Publications

Submitted
Flood-induced Debris Motion Within A Built-in Environment
Nistor I, Goseberg N, Stolle J, Matsuba S, Nakamura R, Mikami T, Shibayama T. Flood-induced Debris Motion Within A Built-in Environment, in Coastal Engineering Proceedings. Istanbul, Turkey; Submitted.
Projecting Morphodynamic Change Due To Harbor Refurbishment: A Practical Example From A Small North Sea Harbor In The Wadden Sea
Lojek O, Schlurmann T, Goseberg N. Projecting Morphodynamic Change Due To Harbor Refurbishment: A Practical Example From A Small North Sea Harbor In The Wadden Sea. Journal of Waterway, Port, Coastal, and Ocean Engineering. Submitted.
Stolle J, Goseberg N, Nistor I, Shibayama T. Debris Impacts and Effects on Structures. In: Kim YC Handbook of Coastal and Ocean Engineering. World Scientific; Submitted. pp. n/a – n/a.
2019
Gate-Opening Criteria for Generating Dam-Break Waves
von Häfen H, Goseberg N, Stolle J, Nistor I. Gate-Opening Criteria for Generating Dam-Break Waves. Journal of Hydraulic Engineering [Internet]. 2019;145(3):04019002. Publisher's VersionAbstract
Dam-break waves are commonly used throughout the field of hydraulic engineering. Given the availability of several well-developed analytical solutions, as well as the relative ease with which they can be implemented as a numerical or physical boundary condition, dam-break waves have been used to examine various phenomena. This study employs a smoothed particle hydrodynamics (SPH) model to examine the influence of the gate opening on characteristics of the wave propagation. First, the model was extensively validated using experimental results from tests which employed swing and lift gates. Generally, any dam-break gate should open or be removed as fast as possible to allow the formation of a perfect dam break wave. However, cost-benefit considerations and technical design constraints, particularly for gates fitted on large-scale test facilities, result in less than instantaneous gate motions because the complexity and associated cost of the gate increases exponentially with increasing drive capacity. Larger gate weights installed in wide flumes require an improved understanding of the errors involved with slower opening times of both types of gate mechanisms. The study found that the influence of the gate opening time decreased with time elapsed from impounded water release, as well as with the downstream distance from the gate. The study also provides an estimate of the errors associated with the gate opening time to help engineers and researchers in the process of planning to generate such waves.
Debris impact forces on flexible structures in extreme hydrodynamic conditions
Stolle J, Goseberg N, Nistor I, Petriu E. Debris impact forces on flexible structures in extreme hydrodynamic conditions. Journal of Fluids and Structures [Internet]. 2019;84:391 - 407. Publisher's VersionAbstract
Field surveys of recent major flood events have emphasized the need for an in-depth examination of debris loading. Debris loading occurs when solid objects entrained within the flow interact with a structure in its movement path, exerting loads through direct impacts or damming. Until now, the focus of research into debris impacts has concentrated on single debris impacting a rigid structure. This study extends to examining the influence of debris impacting a flexible structure. A two degree-of-freedom (2DOF) system was used to model the debris–structure interaction. The model is compared with two experimental data sets using a rigid body and the effective stiffness model. The proposed 2DOF model was shown to be more accurate in estimating the impact force than those to which it was compared to. However, due to difficulties in estimating the stiffness and inertia of the structure and the debris, the proposed model under predicted the maximum measured impact loads. The effective stiffness model was shown to represent the maximum measured impact loads, and should therefore be implemented in the design process when considering debris impacts on flexible structures.
2018
Experimental investigation of debris damming loads under transient supercritical flow conditions
Stolle J, Takabatake T, Nistor I, Mikami T, Nishizaki S, Hamano G, Ishii H, Shibayama T, Goseberg N, Petriu E. Experimental investigation of debris damming loads under transient supercritical flow conditions. Coastal Engineering. 2018;139:16–31.
