Special issue of Ship Technology Research on ‘Simulation-Driven Design of Maritime Systems’ in Honor of Prof. Dr.-Ing. Dr. h. c. Horst Nowacki

Introduction to Professor Horst Nowacki

Em. Professor Horst Nowacki was born on 9 February 1933 in Berlin. He is a graduate of the Technical University of Berlin, receiving his Diploma of Engineering Degree in Naval Architecture/Ship Technology in 1958 and his Doctor of Engineering Degree with a thesis on ‘Wake and Thrust Deduction Calculations for Shiplike Bodies by Means of Potential Theory’ in 1963. Between 1958 and 59 he worked as a research engineer at the Ship Model Basin for Inland Ships in Duisburg and was Scientific Assistant at the Chair of Ship Theory of the Technical University of Berlin from 1959 to 1964.

Having received his PhD, he moved to the University of Michigan, Dept. of Naval Architecture and Marine Engineering, Ann Arbor, USA, where he lived with his wife Elfie and sons from 1964 to 1974. He became first Assistant Professor of Ship Design and was later on promoted to Associate and finally to Full Professor before returning to Germany in 1974. He was appointed Full Professor and head of the newly established Section of Ship Design at the Technical University of Berlin, Department of Ship and Ocean Technology, where he served until his retirement in 1998. Starting in 2001 he was Visiting Scholar of the Max Planck Institute for the History of Science in Berlin.

The areas of his educational and research work cover the wider field of Naval Architecture, Information Technology and in later years the history of Ship Theory. His work refers to Ship design, Computer-Aided Design and Optimization, Computational Fluid Dynamics, Theoretical and Numerical Ship Hydrodynamics, Ship Dynamics and Hydroelasticity, Geometric Modeling, CAD/CAM, Information Technology, Product Modeling, Product Data Engineering, History of Ship Theory.

He was a member of the German Society of Ship Technology (STG) and Fellow of the Society of Naval Architects and Marine Engineers (SNAME).

He was an organizer of a long series of post-graduate, continuing education courses and workshops on Computer Aided Ship Design and Ship Design Optimisation in the USA, Germany, UK, China, Poland, Indonesia, Norway for over 40 years.

For his work, Professor Nowacki received a series of awards, distinctions and fellowships, namely the Distinguished Teaching Award by the University of Michigan, Ann Arbor (1969), Professor for CAD/CAM, Northwestern Polytechnical University, Xian, V.R. China (1985), Visiting Fellow of the Japanese Society for the Promotion of Science (1992), Honorary Commodore, Quarterdeck Society, University of Michigan, Ann Arbor (1993), Honorary membership of the ProSTEP Association, Darmstadt (1998), Silver Commemorative Award of the Shipbuilding Society (STG), Berlin (1999), Visiting scholar of the Max Planck Institute for the History of Science, Berlin, Captain Ralph R. and Florence M. Peachman Lectureship, University of Michigan, Ann Arbor (2007). Furthermore, he received two additional prestigious distinctions, namely the honorary doctoral degree of Dr. h.c. of the National Technical University of Athens, Greece (1996), and the Honorary Membership Award of the Technical University of Berlin (1998).

His publication work, starting in 1960, includes more than 200 scientific contributions published in scientific and professional journals, conference proceedings, monographs and technical reports. He was editor or co-editor of seven books. A short appraisal of his core work follows.

The main contribution of Horst Nowacki to Naval Architecture is the introduction of Computer-Aided Ship Design (CASD) along with the parametric ship design and optimization in the late 1960s through his presented work on the ‘Tanker preliminary design – an optimization problem with constraints’ at the Annual Meeting of the Society of Naval Architects and Marine Engineers (SNAME) (Nowacki et al. 1970). This pioneering work was later on complemented by the development of Syntheses Models for other cargo ship types, including high-speed SWATH like forms (Papanikolaou et al. 1989). The CASD work of Horst Nowacki was widely disseminated by the organization of large series of post-graduate courses and seminars in many places around the world.

