Study the influence of ship length ratio on ship to ship interaction on moving in parallel on their hydrodynamic characteristics

2021 ◽  
pp. 61-66
Author(s):  
Р. Али ◽  
Н.В. Тряскин
Keyword(s):  
Hydrodynamic Interaction ◽  
Turbulence Modeling ◽  
Relative Length ◽  
Velocity Fields ◽  
Length Ratio ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Turbulent Model ◽  
Calm Water ◽  
Good Agreement

Суда в некоторых случаях эксплуатации могут двигаться в непосредственной близости друг от друга. Такой сценарий обычно связан с изменением полей давления и скорости вблизи корпуса судов, в результате чего возникают гидродинамические силы и моменты взаимодействия, которые сильно зависит от относительной длины. В этой статье была проведена серия систематических расчётов на двух корпусах KVLCC2, движущихся на большой глубине в безветренную погоду с одинаковой постоянной малой скоростью, не превышающей 4 уз., чтобы исследовать влияние отношения длин на силы и моменты гидродинамического взаимодействия. OpenFOAM, пакет CFD с открытым исходным кодом использовался для организации и проведения расчётов. Метод осреднения по Рейнольдсу уравнений Навье-Стокса (RANS) применялся для моделирования турбулентности. Хорошо известная модель турбулентности использовалась для замыкания уравнений Навье-Стокса. Числовые результаты, касающиеся поля скоростей и гидродинамического следа за судами, были обработаны, проанализированы, сопоставлены и показали хорошее согласование с экспериментальными результатами. Ships, during the lightering operations, are forced to sail in a close position to each other, such a scenario generally associates with a change in the pressure and velocity fields surrounding their hulls, as a result, interaction hydrodynamic forces and moments are generated which are strongly related to the relative length of the interacted ships. In this paper, a series of systematic computations were performed on two KVLCС2 hulls advancing in deep and calm water with the same constant low speed (full scale speed 4kt) in order to investigate the influence of the length ratio on the hydrodynamic interaction forces and moments during the lightering operation. OpenFOAM, an open-source CFD packet was used for carrying out the simulations, Reynolds Averaged Navier-Stokes (RANS) method was used for turbulence modeling and the well-known turbulent model k-ω SST was used to close RANS equations. Numerical results have been post-processed, analyzed, compared and found to be of a good agreement with the experimental results. The velocity fields and wake were presented and analyzed.

scholarly journals Study the influence of the relative position of two vessels moving in parallel on their hydrodynamic characteristics

2020 ◽  
pp. 59-65
Author(s):  
Р. Али ◽  
Н.В. Тряскин
Keyword(s):  
Deep Water ◽  
Hydrodynamic Interaction ◽  
Turbulence Modeling ◽  
Hydrodynamic Characteristics ◽  
Rigid Boundary ◽  
Pressure Fields ◽  
Close Proximity ◽  
Calm Weather ◽  
Longitudinal Position ◽  
Good Agreement

