Edges and Points

•Line Heat Source (edges)

•Pressure Point Constraint

•Point Heat Source

Pairs

•Heat Continuity

•Pair Thin Thermally Resistive Layer

•Temperature

•Boundary Heat Source

•Flow Continuity

•Wall

These features are slightly different than for other interfaces and are described in this section:

•Initial Values

•Fluid

•Inlet

•Outlet

Fluid

The Fluid feature adds the momentum equations and the temperature equation corresponding to an ideal gas but without volume forces and heat sources. Volume forces and heat sources can be added as separate features. Viscous heating and pressure work terms are added by default to the temperature equation.

When the turbulence model type is set to RANS, the Fluid node also adds the equations for k and , or the undamped turbulent kinematic viscosity, depending on which turbulence model that is used.

The thermal conductivity describes the relationship between the heat flux vector q and the temperature gradient T as in q = k T, which is Fourier’s law of heat conduction. Enter this quantity as power per length and temperature.

D O M A I N S E L E C T I O N

By default, All domains are selected.

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M O D E L I N P U T S

Define the model inputs. If no model inputs are required, this section is empty.

To define the Absolute Pressure, see the settings for the Heat Transfer in

Fluids node as described in the COMSOL Multiphysics User’s Guide.

Tip

Select a Thermal conductivity k (SI unit: W/(m·K)) from the list—From material,

Sutherlands Law (the default), or User defined. If User defined is selected, choose

Isotropic, Diagonal, Symmetric, or Anisotropic based on the characteristics of the thermal conductivity and enter another value or expression in the field or matrix.

Sutherland’s Law

If Sutherlands Law is selected, enter the following model parameters:

•Conductivity at reference temperature kref (SI unit: W/(m·K)))

•Reference temperature Tk,ref (SI unit: K)

•Sutherland constant Sk (SI unit: K)

Sutherland’s law describes the relationship between the thermal conductivity and the total temperature of an ideal fluid according to

T H E R M O D Y N A M I C S

The High Mach Number Flow assumes the fluid to be governed by the ideal gas law. Specify the thermodynamics properties by selecting a gas constant type and selecting between entering the heat capacity at constant pressure or the ratio of specific heats. For an ideal gas the density is defined as

M p p

= ------n-------A-- = ------A---- ,

RT RsT

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where pA is the absolute pressure, and T the temperature.

•Select a Gas constant type— Specific gas constant Rs (SI unit: J/(kg·K)) or Mean molar mass Mn (SI unit: kg/mol). The default setting is to use the property value

From material. Select User defined to enter another value or expression for either of material property. In both cases, the default uses data From material. Select User

defined to enter other values or expressions. If Mean molar mass is selected, the universal gas constant R 8.314 J/(mol·K), which is a built-in physical constant, is

also used.

•From the Specify Cp or list, select Heat capacity at constant pressure Cp

(SI unit: J/(kg·K)), or Ratio of specific heats (unitless). The default setting is to use the property value From material. Select User defined to enter another value or expression for either of material property.

D Y N A M I C V I S C O S I T Y

The dynamic viscosity describes the relationship between the shear rate and the shear stresses in a fluid.

Select a Dynamic viscosity (SI unit: Pa·s) from the list—From material,

Sutherlands Law (the default), or User defined.

Sutherland’s Law

If Sutherlands Law is selected, enter the following model parameters:

•Dynamic viscosity at reference temperature ref (SI unit: Pa·s)

•Reference temperature T ,ref (SI unit: K)

•Sutherland constant S (SI unit: K)

Sutherland’s law describes the relationship between the dynamic viscosity and the total temperature of an ideal fluid according to

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