MpCCI CouplingEnvironment

The MpCCI CouplingEnvironment has been developed in order to provide an application independent interface for the direct coupling of different simulation codes. MpCCI CouplingEnvironment has been accepted as a ‘de facto’ neutral standard for simulation code coupling and provides a multi-physics framework. Within the MpCCI CouplingEnvironment the engineer can combine several ready to use models, define the application field and choose for the best-fit coupling method.

More information, manuals and the software itself can be found on our product pages at http://www.mpcci.de.
 

Co-Simulation Strategy

MpCCI Coupling Environment employs a staggered approach for all co-simulation problems which can be defined as

  • A globally explicit coupling method: the coupled fields are exchanged only once per coupling step. This solution is applicable to problems with weak physics coupling.
  • An implicit iterative coupling method: the coupled fields are exchanged several times per coupling step until an overall stabilized solution is achieved and before advancing to the next coupling step. This approach is applicable to problems with strong physics coupling.

MpCCI Coupling Environment offers standard coupling algorithms to implement the above coupling approaches - e.g. Gauss-Seidel and Jacobi.  

© Photo Fraunhofer SCAI

Gauss-Seidel coupling scheme is also known as serial or "Ping-Pong" algorithm where one code waits while the partner code proceeds.

Jacobi coupling scheme is also known as parallel algorithm where both analysis codes run concurrently.
© Photo Fraunhofer SCAI

Jacobi coupling scheme is also known as parallel algorithm where both analysis codes run concurrently.

In addition to these coupling algorithms different transfer options are provided to control the data exchange of the quantities:

  • The data exchange can be defined as an optional or forced synchronization point. The optional synchronization point provides the alternative to activate the data exchange on request. This request can be triggered by the availability of the quantities or by a physical quantity criterion. This provides an adaptive coupling scheme where bi-directional and uni-directional data transfer can be mixed.
  • The synchronization point can be defined at different coupling iteration step for a steady state solution, or at different coupling time step sizes for a transient solution. The coupling iteration step, resp. coupling time step size may differ from the solver iteration step, resp. time step size. By this way a sub-cycling has been added to the coupling algorithm.

Co-Simulation Application Types

Coupling analysis of steady state solutions

For stationary problems, it is assumed that there is exactly one solution of the coupled problem, which shall be found. The coupling algorithm does not have a big influence on the solution in this case.
 

Coupling analysis of transient solutions

Typical applications focus on the transient effect of the coupled solution, e.g. pressure oscillation, heat dissipation, etc. The fully transient analysis provides an accurate solution. As the solution is dominated by the time component several co-simulation approaches are supported by MpCCI CouplingEnvironment:

  • Fixed coupling time step size: in this configuration both simulations are constrained to use the same coupling time step size during the complete co-simulation. The time step size is equally defined in each application in this case and there is no need to exchange this time information.
  • Exchange of time step size: instead of using a fixed coupling time step size it is also possible to use adaptive time stepping. In this case the time step size is determined by one code and sent to the partner code, which changes its own time step to the received value.
  • Non-matching time step size: codes may run at different local time stepping and also exchange data at non-matching points in time. MpCCI CouplingEnvironment takes care of a proper ‘interpolation in time’ for the coupled physical quantities. MpCCI CouplingEnvironment offers three different methods for the data time-interpolation: constant, linear, and cubic.
     

Coupling analysis of mixed solutions steady state and transient

A fully transient coupling is challenging because of the great disparities of the physical models between the coupled domains (e.g. fluid-structure, fluid-electromagnetics, FEM structural analysis and discrete element models for particles) and the high computational time. The main difficulty is due to the significant discrepancy of characteristic times since the transient phenomena in the fluid usually take place at a much smaller time scale than those in the solid. The fully transient coupling method describing the transient effects in both coupled domains leads to a highly accurate solution but might be too expensive for some applications. As a computationally cheaper mode you can couple transient models with a sequence of steady state models:

