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hydrodynamics
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Numerical study and acoustic analysis of propeller and hull surface vessel in self-propulsion mode
, Article Ships and Offshore Structures ; 2021 ; 17445302 (ISSN) ; Norouzi Keshtan, M ; Malek Jafarian, M ; Bagheri, M. R ; Sharif University of Technology
Taylor and Francis Ltd
2021
Abstract
In this article, the hydrodynamic analysis and noise of the propeller and the surface vessel hull were examined. The model selected in this study is a KRISO Container Ship (KCS) with a five-bladed propeller. Initially, the hydrodynamic analysis of the propeller in open water mode and then in self-propulsion mode was investigated using computational fluid dynamics. Simulations were carried out using a commercial solver, STAR-CCM+ (RANS equations with FVM and VOF model). Finally, the emitted noise from the propeller and the vessel hull was investigated using Fox William Hawkins equations. The pressure distribution and hydrodynamic performance (thrust, torque, efficiency) of the propeller in...
A new formulation for equivalent hydrodynamic modeling of the Jack-up legs
, Article Proceedings of the 21st International Conference on Offshore Mechanics and Arctic Engineering (OMAE), Oslo, 23 June 2002 through 28 June 2002 ; Volume 1 , 2002 , Pages 605-611 ; ASME ; Sharif University of Technology
2002
Abstract
Regulations of offshore structures suggest the application of Morison type equation for the estimation of forces induced by wave and current on the slender bodies of Jacket and Jack-up structures. However, common values of hydrodynamic coefficients are rarely defined in two different regulations. Estimation of global responses of Jack-up structure, the simplified geometrical model is used, therefore we will try to modify the DNV formulations in order to estimate the hydrodynamic forces on equivalent pile. Finally, the forces on the real structure and the equivalent pile model are compared and it has been shown that the approximation of the inertia forces has more accuracy comparing to the...
Numerical study and acoustic analysis of propeller and hull surface vessel in self-propulsion mode
, Article Ships and Offshore Structures ; Volume 17, Issue 11 , 2022 , Pages 2488-2497 ; 17445302 (ISSN) ; Norouzi Keshtan, M ; Jafarian, M. M ; Bagheri, M. R ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
In this article, the hydrodynamic analysis and noise of the propeller and the surface vessel hull were examined. The model selected in this study is a KRISO Container Ship (KCS) with a five-bladed propeller. Initially, the hydrodynamic analysis of the propeller in open water mode and then in self-propulsion mode was investigated using computational fluid dynamics. Simulations were carried out using a commercial solver, STAR-CCM+ (RANS equations with FVM and VOF model). Finally, the emitted noise from the propeller and the vessel hull was investigated using Fox William Hawkins equations. The pressure distribution and hydrodynamic performance (thrust, torque, efficiency) of the propeller in...
Hydrodynamic Modeling of an AUV
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
Autonomous underwater vehicles (AUVs) are a type of marine vehicles which are currently being used for exploration, maintenance, repairing of marine structures and military appliances. Unmanned underwater vehicles categorize in two types: ROVs and AUVs, ROVs (remotely operated vehicles) usually are connected to the mother vessel with a cable, conduction signals transfer through this cable and there is an operator in the control loop. The vehicle may be fed up with this cable, AUVs are modern underwater vehicles which the operator on controlling and conducting is removed, there is no connection between the vehicle and mother vessel, energy sources and controlling orders are set up in the...
Study The Effect of Geometric Parameter on Hydrodynamic and Hydroacoustic Performance Marine Propeller in Far Field by the Openwater Method
, M.Sc. Thesis Sharif University of Technology ; Seif, Mohammad Saeed (Supervisor) ; Mehdigholi, Hamid (Co-Supervisor)
Abstract
One of the most important noise produced by craft, is the propeller noise which must be identified and measured for many reasons, including military and engineering applications. Therefore, in the first step, the sources of noise emissions in the propeller are studied, and after describing the research background, the governing equations of this research are examined. Then, to validate, the DTMB 4119 propeller, which has hydrodynamic and hydroacoustic results, is used. In order to carry out the investigations, a B series propeller model is selected and compared with changing the parameters of the Rake, Skew, Pitch ratio and the number of blades for their hydrodynamic and hydroacoustic...
