CFD software pays for itself in record time

By reducing its development time to just a few days from a year, Viasys Healthcare has managed to save several hundred thousand dollars in development costs.

Like most engineers, pneumatic specialist Steve Han is accustomed to the hard slog that accompanies the design of any new product.

Realising that small improvements in product performance are usually only accomplished through many weeks or even months of detailed engineering analysis, Han's employer, Viasys Healthcare, recently purchased Star-Works.

Expectations were high that incorporating Star-Works into Viasys's already efficient design process would deliver significant savings in design cost and result in a faster time to market.

Even so, Han's management were shocked when, just a few days after installing Star-Works, he delivered with guidance from Steve Duquette, Director of Research and Development, a revolutionary new ventilator device design; something that would normally take upwards of a year in design effort.

In Han's own words: "Within three days Star-Works had paid for itself".

Viasys Healthcare, is a global market leader in health care technology.

The Respiratory Care Division delivers a comprehensive line of respiratory products serving the smallest neonate to the largest adult patient.

Han and his colleagues were working on the redesign of an infant CPAP ventilator device.

Continuous positive airway pressure (or CPAP) is a method of respiratory ventilation, used in the treatment of apnea, a condition in which a patient's natural external breathing suddenly stops due to a self imposed (but involuntary) obstruction to their airway.

In adult patients the most common manifestation is sleep apnea, an extreme form of snoring, during which the soft tissue at the back of the patient's throat becomes relaxed, collapsing the airway and blocking the passage of air, resulting in a temporary interruption to the patient's breathing.

The CPAP unit in question is used in the care of small infants through to premature babies (although not for those in a critical condition).

Apnea is relatively frequent occurrence in newborn infants due to immaturity of the respiratory system.

While in adults the most likely symptom of apnea is serious fatigue, the consequences in small infants are potentially lethal - any breathing interruption over 20 seconds has the potential to cause serious damage or even death.

The CPAP machine works by delivering a constant stream of compressed air via a mask that fits over the patients nose (or nose and mouth).

The slight positive pressure delivered to the mask acts to splint the patient's airway, preventing obstruction and allowing the patient to breathe freely.

Maintaining the constant pressure prescribed for each patient is critical; if the pressure at the mask is too high then it opposes the patient's natural exhalation and increases the so called "work of breathing".

Han's analysis concentrated on the redesign of the jet-venturi, the critical component in regulating the patient pressure.

The orifice of the venturi measures just 0.04in, making physical testing of prototypes very difficult due to the tight manufacturing tolerances involved and the possibility that small defects could significantly influence the results of the test program.

Using Star-Works, Han and his colleagues were rapidly able to evaluate multiple design changes from their desktop computers.

All of the analysis was performed from within the SolidWorks environment.

As all of the CFD functionality is accessible through additional menus in the SolidWorks GUI, Han was able to begin using Star-Works for serious design analysis within a few hours of first installing.

"The whole project took about three days, with about a day to get familiar with the software", says Han.

The improvements were both immediate and impressive.

"It was difficult to believe at first", says Han, "almost every design change resulted in a significant improvement".

"Incredibly, within three days we had reduced the supply pressure required to the unit by 48%".

Part of the reason that the analysis was able to proceed so rapidly is that the Star-Works CFD results are linked directly to the CAD geometry (a process called associativity).

After any modification in the CAD model the simulation results can be updated almost instantly by clicking the "update solution" button, allowing the rapid and thorough investigation of the design space.

Excited by the results, Viasys management immediately approved the funding for the construction of a prototype, the testing of which immediately confirmed the improvements predicted by the CFD analysis.

"We were pretty amazed", says Han", the results of the first prototype were within a few percent of those predicted by Star-Works".

This significant reduction in supply pressure has a number of positive ramifications; not least of which is a significant increase in the saleability of the product.

"Saving 48% of the supply pressure allowed us to use the CPAP unit with the majority of our patient ventilators, rather than just two 'critical care' ventilators as had been the case previously", says Han.

"The reduction in cost achieved in doing this alone, has the potential to treble sales of the product".

Because a much lower supply pressure is required the new design is also around 30% more efficient than previous designs: "Because the new CPAP design uses less energy than its predecessor it is both cost effective to run and more environmentally friendly".

By reducing the development time to just a few days from a year, Viasys Healthcare has managed to save several hundred thousand dollars in development costs.

At the time of writing, the new ventilator device is undergoing patient testing and will be on the market shortly.

"In three days we were able to reduce the required upstream pressure by 48%".

"This level of improvement previously took approximately 1 year to achieve".

"Star-Works saved us $250,000 in physical testing alone, and paid for itself in three days".

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