Cauchy number

Cauchy number

The Cauchy number, mathrm{Ca} is a dimensionless number in fluid dynamics used in the study of compressible flows. It is named after the French mathematician Augustin Louis Cauchy.When the compressibility is important the elastic forces must be considered along with inertial forces for dynamic similarity. Thus, the Cauchy Number is defined as the ratio between inertial and the compressibility force (elastic force) in a flow and can be expressed as

: mathrm{Ca} = frac{ ho v^2}{K},

where

: ho = density of fluid, (SI units : kg/m3): v = local fluid velocity, (SI units : m/s) : K = bulk modulus of elasticity, (SI units : Pa)

Relation between Cauchy number and Mach number

For isentropic processes, the Cauchy number may be expressed in terms of Mach number. The isentropic bulk modulus K_s = gamma p, where gamma is the specific heat capacity ratio and p is the fluid pressure.If the fluid obeys the ideal gas law, we have

: K_s = gamma p = gamma ho R T = , ho a^2,

where

: a = sqrt{gamma RT} = speed of sound, (SI units : m/s) : R = characteristic gas constant, (SI units : J/(kg K) ): T = temperature, (SI units : K)

Substituting K (K_s) in the equation for mathrm{Ca} yields

: mathrm{Ca} = frac{v^2}{a^2} = M^2.

Thus, the Cauchy number is square of the Mach number for isentropic flow of a perfect gas.

ee also

References


* B. S. Massey and J. Ward-Smith, "Mechanics of Fluids", 7th ed., Nelson Thornes, UK (1998).

Wikimedia Foundation. 2010.

Игры ⚽ Нужен реферат?

Look at other dictionaries:

  • Cauchy's theorem (group theory) — Cauchy s theorem is a theorem in the mathematics of group theory, named after Augustin Louis Cauchy. It states that if G is a finite group and p is a prime number dividing the order of G (the number of elements in G ), then G contains an element… …   Wikipedia

  • Cauchy's functional equation — is one of the simplest functional equations to represent, however its solution over the real numbers is extremely complicated. The equation is : f(x+y)=f(x)+f(y). Over the rational numbers, it can be shown using elementary algebra that there is a …   Wikipedia

  • Cauchy sequence — In mathematics, a Cauchy sequence, named after Augustin Cauchy, is a sequence whose elements become arbitrarily close to each other as the sequence progresses. To be more precise, by dropping enough (but still only a finite number of) terms from… …   Wikipedia

  • Cauchy-Riemann equations — In mathematics, the Cauchy Riemann differential equations in complex analysis, named after Augustin Cauchy and Bernhard Riemann, are two partial differential equations which provide a necessary and sufficient condition for a differentiable… …   Wikipedia

  • Cauchy, Augustin-Louis, Baron — born Aug. 21, 1789, Paris, France died May 23, 1857, Sceaux French mathematician, pioneer of analysis and group theory. After a career as a military engineer in Napoleon s navy, he wrote a treatise in 1813 that became the basis of the theory of… …   Universalium

  • Cauchy-continuous function — In mathematics, a Cauchy continuous, or Cauchy regular, function is a special kind of continuous function between metric spaces (or more general spaces). Cauchy continuous functions have the useful property that they can always be (uniquely)… …   Wikipedia

  • Cauchy principal value — In mathematics, the Cauchy principal value of certain improper integrals, named after Augustin Louis Cauchy, is defined as either* the finite number::lim {varepsilon ightarrow 0+} left [int a^{b varepsilon} f(x),dx+int {b+varepsilon}^c f(x),dx… …   Wikipedia

  • Cauchy index — In mathematical analysis, the Cauchy index is an integer associated to a real rational function over an interval. By the Routh Hurwitz theorem, we have the following interpretation: the Cauchy index of : r ( x )= p ( x )/ q ( x ) over the real… …   Wikipedia

  • Cauchy distribution — Not to be confused with Lorenz curve. Cauchy–Lorentz Probability density function The purple curve is the standard Cauchy distribution Cumulative distribution function …   Wikipedia

  • Cauchy space — In general topology and analysis, a Cauchy space is a generalization of metric spaces and uniform spaces for which the notion of Cauchy convergence still makes sense. Cauchy spaces were introduced by H. H. Keller in 1968, as an axiomatic tool… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”