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Using the Predefined System for Moist air, Dry air, or Water-steam defined in the Thermodynamics feature available with the Liquid & Gas Properties Module. Once set up, a material can be automatically generated.
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Create your own material, for example, following the IEC standard for moist air (see Ref. 13). Set up a material and let it depend on the necessary model inputs (pressure, temperature, or relative humidity). Then, set up the necessary interpolation functions or analytical expressions and store the material under the User-Defined Library for future use.
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Moist air is generated from Thermodynamics in the Pressure Reciprocity Calibration Coupler with Detailed Moist Air Material Properties tutorial. Application Library path
Acoustics_Module/Tutorials,_Thermoviscous_Acoustics/pressure_reciprocity_calibration_coupler |
For detailed information about Materials, the Liquids and Gases Materials Library, and the Piezoelectric Materials Library see the COMSOL Multiphysics Reference Manual.
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For detailed information about the Predefined system see the Thermodynamics chapter in the Liquid & Gas Properties User’s Guide.
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The ratio of specific heats γ = 1.4
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The bulk viscosity μB is defined as μB = 0.6·μ(T) in order to comply with the absorption behavior (see discussion in The Bulk Viscosity section).
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The (isobaric) coefficient of thermal expansion is defined as αp = 1/T, following the ideal gas law.
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The parameter of nonlinearity B/A is also defined for gases following the ideal gas law as B/A = (γ+1)/2 (see Ref. 12).
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The bulk viscosity is defined as μB = 2.79·μ(T). In order to comply with the absorption behavior, (see the discussion in The Bulk Viscosity section).
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The ratio of specific heats γ = γ(Τ) is based on the thermodynamic relation
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