The contributions of Horst Nowacki to ship hydrodynamics started in the early 1960s in potential theory and numerical ship hydrodynamics through his at the time highly innovative PhD work on a 3D potential theory panel method to estimate the wake and thrust deduction of shiplike forms (Nowacki 1963). This work was a predecessor of the shortly after published landmark paper by Hess & Smith on a 3D potential theory panel method for arbitrarily shaped 3D bodies (Hess and Smith 1964). In the late 1970s, he presented at the 13th ONR Symposium in Tokyo jointly with his former student Apostolos Papanikolaou an innovative ‘Second-order Theory for Oscillating Arbitrarily shaped bodies in waves’ (Papanikolaou and Nowacki 1980). This was a multi-cited landmark paper for the nonlinear seakeeping theories in the years to come. In the late 1990s, Professor Nowacki jointly presented the first realization of fully-parametric modelling and hydrodynamic optimization of ship hull forms together with his former student Stefan Harries at the 10th International Conference on Computer Applications in Shipbuilding (ICCAS 99), Massachusetts Institute of Technology. The paper entitled ‘Form Parameter Approach to the Design of Fair Hull Shapes’ (Harries and Nowacki 1999) spearheaded the approach of simulation-driven design now followed by many model basins, shipyards and design offices.

After his retirement, in more recent years, Horst Nowacki dealt intensively with the history of ship theory and greatly contributed to scientific evidence for important past discoveries, hidden in history and not mentioned in traditional scientific treatises. Among them, the most important rediscovery was his thorough review of the resurrected work of the great Greek mathematician Archimedes on ship theory. While it is well established that Archimedes introduced the notion of buoyancy of floating bodies, it was less established, or rather ignored completely, that Archimedes had also introduced the basic laws of the stability of floating bodies and also introduced the notion of moments/couple of forces (Nowacki, 2002). Additional discoveries in the field of ship theory may be found in his review of the works of Leonard Euler (Nowacki 2006). Last, but not least, Horst Nowacki was the author of the most comprehensive and competent State of the Art reviews of Ship Design in recent years (Nowacki 2010, 2016, 2019).

Throughout his career Professor Nowacki inspired many colleagues and students, supporting their work, making friends, taking interest in their scientific achievements, their careers and their lives (https://www.hn90.de/birthday-wishes-and-anecdotes/). Professor Horst Nowacki passed away peacefully on 5 June 2023, in Bremen/Germany, surrounded by his loved ones (https://www.hn90.de/obituary/). Even though he cannot hold this Special Issue in honour of his legacy in his hands, we know that he followed the work leading up to its publication keenly and with the scientific interest that had characterized him throughout his life.

Overview of contributions

This Special Issue of STR contains 10 contributions by former students and colleagues of Horst Nowacki’s, covering latest research on different fields of ship design, ship hydrodynamics and the history of naval architecture. In the following overview, the abstracts and the most notable findings of each contribution are presented.

Ship Hull Optimization – Past, Present, Prospects by Volker Bertram DNV, Justus Heinmann, DNV, Karsten Hochkirch, DNV. The paper surveys the development of practical ship hull optimization over more than five decades and trends to extrapolate to (likely) future applications. The paper looks at individual elements of hull optimization, such as geometric model, hydrodynamic model, optimization algorithms, and objective functions (and constraints). For all elements, the discussion sheds light at further room for improvement or further R&D efforts.

On Parametric Modeling, Digital Siblings and Ship Design Optimisation by Apostolos Papanikolaou (National Technical University of Athens). Ship design is inherently coupled with design optimization, namely the selection of the best solution out of many feasible ones. In traditional naval architecture, optimization means taking the best out of two to three feasible solutions and it is up to the designers to decide based on the design specification and their experience, about the decision criterion (or criteria) that may be not rationally defined. Of course, the space of feasible design solutions is huge, the relevant assessment criteria are plenty and complex, as are the many possible design constraints. However, after all, the assessment procedure should be rational and not intuitive, thus according to the contemporary state of the art. All this calls for a step change of the design process in naval architecture. The parametric modelling of ship design by use of digital siblings and the multi-objective optimization of ship design, as they have been elaborated within the recent Horizon 2020 project HOLISHIP project (2016–20), are summarized and reviewed in this contribution, showing the way ahead in response to present and future challenges of the maritime industry.