Эксплуатация судна сопровождается ситуациями, в которых оно испытывает дополнительные нагрузки от близости твёрдых границ, таких как плавание в ограниченном фарватере, расхождение судов на малых расстояниях, погрузочные операции. Для грамотного осуществления подобных операций необходима заблаговременная оценка возможные нагрузок и учёт гидродинамического влияния между судами или судном и твёрдой поверхностью. Целью данной работы является изучение влияния взаимного положения двух судов на гидродинамическое взаимодействие между ними, а также оценка возможного взаимодействия между судами при операциях погрузки/разгрузки на глубокой воде. Гидродинамическое взаимодействие выражается в изменении полей давления и скорости при непосредственной близости нескольких судов, изменении поперечной и продольной гидродинамических сил и моментов рыскания, действующих на оба объекта. Для определения влияния относительных расстояний между судами на их гидродинамическое взаимодействие во время разгрузочных операций проведён ряд численных экспериментов. Смоделировано обтекание потоком вязкой несжимаемой жидкости двух судов типа KVLCС2, находящихся на различных относительных расстояниях друг от друга. Математическое моделирование турбулентного потока основано на решении уравнений Рейнольдса и проведено с помощью открытого программного пакета OpenFOAM. Для моделирования турбулентности использована модель турбулентности. Результаты численного моделирования обработаны и проанализированы, они находятся в хорошем соответствии с экспериментальными данными. Вычислены максимальные силы и моменты, возникающие при взаимодействии судов при их различном взаимном положении. Hydrodynamic interaction between ships continues to be a major field of research, considering that during different stages of the investment ship’s life, ship is exposed to the presence of a close rigid boundary such as sailing in restricted areas, overtaking and encountering at small distances with other ship or during investment operation such as lightering operations. In order to perform lightering operations safely, the knowledge of the interaction effects between both ships is very important. The aim of this article is to study the changes in velocity and pressure fields resulting from the presence of the two ships in close proximity, evaluating the longitudinal and transverse forces as well as yaw momentum affecting both ships, determining their relationship to the relative longitudinal position of the two ships as well as to predict the ship-to-ship interaction during lightering operations in deep water. A series of systematic computations were performed on two KVLCC2 hulls advancing in deep water and calm weather with the same constant low speed (full scale speed 4kt) in order to investigate the influence of the relative longitudinal separations on the hydrodynamic interaction forces and moments during the lightering operation. OpenFOAM, an open-source CFD packet was used for carrying out the simulations, RANS method was used for turbulence modeling and the well-known turbulent model was used to close RANS equations. Numerical results have been post-processed, analyzed, compared and found to be of a good agreement with the experimental results. Maximum forces and moments and their relation with longitudinal position were computed.

Numerical evaluation of hydrodynamic characteristics of planing hulls by using a hybrid method

2021 ◽  
pp. 147509022199024
Author(s):  
Emre Kahramanoglu ◽  
Silvia Pennino ◽  
Huseyin Yilmaz
Keyword(s):  
Experimental Data ◽  
Hybrid Method ◽  
Design Stage ◽  
Hydrodynamic Characteristics ◽  
Calm Water ◽  
Preliminary Design Stage ◽  
Reduction Function ◽  
Hull Forms ◽  
Good Agreement

The hydrodynamic characteristics of the planing hulls in particular at the planing regime are completely different from the conventional hull forms and the determination of these characteristics is more complicated. In the present study, calm water hydrodynamic characteristics of planing hulls are investigated using a hybrid method. The hybrid method combines the dynamic trim and sinkage from the Zarnick approach with the Savitsky method in order to calculate the total resistance of the planing hull. Since the obtained dynamic trim and sinkage values by using the original Zarnick approach are not in good agreement with experimental data, an improvement is applied to the hybrid method using a reduction function proposed by Garme. The numerical results obtained by the hybrid and improved hybrid method are compared with each other and available experimental data. The results indicate that the improved hybrid method gives better results compared to the hybrid method, especially for the dynamic trim and resistance. Although the results have some discrepancies with experimental data in terms of resistance, trim and sinkage, the improved hybrid method becomes appealing particularly for the preliminary design stage of the planing hulls.

scholarly journals Numerical Simulation Analysis of Cavitation Performance of Tandem Propeller

2018 ◽  
Vol 36 (3) ◽  
pp. 509-515 ◽  
Author(s):  
Xiaoxu Du ◽  
Zhengdong Zhang
Keyword(s):  
Numerical Simulation ◽  
Simulation Analysis ◽  
Cavitation Number ◽  
Hydrodynamic Characteristics ◽  
Turbulent Model ◽  
Cavitation Model ◽  
Cavitation Phenomenon ◽  
Cavitation Performance ◽  
Simulation Results ◽  
Good Agreement

