Challenge of multifidelity, multiphysics modeling

In conceptual and preliminary design, many aspects of mechanical products are most efficiently modeled for simulation using 0D/1D/rigid entities. In vehicle drivelines, for example, these include beams, bushings, bearings, point masses and the like. Combining these models with other product components best represented by 2D/3D CAE models can yield systems models that are highly revealing in design exploration activities such as parameter studies, design of experiments and optimization runs. But bringing multiple levels of fidelity together in a single model has conventionally been a labor-intensive manual process, severely limiting the number of design variants able to be studied this way when not precluding the practice altogether.

While mainstream CAE vendors are beginning to progress on this front, breakthrough technologies addressing the problem are available today that work with the industry’s leading solvers. A notable example is Comet Solutions, Inc.’s industry-specific SimApps™, based on its Abstract Engineering Model (AEM®) and Intelligent Templates. One customer, AAM, tells us that implementing Comet’s Driveline SimApp™ yielded an average 75% time reduction in each driveline NVH analysis iteration, allowing it to run many more iterations and make more design decisions, earlier. See our case study for the full story.

Multifidelity engineering model of automotive bumper design
Source: Comet Solutions

Another example is NPSS (Numerical Propulsion System Simulation), an object-oriented, multiphysics engineering design and simulation environment for development, collaboration and seamless integration of system models. Developed by the aerospace industry initially for modeling turbomachinery, rocket engines, environmental control systems, ducting, vapor cycles and other equipment and phenomena, NPSS incorporates both low/medium-fidelity systems simulation and high-fidelity component simulation. This variable-fidelity capability for simulating at selectively increasing levels of detail makes it feasible to carry out robust component simulation and also practical system simulation using a single, unified model.

NPSS modeling capabilities: component integration, discipline coupling, variable-fidelity analysis (zooming)
Source: NPSS Consortium

NPSS originated in the mid-1990s as a project led by NASA Glenn Research Center to develop a rapid simulation capability for engine design. A key objective was to help engine manufacturers develop engine performance models that could be shared with airframe manufacturers and integrated into vehicle system models far more rapidly and easily than with existing tools and methods.

The goal was to create a numerical “test cell” that would let engineers create complete engine simulations overnight on cost-effective computing platforms. “Using NPSS,” NASA Glenn said at the time, “engine designers will be able to analyze different parts of the engine simultaneously, perform different types of analysis simultaneously (e.g., aerodynamic and structural), and perform analysis in a more efficient and less costly manner.”

Summarizing the tool’s capability for variable-fidelity modeling and analysis, NASA Glenn explained that NPSS “allows the seamless integration of design tools at varying levels of dimensional fidelity across multiple technology disciplines. Zooming, originated in the conceptual phase of NPSS, is the coupling of analyses at various levels of detail.”

How does it work? NASA Glenn: “Engine models are assembled from a collection of interconnected components and controlled through the implementation of an appropriate solution algorithm. NPSS can call upon more sophisticated component models directly using the computer industry’s communication standard Common Object Request Broker Architecture (CORBA), interacting with external codes running on other computers distributed across a network.”

In March 2013 a contract was awarded to Southwest Research Institute (SwRI) to become manager of the NPSS Consortium, which took effect May 1. As consortium manager, SwRI provides overall project management and engineering support for maintenance and development activities as directed by the member companies. NPSS can be obtained either by the purchase of a commercial license or through consortium membership. For information, contact: David Ransom, Manager, Machinery Structural Dynamics Section, Mechanical Engineering Division, SwRI, tel. +1 210 522 5281,

For additional history and background, see “New Tool Offers Capability and Collaboration,” NASA HPCC InSights, Vol. 8.

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