At last year’s Simcenter conference in Prague, the keynote speaker Nancy Rademaker used cassette tapes as one example of the ‘old normal’ – something which was the standard once but has now been replaced by the ‘new normal’, streaming. Music, like many things, is now digital. This is the new normal, and younger generations have no interest in or understanding of the old normal. While I am sure most of us can accept this for music, Nancy also challenged us whether we were all ready for the new normal in every aspect of life, or are our ideas and practices still based on the old normal?
From cassettes to digital streaming: old normal to new normal, giving more choice and ease of use
We see this clash between the old and new normal on a regular basis in marine design. While the use of CAD models instead of line drawings is now standard practice in vessel design, there is continued insistence and reliance on confirming each design suitability via towing tank testing of a physical scaled model. The limitations of towing tanks are well known: translating model-scale measurements to full-scale vessels is open to many uncertainties and requires the use of empirical scaling formulae. Also, due to the differences in Reynolds number, it is difficult to study interactions between key components accurately such as propellers, appendages, and hulls. Dependence on this limited, expensive and time-consuming method is holding the industry back from innovating in design and efficiency. And this resistance to switching to digital simulation at full scale as the new normal in marine design is even more interesting when we consider that the marine industry can also be a world leader in innovation and new technology. For example, Maersk is investing in using blockchain in the global supply chain, aiming to promote more efficient and secure global trade.
In a time which is becoming increasingly critical for the industry to meet stringent environmental regulations, it seems that everyone accepts that things need to change but no one is willing to make the decision to do so. Other industries have been quicker to adopt changes, for example in the aerospace industry where CFD models are now used alongside wind tunnel tests, speeding up certification programs, and reducing the overall cost. Why is it that these two industries have different attitudes to adopting new normals? How can the same simulation technology be accepted in an industry whose main cargo is human lives, with millions traveling daily, yet is deemed not sufficiently validated to be trusted with the design of a cargo vessel?
I believe it is the time to move to the new normal: designs analyzed using CFD simulation, at full scale. The additional benefit of this approach is that multiple designs can be tested under realistic operating conditions, such as wind, waves, and self-maneuvering, all of which are again not possible in a towing tank. While I call this the new normal, it is not a new method, but a well-established, well-validated tool with many proven results and successes in other industries as well as marine. The 2017 Lloyd’s Register workshop on full-scale simulation proved that when used properly CFD can accurately match sea trial data, while at the recent Simcenter conference Wärtsilä propulsion presented results showing that full-scale CFD simulation on a propulsor proved it was suitable for use when previous towing tank tests had defined it as unsuitable.
From scale model towing tank tests to full-scale CFD simulations: old normal to new normal, giving a greater understanding of vessel dynamics under realistic conditions
Adding to these examples from industry, this new white paper authored by Professor Milovan Peric takes a measured look at the use of full-scale CFD simulation, aiming to allay some common reservations about this for the marine industry. Based on his many years of experience with marine simulations, Professor Peric argues that full-scale CFD increases the value that simulation brings to marine design, by increasing realism and enabling multiple designs to be rapidly evaluated.
Here is my vision for the new normal in marine design: using an agile digital twin of a vessel which includes full-scale CAD, full-scale simulation data and sea trial data (if available) and covers all aspects of vessel performance, accessible in real time to all stakeholders. With this in place, you can quickly test multiple ‘what if’ scenarios: what is the impact on safety and performance of the damage or adverse weather conditions? What if we re-design part of the hull? What if we re-purpose the vessel to alternative routes? What if we change to a new engine? If this sounds too far-fetched to you, consider: even ten years ago would you have predicted that you would stream music from the cloud? And yet, that is the reality today. The digital twin must become the new normal in marine design, the only question is when we will come to accept it as standard.
Professor Peric comes to the same conclusion in the white paper:
“Many experienced users in the maritime sector are already routinely and successfully applying CFD simulations under full-scale conditions. For those who are still hesitating, it is time to start gathering experience since the trend is clear. Using Simcenter STAR-CCM+ makes it possible to meet the goal of conducting full-scale analysis of complete systems under realistic operating conditions by creating a digital twin of the real system.”