Averaging window

simulation_control.transient.averaging_window Unit: s Step 07 · Run Settings

The length of simulated time, at the end of a transient run, over which the pressure drop is averaged. The reported pressure drop is that average; quality gate 2 compares it with the average of the preceding window.

Last updated 2026-11-03

Theory

A transient muffler flow fluctuates, so its pressure drop is a time series. The reported pressure drop is the mean of the monitor samples in the last window, equation (1). Gate 2 computes the same mean for the preceding window and requires the two to agree within the Δp tolerance, but not tighter than 1 %, equation (2) (Δp mean-stability tolerance).

One flow-through time is the natural window, equation (3): every parcel of gas passes through the muffler once.

Equations

\overline{\Delta p_0} = \frac{1}{n_1}\sum_{t_i \in (t_{end}-T_W,\ t_{end}]}\Delta p_0(t_i)

(1)

\frac{\lvert\overline{\Delta p_0} - \overline{\Delta p_0}^{prev}\rvert}{\lvert\overline{\Delta p_0}\rvert} < \max(\varepsilon,\ 1\,\%), \qquad \overline{\Delta p_0}^{prev}\ \text{over}\ (t_{end}-2T_W,\ t_{end}-T_W]

(2)

T_W = t_{FT} = \frac{V_{fluid}}{Q_{total}} \quad \text{(auto)}

(3)

where	meaning	unit
$\Delta p_0(t_i)$	Total-pressure drop at the monitor time $t_i$	Pa
$n_1$	Number of samples in the last window	-
$T_W$	Averaging window	s
$t_{end}$	Last simulated time	s
$\varepsilon$	Δp mean-stability tolerance	%
$t_{FT}$	Flow-through time	s

Default and rule

Default: auto: 1 flow-through time (0.1 s until it is known)Computed by the program
Rule: Auto: one flow-through time. Before the geometry is exported, or while no inlet flow is set, the window is 0.1 s. A typed window longer than the end time triggers a warning.
Source: This is the program's rule; it replaces a fixed window of 0.1 s. It has not yet been validated by a transient run whose window differs from 0.1 s.

Valid range > 0; at most half the end time for the stationarity check

Values

Above 0. The run must cover at least $2T_W$ of simulated time, or gate 2 fails with "less than two averaging windows".

Theory

Equations

Default and rule

Valid range > 0; at most half the end time for the stationarity check

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