foamedOver - A Library to Add a Dynamic Overset Grid Capability to ...

foamedOver 

A Library to Add a Dynamic Overset Grid Capability to OpenFOAM 

David Boger Ralph Noack Eric Paterson 

Penn State University, Applied Research Lab 

State College, PA USA 

5th OpenFOAM Workshop 

21 - 24 June 2010 

Chalmers University of Technology 

Göteborg, Sweden 

Boger, Noack, and Paterson (PSU/ARL) foamedOver OFW5 1 / 25

Outline 

1 Background 

Overset Grids 

Overset Grid Approach 

Suggar++ 

DiRTlib 

2 foamedOver 

3 Results 

Standard Applications 

Dynamic Meshes 

4 Summary 


Definition 

An overset grid assembly is 

comprised of a set of grids 

(structured, unstructured, or mixed) 

The grids overlap each other 

arbitrarily to cover the domain 

Component grids are constructed 

(mostly) independent of one another 

Field equations are connected by 

interpolation across the overlapping 

boundaries 


Advantages 

Overset grids are a major enabling 

technology for 

◮ Complex geometries 

⋆ Component grids can be built 

independently 

⋆ Components can be easily 

modified, added, or removed 

◮ Bodies in relative motion 

◮ Tracking of important flow features 

⋆ Grid points are added only where 

they are needed 


Advantages 





independently 








Advantages 





independently 








Advantages 





independently 








Overset Grid Approach 


Overset Hole Cutting 


Overset Fringe Boundary Points 


Overset Overlap Minimization 


Requirements 

Obtain the Domain Connectivity Information (DCI) 

◮ Determine in/out/fringe status and interpolation stencils 

Read, access, and utilize the DCI 

◮ Perform interpolation of the dependent variables 

Modify the solver to exclude out cells 

◮ Equation solvers, residual measures, volume averaging, etc. 

Modify the field equations at fringe points 

◮ Replace governing equations by interpolation 

Move the grids 

Fix force and moment integrals on overlapping surfaces 


Suggar++ 1 

Overset grid assembly software 

Performs hole-cutting, donor search, 

overlap minimization 

Static or dynamic (moving body) 

assemblies 

Structured and unstructured grids 

Node-centered and cell-centered flow 

solvers 

Stand-alone executable (static) or 

library calls for dynamic grids 

(libsuggar.so) 

1 Ralph W. Noack, David A. Boger, Robert F. Kunz, and Pablo M. Carrica, "Suggar++: An Improved General Overset Grid 

Assembly Capability," AIAA Paper 2009-3992 


DiRTlib 2 

DiRTlib is a solver-neutral library that simplifies the addition of an 

overset capability to a flow solver by encapsulating the required 

operations 

Acquire interpolation stencils via file 

I/O or direct communication with 

libSuggar++ 

Provides higher-level methods to 

transfer field data from donors to 

receptors and interpolate 

Provides lower-level access to donor 

member indices and weights to help 

build implicit global matrix 

drt_get_dci() 

drt_generate_transmit_apply() 

drt_get_donor_members_donor_weights() 

2 Ralph W. Noack, “DiRTlib: A Library to Add an Overset Capability to Your Flow Solver” AIAA 2005-5116 



FoamedOver is an interface between OpenFOAM and other 

specialized libraries 

DiRTlib – Library to facilitate 

the addition of overset 

capability to any flow solver 

Suggar++ – Overset grid 

assembly software 

PETSc – Library of data 

structures and routines for the 

parallel solution of large 

systems of linear and 

non-linear equations 



FoamedOver is a collection of custom classes, solvers, and 

applications. 



FoamedOver is a stand-alone library that provides a dynamic overset 

grid capability to any OpenFOAM solver 

No changes are required to 

the OpenFOAM library itself 

Any OpenFOAM solver is 

made overset-capable by the 

insertion of a half-dozen lines 

of code . . . 

. . . and the use of custom 

run-time selectable objects 

# include “oversetObject.H” 

# include “createOverset.H” 

overset.updateFringeValues(U); 

dynamicFvMesh oversetFvMesh; 

mesh.update() 


Run–Time Selectable Objects 


Potential Foam 

cylinder 

steady 

potential flow 


interFoam 

submerged hydrofoil a 

steady 

incompressible multiphase 

a J. Duncan, "The Breaking and Non-Breaking Wave 

Resistance of a Two-Dimensional Hydrofoil," J. Fluid Mech, 

126:507–520, 1983. 


interFoam 

extension of damBreak tutorial 

unsteady 

incompressible multiphase 


compressibleInterFoam 

extension of depthCharge 

tutorial 

unsteady 

compressible multiphase 


Unsteady potential flow 

cylinder 

prescribed mesh motion 

unsteady 

unsteady potentail flow is a 

series of steady solutions 


icoDyMFoam 

pitching foil 

prescribed mesh motion 

incompressible, laminar flow 


interDyMFoam 

falling cylinder 

6DOF mesh motion 

incompressible, laminar flow 

Compare to simplified 

analytical solution for 

free-falling body with constant 

CD 


Two Paddles 

interlacing rotating paddles 

motion would be very difficult 

to resolve with GGI, RBF, or 

Laplacian dynamicFvMesh 

methods. 


Water Entry 


Summary 

foamedOver is a collection of custom classes, solvers, and 

applications 

It is a stand-alone library that provides a dynamic overset grid 

capability to any OpenFOAM solver 

motionObjects have been developed which permit prescribed, 

analytical, and 6DOF motions 

For now, it is controlled by ITAR 3 , and not available outside the 

USA 

Future work 

◮ Develop interface with native OpenFOAM algebraic solvers. 

◮ Parallel efficiency 

3 International Traffic in Arms Regulations

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