The Linearized Euler, Frequency Domain (lef) interface (
), found under the
Acoustics>Aeroacoustics branch (
) when adding a physics interface, is used to compute the acoustic variations in density, velocity, and pressure in the presence of a stationary background mean-flow that is well approximated by an ideal gas flow. The physics interface is used for aeroacoustic simulations that can be described by the linearized Euler equations.
The equations defined by the Linearized Euler, Frequency Domain interface are the linearized continuity, momentum (Euler), and energy equations. The physics interface solves for the acoustic variations in the density ρ, velocity field
u, and pressure
p. The equations are formulated in the frequency domain and assume harmonic variation of all sources and fields. The harmonic variation of all fields and sources is given by
eiωt using the
+iω convention. The background mean flow can be any stationary gas flow that is well approximated by an ideal gas. The coupling between the acoustic field and the background flow does not include any predefined flow induced noise. Even though the equations do not include any loss mechanisms, only acoustic modes exist in the frequency domain as the driving frequency is predefined and real valued.
When this physics interface is added, these default nodes are also added to the Model Builder —
Linearized Euler Model,
Rigid Wall, and
Initial Values. For axisymmetric components an
Axial Symmetry node is also added.
Then, from the Physics toolbar, add other nodes that implement, for example, boundary conditions and sources. You can also right-click
Linearized Euler, Frequency Domain to select physics features from the context menu.
The Label is the default physics interface name.
The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern
<name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the
name string must be unique. Only letters, numbers, and underscores (_) are permitted in the
Name field. The first character must be a letter.
The default Name (for the first physics interface in the model) is
lef.
See Sound Pressure Level Settings for the Pressure Acoustics, Frequency Domain interface. Only
Use reference pressure for air or
User-defined reference pressure are available selections.
See Typical Wave Speed for the Pressure Acoustics, Frequency Domain interface.
This physics interface defines these dependent variables (fields), the Density rho, Velocity field u and its components, and
Pressure p. The name can be changed but the names of fields and dependent variables must be unique within a model.
Select the Stabilization Method —
No stabilization applied,
Galerkin least squares (GLS) stabilization (the default),
Streamline upwind Petrov-Galerkin (SUPG) stabilization, or
Streamline diffusion (legacy method). When stabilization is selected enter a value for the
Stabilization constant αstab (dimensionless). The default value is
1e-5 and should typically have a numerical value between
1e-3 and
1e-7. In cases where there is no background flow, set the value to the lower limit
1e-7.