initial form. For example, heat transfer is dissipative because it is a transfer of internal energy from a hotter body to a colder one. Following the second law of thermodynamics, the entropy varies with temperature (reduces the capacity of the combination of the two bodies to do mechanical work), but never decreases in an isolated system.

In thermodynamics, dissipation is the result of an irreversible process that takes place in homogeneous thermodynamic systems. A dissipative process is a process in which energy (internal, bulk flow kinetic, or system potential) is transformed from some initial form to some final form; the capacity of the final form to do mechanical work is less than that of the initial form. For example, heat transfer is dissipative because it is a transfer of internal energy from a hotter body to a colder one. Following the second law of thermodynamics, the entropy varies with temperature (reduces the capacity of the combination of the two bodies to do mechanical work), but never decreases in an isolated system.

在热力学中，耗散是在均匀热力学系统中发生的不可逆性的结果。耗散过程是能量(内部、体流动动力学或系统势)从某种初始形式转化为某种最终形式的过程，最终形式做机械功的能力小于初始形式。例如，热传递是耗散的，因为它是内部能量从一个较热的物体向一个较冷的物体的转移。在热力学第二定律之后，熵随温度变化(降低了两个物体组合做机械功的能力) ，但是在一个孤立的系统中熵不会减少。

These processes produce entropy (see entropy production) at a certain rate. The entropy production rate times ambient temperature gives the 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).

这些过程以一定的速率产生熵(见产生熵)。产生熵速率乘以环境温度就得到了耗散功率。不可逆过程的重要例子有: 热流过热阻，流体流过流阻，扩散(混合) ，化学反应，电流流过电阻(焦耳加热)。

Definition

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.[Definition needed!]

热力学耗散过程本质上是不可逆的。它们以有限的速率产生熵。在一个局部连续定义温度的过程中，产生熵的局部密度乘以局部温度得到局部耗散功率密度。[需要定义! ]

A particular 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.

耗散过程的特殊现象不能用单个的哈密顿形式来描述。耗散过程需要一系列可接受的个体哈密顿描述，准确地描述未知的兴趣过程的实际特殊发生。这包括摩擦力，以及所有导致能量退相干的类似作用力---- 也就是说，相干或定向能量流转化为间接或更为各向同性的能量分布。

Energy

"The conversion of mechanical energy into heat is called energy dissipation." – François Roddier^[1] The term is also applied to the loss of energy due to generation of unwanted heat in electric and electronic circuits.

"The conversion of mechanical energy into heat is called energy dissipation." – François Roddier The term is also applied to the loss of energy due to generation of unwanted heat in electric and electronic circuits.

机械能转化为热量的过程叫做能量耗散这一术语也用于指电子电路中由于产生不需要的热量而造成的能量损失

Computational physics

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.^[2]

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.

在计算物理学，数值耗散(也称为“数值扩散”)是指某些副作用，可能发生的结果，数值解的微分方程。用数值近似方法求解无耗散的纯对流方程时，初始波的能量可以以类似于扩散运动的方式降低。这种方法被称为包含耗散。在某些情况下，有意添加“人为放散”以改善解决方案的数值稳定性特性。

Mathematics

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.

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.

本文给出了在保测度动力系统的数学研究中常用的耗散的形式化数学定义。

Examples

In hydraulic engineering

Dissipation is the process of converting mechanical energy of downward-flowing water into thermal and acoustical energy. Various devices are designed in stream beds to reduce the kinetic energy of flowing waters to reduce their erosive potential on banks and river bottoms. Very often, these devices look like small waterfalls or cascades, where water flows vertically or over riprap to lose some of its kinetic energy.

