166 Works

Resilience through aroecology and ecological restoration : the system of rice intensification with intercropping

Tavseef Mairaj Shah & Ralf Otterpohl

Predicting long-term dynamics of soil salinity and sodicity on a global scale

Amirhossein Hassani, Adisa Azapagic & Nima Shokri
Knowledge of spatiotemporal distribution and likelihood of (re)occurrence of salt-affected soils is crucial to our understanding of land degradation and for planning effective remediation strategies in face of future climatic uncertainties. However, conventional methods used for tracking the variability of soil salinity/sodicity are extensively localized, making predictions on a global scale difficult. Here, we employ machine-learning techniques and a comprehensive set of climatic, topographic, soil, and remote sensing data to develop models capable of making...

On the potential of gassy marine soils triggering submarine slope instabilities

Pauline Kaminski & Jürgen Grabe
The development of debris flows and turbidity currents in the course of a submarine slope failure event can cause major damage in offshore infrastructure. Additionally, the tsunamogenic potential of large slope failures at continental margins poses a direct threat to coastal communities. Therefore, the trigger mechanisms of submarine slope failures have been thoroughly investigated in the past. However, the influence of free gas in the sediment, which has been observed close to several slide events,...

The CFD study of rudder-bulb-fin system in changing cambered foil and AOA applied to KVLCC2 tanker

Tho-Quang Truong & Yasuyuki Toda
The present research is to develop the fin geometry based on an available rudder designed for KVLCC2 tanker in calm water. The improvement of rudder-bulb-fin system is discussed in detail in this paper. The cambered foil that is used in this research is a cambered 4-digit airfoil as a design of the National Advisory Committee for Aeronautics. The mean camber line and thickness have been adjusted and simulated using CFDship-Iowa code to be able to...

Turbulent mixing analysis of discharge streams for open-loop exhaust gas cleaning system

Yung-An Chu & Tsung-Yueh Lin
Due to IMO regulations on sulphur oxides (SOx) emissions after 2020, exhaust gas cleaning systems (EGCS) or equivalent measures are commonly being adopted on ships. For open-loop type SOx scrubbers, one of the requirements is that, during commissioning of the EGC unit, the pH-value of the discharged wash water plume shall be no less than 6.5, measured 4 meters externally from the ship at rest, verified either by means of direct measurement or by using...

Software-In-the-Loop Method to Predict the Global Dynamic Responses of Full-scale Floating Wind Turbines by Artificial Neural Network

Peng Chen, Zhiqiang Hu & Changhong Hu
The design of floating offshore wind turbines (FOWTs) need accurate predictions of full-scale global dynamic responses. Conventional basin experimental method can hardly be used directly to predict the full-scale global dynamic responses of FOWTs, due to the dissimilarity of aerodynamic load and hydrodynamic load. Besides, numerical simulation methods are not reliable enough at this moment due to the lack of full-scale data validation. Therefore, it is necessary to find an accurate, economic and efficient approach...

An energy-efficient adaptive course control system for ocean surface ships

Changyuan Chen, Manases Tello Ruiz, Guillaume Delefortrie, Marc Vantorre & Evert Lataire
In order to improve the performance and the energy efficiency (rudder actions) of the ship control system in presence of changing environmental conditions and system uncertainty, this paper develops a novel adaptive fuzzy-PID course controller with a dynamic compensator and a nonlinear feedback for the autonomous surface ship. Firstly, an adaptive PID control strategy, whose control parameters are real-time adjusted by the fuzzy system, is designed to achieve the optimal control effect and the robust...

Diffraction of wavefront around cylinders

R. P. Li, X. B. Chen & W. Y. Duan
The diffraction of transient waves around an infinite cylinder vertically fixed in deepwater is considered. The velocity potential and corresponding normal derivatives on the cylinder surface are expanded by the Laguerre function in vertical direction and Fourier series along the circumference. Green’s Theorem is applied in the domain external to the cylinder, to obtain the so-called Dirichlet-to-Neumann (DtN) operator, which represents the relationship between series expansion coefficients related to the velocity potential and its normal...

A linearized free-surface RANS method for self-propulsion and maneuvering

Paolo Geremia, Kevin J. Maki & Pavlos Alexias
Numerical prediction of the hydrodynamical performance of unsteady ship operations, such as self-propulsion and maneuvering, is an important method to help naval architects design optimal ship hulls. Currently, traditional finite-volume Computational Fluid Dynamics (CFD) methods offer a well-proven simulation platform to realize such predictions with a high degree of accuracy. In this work, a novel transient CFD method based on an unsteady linearized free-surface RANS solver is presented for the objective of simulating ship maneuvering....

