Article
Engineering, Aerospace
Xiaofan Fei, Brandon L. Litherland, Brian J. German
Summary: This paper presents a three-dimensional unsteady vortex lattice method with a free vortex ring wake formulation for modeling the complex aerodynamics of a propeller at incidence. The method is validated by comparing its results with computational fluid dynamics (CFD) analyses. The paper also discusses the challenges of modeling propellers at incidence using vortex lattice methods.
Article
Green & Sustainable Science & Technology
Luca Greco, Claudio Testa
Summary: This study investigates the performance of a horizontal axis wind turbine in axial and yawed flow using a free-wake, unsteady, three-dimensional aerodynamic formulation. The comparison between numerical predictions and experimental data highlights the applicability and limitations of aerodynamic formulations based on the Boundary Element Method in wind turbine applications. Additionally, the performance of a model-scale rotor in different operating conditions is discussed, providing insights into extreme shear and rotor installation on a floating platform undergoing pitching motion.
Article
Engineering, Aerospace
Witold Artur Klimczyk
Summary: The methodology presented in this paper delivers an efficient blade design. Through optimization, the blade efficiency can be further improved, reducing power consumption at hover by around 7%. This approach can be applied to any blade design problem, with results varying depending on specific requirements and constraints.
AIRCRAFT ENGINEERING AND AEROSPACE TECHNOLOGY
(2022)
Article
Engineering, Marine
Seungnam Kim, Spyros A. Kinnas
Summary: In this article, a boundary element method (BEM) is used to predict the unsteady performance of ducted propellers. The method modifies the duct profiles based on predicted streamlines and uses a BEM/RANS coupling scheme to account for viscous interactions. Comparisons are made with experimental measurements and URANS simulations.
Article
Engineering, Mechanical
Fatih Selimefendigil, Seda Ozcan Coban, Hakan F. Oztop
Summary: This study proposes an efficient methodology for optimizing convective drying performance of multiple porous moist objects in a channel. Numerical simulations reveal the significant impact of different distances between objects on heat transfer efficiency, and the optimal distance values for reducing moisture content have been identified.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2021)
Article
Engineering, Marine
R. Doyle, T. L. Jeans, A. G. L. Holloway
Summary: This study analyzes the forces and moments on a UUV hull undergoing unsteady sway motions, using both traditional methods and hydrodynamic impulse based methods. It is found that the impulse based method provides a sensible decomposition of unsteady forces, primarily describing motion history effects, with decaying effects towards quasi-steady limit at large times or low frequencies.
Article
Engineering, Marine
Saeed Najafi, Behrooz Abtahi
Summary: In this study, a three-dimensional unsteady panel method was used to investigate the locomotion and propulsive efficiency of aquatic animals. The implementation of a wake sheet and flexible panel movements allowed for simulation of fish and wing motions. This study is important for understanding the locomotion and propulsion mechanisms of aquatic animals.
Article
Engineering, Aerospace
Diliana Friedewald
Summary: This research focuses on using systematic unsteady Reynolds-averaged Navier-Stokes simulations to study gust load analyses of transport aircraft in cruise flight conditions. The study found that amplitude effects decrease with lower Mach numbers or higher excitation frequencies. Nonlinear simulations predict lower maximum lift values and lower lift and moment derivatives compared to their linear counterparts for lower frequencies combined with large-amplitude excitations.
Article
Engineering, Mechanical
Feng Wang, Luca di Mare
Summary: This paper proposes a nonlinear harmonic method to simulate the unsteady interactions among multispool turbomachinery components. The method shows good performance in simulating the transfer of hot streaks and requires significantly less computational time compared to conventional methods.
JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME
(2023)
Article
Engineering, Aerospace
Mohsen Rostami, Amir Hamzeh Farajollahi
Summary: This paper describes the progress made on a new design of twin-propeller (front and rear) with duct, which improves the stability and performance of the UAV.
