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March 28, 2019, 09:58 |
Material Properties by expressions
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#1 |
New Member
Join Date: Mar 2019
Posts: 1
Rep Power: 0 |
Hey folks,
i want to simulate the flow of liquid oxygen. In a preliminary simulation i used a constant property liquid and everything worked fine. Now i want to account for changes in fluid properties. I defined expressions for the density, heat capacity, dynamic viscosity and the thermal conductivity as functions of p and T (pressure and Temperature). I checked the units and the values and they are correct. If i don't setup a table CFX-Pre starts complaining. I tried to start a simulation with and without a table but either way the solver stops immediately. Is there a major mistake in my setup? Do i need a table? I heard about problems when defining density and the heat capacity at the same time but i couldn't find any related threads. Thanks in advance |
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March 28, 2019, 10:27 |
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#2 |
Senior Member
Join Date: Jun 2009
Posts: 1,869
Rep Power: 33 |
The CFX-Solver nearly always creates a table from the fundamentals properties given by expressions.
For example, how would compute Enthalpy from a Cp expression? How would you compute Entropy from expressions for density and Cp? Thermodynamic properties are not independent, they MUST satisfy the Maxwell relationships; otherwise, the energy balance equations will not work properly. See ANSYS CFX documentation for a light description of the minimum requirements. |
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Tags |
error, expressions, material, properties |
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