The Roll Damping of High-Speed Craft in Waves

2020 ◽  
Author(s):  
Oliviero Consolo ◽  
Lodewick Hillege ◽  
Matteo Bonci
Keyword(s):  
Mathematical Model ◽  
High Speed ◽  
Roll Angle ◽  
Irregular Waves ◽  
Lateral Component ◽  
Roll Damping ◽  
Head Waves ◽  
Hull Forms ◽  
Main Component ◽  
State Of Art

The main component of high-speed craft (HSC) roll damping is related to the hydrodynamic lift developed on the hull surface. This is very different from displacement type hull forms. However, the estimation of roll damping of HSC is often treated in the same manner as for larger and slower ships. Being able to model the roll of HSC correctly is of paramount importance in the prediction of the lateral component of acceleration of an impact at a roll angle in waves, or during a manoeuvre at high speed. These are phenomena that can have severe consequences on the comfort and safety of the crew on-board of HSC. Three procedures meant to estimate the HSC roll damping were analyzed. The outcomes of these procedures were compared in terms of roll and lateral accelerations statistics of HSC sailing in irregular waves. The HSC motions were predicted by a 2D+t mathematical model. Differently from the majority of the state-of-art HSC seakeeping tools, which focuses only on the vertical impacts in head waves, in this work the roll was included in the simulations. The numerical results of the simulations were validated by means of free sailing model tests at beam and quartering irregular seas carried out at the Seakeeping and Manoeuvring Basin of MARIN.

SUPERIOR SEAWORTHINESS OF A RESONANCE-FREE FAST OCEANGOING SWATH

2021 ◽  
Vol 156 (A4) ◽  
Author(s):  
M Yoshida ◽  
H Kihara ◽  
H Iwashita ◽  
M Kanda ◽  
T Kinoshita
Keyword(s):  
High Speed ◽  
Time Lag ◽  
Ship Motions ◽  
Speed Reduction ◽  
Small Water ◽  
Motion Responses ◽  
Head Waves ◽  
Unsteady Characteristics ◽  
Hull Forms ◽  
Heave Motion

The speed reduction, additional resistance or slamming caused by the large amplitude ship motions, should be completely restricted for a large fast oceangoing ship because of the strict time-punctuality and the high value of the cargo. A “Resonance-Free SWATH (RFS)”, which has negative restoring moments due to the extremely small water plane area, is introduced to minimize the motion responses. A motion control system using small fins is necessary for the RFS, which has no stability during high speed cruising. Theoretical estimations and experiments to search for the optimum values of PD control gains have been performed. Unsteady characteristics of fin-generated lift such as the time lag and the interaction among the fins and lower hulls have been measured and they are taken into account in the motion equations. Then, experiments using the RFS model with controlling fins have been carried out to validate the theoretical estimation for the motion responses of the RFS in waves. The theoretical and experimental results agree well with each other. The motion responses of the RFS in regular and irregular head waves are compared with those of other hull forms, such as a mono-hull, an ordinary SWATH and a trimaran. The clear advantage of the RFS regarding the seaworthiness has been found. In summary, the heave motion response of the RFS is reduced to 1/60 and the pitch motion becomes1/8, compared with those of the existing mono-hull ship.

AlGaN/GaN HEMTs: RECENT DEVELOPMENTS AND FUTURE DIRECTIONS

2008 ◽  
Vol 18 (04) ◽  
pp. 913-922 ◽  
Author(s):  
SIDDHARTH RAJAN ◽  
UMESH K. MISHRA ◽  
TOMÁS PALACIOS
Keyword(s):  
Field Effect ◽  
High Speed ◽  
Digital Circuits ◽  
Field Effect Transistors ◽  
Rf Power ◽  
Power Performance ◽  
Future Directions ◽  
Recent Developments ◽  
Gan Hemts ◽  
State Of Art

This paper provides an overview of recent work and future directions in Gallium Nitride transistor research. We discuss the present status of Ga -polar AlGaN / GaN HEMTs and the innovations that have led to record RF power performance. We describe the development of N -polar AlGaN / GaN HEMTs with microwave power performance comparable with state-of-art Ga -polar AlGaN / GaN HEMTs. Finally we will discuss how GaN -based field effect transistors could be promising for a less obvious application: low-power high-speed digital circuits.

Prediction of Surface Roughness in Compressed Air Jet Assisted High Speed End Milling of Silicon Using Diamond Coated Tools

2012 ◽  
Vol 576 ◽  
pp. 41-45
Author(s):  
A.K.M. Nurul Amin ◽  
M.A. Mahmud ◽  
M.D. Arif
Keyword(s):  
Mathematical Model ◽  
Surface Roughness ◽  
Surface Finish ◽  
High Speed ◽  
End Milling ◽  
Silicon Wafers ◽  
Compressed Air ◽  
Machining Parameters ◽  
High Quality ◽  
Ductile Mode

The majority of semiconductor devices are made up of silicon wafers. Manufacturing of high-quality silicon wafers includes numerous machining processes, including end milling. In order to end mill silicon to a nano-meteric surface finish, it is crucial to determine the effect of machining parameters, which influence the machining transition from brittle to ductile mode. Thus, this paper presents a novel experimental technique to study the effects of machining parameters in high speed end milling of silicon. The application of compressed air, in order to blow away the chips formed, is also investigated. The machining parameters’ ranges which facilitate the transition from brittle to ductile mode cutting as well as enable the attainment of high quality surface finish and integrity are identified. Mathematical model of the response parameter, the average surface roughness (Ra) is subsequently developed using RSM in terms of the machining parameters. The model was determined, by Analysis of Variance (ANOVA), to have a confidence level of 95%. The experimental results show that the developed mathematical model can effectively describe the performance indicators within the controlled limits of the factors that are being considered.

