Flexible Structures in Aerodynamics and Machinery Design

When a surrounding fluid exerts pressure on a flexible structure this structure deforms- which leads to changes in the flow field of the fluid. These so-called fluid-structure interactions appear in different application areas: the most common examples are wings, spoilers and other deformable parts of racing or everyday cars or the flutter of aircraft wings. Furthermore, this effect can be observed in many machines, especially where moving parts or light, very deformable walls are involved. Typical examples are valves, pumps or hydraulic engine mounts. MpCCI has been used successfully to solve different applications from all of these areas:

© Photo Fraunhofer SCAI

Optimization of a flexible spoiler in automotive racing

Wings and spoilers of racing cars deform considerably under the fluid forces, thereby influencing the CFD solution. To find optimal layouts of spoilers, huge CFD models of full racing cars have to be coupled to FEA models of the deformable parts. Only a coupled simulation can predict the actual lift and drag coefficients for different spoiler layouts.

  • Using MpCCI to optimise Automotive Aerodynamics [PDF, ]
    (Best Practice Case Flyer in preparation)
© Photo Fraunhofer SCAI

Aero-elastic benchmark cases using coupled fluid-structure code combinations

Using MpCCI to couple MSC.Nastran and Ansys Fluent, different benchmarks from the area of aero-elasticity, most importantly the HIRENASD benchmark, have been simulated. The results of the coupled FSI simulations are compared to experimental measurements.

© Photo Fraunhofer SCAI

Numerical Simulation of Fluid-Structure Interaction in the Design Process for a New Axial Hydraulic Pump

With the help of numerical simulation a new high-pressure hydraulic axial pump has been developed at Gdansk University. To find an optimal layout of the different pump chambers, coupled FSI simulations, using Abaqus, Fluent and MpCCI, were used.

© Photo 2014 by University of Duisburg-Essen

An enhanced 1-way coupling method to predict elastic global girder loads

To predict global hull girder loads of sea-going vessels the structural elasticity has to be taken into account. A one-way-mapping of the CFD external loads at the hull surface to a FEA 3d model of the hull computing the structural response has been realized by employing MpCCI.

FSI Features in MpCCI

  • Different coupling schemes are available:
  • A globally explicit coupling method: the coupled fields are exchanged only once per coupling step. This approach 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 before advancing to the next coupling step. This approach is applicable to problems with strong physics coupling.

  • Each coupling scheme can be adapted to the application:
  • Optimization of the implicit iterative coupling with an adaptive stopping criteria
  • Explicit coupling method with flexible time coupling management
  • Application with highly coupled time: time steps are matching, or one code acting as master code and defining the time step size
  • Application with different solver integration on time scale: non matching time steps

  • Analysis of a stationary application by coupling two steady state simulations
  • Quasi-transient approach by coupling a steady state and transient simulations
  • Ramping and Relaxation methods to stabilize coupled simulations. The relaxation factor can be computed automatically according to Aitken’s method.
  • Extrapolation methods can be used to handle “orphaned areas” (local mesh regions without matching regions on the partner mesh)
  • Additional to the CFD code’s morphing and remeshing capabilities the MpCCI Mesh Morpher can be used to handle the deformation of the CFD mesh, e.g. for coupled OpenFOAM simulations.
  • MpCCI FSIMapper can be used to check the geometries and the mapped CFD results before starting a coupled simulation.

Realization of new Methods and Solutions within R&D Projects

  • Although FSI is already an established solution method for many engineering applications there are still many open issues which we would like to evaluate and solve in more strategic and long-term (3rd party funded) R&D projects:
  • Extending MpCCI to further simulation tools and deploying it to new and challenging application domains
  • Working on open and generic benchmarks and validation cases
  • Enhancing stability and accuracy for highly dynamic fluid-structure interactions
  • More sophisticated and automated coupling control mechanisms

Our FSI Service Offer

Based on our long-term experience in FSI we can provide you with dedicated knowledge and services:

  • Integration of commercial or inhouse codes into the MpCCI tools
  • Integration of MpCCI tools into customer’s CAE workflow
  • Adjusting MpCCI to customer’s specific requirements
  • Realization of a first FSI concept for your specific application setup – from separated standalone models towards coupled fluid-structure-cases
  • Preparation of the geometrical connection between the CFD and FEA meshes
  • Defining appropriate mesh motion conditions for the CFD simulation code
  • Testing and evaluating different coupling methods for your specific problem: iterative or explicit coupling, steady state or transient simulations
  • Integrating coupled FSI jobs in your dedicated HPC systems

MpCCI CouplingEnvironment

The MpCCI CouplingEnvironment offers flexible solutions for multiphysical simulations. The combinable simulation codes for this application area are shown in the following table:

Discipline

Codes

Fluid

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

STRUCTURE

  • Abaqus
  • ANSYS Mech.
  • MD Nastran / MSC.Nastran
  • MSC.Marc

 

The supported quantities in this context are:

 

Quantities

Mechanical

  • pressure
  • force
  • nodal coordinates


List of all supported codes and quantities


MpCCI FSIMapper

The MpCCI FSIMapper maps simulation results from a source to a target mesh. The following two tables list the supported source and target file formats for this application area.

 

Source Formats

Quantities

CFD

  • ANSYS Fluent (.cas, .dat)
  • ANSYS CFX (.csv)
  • EnSight Gold (.case)
  • FINE/Turbo (.cgns)
  • STAR-CCM+ (.case)
  • OpenFOAM (.case)
  • FloEFD (.efdfea)

pressure

 

 

Target Formats

Target Analyses

FEM

  • Abaqus
  • ANSYS Mech.
  • Nastran

deformation

stress

fatigue

NVH


List of additionally supported source and target file formats