Powering and Seakeeping Characteristics of a Displacement Vessel Hullform With Waterline Parabolization

2010 ◽  
Author(s):  
Kevin J. Gould ◽  
Sander M. Calisal ◽  
Jon Mikkelsen ◽  
O¨mer Go¨ren ◽  
Barbaros Okan ◽  
...  
Keyword(s):  
Design Procedure ◽  
Programming Algorithm ◽  
Wave System ◽  
Optimized Design ◽  
Added Resistance ◽  
Speed Reduction ◽  
Optimal Shapes ◽  
Seakeeping Performance ◽  
Strip Theory ◽  
Significant Difference

Waterline parabolization is a design procedure used for displacement vessels to decrease the wave resistance of the hullform through the addition of amidships bulbs. The bow and shoulder wave system of a parent hullform are interfered with by the wave system produced by the amidships bulb. Despite an overall increase in vessel beam, amidships bulbs can produce enough wave cancellations to decrease the total resistance. The designer must pay close attention to the amidships bulbs longitudinal positioning and fairing. Two design approaches can be taken: one the amidships bulbs are “retro-fit” to the existing parent hullform increasing the vessels displacement, and second the displacement is held constant producing an entirely new “optimized” design with shallower entrance and exit angles. Optimal shapes for the amidships bulbs were developed numerically using a potential flow code based on Dawson’s method coupled with a quasi-Newton nonlinear programming algorithm, Calisal et al. (2009a). Tow-tank tests at Istanbul Technical University (ITU) confirmed that amidships bulbs could reduce the effective power by 15%. Given a significant improvement in powering, this paper compares the seakeeping performance of the parent, optimized, and retro-fit hullforms at different sea state conditions and quantifies fuel consumption and acceleration levels. SHIPMO PC, a ship motion program based on strip theory is used to compare the three different hullforms. Three speeds are considered: the design speed of 12.5 knots, a reduced speed of 11 knots associated with the expected loss of speed from added resistance, and 6 knots to represent significant speed reduction. Roll, pitch and heave motions along with added resistance are estimated. Accelerations at the bridge are used to evaluate effects on the crew. For various sea states the most significant motion is roll in beam seas and is incurred at low speeds. The only significant difference in response between all models was for the retro-fit design; the increased displacement from adding the amidships bulbs and holding the draught constant increased the added resistance. Powering and acceleration levels for all models in head seas will be verified in tow-tank tests at ITU.

Added Resistance in Seaways and its Impact on Yacht Performance

2007 ◽  
Author(s):  
Kai Graf ◽  
Marcus Pelz ◽  
Volker Bertram ◽  
H. Söding
Keyword(s):  
Strong Impact ◽  
Wave Spectra ◽  
Linear Extensions ◽  
Added Resistance ◽  
Optimum Length ◽  
Prediction Program ◽  
Strip Theory ◽  
Velocity Prediction ◽  
Added Resistance In Waves ◽  
Response Amplitude Operators

A method for the prediction of seakeeping behaviour of sailing yachts has been developed. It is based on linear strip theory with some non-linear extensions. The method is capable to take into account heeling and yawing yacht hulls, yacht appendages and sails. The yacht's response amplitude operators (RAO) and added resistance in waves can be predicted for harmonic waves as well as for natural wave spectra. The method is used to study added resistance in seaways for ACC-V5 yachts of varying beam. Results are used for further VPP investigations. The AVPP velocity prediction program is used to study optimum length to beam ratio of the yachts depending on wind velocity and upwind to downwind weighting. This investigation is carried out for flat water conditions as well as for two typical wave spectra. The results show that taking into account added resistance in seaways has a strong impact on predicted performance of the yacht.

