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Experimental study of a tanker ship squat in shallow water
, Article Jurnal Teknologi (Sciences and Engineering) ; Vol. 66, Issue. 2 , 2014 , pp. 15-20 ; ISSN: 01279696 ; Seif, M. S ; Sharif University of Technology
Abstract
One of the phenomena restricting the tanker navigation in shallow waters is reduction of under keel clearance in the terms of sinkage and dynamic trim that is called squatting. According to the complexity of flow around ship hull, one of the best methods to predict the ship squat is experimental approach based on model tests in the towing tank. In this study model tests for tanker ship model had been held in the towing tank and squat of the model are measured and analyzed. Based on experimental results suitable formulae for prediction of these types of ship squat in fairways are obtained
Experimental and Numerical Investigation the Effect of Geometry on Hydrodynamic Performance in Surface Piercing Propeller
, Ph.D. Dissertation Sharif University of Technology ; Seif, Mohammad Saeed (Supervisor)
Abstract
Due to the suitable performance characteristics and the widespread use of Surface Piercing Propellers (SPPs) in high-speed crafts, many experiments and numerical studies have been conducted in this field. Due to the lack of a comprehensive series similar to conventional propellers in the field of SPPs, in this thesis, it has been tried to personalize the suitable basis by conducting two separate experimental tests in the National Iranian Maritime Laboratory (NIMALA) towing tank and the cavitation tunnel at Sharif University using computational fluid dynamics method and the commercial code STAR-CCM+. For this purpose, a wide range of phenomena and effective parameters on hydrodynamic...
Hydrodynamic Performance of Squat Submarine Equipped with Passive Pressure Drag Reductions
, Ph.D. Dissertation Sharif University of Technology ; Abbaspour, Madjid (Supervisor) ; Mohtasham Dolatshahi, Kiarash (Supervisor) ; Sani, Mahdi (Co-Supervisor)
Abstract
This research empirically examines the hydrodynamic performances of squat submarines under the resistance and wave tests, besides the numerical investigation of pressure drag reduction techniques. Submarines are limited for public use due to military classification issues and being expensive. This research introduces a new squat submarine in order to enable underwater exploration. This squat submarine has a 9- person capacity as a manned midget submersible using specific geometries of length-over-depth ratios (L/D) below four. The cause of such selection is to provide better visibility for the passengers to research and explore the sea. However, the geometrical features considerably change...
Investigation of Hydrodynamic Interaction between a Squat Submarine Operated behind a Ship
, Ph.D. Dissertation Sharif University of Technology ; Abbaspour, Madjid (Supervisor) ; Mohtasham Dolatsahhi, Kiarash (Supervisor) ; Sani, Mahdi (Co-Supervisor)
Abstract
This research investigates the hydrodynamic interaction of a squat submarine operating behind a ship in various wave and resistance experiments for towing and self-propelling arrangements. A one-tenth scaled captive model of a 0.625 m squat submarine is constructed along with a 1.5 m Fridsma ship to perform 116 unique experiments in a 4×6×400 m3 tank located in a towing tank center. The submarine is a new midget-submersible, of Apam-Napat SMSD type, with an L/D ratio below four. The cable is specified, regarding its weight per unit length, using a scaling method introduced in this research. Wave and resistance tests are performed for various 2D relative lengths and depths at short-distance...
Experimental evaluation of ship squat in shallow waters
, Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Vol. 36, Issue. 3 , 2014 , pp. 559-569 ; ISSN: 1806-3691 ; Seif, M. S ; Sharif University of Technology
Abstract
Enlargement of ship size in recent decades and no change in the harbors and approach channels have resulted in global attention toward navigation in shallow and confined waters. A phenomenon which restricts ship navigation in shallow waters is reduction of under-keel clearance in terms of sinkage and dynamic trim, which is called squatting. Due to the complexity of flow around the ship hull, one of the best methods for predicting the ship squat is the experimental approach based on systematic model tests in the towing tank. In this study, model tests for tanker ship model and traditional Persian Gulf and Oman Sea vessel called dhow had been performed in the towing tank and the squat of the...
