NACS 2.5 is available

We are happy to announce the availability of NACS 2.5.

NACS 2.5 is a feature release that mainly enhances the functionality of NACS and partly removes some bugs.

Bugs were mainly removed from the graphical user interface but also from the NACS core itself.
The bugfixes in NACS concern simulations using nonconforming mesh interfaces as well as some mechanical results as listed below.

A completely new boundary condition dialog was implemented and an improvement was introduced in the postprocessor.

Feature Highlights

NACS Core Features

New Modal Analysis Solver
A new solver for modal analyses was added that is capable of finding all modes in a given frequency range. This can be beneficial for high frequency applications where a large frequency shift might be problematic. However, this approach must be used with caution as computing all modes in a frequency range can be significantly slower than computing a fixed number of modes.
Modal Analysis: Participation Factors and Modal Masses
Modal analyses of mechanic and piezoelectric models now automatically calculate the participation factors and modal masses of the computed modes. The participation factors and modal masses are written into the result file for the load cases of translation in x-, y- and z-direction and rotation about the x-, y- and z-axis. In the simulation log these results are reported for unit load (simultaneous force in all three axes).
Use External Data in Boundary Conditions

In addition to analytic math expressions, NACS can now also use data from other simulations to define boundary conditions. This can be used e.g. for vibro-acoustic simulations with weak coupling to spilt the computation into a mechanic simulation and a subsequent acoustic simulation based on the displacements of the previous mechanic simulation. Currently, this capability is limited to data on identical grids. Interpolation of data on different grids will be added in a future version.

The following boundary conditions support this feature:

  • Mechanical Pressure (Source: acoustic Pressure)
  • Mechanical Force Density (Source: Lorentz-Forcedensity)
  • Acoustic (Normal)velocity (Source: mechanical velocity)
Boundary Condition: Permanent Magnet
A boundary condition for permanent magnets with a given remanent flux density was added. This boundary condition is similar to the flux density boundary condition, except that the magnetic field intensity inside the permanent magnet is computed according to its linear B-H curve in the second quadrant.
In previous versions of NACS the inductance of a coil was calculated as the quotient of the coil’s linked flux and its electric current, which is the static inductance. In transient simulations NACS now computes the dynamic inductance, which is defined as the derivative of the coil’s linked flux by its electric current. This provides more reasonable results in transient simulations that include permanent magnets or nonlinear materials.

NACS Core Bugfixes

Some bugs reported by customers or identified by our own staff could be fixed. Please review the main bugfixes listed below:

Crash of harmonic analysis in case of parallel usage of Biot-Savart-coils and flux parallel boundary condition
NACS crashed while solving a harmonic magnetic simulation that used both a Biot-Savart coil and a flux-parallel boundary condition simultaneously.
Load Result with the Piles Model
Whenever the Piles model was used as a material nonlinearity, the result mechRhsLoad did not contain the sum of loads as expected, but was always zero.
Weight vs. Mass

The mechanic result of mass was erroneously called weight.

NACS GUI will automatically rename the weight result to the mass result. Users that edit their simulation script manually can still use the weight result, but it is now considered deprecated and will be removed in a future version of NACS.

Non-Conforming Mesh Interfaces

A non-conforming mesh interface that was defined by two groups that did not fully overlap would sometimes provide incorrect results.

NACS crashed in the second step of a two-step analysis (static-transient or static-harmonic) if non-conforming mesh interfaces were used.

Crash if halted simulation is continued and boundary condition uses sample1D function

In case that a simulation contained a boundary condition which used the function sample1D used imported multicolumn external data, the simulation crashed since the content of the external data file was written twice to the resultfile.

NACS GUI Features

NACS 2.5 benefits from some GUI enhancements which will be described in the following sections.

External File Support

NACS 2.5 allows to define and manage external files used e.g. for defining boundary conditions.

The content of the NACS result files can be reviewed.

New boundary condition dialog

NACS 2.5 arrives with a complete reimplemented boundary condition define dialog. The new dialog allows to modify the size of the boundary condition list and remembers changes carried out by the user.

Furthermore we added support for defining boundary conditions using previous analysis steps or external result files.

Clipping in Result Viewer

In the result viewer the clipping plane created a hollow model with a hole across the clipping plane instead of displaying the results on the plane itself.

Since this volume cutting method consumes some time we currently do not see an immediate update of the cutted model. Instead a Apply button allows to set changes to the cut plane.


The current NACS Version be downloaded from our website by all registered users.

Release Notes on Youtube

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