490 Works

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...

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...

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...

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...

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...

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....

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...

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...

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...

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...

Collective orientational order and phase behavior of a discotic liquid crystal under nanoscale confinement

Arda Yildirim, Kathrin Sentker, Glen Jacob Smales, Brian Richard Pauw, Patrick Huber & Andreas Schönhals
The phase behavior and molecular ordering of hexakishexyloxy triphenylene (HAT6) DLCs under cylindrical nanoconfinement are studied utilizing differential scanning calorimetry (DSC) and dielectric spectroscopy (DS), where cylindrical nanoconfinement is established through embedding HAT6 into the nanopores of anodic aluminum oxide (AAO) membranes, and a silica membrane with pore diameters ranging from 161 nm down to 12 nm. Both unmodified and modified pore walls were considered. In the latter case the pore walls of AAO membranes...

Das Methodenkonzept \"Vom Nowland zum Nextland\" : zur pro-aktiven Mitgestaltung digitaler Transformationen in Organisationen

Vanessa Päplow, Ronny Röwert, Tina Jessica Ladwig & Henning Klaffke
Der digitale Strukturwandel stellt Unternehmen vor große Herausforderungen. Diese komplexen Herausforderungen zu beschreiben und dabei die richtigen Begriffe und Konzepte zu verwenden ist meist sehr schwierig. Das hier vorgestellte Methodenkonzept zur Gestaltung des Strukturwandels gibt den Akteur:innen Bilder und Symbole an die Hand, um die Veränderungen vereinfacht zu beschreiben und mögliche Wege zur Transformation aufzuzeigen.

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...

Data for characterizing devolatilized wood pellets for fluidized bed applications

Kolja Jarolin, Shen Wang, Timo Dymala, Tao Song, Stefan Heinrich, Laihong Shen & Maksym Dosta
This dataset was used to characterize devolatilized wood pellets for fluidized bed applications. The results and the details about the methodology are presented in "Jarolin, K.; Wang, S.; Dymala, T.; Song, T.; Heinrich, S.; Shen, L.; Dosta, M. (2021): Characterizing devolatilized wood pellets for fluidized bed applications. In: Biomass Conversion and Biorefinery." In this work, three types of wood pellets, called Type A (white sawdust pellet from spruce wood), Type B (brown sawdust pellet from...

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...

HOOU@TUHH Erfahrungen und Erfolge 2018/2019

Tina Jessica Ladwig, Ann-Kathrin Watolla, Dorothee Schielein, Axel Dürkop, Stephan Dublasky, Philip Busch, Christin Burkhardt, Jennifer Lehmann, Gesine Liese, Henning Haschke, Florian Hagen, Ruth Schaldach & Lars Schmeink
In den Jahren 2018 und 2019 wurden 7 Projekte im Rahmen der Hamburg Open Online University (HOOU) an der TUHH gefördert und umgesetzt. Die projektspezifischen Erfahrungen und Erfolge werden in dieser Broschüre zusammenfassend dargestellt.

Modelling the flood attenuation of combined SUDS in urban areas

Claudia Brüning, Erik Pasche, Sandra Hellmers, Natasa Manojlovic & Niloufar Behzadnia
The assessment of the effectiveness of Flood Probability Reduction Measures such as Sustainable Drainage Systems (SUDS) is not systematically verified and their practice is not well established yet. The objective of this paper is to quantify and model the hydrologic effects of combined SUDS elements on the catchment level of urban areas at extreme storm events with a new integrative method. The theoretical concept aims at high level of physical soundness and level of detail,...

Mapping of multiple linked green infrastructure systems in rainfall-runoff models

Sandra Hellmers, Gernot Belger & Peter Fröhle
In this paper, the development of a theoretical approach to integrate green infrastructures in catchment based model discretisation as well as its implementation in a conceptual semi-distributed rainfall-runoff model (RRM) is presented. This model type has been distinguished as most promising related to model application in practice. The approach integrates the differentiated description of sustainable urban drainage systems (SUDS) as polygon geometries overlaying the basic data of a catchment. These overlays are defined with an...

Optimisation of rainfall-runoff modelling for urban flood management with ensemble radar nowcasts

Sandra Hellmers, Alexander Strehz, Nina Sophie Leese, Thomas Einfalt & Peter Fröhle
Especially in urban areas, improved strategies are required to assess the influence of small scale precipitation patterns of local heavy rainfall events in a flood warning context. The results of the case study show a wide range of possible precipitation scenarios given by the radar nowcast ensemble members for a local rainfall event. This reflects the large uncertainty in predicting discharge curves. The first steps of the project StucK (2015 till 2018) are presented here:...

Using particle swarm optimization for source seeking in multi-agent systems

Marcus Gronemeyer, Marcus Bartels, Herbert Werner & Joachim Horn
This paper presents a novel approach to the source seeking problem, where a group of mobile agents tries to locate the maximum of a scalar field defined on the space in which they are moving. The agents know their position and the local value of the field, and by communicating with their neighbors estimate the gradient direction of the field. A distributed cooperative control scheme is then designed that drives the group towards the maximum...

Constrained predictive control of a robotic manipulator using quasi-LPV representations

Pablo S. G. Cisneros, Aadithyan Sridharan & Herbert Werner
In this paper a practical approach to Nonlinear Model Predictive Control (NMPC) of a robotic manipulator subject to nonlinear state constraints is presented, which leads to a successful experimental implementation of the control algorithm. The use of quasi-LPV modelling is at the core of this scheme as complex nonlinear optimization is replaced by efficient Quadratic Programming (QP) exploiting the quasi-linearity of the resulting model and constraints. The quasi-LPV model is obtained via velocity-based linearization which...

Nonlinear flatness-based control of driveline oscillations for a powertrain with backlash traversing

Hong Truc Pham, Robert Seifried, Andreas Hock & Christian Scholz
Load changes in automotive powertrains may cause uncomfortable vibrations during vehicle acceleration. These driveline oscillations occur due to flexible and underdamped shafts. Furthermore, backlashes in the drive train represent hard nonlinearities and lead to challenges in control. Reducing vibration only by feedback control may destabilize the closed loop due to time delays in the powertrain system. This paper proposes a flatness-based feedforward control law based on a two-mass powertrain model with backlash to compensate oscillations....

Development of a design education platform for an interdisciplinary teaching concept

Emil Heyden, Jan Küchenhof, Erik Greve & Dieter Krause
Teams of engineering students take part in a problem-based learning course, where they develop physical product variants of a robotic system and take part in a competition. Design theory and methodology are part of the teaching concept, including complexity management by platform strategy and modularization. Skills in mechanical engineering, design, numerical optimization, additive manufacturing and use of CAD, PDM and FEM software are improved. The developed robotic systems are divided into different modules, these modules...

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