In
fluid dynamics
In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids— liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other gases in motion) an ...
, the
fluid
In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...
flow is often decomposed into a mean flow and
deviations from the
mean
There are several kinds of mean in mathematics, especially in statistics. Each mean serves to summarize a given group of data, often to better understand the overall value (magnitude and sign) of a given data set.
For a data set, the '' ari ...
. The
averaging
In ordinary language, an average is a single number taken as representative of a list of numbers, usually the sum of the numbers divided by how many numbers are in the list (the arithmetic mean). For example, the average of the numbers 2, 3, 4, 7, ...
can be done either in space or in time, or by
ensemble averaging
In machine learning, particularly in the creation of artificial neural networks, ensemble averaging is the process of creating multiple models and combining them to produce a desired output, as opposed to creating just one model. Frequently an ens ...
.
Example
Calculation of the mean flow may often be as simple as the
mathematical mean
In mathematics, generalized means (or power mean or Hölder mean from Otto Hölder) are a family of functions for aggregating sets of numbers. These include as special cases the Pythagorean means ( arithmetic, geometric, and harmonic means). ...
: simply add up the given flow rates and then divide the final figure by the number of initial readings.
For example, given two
discharges (''Q'') of 3 m³/s and 5 m³/s, we can use these flow rates ''Q'' to calculate the mean flow rate ''Q''
mean. Which in this case is ''Q''
mean = 4 m³/s.
See also
*
Generalized Lagrangian mean
In continuum mechanics, the generalized Lagrangian mean (GLM) is a formalism – developed by – to unambiguously split a motion into a mean part and an oscillatory part. The method gives a mixed Eulerian–Lagrangian description for the flo ...
References
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{{fluiddynamics-stub
Fluid dynamics