Debris impact under extreme hydrodynamic conditions part 2: Impact force responses for non-rigid debris collisions
Stolle J, Derschum C, Goseberg N, Nistor I, Petriu E. Debris impact under extreme hydrodynamic conditions part 2: Impact force responses for non-rigid debris collisions. Coastal Engineering [Internet]. 2018;141:107 - 118. Publisher's VersionAbstract
Historical tsunami events have resulted in extreme damage to coastal regions worldwide. Among the various loads associated with tsunami waves, debris impact has been shown to cause major damage to nearshore infrastructure. As a result, debris impact loads have been included prominently in existing design guidelines and standards, such as the FEMA P-646 [11] and ASCE7 Chapter 6 [6]. In the present study, single debris impacts on structures was experimentally investigated under tsunami-like wave conditions. Eccentric and oblique impacts of a model shipping container (length scale 1:40) on a non-rigid structure were examined. The experimental results of the non-rigid impacts are discussed in the context of the existing force equations which were derived under the assumption of rigid-body impact theory. As expected, the elasticity of the structure was determined to influence and, specifically, reduce the magnitude of the debris impact forces. Existing impact force equations are herein critically discussed through comparison with the experimental results and, finally, modifications to existing force equations to account for non-rigid collisions are proposed.
Swing gate generated dam-break waves
Stolle J, Ghodoosipour B, Derschum C, Nistor I, Petriu E, Goseberg N. Swing gate generated dam-break waves. Journal of Hydraulic Research [Internet]. 2018:1-13. Publisher's VersionAbstract
ABSTRACTThe study presented herein examines the influence of a swing gate on the generation of dam-break waves. Recently, researchers have been using swing gate systems, as opposed to vertical lift gates, as swing gates can be more economical as well as simpler to design and construct. The experimental programme presented herein examines the influence of the swing gate opening time on the generation, propagation and evolution of the dam-break wave profile and hydrodynamics downstream of the gate. Wave profiles were measured at several locations downstream of the gate to determine the influence of the gate opening time on its characteristics. The gate opening time was demonstrated to have a linear dependence on the wave arrival time, likely due to the gate interference in the formation of the wave. The wave profile, however, was not found to be significantly influenced by the gate opening time.
Debris impact under extreme hydrodynamic conditions part 1: Hydrodynamics and impact geometry
Derschum C, Nistor I, Stolle J, Goseberg N. Debris impact under extreme hydrodynamic conditions part 1: Hydrodynamics and impact geometry. Coastal Engineering [Internet]. 2018;141:24 - 35. Publisher's VersionAbstract
In field investigations of major flooding events, debris impact has been identified as a critical load and has thus been included in various building codes, such as FEMA P-646 and ASCE7. However, the evaluation of debris loading solely based on field data is challenging. Therefore, to address the uncertainties related to debris loading, an experimental program investigating debris impacts on structures was performed using a dam-break wave. The debris were down-scaled 6.1 m (20 ft) shipping containers (1:40 geometric scale) which were entrained and displaced by the transient wave conditions. The study presented here examines the influence of the transient flow conditions and the flow features around the structure due to the impinging wave on the debris impact conditions. The influence of the impact geometry (obliqueness, eccentricity) on the impact force is also discussed and possible parameters to describe the impact geometry are introduced.
Processes and evolution of scour around a monopile induced by tidal currents
Schendel A, Hildebrandt A, Goseberg N, Schlurmann T. Processes and evolution of scour around a monopile induced by tidal currents. Coastal Engineering [Internet]. 2018;139:65-84. Publisher's Version
Probabilistic Investigation and Risk Assessment of Debris Transport in Extreme Hydrodynamic Conditions
Stolle J, Goseberg N, Petriu E, Nistor I. Probabilistic Investigation and Risk Assessment of Debris Transport in Extreme Hydrodynamic Conditions. Journal of Waterways, Port, Coastal, and Ocean Engineering. 2018;144(1):04017039-1.Abstract
Recent extreme hydrodynamic events, such as the 2004 Indian Ocean Tsunami, 2005 Hurricane Katrina, and 2013 Typhoon Haiyan, have indicated the vulnerability of coastal communities. As a result, emphasis has been placed on understanding and developing methods of assessing the potential loads  associated with these extreme events. The majority of research has focused on assessing the risk of hydrodynamic loads; however, little research has gone into assessing the potential for debris loading. The following study aimed to address the trajectory of debris within extreme hydrodynamic conditions to aid in the  assessment of risk for debris loading. Laboratory experiments were performed using a dam-break wave as the hydrodynamic forcing condition. The trajectory and velocity of the debris were examined to determine the statistical characteristics of the debris motion. The study showed that the lateral  displacement of the debris can be evaluated using a normal distribution, and the velocity of the debris can be conservatively modeled as the wave front velocity.
