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time-varying bc: "scale-time"

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Old   July 30, 2018, 14:54
Default time-varying bc: "scale-time"
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Hi,
I have the OpenFOAM-5.0 and I want to create a wave with the "setWaves tool". I'm following the wave tutorial (/multiphase/interFoam/laminar/wave). It's by default setting up with the Airy wave model for the velocity, where the U specifications for the left side are as below:

left
{
type waveVelocity;

origin (0 0 0);

direction (1 0 0);

speed 2;

waves

(
Airy

{

length 300;
amplitude 2.5;
phase 0;
angle 0;
}
);
scale table ((1200 1) (1800 0))
crossScale constant 1;
}
It supposed that a wave is created from the left side with the specified parameters. The "scale" function (that in this case is involved with "table" function), define a time-varying boundary condition, but I don't know how it works. I searched in the OpenFOAM-Userguide and for "table" function is understood there are two inputs (time1 value1) (time2 value2). For this case they are (1200 1) (1800 0), I guess 1200 and 1800 are times (according to the description of the Userguide), however in the original case the time is set up until 200 seconds, then it doesn't make sense for me, but the case works so I think that has another meaning. I don't know what crossScale means eather. I looked at the waveVelocityFvPatchVectorField.H (that remains in /opt/openfoam5/src/waves/derivedFvPatchFields/waveVelocity), where a description is showned:

Description
This boundary condition provides a waveVelocity condition. This sets the
velocity to that specified by a superposition of wave models. The
corresponding phase fraction condition looks this condition up and re-uses
the wave modelling.
Usage
\table
Property | Description | Req'd? | Default
origin | origin of the wave coordinate system | yes |
direction | direction of the mean flow | yes |
speed | speed of the mean flow | yes |
waves | list of wave models to superimpose | yes |
scale | scale factor along the mean flow direction | no | None
crossScale | scale factor across the mean flow direction | no | None
phi | Name of the flux field | no | phi
\endtable
I find that that description it's not enough to understand how scale and crossScale work.

When I ran the simulation, it looks good, but when I change the some values in the brackets of table, the results of the simulation becomes strange.

I would appreciate if someone knows anything about this matter.
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Old   March 30, 2019, 21:05
Default not time-varying bc, but position-varying initial condition
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Charles
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Not sure if you find answer. But here is an explanation of how to use the scale.



scale table ((1200 1) (1800 0))


The table is not time a varying table but a position varying table. It means, before x=1200 meter, the scale is 1, and, after x = 1800 meter, the scale is 0 (i.e. no wave), and in between 1200 and 1800, the scale is a ramp from 1 to 0 (i.e. wave is damping out within 600 meters).
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