AEROSPACE SCIENCE AND TECHNOLOGY
(2021)
Article
Engineering, Mechanical
Yunqing Gu, Junjun Zhang, Songwei Yu, Chengqi Mou, Zhou Li, Chendong He, Denghao Wu, Jiegang Mou, Yun Ren
Summary: In this study, the grid irrelevance and discrete error in hydrofoil unsteady cavitation simulations were investigated using the GCI evaluation method to determine the optimal number of grids. Various turbulent viscosity correction approaches were employed to improve the turbulence model, and numerical simulations successfully captured the details of the hydrofoil cavity shape and shedding process, revealing the mechanism of hydrofoil cavitation.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2022)
Article
Energy & Fuels
Tlegen Kamidollayev, Juan Pablo Trelles, Jay Thakkar, Jan Kosny
Summary: Heat exchangers play a crucial role in thermal control in buildings, and the use of phase change materials (PCMs) enhances heat exchange processes. This study analyzes the performance of different configurations of PCM-air heat exchangers through simulation, aiming to determine the optimal thermal charging time.
Article
Engineering, Aerospace
Nanxuan Qiao, Tielin Ma, Jingcheng Fu, Ligang Zhang, Xiangsheng Wang, Pu Xue
Summary: The rising interest in the evolvability of electric vertical takeoff and landing (eVTOL) shows great potential for urban air mobility (UAM). The framework presented in this paper optimizes the blade shape of contra-rotating propellers (CRP) and studies the impact of revolution speed allocations on power efficiency. Results show that the optimized CRP outperforms the original design by 5.9% in thrust-to-power ratio, and the overall efficiency can be further improved by 5.3% when the dual propellers have similar torques. The framework allows for swift obtaining of optimized CRP schemes while maintaining robustness.
Article
Engineering, Marine
Weikang Du, Spyros A. Kinnas
Summary: The study introduces a numerical scheme, the three-dimensional flow separation model, to enable the panel method in the design and analysis of marine propellers with a blunt trailing edge. The shape of the flow separation zone is determined using criteria of zero local lifts and zero local moments. This model requires less computational effort while maintaining high accuracy, making it reliable for propeller design and analysis.
Article
Engineering, Aerospace
Witold Klimczyk, Adam Sieradzki
Summary: Modeling of UAV propellers in a global, multidisciplinary aeroacoustic optimization was studied, including geometry, aerodynamics, and aeroacoustics. Parametric geometry model was established using chord, twist, and sweep distributions, and airfoil parameters were added. Blade geometry-resolved aerodynamic model based on steady RANS was applied, and an aeroacoustic model for far-field tonal noise calculation was defined. Global sensitivity analysis and surrogate modeling-based optimization strategy were performed for efficient multi-objective aeroacoustic optimization of propeller geometries.
Article
Energy & Fuels
Stefano Gaggero, Mattia Martinelli
Summary: Pre-swirl fins-based energy saving devices have been designed to improve the propulsive performance of twin-screw ships. A combined BEM/RANSE method was used to predict the self-propulsion efficiency, and the ESD geometry was systematically varied to maximize the energy-saving effect. Surrogate models based on Ordinary Kriging were also employed for affordable preliminary design. The results showed promising energy-savings up to 3% at the design point and satisfactory savings in off-design conditions.
JOURNAL OF OCEAN ENGINEERING AND MARINE ENERGY
(2023)
Article
Automation & Control Systems
Miltiadis Kalikatzarakis, Andrea Coraddu, Mehmet Atlar, Stefano Gaggero, Giorgio Tani, Luca Oneto
Summary: For propeller-driven vessels, cavitation is the main noise source affecting wildlife, passenger comfort, and underwater warfare. Accurate predictions of underwater radiated noise in the design stage are crucial for designing efficient and silent propellers. Existing predictive models are based on physical, data-driven, and hybrid approaches. However, current hybridization strategies fail to fully utilize the strengths of both physical and data-driven models. In this study, a novel hybrid model is proposed, combining a state-of-the-art physical model with a data-driven model to improve accuracy and physical plausibility.
ENGINEERING APPLICATIONS OF ARTIFICIAL INTELLIGENCE
(2023)
Article
Computer Science, Interdisciplinary Applications
P. Cifani, M. Viviani, K. Modin
Summary: We propose an efficient and scalable numerical method for solving two-dimensional ideal fluid dynamics on the sphere. The method utilizes a tridiagonal splitting of the discrete spherical Laplacian and optimized numerical algorithms. For time-stepping, an isospectral integrator is adopted to preserve the geometric structure of Euler's equations. The algorithm achieves high computational performance by formulating the matrix Lie algebra basis through tridiagonal eigenvalue problems and implementing an efficient parallel computation.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Engineering, Marine
Stefano Gaggero, Marco Ferrando
Summary: Tip loading is a common strategy to increase the efficiency of propellers. This paper investigates the interaction mechanism between primary and secondary vortices in CLT and New Generation CLT propellers using high-fidelity CFD simulations. The results show that the configuration of the endplate affects the instability mechanism and splitting a single tip vortex can have negative side effects on the wake.
