R. Cengiz Ertekin | |
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Born | |
Alma mater | Technical University of Istanbul and University of California, Berkeley |
Known for | The GN equations, Hydroelasticity of VLFS, Wave loads on coastal bridges |
Scientific career | |
Fields | Marine Hydrodynamics and Ocean Engineering |
Institutions | University of Hawaiʻi at Mānoa, United States; Harbin Engineering University of China |
Doctoral advisor | John V. Wehausen |
R. Cengiz Ertekin is a professor of Marine Hydrodynamics and Ocean Engineering. He currently holds a guest professor position at Harbin Engineering University of China. He is best known for his contributions to the development of nonlinear water wave theories, hydroelasticity of very large floating structures (VLFS), wave energy, and tsunami and storm impact on coastal bridges. He is also the co-developer, [1] along with Professor H. Ronald Riggs of the University of Hawaiʻi, of the computer program HYDRAN for solving linear fluid-structure interaction problems of floating and fixed bodies.
R. Cengiz Ertekin was born and raised in Turkey. He received a B.Sc. degree in Naval Architecture and Marine Engineering from Istanbul Technical University, the top technical university of Turkey, [2] in 1977. Following the encouragement of his advisor, Prof. M Cengiz Dokmeci, he moved to the Department of Naval Architecture and Offshore Engineering of the University of California, Berkeley, United States, for higher education. He received his M.Sc. and Ph.D. degrees in 1980 and 1984, respectively. His M.Sc. advisors were Professors Marshall P. Tulin and William C. Webster. His Ph.D. advisor was Professor John V. Wehausen. [3] [4] [5] Cengiz was the last student of Prof. John V. Wehausen before his retirement. [6] After graduation, Professor Wehausen offered Cengiz a postdoctoral research assistant position for 18 months at U.C. Berkeley.
Most of Ertekin's professional career has been dedicated to academic work; however, he also has several years of experience of working in the industry.
In 1985, Ertekin joined the Research Center of Shell Development Company in Houston, Texas. He took a faculty position (hired at the associate professor level) at the Department of Ocean Engineering of the University of Hawaiʻi at Mānoa in 1986, and received tenure within four years and was promoted to Professor in 1994. [7] The Ocean Engineering Department of UH was established by Professor Charles Bretschneider in 1966 and is one of the first of its kind in the US.
At the University of Hawaiʻi, Ertekin led and contributed immensely to the success of School of Ocean and Earth Science and Technology and the Department of Ocean and Resources Engineering (ORE, formerly Ocean Engineering). In the era of PCs, for example, Professor Ertekin played a key role in transferring the department from one focusing mostly on field and experimental studies, to also a leading institute in modern and computational hydrodynamics. The department was the host of some of the internationally leading conferences, workshops and meetings (details given below), mostly organized and chaired by Cengiz.
After almost 30 years, he retired from the University of Hawaiʻi in September 2015. Starting in March 2014, he became a guest professor at the College of Shipbuilding Engineering of Harbin Engineering University in China.
Ertekin has taught numerous courses on hydrodynamics and ocean engineering at the University of Hawaiʻi at Mānoa, and at University of California, Berkeley.
At the Ocean Engineering Department of the University of Hawaiʻi, Ertekin developed and taught several courses including Nonlinear water wave theories (ORE 707), Hydrodynamics of Fluid-Body Interaction (ORE 609), Buoyancy and Stability (ORE 411), and Marine Renewable Energy (ORE 677), to name a few. At the University of California, Berkeley, he taught Ship Statics (NAOE 151) and Ship Resistance and Propulsion (NAOE 152A).
At the University of Hawaiʻi, Ertekin advised and mentored over 50 graduate students. [8] [9] [10] [11] [12]
Ertekin's research on Marine Hydrodynamics and Ocean Engineering has extended over a period of about forty years. His work cover both basic and applied research through analytical, computational and experimental approaches. Below are an examples of his pioneering contributions. Other topics of significant research contribution by Ertekin include ship resistance, marine energy, and oil spills. [13]
The Green-Naghdi (GN) equations are nonlinear water wave equations that were originally developed by British mathematician Albert E. Green [15] and Iranian-American mechanical engineer Paul M. Naghdi [16] in the 1970s (see, [17] [18] [19] ). The original equations, namely the Level I GN equations, are mostly applicable to the propagation of long waves in shallow waters. However, high level GN equations are also developed which are applicable to deep water waves. The equations differ from the classical water wave theories (e.g. Boussinesq equations) in that the flow need not be irrotational, and that no perturbation is used in deriving the equations. Hence, the GN equations satisfy the nonlinear boundary conditions exactly, and postulate the integrated conservation laws. Although the GN equations were developed very recently (compared to other wave theories), they are well-known and fairly understood by the research and scientific community.
Ertekin's Ph.D. advisor and dissertation committee chair was Professor Wehausen. Others on his Ph.D. committee were Professor William Webster, and Professor Paul M. Naghdi. Working under close guidance of his advisors, he was one of the first to use the nonlinear equations (that were introduced just a couple of years earlier by Profs. Green and Naghdi). In his Ph.D. dissertation, Ertekin was the first to give the equations in now a familiar form to the hydrodynamics community by providing closed-form relations for the pressures. He named the equations, The Green-Naghdi Equations.
