Article
Engineering, Marine
Leonie S. Foehring, Peter Moller Juhl, Dietrich Wittekind
Summary: This paper analyzes the cavitation volume behavior of propellers using underwater noise measurement data, and investigates the cause of an often observed but unexplained similarity in shipping noise spectra.
JOURNAL OF MARINE SCIENCE AND ENGINEERING
(2022)
Article
Engineering, Marine
Seungnam Kim, Spyros A. Kinnas
Summary: A numerical method coupled with a boundary element method is used to evaluate propeller-induced hull pressures. Predictions show good agreement with experimental data and RANS simulations, especially under moderately loaded conditions.
Article
Engineering, Marine
C. Testa, L. Greco, J. Bosschers
Summary: In this study, the shaft loads of noncavitating marine propellers in oblique-flow conditions were investigated. The Boundary Element Method (BEM) hydrodynamics approach was verified using two propeller models and compared with experimental and numerical data. The results showed that the proposed BEM formulation has a good capability in capturing unsteady blade pressures and satisfactory results were obtained in terms of shaft loads fluctuations compared to Computational Fluid Dynamics (CFD) outcomes.
Article
Engineering, Marine
Ismail Kahraman, Gurbuz Bilici, Ramazan Tufan Azrak, Enes Tunca, Akif Kutlu, Bahadir Ugurlu
Summary: In this study, the problem of structure-borne noise radiated from a combined submarine-propeller system under self-propulsion condition is investigated using numerical methods. The results show that approximate configurations provide accurate estimations for limited frequency bands and should be employed with caution. Additionally, the flexibility of the propeller plays a major role in noise generation, increasing both noise levels and peak response amplitudes in the low- and high-frequency regions.
Article
Mechanics
Anubhav Bhatt, Harish Ganesh, Steven L. Ceccio
Summary: Partial cavity flows on a NACA0015 hydrofoil were visualized and studied using high-speed cinematography and time-resolved X-ray densitometry. Both near-surface liquid re-entrant flow and bubbly shock waves were identified as mechanisms causing cavity pinch-off and cloud shedding. The frequency of cavity shedding was examined and found to be related to the underlying flow dynamics. The probability of re-entrant flow or bubbly shock-induced shedding processes was quantified, and it was shown that the dominant mechanism for large-scale cavity shedding and cloud cavitation is shock waves when the Mach number exceeds unity.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Engineering, Marine
Ville Viitanen, Tuomas Sipila, Antonio Sanchez-Caja, Timo Siikonen
Summary: This paper numerically investigates the Potsdam Propeller Test Case in oblique inflow conditions, considering open water performance curves, cavitation observations, and pressure pulses. The study finds that propeller blade loading, cavitation, and pressure peaks are dependent on the blade rate frequency in non-uniform inflow, with good agreement between numerical simulations and experimental results.
Article
Mechanics
Han Liu, Zuoli Xiao, Lian Shen
Summary: Ventilated cavitating flows are investigated using direct numerical simulations, providing a comprehensive description of the two-phase flow and the air leakage and vortex shedding processes. The mean velocity suggests the existence of three characteristic flow structures: shear layer, recirculating area, and jet layer. Turbulent kinetic energy is concentrated in the jet layer, with streamwise turbulent fluctuations dominating in both shear layer and jet layer. Air leakage and vortex shedding occur periodically and show a one-to-one correspondence, confirmed by velocity and volume fluid spectra results and the autocorrelation function. Coherent flow structures are analyzed using the spectral proper orthogonal decomposition method, identifying fine coherent structures associated with various instability and convection mechanisms. This study complements previous research by providing detailed descriptions of turbulent motions and complex interactions in cavitating flows.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Engineering, Multidisciplinary
Euripides J. Sellountos, Theodore V. Gortsas, Demosthenes Polyzos
Summary: The Local Domain Boundary Element Method (LD-BEM) is introduced to solve incompressible fluid flow problems. By dividing the domain of interest into small subdomains, the integral representation of the solution is considered separately in each subdomain. By eliminating fluxes at all subdomain interfaces, LD-BEM leads to sparse linear system coefficient matrices and reduced computational complexity, overcoming some disadvantages of the conventional BEM. The proposed method is applied to the well-known 2D lid-driven cavity problem with high Reynolds numbers, involving over 10 million unknowns in the discretization.
ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS
(2023)
Article
Computer Science, Interdisciplinary Applications
Antigoni Kleanthous, Timo Betcke, David P. Hewett, Paul Escapil-Inchauspe, Carlos Jerez-Hanckes, Anthony J. Baran
Summary: We investigate various techniques to accelerate Calderon preconditioning in the context of boundary integral equation methods for electromagnetic transmission problems. By employing barycentric meshes only for the preconditioner and discarding non-essential boundary integral operators, and by using a lower-quality H-matrix assembly routine with the novel approach of discarding far-field interactions, we achieve significant reductions in computational cost. Experimental results on scattering by multiple dielectric particles demonstrate that our accelerated implementation can significantly reduce memory cost and computation time compared to a non-accelerated implementation.