JOURNAL OF MARINE SCIENCE AND ENGINEERING
(2023)
Article
Engineering, Marine
Stefano Gaggero, Mattia Martinelli
Summary: The design of pumpjet propulsors (PJP) is addressed using a simulation-based design optimization approach, which includes a parametric description of the system's main geometrical characteristics, a RANSE solver with mixing plane interface capabilities, and a genetic algorithm. The optimal designs of both Rotor/Stator (PJP-R/S) and Stator/Rotor (PJPS/R) configurations are compared to a reference ducted propeller with decelerating nozzle (Gaggero et al., 2012), and detached eddy simulations (DES) are conducted to assess the performance improvements provided by the PJPs and the influence of the rotor/stator/nozzle interactions on the vortical structures shed by the propulsor.
Article
Engineering, Marine
Benedetto Piaggio, Guglielmo Sommariva, Andrea Franceschi, Diego Villa, Michele Viviani
Summary: The employment of twin pod-drives is becoming popular in modern ships due to its advantages in maneuverability, efficiency, space optimization and noise-comfort. However, the open stern shapes of the pod configuration may affect the coursekeeping and yaw checking abilities at high-speed. Therefore, a simulation tool is developed to analyze and validate the twin pod ship configurations, and it is found that a proper design of pod units does not negatively impact the yaw checking ability in certain cases.
Article
Physics, Multidisciplinary
M. Viviani, L. Girlanda, A. Kievsky, D. Logoteta
Summary: In this study, the authors investigate the processes d(d, p)3H and d(d, n)3He, which are relevant for energy production and big-bang nucleosynthesis. They use the ab initio hyperspherical harmonics method to accurately solve the four-body scattering problem. By varying the cutoff parameter, they estimate the theoretical uncertainty for various observables including the astrophysical S factor and quintet suppression factor.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
Aurora Tumino, Giuseppe G. Rapisarda, Marco La Cognata, Alessandro Oliva, Alejandro Kievsky, Carlos A. Bertulani, Giuseppe D'Agata, Mario Gattobigio, Giovanni L. Guardo, Livio Lamia, Dario Lattuada, Rosario G. Pizzone, Stefano Romano, Maria L. Sergi, Roberta Sparta, Michele Viviani
Summary: The Coulomb-free S-1(0) proton-proton (p-p) scattering length is determined using the quasi-free p + d -> p + p + n reaction. The resulting p-p scattering length is -18.17 (+0.52)(-0.58)vertical bar(stat) +/- 0.01(syst) fm and the effective range is 2.80 +/- 0.05(stat) +/- 0.001(syst) fm. A model based on universality concepts is developed to interpret this result and suggests assessing the charge symmetry breaking of the short-range interaction.
COMMUNICATIONS PHYSICS
(2023)
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
Diego Villa, Giorgio Tani, Stefano Gaggero, Marco Ferrando, Pierluigi Ausonio, Piero Travi, Michele Viviani
Summary: The literature on high-speed marine vehicles (HSMV) in the context of numerical self-propulsion predictions is relatively scarce. However, with the increasing market demand and the focus on greenhouse gas reduction, there is a need for researchers to have exact knowledge of the vessel working point and factors defining the propulsion condition. This paper presents a numerical study of two existing vessels using simplified viscous Computational Fluid Dynamic approaches to predict self-propulsion working points. The results are compared with sea trials and show a high level of agreement. The impact of uncertainties on the self-propulsion prediction is also investigated, revealing that the maximum speed can be obtained with a certain level of uncertainty. A more robust prediction is possible by including uncertainty assessment in the propulsion analyses. The validity of the proposed analyses is supported by the fact that the numerical uncertainty falls within the uncertainty obtained from full-scale measurements, providing a more reliable prediction of the vessel propulsion point.
Article
Engineering, Marine
Stefano Gaggero
Summary: In this paper, the influence of transition sensitive and modified mass transfer models on the prediction of cavitation inception of marine propulsors is investigated. RANS and DES methods are used to analyze the VP1304 test case, and the results show good agreement with the available measurements of propeller performances. The application of the transition sensitive correction to the mass transfer model improves the overall cavitation pattern, but the complex dynamics of bubble cavitation prevents accurate predictions of thrust/torque breakdown and induced pressure pulses levels.
