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1
Content available Investigating the harbour basin tranquillity in the Genaveh Port development plan
Sharif Mahdi Bandizadeh, Gorbanpour Amir Hossein, Ghassemi Hassan, He Guanghua
Polish Maritime Research
|
2023
|
nr 1
145--155
EN
The Genaveh commercial port was placed on the agenda of the Iranian PMO (ports and maritime organization) to consider economic, commercial and residential development in Bushehr province and specifically in Genaveh city. In order to increase the water capacity of the port, it is necessary to build a new harbour basin for exploitation and commercial purposes at a depth of 5 to 6 meters by extending the existing jetties arms in front of the port. This research aims to investigate the harbour basin’s tranquillity for providing vessels with safe berthing. For this purpose, three modules, namely the flow model (FM), spectral wave (SW) and Boussinesq waves model (BW) from the MIKE 21 software package, were utilized. According to the monitoring data, which is provided by the Iranian PMO, the harbour basin’s tranquillity based on the prevailing wave directions was investigated. Based on the diffraction graph in the harbour basin, the results showed that, according to the percentage of permissible diffraction recommended by different valid regulations, there is a need to modify the geometry of the breakwater arms to increase the harbour basin’s tranquillity at the port in the development plan.
2
Content available Ship nonlinear roll motion identification using artificial neural network
Mousavi Seyed Mohamadreza, Khoogar Ahmad Reza, Ghassemi Hassan
Zeszyty Naukowe Akademii Morskiej w Szczecinie
|
2022
|
nr 72 (144)
65--74
EN
The solution of the nonlinear equation for a ship’s rotational motion around its longitudinal axis, even with simplifying assumptions, is complicated. This oscillatory motion, which is known as the roll motion, is generated when the ship sails in the waves, and the irregular behavior of the waves causes time-varying dynamics. Calculating the ship’s roll response is possible by determining roll equation coefficients. In the current study, the coefficients were determined from the dynamic response of the ship using a training feed-forward neural network. The training was carried out in two modes: as a free swing in calm water and forced oscillation in irregular waves. The DTMB 5415 vessel was selected as the case study ship. The results of the simulation by the neural network were validated by numerical analysis and model test results.
3
Content available Investigation into a hybrid mooring system with hydrodynamic response and mooring tension from a DeepCwind floating wind turbine
Ganjgani Arman Aghaei, Ghassemi Hassan, Ghiasi Mahmoud
Zeszyty Naukowe Akademii Morskiej w Szczecinie
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2022
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nr 71 (143)
11--21
EN
This paper investigates the effect of buoys and a clump weight on the mooring lines and the dynamic response of the floating platform. The full-scale of the OC4-DeepCwind semisubmersible FOWT platform is analyzed using the boundary element method (BEM) with ANSYS-AQWA software, when considering regular wave conditions. Platform motions and mooring line tension in the surge, heave, and pitch are presented and discussed in the time domain analyses (TDA) and frequency domain analyses (FDA). Validation is performed by compression of the platform motion RAO and the fairlead tension RAO magnitudes in the surge, heave, and pitch (for both numerical and experimental data) under seven sea states’ regular waves. The results show that increasing the number of buoys at a constant volume decreases the surge and pitch motion amplitude, while the heave motion increases slightly. Adding the buoy and clump weight (type 1) to the mooring line reduces the oscillation amplitude tension. In addition, raising the number of buoys increases the oscillation tension.
4
Content available DeepCwind semi-submersible floating offshore wind turbine platform with a nonlinear multi-segment catenary mooring line and intermediate buoy
Motallebi Mohammad, Ghassemi Hassan, Shokouhian Mehdi
Zeszyty Naukowe Akademii Morskiej w Szczecinie
|
2022
|
nr 69 (141)
20--34
EN
In this paper, to improve the mechanical behavior of DeepCwind semi-submersible floating offshore wind turbine (FOWT) platform mooring lines, the nonlinear catenary cables of the platform were divided into multi-segment and intermediate buoys. Mathematical formulations of the boundary element method (BEM) governing the dynamics of mooring line systems with buoy devices were described. This study was applied to the OC4-DeepCwind semi-submersible FOWT platform, which is designed for a 200-meter water depth with mooring lines consisting of three catenary steel chain cables at 120° angles to each other. The dynamic response of the multi-segment catenary mooring lines with different buoy radiuses and different positions along the cables was investigated. The full-scale platform was modeled in ANSYS-AQWA software, and the simulations were performed under harsh offshore conditions. The mooring line’s general arrangement, tension, strain and uplift force for different buoy radiuses and their position along the cable are presented and discussed. Moreover, platform motions in three directions (surge, heave, and pitch) were also analyzed. It was concluded that by correctly selecting the buoy volume and position along the cable, the tension of the cable may be reduced by up to 45%. By incorrectly selecting the buoy, the results caused adverse effects.