JOURNAL OF COMPUTATIONAL PHYSICS
(2022)
Article
Physics, Applied
Benrong Zhang, Fajie Wang, Lin Qiu
Summary: In this paper, the authors propose a deep learning method called multi-domain physics-informed neural networks (MDPINNs) to numerically solve linear and nonlinear transient heat conduction problems in multilayer composite materials. The multilayer media are divided into independent sub-domains using domain decomposition technique, and single-layer deep neural networks are established for each sub-domain. The sub-networks are then connected by continuity conditions on the interface to form a MDPINNs' framework that can directly solve the transient heat conduction problem. Numerical experiments demonstrate the satisfactory accuracy of the proposed framework, even in micrometer or nanometer structures, and its advantage of directly solving both linear and nonlinear heat conduction problems in multilayer materials in a unified and concise form.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Mechanics
Xuhong Jin, Fei Huang, Wenbo Miao, Xiaoli Cheng, Bing Wang
Summary: Varying the boundary-layer thickness at the cavity entrance can significantly affect the flow characteristics and aerodynamic surface quantities of rarefied hypersonic flows. Thicker boundary layers allow external fluid to penetrate deeper into the cavity, leading to a transition from open to closed flow. The 3D effect becomes important only in cases of extremely thick boundary layers at the cavity entrance.
Article
Engineering, Marine
Afaq Ahmed Abbasi, Giovanni Franzosi, Edward Canepa, Stefano Gaggero, Diego Villa, Michele Viviani, Giorgio Tani
Summary: The present study aims to investigate the flow field generated by a marine propeller running with inclined shaft using velocimetric measurements. Laser Doppler Velocimetry (LDV) was used to measure a scaled model of the propeller in a cavitation tunnel, and ensemble average technique was applied to the acquired data. Tests were conducted both with and without the propeller at different velocities to analyze the incoming flow field and its effects on the propeller flow. The 3-D flow field was measured in four transverse sections and a longitudinal plane, with a dedicated interpolation technique to improve spatial resolution.
Article
Engineering, Marine
Jui-Hsiang Kao
Summary: This paper presents an Inverse Tracing Method (ITM) in the time domain to address the issue of radiating noise caused by unsteady propeller sheet cavitation. The ITM shows good agreement with far-field noise predictions and experimental results for near-field noise, although there are slight discrepancies. Additionally, predicting noise levels accurately requires adjustments to numerical cavity volumes and cavitation numbers.
Article
Physics, Multidisciplinary
Elsayed M. A. Elbashbeshy, Hamada Galal Asker
Summary: This paper investigates the boundary layer flow of a nanofluid containing gyrotactic microorganisms over a vertical stretching surface embedded in a porous medium. The effects of various controlling parameters on velocity, temperature, nanoparticle concentration, and microorganisms conservation are analyzed numerically. The results show that increasing the porosity parameter enhances the surface cooling effect.
EUROPEAN PHYSICAL JOURNAL PLUS
(2022)
Article
Mechanics
Wei Lin, Tiezhi Sun, Hao Xu, Jinxiong Duan
Summary: This study numerically simulated the underwater launching process of a vehicle under both stationary and rolling boundaries. The results showed that the rolling of the launch platform significantly altered the development of the tail cavity, impacting the motion and attitude of the vehicle. The shape of the cavity, pressure distribution, and collapse-induced load exhibited distinct differences between stationary and rolling conditions.
Article
Engineering, Marine
Mohamad Amin Ghazi, Hassan Ghassemi, Hamid Reza Ghafari
Summary: Two new profiles at the leading-edge tubercles of the tidal turbine have been proposed to improve hydrodynamic performance and increase power production. Computational simulations based on the Reynolds-Averaged Navier-Stokes equations have shown good agreement with experimental data. The newly proposed tubercles significantly increase power and torque coefficients, especially at higher tip speed ratios (TSRs).
SHIPS AND OFFSHORE STRUCTURES
(2023)
Article
Mechanics
Weijie Mo, Guanghua He, Hassan Ghassemi, Hao Yang, Weihao Mao
Summary: Numerical simulations were conducted to investigate wake vortex structures with different aspect ratios of a flapping hydrofoil on power extraction. The two-dimensional wake was dominated by a Karman-like vortex street composed of spanwise vortices, while the three-dimensional wake was dominated by two sets of oblique vortex structures. These vortex structures interacted with each other as they convect downstream. The power-extraction efficiency reached an optimum of 32.4% at an aspect ratio of 8 in the three-dimensional condition.
