ApplyGravity is not working

[George.B]

Hi Guys,

I wanna apply gravity on the set of "load". This is the input file:

<GranOO Version="2.0" TotIteration="20000" TimeStep="1e-8" OutDir="Results_003">
<PreProcessing>
<PlugIn Id="BuildDomain" Message="polyhed.off" Length="1" Radius="10" Numberx="8" Numbery="1" Density="1" Case="23" Run="23" RandomOrientation="0"/>
<PlugIn Id="_ConvertElementPairToBeam" Set="harddd" YoungModulus="10e9" RadiusRatio="0.6" PoissonRatio="0.3" MaxStress="0" />
<PlugIn Id="_ConvertElementPairToBeam" Set="softtt" YoungModulus="10e7" RadiusRatio="0.6" PoissonRatio="0.45" MaxStress="0" />
<PlugIn Id="_ComputeOptimalTimeStep" Ratio="0.1" />
<PlugIn Id="InitSensor" />
</PreProcessing>
<Processing>

<PlugIn Id="_ClearLoad"/>
<PlugIn Id="_ApplyBondLoad"/>
<PlugIn Id="_ApplyGravity" X="0" Y="0" Z="-9" Set="load"/>
<PlugIn Id="_IntegrateAcceleration" Linear="Yes" Angular="Yes"/>
<PlugIn Id="_ImposeDisplacement" Z="0*it" Set="boundary1"/>

<PlugIn Id="_Check"/>
<PlugIn Id="_SaveDomain" IterLoop="1000" />
<PlugIn Id="_WriteSensorData" IterLoop="1000"/>

</Processing>
<PostProcessing>
</PostProcessing>
</GranOO>

But the plugin "_ApplyGravity" has no effects on the DEs. They do not move at all.

What do you think the problem is?

Thank you so much for your help :)

[jeremie.girardot]

Hard to say for me....

did you check that you have the set of named "load" when you open your domain with grqnoo-viewer ?
Is it filled with Discrete Elements ?

Also, you specified a timeStep, but you use the plugIn "ComputeOptimaleTimeStep", which will change the timestep...

[A.SH.K]

The set "load" is well defined. When I apply an initial velocity or impose displacement, the set moves well. But, when I apply gravity nothing happens.
Yes, the plugIn "ComputeOptimaleTimeStep" changes the time step, but it still should work. The only difference is that the time step gets smaller.

[Damien André]

It has really no effect ? Did you monitor the values of the displacements of each discrete element ?
These displacements may be very tiny depending on the time step : small time step = tiny displacement.