The steady non cavitation hydrodynamic characteristics of CLB4-55-1 tandem propeller and the steady cavitation flows of NACA66 hydrofoil are numerically studied firstly based on the RANS equations of homogeneous multiphase using CFD theory, combined with the SST k-ω turbulent model and Z-G-B cavitation model. Numerical simulation results are in good agreement with the experimental results, which indicates that the numerical method is reliable and accurate. Then, the cavitation performance of the tandem propeller are numerical simulated and analyzed. The results show that the computational model can predict the cavitation performance of tandem propeller accurately. The cavitation performance of tandem propeller is nearly the same as single propeller, however, the cavitation phenomenon of back propeller is greater than the head propeller at certain advance coefficient and cavitation number. The cavitation phenomenon will disappear with the increase of the advance coefficient or the cavitation number.

scholarly journals Numerical Simulations for the Wake Prediction of a Marine Propeller in Straight-Ahead Flow and Oblique Flow

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
E. Guilmineau ◽  
G. B. Deng ◽  
A. Leroyer ◽  
P. Queutey ◽  
M. Visonneau ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Open Water ◽  
Numerical Code ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Marine Propeller ◽  
Oblique Flow ◽  
Les Model ◽  
Straight Ahead ◽  
Good Agreement

This paper presents the capability of a numerical code, isis-cfd, based on the solution of the Navier–Stokes equations, for the investigation on the hydrodynamic characteristics of a marine propeller in open water. Two propellers are investigated: the Istituto Nazionale per Studi ed Esperienze di Architectura Navale (INSEAN) E779A model in straight-ahead flow and the Potsdam Propeller Test Case (PPTC) model in oblique flow. The objectives of this study are to establish capabilities of various turbulent closures to predict the wake propeller and to predict the instability processes in the wake if it exists. Two Reynolds-averaged Navier–Stokes (RANS) models are used: the k–ω shear stress transport (SST) of Menter and an anisotropic two-equation explicit algebraic Reynolds stress model (EARSM). A hybrid RANS–large eddy simulation (LES) model is also used. Computational results for global flow quantities are discussed and compared with experimental data. These quantities are in good agreement with the measured data. The hybrid RANS–LES model allows to capture the evolution of the tip vortices. For the INSEAN E779A model, the instability of the wake is only predicted with a hybrid RANS–LES model, and the position of these instabilities is in good agreement with the experimental visualizations.

A Navier-Stokes Analysis of the Stall Flutter Characteristics of the Buffum Cascade

2000 ◽  
Author(s):  
Stefan Weber ◽  
Max F. Platzer
Keyword(s):  
Mach Number ◽  
Turbulence Modeling ◽  
Separation Bubble ◽  
Leading Edge ◽  
Navier Stokes ◽  
Implicit Time ◽  
Fully Implicit ◽  
High Incidence ◽  
Stall Flutter ◽  
Good Agreement

Numerical stall flutter prediction methods are highly needed as modern jet engines require blade designs close to the stability boundaries of the performance map. A Quasi-3D Navier-Stokes code is used to analyze the flow over the oscillating cascade designed and manufactured by Pratt & Whitney, and studied at the NASA Glenn Research Center by Buffum et al. The numerical method solves for the governing equations with a fully implicit time-marching technique in a single passage by making use of a direct-store, periodic boundary condition. For turbulence modeling the Baldwin-Lomax model is used. To account for transition, the criterion to predict the onset location suggested by Baldwin and Lomax is incorporated. Buffum et al. investigated two incidence cases for three different Mach numbers. The low-incidence case at a Mach number of 0.5 exhibited the formation of small separation bubbles at reduced oscillation frequencies of 0.8 and 1.2. For this case the present approach yielded good agreement with the steady and oscillatory measurements. At high-incidence at the same Mach number of 0.5 the measured steady-state pressure distribution and the separation bubble on the upper surface was also found in good agreement with the experiment. But computations for oscillations at high-incidence failed to predict the negative damping contribution caused by the leading edge separation.