Upon completion of his Ph.D., Ertekin continued research on the GN equations. He has patiently introduced the GN equations to his graduate students and postdoctoral researchers and has guided many of them to perform basic and applied research on or by use of the GN equations. Along with his research assistant and postdocs, they developed the Irrotational GN (IGN) equations (see e.g., [20] [21] and [22] ), and high-level GN equations (see e.g., [23] [24] [25] and [26] ). They have solved some of the classical and challenging hydrodynamics problems by use of the GN equations, including nonlinear wave diffraction and refraction(see e.g. [27] ), nonlinear wave loads on vertical cylinders (see e.g. [28] ), wave interaction with elastic bodies and VLFS (see e.g. [29] ), wave loads on coastal bridges (see e.g. [30] ), and wave interaction with wave energy devices (see e.g. [31] ), among many others.
The Mobile Offshore Base (MOB) project of USA and the Mega-Float project of Japan are two examples of Very Large Floating Structures (VLFS). These are very large floating platforms consist of interconnected modules whose length can extend to several kilometers. Due to the unprecedented long length, displacement and associated hydroelastic response of VLFS, the state of the art analysis and design approaches that was used for smaller floating platforms was not adequate. It quickly became obvious that new approaches must be developed to tackle the complex problems associated to dynamics and response of VLFS.
Starting 1990's, Ertekin pioneered the research on hydroelasticity of VLFS. He and H. Ronald Riggs of the Civil Engineering Department at the University of Hawaii coined the term VLFS. They have solved the hydroelasticity problem of VLFS by use of both linear and nonlinear approaches, in two and three dimensions. Ertekin has also introduced new approaches and equations to study this topic, including the use of nonlinear water wave models to analyse the hydroelastic response of VLFS of mat type (see e.g., [32] [33] [34] and [35] ).
His work and research on hydroelasticity of VLFS has opened a new era for these topics and gave more confidence in understanding the dynamics and response of the structures.
Some of the recent tsunami and hurricanes, such as Tohoku tsunami in Japan (2011) and Hurricane Katrina in the United States (2005), caused significant damage to the decks of coastal bridges and structures. Interaction of surface waves with coastal bridges is a complex problem, involving fluid-structure interaction, multi-phase fluids, wave breaking, and overtopping. These are of course in addition to the difficulties associated to the structural analysis. Ertekin and his students studied bridge failure mechanisms and possible mitigating solutions. [36] [37] [38] [39] They developed models used to assess the vulnerability of coastal bridges in USA to tsunami and storm surge and waves. [40]
Ertekin has over 150 peer-reviewed publications. [41]
He has been on the editorial board of more than ten internationally leading journals since early 1990s (see e.g., [42] [43] and [44] ), and editor of several special issues in various journals, see e.g. Renewable Energy: Leveraging Ocean and Waterways special issue of Applied Ocean Research journal (2009). [45] He was the co-editor-in-chief of Elsevier's Ocean Engineering journal (2006–2010), [46] and he is the founding editor-in-chief of Springer's Journal of Ocean Engineering and Marine Energy. [47] Ertekin has been keynote speaker of several leading meetings and conferences, see e.g. [48] and. [49]
In fluid dynamics, a wind wave, or wind-generated water wave, is a surface wave that occurs on the free surface of bodies of water as a result of the wind blowing over the water's surface. The contact distance in the direction of the wind is known as the fetch. Waves in the oceans can travel thousands of kilometers before reaching land. Wind waves on Earth range in size from small ripples to waves over 30 m (100 ft) high, being limited by wind speed, duration, fetch, and water depth.
Wave power is the capture of energy of wind waves to do useful work – for example, electricity generation, water desalination, or pumping water. A machine that exploits wave power is a wave energy converter (WEC).
In numerical analysis, adaptive mesh refinement (AMR) is a method of adapting the accuracy of a solution within certain sensitive or turbulent regions of simulation, dynamically and during the time the solution is being calculated. When solutions are calculated numerically, they are often limited to predetermined quantified grids as in the Cartesian plane which constitute the computational grid, or 'mesh'. Many problems in numerical analysis, however, do not require a uniform precision in the numerical grids used for graph plotting or computational simulation, and would be better suited if specific areas of graphs which needed precision could be refined in quantification only in the regions requiring the added precision. Adaptive mesh refinement provides such a dynamic programming environment for adapting the precision of the numerical computation based on the requirements of a computation problem in specific areas of multi-dimensional graphs which need precision while leaving the other regions of the multi-dimensional graphs at lower levels of precision and resolution.
Marine engineering is the engineering of boats, ships, submarines, and any other marine vessel. Here it is also taken to include the engineering of other ocean systems and structures – referred to in certain academic and professional circles as "ocean engineering". After completing this degree one can join a ship as an officer in engine department and eventually rise to the rank of a chief engineer. This rank is one of the top ranks onboard and is equal to the rank of a ship's captain. Marine engineering is the highly preferred course to join merchant Navy as an officer as it provides ample opportunities in terms of both onboard and onshore jobs.