Electromagnetic Shock Absorbers for Automotive Suspensions: Electromechanical Design

2006 ◽  
Author(s):  
Nicola Amati ◽  
Aldo Canova ◽  
Fabio Cavalli ◽  
Stefano Carabelli ◽  
Andrea Festini ◽  
...  
Keyword(s):  
Shock Absorber ◽  
Dynamic Performance ◽  
Integrated Design ◽  
Design Procedure ◽  
Resistive Load ◽  
Added Resistance ◽  
Damping Force ◽  
Quarter Car Model ◽  
Car Model ◽  
Shock Absorbers

This article illustrates the modeling and design of electromechanical shock absorbers for automotive applications. Relative to the commonly used hydraulic shock absorbers, electromechanical ones are based on the use of linear or rotative electric motors. If electric motor is of the DC-brushless type, the shock absorber can be devised by shunting its electric terminals with a resistive load. The damping force can be modified by acting on the added resistance. An integrated design procedure of the electrical and mechanical parameters is presented in the article. The dynamic performance that can be obtained by a vehicle with electromechanical dampers is verified on a quarter car model.

INTEGRASI LITERASI INFORMASI PADA PENDIDIKAN DAN PELATIHAN JARAK JAUH PENDALAMAN MATERI BIOLOGI MADARASAH ALIYAH

2020 ◽  
Vol 10 (1) ◽  
pp. 1874
Author(s):  
Hikmawati Hanurani
Keyword(s):  
Religious Education ◽  
Information Literacy ◽  
Design Procedure ◽  
Literacy Skills ◽  
T Test ◽  
Distance Training ◽  
Significant Difference ◽  
Before And After ◽  
E Learning ◽  
The Subject

Abstract                                                                    This study aims to find out how the integration of information literacy substnce in distance training on biological substance for Madrasah Aliyah (MA) in improving information literacy skills in MA biology teachers. In this study the teacher participated in Distance  Training on MA biological material that was integrated with information literacy substance. The research sample consisted of 26 participants in Distance Training  in  Biology Substance for Biology Teacher Aliyah Madrasah in the Bandung Religious Education Training Center originating from the Ministry of Religion of West Java Province. The research design used was pre-experimental design with one group pretest-posttes design. The design procedure of this study was to take the 1st measurement on the subject (pretest) on the ability of mastery of information literacy, then the subject was treated for a certain period (exposure) through education and training in e-learning based distance training deepening of Biology Substance. The second measurement (posttest) was carried out after the treatment was given, and the prestest measurement results were compared with the results of the posttest measurements, using the t-test statistical test. Based on the t-test it can be concluded that "There is a significant difference in the results of self-assessment of information literacy between before and after doing Distance Learning Training".Abstrak                                                                     Penelitian ini bertujuan untuk mengetahui bagaimana integrasi materi literasi informasi pada kurikulum pendidikan dan pelatihan Diklat jarak jauh (DJJ) pendalaman materi biologi Madrasah Aliyah (MA) dalam meningkatkan keterampilan literasi informasi pada guru biologi MA.  Dalam penelitian ini guru mengikuti Diklat Jarak Jauh  Pendalaman materi biologi MA yang diintegrasikan dengan materi literasi informasi. Sampel penelitian berjumlah 26 orang peserta Diklat Jarak Jauh Teknis Substantif Pendalaman Materi Biologi Bagi Guru Biologi Madrasah Aliyah di Balai Diklat Keagamaan Bandung   yang berasal dari Lingkungan Kementerian Agama Provinsi Jawa Barat.   Desain penelitian yang digunakan adalah pre-eksperimental dengan desain One group pretest-posttes design. Prosedur desain penelitian ini adalah melakukan pengukuran ke-1 pada subyek (pretest) terhadap kemampuan penguasaan literasi informasi,  kemudian subjek diberi perlakuan untuk jangka waktu tertentu (exposure) melalui pendidikan dan pelatihan diklat jarak jauh pendalaman materi biologi MA berbasis e-learning yang terdiri dari tiga kegiatan belajar.  Pengukuran ke-2 (posttest) dilakukan setelah perlakuan diberikan, dan hasil pengukuran prestest dibandingan dengan hasil pengukuran posttest, menggunakan uji statistik Uji-t.  Berdasarkan uji-t dapat disimpulkan bahwa “Terdapat perbedaan yang signifikan hasil penilaian diri penguasaan literasi informasi  antara sebelum dan sesudah melakukan pembelajaran Diklat Jarak Jauh”

