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thermodynamic pressure Vs. mechanic pressure

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Old   July 8, 2013, 21:07
Default thermodynamic pressure Vs. mechanic pressure
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Mehdi
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what is the differences between thermodynamic pressure and mechanic pressure ?
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Old   July 9, 2013, 12:50
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Mohammad Saeedi
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Thermodynamic pressure is actually the pressure you sense with you sensor.

Mechanical pressure is the pressure that comes from the diagonal part of the stress tensor.

In fact, they are usually very close to each other. You can find the math. definition of them in the book fluid dynamics of Bachelor.
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Old   July 9, 2013, 22:18
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Dear Mohammad;
thank you so much for the reply. I know waht you mean, but I want to know the physicval meaning and differences of these properties. I read in a site that:

thermodynamic pressure:
1-Force exerted on container walls as fluid molecules coincide with it during their random movement.
2- Related to absolute temperature of the fluid and includes the vibrational and rotational energy as well.

hydrostatic pressure :
1- Average mechanical pressure exerted at a point in the fluid.
2- Related to translational energy of the molecules.

but these explanation are a little vague. I want to know a distinct definition of these properties.

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Originally Posted by saeedi View Post
Thermodynamic pressure is actually the pressure you sense with you sensor.

Mechanical pressure is the pressure that comes from the diagonal part of the stress tensor.

In fact, they are usually very close to each other. You can find the math. definition of them in the book fluid dynamics of Bachelor.
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