Experimental and numerical investigation of squat submarines hydrodynamic performances
, Article Ocean Engineering ; Volume 266 , 2022 ; 00298018 (ISSN) ; Abbaspour, M ; Dolatshahi, K. M ; Sarraf, S ; Sani, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
This paper empirically examines the hydrodynamic performances of squat submarines under the resistance and wave tests beside numerical investigation of pressure drag reduction techniques. Despite vast information about the operation of the streamlined fluid vessels, there is not much information about the geometries and hydrodynamic behaviors of squat vessels with L/D ratios below four. This study experimentally investigates the impacts of various relative depths and flow inclinations, intending to find drag, heave, and sway forces at the velocities of 0.5, 1.0, 1.5, 2.0, and 2.5-m/s. A one-tenth scaled model of a squat submarine is examined under the resistance and wave train scenarios as...
, M.Sc. Thesis Sharif University of Technology ; Abbaspour, Madjid (Supervisor)
Abstract
In order to design a ship with waterjet system, estimation of its hydrodynamic performance is crucial. Presence and operation of waterjet propulsion system changes the flow field and pressure distribution in bottom and stem of ship hull, so affect hydrodynamic performance of craft. In the present thesis, CFD analysis is applied to free surface flow around a waterjet propelled ship using ANSYS CFX software. Also a waterjet propulsion system is built and settled in a ship model and resistance and self propulsion tests are performed. In order to performing a systematic process in project, in the first step, pump design is performed with extracting optimum efficiency relations and cavitation...
Experimental and numerical investigation of drag force over tubular frustum
, Article Scientia Iranica ; Volume 18, Issue 5 , 2011 , Pages 1133-1137 ; 10263098 (ISSN) ; Rad, M ; Sharif University of Technology
Abstract
There are different ways in order to achieve higher velocity in underwater vehicles. One of these methods is using a body with special form. This paper presents a towing tank based experimental study on drag forces for different Reynolds Numbers of a special underwater model. This paper investigates drag force and drag coefficient in a different flow direction over the model. Obtained experimental results in towing tank are explained. Computational Fluid Dynamic (CFD) simulation also is performed using commercial CFD software package FLUENT 6.3.26. There is a significant decrease in drag coefficient of model moving with small diameter at upstream
An investigation into the effect of pressure source parameters and water depth on the wake wash wave generated by moving pressure source
, Article Scientia Iranica ; Volume 25, Issue 4 , 2018 , Pages 2162-2174 ; 10263098 (ISSN) ; Binns, J ; Thomas, G ; Renilson, M ; Sharif University of Technology
Sharif University of Technology
2018
Abstract
In this study, the effect of moving pressure source and channel parameters on the generated waves in a channel was numerically investigated; draught, angle of attack, and profile shape as parameters of pressure source, and water depth and blockage factor as channel parameters for wave height. Firstly, the chosen Computational Fluid Dynamics (CFD) approach was validated with the experimental data over a range of speeds. Then, the CFD study was conducted for further investigations. It was shown that that by enlarging draught, angle of attack, and beam of the pressure source, the wave height generated would be increased. Channel study showed that it was possible to increase the wave height...
Experimental method for calculation drags reduction in air cavity boat
, Article 9th International Conference on Fast Sea Transportation, FAST 2007, Shanghai, 23 September 2007 through 27 September 2007 ; 2007 , Pages 278-285 ; 9781622764129 (ISBN) ; Rad, M ; Amini, H ; Sharif University of Technology
2007
Abstract
The search for higher ship speeds and better propulsive performance has resulted in many performance enhancement techniques. One technique is to introduce an air film along the bottom of the hull to reduce skin friction drag. The air film system opens many possibilities for using designs with larger payloads such as barges and tankers, as well as catamarans with larger deck space which otherwise are not attractive because of their higher propulsion power. Although reducing hull drag by air injection was proposed in the beginning of this century, it still remains to be fully exploited. In this thesis, two models are used to do the experiments. The first one was a simple catamaran model and...