5
Content available Dynamic motions of the cabin mounted on the mono-hull planing boat using suspension system in waves
Bahrami Hassan, Ghassemi Hassan
Polish Maritime Research
|
2022
|
nr 1
13--25
EN
The necessity for higher speed and appropriate seakeeping performance of boats has led to extensive research. Hence, this research mainly discusses the optimal behavior of the boat against motions. From an economic point of view, reducing motions of the boat minimizes the damage caused by shock and vibration to the boat and equipment. Other benefits include comfort and safety and, as a result, improved human operating ability. Suspension systems are rarely used as motion controller in a boat. In multi-hull boats, the hull is an inseparable part of the vessels, so the wave will affect crew and equipment. This paper proposes and evaluates a novel concept boat equipped with a suspended cabin. The hull and superstructure (cabin) are separated in this new form by a simple passive suspension system. This study used numerical analysis to examine the seakeeping performance of the planing boat Fridsma model equipped with a passive suspension system under regular wave conditions. The hydrodynamics of the planing hull were modeled using commercial software, STAR-CCM+. For simulation of the passive suspension system between boat and cabin, MATLAB software was used. Results showed that the motion of the cabin, which is where the crew and equipment are located, decreased in regular waves.
6
Content available Vibration equations of the coupled torsional, longitudinal, and lateral vibrations of the propeller shaft at the ship stern
Firouzi Jabbar, Ghassemi Hassan, Vakilabadi Karim Akbari
Zeszyty Naukowe Akademii Morskiej w Szczecinie
|
2020
|
nr 61 (133)
121--129
EN
A propeller shaft generally experiences three linear forces and three moments, the most important of which are thrust, torque, and lateral forces (horizontal and vertical). Thus, we consider 4DOFs (degrees of freedom) of propeller shaft vibrations. This paper is presented to obtain the vibration equations of the various coupled vibrations of the propeller shaft at the stern of a ship (including coupled torsional-axial, torsional-lateral, axial-lateral, torsional-axial, and lateral vibrations). We focused on the added hydrodynamic forces (added mass and added damping forces) due to the location of the propeller behind the ship. In this regard, the 4DOFs of the coupled vibration (torsional-longitudinal and lateral vibrations in the horizontal and vertical directions) equations of shaft and propeller systems located behind a ship were extracted with and without added mass and damping forces. Also, the effect of mass eccentricity was considered on vibrations occurring at the rear of the ship.
7
Content available Calculating the second-order hydrodynamic force on fixed and floating tandem cylinders
Motallebi Mohammad, Ghafari Hamidreza, Ghassemi Hassan, Shokouhian Mehdi
Zeszyty Naukowe Akademii Morskiej w Szczecinie
|
2020
|
nr 62 (134)
108--115
EN
In this paper, the second-order hydrodynamic force on fixed and floating tandem cylinders has been calculated and different parameters have been taken into consideration. An incident wave is diffracted by the fixed cylinder, and as a result low-frequency waves radiate toward the floating cylinder and cause low-frequency second-order hydrodynamic forces to act on the surface of the floating cylinder. The interactions between the fixed and floating cylinders have been investigated by changing the distance between them, as well as the draft and radius of the floating cylinder. By employing perturbation series analysis over the wetted surface, the second-order wave excitation force has been calculated. The maximum force applied on the floating cylinder becomes non-dimensional when considering it with and without the fixed cylinder. The results showed the effect that the existence of the fixed cylinder had on the increase in the second-order forces is quite evident where, for a significant parameter of the floating cylinder, the force in the heave direction was enhanced by up to 1.55 times.
8
Content available Numerical investigation of the hydrodynamic performance of the propeller behind the ship with and without WED
Nadery Alireza, Ghassemi Hassan
Polish Maritime Research
|
2020
|
nr 4
50--59
EN
The presented paper numerically carries out the investigation of the hydrodynamic performance of the propeller behind the ship with and without wake equalizing duct (WED). It is mounted in front of the propeller in order to equalize the ship’s wake flow and improve the propeller performance. The computational fluid dynamics (CFD) analysis software STAR-CCM solver was adopted to simulate the KP505 propeller behind the KRISO container ship (KCS) using overlapping grid technology and user-defined functions. To obtain the effect of a –duct on propeller performance, the ship bare hull case, the with-propeller case, and the with-propeller-and-duct case are also computed. Together, these computations provide for a –complete CFD comparison of the duct effects. Also, the Taguchi design of the experiment method is applied to investigate three parameters (angle of attack, trailing edge radius, and chord length) of the duct. Finally, the main dimensions are obtained, and the thrust and torque coefficients are presented and discussed for one blade and whole blades during one cycle. Based on the numerical results, it is indicated that good design increases efficiency by 1.67%, and a –bad design may reduce efficiency by 3.25%. Also, the effect of the WED caused to decrease the pressure pulse by 35.9% in the face side of the propeller blade.