  • Full-vehicle thermal management of driving cycles: In this coupling procedure you should adopt a coupling interval which is at least equal to the solid time step. The flow solution is considered as a sequence of steady state solutions and in the solid the fields evolve in a fully transient manner. This co-simulation provides a flexible solution approach to consider driving cycles. A good compromise between a high computational time and modeling of transient physics is provided by a co-simulation of the transient thermal model with steady-state fluid models in a pseudo-transient approach.
  • Magnetohydrodynamic analysis for electric arcs: In this application you may assume a steady state computation of the electromagnetic phenomena because the electromagnetic phenomena are faster than the gas dynamic. The Maxwell equations will be solves as a sequence of steady state solutions whereas in the fluid the Navier-Stockes equations evolve in fully transient manner.
     

High performant coupling server

The MpCCI CouplingEnvironment offers a high performant exchange of data between the coupled codes. In a very simple but FSI-like benchmark two basic codes running on a standard workstation and exchange pseudo-physical data at high speed. For surface meshes of ~4K nodes on each side the internal server engine of the MpCCI CouplingEnvironment can execute

  • up to ~400 exchanges per second if  the mesh definitions in the coupled codes are incompatible and fixed (identical) coupling time steps are used on both sides
  • if conformal mesh definitions and non-matching-time steps with a ratio of 1/10 are used the code with the coarser time step can send ~200 data sets per second while the ‘fine’ code can receive up to ~2,000 (interpolated-in-time) data sets per second

Exchange of Physical Quantities

MpCCI CouplingEnvironment will automatically exchange the data between the meshes of two or more simulation codes by using the best-fit interpolation method and considering the nature of the quantities exchanged. The co-simulation application can exchange nearly any kind of data between the coupled codes; e.g. energy and momentum sources, material properties, boundary condition values, mesh definitions, or global quantities. To ensure best interoperability between different simulation codes the coupling procedures are independent from the utilized codes and coupling quantities definition: energy sources, e.g. joule heat; momentum sources, e.g. Lorentz forces; boundary conditions values, e.g. temperature, pressure.  All details of the data exchange are automatically handled by a coupling manager behind the concise interface of MpCCI CouplingEnvironment.

Code Interfaces

Open CodeAPI

The MpCCI CouplingEnvironment has an open Programming Interface (API) which can be used to adapt inhouse or further commercial codes. This API is designed as a general and discipline independent toolkit and can be used for different levels of co-simulation:

  • Surface-2-Surface interface suitable for all simulation methods which provide a discretised surface definition, support for deformable walls, and physical quantities located on surface elements or nodes (e.g. for modelling methods like FEM/CSD, FEM/Radiation, FVM/CFD, DEM/Particles, SPH or FPM/fluid models, etc.)
  • Volume-2-Volume coupling suitable for all simulation methods which provide a discretised volume definition and physical quantities located per volume element or per node (e.g. modelling methods like FVM/CFD, FEM/EMAG, etc.)
  • Point-2-Surface coupling suitable for all system simulation tools using ‘control nodes’ and physical quantities related to these nodes (e.g. modelling methods MBS, 1D-CFD pipeline models, general control models, FMI-for-co-simulation, etc.)

Standard interfaces for commercial codes

The MpCCI CouplingEnvironment supports most of the leading commercial codes for fluid-dynamics, structural analysis, electro-magnetic, and other disciplines:

Structural Analysis
  • Abaqus
  • ANSYS Mechanical
  • MSC.Nastran
  • MSC.Marc

Fluid Dynamics

  • ANSYS ICEPAK
  • ANSYS Fluent
  • FINE/Open
  • FINE/Turbo
  • OpenFOAM
  • STAR-CCM+
  • STAR-CD

Radiation

  • RadTherm / TaiTherm

System Modelling

  • Flowmaster
  • MATLAB
  • MSC.Adams
  • SIMPACK
  • FMI for co-simulation (under development)

Electro-Magnetics

  • ANSYS Emag
  • FLUX
  • JMAG

Programming Interface

  • Fully documented programming interface (C/C++, F77) to adapt further inhouse or research codes to MpCCI CouplingEnvironment.