Joined up thinking

After years of ‘separate-function’ demarcation in CFD and FEA, software designers have got together for systems to suit both the specialist and non-specialist.

Like many technical fields we are starting to see real convergence in computational fluid dynamics and finite element analysis. For a long time there has been considerable demarcation — with separate software for functions such as static analysis, dynamic analysis, large deformation and non-linear.

And anything including thermal/structural or fluid/structural interaction was still regarded as ‘stuff for rocket scientists’ and went by grand names such as multi-physics problems.

SolidWorks with Cosmos, Ansys with DesignSpace, and MSC with InCheck have been leading the ‘stress-checker’ charge since the mid-1990s where real analytical capability was made useable by design engineers with little or no specialist analytical knowledge, to give them a feel for the stressworthiness of their parts.

This trend has now moved on to include CFD, and establish true ‘up-front simulation’ over the more traditional post-failure’ analysis. Blue Ridge Numerics is a leading protagonist of upfront CFD. Its flagship product, CFdesign, is widely recognised for its associative integration with leading 3D MCAD systems.

However, MCAD integration alone does not make for an up-front design solution. Many CFD vendors have added CAD translators to their current product offerings, hoping to enlarge their market opportunity, only to discover the translator acts like a bridge leading to a foreign land.

Once the bridge is crossed the user finds he is looking at unfamiliar and sometimes confusing terrain and speaking a language that is not readily understood — and the ‘process’ suddenly comes to a grinding halt. The user hastily retreats to his comfortable MCAD environment and decides that testing some physical prototypes or tossing an IGES file to a CFD consultant is the better, safer way forward.

Blue Ridge’s approach to process integration, CFdesign, is based on a comprehensive sequence of steps. Allowing the engineer to use native MCAD geometry and conduct fully associative simulations is the first step.

Beyond this, the system uses dozens of intelligent algorithms and engineering input templates to remove complexity and automate the process.

Similarly, Pioneer Solutions’ Fluid Connection product provides support for Simulation-based design (SBD) and in-process CFD analysis in a Pro/ENGINEER design environment.

Based on Simmetrix’ Simulation Application Suite, it provides an ability to define an Abstract Analysis Model for CFD that is independent of the current design instance. The CFD analysis that problem definition is fully defined on this persistent Analysis Abstract Model. Fluid Connection includes definition of the CFD problem, automatic mesh generation with boundary layers, and automatic generation of run-ready data for CFD solution for AcuSolve from ACUSIM software.

This allows for definition of the CFD problem and methodology by experts and the use of this defined methodology as part of the product development process by non-experts.

The tricky part about making complex analysis techniques accessible to all is making sure that mistakes due to the lack of specialist knowledge are avoided. It is precisely because the Abstract Analysis Model is a methodology formulated by CFD experts, and the user is providing just the geometry, that the possibility of these kinds of mistakes are minimised.

Another recent milestone is the announcement by Fluent and Abacus of the availability of software for the simulation of fluid-structure interaction (FSI). Applications like flow-induced vibrations in structures and equipment, fan blade flutter, in-vivo vascular flows, microfluidics, and consumer products design and packaging are the main targets for this new capability.

The full set of modelling capabilities in Fluent 6.2 and Abacus 6.5 is available for use in coupled FSI simulations. This technology combines the benefits of full non-linear structural simulation from both Abacus products with the unique dynamic meshing capability in Fluent to account for the effect of structural motion or deformation on the fluid domain.

Comsol also provides solutions for multi-physics problems. Its corporate mission has always been to develop ‘real world’ engineering modelling software, and FEMLAB was developed in-house and released in 1998.

Comsol Multiphysics is a modelling package for the simulation of any physical process with partial differential equations (PDEs). It features state-of-the-art solvers that address complex problems quickly and accurately, while its intuitive structure is designed to provide ease of use and flexibility.

Most phenomena can be modelled through Multiphysics’ predefined modelling templates or application modes. Modifying these to specific applications is possible through the software’s equation-based modelling capabilities.

CD-adapco is moving in the same direction with its new products STARCCM+, STAR-Design and the STAR-CAD series. It claims that these products offer the simplest front door or gateway into the world’s most powerful suite of CFD products. Moves are afoot to improve and refine its customer’s CFD processes

The earliest sign of this is the company’s new surface wrapping functionality, which automatically cleans and de-features dirty or complex CAD geometry with minimal user interaction. It also claims to be the only CFD vendor to offer Full Insight, Full Spectrum CFD, able to tackle the full range of problems with a single consistent set of highly-usable tools, integrated into a customer’s CAE processes and workflows.

The one problem with all this choice is the many ways to access the technology.

This is being tackled head on by the Design and Simulation Council, led by Collaborative Product Development Associates (CPDA) and including the major software vendors and academic institutions.

The council was set up to examine the requirements for a standard framework employing common terminology, to integrate and optimise the diverse and divergent specialist activities currently fragmenting design efforts.

CAD frameworks should facilitate the bi-directional propagation of design changes with analysis to support active collaboration. Changes must be able to flow smoothly from the analysts to designers, and not just the other way, from CAD to CAE. To facilitate coupling that captures, extends, and distributes knowledge, an intermediate abstract representation of the model must support the full range of data requirements.

In particular, all relationships at the detailed level of the model such as files, features, attributes, and parameters must be specified and tracked.

As always with analysis and simulation ‘you pays your money and you takes your choice’.

Unlike a decade or so ago, today’s choice is vast and priced from low-cost through mid-range to high-end. All the software runs on ‘affordable’ hardware and it’s much more accessible to the non-rocket scientist than ever before.