Dynamics of the nanoneedle probe in trolling mode AFM
, Article Nanotechnology ; Volume 26, Issue 20 , April , 2015 ; 09574484 (ISSN) ; Pishkenari, H. N ; Keramati, R ; Minary Jolandan, M ; Sharif University of Technology
Institute of Physics Publishing
2015
Abstract
Atomic force microscopy (AFM), as an indispensable tool for nanoscale characterization, presents major drawbacks for operation in a liquid environment arising from the large hydrodynamic drag on the vibrating cantilever. The newly introduced 'Trolling mode' (TR-mode) AFM resolves this complication by using a specialized nanoneedle cantilever that keeps the cantilever outside of the liquid. Herein, a mechanical model with a lumped mass was developed to capture the dynamics of such a cantilever with a nanoneedle tip. This new developed model was applied to investigate the effects of the needle-liquid interface on the performance of the AFM, including the imaging capability in liquid
Jet impact geometry and plunge pool dimensions effects on dynamic pressures at pool sidewalls
, Article Canadian Journal of Civil Engineering ; Volume 35, Issue 4 , 2008 , Pages 408-417 ; 03151468 (ISSN) ; Zarnani, P ; Sharif University of Technology
2008
Abstract
A plunge pool is one of the energy dissipater structures for high head dams, which ensures stability of the dam under extreme hydrodynamic pressure, due to falling jet impacts. The excess energy of the jet is dissipated, together with significant impact pressure exerted on the floor and pool walls. Thus, appropriate assessment of jet dynamic characteristics in the plunge pool is essential. This research presents experimental results focusing on. the distribution of mean and extreme pressure fluctuations on the sidewalls, due to circular and rectangular plunging jets, and the effects of pool dimension, especially in narrow valleys. The experimental variables are discharge, geometry of jet,...
Investigating the effect of geometric parameters on hydrodynamic and hydro-acoustic performances of submerged propellers
, Article Applied Ocean Research ; Volume 114 , 2021 ; 01411187 (ISSN) ; Ebrahimi, A ; Zahedi, F ; Javanmardi, M. R ; Seif, M. S ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The hydro-acoustic analysis of submerged propellers is an important issue in marine industries, which is examined to reduce the vibrations and noise level of vessels alongside reducing fuel consumption and improving hydrodynamic efficiency. B-series propellers are common propellers whose hydrodynamic and acoustic investigation through applying suitable rake, and skew angle can offer proper results to designers for enhancing the hydrodynamic performance and reducing noise. In this study, a model of the five-bladed B-series propeller with the normal skew angle is chosen. The effects of geometric parameters, including the rake angle, skew angle, geometric pitch ratio, and the number of blades...
A fully explicit incompressible Smoothed Particle Hydrodynamics method for multiphase flow problems
, Article Engineering Analysis with Boundary Elements ; Volume 143 , 2022 , Pages 501-524 ; 09557997 (ISSN) ; Hopp Hirschler, M ; Shadloo, M. S ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Multiphase flow is a challenging area of computational fluid dynamics (CFD) due to their potential large topological change and close coupling between the interface and fluid flow solvers. As such, Lagrangian meshless methods are very well suited for solving such problems. In this paper, we present a new fully explicit incompressible Smoothed Particle Hydrodynamics approach (EISPH) for solving multiphase flow problems. Assuming that the change in pressure between consecutive time-steps is small, due to small time steps in explicit solvers, an approximation of the pressure for following time-steps is derived. To verify the proposed method, several test cases including both single-phase and...
Extended and Unscented Kalman filters for parameter estimation of an autonomous underwater vehicle
, Article Ocean Engineering ; Vol. 91, issue , 2014 , p. 329-339 ; Sarhadi, P ; Zarini, M ; Sharif University of Technology
Abstract
In this paper, a high performance procedure for estimating of hydrodynamic coefficients in Autonomous Underwater Vehicles (AUV's) is proposed. In modeling of an AUV, experimental data should be verified and validated using appropriate techniques. Due to implementation complexity in calculating methods, computation of hydrodynamic parameters is challenging. This paper presents analytical approaches for estimating an AUV's hydrodynamic coefficients. Nonlinear Kalman Filter (KF) algorithms are implemented to estimate unknown augmented states (coefficients). A comparative study is conducted which shows the superior performance of Unscented Kalman Filter (UKF) in comparison with Extended Kalman...