Influence of reversing currents on the erosion stability and scour protection potential of wide-graded grain material
Schendel A, Goseberg N, Schlurmann T. Influence of reversing currents on the erosion stability and scour protection potential of wide-graded grain material. International Journal of Sediment Research. 2018;33(1):68-83.Abstract
Physical model tests were carried out in a closed-circuit flume to investigate the overall erosion stability and the scour protection potential of wide-graded bed material in estuarine and coastal conditions by means of simulating tidal flow conditions with reversing currents. As a result of the reversing flow conditions, previously protected sediment eventually became exposed again, leading to bidirectional displacement processes in dependency of the flow direction. Furthermore, eroded sediment fractions were slightly finer due to flow in initially applied direction than under the subsequently applied flow in reversed direction. This indicates higher critical shear stresses and thus erosion stability for the initial flow direction. In comparison to erosional pattern found when subjecting the material to unidirectional currents, this study finds an even higher erosional stability for sediment fractions smaller than the median d50 diameter of the initial bed material under reversing current conditions. Overall, no significant damage or failure of the bed was observed after subjecting the material to reversing currents, indicating a high potential as scour protection under the tested flow conditions, particularly if applied as single-layer setup in a dynamically stable design.
2017
Debris Dynamics And Associated Loads In Extreme Hydrodynamic Conditions
Stolle J, Goseberg N, Derschum C, Nistor I. Debris Dynamics And Associated Loads In Extreme Hydrodynamic Conditions, in E-proceedings of the 37th IAHR World Congress. Kuala-Lumpur, Malaysia; 2017.
Flood-induced Debris Motion In A Built-in Environment
Nistor I, Goseberg N, Stolle J. Flood-induced Debris Motion In A Built-in Environment, in E-proceedings of the 37th IAHR World Congress. Kuala-Lumpur, Malaysia; 2017.
Swing Gate Generated Dam Break Waves
Goseberg N, Stolle J, Derschum C, Nistor I. Swing Gate Generated Dam Break Waves, in E-proceedings of the 37th IAHR World Congress. Kuala-Lumpur, Malaysia; 2017.
Experimental Investigation of Debris-Induced Loading in Tsunami-Like Flood Events
Stolle J, Takabatake T, Mikami T, Shibayama T, Goseberg N, Nistor I, Petriu E. Experimental Investigation of Debris-Induced Loading in Tsunami-Like Flood Events. geosciences [Internet]. 2017;7(3):74. Publisher's VersionAbstract
Debris loads during flood events have been well-documented by forensic engineering field surveys of affected communities. Research has primarily focused on debris impact loading and less emphasis has been placed into quantifying the loads and effects associated with debris damming, which occurs when solid objects accumulate at the front of structures. The formation of the debris dam has been shown to results in increased drag forces, backwater rise, and flow accelerations which can influence the stability of the structure. This study examined the formation of a debris dam in steady-state conditions of debris common to flood-prone communities. The study determined that the hydraulic conditions, in particular flow velocity, influenced the formation of the debris dam. Additionally, the study examined the influence of the blockage ratio on the backwater rise as well as the drag coefficient.
