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Finding Forces PUBLIC ACCESS

With Today's Analysis Software, Engineers can Quickly Solve For Multiple Physical Effects.

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Associate Editor

Mechanical Engineering 131(10), 33-36 (Oct 01, 2009) (6 pages) doi:10.1115/1.2009-OCT-3

This article explains how today's analysis software are helping engineers to quickly solve for more than one physical phenomenon at a time. Today's simulation software mirror real-life behavior. Engineers can now run multiple analyses within the same application or within loosely coupled applications. Other systems allow users to solve for more than one force at the same time. The capability to solve in tandem or to work with integrated systems greatly speeds the analysis process. Analysis advances also allow engineering firms to call upon the analysis software to design complex and never-before-seen products, to test for safety quicker than before, and to cut costs by perfecting designs earlier in the development process.

A physical force rarely acts alone. Because forces act in tandem on an object or assembly, simulation and analysis software of late has stepped up to allow engineers to solve for more than one physical phenomenon at a time. They can now run multiple analyses within the same application or within loosely coupled applications.

Some analysis packages loosely link fluid flow and finite element analysis capabilities, for example, to allow users to solve complex physical problems within the same, packaged software system. Other systems allow users to solve for more than one force at the same time.

Either way, before the advent of these types of software, simulation and analysis meant laboriously modeling and solving for one physical phenomenon at a time, not leaping between integrated software packages or modeling forces at once. Analysts would, for example, model and solve for structural integrity. Then they'd import their model into another system in order to solve for, say, electromagnetic compatibility or aerodynamic behavior.

Today's simulation software mirrors real-life behavior. In reality a component's behavior can depend on a number of physical phenomena combined with each other, said Bernt Nilsson, vice president of marketing at Comsol Ine. of Burlington, Mass. Comsol makes multiphysics software, which lets engineers conduct analyses of several influences acting on a system at the same time.

The capability to solve in tandem or to work with integrated systems greatly speeds the analysis process, Nilsson said.

And as analysis software capable of modeling the complexity of everyday interactions becomes ever more advanced it's making the leap from exclusive use byanalysis specialists to wider use by design engineers at work on early digital prototypes, he said.

Many engineering firms now call upon advanced analysis software to design complex structures. Here, a CFD analysis of a ship's propeller.

Grahic Jump LocationMany engineering firms now call upon advanced analysis software to design complex structures. Here, a CFD analysis of a ship's propeller.

In an effort to give design engineers a look at complexities of interactions and to give them a greater 'hand in analyzing their early designs, many developers are following the trend of pushing analysis software beyond the purview of trained specialists. They're now making an effort to reach the design engineers who more and more are calling upon analysis software to help with their initial designs, Nilsson said.

This month, for example, his company will be releasing Comsol Desktop, which allows users with all levels of physics modeling expertise to build and run simulations.

"Our target is the design engineer, not the specialist," Nilsson said. "Design engineers are running more and more multiphysics simulations every day because they need to add reality into their models."

The simulation software can model for multiple physical effects at once such as heat transfer and fluid flow. It can run electromagnetic, acoustical, and structural mechanics simulations, and a host of other physical analyses.

By running the simulations, design engineers can gauge how their design prototypes would operate in real-world conditions, Nilsson said.

Advanced simulation with design is becoming more accessible for both larger companies with analysts on staff and for individual design engineers because the soft-ware interfaces are being made more user friendly for the engineer who normally doesn't specialize in analysis and because costs of the software packages are coming down, Nilsson said.

Multiple physical simulations can now be run at once or in quick succession on a component to study the intera ction of physical effects.

Grahic Jump LocationMultiple physical simulations can now be run at once or in quick succession on a component to study the intera ction of physical effects.

But there's another factor at work that allows more and more engineering firms to turn to advanced analysis packages. The fact that such packages are now available for desktop COrriputers.

"Twenty years ago, you'd need a supercomputer to run ' these kind of advanced analyses," Nilsson said. "Each analysis method was developed in its own space, but you couldn't consider coupling them because there wasn't the software and hardware to do it.

"But as computation power grew, we can now solve these kinds of problems on the desktop," he added.

Analysis advances also ' allow engineering firms to call upon the analysis software to design complex and never- before-seen products, to test for safety quicker than before, and to cut costs by perfecting designs earlier in the development process.

Take Delta Marine of Istanbul, Turkey, which recently turned to simulation software from Ansys Ine. of Canonsburg, Pa., to optimize ships that transport cargo across the globe. Delta Marine's engineers use the same software package to look at both the ship's vibration and its structural soundness.

"Advanced simulation with design is becoming more accessible because the software interfaces are being made more user friendly for the engineer who normally doesn't specialize in analysis"

The shipmaker analyzes its designs to identify and correct troublesome vibration within the ship in order to comply with international standards and to ensure a long life for the vessel, said Dirim Sener, the company's planning director.

