When one studies the literature carefully, one does find fundamental errors made due to the fact that simple understanding of thermodynamics is lacking. As we have already discussed very early on the state principle and the fact that any two independent intensive thermodynamic properties are sufficient to define a thermo-dynamic state, it is really of no consequence which two are selected since the final result has to be unique.
Chawla (1978) selects three different combinations of properties to determine the speed of sound. In the first case, the variables selected are the velocity, the pressure, and the enthalpy. The result for the speed of sound turns out to be
1 where p is the density, inverse of v. The second case is
for the velocity, density, and pressure.
This time the result obtained be-
. The third case is for the velocity, pressure and temper-
ature. The result obtained is c =
V dP Jt
However, from the definition of the speed of sound, c2 = I —
and using the
methodology given above, it is indeed very simple to show that the analytical re-
No matter which two properties along with the velocity are chosen, this is the result that must be obtained. Results are obtained in terms of non-measurable properties which are consequently solved numerically, Chawla (1978). Since the series variation of these properties do not have the same character, numerical truncation errors result in different forms for the answers. The author then tries to justify why they are different. However, we have seen that the result has got to be unique, the state principle, and it is demonstrated once again by Arnas (2000). All three results above are analytically the same, as it should be. Numerically, they are not! Therefore, a fundamental understanding of thermodynamics is very important to explain physical phenomena.
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