Nodal boundary condition error

Lea

Hello,

I am trying to apply nodal boundary conditions with scattered data. The goal is to split one large model into two seprerate ones and use the outflow of the first one as inflow for the second model. Since the velocity profile is complex, I extracted the velocity data from the output to a csv file and now want to use this data as nodal boundary condition for the second half of the model. This however leads to the following error (same for all conditions): 

NODAL_BOUNDARY_CONDITION( "Advanced - z_velocity" )
acuPrep: *** ERROR: Scattered data is non-planar

Since it is only possible to include scattered date with xyz-coordinates, I am wondering how this data is supposted to be planar?

 

Thank you in advance!

Lea

 

acupro

The data (source and target) need to be planar.  So for example, a planar outlet mapped to a planar inlet.  Best to use the   acuGetNodeSubset   script to extract the data from the planar outlet, to then arrange for the planar inlet with the NBC.   acuGetNodeSubset -h    for usage

acupro

The data (source and target) need to be planar.  So for example, a planar outlet mapped to a planar inlet.  Best to use the   acuGetNodeSubset   script to extract the data from the planar outlet, to then arrange for the planar inlet with the NBC.   acuGetNodeSubset -h    for usage

Lea

acupro_21778 said:

The data (source and target) need to be planar.  So for example, a planar outlet mapped to a planar inlet.  Best to use the   acuGetNodeSubset   script to extract the data from the planar outlet, to then arrange for the planar inlet with the NBC.   acuGetNodeSubset -h    for usage

Thank you, it worked!

one more question: I read in another post that you should always use an nodal boundary condition with a simple boundary condition. How does that work? Right now I only use a nbc for pressure, velocity, eddy frequency, eddy viscosity and kinetic energy. The simulation runs smoothly but my results are not as they supposted to be. Could this be the reason? Did I miss any parameters that are requiered for nbc to work as inflow?

Thanks again

Lea

acupro

Lea said:

Thank you, it worked!

one more question: I read in another post that you should always use an nodal boundary condition with a simple boundary condition. How does that work? Right now I only use a nbc for pressure, velocity, eddy frequency, eddy viscosity and kinetic energy. The simulation runs smoothly but my results are not as they supposted to be. Could this be the reason? Did I miss any parameters that are requiered for nbc to work as inflow?

Thanks again

Lea

I would recommend not using the Pressure NBC at the inlet - as then you've specified both velocity and pressure which is over-specification.  Instead, I would add Element BCs for both the pressure and tangential_traction variables, with type = free.

That is the benefit to using a Simple BC - that takes care of all the details in the background, as Simple BC is really a combination NBCs and EBCs - then add NBCs with a higher precedence, say 2, to handle what you want to explicitly set.  It may be easier to use Simple BC with a velocity inflow type - then add your desired NBCs - but still not for pressure.  Let the inlet pressure be calculated from the solution, to be consistent with the outlet.

Lea

acupro_21778 said:

I would recommend not using the Pressure NBC at the inlet - as then you've specified both velocity and pressure which is over-specification.  Instead, I would add Element BCs for both the pressure and tangential_traction variables, with type = free.

That is the benefit to using a Simple BC - that takes care of all the details in the background, as Simple BC is really a combination NBCs and EBCs - then add NBCs with a higher precedence, say 2, to handle what you want to explicitly set.  It may be easier to use Simple BC with a velocity inflow type - then add your desired NBCs - but still not for pressure.  Let the inlet pressure be calculated from the solution, to be consistent with the outlet.

Thank you, that was very helpful! The results look much better now that I added an EBC for pressure instead of a NBC.