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Ge Muye - One of the best experts on this subject based on the ideXlab platform.

  • Numerical prediction of propeller induced hull Pressure Pulses and noise
    2021
    Co-Authors: Ge Muye
    Abstract:

    An operating marine propeller is one of the major sources inducing hull Pressure Pulses, onboard noise and vibration as well as underwater radiated noise. There are rising concerns of environmental impacts and comfort and welfare of passengers and crews due to these negative effects. Cavitation is a significant source of these effects, but it is typically inevitable if only the hydrodynamic efficiency of the propeller is optimized. To reduce the noise and the Pressure Pulses caused by the cavitation, a trade-off of the hydrodynamic efficiency should be made to design and optimize a propeller that possess both high hydrodynamic performance and low noise and hull Pressure pulse generation. More accurate predictions are needed to identify the best trade-off between a high efficiency propeller design and a low Pressure pulse and noise one.The study focuses on the numerical prediction of hull Pressure Pulses and radiated underwater noise using viscous CFD including the opensource package OpenFOAM and commercial package Star-CCM+. Numerical predictions are performed regarding different experimental configurations for determining hull Pressure Pulses and ship noise, including propellers mounted on inclined shafts and propellers operating behind ship hulls, under different scales and scaling laws with different operating conditions and Reynolds numbers.Non-cavitating propeller induced Pressure Pulses are generally lower in levels and rich in blade passing frequency comparing to cavitating conditions, with blade tip clearance as a major impact factor. For cavitating conditions the rate of cavity growth/shrinkage is found to play the dominating role generating Pressure fluctuations. For certain model scale configurations, numerical predictions with ordinary approaches predict massive sheet cavity on propeller blades leading to Pressure pulse prediction discrepancies comparing to experimental observations and measurements. These can be significantly improved by a developed bridged model considering laminar to turbulence transition. Tip vortex cavitation bursting is a common phenomenon found on propellers operating behind the ship hull and generating significant levels of Pressure Pulses. The phenomenon is numerically predicted with investigations of its generation mechanisms in relation to the propeller inflow, convex shaped sheet cavitation closure line and traveling re-entrant jet underneath the sheet cavity.Propeller induced noise prediction was studied using approaches focused on the FWH (Ffowcs Williams-Hawkings) acoustic analogy with incompressible input on permeable/porous data surface (PDS). \ua0Studies show this combination between incompressible input and FWH acoustic analogy can be erroneous, though using certain PDS placements and closer receivers the error can be reduced

  • Numerical investigation of tip vortex bursting and induced hull Pressure Pulses on a container vessel
    2021
    Co-Authors: Ge Muye, Svennberg Urban, Bensow Rickard
    Abstract:

    A rotating marine propeller generates Pressure Pulses on the hull above it. The dynamics of cavitation, especially the tip vortex cavitation (TVC) bursting and TVC destruction by sheet cavity collapse have been found to induce high levels of Pressure Pulses on the ship hull body. The present study is focused on the numerical prediction of propeller induced Pressure Pulses on the hull with analysis on the interactions between ship wake, sheet cavitation and TVC. The predicted 1st – 2nd order Blade Passing Frequency (BPF) agree well with experimental measurements and higher order BPF Pressure Pulses are reasonably predicted as well. The study shows that the re-entrant jet, which can be related to the propeller inflow and convex shaped sheet cavity closure line, plays an important role regarding sheet cavitation collapse as well as violent TVC dynamics, and induce significant levels of hull Pressure Pulses

  • Numerical investigation of propeller induced hull Pressure Pulses using RANS and IDDES
    2021
    Co-Authors: Ge Muye, Svennberg Urban, Bensow Rickard
    Abstract:

