Multiphysics simulations are becoming more complex, and take place earlier in the design cycle

Jean Thilmany, Senior Editor

Using multiphysics simulation software in tandem with design keeps engineers from following hypotheses that lead to dead ends. Of course, that significantly cuts development time, especially for complex products on which many physical forces come together: for instance, solid-state cooking ovens and the sonar on unmanned, undersea drones.

If the examples seem oddly specific, it’s because engineers who develop both types of applications described how their teams use Comsol multiphysics software at the Comsol Conference held online in October. The analysis software simulates how multiple, real-time physical forces would affect design.

Because Lauren Lagua works for a sonar team primarily funded by research and development dollars, “We don’t have a lot of time to spend on design and implementation,” she says. Lagua is an acoustic engineer with The Northrop Grumman Undersea Systems group. As a mechanical designer and acoustic analyst, she integrates tests equipment for undersea sonar systems and payloads for unmanned underwater vehicles (UUVs).

To make the most of funds, her team created a workflow for quick test-and-verify design. For transducers, their design method calls upon swift, but multiple rounds of prototyping and verifying. All the while, they must ensure the transducer can be rapidly manufactured. The transducers convert variants in pressure, brightness, or other physical qualities into an electrical signal.

Though Lagua’s team solves for electrical and acoustics tests early in the initial design stage, that doesn’t mean they’ve perfected design right off the bat. The process involves many design changes and modifications—or as Lagua puts it, “around and around we go.”

Of course, the models begin with design and CAD, but using Comsol for analysis in conjunction with design is the secret sauce that speeds the process, Lagua says. Because they simulate as they design, they get to the end result much faster than if they had to hand off the model to a dedicated analyst and await results.

“It allows us to quickly iterate on a design, to try out designs, to identify issues early on in the design phase and mitigate and fix them before they become bigger issues,” Lagua says.

“Say I’m building a transducer made of some type of material and I bond it to an electric substrate and see a bubble,” she says. “I can make a hypothesis about what failed. I then change the design, and test it with Comsol and compare it to our test events. We find issues with models and correct them quickly.”

“We’re able to design, prototype, test and verify a design sometimes in as little as a week,” she adds.

New materials and tank testing
Because it simulates how the material from which the object is made affects performance, the analysis software also helps engineers establish the material properties the transducer needs. They also use it to test prospective new materials, Lagua adds.

“We figure out if we have to change the design based on the prototype and maybe changing the materials is part of that,” she adds.

“The challenge is: materials vendors don’t always give you all their materials properties. And you need them,” Lagua says. “So, we use Comsol to model the materials.”

The researchers do this by plugging the materials properties they do have into the simulation and analysis software. They also find the materials they deem most similar to the one they are using and put those material properties in those as well.

“So, if I’m experimenting with a new polyurethane, it comes down to what we know about polyurethane in general. Then we look at the differences in data between the model and the test information and change and tweak the information we do have,” she says.

What is the test information she refers to?

Well, of course, the team needs real-world measurements to verify against and plug into the analysis software. These tests are also how they verify material properties against the information they have. They create model prototypes and study them, to study how that prototype would perform in the field.

Acoustical test events, as they’re called, take place at a specialized underseas testing facility that simulate open-water testing. The facility her team uses features a 50-foot-diameter, 300,0000-gallon tank lined with redwood for sound baffling. Onsite test and measurement equipment are placed on the prototype to gather immediate feedback and readings.

“It’s the closest an engineer gets to measuring how a device will act deep in the ocean—without actually taking the device deep in the ocean,” Lagua says.

“We take the results we get from the facility and bring them back into Comsol,” she says. “Then, with Comsol, you can run the same acoustic testing you do at an open-water tank,” she adds. “We have that information in our analysis software.

“Then we can and relate it back to our earlier test data and verify and tweak our model,” she adds. “We figure out if we have to change design or maybe change materials to optimize transducer performance.”

The engineers optimize transducer performance-based how that particular transducer’s end use.

“For example, we’ll optimize for acoustical performance: the highest level of sensitivity to capture the lowest amount of sound while having a large, broadband frequency coverage to hear over a very large range of frequencies,” Lagua says. “We’re really optimizing for multiple things in parallel.”

At the conference, Lagua shared one of the systems created through her group’s design iteration process: a µSAS (pronounced “micro-sas”) sonar to be affixed on UUVs. The micro-sas is small in size, weight, and power.

The interferometric synthetic aperture sonar produces high-quality, 3-D images, enables longer sorties, and higher area coverage rates for UUV missions, says Alan Lytle, vice president of undersea systems at Northrop Grumman. The sonar takes 2-D sas and 3-D bathymetric images.

