Coupled Motion of Two Floating Objects. Minghao Wu

Transcription

1 Project assignment for the course CFD with OpenSource Software, 2015 Minghao Wu Department of Shipping and Marine Technology Chalmers University of Technology

2 Introduction Introduction of the topic Environment: OpenFOAM 2.4.x, interdymfoam Two cases Uncoupled motion of two floating objects

3 Uncoupled motion of two floating objects Uncoupled motion of two floating objects Description Description

4 Uncoupled motion of two floating objects Terminal Command cp -r $FOAM_TUTORIALS/multiphase/interDyMFoam/ras/floatingObjec t $FOAM_RUN cd $FOAM_RUN mv floatingobject uncoupledfloatingobjects cd uncoupledfloatingobjects

5 Uncoupled motion of two floating objects blockmeshdict blockmeshdict Vertices ( (-1 0 0) (1 0 0) (1 1 0) (-1 1 0) (-1 0 1) (1 0 1) (1 1 1) (-1 1 1) ); floatingobject1 { type wall; faces (); } floatingobject2 { type wall; faces (); }

6 Uncoupled motion of two floating objects toposetdict toposetdict actions ( {name c1; type cellset; action new; source boxtocell; sourceinfo {box ( ) ( );} } {name c1; type cellset; action invert;} ); actions ( {name c2; type cellset; action new; source boxtocell; sourceinfo {box ( ) ( );} } {name c2; type cellset; action invert;} );

7 Uncoupled motion of two floating objects dynamicmeshdict dynamicmeshdict dynamicfvmesh dynamicmotionsolverfvmesh; motionsolverlibs ( "libsixdofrigidbodymotion.so" "libfvmotionsolvers.so" ); solver displacementlaplacian; displacementlaplaciancoeffs { diffusivity inversedistance (floatingobject1 floatingobject2); }

8 pointdisplacement Uncoupled motion of two floating objects pointdisplacement floatingobject1 {type sixdofrigidbodydisplacement; mass 4; centreofmass ( ); momentofinertia ( ); rhoname rhoinf; rhoinf 1; report on; value uniform (0 0 0); constraints {fixedpoint1 {sixdofrigidbodymotionconstraint point; centreofrotation ( );} } } floatingobject2 {type sixdofrigidbodydisplacement; mass 4; centreofmass ( ); momentofinertia ( ); rhoname rhoinf; rhoinf 1; report on; value uniform (0 0 0); constraints {fixedpoint2 {sixdofrigidbodymotionconstraint point; centreofrotation ( );} } }

9 Other boundary values Uncoupled motion of two floating objects Other boundary values cd $FOAM_RUN/uncoupledFloatingObjects/0.org sed -i s/floatingobject/floatingobject1/g * sed -i 37r<(sed 34,37!d alpha.water) alpha.water sed -i 45r<(sed 38,45!d epsilon) epsilon sed -i 39r<(sed 35,39!d k) k sed -i 44r<(sed 37,44!d nut) nut sed -i 41r<(sed 38,41!d p_rgh) p_rgh sed -i 38r<(sed 34,38!d U) U sed -i 0,/floatingObject1/! {0,/floatingObject1/ s/floatingobject1/floatingobject2/} *

10 Uncoupled motion of two floating objects fvsolution fvsolution "celldisplacement.*" { solver GAMG; tolerance 1e-8; reltol 0; smoother GaussSeidel; cacheagglomeration true; ncellincoarsestlevel 10; agglomerator faceareapair; mergelevels 1; }

11 Uncoupled motion of two floating objects Allrun Allrun runapplication blockmesh #run toposet for object1 #use runapplication runapplication toposet -dict system/object1toposet runapplication subsetmesh -overwrite c1 -patch floatingobject1 #Cleaning logs when runapplication is used rm log.toposet rm log.subsetmesh #run toposet for object2 #without runapplication toposet -dict system/object2toposet runapplication subsetmesh -overwrite c2 -patch floatingobject2 cp -r 0.org 0 > /dev/null 2>&1 runapplication setfields runapplication $application

12 Description Description Spring Damper Hinge Catenary

13 Description Description Two objects linked with springs

14 A glimpse of linearspring.c A glimpse of linearspring.c restraintposition = motion.transform(refattachmentpt_); r = restraintposition - anchor_; magr = mag(r); r /= (magr + VSMALL); restraintforce = -stiffness_*(magr-restlength_)*rdamping_*(r & v)*r;