    This paper investigates the numerical predictions of Pressure Pulses induced by a cavitating marine propeller operating in behind-hull condition in model scale. Simulations are performed using the commercial package Star-CCM+ using RANS and IDDES approaches. The predicted sheet cavitation agreed well compared to experimental recordings and the 1st- and 2ndorder blade passing frequency (BPF) Pressure Pulses also agreed well compared to measurements via Pressure transducers mounted on the model scale ship hull. Tip vortex cavitation (TVC)bursting was observed in the experiments and predicted as well in the numerical simulations. A traveling re-entrant jet from blade leading edge to blade tip was predicted underneath the sheet cavity structure, and triggered the partly collapse of sheet cavitation and strong TVCdynamics. The hull Pressure uctuations are found to be correlated with the rate of cavitation volume growth/shrinkage and the TVC dynamics are found generating high levels of higherorder BPF Pressure Pulses, according to the deduced TVC volume time series. Significant cavitation variations were recorded between blade passings and propeller revolutions in the experiments, while in the numerical predictions no noticeable cavitation difference was predicted, and the predicted 3rd- to 5th-order BPF Pressure pulse tonal values are generally higher than experimental measurements. The cavitation variations in the experiments are suspected to be related with sheet cavitation inception rather than blade loading difference induced by wake dynamics

  • Investigation on RANS prediction of propeller induced Pressure Pulses and sheet-tip cavitation interactions in behind hull condition
    'Elsevier BV', 2020
    Co-Authors: Ge Muye, Svennberg Urban, Bensow Rickard
    Abstract:

    This paper investigates the numerical prediction of cavitation and hull Pressure Pulses induced by a marine propeller operating in behind-hull conditions of a container vessel in model scale. Simulations are performed using commercial package Star-CCM+ and opensource package OpenFOAM using RANS approach and predictions are compared with experimental measurements. A mesh dependency study with respect to wake prediction is also presented. Operating conditions scaled to two different Reynolds numbers with the same propulsion characteristics and cavitation number are considered to study scaling effect. Simulations using tip refined mesh are performed and compared with using base mesh to study the tip vortex generation, tip vortex cavitation, its interaction with sheet cavity and induced Pressure Pulses. The influence of time step length is also investigated. Star-CCM+ and OpenFOAM predict consistent results. The predicted cavitation patterns agree well compared to experimental measurements as well as Pressure pulse levels up to 3~4 times blade passing frequency (BPF) especially for the predictions with tip refined mesh. The sheet cavitation is the major contribution to 1st and 2nd order BPF Pressure Pulses and its closure has significant contributions to higher-order Pressure Pulses. Deduced Pressure Pulses by tip vortex cavitation (TVC) are significant ranging from 3rd order to 10th order of BPFs. The TVC induced Pressure Pulses are related to its violent bursting behavior which is influenced by the closure of the sheet cavity.\ua0\ua9 2020 Elsevier Lt

  • Numerical investigation of Pressure pulse predictions for propellers mounted on an inclined shaft
    2019
    Co-Authors: Ge Muye, Svennberg Urba, Ensow Rickard
    Abstract:

    In the presented study, two high-skew model scale marine propellers were tested in the cavitation tunnel and the induced Pressure Pulses were measured during the test. Propeller shaft was inclined about 10 degrees to create blade load variations. The cavitation pattern were recorded using high speed videos. The open-source package openFOAM and commercial package Star-ccm+ are used as simulation tools to predict Pressure Pulses numerically. By using the fully turbulent SST k − ω model, the predicted wetted flow Pressure pulse levels agreed well compared to experimental measurements, but together with Schnerr-Sauer\ua0cavitation mass transfer model, massive cavitation was predicted which lead to inaccurate Pressure pulse predictions.\ua0The transition sensitive turbulence model γ − Re θ model\ua0is used to study the cases, and simulation results reveal\ua0the existence of laminar-transition zone and vortex structures on the propeller blades. Attempts are made to linking correlation-based separation region from the transition model and the cavitation model, and good predictions of cavitation pattern are achieved but the predicted Pressure Pulses levels are merely improved

J D Richardson - One of the best experts on this subject based on the ideXlab platform.