OPERATIONAL BEHAVIOUR OF AN OFFSHORE MULTIPURPOSE SUPPORT VESSEL IN THE EASTERN MEDITERRANEAN SEA

2021 ◽  
Vol 161 (A3) ◽  
Author(s):  
Y Garbatov ◽  
N Almany ◽  
M Tekgoz
Keyword(s):  
Mediterranean Sea ◽  
Eastern Mediterranean ◽  
Probabilistic Approach ◽  
Vertical Acceleration ◽  
Operational Mode ◽  
Wave Condition ◽  
Eastern Mediterranean Sea ◽  
Seakeeping Performance ◽  
Strip Theory ◽  
Operational Behaviour

The objective of this work is to analyse the operational behaviour of an offshore multipurpose support vessel designed to operate in the Eastern Mediterranean Sea. First, the seakeeping analysis is performed in a regular wave condition for different heading angles estimating heave and pitch motions through the strip theory. After that, the effects of the vertical acceleration on the bow, occurrence of slamming or hydrodynamic impact of the hull on the surface of the water; wetted deck, occurrence or invasion of water on the deck of the vessel and propeller emersion, motion sickness and wave-induced additional resistance are analysed. The present analysis is extended in an irregular sea condition, and the estimated seakeeping criteria are compared to the acceptable levels. In defining the most suitable operational mode of the offshore support vessels, multi-criteria decision techniques and probabilistic approach are employed to perform an adequate evaluation of the seakeeping performance accounting for different hazardous events through the service life.

NUMERICAL PREDICTION OF VERTICAL SHIP MOTIONS AND ADDED RESISTANCE

2021 ◽  
Vol 159 (A4) ◽  
Author(s):  
F Cakici ◽  
E Kahramanoglu ◽  
A D Alkan
Keyword(s):  
Deep Water ◽  
High Speed ◽  
Computer Experiments ◽  
Navier Stokes ◽  
Ship Motions ◽  
Added Resistance ◽  
Strip Theory ◽  
Head Waves ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method

Along with the development of computer technology, the capability of Computational Fluid Dynamics (CFD) to conduct ‘virtual computer experiments’ has increased. CFD tools have become the most important tools for researchers to deal with several complex problems. In this study, the viscous approach called URANS (Unsteady Reynolds Averaged Navier-Stokes) which has a fully non-linear base has been used to solve the vertical ship motions and added resistance problems in head waves. In the solution strategy, the FVM (Finite Volume Method) is used that enables numerical discretization. The ship model DTMB 5512 has been chosen for a series of computational studies at Fn=0.41 representing a high speed case. Firstly, by using CFD tools the TF (Transfer Function) graphs for the coupled heave- pitch motions in deep water have been generated and then comparisons have been made with IIHR (Iowa Institute of Hydraulic Research) experimental results and ordinary strip theory outputs. In the latter step, TF graphs of added resistance for deep water have been generated by using CFD and comparisons have been made only with strip theory.

Numerical Prediction of Vertical Ship Motions and Added Resistance

2017 ◽  
Vol 159 (A4) ◽  
Author(s):  
F Cakici ◽  
E Kahramanoglu ◽  
A D Alkan
Keyword(s):  
Deep Water ◽  
High Speed ◽  
Computer Experiments ◽  
Navier Stokes ◽  
Ship Motions ◽  
Added Resistance ◽  
Strip Theory ◽  
Head Waves ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method