Simulation-driven Design of a fast Monohull by Stefan Harries, Osama Ahmed, Sebastian Uharek (FRIENDSHIP SYSTEMS). A fast monohull has been designed and optimized, using CAESES for parametric modelling and optimization coupled to STAR-CCM + for viscous free surface RANS simulations. The boat is a 9.5ton pilot boat, featuring two tunnelled propellers, conventional shafts with I-brackets and spate rudders. The optimizations were undertaken for thrust at design speed of 27.5kn, a condition at the lower end of planing. The boat was free to trim and rise, utilizing an overset grid for high resolution and acceptable turn-around time per variant. Propulsion was taken into account via an actuator disc, balancing resistance and thrust for given propeller open-water characteristics. The geometry of the bare hull and the tunnel were varied during the optimizations, using fully-parametric models within CAESES. A comparison of numerical and experimental data was undertaken in order to ensure accuracy of the CFD simulations. The experiments were conducted with the high-speed carriage at TU Berlin’s towing tank, using a 3.5 m fully-appended self-propelled model. The optimizations undertaken comprised Design-of-Experiments, deterministic search strategies, surrogates and various local and global strategies. Substantial improvements could be identified with variants being tangibly more efficient than a representative baseline. The paper discusses the parametric model, the CFD set-up for accurate yet reasonably fast simulations and the various optimization approaches along with selected results.

Design-Space Dimensionality Reduction in Global Optimization of Functional Surfaces: Recent Developments and Way Forward by Matteo Diez and Andrea Serani (CNR). In shape optimization of complex industrial products (such as, but not limited to, hull forms, rudder and appendages, propellers), there exists an inherent similarity between global optimization (GO) and uncertainty quantification (UQ): they rely on an extensive exploration of the design and operational spaces, respectively; often, they need local refinements to ensure accurate identification of optimal solutions or probability density regions (such as distribution tails), respectively; they both are dramatically affected by the curse of dimensionality as GO and UQ algorithms’ complexity and especially computational cost rapidly increase with the problem dimension. Therefore, there exists a natural ground for transferring dimensionality reduction methods for UQ to GO. These enable the efficient exploration of large design spaces in shape optimization, which, in turn, enable global optimization (possibly in a multidisciplinary and stochastic setting). The paper reviews and discusses recent techniques for design-space dimensionality reduction in shape optimization, based on the Karhunen-Loeve expansion (equivalent to proper orthogonal decomposition and, at the discrete level, principal component analysis). An example is shown and discussed for the hydrodynamic optimization of a ship hull.

Practical ship afterbody optimization by multifidelity techniques by Hoyte C. Raven, Joy Klinkenberg (Maritime Research Institute Netherlands – MARIN). This paper discusses multifidelity methods for CFD-based optimization of ship afterbody designs; aimed at a fast application to a variety of practical cases. Surrogate-based global optimization is used, using a multi-objective genetic algorithm. The surrogates are derived by combining few high-fidelity computations, by free-surface RANS codes, with many low-fidelity computations. For rather slender vessels for which the wave resistance variations over the design space are dominant, a free-surface potential flow code is found very effective as a low-fidelity solver, permitting a large reduction of the number of RANS computations and the associated cost. Examples are shown for model 5415 and a fast displacement vessel. For cases with variation in both viscous and wave resistance, an alternative method is used combining coarse and fine-grid RANS computations; the coarse-grid ones being about 20 times cheaper. Application of this coarse/fine grid multifidelity optimization to a containership and a motor yacht shows its effectivity.

Interactive Modeling of Fair Ship Hulls With B-Spline Surfaces Avoiding Gaps and Discontinuities by Lothar Birk (University of New Orleans): In most of today's three-dimensional modelling systems hull surfaces are represented as parametric B-spline or NURBS surfaces (NURBS stands for Non-Uniform Rational B-Spline). The shape of a surface is controlled by a mesh of vertices. In traditional NURBS surfaces this mesh is regular with constant numbers of vertices in each parametric direction. This restriction complicates the modelling of complex features like bulbous bows, stern bulbs, transoms and others features. Several surface patches may be used to overcome the perceived limitations of a regular control mesh, but it raises the challenge to keep the patches properly aligned at the seams. Especially in smaller companies, hull design is just one of many responsibilities for the naval architect. Lack of practice, inexperience or sometimes just lack of time can lead to hull representations which feature undesirable gaps, overlaps or discontinuities in tangent and curvature distributions at the edges of individual patches. Gaps and discontinuities are typically small enough to proceed with general layout. However, they might significantly hamper post-processing the hull design for conducting hydrostatics and stability analysis, generating grids for CFD and FEM programmes, or feeding data to a five axis mill for building a towing tank model. Fixing the surface deficiencies is usually a time consuming process and thus costly. This paper presents a systematic and fairly easy to learn methodology to design fully featured ship hulls without any gaps, overlaps or tangent and curvature discontinuities. This is achieved with just two surface patches. With proper layout of the control vertex mesh and exploitation of the geometrical properties inherent to the B-spline/NURBS definition, the resulting three-dimensional hull models are readily transferred to analysis and manufacturing systems.

