ISP Newsletter May 2023
The worldwide COVID-19 pandemic affected also the work of the Governing Board of ISP, due to several personal circumstances. Meanwhile, the Editorial Board managed to continue their work as good as possible, under the guidance of the Editor-in-Chief, Dr. Peter Wellens and the Editorial Office Manager, Martin van der Eijk. Although the number of annual ISP issues had to be reduced from four to two in 2021 and 2022 they managed to compose a number of interesting issues from the submitted articles in that period.
On January 31st, 2023 Dr. Wim Veldhyzen retired from his function as chairman of the Governing Board of the ISP Foundation after 18 years of service. The Governing Board as well as the staff of the Editorial Board thank Wim for the valuable service to the cause of ISP during such a long period.
Wim was succeeded as chairman by Do Ligtelijn, who was the secretary/treasurer of the Foundation ISP until then. The newly appointed sectretary is Dr. Ed van Daalen of MARIN.
ISP Volume 67, Issue 2 - 4
ISP Volume 67, issue 2 - 4 of 2020, is an issue that contains five articles on various topics. They range from ship design, construction of composite (concrete/steel) floating docks, seakeeping behaviour of a RIB to numerical prediction of cavitation erosion on propellers. Summaries, as well as the full articles can be found on https://content.iospress.com/journals/international-shipbuilding-progress/67/2-4.
Pneumatic transport of bulk materials in construction of composite floating docks
Investigations of pneumatic transport of bulk materials like cement, sand, gravel and crushed stones, used in the construction of composite (cement/steel) floating docks, have been carried out. The abrasiveness, wear of straight and curved sections of pipelines was investigated. The dependencies of the amount of wear on various factors were defined theoretically. This concerned abrasiveness and concentration of transported particles, flow rate, pipe diameter and wear resistance of its material, structural and operational features of the transport system, etc. Formulas for determining the maximum useful life of straight and curved sections of pipelines were obtained. The theoretical results have been confirmed experimentally.
How uncertainty influences decision-making effectiveness in conceptual ship design processes
Understanding how and why the development of conceptual ship designs sometimes becomes ineffective is essential for ship design firms. In many projects uncertainty influences the effectiveness of the decision-making process negatively. The objective of this study is to quantify the perception of uncertainty in conceptual ship design processes. In this article, a research model is proposed to study such a phenomenon. The research model is tested using multivariate regression analysis, building on a survey conducted among 23 shipping companies. The model suggests that 14% (R 2 ) of the variability in the effectiveness of decision-making processes in ship design can be explained by changes in the perception of uncertainty. Three interesting insights can be extracted from this research work for the ship design practitioners as to how to improve the effectiveness of their design processes: (i) put more effort into the contextual factors affecting the ship design process, (ii) improve the communication with vessel owners and other stakeholders, and (iii) improve the agility of the design process. This study contributes to research on uncertainty in ship design processes by: (a) proposing an investigative model, (b) developing and testing a survey instrument and (c) running a multivariate regression analysis to study the effect of perceived uncertainty on the effectiveness of decision-making processes in conceptual ship design.
Experimental and numerical assessment of vertical accelerations during bow re-entry of a RIB in irregular waves
This paper presents the comparison of a self-conducted towing tank experiment with the simulation results of a calibrated state-of-the-art strip-theory method and a first-principles numerical method. The experiment concerns a Rigid Inflatable Boat (RIB) in moderate-to-high irregular waves. These waves result in bow emersion events of the RIB. Bow re-entry induces vertical accelerations which, in reality, can lead to severe injuries and structural damage. State-of-the-art methods for predicting the vertical acceleration levels are based on assumptions, require calibration and are often limited in application range. It is demonstrated how the vertical acceleration as a function of time is found from a 3D numerical method based on the Navier–Stokes equations, employing the Volume of Fluid (VoF) method for the free surface, without any further assumptions or limitations. 2D+t strip theory methods like Fastship are based on the mechanics of wedges falling in water. The 3D numerical method that is part of the software ComFLOW is compared to previous research on falling wedges in 2D to investigate the effect of air and to find suitable grid distances for the 3D simulation of the RIB. The 3D RIB simulations are compared to Fastship and the experiment.
With respect to the experiment, the ComFLOW simulations show a slight underestimation of the levels of heave and pitch. The underestimation of Fastship is larger. The prediction of acceleration in ComFLOW is hardly different from the experiment and a significant improvement with respect to Fastship. ComFLOW is demonstrated to predict acceleration levels better than before, which creates opportunities for using it in seakeeping optimization and for the improvement of methods like Fastship. The properties of the RIB and the experiment are available as open data at Wellens (2020 ).
Practical numerical method for erosion risk prediction on ship propellers
It is important to make predictions of cavitation-induced erosion risk on ship propellers in the design phase. Since a cavitation tunnel test on a propeller model coated by soft paint, that is, a standard experimental method for evaluating erosion risk, is costly and time-consuming, numerical methods are necessary for erosion risk predictions. DES is made for cavitating flows around the propeller with a numerically modelled hull wake at the inflow. After achieving a converged solution, an erosion risk index is computed in each cell connecting to the blade surface and accumulated over a propeller rotation. Cavitation simulations are made for two propellers designed for a single-screw ship, of which one showed an erosion indication and the other showed no indication after cavitation tunnel tests with soft paint coating. Three index formulations are compared with the experiment result. The high value region of Index 1 based on the potential energy density of collapsing bubbles corresponds better with the eroded spot indicated by partial and complete paint removals in the experiment than those of the other indices. The maximum value of Index 1 for the non-eroded propeller is lower by more than an order of magnitude than that for the eroded one, whereas the maximum values of the other indices are of the same order of magnitude for both propellers. The validation of Index 1 is in agreement with the criterion that the maximum index needs to be below 1,000 J/m3 for erosion-free propeller designs. The design evolution based on the erosion risk index and propulsive efficiency from CFD shows that it can be a practical tool for a quantitative evaluation of blade surface erosion risk in the propeller design phase.
Ship design complexity, sources, drivers and factors: A literature review
Handling complexity in conceptual ship design processes requires a thorough understanding of complexity aspects in general. More than 100 scientific papers on the subject published since 1962 are, therefore, reviewed and discussed in this paper. The paper expands the understanding of complexity theory by reviewing the literature in the engineering domain. Different definitions of complexity, characteristics of complex systems, aspects of complexity in design, complexity sources, and its drivers are explored and discussed in detail. Furthermore, the findings are arranged into relevant complexity factors in ship design. Related complexity factors in ship design, are also discussed by use of examples from everyday ship design practices. This study is a theoretical elaboration to shed light on the current practice and future research direction in handling complexity in conceptual ship design processes to improve competitiveness.
ISP issues in 2021 and 2022
Volume 68 (2021) consists of two issues (1-2 and 3-4). Volume 69 consists also of two issues (1 and 2). These issues will be discussed in the next ISP newsletters.
Next meeting of the Editorial Board
No new meeting of the Editorial Board has been scheduled yet. It is the intention to resume the Editorial Board meetings on a regular basis as soon as possible.
Upcoming conferences, meetings and training courses
Overviews of relevant conferences, exhibitions, meetings and training courses can be found on:
Published: 2023-06-08 | Tagged: isp-news, isp-nieuws, uitgelicht