Along with the development of computer technology, the capability of Computational Fluid Dynamics (CFD) to conduct ‘virtual computer experiments’ has increased. CFD tools have become the most important tools for researchers to deal with several complex problems. In this study, the viscous approach called URANS (Unsteady Reynolds Averaged Navier-Stokes) which has a fully non-linear base has been used to solve the vertical ship motions and added resistance problems in head waves. In the solution strategy, the FVM (Finite Volume Method) is used that enables numerical discretization. The ship model DTMB 5512 has been chosen for a series of computational studies at Fn=0.41 representing a high speed case. Firstly, by using CFD tools the TF (Transfer Function) graphs for the coupled heave-pitch motions in deep water have been generated and then comparisons have been made with IIHR (Iowa Institute of Hydraulic Research) experimental results and ordinary strip theory outputs. In the latter step, TF graphs of added resistance for deep water have been generated by using CFD and comparisons have been made only with strip theory.

Two-Step Optimization for Wind Turbine Blade With Probability Approach

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Ki-Hak Lee ◽  
Kyu-Hong Kim ◽  
Dong-Ho Lee ◽  
Kyung-Tae Lee ◽  
Jong-Po Park
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Design Space ◽  
Cost Model ◽  
Minimum Energy ◽  
Design Procedure ◽  
Wind Turbine Blade ◽  
Horizontal Axis Wind Turbine ◽  
Probability Approach ◽  
Strip Theory

A horizontal-axis wind turbine blade is designed using two step optimization procedures with probability approach. For the efficient management of the multiple design variables required for the blade design, the design procedure is divided into two optimization steps. In step 1, the diameter and rotating speed of a blade are determined and design points are extracted from the design space. In step 2-1, blade shapes are optimized by using the strip theory with the minimum energy loss method. The capacity factor and the cost model for each optimized blade shape are calculated in steps 2-2 and 2-3, respectively. To find the global optimum point in the design space, the space is modified into a highly possible region through the use of the probability approach.

Numerical Analysis of a Surface Ship in Waves

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Shawn Aram
Keyword(s):  
Stokes Equations ◽  
Body Motion ◽  
Irregular Waves ◽  
Design Stage ◽  
Fluid Viscosity ◽  
Sea Waves ◽  
Added Resistance ◽  
Physical Mechanisms ◽  
Strip Theory ◽  
Seakeeping Analysis

Abstract Ship's resistance and engine power to sustain ship's speed in seaways are augmented due to complex non-linear interactions between the ship and the ambient sea (waves). Ship designers, in early design stage, use an ad hoc "sea margin" to account for the effects of seaways in selecting propeller and engine. A numerical tool capable of accurately predicting added resistance and power of a ship cruising in waves would greatly help select its powering (margin) requirement and determine the optimal operating point that can maximize the energy efficiency. For seakeeping analysis, strip theory-based methods have long been used. More recently, nonlinear time-domain three-dimensional (3D) panel methods have started being used widely. A more physics-based avenue to seakeeping analysis is offered by coupled solutions of two-phase unsteady Reynolds-Averaged Navier-Stokes equations and six degrees-of-freedom rigid-body motion (RBM) equations. The URANS approach also avails itself of including the effects of propulsors, either explicitly or approximately. By accounting for all the nonlinear effects in hydrodynamic forces and moments and the resulting ship motions, and the effects of fluid viscosity and turbulence, the coupled URANS-RBM method is believed not only able to predict added resistance and speed loss more accurately, but also to provide valuable insights into the physical mechanisms underlying added resistance and power. The objectives of this study are: (1) to validate a coupled URANS-RBM solver developed for high-fidelity prediction of added resistance, speed loss and added power on ships cruising in regular head sea and irregular waves, and (2) to conduct a detailed analysis of the interactions among ship hull, propeller and waves for a 1/49 scaled model of the ONR Tumblehome (ONRT) (Model 5613) in order to shed light on the physical mechanisms leading to added resistance, speed loss and added power. Figure 1 depicts the ONRT self-propellers with two 4-bladed propellers in regular waves. The main flow features such as the free surface, the hub vortices and blade-tip vortices from the propeller, as well as vortices generated by the sonar dome, shafts, shaft brackets and bilge keels are captured.