Numerical investigation of cavitation and hydrodynamic characteristics of damaged propeller

Minsheng Zhao & Decheng Wan
In the present study, a numerical simulation of cavitation flows around a damaged and a complete four –bladed E779A propeller has been carried out. The numerical results can be used as a reference to evaluate the working ability of a propeller in case of damage. In numerical simulation, the damaged propeller is simplified as the INSEAN E779A propeller missing one blade, hence, it’s a three-bladed. The typical unsteady dynamics are predicted by the RANS method...

Fully automatic design space exploration by RANS computations

Sebastian Uharek, Stefan Harries & Andrés Cura Hochbaum
The present paper presents the result of a design space exploration study for three design variables performed for a twin screw ROPAX ship performed with the Computer Aided Engineering (CAE) software CAESES and the RANS code Neptuno using the meshing software GridPro for the automatic generation of the computational grid for each design iteration step. The design space exploration is carried out using an ensemble design engine, which performs a systematic variation of the parameters...

Study of trim optimization based on design of experiments and RANS simulation

Jianwei Chen, Cheng Yu & Liang Shen
Trim optimization is a particularly easy and cheap way of improving ship performance, reducing fuel oil consumption and lowering emission. The purpose of trim optimization is to obtain the optimal trim to minimize the ship total resistance at the specified draft and speed. The usual approach is to establish a surrogate model to estimate the ship resistance based on some sample points. However, for most of present practices of trim optimization, a large number of...

Scale Effect on the Hydrodynamic Performance of a Ducted Propeller under Consideration of Flow Transition and Cavitation

Erik Schomburg & Moustafa Abdel-Maksoud
The paper presents a numerical investigation of the scale / Reynolds number effects on the hydrodynamic performance of a 4-bladed ducted propeller under open water test conditions. In the numerical simulations, the influences of flow transition and cavitation are taken into account. The RANS calculations are carried out using the ANSYS-CFX solver. For turbulence modelling, the Explicit Algebraic Reynolds Stress Model (EARSM) is applied in combination with the γ-Re θ transition model. The cavitation model...

Stakeholder participation in the planning and design of nature-based solutions : insights from CLEVER Cities Project in Hamburg

Alessandro Arlati, Anne Rödl, Sopho Kanjaria-Christian & Jörg Knieling
Cities are essential players in responding to the present complex environmental and social challenges, such as climate change. The nature-based solution (NbS) concept is identified in the scientific discourse and further recognized by the European Commission as a part of the solution to address such challenges. Deploying NbS in urban contexts requires the cooperation of different public and private stakeholders to manage those processes. In this paper, the experiences of establishing and managing NbS-related processes...

Fuel planning strategies considering operational uncertainties of aerodynamic formation flight

Majed Swaid, Tobias Marks, Florian Linke & Volker Gollnick
The operational concept of aerodynamic formation flight, also referred to as aircraft wake-surfing for efficiency (AWSE), has high potential in terms of fuel savings and climate impact mitigation. In order to implement this concept, many technological and operational challenges have to be coped with. As the fuel consumption during a mission strongly depends on a successful execution of AWSE, the existing uncertainties regarding flight planning increase. While a conservative fuel planning ensures a follower to...

Toward ATM resiliency : a deep CNN to predict number of delayed flights and ATFM delay

Rasoul Sanaei, Brian Alphonse Pinto & Volker Gollnick
The European Air Traffic Management Network (EATMN) is comprised of various stakeholders and actors. Accordingly, the operations within EATMN are planned up to six months ahead of target date (tactical phase). However, stochastic events and the built-in operational flexibility (robustness), along with other factors, result in demand and capacity imbalances that lead to delayed flights. The size of the EATMN and its complexity challenge the prediction of the total network delay using analytical methods or...

Dissimilar titanium and titanium aluminide joints manufactured by laser beam welding and laser additive manufacturing

Irmela Burkhardt
Durch die zunehmenden Anforderungen an Leichtbaukonstruktionen motiviert, ist das Ziel ungleichartige Ti- und γ-TiAl-Ti-Legierungs-Verbindungen aus Blechen rissfrei mittels Laserstrahlschweißen herzustellen. Dies wurde durch Vorheizen erreicht. Die Rissentstehung konnte der Mikrostruktur-Phasen-Entwicklung zugeordnet werden. Der Einfluss der Grenzfläche auf den Versagensort und die Zugeigenschaften wurde durch Zugversuche ermittelt. Zudem wurde das gewonnene Wissen bezüglich der Mikrostruktur-Phasen-Entwicklung an der Grenzfläche erfolgreich auf laserauftragsgeschweißte Strukturen übertragen und die Grenzen der Übertragbarkeit bezüglich der Rissbildung aufgezeigt. Folglich wurden die Grundlagen...