9
Content available Potential-based boundary element method to calculate the hydrodynamic drift force on the floating cylinder
Ghafari Hamidreza, Motallebi Mohammad, Ghassemi Hassan
Journal of Applied Mathematics and Computational Mechanics
|
2020
|
Vol. 19, nr 4
69--79
EN
This paper presents the calculation of the hydrodynamic drift force by using the potetial-based boundary element method (BEM). The potential theory and far-field wave drift forces solution will be described. The comparison of non-dimensional drift force for surge and heave motions are in good agreement between numerical and experimental data. The effect of different drafts and the radius of a cylinder on the drift forces (surge, heave and pitch) are presented and discussed.
10
Content available Power and thrust coefficients of the horizontal axis tidal stream turbine with different twist angles, blade numbers, and section profiles
Abbasi Alireza, Ghassemi Hassan, Molyneux David
Zeszyty Naukowe Akademii Morskiej w Szczecinie
|
2019
|
nr 57 (129)
11--20
EN
The purpose of this research was to investigate the power and thrust coefficients of a horizontal axis tidal stream turbine (HATST) with different blade geometries, including twist angles, blade numbers, and section profiles. The RANS equations and Star-CCM+ commercial software were used to numerically analyze these variables. Furthermore, the turbulence model used in this study is a Realisable k-ε turbulent model. Nine different models were defined by changing the twist angle, thickness, camber, and blade numbers. The results are presented, and the power and thrust coefficients are compared against TSR for each of the nine different models. The pressure distribution and flow velocity contour are also presented and discussed.
11
Content available Power performance of the combined monopile wind turbine and floating buoy with heave-type wave energy converter
Homayoun Esmaeil, Ghassemi Hassan, Ghafari Hamidreza
Polish Maritime Research
|
2019
|
nr 3
107--114
EN
This study deals with a new concept of near-shore combined renewable energy system which integrates a monopile wind turbine and a floating buoy with heave-type wave energy converter( WEC). Wave energy is absorbed by power-take-off (PTO) systems. Four different shapes of buoy model are selected for this study. Power performance in regular waves is calculated by using boundary element method in ANSYS-AQWA software in both time and frequency domains. This software is based on three-dimensional radiation/diffraction theory and Morison’s equation using mixture of panels and Morison elements for determining hydrodynamic loads. For validation of the approach the numerical results of the main dynamic responses of WEC in regular wave are compared with the available experimental data. The effects of the heaving buoy geometry on the main dynamic responses such as added mass, damping coefficient, heave motion, PTO damping force and mean power of various model shapes of WEC in regular waves with different periods, are compared and discussed. Comparison of the results showed that using WECs with a curvature inward in the bottom would absorb more energy from sea waves.
12
Content available Numerical investigation on the effects of obstruction and side ratio on non-Newtonian fluid flow behavior around a rectangular barrier
Noferesti Sara, Ghassemi Hassan, Nowruzi Hashem
Journal of Applied Mathematics and Computational Mechanics
|
2019
|
Vol. 18, nr 1
53--67
EN
In this paper, the characteristics of the flow and forced heat transfer of power law non-Newtonian fluids that flow around a quadrilateral and rectangular cylinder that are located in a 2D channel are investigated by use of the finite volume method (FVM) in a steady state flow regime. To this accomplishment, in the constant temperature, the effects of a different obstruction ratio, aspect ratio and Reynolds number are investigated. The Reynolds number in the range 5 ≤ Re ≤ 40, the power index in the range 0.5 ≤ n ≤ 1.4, the aspect ratio in the range 0.5 ≤ a ≤ 2, and the obstruction ratio in the range 0.125 ≤ b ≤ 0.5 were selected. By surveying the drag coefficient profiles, it’s concluded that as the obstruction ratio increases, the drag coefficient is increased, while an increase in the Reynolds number causes the lower drag coefficient. In addition, the drag coefficient is strongly increased by aspect ratio enhancements.
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