Extension of the Stator Vane Upstream Across the 180° Bend for a Multistage Radial Compressor Stage

2009 ◽  
Author(s):  
Christian Aalburg ◽  
Alexander Simpson ◽  
Jorge Carretero ◽  
Tue Nguyen ◽  
Vittorio Michelassi
Keyword(s):  
Three Dimensional ◽  
Design Procedure ◽  
Design Parameters ◽  
Optimized Design ◽  
Angle Distribution ◽  
Conventional Design ◽  
Stator Vane ◽  
Limited Applicability ◽  
Return Channel ◽  
Vane Angle

The design, analysis and optimization of a new stator concept for multistage centrifugal compressors using numerical methods is presented. The first objective was to further improve the performance of a well-optimized stage with a short vaneless diffuser, see Aalburg et al [1]. The second objective was to achieve a significant increase in the flow turning in the stator part. In order to achieve these goals an extension of the return channel vane upstream, over the U-turn bend, was considered. This design poses challenges that are quite different from those encountered for a conventional design. For example, a conventional vane angle distribution leads to lean angles across the bend that are not feasible from a manufacturing and aerodynamic perspective. In addition, conventional design tools for geometry generation were found to have limited applicability for this concept. To address these issues a geometry generator was developed that facilitated the design of three-dimensional across-the-bend type vanes with unconventional vane angle distributions. The geometry generator was based on an analytical design procedure similar to that outlined by Veress and Braembussche [2]. This procedure allows a desired loading distribution to be specified. In this paper the vane concept will be introduced, the development of the geometry generator will be outlined and the effect of varying design parameters will be considered. An optimized design will then be presented that outperformed the reference conventional design in terms of efficiency by up to one point across the operating range. This improvement was achieved despite a significantly higher vane loading.

Long-Term Prediction of Speed Reduction Due to Waves and Fuel Consumption of a Ship at Actual Seas

2010 ◽  
Author(s):  
Pei Yuan Feng ◽  
Ning Ma ◽  
Xie Chong Gu
Keyword(s):  
Fuel Consumption ◽  
Added Resistance ◽  
Ocean Engineering ◽  
Speed Reduction ◽  
Short Term Result ◽  
Propulsive Performance ◽  
Term Prediction ◽  
Long Term Prediction ◽  
Actual Seas

The improvement of ship motion and propulsive performance becomes vital in various ocean engineering applications. As the notion of energy saving and environmental protection gradually finds its way deep into people’s heart, the issue of energy efficient design and operation of the vessels has attracted more and more attentions. How to make the vessels maintain service speed while consuming less fuel has quickly become the main concern of the naval architects. In this paper, we present a new procedure to predict speed reduction and fuel consumption of a ship at actual seas. The prediction takes into account the added resistance due to waves since it is recognized to be the predominant component, while wind resistance, fouling effect and other resistance components are relatively small and temporarily ignored. The calculation of the added resistance is based on a three-dimensional frequency-domain panel method for regular waves and spectral approach is applied to obtain the mean value. Then speed prediction is performed based on a simplified model assuming the balanced working point among the ship, propeller and the engine under the assumption of linear relationship between the engine torque and its rotation. Fuel consumption prediction is carried out through calculating the engine power, the effective fuel consumption rate and the time for sailing. Long-term prediction is made through combining the short-term result with the long-term ocean wave statistics from the Database of Winds and Waves which is newly developed in Shanghai Jiao Tong University (SJTU). A long-term probability model which takes into account the ship’s actual navigation conditions is applied, and the expected ship speed and fuel consumption along her actual sea route are predicted accordingly. For the purposed of practical use, a VLCC ship type is adopted for the prediction as an example. Finally, it has been concluded that the propulsive performance, i.e. speed and fuel consumption, of the vessel at actual seas can be improved through design considerations such as hull form optimization, engine selection and weather routing.

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