JOURNAL OF MARINE SCIENCE AND APPLICATION
(2023)
Proceedings Paper
Astronomy & Astrophysics
Gianpiero Gervino, Carlo Gustavino, Evaristo Cisbani, Nicola Colonna, Giorgio Cotto, Marco D'Incecco, Salvatore Fiore, Cristian Massimi, Pierfrancesco Mastinu, Annamaria Mazzone, Elizabeth Musacchio-Gonzalez, Cristina Petrone, Michele Viviani
Summary: We present the latest progress of the n_TOF Collaboration Working Group in solving the puzzle of the existence of the new particle X17, first observed by the ATOMKI team in Hungary a few years ago but not confirmed or refuted by other independent experimental collaborations. We are designing a detection setup to achieve sufficient angular and energy resolution for measuring the decay paths and properties of X17, in collaboration with the Pisa Nuclear Theory team who has extensively studied the implications and characteristics of X17 based on the ATOMKI results.
NUCLEAR PHYSICS IN ASTROPHYSICS - X, NPA-X 2022
(2023)
Article
Engineering, Marine
Lakshmi Madhavan Miller, Stephen Krauss, Stefano Brizzolara, Christine Gilbert, Daniel Stilwell
Summary: Planar motion mechanism tests are widely used in simulations for ocean craft, especially for underwater vehicles. This article presents a detailed methodology to determine the appropriate amplitudes and frequencies for pure sway and pure yaw virtual planar motion mechanism (VPMM) for autonomous underwater vehicles in the early design stage.
Article
Engineering, Marine
Alba Ricondo, Laura Cagigal, Beatriz Perez-Diaz, Fernando J. Mendez
Summary: This research presents a site-specific metamodel based on the SWASH numerical model simulations, which can predict coastal hydrodynamic variables in a fast and efficient manner. The metamodel uses downscaled and dimensionality reduced synthetic database to accurately reproduce wave setup, wave heights associated with different frequency bands, and wave runup. This method has great potential in coastal risk assessments, early warning systems, and climate change projections.
Article
Engineering, Marine
Xiao Yu, Wangjun Ren, Bukui Zhou, Li Chen, Xiangyun Xu, Genmao Ren
Summary: This study investigated and compared the compression responses and energy absorption capacities of coral sand and silica sand at a strain rate of approximately 1000 s-1. The results showed that coral sand had significantly higher energy absorption capacity than silica sand due to its higher compressibility. The study findings suggest that using poorly graded coral sand can improve its energy absorption capacity.
Article
Engineering, Marine
Jingxi Zhang, Junmin Mou, Linying Chen, Pengfei Chen, Mengxia Li
Summary: This paper proposes a cooperative control scheme for ship formation tracking based on Model Predictive Control. A predictive observer is designed to estimate the current motion states of the leader ship using delayed motion information. Comparative simulations demonstrate the effectiveness and robustness of the proposed controller.
Article
Engineering, Marine
Yu Yao, Danni Zhong, Qijia Shi, Ji Wu, Jiangxia Li
Summary: This study proposes a 2DH numerical model based on Boussinesq equations to investigate the impact of dredging reef-flat sand on wave characteristics and wave-driven current. The model is verified through wave flume experiments and wave basin experiments, and the influences of incident wave conditions and pit morphological features on wave characteristics are examined.
Article
Engineering, Marine
Jayanta Shounda, Krishnendu Barman, Koustuv Debnath
Summary: This study investigates the double-average turbulence characteristics of combined wave-current flow over a rough bed with different spacing arrangements. The results show that a spacing ratio of p/r=4 offers the highest resistance to the flow, and the double-average Reynolds stress decreases throughout the flow depth. The advection of momentum-flux of normal stress shows an increase at the outer layer and a decrease near the bed region after wave imposition. Maximum turbulence kinetic energy production and diffusion occur at different layers. The turbulence structure is strongly anisotropic at the bottom region and near the outer layer, with a decrease in anisotropy observed with an increase in roughness spacing.
Article
Engineering, Marine
Meng Zhang, Lianghui Sun, Yaoguo Xie
Summary: The research proposes a method for online identification of wave bending and torsional moment in hull structures. For structures without large openings, the method optimizes sensor positions and establishes a mathematical model to improve accuracy. For structures with large openings, a joint dual-section monitoring method is proposed to simultaneously identify bending and torsional moments in multiple key cross sections.