The UUV vehicles carry six sonar systems, which can be preprogrammed for the needs of the mission, Lagua says.

“We have sonars on both sides of the vehicle so you can look at images from two different aspect ratios and interpret them in 3-D just as your eyes would,” she adds.

“Because of its very small scale we were constrained in size, weight and power for our system,” she says. “We wanted the best acoustics possible at the smallest scale while conserving as much energy as much as possible.”

The group tested their late prototypes by sending them down to take imagery of a ship that sank on the bay near their Maryland facility.

“In the 3-D image you can see the ship is in a big trough and the front is sticking out of a hole,” Lagua points out. “You wouldn’t be able to see that in 2-D.”

While she did not say exactly what sonar technology her team worked on, in February, Northrup Grumman announced that the company’s µSAS interferometric synthetic aperture sonar will be integrated onto L3Harris Technologies’ Iver4 UUVs.

The Iver4 UUV weighs 200-pounds, is nine inches in diameter and 99-inches long. Integration of synthetic aperture sonar on UUV of this diameter represents a significant step forward for the operational capability of small-class vehicles, according to Lytle.

The next-gen microwave oven
Then we veer to quite a different use for simulation in the early (and late) design stages. Illinois Tool Works (ITW) Food Equipment Group uses Comsol to analyze and simulate new heating methods for their solid-state ovens. The ovens, intended for commercial use, can cook a variety of foods, all at the same time and their different temperatures, says Chris Hopper, radio frequency systems engineer at ITW. He also spoke at the Comsol conference.

Solid stage ovens differ from convection microwaves, which use the same magnetron technology developed for radar in World War II. A “regular” microwave oven uses the open-loop magnetron system to heat foods.

But magnetron-based systems have many limitations, including low power and phase control, short lifetime, and high-voltage power supplies, Hopper says.

On the other hand, RF solid-state cooking features a closed-loop feedback system that can adapt to various loads and measure the food’s properties at any time during the cooking process, Hopper says.

“With solid-state, you can vary the power, measure what goes into the cavity and is coming out, and you can teach the oven how to intelligently respond over time to the feedback it gets,” he says.

“A magnetron can last from 12 to 18 months, but with solid-state power, the lifetime can be amplified for many years,” Hopper adds. “And the performance doesn’t degrade over time.”

“But before you start building, you want to investigate basic physical phenomena because we’re talking about a metal box with multiple phenomena,” he says.

Hopper’s team uses Comsol to iterate on the design using LiveLink for MatLab. The software allows them to synchronize their model with Comsol Multiphyics and define geometry, run multiphysics simulations, and optimize the model accordingly. For instance, they use simulation to study their model’s heating patterns.

“We look at what the presence of the food changes in terms of interference, hot and cold spots, and other qualities,” he says. “How does changing the phase affect the food itself?

“We don’t need it to be exact,” Hopper adds. “We’ll look at the accuracy once we’ve established that the simulation represents real-life experiments accurately,” he says.

“The culmination of our work is to develop algorithms,” Hopper says. “We can study hundreds of combinations of different phases in different sources. We can look at the data behind this and test and train models mainly worthy of further development for an algorithm.

“With simulations, we can phase out what wouldn’t work for outcomes we’re interested in,” Hopper says. “It saves us a lot of time because we don’t go down dead ends for algorithm development that may not work out.”

To study each phase and frequency combination separately would take weeks using testing equipment in a lab, he adds.

The virtual simulations also cuts labor costs in an unusual way, as the engineers run fewer experiments with actual oven prototypes and the food they cook.

To make those simulations available to product specialists, who don’t need or want to see the fine print, the ITW engineers created an application from the Comsol data. Product specialists download it, view it, and offer feedback based on their own experience, Hopper says.

“We have a chef here who is responsible for bringing value to our customers,” Hopper says. “There are certain questions he wants answered and, through the app, he doesn’t want to try it out in the kitchen many times. “He can look at temperature, airspeed, time and determine the parameters of the food he can cook and how the food will change as the result of those things.

In the end, many companies are learning that multiphysics simulation can be as important as model creation itself, says Bjorn Sjodin, Comsol vice president of product marketing. He calls the trend “the democratization of simulation.”

“More engineers are using simulation,” he says. And he expects the trend to continue.

The capability to simplify complex analysis and simulation by making application expands the reach beyond engineers.

Soon, a sales representative may be demonstrating oven phase and frequency to a potential customer. After all, “there’s an app for that.”

COMSOL
www.comsol.com