Transportation and Settling Distribution of Microparticles in Low-Reynolds-Number Poiseuille Flow in Microchannel
, Article Journal of Dispersion Science and Technology ; Volume 37, Issue 4 , 2016 , Pages 582-594 ; 01932691 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Taylor and Francis Inc
Abstract
In this article, velocity field and settling distribution of microparticles in a dilute suspension in low-Reynolds-number Poiseuille flow in a microchannel is experimentally investigated using microscopic image analysis. An effective technique is applied to manipulate single-particle tracking in order to determine the controlling parameters on transportation and settling of microparticles in microchannels. The results show that the velocities of dispersed phase are affected by the hydrodynamic properties, and this velocity deviation can be significant when the hydrodynamic coupling between particles and channel walls is considerable. Increasing the Reynolds number would result in decrease in...
Hydrodynamics maneuver of a single helical flagellum swimming robot at low-Reynolds condition
, Article Microfluidics and Nanofluidics ; Volume 23, Issue 1 , 2019 ; 16134982 (ISSN) ; Bahmanyar, S ; Sharif University of Technology
Springer Verlag
2019
Abstract
Helical swimming robots with a capable propulsion system at low-Reynolds numbers have been proposed for many applications. Although linear propulsion characteristics of swimming robots with a single helical flagellum have been extensively studied, the characteristics of maneuverability have not been completely investigated yet. This study presents a new method for the maneuverability of the helical swimming robot with a single helical flagellum. This mechanism is based on the change in the angle between the helical and body axes. This study shows that a change in the aforementioned angle can enable the swimming robot to have turning maneuvers in clockwise or counterclockwise directions....
Hydrodynamics maneuver of a single helical flagellum swimming robot at low-reynolds condition
, Article Microfluidics and Nanofluidics ; Volume 23, Issue 1 , 2019 ; 16134982 (ISSN) ; Bahmanyar, S ; Sharif University of Technology
Springer Verlag
2019
Abstract
Helical swimming robots with a capable propulsion system at low-Reynolds numbers have been proposed for many applications. Although linear propulsion characteristics of swimming robots with a single helical flagellum have been extensively studied, the characteristics of maneuverability have not been completely investigated yet. This study presents a new method for the maneuverability of the helical swimming robot with a single helical flagellum. This mechanism is based on the change in the angle between the helical and body axes. This study shows that a change in the aforementioned angle can enable the swimming robot to have turning maneuvers in clockwise or counterclockwise directions....
Hydrodynamic performance of multiple co-axial heave plates with different diameters
, Article Ships and Offshore Structures ; Volume 15, Issue 4 , 2020 , Pages 380-392 ; Behzad, M ; Thiagarajan, K. P ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
Heave plates are structural components of a floating structure whose primary purpose is to increase damping and added mass in heave or pitch direction. If multiple plates are stacked along a common axis, then the relative diameters and spacing in between are important factors affecting the performance. In the present study, hydrodynamic coefficients of single, double and triple disks are experimentally investigated in different arrangements as Uniform, Concave and Convex edge shapes. It is observed that each disk in a multiple arrangement with lower diameter ratio have better hydrodynamic performance compared to the cases with higher diameter ratio when the spacing is small compared to the...
A fully explicit three-step SPH algorithm for simulation of non-Newtonian fluid flow
, Article International Journal of Numerical Methods for Heat and Fluid Flow ; Volume 17, Issue 7 , 2007 , Pages 715-735 ; 09615539 (ISSN) ; Taghizadeh Manzari, M ; Kazemzadeh Hannani, S ; Sharif University of Technology
2007
Abstract
Purpose - This paper sets out to present a fully explicit smoothed particle hydrodynamics (SPH) method to solve non-Newtonian fluid flow problems. Design/methodology/approach - The governing equations are momentum equations along with the continuity equation which are described in a Lagrangian framework. A new treatment similar to that used in Eulerian formulations is applied to viscous terms, which facilitates the implementation of various inelastic non-Newtonian models. This approach utilizes the exact forms of the shear strain rate tensor and its second principal invariant to calculate the shear stress tensor. Three constitutive laws including power-law, Bingham-plastic and...