In fluid dynamics, vortex-induced vibrations (VIV) are motions induced on bodies interacting with an external fluid flow, produced by, or the motion producing, periodic irregularities on this flow.
Paul Mansour Naghdi was a professor of mechanical engineering at University of California, Berkeley.
Very large floating structures (VLFSs) or very large floating platforms (VLFPs) are artificial islands, which may be constructed to create floating airports, bridges, breakwaters, piers and docks, storage facilities, wind and solar power plants, for military purposes, to create industrial space, emergency bases, entertainment facilities, recreation parks, mobile offshore structures and even for habitation. Currently, several different concepts have been proposed for building floating cities or huge living complexes. Some units have been constructed and are presently in operation.
A parametric array, in the field of acoustics, is a nonlinear transduction mechanism that generates narrow, nearly side lobe-free beams of low frequency sound, through the mixing and interaction of high frequency sound waves, effectively overcoming the diffraction limit associated with linear acoustics. The main side lobe-free beam of low frequency sound is created as a result of nonlinear mixing of two high frequency sound beams at their difference frequency. Parametric arrays can be formed in water, air, and earth materials/rock.
In fluid dynamics and elasticity, hydroelasticity or flexible fluid-structure interaction (FSI), is a branch of science which is concerned with the motion of deformable bodies through liquids. The theory of hydroelasticity has been adapted from aeroelasticity, to describe the effect of structural response of the body on the fluid around it.
In fluid dynamics, a Stokes wave is a nonlinear and periodic surface wave on an inviscid fluid layer of constant mean depth. This type of modelling has its origins in the mid 19th century when Sir George Stokes – using a perturbation series approach, now known as the Stokes expansion – obtained approximate solutions for nonlinear wave motion.
Coastal engineering is a branch of civil engineering concerned with the specific demands posed by constructing at or near the coast, as well as the development of the coast itself.
Howell Peregrine was a British applied mathematician noted for his contributions to fluid mechanics, especially of free surface flows such as water waves, and coastal engineering.
In fluid dynamics, Airy wave theory gives a linearised description of the propagation of gravity waves on the surface of a homogeneous fluid layer. The theory assumes that the fluid layer has a uniform mean depth, and that the fluid flow is inviscid, incompressible and irrotational. This theory was first published, in correct form, by George Biddell Airy in the 19th century.
The moving particle semi-implicit (MPS) method is a computational method for the simulation of incompressible free surface flows. It is a macroscopic, deterministic particle method developed by Koshizuka and Oka (1996).
Chiang Chung "CC" Mei is Ford Professor of Engineering, Emeritus, at the Department of Civil and Environmental Engineering of Massachusetts Institute of Technology, known for his contributions in fluid mechanics with applications to civil, environmental, and coastal engineering.
John Vrooman Wehausen was an American applied mathematician considered to be one of the world's leading researchers and pioneers in the field of marine hydrodynamics.
Albert Edward Green was a British applied mathematician and research scientist in theoretical and applied mechanics.
B. Mutlu Sumer is a Turkish scientist and engineer known for his studies on seabed and structure interaction including scour and soil liquefaction, as well as turbulence in coastal and civil engineering. He was previously Professor at the Technical University of Denmark until he retired in 2015. He held a Professor-Emeritus position between June 2015 and June 2017 at the same university. He was Professor of Hydraulics at Istanbul Technical University before he moved to Denmark in 1984. B. Mutlu Sumer relocated to Turkey, his native country, in 2016 and, together with Professor Özgür Kirca, founded a consultancy and research company, BM SUMER Consultancy & Research, affiliated with Istanbul Technical University.
The nonlinearity of surface gravity waves refers to their deviations from a sinusoidal shape. In the fields of physical oceanography and coastal engineering, the two categories of nonlinearity are skewness and asymmetry. Wave skewness and asymmetry occur when waves encounter an opposing current or a shallow area. As waves shoal in the nearshore zone, in addition to their wavelength and height changing, their asymmetry and skewness also change. Wave skewness and asymmetry are often implicated in ocean engineering and coastal engineering for the modelling of random sea states, in particular regarding the distribution of wave height, wavelength and crest length. For practical engineering purposes, it is important to know the probability of these wave characteristics in seas and oceans at a given place and time. This knowledge is crucial for the prediction of extreme waves, which are a danger for ships and offshore structures. Satellite altimeter Envisat RA-2 data shows geographically coherent skewness fields in the ocean and from the data has been concluded that large values of skewness occur primarily in regions of large significant wave height.
Jørgen Fredsøe (1947) is a Danish hydraulic engineer who is recognized for his contributions within bed form dynamics in rivers and the marine environment and coastal morphology including bars and beach undulations. Together with professor B. Mutlu Sumer he initiated the research on scour (erosion) in the seabed around coastal structures applying detailed hydrodynamic interpretations. He was born in Randers, Denmark.