One of the most basic tasks that marine engineers face is eliminating undesirable vibration that can cause vital equipment to malfunction, he said. But an ocean-going bulk carrier, which can carry bulk cargo such as iron ore or coal weighing up to 180,000 tons, is continuously experiencing such vibrations. The engineers' goal is to reduce vibration to acceptable levels before the ship is even built.

Each ship also has a natural frequency, which is determined by the size of the structure, its shape, and the material used to build it. If overall vibration values do not meet international standards, expensive design changes will likely need to be made, Sener said.

Forcing frequencies also act upon a ship, which are usually generated by components operating at different frequencies from one another. As the propeller moves the water, for example, it exerts forces on the back of the ship. If the forces are large enough, they can cause vibration, particularly if they excite one of the structure's natural modes of vibration, he added.

Ocean-going merchant ships a re continually slammed by loads that create vibratio ns. Analysis software helps minimize these vibrations that can damage the ship.

Grahic Jump LocationOcean-going merchant ships a re continually slammed by loads that create vibratio ns. Analysis software helps minimize these vibrations that can damage the ship.

These phenomena must be understood through simulation and analysis.

Vibration in marine applications is especially complex to analyze because it involves the behavior of the structure as it passes through the water, Sener added. It's this fluidstructure interaction that can fatigue the hull's components and cause equipment to malfunction, he said. And this is where the tandem analysis comes into play.

Engineers can analyze for forcing frequencies, for natural vibrations, and for fluid-structure interaction using the same model. They use the analysis software, for example, to calculate pressures induced by the propeller on the ship as well as the loads generated on the propeller shaft.

By identifying and fixing vibration problems like this in the early stages of the design process, Delta Marine can make alterations such as adding pillars within the ship to stabilize the structure, strengthening structural components, or changing the propeller crankshaft's revolutions per minute or changing the number of blades in the propeller, Sener said.

After running simulations, engineers can update the model and determine the effect of the changes on vibration displacement and velocity.

"Simulation analysis gives our engineers insight into the complexities of these interactions," Sener said.

"Using simulation technology, our engineers try to correct problems by modifying the ship during the design stage-instead of discovering vibration problems after the ship is launched."

"It's virtually impossible to model complex processes on a theoretical basis on paper, according to one engineer who turned to analysis software instead."

Changes made after launch could cost m,illions of dollars, while changing the underwater form of a ship in the design stage can be done at almost no cost, he said.

"Engineers also have much more freedom when making design changes in the early stages," he said.

Delta Marine engineers also use the Ansys software to evaluate cargo tanks against worst-case load scenarios. They look at forces exerted by the tank's contents against the tank itself. For example, the design and construction of sulfur- and bitumen-carrying tankers is complicated by complexity of the cargo tanks, which could either be built independently or as part of an integrated structure, Sener said.

Engineers at SFX Technologies Ltd. used specialized analysis software to design a loudspeaker driver, above, that turns almost any surface into a speaker.

Grahic Jump LocationEngineers at SFX Technologies Ltd. used specialized analysis software to design a loudspeaker driver, above, that turns almost any surface into a speaker.

According to Nilsson of Comsol, the coupling-of-physical- forces analysis power allows today's designers to develop unique products.

Engineers at SFX Technologies Ltd. of Dunfermline, Scotland, for instance, used Comsol when designing a loudspeaker driver that uses virtually any surface-from a table top to walls, mirrors, dashboards, billboards, or even bus shelters-to produce high-quality sound, said Rob Habeshaw, acoustics engineer at the company.

When the Gel Audio transducer developed by SFX is placed against a surface, that surface becomes the loudspeaker, Habeshaw said.

The transducer's magnet and coil receive analog audio signals from an amplifier, while the' gel acts as an intermediary material that transfers the acoustic waves to the panel. The small transducer acts as a speaker without the need for a large speaker box, Habeshaw said.

"It's virtually impossible to model this complex process on a theoretical basis on paper," he said.

So the engineers naturally turned to analysis software. The company uses the multiphysics software from Comsol, which is linked to a special acoustics module from the same developer.

"The primary task of the modeling is to find the optimal assembly-the right amount of gel and the best way to attach it to the surface. And we do so by considering structural-acoustic interactions," Habeshaw said. "Too much gel makes the driver inefficient and nonresponsive; too little leads to sound distortions."

With the software's help, engineers created a design prototype within a month. Using uncoupled, separate simulation packages, engineers needed about three months to create the initial prototype, Habeshaw said. Such time savings, of course, can lead to significant cost reductions.

It's the potential for those time savings and cost reductions that will keep pushing advanced analysis capabilities to design engineers' desks. And without even knowing exactly who they have to thank, users of safe and unique products of the future will rejoice.

Copyright © 2009 by ASME
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