Vortex shedding modes around oscillating non-uniform double heave plates
, Article Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment ; Volume 235, Issue 2 , 2021 , Pages 558-569 ; 14750902 (ISSN) ; Alvandi, M ; Behzad, M ; Thiagarajan, K. P ; Sharif University of Technology
SAGE Publications Ltd
2021
Abstract
Multiple co-axial heave plates of uniform geometry are attached to offshore platforms for inducing damping and added mass. These effects generally decrease the magnitude of the dynamic response of the platform under applied environmental excitation forces. When spacing between heave plates is decreased the damping and added mass performance are altered due to their strong vortex interaction. A new non-uniform plate configuration is proposed that may create different hydrodynamic characteristics. The modes of vortex shedding around plate edges in a non-uniform arrangement under forced harmonic oscillation are investigated via the CFD method. Furthermore, a new simplified formula for the total...
Hydrodynamic damping enhancement by implementing a novel combined rigid-elastic heave plate
, Article Journal of Marine Science and Technology (Japan) ; Volume 26, Issue 1 , 2021 , Pages 216-232 ; 09484280 (ISSN) ; Behzad, M ; Thiagarajan, K ; Sharif University of Technology
Springer Japan
2021
Abstract
Heave plates are structural components used for reducing the vibrations caused by environmental forces on marine and offshore structures by changing the hydrodynamic properties. The fact that the added mass increase via heave plates does not always lead to the structural response reduction underscores the role of damping in maintaining the vibration amplitude within allowable limits. In the present experimental study, a novel combined rigid-elastic design is used to improve the damping through the velocity increase in the elastic part and added mass creation in the central rigid part. The desired percentage of total added mass and damping can be adjusted by changing the rigid-to-elastic...
Controlled swarm motion of self-propelled microswimmers for energy saving
, Article Journal of Micro-Bio Robotics ; 2021 ; 21946418 (ISSN) ; Nejat Pishkenari, H ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
Swarm motion is an amazing collective behavior in nature for energy saving. Inspiring this natural phenomenon in microorganisms’ swimming, we have proposed a motion strategy for a swarm of microrobots to reduce their energy consumption during path tracking. The investigated microrobot is an artificial Self-Propelled Microswimmer (SPM) with high maneuverability at low Reynolds number flow (Re ≪ 1). In this study, we have demonstrated that forming a swarm behavior with minimum energy consumption requires the microswimmers to be close enough to each other, since at small distances the hydrodynamic interactions of microswimmers reduce their energy consumption. Moreover, we also showed that...
Vortex shedding modes around oscillating non-uniform double heave plates
, Article Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment ; Volume 235, Issue 2 , 2021 , Pages 558-569 ; 14750902 (ISSN) ; Alvandi, M ; Behzad, M ; Thiagarajan, K. P ; Sharif University of Technology
SAGE Publications Ltd
2021
Abstract
Multiple co-axial heave plates of uniform geometry are attached to offshore platforms for inducing damping and added mass. These effects generally decrease the magnitude of the dynamic response of the platform under applied environmental excitation forces. When spacing between heave plates is decreased the damping and added mass performance are altered due to their strong vortex interaction. A new non-uniform plate configuration is proposed that may create different hydrodynamic characteristics. The modes of vortex shedding around plate edges in a non-uniform arrangement under forced harmonic oscillation are investigated via the CFD method. Furthermore, a new simplified formula for the total...
Hydrodynamic damping enhancement by implementing a novel combined rigid-elastic heave plate
, Article Journal of Marine Science and Technology (Japan) ; Volume 26, Issue 1 , 2021 , Pages 216-232 ; 09484280 (ISSN) ; Behzad, M ; Thiagarajan, K ; Sharif University of Technology
Springer Japan
2021
Abstract
Heave plates are structural components used for reducing the vibrations caused by environmental forces on marine and offshore structures by changing the hydrodynamic properties. The fact that the added mass increase via heave plates does not always lead to the structural response reduction underscores the role of damping in maintaining the vibration amplitude within allowable limits. In the present experimental study, a novel combined rigid-elastic design is used to improve the damping through the velocity increase in the elastic part and added mass creation in the central rigid part. The desired percentage of total added mass and damping can be adjusted by changing the rigid-to-elastic...