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Suggestion for new description in documentation of waveTransmissive BC

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Old   August 23, 2022, 10:03
Default Suggestion for new description in documentation of waveTransmissive BC
Julio Pieri
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Hi all,

I have a suggestion to make.

In the waveTransmission BC documentation, "gamma" is defined as "ratio of specific heats". However, this leads to a lot of confusion (as I seen around) when we are dealing with liquids.

I believe the correct description would be something like "numerator of the wave speed formula", which ends up being 1 for water.

From the .C file:
    // Calculate the speed of the field wave w
    // by summing the component of the velocity normal to the boundary
    // and the speed of sound (sqrt(gamma_/psi)).
For liquid, the OF's \psi is 1/(B/rho), where B is the bulk modulus of the liquid. This is the reciprocal of (the square of) the wave speed! So that formula ends up taking gamma as 1 (at least for weak compressible water).

A simple change that can help some users in the future!
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