  • response of the magnetic field in the geosynchronous orbit to solar wind dynamic Pressure Pulses
    Journal of Geophysical Research, 2007
    Co-Authors: Chinliang Wang, Junkai Liu, Zhaohui Huang, J D Richardson
    Abstract:

    We do a statistical survey of solar wind dynamic Pressure (P-d) Pulses and geosynchronous magnetic fields observed between 1998 and 2005. In geomagnetic quiet times with D-st > -50 nT, we find 111 solar wind dynamic Pressure Pulses which produce geosynchronous magnetic field responses. These responses are often observed by two or three GOES spacecraft at different local times in geosynchronous orbit. The magnitudes of the geosynchronous magnetic field changes (dB(z)) have a peak near the noon meridian, similar to the results obtained in the study of the response of the geosynchronous field to the large and sharp solar wind dynamic Pressure variations. However, the relative change of the geosynchronous magnetic field dBz/AV-B-z (where AV-B-z is the average of the geosynchronous magnetic field Bz observed during the response to the Pressure pulse) depends weakly on the local time; thus the change of B-z(dB(z)) is proportional to the average field (AV-B-z). As the magnitude of the relative change of solar wind dynamic Pressure (dP(d)/P-d) increases, the rate of geosynchronous magnetic field variation increases correspondingly. These results imply that the magnitude of the geosynchronous magnetic field response could be determined by AV- B-z. In addition, the interplanetary field orientation does not affect the response significantly. Using an MHD code which models the global behavior of the solar wind-magnetosphere-ionosphere system, we reproduce the main characteristics of the observations.

Tomoaki Hori - One of the best experts on this subject based on the ideXlab platform.

  • propagation and evolution of electric fields associated with solar wind Pressure Pulses based on spacecraft and ground based observations
    Journal of Geophysical Research, 2017
    Co-Authors: Y Nishimura, T Kikuchi, Naoko Takahashi, Yasumasa Kasaba, Atsuki Shinbori, Tomoaki Hori
    Abstract:

    We investigate spatial and temporal evolution of large-scale electric fields in the magnetosphere and ionosphere associated with sudden commencements (SCs) using multi-point equatorial magnetospheric (THEMIS, RBSP, GOES) and ionospheric (C/NOFS) satellites with radars (SuperDARN). A distinct SC event on March 17, 2013 shows that the magnetospheric electric field in the equatorial plane propagates from dayside toward nightside as a fast mode wave. The ionospheric electric field responds ~41 s after the onset of dayside magnetospheric electric field, which can be explained by the propagation of the Alfven wave along magnetic field lines. Poynting fluxes toward the ionosphere support these propagations. From a statistical analysis of response time, tailward propagation speed is estimated at about 1000–1100 km/s. We also statistically derive a spatial distribution and time evolution of the magnetospheric electric field in the dawn-dusk direction (Ey). Our result shows that negative Ey (dawnward) propagates from noon toward the magnetotail, followed by positive Ey (duskward). The propagation characteristics of electric fields in the equatorial plane depend on magnetic local time. At noon, negative Ey lasts for about 1 min, and positive Ey becomes dominant about 2 min after the SC onset. Negative Ey soon attenuates in the nightside region, while the positive Ey propagates fairly well to the pre-midnight or post-midnight regions while maintaining a certain amplitude. The enhancement of positive Ey is due to the enhancement of magnetospheric convection associated with the main impulse of SCs.

Pingbing Zuo - One of the best experts on this subject based on the ideXlab platform.