Investigation of training data selection in the black-box modeling of ship maneuvering motion

Zihao Wang, Carlos Guedes Soares & Zaojian Zou
For the identification modeling of ship maneuvering motion, comparisons between various training data are conducted to select appropriate excitation signal with maximum dynamic information, thereby ensuring the generalization ability of the identified model. The identification framework is black-box modeling based on the (“nu”)-support vector machine algorithm with radial basis function kernel, which automatically controls the number of support vectors and keeps sparsity. A Mariner class ship is taken as the study object, and the training...

Numerical and Test Analysis for Resistance and Self-Propulsion Performance of a Trailing Suction Hopper Dredger

Zhigao Luo & Long Yu
Resistance and self-propulsion performances of trailing suction hopper dredger (TSHD) remains a hot issue in predicting and improving performances of TSHD. In this paper, the CFD simulation technology and overset technology are used to calculate the resistance performance of TSHD at different velocities, and the results are accord with the model test results. Then overset technology is used to calculate the self-propelled performances of THSD equipped with different propellers under different working conditions. The results...

Damping of non-linear and irregular long-crested free-surface waves using forcing zones

Robinson Peric & Moustafa Abdel-Maksoud
Forcing-zone-type approaches (such as absorbing layers, damping zones, sponge layers, relaxation zones, etc.) can be used to reduce undesired wave reflections at the domain boundaries in flow simulations with free-surface waves. They introduce source terms in one or several of the governing equations in a zone adjacent to the corresponding domain boundaries, with the intention of gradually forcing the solution within the zone towards some reference solution. These source terms contain case-dependent parameters that require...

Numerical study of sloshing motion on unstructured mesh using UMTHINC

Mohamed M. Kamra & Changhong Hu
The numerical simulations of sloshing motions are performed for different test cases with various filling levels and oscillation frequencies. The numerical results are analyzed and compared with experimental data. The numerical computations are performed with a Volume Of Fluid (VOF) based Reynolds-Averaged Navier-Stokes (RANS) solver. Our in-house numerical solver employs the unstructured multi-dimensional tangent hyperbolic interface capturing method (UMTHINC) for free-surface capturing combined with various turbulence models. The sloshing motion is numerically modeled using the...

Sensitivity analysis for ship squat predictions using Sobol’ indices

Li Xia, Zaojian Zou, Zi-Hao Wang & Lu Zou
Ship’s sinkage, trim and resistance will increase when entering shallow waters. It is of great significance to investigate the squat of ship in shallow and confined navigation areas. However, there are many factors affecting the ship’s squat, such as speed of the ship, block coefficient, water depth and draught of the ship et al. In this paper, the contribution of these factors to the squat is measured in empirical formula models using Sobol’s indices which...

Student-FRIEndly extension to the TCP/IP protocol Suite

Koojana Kuladinithi & Asanga Udugama
Protocols of the TCP/IP protocol suite were designed solely to adapt to the technical changes in networks and devices, leaving out users' feelings. COVID-19 pandemic has shown us the necessity of including mechanisms in TCP/IP to support the context-sensitive human thought process, especially to serve pupils and students. This memo describes the student-FRIEndly TCP/IP protocol Suite (FRIES) that caters to the quick adaptation of TCP/IP to serve students in a virtual context. This mode of...

A segmentation scheme for CLF dynamic movement control applied to robotic handwriting

Patrick Göttsch, Robin Olschewski & Herbert Werner
Control Lyapunov Function - Dynamic Movement is a recently proposed imitation learning approach for controlling point-to-point movements. In this work some practical issues arising with this approach have been investigated by studying a particular application: robotic handwriting of German letters. One difficulty in this context is the handling of crossings. Here a novel segmentation scheme is proposed to eliminate crossings. Using a segmentation framework for splitting up the movement into a number of partial movements...

Controlling the large-scale fabrication of supraparticles

Alexander Plunkett, Catriona Eldridge, Gerold A. Schneider & Berta Domènech Garcia
Controlling the nanoscale interactions of colloidal building blocks is a key step for the transition from single nanoparticles to tailor-made, architected morphologies and their further integration into functional materials. Solvent evaporation-induced self-assembly within emulsion droplets emerges as a fast, versatile, and low-cost approach to obtain spherical, complex structures, such as supraparticles. Nevertheless, some process-structure relationships able to describe the effects of emulsion conditions on the synthesis outcomes still remain to be understood. Here, we explore...

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