Learning Forum

[ferranj2]

I need to apply a centripetal force to a compressor blade to do a hot-to-cold correction.
I've been exploring the GUI and looking online, but from my searching, it seems that this is not possible within Static Structural.
The closest load available is the "Rotational Velocity" but that is centrifugal in nature.
Is there a way to invert the effect of "Rotational Velocity" so that it pushes the structure inwards ("petal") as oppossed to outward ("fugal")?
Maybe there is a way to specify this with a user-defined load (if that exists)?

I've done this before but with MSC Nastran by scaling an RFORCE card by -1 using a LOAD entry.
If Static Structural can't do this, would it be possible to load BDF inputs and OP2/HDF5 outputs into Workbench as external models that can be piped into a Modal Analysis?

[dlooman]

It appears that the sign of a negative rotational velocity is ignored, so that's not a way.  It is possible to specify a negative mass density.  That will produce centripetal forces due to rotational velocity.

[MissSophie58]

 

@Tiny Fishing So is there any other way?

 

[dlooman]

I was wrong about the sign of the rotational velocity being ignored.  It's just that the centrifugal forces are the same whether the rotational velocity is positive or negative.  There is an APDL way to apply centripetal force as illustrated by the commands below.  The LDREAD command can read the reaction forces from a previous solution.  So the idea is to apply the rotational velocity to the model completely fixed and then read the reaction forces into a subsequent analysis LDREAD,REAC,Last.   Because the reaction forces have the opposite sign of the centrifugal forces, they are converted to centripetal forces.  This procedure might be problematic in Workbench Mechanical because the initial rst file has to be moved to the working directory and Mechanical deletes all the files when the solution starts.  Maybe a command like /sys, copy D:\path\file.rst .  could copy it over just before the LDREAD command.

/prep7
et,1,185
mp,ex,1,1e7
mp,nuxy,1,0.3
mp,dens,1,0.000754
block,9,10,,10,,1
esize,.5
vmesh,1

d,all,all
fini

/solu
omega,,,1000
solve
fini

/prep7
ddele,all,all
omega,0,0,0        ! Zero rotational velocity
nsel,s,loc,y,0
d,all,all
nsel,all
ldread,reac,last   ! Read reaction forces from first analysis
fini

/solu
solve
fini

/post1
set,last
plnsol,ux