3. Modeling A

3.1. Characteristics of modeling

Formulation pressure 3D elements” ACOUSTIQUE “

Divide =	15	meshes HEXA20selon the \(x\) axis
	2	meshes HEXA20selon the \(y\) axis
	2	meshes HEXA20selon the \(z\) axis

Boundary conditions:
	VITE_FACE:	(group_MA: Input	Vnor: RI 0.014 0.)
	IMPE_FACE:	(group_MA: Output	Impe: RI 445.9 0.)

Node name

\(A=\mathrm{No1}\)

\(B=\mathrm{No780}\)

\(C=\mathrm{No751}\)

\(D=\mathrm{No763}\)

3.2. Characteristics of the mesh

Number of nodes:	471
Number of meshes and types:	60 HEXA208 QUAD8

3.3. Tested values

Location	Sizes	Reference	Tolerance
\(A\)	\(p(\mathit{réel})\)	—6.2426	0.1%
	\(p(\mathit{imag})\)	0.0000	0.1%
	\(p(\mathit{dB})\)	109.9	0.1%
	Sound Intensity (real)	0.0437	3%
	Sound Intensity (image)	0	3.5E-4
\(B\)	\(p(\mathit{réel})\)	—6.2426	0.1%
	\(p(\mathit{imag})\)	0.0000	0.1%
	\(p(\mathit{dB})\)	109.9	0.1%
	Sound Intensity (real)	0.0437	3%
	Sound Intensity (image)	0	3.5E-4
\(C\)	\(p(\mathit{réel})\)	6.0237	0.1%
	\(p(\mathit{imag})\)	1.6387	0.1%
	\(p(\mathit{dB})\)	109.9	0.1%
	Sound Intensity (real)	0.04037	3%
	Sound Intensity (image)	0	3.5E-4
\(D\)	\(p(\mathit{réel})\)	6.0237	0.1%
	\(p(\mathit{imag})\)	1.6387	0.1%
	\(p(\mathit{dB})\)	109.9	0.1%
	Sound Intensity (real)	0.0437	3%
	Sound Intensity (image)	0	3.5E-4

					Frequency
Clean mode order \(i\)	\(m\)		\(n\)		\(p\)	reference	tolerance
2 3 4 5 6 7 8 9	1 »
2
3
4
5
0
1
2 »	0 0 0 0 0 0 0 0	0 0 0 0 0 1 1 1	171.5 343.0 514.5 686.0 857.5 857.5 874.482 923.556	0.01% 0.01% 0.1% 1% 0.1% 0.5% 0.5% 0.5%

3.4. note

The results are tested in two different ways:

• by the usual procedure using DYNA_VIBRA;

• by a calculation broken down into linear algebra commands COMB_MATR_ASSE, CREA_CHAMP, FACTORISER, RESOUDRE.

The tests are therefore duplicated and it is checked that the results are consistent.