Plate / wall thickness

The thickness of the perforated sheet. It is the length of the porous jump the solver uses (only $I\,t = K$ matters there), the $l$ of $l/d$ in the thick-plate formula, and, for a perforated tube, one of the two inputs of the discharge-coefficient table.

Last updated 2026-11-03

Theory

The wall itself is not meshed with a thickness: it is a zero-thickness cyclic pair of faces. The thickness enters in three places:

The jump's length: OpenFOAM's porousBafflePressure multiplies its per-length coefficients by a length (OpenFOAM user guide, 2026); the program writes $I = K/t$ and length $t$ , so the inertial loss is independent of $t$ , equation (1). The viscous Darcy term (Darcy coefficient D) does scale with $t$ .
The thick-plate formula of a perpendicular plate: $l/d = t/d$ (Plate formula).
The no-grazing discharge coefficient $C_{D0}$ of a perforated tube, interpolated in a table of hole diameter and thickness (Discharge coefficient C_D0). The thickness also feeds the acoustic perforate models.

Equations

\Delta p = \left(\mu D + \tfrac12\rho\,\frac{K}{t}\lvert U_n\rvert\right) U_n\,t = \mu D\,t\,U_n + \tfrac12\rho K\lvert U_n\rvert U_n

(1)

where	meaning	unit
$\Delta p$	Pressure jump	Pa
$t$	Wall thickness	m
$\mu$	Dynamic viscosity	Pa·s
$D$	Darcy coefficient	1/m²
$K$	Loss coefficient	-
$U_n$	Velocity normal to the wall face	m/s

Default and rule

Default: 1 mm
Rule: 1 mm.
Source: Jump law: (OpenFOAM user guide, 2026). Thick plate: (Idelchik, 2008). Discharge-coefficient table: Elnady's measured values (doctoral thesis, KTH 2004; the related paper is (Elnady et al., 2010)).

Valid range t > 0

Values

Above 0, in millimetres on the card.

Thickness and K

A typed $K$ is not corrected for the thickness; the thin-plate formula ignores it. Use the thick-plate formula or a measured $K$ for a sheet that is thick relative to its holes.

Outside the discharge-coefficient table

The table covers 0.5-2.5 mm; outside it the edge value is used (the card says so). Elnady measured 0.8-2.4 mm; the rest of the table is his extrapolation.

Theory

Equations

Default and rule

Valid range t > 0

Related 5

References 3