Theory

The baseline computes the exact viscous impedance of the hole as a short tube plus an end correction. A real sharp-edged hole acts as if it were narrower (vena contracta). Elnady's model (Elnady et al., 2010) accounts for this by dividing the hole impedance by $C_D$ ; this option applies the same step to the baseline, equation (1). With the option off, the baseline is the plain thin-plate theory, and existing cases give unchanged results.

Equations

\zeta_h = \frac{1}{C_D}\,\frac{1}{\rho c}\left[\frac{i\omega\rho t}{F(k_s d)} + i\omega\rho\,\epsilon f_{int} d\right]

(1)

where	meaning	unit
$C_D$	Discharge coefficient (Discharge coefficient C_D (acoustics))	-
$F$	Crandall's viscous tube function, $1 - 2J_1(k_s a)/(k_s a J_0(k_s a))$	-
$k_s$	Stokes wavenumber, $k_s^2 = -i\omega\rho/\mu$	1/m
$\epsilon$	End-correction factor	-
$f_{int}$	Hole-interaction factor (1 without interaction)	-

Default and rule

Default: off
Rule: Off.
Source: The division by $C_D$ follows (Elnady et al., 2010) eq. (6).

Valid range on / off (thin-plate physics baseline only)

Applies to

The thin-plate physics baseline only; the Elnady model always uses $C_D$ , the other models never do.

References 1

Elnady, T., Åbom, M. and Allam, S. (2010). Modeling perforates in mufflers using two-ports. Journal of Vibration and Acoustics, 132(6), 061010. DOI 10.1115/1.4001510

Theory

Equations

Default and rule

Valid range on / off (thin-plate physics baseline only)

Related 5

References 1