Using forces in other classes

flowris · May 7, 2012, 11:49

Hello,

I have a mesh motion class that works very well for prescribed motion. I would like to use this class to do rigid body displacements, under the influence of the fluid forces. I can also calculate the forces using the standard forces function.

How can I take the results from this force calculation at each time step, and bring them into my mesh motion class for further use?

boger · May 8, 2012, 08:14

One way would be to instantiate a forces object from within your class and use the calcForcesMoment() method to get the forces and moments acting on your object.

flowris · May 8, 2012, 08:40

Excellent! I saw that in the sixDoFRigidBodyDisplacement class, but was not sure if this was what I was looking for. I'll try and learn to use it.

Many thanks!

flowris · May 8, 2012, 11:22

Do you know more about objectRegistry? I am trying to instantiate a forces object, as you suggested:

Code:

    dictionary forcesDict;

    forcesDict.add("patches", "block");
    forcesDict.add("rhoName", "rhoInf");
    forcesDict.add("rhoInf", 1000);
    vector centreOfMass_(0.0,0.0,0.0);
    forcesDict.add("CofR", centreOfMass_);

    forces f("forces", db(), forcesDict);

But in the last line, where is written "db()", I should put a reference to the objectRegistry. What is this, and how do I reference to it?

flowris · June 5, 2012, 11:38

Can anybody tell me how to instantiate a forces object in a new class, or give an example where it is done?

flowris · June 5, 2012, 13:56

Simply writing

Code:

    forces f("forces", db(), forcesDict);

results in the compiling error

Code:

hppGgiFvMesh.C: In member function ‘void Foam::hppGgiFvMesh::getMoment()’:
hppGgiFvMesh.C:358: error: reference to ‘db’ is ambiguous
/home/jmatthei/OpenFOAM/OpenFOAM-1.6-ext/src/OpenFOAM/lnInclude/IOobject.H:236: error: candidates are: const Foam::objectRegistry& Foam::IOobject::db() const
/home/jmatthei/OpenFOAM/OpenFOAM-1.6-ext/src/OpenFOAM/lnInclude/IOobject.H:236: error:                 const Foam::objectRegistry& Foam::IOobject::db() const
/home/jmatthei/OpenFOAM/OpenFOAM-1.6-ext/src/OpenFOAM/lnInclude/IOobject.H:236: error:                 const Foam::objectRegistry& Foam::IOobject::db() const
hppGgiFvMesh.C:358: error: reference to ‘db’ is ambiguous
/home/jmatthei/OpenFOAM/OpenFOAM-1.6-ext/src/OpenFOAM/lnInclude/IOobject.H:236: error: candidates are: const Foam::objectRegistry& Foam::IOobject::db() const
/home/jmatthei/OpenFOAM/OpenFOAM-1.6-ext/src/OpenFOAM/lnInclude/IOobject.H:236: error:                 const Foam::objectRegistry& Foam::IOobject::db() const

brdvolde · August 19, 2016, 11:32

Have you found a solution for this problem?

giovastabile · August 26, 2016, 12:57

I have also the same problem

louisgag · November 3, 2017, 13:41

Quote:

Originally Posted by giovastabile

I have also the same problem

And so do I, anyone knows how to access the db() objectRegistry required by the

Code:

forces f("forces", db(), forcesDict);

call directly from a solver?

May 7, 2012, 11:49	Using forces in other classes	#1
flowris Senior Member Join Date: Apr 2010 Posts: 151 Rep Power: 16	Hello, I have a mesh motion class that works very well for prescribed motion. I would like to use this class to do rigid body displacements, under the influence of the fluid forces. I can also calculate the forces using the standard forces function. How can I take the results from this force calculation at each time step, and bring them into my mesh motion class for further use?

May 8, 2012, 08:14		#2
boger Senior Member David Boger Join Date: Mar 2009 Location: Penn State Applied Research Laboratory Posts: 146 Rep Power: 17	One way would be to instantiate a forces object from within your class and use the calcForcesMoment() method to get the forces and moments acting on your object. __________________ David A. Boger

May 8, 2012, 11:22		#4
flowris Senior Member Join Date: Apr 2010 Posts: 151 Rep Power: 16	Do you know more about objectRegistry? I am trying to instantiate a forces object, as you suggested: Code: dictionary forcesDict; forcesDict.add("patches", "block"); forcesDict.add("rhoName", "rhoInf"); forcesDict.add("rhoInf", 1000); vector centreOfMass_(0.0,0.0,0.0); forcesDict.add("CofR", centreOfMass_); forces f("forces", db(), forcesDict); But in the last line, where is written "db()", I should put a reference to the objectRegistry. What is this, and how do I reference to it?

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May 8, 2012, 08:40		#3
flowris Senior Member Join Date: Apr 2010 Posts: 151 Rep Power: 16	Excellent! I saw that in the sixDoFRigidBodyDisplacement class, but was not sure if this was what I was looking for. I'll try and learn to use it. Many thanks!

June 5, 2012, 11:38		#5
flowris Senior Member Join Date: Apr 2010 Posts: 151 Rep Power: 16	Can anybody tell me how to instantiate a forces object in a new class, or give an example where it is done?

August 19, 2016, 11:32		#7
brdvolde New Member Brecht Devolder Join Date: Oct 2014 Posts: 2 Rep Power: 0	Have you found a solution for this problem?

August 26, 2016, 12:57		#8
giovastabile New Member Giovanni Stabile Join Date: Sep 2014 Location: Trieste (Italy) - Florence (Italy) Posts: 14 Rep Power: 12	I have also the same problem