  • dynamic responses of the earth s radiation belts during periods of solar wind dynamic Pressure pulse based on normalized superposed epoch analysis
    Journal of Geophysical Research, 2016
    Co-Authors: Zheng Xiang, Yuri Shprits, Chen Zhou, Zhengyu Zhao, Xianguo Zhang, Pingbing Zuo
    Abstract:

    Using the electron flux measurements obtained from five satellites (GOES-15 and POES 15, 16, 18, and 19), we investigate the flux variations of radiation belt electrons during forty solar wind dynamic Pressure Pulses identified between September 2012 and December 2014. By utilizing the mean duration of the Pressure Pulses as the epoch timeline and stretching or compressing the time phases of individual events to normalize the duration by means of linear interpolation, we have performed normalized superposed epoch analysis to evaluate the dynamic responses of radiation belt energetic electrons corresponding to various groups of solar wind and magnetospheric conditions in association with solar wind dynamic Pressure Pulses. Our results indicate that by adopting the timeline normalization we can reproduce the typical response of the electron radiation belts to Pressure Pulses. Radiation belt electron fluxes exhibit large depletions right after the Pdyn peak during the periods of northward IMF Bz and are more likely to occur during the Pdyn pulse under southward IMF Bz conditions. For the pulse events with large negative values of (Dst)min, radiation belt electrons respond in a manner similar to those with southward IMF Bz, and the corresponding post-pulse recovery can extend to L ~ 3 and exceed the pre-pulse flux levels. Triggered by the solar wind Pressure enhancements, deeper earthward magnetopause erosion provides favorable conditions for the prompt electron flux dropouts that extend down to L ~ 5, and the Pressure Pulses with longer duration tend to produce quicker and stronger electron flux decay. In addition, the events with high electron fluxes before the Pdyn pulse tend to experience more severe electron flux dropouts during the course of the pulse, while the largest rate of electron flux increase before and after the pulse occurs under the pre-conditioned low electron fluxes. These new results help us understand how electron fluxes respond to solar wind dynamic Pressure Pulses and how these responses depend on the solar wind and geomagnetic conditions and on the preconditions in the electron radiation belts.

  • strong solar wind dynamic Pressure Pulses interplanetary sources and their impacts on geosynchronous magnetic fields
    The Astrophysical Journal, 2015
    Co-Authors: Pingbing Zuo, Xueshang Feng, Yanqiong Xie, Yi Wang
    Abstract:

    In this investigation, we first present a statistical result of the interplanetary sources of very strong solar wind dynamic Pressure Pulses (DPPs) detected by WIND during solar cycle 23. It is found that the vast majority of strong DPPs reside within solar wind disturbances. Although the variabilities of geosynchronous magnetic fields (GMFs) due to the impact of positive DPPs have been well established, there appears to be no systematic investigations on the response of GMFs to negative DPPs. Here, we study both the decompression effects of very strong negative DPPs and the compression from strong positive DPPs on GMFs at different magnetic local time sectors. In response to the decompression of strong negative DPPs, GMFs on the dayside near dawn and near dusk on the nightside, are generally depressed. But near the midnight region, the responses of GMF are very diverse, being either positive or negative. For part of the events when GOES is located at the midnight sector, the GMF is found to abnormally increase as the result of magnetospheric decompression caused by negative DPPs. It is known that under certain conditions magnetic depression of nightside GMFs can be caused by the impact of positive DPPs. Here, we find that a stronger Pressure enhancement may have a higher probability of producing the exceptional depression of GMF at the midnight region. Statistically, both the decompression effect of strong negative DPPs and the compression effect of strong positive DPPs depend on the magnetic local time, which are stronger at the noon sector.

Viviani Michele - One of the best experts on this subject based on the ideXlab platform.