Naval ship design-process analysis through dynamic social networks by Georgios Anagnostopoulos and Panagiotis Kaklis (University of Strathclyde): Modern naval ship design is increasing in complexity as more and more systems are incorporated into the design process, leading to an increase in the number (and interdependence) of tasks that designers need to complete and progress through the design stages. This work develops a dynamic bipartite social network representation, separating the nodes in activities and individuals, with the aim to analyse and draw conclusions regarding the design process. A dynamic time-dependent graph (TDG) is constructed with the use of a presence function for the edges. Network properties (density, clustering, active tasks/designers) are expressed as functions of time, and node-wise metrics (centralities) reveal the key role of individuals in the naval ship design process, which is heavily-crowded with respect to tasks. Furthermore, application of the model to naval ship design data reveals interesting insights regarding the impact of COVID-19 and the design company’s adopted hiring policy.

An Investigation into the Gate Rudder System Design for Propulsive Performance Using Design of Experiment (DoE) Method by Ahmet Yusuf Gurkan, Uğur Oral Ünal (University of Strathclyde), Batuhan Aktas (Istanbul Technical University), Mehmet Atlar (University of Strathclyde): The Gate Rudder System (GRS) is an innovative energy-saving device integrating the steering and propulsion of ships. While various scale model tests, sea trials, and voyage monitoring have demonstrated significant potential for power saving of ships with GRS, the optimal design of it, at least from the powering performance point of view, has yet to be fully explored in the open literature. This study used a Design of Experiment (DoE) approach to investigate the sensitivity of key design variables of the GRS on the ship's powering performance. Computational Fluid Dynamics (CFD) analysis was employed to calculate the respective flow variables at each design point, and the most effective geometrical parameter was identified as the rudder angle based on the correlations between the input and output parameters. Surprisingly, the analyses revealed that the best powering performance was not observed with the highest rudder thrust force generated. Instead, the optimal GRS design was found to be one that maximizes the overall energy savings for powering by achieving the most favourable interaction between the propeller, hull, and GR blades. Further validation was achieved using high-fidelity CFD modelling of the propeller action. Therefore, this study fills an important gap in the optimal GRS design from the powering performance point of view and paves for other performance behaviour optimisations involving this promising technology.

The righting arm in Archimedes’ On Floating Bodies by Chris Rorres (Drexel University): Archimedes’ Law of Buoyancy describing the magnitude of the buoyancy force on a floating object is justly regarded as the beginning of the field of hydrostatics. But a postulate he attached to it about the line of action of the buoyancy force is equally important and is essential in determining equilibrium orientations of a floating body and the stability of those orientations. In proving the stability of certain orientations of a floating truncated sphere or paraboloid, he introduced a distance now recognized as the precursor of the righting arm of a floating body. This paper delves into this seminal concept and also brings Archimedes’ results up-to-date by finding all of the equilibrium orientations – both stable and unstable – for the two basic floating bodies he studied.

Naval Architecture saves the United States at its Birth by Larrie D. Ferreiro (George Mason University): Naval architecture was developed by European sailing navies (mostly France and Spain) as a force multiplier against Britain. It became the basis for the design of the combined French – Spanish Bourbon Armada, which fought the British Navy around the globe, outnumbering and overwhelming it during the War of American Independence. Coppering, which reduced resistance, was one of the most important naval technologies developed during the war. The French frigate Concorde, designed with most advanced naval architecture theory of the era and fully coppered, carried the key dispatches that enabled French and American forces to coordinate and converge at Yorktown in 1781. All of these actions, taken together, forced Britain to sue for peace, resulting in an independent United States of America.

Acknowledgements

The editors of this Special Issue (SI) of Ship Technology Research – Schiffstechnik (STR) are grateful to the chief editors of STR, Professors Soeren Ehlers and Bettar Ould El Moctar, the publisher of STR Taylor & Francis and all contributors – authors and reviewers in particular – of scientific papers that enabled us to revisit the work and appreciate new developments inspired by late Professor Nowacki’s scientific legacy. The material compiled in this Special Issue honours late Professor Dr.-Ing. Dr. h.c. Horst Nowacki, who will be remembered by us and the naval architectural community for many years to come.