CFD reduces diving rebreather’s resource consumption & operating costs

COMPUTATIONAL FLUID DYNAMICS (CFD) reduces diving rebreather’s resource consumption & operating costs

M4R Project: COBRA diving rebreather system – Breath-by-breath CFD simulation & analysis of COBRA rebreather fluid dynamics and oxygen consumption

JFD is a world-leading underwater capability provider, serving the commercial and defence markets with innovative diving, submarine and hyperbaric rescue, technical solutions and services.

Facing an issue with a component in a diving rebreather system which wasn’t operating as expected, JFD turned to TÜV SÜD’s computational fluid dynamics (CFD) consultancy. Our team provided a successful solution which offers JFD’s customers reduced resource consumption and operational costs without compromising safety.

Challenge

Callum Crawford, Head of Innovation at JFD is responsible for research and development (R&D) activities across the company. This involves engaging with customers and end users to fully understand their requirements and ensure that product specifications reflect their needs. Callum aims to ensure JFD’s products remain “in a market-leading position in terms of both capability delivered and value for money, through utilising technologies and engaging specialist engineering services to continually refine and enhance our design solutions.”

JFD Cobra Rebreather CFD Graphic

In their COBRA rebreather system, JFD use a mixture of helium and oxygen (known as Heliox). As a diver descends to deeper depths the partial pressures of the breathing gas mixture change. Unfortunately, the breathing gas injection lee-jet nozzle within the rebreather system wasn’t operating as expected based on the information in the manufacturer’s datasheets.

JFD decided to partner with us for several reasons including reputation and experience, funding opportunities and location. Callum was also confident that our CFD team would be able to find a solution:

“We were aware of TÜV SÜD’s specialist simulation and modelling capabilities and felt confident that through the wide range of experience and disciplines within their engineering analysis team, a solution to this challenge would be identified.”

The vast majority of the work was completed remotely but being based in Aberdeen, JFD found our Glasgow location convenient as it meant the introductory sessions and subsequent face-to-face meetings were easier to arrange.

TÜV SÜD Solution

The component in question was a bought in item which wasn’t performing as predicted by the manufacturer. However, the manufacturer wasn’t willing to divulge the inner workings, and was unable to help identify why the performance didn’t align with their published data. To address this, TÜV SÜD recommended that JFD engage a 3rd party 3D scanning company which successfully reverse engineered the component based on data obtained using a CT scanner.

This provided a 3D CAD model which we were able to start building a CFD simulation around. We combined this with measured data that JFD already had to tune its results to reflect the measured real-world performance. This provided a simulation tool which was able to predict the behaviour of the component. Understandably, JFD didn’t want to have to run the simulation every time a customer wanted to plan a dive, so we further evaluated the model and generated a spread of results across a range of different conditions.

Based on these results, we derived a simple formula which could be used in place of the manufacturer’s recommended calculation method. With this formula, JFD were able to publish a revised set of customer guidance documents, which included a far more accurate calculation for Heliox gas mixtures across an appropriate range of depths. This new formula has helped to reduce the required volume of this finite resource and lower operational costs with no negative impact on safety.

Client Benefits

Callum is delighted with the positive impact that TÜV SÜD’s CFD services have had on their product and, in particular, the benefits that JFD have been able to pass onto their customers:

“The primary benefit realised from this project is operational, and is passed directly to our customers who are now able to operate their dive systems at a higher level of resolution, and can reduce their operating costs by more accurately calculating the gas consumption for a given dive depth. This provides a more attractive and cost-effective emergency bailout system, and allows them to consume less Helium (a finite element) for each dive.”

Based on their experience, JFD wholeheartedly endorse our CFD consultancy services with Callum commenting:

“I would recommend TÜV SÜD as their approach is thorough, detailed and sympathetic to both project and customer requirements. It was a pleasure working with the TÜV SÜD team as they were dedicated and professional throughout, and they clearly had a real desire to understand and solve the problem at hand.

They say a problem shared is a problem halved, and in the context of partnering with TÜV SÜD, I feel that adage is particularly apt.”

Dr Sandy Black, Senior CFD Consultant at TÜV SÜD, said:

“Working on this project was an interesting challenge from start to finish. I’m pleased that we were able to create a powerful simulation tool capable of predicting the component's behaviour across various conditions and then develop the formula. It’s always satisfying when we can help a client achieve reduced resource consumption, lowered operational costs, and uncompromised safety. A project truly worth every ounce of effort.”