  • Ship propeller side effects: Pressure Pulses and radiated noise
    De Gruyter, 2016
    Co-Authors: Gaggero Stefano, Villa Diego, Tani Giorgio, Gaggero Tomaso, Rizzuto Enrico, Viviani Michele
    Abstract:

    The present paper deals with the side effects of propellers cavitation, i.e. Pressure Pulses and radiated noise. These effects are gaining more and more importance for commercial ships for different reasons. Pressure Pulses significantly affect comfort onboard, thus their reduction is of utmost importance for all ships carrying passengers. As regards the underwater radiated noise, in the last decade interest has shifted from navy applications to commercial ships, due to the concern for the rising background noise in the oceans. The propellers, generating noise directly in water, represent one of the main contributions to the overall underwater noise emitted from ships. Due to the complexity of the mechanisms of propeller noise generation, different complementary strategies have to be followed to properly analyze the problem, ranging from induced Pressure Pulses to broadband noise and cavitation. In the present work, part of the activities carried out in the framework of the collaborative EU FP7 project AQUO (Achieve QUieter Oceans by shipping noise footprint reduction, www.aquo.eu) are reported. The paper presents the investigations carried out on a specific test case represented by a single screw research vessel, which is analyzed with three different strategies: numerical calculations, model scale investigations and fullscale measurements

  • Ship propeller side effects: Pressure Pulses and radiated noise
    'Walter de Gruyter GmbH', 2016
    Co-Authors: Gaggero Stefano, Villa Diego, Tani Giorgio, Gaggero Tomaso, Rizzuto Enrico, Viviani Michele
    Abstract:

    The present paper deals with the side effects of propellers cavitation, i.e. Pressure Pulses and radiated noise. These effects are gaining more and more importance for commercial ships for different reasons. Pressure Pulses significantly affect comfort onboard, thus their reduction is of utmost importance for all ships carrying passengers. As regards the underwater radiated noise, in the last decade interest has shifted from navy applications to commercial ships, due to the concern for the rising background noise in the oceans. The propellers, generating noise directly in water, represent one of the main contributions to the overall underwater noise emitted from ships. Due to the complexity of the mechanisms of propeller noise generation, different complementary strategies have to be followed to properly analyze the problem, ranging from induced Pressure Pulses to broadband noise and cavitation. In the present work, part of the activities carried out in the framework of the collaborative EU FP7 project AQUO (Achieve QUieter Oceans by shipping noise footprint reduction, www.aquo.eu) are reported. The paper presents the investigations carried out on a specific test case represented by a single screw research vessel, which is analyzed with three different strategies: numerical calculations, model scale investigations and full scale measurement

  • Experimental Analysis of the Influence of Ship Wake Scaling on Marine Propeller Radiated Noise and Pressure Pulses
    place:Beijing, 2014
    Co-Authors: Rizzuto Enrico, Tani Giorgio, Viviani Michele
    Abstract:

    The propeller performances and in particular the non-stationary cavitating behavior and its side effects, i.e. Pressure Pulses and radiated noise, are strongly dependent on the ship wake field. Many different predictive methods are available, however in many cases predictions are still performed on the basis of semi-empirical approaches, whose validity is doubtful. In par-allel to this, the ever increasing power of computational tools (namely RANS solvers) allows for a direct numerical prediction of the ship full scale wake. In the present paper, the effect of the adoption of two different full scale wakes obtained with semi-empirical methods and di-rect computations is evaluated experimentally by means of cavitation tunnel tests on a model propeller, focusing the attention not only on mechanical characteristics and cavitation extents but, specifically, on Pressure Pulses and radiated noise. The results of this study put into evi-dence the differences which may be expected using the two different scaling approaches

  • Ship wake scaling and effect on propeller performances
    CRC Press - Taylor & Francis Group, 2014
    Co-Authors: Gaggero Stefano, Villa Diego, Viviani Michele, Rizzuto Enrico
    Abstract:

    The propeller performances and in particular the non-stationary cavitating behaviour and its side effects, namely induced Pressure Pulses and radiated noise, are strongly dependent on the ship wake field. As a consequence, a correct prediction of the ship wake, considering the differences between model and full scale, is of utmost importance. In present study, results obtained by means of traditional and well established semi-empirical methods for wake scaling and direct RANS computations are compared, considering not only the differences in the wake field, but also their effect on the propeller non-stationary behavior, which is evaluated by means of a panel code. The results of the study allow to exploit the differences which may be expected by the designer using these different approache