耗散是将向下流动的水的机械能转化为热能和声能的过程。在河床上设计了各种装置，以降低流动水的动能，减少它们对河岸和河底的侵蚀潜力。很多时候，这些装置看起来像小瀑布或瀑布，水流垂直流动或越过抛石，失去一些动能。

Irreversible processes

Important examples of irreversible processes are:

不可逆过程的重要例子有:

Heat flow through a thermal resistance

Heat flow through a thermal resistance

热流过热阻

Fluid flow through a flow resistance

Fluid flow through a flow resistance

流体流过流动阻力

Diffusion (mixing)

Diffusion (mixing)

扩散(混合)

Chemical reactions^[3]^[4]

Chemical reactions

化学反应

Electrical current flow through an electrical resistance (Joule heating).

Electrical current flow through an electrical resistance (Joule heating).

电流通过电阻(焦耳加热)。

Waves or oscillations

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.

波浪或振荡，随着时间的推移会失去能量，通常是由于摩擦或紊流。在许多情况下，“损失”的能量提高了系统的温度。例如，失去振幅的波叫做消散波。影响的确切性质取决于波的性质: 例如，大气波可能由于与陆地质量的摩擦而接近地表消散，由于辐射冷却的缘故而在更高的水平上消散。

History

The concept of dissipation was introduced in the field of thermodynamics by William Thomson (Lord Kelvin) in 1852.^[5] Lord Kelvin deduced that a subset of the above-mentioned irreversible dissipative processes will occur unless a process is governed by a "perfect thermodynamic engine". The processes that Lord Kelvin identified were friction, diffusion, conduction of heat and the absorption of light.

The concept of dissipation was introduced in the field of thermodynamics by William Thomson (Lord Kelvin) in 1852. Lord Kelvin deduced that a subset of the above-mentioned irreversible dissipative processes will occur unless a process is governed by a "perfect thermodynamic engine". The processes that Lord Kelvin identified were friction, diffusion, conduction of heat and the absorption of light.

耗散的概念是由威廉 · 汤姆森(开尔文勋爵)于1852年在热力学领域提出的。开尔文勋爵推断，上述不可逆耗散过程的一个子集将会发生，除非一个过程被一个“完美的热力学发动机”所支配。开尔文勋爵确定的过程是摩擦、扩散、热传导和光的吸收。

References

↑ Roddier F., Thermodynamique de l'évolution (The Thermodynamics of Evolution), parole éditions, 2012
↑ Thomas, J.W. Numerical Partial Differential Equation: Finite Difference Methods. Springer-Verlag. New York. (1995)

↑ Glansdorff, P., Prigogine, I. (1971). Thermodynamic Theory of Structure, Stability, and Fluctuations, Wiley-Interscience, London, 1971,

, p. 61.

↑ Eu, B.C. (1998). Nonequilibrium Thermodynamics: Ensemble Method, Kluwer Academic Publications, Dordrecht,

, p. 49,

↑ W. Thomson On the universal tendency in nature to the dissipation of mechanical energy Philosophical Magazine, Ser. 4, p. 304 (1852).

模板:Footer energy

Category:Thermodynamic processes

类别: 热力学过程

Category:Non-equilibrium thermodynamics

类别: 非平衡态热力学

Category:Dynamical systems

类别: 动力系统

This page was moved from wikipedia:en:Dissipation. Its edit history can be viewed at 耗散/edithistory

[1] Roddier F., Thermodynamique de l'évolution (The Thermodynamics of Evolution), parole éditions, 2012

[2] Thomas, J.W. Numerical Partial Differential Equation: Finite Difference Methods. Springer-Verlag. New York. (1995)

[3] Glansdorff, P., Prigogine, I. (1971). Thermodynamic Theory of Structure, Stability, and Fluctuations, Wiley-Interscience, London, 1971,
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[4] Eu, B.C. (1998). Nonequilibrium Thermodynamics: Ensemble Method, Kluwer Academic Publications, Dordrecht,
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[5] W. Thomson On the universal tendency in nature to the dissipation of mechanical energy Philosophical Magazine, Ser. 4, p. 304 (1852).

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耗散

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