ACPOWER

I/O Options and Subcase Information Entry Used in the I/O Options section or in frequency response (direct and modal) subcases to request acoustic power radiated across a panel for Infinite Elements and Adaptive Perfectly Matched Layer (APML).

Format

ACPOWER (format) = option

Definitions


Argument	Options	Description
`format`	<H3D, PUNCH, blank>	H3D Results are output in Hyper3D format (.h3d file). PUNCH Results are output in Punch format (.pch file). Blank (Default) Results are output in all active formats for which the result is available.
`option`	<YES, ALL, NO, NONE>	YES, ALL (Default), blank The acoustic power is computed for all panels defined by PANELG with ACPOWER type in the Bulk section. 1 NO, NONE Acoustic Power is not output.

Comments

The result is output for every PANELG entry whose type is ACPOWER. In this case, PANELG also accommodates a SURF entry.
Acoustic Power results are available for Infinite Elements and Adaptive Perfectly Matched Layer (APML). It is supported for both H3D and PUNCH formats.
Multiple formats are allowed on the same entry; these should be comma-separated. If a format is not specified, this output control applies to all formats defined by the OUTPUT command, for which the result is available.
Multiple instances of this card are allowed; if instances are conflicting, the last instance dominates.
The acoustic power is calculated using the surface integral of the real part ( $R_{e}$ ) of acoustic intensity $\underline{I} (Ω)$ .
$P = \int_{s} Re [\underline{I} (Ω)] \cdot \underline{n} d S$
Where,

$S$

Surface area of the panel

$n$

Local normal of the surface

The expression for acoustic intensity is related to the nodal pressure ( $p$ ) and the complex conjugate of the particle velocity ( $ν *$ ), given by:
$\underline{I} (Ω) = \frac{1}{2} p \underline{v} *$
The calculation of ACPOWER in decibels (dB) is performed using the PARAM, ACPREFDB, for which the following equation is used. ACPREFDB is the reference value of the power. This output is currently available only in PUNCH format.
$A C P O W E R (d B) = 10 * \log_{10} (\frac{A C P O W E R}{A C P R E F D B})$
Where,

$A C P O W E R (d b)$

Acoustic power in decibels.

$A C P R E F D B$

Reference acoustic power value specified using PARAM,ACPREFDB.