geosciences-07-00074_small.pdf
The German Case Study: Pioneer Projects of Aquaculture-Wind Farm Multi-uses
Buck BH, Krause G, Pogoda B, Grote B, Wever L, Goseberg N, Schupp MF, Mochtak A, Czybulka D. The German Case Study: Pioneer Projects of Aquaculture-Wind Farm Multi-uses. In: Aquaculture Perspective of Multi-Use Sites in the Open Ocean: The Untapped Potential for Marine Resources in the Anthropocene. Springer International Publishing; 2017. pp. 253-354. Publisher's VersionAbstract
Most studies on multi-use concepts of aquaculture and wind farms explored cultivation feasibility of extractive species, such as seaweed or bivalves. However, recent studies also included the cultivation of crustaceans or fish culture in the vicinity of wind turbines. Consequently, new approaches combine fed and extractive species in integrated multi-trophic aquaculture (IMTA) concepts for offshore multi-use to reduce nutrient output and the overall environmental impact of aquaculture operations. In this chapter the findings of a series of mussel and oyster cultivation experiments over several seasons are presented, which were conducted at different offshore test sites in the German Bight. Sites were selected within future offshore wind farm areas for an explicit multi-use perspective. Results have demonstrated successful growth and fitness parameters of these candidates and therefore definitely proved the suitability of these bivalve extractive species for open ocean aquaculture. Another approach for multi-use in offshore wind farms is its use as marine protected area or even for reinforcement or restoration of endangered species, which need the absence of any fisheries activity for recovery. Current projects are testing this perspective for the native European oyster Ostrea edulis and the European lobster Homarus gammarus. From the technological point of view there are many options on how to connect aquaculture devices, such as longline and ring structures as well as different cage types, to the foundations as well as to install it in the centre of the free area between wind turbines. Next to the system design also experiments on drag forces originating from the aquaculture structure on the foundation and vice versa were investigated. Complementary to the biological, environmental end technical aspects, a number of studies were specifically targeted to address and include stakeholders, their attitudes, their interests and concerns over time. By this approach, the inclusion of stakeholders into the research process from its very beginning until today, co-production of knowledge could be fostered. Next to joint identification of the major impediments and concerns of offshore aquaculture under multi-use conditions, new issues and research questions were identified. Primary focus on the economic potential of aquaculture in offshore wind farms was shown for consumption mussels. The production of mussels using longline technology is sufficiently profitable even under the assumption of substantial cost increases. This is especially true, if existing capacities could be used. Last but not least, the EEZ is a special area{--}it is not a state territory even if a coastal state has its sovereign rights and jurisdiction. It is an area where three legal systems come together: international law, law of the European Union and national law. There are no mariculture projects in the German EEZ and no approval procedure has been completed so far. Some sites are not suitable for mariculture, especially because of nature conservation and shipping.
Technological Approaches to Longline- and Cage-Based Aquaculture in Open Ocean Environments
Goseberg N, Chambers M, Haesmann K, Fredriksson D, Fredheim A, Schlurmann T. Technological Approaches to Longline- and Cage-Based Aquaculture in Open Ocean Environments. In: Aquaculture Perspective of Multi-Use Sites in the Open Ocean: The Untapped Potential for Marine Resources in the Anthropocene. Springer International Publishing; 2017. pp. 71-95. Publisher's VersionAbstract
As the worldwide exploitation rate of capture fisheries continues, the development of sustainable aquaculture practices is increasing to meet the seafood needs of the growing world population. The demand for aquatic products was historically satisfied firstly by an effort to expand wild catch and secondly by increasing land-based and near-shore aquaculture. However, stagnation in wild catch as well as environmental and societal challenges of land-based and near-shore aquaculture have greatly promoted efforts to development farming offshore technologies for harsh, high energetic environments. This contribution thus highlights recent technological approaches based on three sample sites which reach out from sheltered near-shore aquaculture sites to sites with harsh wave/current conditions. It compares and evaluates existing technological approaches based on a broad literature review; on this basis, we then strongly advocate for presently available aquaculture technologies to merge with future offshore structures and platforms and to unveil its added value through synergetic multi-use concepts. The first example describes the recent development of longline farming in offshore waters of New Zealand. New Zealand has designated over 10,000 ha of permitted open ocean water space for shellfish farming. The farms range from 8 to 20 km out to sea and a depth of 35–80 m of water. Research has been ongoing for the last 10 years and the first commercial efforts are now developing in the Bay of Plenty. New methods are being developed which should increase efficiency and reduce maintenance with a particular focus on Greenshell mussel (Perna canaliculus) and the Pacific Oyster (Crassostrea gigas), Flat Oyster (Tiostrea chilensis) and various seaweeds. The second case study involves a long-term, open ocean aquaculture (OOA) research project conducted by the University of New Hampshire. During the course of approximately 10 years, the technological aspects of OOA farming were conducted with submersible cages and longlines, surface feeding systems and real time environmental telemetry. The grow-out potential of multiple marine species such as cod (Gadus morhua), haddock (Melanogrammus aeglefinus), halibut (Hippoglossus hippoglossus), blue mussel (Mytilus edulis), sea scallop (Placopecten magellanicus) and steelhead trout (Oncorhynchus mykiss) were investigated at a site 12 km from shore. The last study presents a multi-use aspect of aquaculture for an open ocean site with fish cages attached to existing offshore wind energy foundations. Technological components such as mounting forces and scour tendencies of two different cage structures (cylindrical and spherical) were investigated by means of hydraulic scale modeling. The cages were pre-designed on the basis of linear theory and existing standards and subsequently exposed to some realistic offshore wave conditions. The wind farm “Veja Mate” in German waters with 80 planned 5 MW turbines anchored to the ground by tripiles is taken as the basis for the tested wave conditions. Based on findings stemming from the three example approaches conclusions are drawn and future research demand is reported.