15 Terminal command cd $WM_PROJECT_USER_DIR mkdir src cd $WM_PROJECT_DIR/src cp -r sixdofrigidbodymotion $WM_PROJECT_USER_DIR/src Cd $WM_PROJECT_USER_DIR/src mv sixdofrigidbodymotion mysixdofrigidbodymotion cd mysixdofrigidbodymotion cd mysixdofrigidbodymotion/sixdofrigidbodymotion/restraints cp -r linearspring couplinglinearspring cd couplinglinearspring mv linearspring.c couplinglinearspring.c mv linearspring.h couplinglinearspring.h sed -i s/linearspring/couplinglinearspring/g couplinglinearspring.*

16 Make/files Make/files restraints = sixdofrigidbodymotion/restraints $(restraints)/sixdofrigidbodymotionrestraint/sixdofrigidbodymotionrestraint.c $(restraints)/sixdofrigidbodymotionrestraint/sixdofrigidbodymotionrestraintnew. C $(restraints)/couplinglinearspring/couplinglinearspring.c LIB = $(FOAM_USER_LIBBIN)/libmysixDoFRigidBodyMotion

17 Identification of objects sixdofrigidbodymotion.h sixdofrigidbodymotion.h class sixdofrigidbodymotion { // Private data Switch report_; //- Name of the rigid body word rigidbodyname_; //- Name of the coupled body word coupledbodyname_; class sixdofrigidbodymotion {... Public... // Member Functions // Access inline bool report() const; //- Return the Name inline word rigidbodyname() const; //- Return the coupled body name inline word coupledbodyname() const;...

18 Identification of objects sixdofrigidbodymotioni.h sixdofrigidbodymotioni.h // * * * * * * * * * Member Functions * * * * * * * * * // inline Foam::scalar Foam::sixDoFRigidBodyMotion::mass() const { return mass_; }... inline Foam::word Foam::sixDoFRigidBodyMotion::rigidBodyName() const { return rigidbodyname_; } inline Foam::word Foam::sixDoFRigidBodyMotion::coupledBodyName() const { return coupledbodyname_; }

19 Identification of objects sixdofrigidbodymotion.c sixdofrigidbodymotion.c // * * * * * * * * * * Constructors * * * * * * * * * // Foam::sixDoFRigidBodyMotion::sixDoFRigidBodyMotion() :... report_(false), rigidbodyname_(), coupledbodyname_() {}... Foam::sixDoFRigidBodyMotion::sixDoFRigidBodyMotion (const dictionary& dict, const dictionary& statedict):... rigidbodyname_(dict.lookupordefault<word>("rigidbodyname","rigidbody 1")), coupledbodyname_(dict.lookupordefault<word>("coupledbodyname","none" )) {

20 Identification of objects sixdofrigidbodymotion.c sixdofrigidbodymotion.c Foam::sixDoFRigidBodyMotion::sixDoFRigidBodyMotion ( const sixdofrigidbodymotion& sdofrbm ) :... report_(sdofrbm.report_), rigidbodyname_(sdofrbm.rigidbodyname_), coupledbodyname_(sdofrbm.coupledbodyname_) {}...

21 Identification of objects sixdofrigidbodymotion.c sixdofrigidbodymotion.c void Foam::sixDoFRigidBodyMotion::status() const { Info<< "6-DoF rigid body motion" << nl << " Name of rigid body: " << rigidbodyname() << nl << " Centre of rotation: " << centreofrotation() << nl << " Centre of mass: " << centreofmass() << nl << " Orientation: " << orientation() << nl << " Linear velocity: " << v() << nl << " Angular velocity: " << omega() << endl; }

22 Identification of objects sixdofrigidbodymotionio.c sixdofrigidbodymotionio.c motionstate_.write(os);... os.writekeyword("rigidbodyname") << rigidbodyname_ << token::end_statement << nl; os.writekeyword("coupledbodyname") << coupledbodyname_ << token::end_statement << nl;

23 couplinglinearspring class OFstream and IFstream IFstream ( const filename& pathname, streamformat format=ascii, versionnumber version=currentversion ); // STL stream //- Access to underlying std::istream virtual istream& stdstream(); //- Const access to underlying std::istream virtual const istream& stdstream() const; OFstream and IFstream OFstream (const filename& pathname, streamformat format=ascii, versionnumber version=currentversion, compressiontype compression=uncompressed );

24 couplinglinearspring class couplinglinearspring.c couplinglinearspring.c // Foam classes #include "OFstream.H" #include "IFstream.H" #include "Vector.H" // std classes #include <stdio.h> #include <fstream> #include <iostream> #include <string.h> #include <stdlib.h>