Article
Engineering, Marine
Hassan Zakerdoost, Hassan Ghassemi
Summary: This research developed a framework for analyzing and optimizing ship hull-propeller systems (HPSs) in waves. The framework is an efficient synthesis tool for determining the geometric characteristics of HPSs during the early stage of ship design. The optimization process was conducted using a multiobjective evolutionary algorithm, low-fidelity hydrodynamic solvers, and a medium-fidelity solver. Numerical results showed that the framework can find optimized designs with better hydrodynamic performance.
JOURNAL OF SHIP PRODUCTION AND DESIGN
(2023)
Article
Mechanics
Iman Farahbakhsh, Amin Paknejad, Hassan Ghassemi
Summary: A monolithic mathematical framework is proposed for understanding the fluid-rigid-elastic structure interaction problem. The Navier-Stokes equations are solved in a secondary formulation, and a technique for imposing the rigid boundaries is applied. The method is capable of modeling the interactions between rigid and elastic structures in an incompressible fluid flow.
FLUID DYNAMICS RESEARCH
(2023)
Article
Thermodynamics
Hossein Yazdi, Hamid Reza Ghafari, Hassan Ghassemi, Guanghua He, Madjid Karimirad
Summary: Integrating a floating offshore wind turbine (FOWT) and an array of wave energy converters (WECs) is proposed as a new hybrid concept for enhanced energy harvesting and reduced energy cost. The study compares the response of FOWT and a single SD WEC, and investigates the performance of three hybrid FOWT-MSD systems with 12SD, 15SD, and 18SD WECs under different wave conditions. The results show that 12SD absorbs more power than the other setups in the wave period of 6-9 s, while all three systems have similar power absorption in the wave period of 9-11 s. The absorbed power of 15SD and 18SD is higher than 12SD for wave periods above 12 s.
Article
Engineering, Marine
Hao Yang, Guanghua He, Weihao Mao, Weijie Mo, Hassan Ghassemi
Summary: This study investigates the influence of blockage effect and ground effect on the energy-extraction performance of oscillating hydrofoils using a two-dimensional numerical model. The results show that the double-wall configuration greatly improves efficiency, and the drag coefficient correction can remedy the influence of ground effect.
Article
Mechanics
Penglin Jing, Guanghua He, Hassan Ghassemi, Zhengxiao Luan
Summary: This study investigates the transient responses in fixed and free-heaving moonpools under the conditions of linear and nonlinear gap resonance. Through numerical simulations and parameter analyses, it is found that the free-heaving motion affects the developing patterns of gap resonance, but has little impact on the diminishment. By introducing a new amplification function, the development of gap resonance in the free-heaving moonpool is accurately predicted. The duration of damping time is greatly influenced by the phase relation between the free-surface elevation and the heave motion. Overall, this study contributes to our understanding of gap resonance in moonpools.
Article
Engineering, Marine
Mahdi Bandizadeh Sharif, Amir Hossein Gorbanpour, Hassan Ghassemi, Guanghua He
Summary: This paper focuses on numerically modeling wave and current patterns in Genaveh port, a coastal city in the Persian Gulf, with a sloping breakwater. Three different breakwater arm patterns were defined based on the marine currents in the area. Using meteorological and wave statistics, as well as data from monitoring and simulation projects, the hydrodynamics of the study area were simulated after the breakwater construction. The results show that an optimal pattern can achieve significant wave heights of 0.2m and wave speeds of 0.25m/s within the existing and newly constructed harbor basins.
SHIPS AND OFFSHORE STRUCTURES
(2023)
Article
Engineering, Marine
Mahdi Bandizadeh Sharif, Amir Hossein Gorbanpour, Hassan Ghassemi, Guanghua He
Summary: The Genaveh commercial port in Bushehr province, Iran, has been placed on the agenda of the Iranian PMO to consider its economic, commercial, and residential development. The research investigates the tranquillity of the harbor basin for safe berthing of vessels. Three modules from the MIKE 21 software package were utilized to analyze the prevailing wave directions and suggest modifications to increase the harbor basin's tranquillity.
POLISH MARITIME RESEARCH
(2023)
Article
Thermodynamics
A. Abbasi, H. Ghassemi, H. Ghafari, G. He
Summary: This paper compares the impact of different wavy leading-edge protuberances on the performance and power efficiency of oscillating hydrofoils. Unsteady turbulent 3D flow simulations are conducted using StarCCM+ software. Four new types of hydrofoils with wavy leading-edge protuberance are proposed. The results show that Type-M hydrofoil achieves consistently higher efficiency of over 46% by employing appropriate heave and pitch amplitudes.
JOURNAL OF APPLIED FLUID MECHANICS
(2023)
Article
Engineering, Marine
Atefeh Neisi, Hassan Ghassemi, Mehdi Iranmanesh
Summary: Investigating mooring line failure is crucial for ensuring safety in floating wind turbine platform operations. This study evaluates the performance of two mooring systems (OC4-DeepCwind and MSM-BMW) in intact and failure scenarios, and finds that the MSM-BMW system performs better.