Entrainment and Transport Dynamics of Debris in Extreme Hydrodynamic Conditions
Stolle J, Nistor I, Goseberg N, Mikami T, Shibayama T. Entrainment and Transport Dynamics of Debris in Extreme Hydrodynamic Conditions. Coastal Engineering Journal [Internet]. 2017;1750011. Publisher's VersionAbstract
An experimental study was performed to examine multiple debris entrainment and transport in tsunami-like flow conditions. The study was performed in the Tsunami Wave Basin at Waseda University. The wave basin used a falling-head driven elongated solitary wave that broke at the edge of a horizontal apron to generate a tsunami-like surge. The debris, modeled as scaled-down (1:40 length scale) 20-foot standard shipping containers, was placed on the horizontal apron. The debris was tracked using a camera-based object tracking algorithm. The study examined the effect of the debris configuration, the number of debris, and orientation of debris on the entrainment and transport within the inundating surge. In examining the transport of multiple debris, the debris tended to be transported within the surge as an agglomeration. Using a previously derived model of debris the study determined experimentally derived coefficients to explain the difference in debris transport between various configurations. An experimental study was performed to examine multiple debris entrainment and transport in tsunami-like flow conditions. The study was performed in the Tsunami Wave Basin at Waseda University. The wave basin used a falling-head driven elongated solitary wave that broke at the edge of a horizontal apron to generate a tsunami-like surge. The debris, modeled as scaled-down (1:40 length scale) 20-foot standard shipping containers, was placed on the horizontal apron. The debris was tracked using a camera-based object tracking algorithm. The study examined the effect of the debris configuration, the number of debris, and orientation of debris on the entrainment and transport within the inundating surge. In examining the transport of multiple debris, the debris tended to be transported within the surge as an agglomeration. Using a previously derived model of debris the study determined experimentally derived coefficients to explain the difference in debris transport between various configurations.Read More: http://www.worldscientific.com/doi/abs/10.1142/S0578563417500115 An experimental study was performed to examine multiple debris entrainment and transport in tsunami-like flow conditions. The study was performed in the Tsunami Wave Basin at Waseda University. The wave basin used a falling-head driven elongated solitary wave that broke at the edge of a horizontal apron to generate a tsunami-like surge. The debris, modeled as scaled-down (1:40 length scale) 20-foot standard shipping containers, was placed on the horizontal apron. The debris was tracked using a camera-based object tracking algorithm. The study examined the effect of the debris configuration, the number of debris, and orientation of debris on the entrainment and transport within the inundating surge. In examining the transport of multiple debris, the debris tended to be transported within the surge as an agglomeration. Using a previously derived model of debris the study determined experimentally derived coefficients to explain the difference in debris transport between various configurations.Read More: http://www.worldscientific.com/doi/abs/10.1142/S0578563417500115
Tsunami-Driven Debris Motion and Loads: A Critical Review
Nistor I, Goseberg N, Stolle J. Tsunami-Driven Debris Motion and Loads: A Critical Review. Frontiers in Build Environment. 2017;3.

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