A Navier–Stokes Analysis of the Stall Flutter Characteristics of the Buffum Cascade

2000 ◽  
Vol 122 (4) ◽  
pp. 769-776 ◽  
Author(s):  
Stefan Weber ◽  
Max F. Platzer
Keyword(s):  
Mach Number ◽  
Turbulence Modeling ◽  
Separation Bubble ◽  
Leading Edge ◽  
Navier Stokes ◽  
Implicit Time ◽  
Fully Implicit ◽  
High Incidence ◽  
Stall Flutter ◽  
Good Agreement

Numerical stall flutter prediction methods are much needed, as modern jet engines require blade designs close to the stability boundaries of the performance map. A Quasi-3D Navier–Stokes code is used to analyze the flow over the oscillating cascade designed and manufactured by Pratt & Whitney, and studied at the NASA Glenn Research Center by Buffum et al. The numerical method solves for the governing equations with a fully implicit time-marching technique in a single passage by making use of a direct-store, periodic boundary condition. For turbulence modeling, the Baldwin–Lomax model is used. To account for transition, the criterion to predict the onset location suggested by Baldwin and Lomax is incorporated. Buffum et al. investigated two incidence cases for three different Mach numbers. The low-incidence case at a Mach number of 0.5 exhibited the formation of small separation bubbles at reduced oscillation frequencies of 0.8 and 1.2. For this case the present approach yielded good agreement with the steady and oscillatory measurements. At high incidence at the same Mach number of 0.5 the measured steady-state pressure distribution and the separation bubble on the upper surface was also found in good agreement with the experiment. But computations for oscillations at high incidence failed to predict the negative damping contribution caused by the leading edge separation. [S0889-504X(00)01304-0]

scholarly journals Application of an alternative mesh morphing method on the numerical modeling of oscillating wave surge converters

RBRH ◽  
2019 ◽  
Vol 24 ◽  
Author(s):  
Guilherme Fuhrmeister Vargas ◽  
Edith Beatriz Camaño Schettini
Keyword(s):  
Numerical Modeling ◽  
Turbulence Modeling ◽  
Experimental Studies ◽  
Ocean Waves ◽  
Navier Stokes ◽  
Ocean Bottom ◽  
Mesh Morphing ◽  
Wave Energy Converters ◽  
Relative Differences ◽  
Good Agreement

ABSTRACT A technology capable of converting the horizontal motion of the ocean waves into energy by the application of a flap-piston system has been improved over the last few years, this device is known as oscillating wave surge converter. This system has great potential, already proven, for electric power generation. The computational fluid dynamics is one of the most used tools for the study of wave energy converters. In this context, the present paper proposes the application of an alternative mesh morphing method to represent the hydrodynamics of these devices, which is based on a bottom that oscillates with the converter, leading the flap to reach high inclinations without causing numerical divergences. The study is performed using the OpenFOAM computational code and its extension OLAFOAM. These are based on Reynolds Average Navier Stokes (RANS) turbulence modeling and the Volume of Fluid method (VOF) for the free surface representation, which are applied to a bidimensional model, allowing the numerical modeling of the converter. The proposed method presented good agreement of the results when compared to the experimental studies in similar hydrodynamic cases. The methodology based on a moving bottom presented relative differences, concerning the method that considers the bottom as fixed, between 4% and 17% for the cases where the flap is near to the ocean bottom and up to 8% for cases where it is further away.

scholarly journals NUMERICAL INVESTIGATION OF INTERCEPTOR EFFECT ON SEA KEEPING BEHAVIOUR OF PLANING HULL ADVANCING IN REGULAR HEAD WAVES

Brodogradnja ◽  
2021 ◽  
Vol 72 (2) ◽  
pp. 73-92
Author(s):  
Jangam Suneela ◽  
◽  
Prasanta Sahoo ◽  
Keyword(s):  
Numerical Data ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Head Waves ◽  
Calm Water ◽  
Vessel Response ◽  
Planing Vessel ◽  
Motion Characteristics ◽  
The Impact ◽  
Regular Head Waves