25 couplinglinearspring class couplinglinearspring.c couplinglinearspring.c OFstream restrainpositionoutputx(motion.rigidbodyname()+"x"); OFstream restrainpositionoutputy(motion.rigidbodyname()+"y"); OFstream restrainpositionoutputz(motion.rigidbodyname()+"z"); IFstream AnchorInputX(motion.coupledBodyName()+"X"); IFstream AnchorInputY(motion.coupledBodyName()+"Y"); IFstream AnchorInputZ(motion.coupledBodyName()+"Z"); double AX,AY,AZ; char temp[100];

26 couplinglinearspring class couplinglinearspring.c couplinglinearspring.c AnchorInputX.stdStream().getline(temp, 100); AX=(double)strtod(temp,NULL); AnchorInputY.stdStream().getline(temp, 100); AY=(double)strtod(temp,NULL); AnchorInputZ.stdStream().getline(temp, 100); AZ=(double)strtod(temp,NULL); Vector<double> anchor_(ax, AY, AZ); restrainpositionoutputx << restraintposition.x()<< nl << endl; restrainpositionoutputy << restraintposition.y()<< nl << endl; restrainpositionoutputz << restraintposition.z()<< nl << endl; Info<< " anchor position " << anchor_<< endl;

27 couplinglinearspring class Compiling Compiling cd $WM_PROJECT_USER_DIR/src/sixDoFRigidBodyMotion wclean wmake libso Prepare for running cd $FOAM_RUN cp -r uncoupledfloatingobjects coupledfloatingobjects

28 0.org/pointDisplacement Run the case floatingobject1 { rigidbodyname floatingobject1; coupledbodyname floatingobject2; type sixdofrigidbodydisplacement; mass 4; centreofmass ( ); momentofinertia ( ); rhoname rhoinf; rhoinf 1; report on; value uniform (0 0 0); constraints... restraints { horizontalspring { sixdofrigidbodymotionrestraint CouplinglinearSpring; anchor $anchorofobj1; refattachmentpt ( ); stiffness 35; damping 0; restlength 0.2; } }

29 0.org/pointDisplacement Run the case floatingobject2 { rigidbodyname floatingobject2; coupledbodyname floatingobject1; type sixdofrigidbodydisplacement; mass 4; centreofmass ( ); momentofinertia ( ); rhoname rhoinf; rhoinf 1; report on; value uniform (0 0 0); constraints... restraints { horizontalspring { sixdofrigidbodymotionrestraint CouplinglinearSpring; anchor $anchorofobj1; refattachmentpt ( ); stiffness 35; damping 0; restlength 0.2; } }

30 Constant/dynamicMeshDict Run the case motionsolverlibs ( "libmysixdofrigidbodymotion.so" "libfvmotionsolvers.so" );

31 Run the case Allrun and Allclean Allrun echo "-0.1" >& floatingobject1x echo "0.5" >& floatingobject1y echo "0.6" >& floatingobject1z echo "0.1" >& floatingobject2x echo "0.5" >& floatingobject2y echo "0.6" >& floatingobject2z Allclean rm floatingobject?x rm floatingobject?y rm floatingobject?z

32 Results and Discussions Results Uncoupled case Coupled case t=0s

33 Results and Discussions Results Uncoupled case Coupled case t=0.5s

34 Results and Discussions Results Uncoupled case Coupled case t=1.0s

35 Results and Discussions Results Uncoupled case Coupled case t=1.5s

36 Results and Discussions Results Uncoupled case Coupled case t=2.5s

37 Results and Discussions Results Uncoupled case Coupled case t=3.5s

38 Results and Discussions Discussions

39 Results and Discussions Suggestions for balancing the force In couplinglinearspring.c restraintposition = motion.transform0 (refattachmentpt_); // Use transform instead of transform function In sixdofrigidbodymotion.h // Transformations inline point transform(const point& initialpoints) const; //not changed inline point transform0(const point& initialpoints) const; // added In sixdofrigidbodymotioni.h inline Foam::point Foam::sixDoFRigidBodyMotion::transform0(const point& initialpoint) const { return (centreofrotation() + (Q0() & initialq_.t() & (initialpoint - initialcentreofrotation_))); } // return the tranformation of a point based on previous-step motion

40 Results and Discussions Suggestions for balancing the force Time step should be small if stiffness is high. Slowly varying spring force means it is possible to use transformation based on previous time step motion. Set damping to 0.

41 Results and Discussions Discussions Use dictionary to execute I/O and exchange information between patches It is possible to extend to multiple objects Restraints can be modified to be shared with two objects