Article
Engineering, Marine
Longming Chen, Shutao Li, Yeqing Chen, Dong Guo, Wanli Wei, Qiushi Yan
Summary: This study investigated the dynamic response characteristics and damage modes of pile wharves subjected to underwater explosions. The results showed that the main damaged components of the pile wharf were the piles, and inclined piles had a higher probability of moderate or more significant damage compared to vertical piles. The study also suggested that replacing inclined piles with alternative optimized structures benefits the blast resistance of pile wharves.
Article
Engineering, Marine
I. -C Kim, G. Ducrozet, V. Leroy, F. Bonnefoy, Y. Perignon, S. Bourguignon
Summary: Previous research focused on the accuracy and efficiency of short-term wave fields in specific prediction zones, while we developed algorithms for continuous wave prediction based on the practical prediction zone and discussed important time factors and strategies to reduce computational costs.
Article
Engineering, Marine
Hang Xie, Xianglin Dai, Fang Liu, Xinyu Liu
Summary: This study investigates the load characteristics of a three-dimensional stern model with pitch angle through a drop test, and reveals complex characteristics of pressure distribution near the stern shaft. The study also shows that the vibration characteristics of the load are influenced by the drop height and pitch angle, with the drop height having a greater effect on the high-frequency components.
Article
Engineering, Marine
Hangyuan Zhang, Wanli Yang, Dewen Liu, Xiaokun Geng, Wangyu Dai, Yuzhi Zhang
Summary: The deep-water bridge is more vulnerable to earthquake damage than the bridge standing in air. The larger blocking ratio has a significant impact on the added mass coefficient, which requires further comprehensive study. The generation mechanism of block effect is analyzed using numerical simulation software ANSYS Fluent. The results show that the recirculation zone with focus reduces the pressure on the back surface of the cylinder, resulting in the peak value of in-line force not occurring synchronously with the peak value of acceleration. The change in position and intensity of the recirculation zone with focus, as well as the change in water flow around the cylinder surface, are identified as the generation mechanism of the block effect, which has a 10% influence on the hydrodynamic force. The changing rule of the added mass coefficient with blocking ratio is discussed in detail, and a modification approach to the current added mass coefficient calculation method is suggested. Physical experiments are conducted to validate the modification approach, and the results show that it is accurate and can be used in further study and real practice.
Article
Engineering, Marine
Golnesa Karimi-Zindashti, Ozgur Kurc
Summary: This study examines the performance of an in-house code utilizing a deterministic vortex method on the rotation of circular and square cylinders. The results show that rotational motion reduces drag forces, suppresses fluctuating forces, and increases lift forces. The code accurately predicts vortex shedding suppression and identifies the emergence of near-field wakes in the flow over rotating square cylinders.
Article
Engineering, Marine
George Dafermos, George Zaraphonitis
Summary: The survivability of damaged ships is of great importance and the regulatory framework is constantly updated. The introduction of the probabilistic damage stability framework has rationalized the assessment procedure. Flooding simulation tools can be used to investigate the dynamic response of damaged ships.
Article
Engineering, Marine
Xuyue Chen, Xu Du, Chengkai Weng, Jin Yang, Deli Gao, Dongyu Su, Gan Wang
Summary: This paper proposes a real-time drilling parameters optimization method for offshore large-scale cluster extended reach drilling based on intelligent optimization algorithm and machine learning. By establishing a ROP model with long short-term memory neurons, and combining genetic algorithm, differential evolution algorithm, and particle swarm algorithm, the method achieves real-time optimization of drilling parameters and significantly improves the ROP.
Article
Engineering, Marine
Sung-Jae Kim, Chungkuk Jin, MooHyun Kim
Summary: This study investigates the dynamic behavior of a moored submerged floating tunnel (SFT) under tsunami-like waves through numerical simulations and sensitivity tests. The results show that design parameters significantly affect the dynamics of the SFT system and mooring tensions, with shorter-duration and higher-elevation tsunamis having a greater impact.
Article
Engineering, Marine
G. Clarindo, C. Guedes Soares
Summary: Environmental contours are constructed using the Inverse-First Order Reliability Method based on return periods. The paper proposes the use of the Burr distribution to model the marginal distribution of long-term significant wave heights. The newly implemented scheme results in different environmental contours compared to the reference approach.