In this paper an attempt has been made to assess the capability of numerical algorithm based on Reynolds Averaged Navier Stokes (RANS) for predicting the motion characteristics of the planing hull in calm water and regular waves. The focus of the present study is the impact of interceptors on the sea keeping quality of a planing vessel investigated through the application of numerical methods. The wave properties such as wavelength and wave height are taken into consideration to investigate the effect of wave steepness on vessel response. It is found that numerical data can efficiently simulate the motion attitude and the hydrodynamic characteristics of planing craft in regular head waves. The planing hull with and without interceptor fitted at the transom is simulated in numerical wave tank. The results show reduction in heave and pitch motions which gave favorable sea keeping behavior for the hull fitted with interceptor. The numerical solution is useful for the preliminary prediction of navigation safety during sailing.

scholarly journals Propeller Hydrodynamic Characteristics in Oblique Flow by Unsteady Ranse Solver

2020 ◽  
Vol 27 (1) ◽  
pp. 6-17
Author(s):  
Hossein Nouroozi ◽  
Hamid Zeraatgar
Keyword(s):  
Numerical Method ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Time Step ◽  
Sliding Mesh ◽  
Oblique Flow ◽  
Ranse Solver ◽  
Ship Performance ◽  
Thrust And Torque ◽  
Good Agreement

AbstractPropellers may encounter oblique flow during operation in off-design conditions. Study of this issue is important from the design and ship performance points of view. On the other hand, a propeller operating in oblique flow may sometimes result in a better propulsion efficiency. The main goal of the present study is to provide an insight on the propeller characteristics in the oblique flow condition. In this research, the performance of the DTMB 4419 propeller is studied by the numerical method based on solving Reynolds Averaged Navier–Stokes (RANS) equations in several inflow angles. The sliding mesh approach is used to model the rotary motion of the propeller. Initially, the numerical method is verified by grid and time step dependency analysis at various inflow angles. Additionally, computed results at zero inflow angle are compared with the available experimental data and good agreement is achieved. Finally, the forces and moments acting on the propeller are obtained for 0° to 30° inflow angles. It is concluded that the inflow angle up to 10° has no significant influence on the thrust and torque coefficients as well as the propeller efficiency. However, at high angles up to 30°, the thrust and torque coefficients increase as the inflow angle increases, which may result in a significant improvement of propeller efficiency.

scholarly journals Numerical Analysis on Hydrodynamic Characteristics of Surface Piercing Propellers in Oblique Flow

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2015
Author(s):  
Ren ◽  
Hua ◽  
Ji
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Analysis ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Planing Craft ◽  
Sliding Mesh ◽  
Oblique Flow ◽  
Thrust And Torque ◽  
Good Agreement

When a planing boat sails at the free surface, the posture changes drastically with time, so the surface piercing propellers usually work in oblique flow. In this paper, numerical simulations are performed to predict the performance of PSP-841B with Unsteady Reynolds Averaged Navier–Stokes (URANS) method coupling with sliding mesh and volume of fluid (VOF) method. The results show that the predicted thrust and torque coefficients of PSP-841B are in good agreement with the experimental data. It proves the present numerical schemes are feasible and validated. These schemes are applied in the simulations of SPP-1 that is installed to a planing craft. In oblique flow, the ventilation volume of SPP-1 increases dramatically, resulting in the postponed transition of vented status that changes from the fully dry to partially wetted; at the low advance ratios, the thrust and torque coefficients are less than that in the horizontal case. As the advance speed increases, the vented mode of SPP-1 varies from full ventilation to partially wet, and the forces and moments get closer to the results in the horizontal flow. In addition, the blockage effect of air cavity to the inflow in oblique flow is more significant than the results in the horizontal case.

Sign in / Sign up

Export Citation Format

Share Document