Research on the Performance Simulation of the Transmission System of Loader with Secondary Regulating Technique

2010 ◽  
Vol 426-427 ◽  
pp. 299-302
Author(s):  
Fa Ye Zang
Keyword(s):  
Mathematical Model ◽  
Fuzzy Control ◽  
Energy Saving ◽  
High Speed ◽  
Transmission System ◽  
Performance Simulation ◽  
Constant Torque ◽  
Braking Torque ◽  
The Mathematical Model ◽  
Inertial Energy

Based on deeply analyzing the working principles and energy-saving theory of loader secondary regulating transmission system, regenerating the transmission system’s inertial energy by controlling constant torque was put forward. Considering large changes of the parameters of the transmission system and its non-linearity, a fuzzy control was adopted to control the transmission system, and the mathematical model of the system was established, then the simulations of the performance of the transmission system has been conducted. The conclusion was made that the inertial energy can be reclaimed and reused in the system by the application of the secondary regulation technology, and braking by controlling constant torque is stable, it can ensure the security of braking at high speed and also permits changing the efficiency of recovery by changing the braking torque. The system’s power has been reduced and energy saving has been achieved.

SUBSTANTIATION OF OPTIMAL PARAMETERS AND DEVELOPMENT OF HIGH-TEMPERATURE STERILIZATION MODES FOR COMPOTE FROM PEARS IN HEATED AIR FLOW

2020 ◽  
Author(s):  
М.Э. Ахмедов ◽  
А.Ф. Демирова ◽  
Г.И. Касьянов ◽  
Ю.Ф. Росляков ◽  
М.М. Рахманова
Keyword(s):  
Mathematical Model ◽  
High Temperature ◽  
High Speed ◽  
Heat Transfer Fluid ◽  
Initial Product ◽  
Hot Air ◽  
Heated Air ◽  
Sterilization Process ◽  
Thermal Sterilization ◽  
Heat Carriers

Разработаны новые режимы стерилизации компота из груш в стеклотаре СКО 1-82-1000 с использованием высокотемпературных скоростных теплоносителей. Получена математическая модель расчета продолжительности процесса стерилизации в зависимости от параметров теплоносителя. Для получения математической модели использован метод математического планирования эксперимента. Предложен технологический прием ускоренной стерилизации компота из груш в стеклобанке объемом 1 дм3. Разработаны новые режимы тепловой обработки (стерилизации) компота из груш в стеклобанке 1-82-1000 при различных параметрах горячего воздуха и разных начальных температурах продукта, °С: 70, 80, 85 и 90. Наименьшая продолжительность процесса тепловой стерилизации достигнута при скорости теплоносителя 7,5 м/с при начальной температуре продукта 90°С. New modes of sterilization of compote from pears in glass containers of SKO 1-82-1000 using high-temperature high-speed heat carriers have been developed. A mathematical model for calculating the duration of the sterilization process depending on the parameters of the heat carrier is obtained. To obtain a mathematical model, we used the method of mathematical planning of the experiment. A technological method for accelerated sterilization of pear compote in a glass jar with a volume of 1 dm3 is proposed. The research made it possible to develop new modes of heat treatment (sterilization) of compote from pears in a glass jar 1-82-1000 at different parameters of hot air and different initial temperatures of the product, °C: 70, 80, 85 and 90. The shortest duration of the thermal sterilization process is achieved at the heat transfer fluid speed of 7,5 m/s at the initial product temperature of 90°C.

Increasing the mobility of a high-speed tracked vehicle based on a controlled skid algorithm

2020 ◽  
pp. 29-33
Author(s):  
S. V. Kondakov ◽  
O.O. Pavlovskaya ◽  
I.D. Ivanov ◽  
A.R. Ishbulatov
Keyword(s):  
Mathematical Model ◽  
Dynamic Stability ◽  
Simulation Modeling ◽  
Automatic System ◽  
High Speed ◽  
Control Algorithm ◽  
Loss Of Stability ◽  
Tracked Vehicle ◽  
Hydrostatic Transmission ◽  
The Mathematical Model

A method for controlling the curvilinear movement of a high-speed tracked vehicle in a skid without loss of stability is proposed. The mathematical model of the vehicle is refined. With the help of simulation modeling, a control algorithm is worked out when driving in a skid. The effectiveness of vehicle steering at high speed outside the skid is shown. Keywords: controlled skid, dynamic stability, steering pole displacement, hydrostatic transmission, automatic system, fuel supply. [email protected]

Study on Mathematical Model of High Speed Milling Force for Plastic Mold Steel 3Cr2Mo

2011 ◽  
Vol 291-294 ◽  
pp. 710-714
Author(s):  
Jun Min Xiao ◽  
Ying Xu
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
High Speed ◽  
High Hardness ◽  
Milling Force ◽  
High Speed Milling ◽  
Engineering Requirement ◽  
Practical Engineering ◽  
Cad Cam ◽  
Plastic Mold

Mold steel 3Cr2Mo has been used widely in manufacturing of plastic mold formed parts, owing to fine mechanical properties. However, it is also very difficult to cut mold formed parts of steel 3Cr2Mo due to high hardness. Ordinary NC cutting method of steel 3Cr2Mo is unable to relate to modern mold manufacturing due to bad cutting property, so it is extremely significant for improving cutting property of steel 3Cr2Mo to study the high speed milling technology. On the basis of improving the traditional cutting force formula, the mathematical model of high speed milling force for steel 3Cr2Mo was derived and solved by using the experimental data and constructing matrix equation based on MATLAB software. Comparing with experimental data, the error of mathematical model of high speed milling force could be controlled within 6 percent. Due to high precision the model of high speed milling force can meet practical engineering requirement and has great value in the fields of CAD/CAM/CAE.

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