Tips & Tricks

Here you will find articles on how to solve specific issues related to ESI's software solutions. Missing ESI products will be added progressively. Each article has a short abstract which is accessible to everyone. As logged users you can see the full article with all attached screenshots, and you can post comments related to each article

Negative Pin into a BEM fluid

Negative Pin into a BEM fluid
I see negative Pin into a BEM fluid - what may be the reason?,This was a known issue for cases with heavy fluids read more
Vibro-Acoustics
7
0

MUMPS error when solving my SEA model

MUMPS error when solving my SEA model
I'm getting a MUMPS error when solving my SEA model - what may be the cause?, Reason for this is un-allowed or un-physical combination of physical properties in some NCTs. Correct those and the solve should go through. read more
Vibro-Acoustics
11
0

Why PEM disappears when solving for coupled modes ?

Why PEM disappears when solving for coupled modes ?
PEM subsystems are nodal, whereas acoustic and structural ss are modal. The PEM ss adds to the global dynamic stiffness matrix, just as any SEA etc objects; so the PEM ss is taken into account when solving for the coupled mode. But one won't be able to visualize... read more
Vibro-Acoustics
7
0

What is <Sqq> ?

What is &lt;Sqq&gt; ?
<Sqq> is an exact expression for the ensemble average response of a system of coupled subsystems with uncertain boundaries... read more
Vibro-Acoustics
20
0

Difference between using a cavity constraint vs. a Diffuse Acoustic Field source

Difference between using a cavity constraint vs. a Diffuse Acoustic Field source
If I apply a Diffuse Acoustic Field (DAF) source on a panel instead of constraining the pressure in an adjacent cavity, will I obtain the same results?, The results from the DAF and the constrained cavity are almost identical. The two main differences between the... read more
Vibro-Acoustics
37
0

What is a stiffness multiplier in SEA?

What is a stiffness multiplier in SEA?
Essentially it’s about adjusting the Young’s modulus to fit modes in band. read more
Vibro-Acoustics
23
0

Imported modal damping from NASTRAN

 Imported modal damping from NASTRAN
How do I use imported modal damping from NASTRAN?, VA One can read the modal damping matrix from Nastran (KHH or BHH matrix). The KHH or BHH matrix needs to be in the.op2 file with the modes read more
Vibro-Acoustics
25
0

I have a DAF and a cavity wetting the same plate, and get unexpected cavity mass law - why?

I have a DAF and a cavity wetting the same plate, and get unexpected cavity mass law - why?
A model like this is not valid, i.e. a DAF is not intended to be combined with a cavity like this ... read more
Vibro-Acoustics
20
0

How do I work with only imported geometry for creating temporary nodes for subsystem creation?

How do I work with only imported geometry for creating temporary nodes for subsystem creation?
In order to import the geometry, and use this for creating new temporary nodes, select to import “Geometry (nodes and elements)”. Then in the visibility tree, uncheck “Imported nodes” under Imported “CAD/FE Geometry”, and make “Nodes on Visible Objects” checked. read more
Vibro-Acoustics
10
0

Difference in BEM solve times when recovering Radiation Efficiency. Is this expected?

Difference in BEM solve times when recovering Radiation Efficiency. Is this expected?
I see a drastic difference in BEM solve times when recovering Rad Eff. Is this expected?, Yes, computing the BEM radiation efficiency is very expensive as it has to recover the velocity at every wetted node and multiply by the mode shape at that mode, then sum that all... read more
Vibro-Acoustics
11
0

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