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Experimental investigation of vortex generator influences on propeller cavitation and hull pressure fluctuations

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Journal of Hydrodynamics 2020年第1期32卷 82-92页

作者： Hong-bo Huang Yun Long Bin Ji National Key Laboratory on Ship Vibration and Noise China Ship Scientific Research CenterWiuxi 214082China State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan 430072China

In this paper,the transient turbulent cavitating flow around a marine propeller behind a ship was investigated experimentally with emphasis on how vortex generator(VG)influences propeller cavitation and hull pressure *** experiments were carried out in China Large Cavitation Channel with the closed test section covering 10.5 m in length and cross-section of 2.2 m^2×2.0m^*** experiment recorded instantaneous cavitation photos of the propeller and pressure fluctuations on the hull *** results demonstrate that without vortex generator,the sheet cavitation inception begins at-50°(310°),and then from-50°(310°)to 30°,the extent and area of sheet cavitation *** vortex generator installed on the hull,the sheet cavitation inception occurs in advance at-60°(300°),and the sheet cavitation expands to larger rotation range due to the vortex *** is shown that the vortex generator with proper geometry and installed location may contribute the highly nonuniform wake to be more uniform,and can make the change of propeller cavitation to be milder,which decrease the pressure fluctuations in this *** analysis indicates that the vortex generator may promote the energy distribution to be more uniform in physical and spectral space in some degree.

关键词： Cavitating flow pressure fluctuations propeller and ship hull vortex generator

Analysis and evaluation on pressure fluctuations in air dense medium fluidized bed

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International Journal of Mining Science and Technology 2018年第3期28卷 461-467页

作者： Sheng Cheng Duan Chenlong Zhao Yuemin Dong Liang Luo Zhenfu Key Laboratory of Coal Processing and Efficient Utilization of Ministry of Education School of Chemical Engineering & Technology China University of Mining & Technology Xuzhou 221116 China Forschungszentrum Jülich Julich 52428 Germany

pressure fluctuations contribute to the instability of separation process in air dense medium fluidized bed, which provides a high motivation for further study of underlying mechanisms. Reasons for generation and propagation of pressure fluctuations in the air dense medium fluidized bed have been *** rate and collision rate of particles were employed to deduce the correlation between voidage and pressure fluctuations. Simultaneously, a dynamic pressure fluctuation measuring and analysis system was established. Based on frequency domain analysis and wavelet analysis, collected signals were disassembled and analyzed. Results show gradually intensive motion of particles increases magnitudes of signal components with lower frequencies. As a result of violent particle motion, the magnitude of real pressure signal's frequency experienced an increase as air velocity increased moderately. Wavelet analysis keeps edge features of the real signal and eliminates the noise efficaciously. The frequency of denoised signal is closed to that of pressure signal identified in frequency domain analysis.

关键词： Air dense medium fluidized bed pressure fluctuations Frequency domain analysis Wavelet analysis Particle distribution function

pressure fluctuations IN GAS-SOLIDS FLUIDIZED BEDS

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China Particuology 2003年第4期1卷 139-144页

作者： Hsiaotao Bi Fluidization Research Centre Department of Chemical and Biological Engineering University of British Columbia 2216 Main Mall Vancouver BC V6T 1Z4 Canada

pressure fluctuation data measured in a series of fluidized beds with diameters of 0.05, 0.1, 0.29, 0.60 and 1.56 m showed that the maximum amplitude or standard deviation increased with increasing the superficial gas velocity and static bed height for relatively shallow beds and became insensitive to the increase in static bed height in relatively deep beds. The amplitude appeared to be less dependent on the measurement location in the dense bed. Predictions based on bubble passage, bubble eruption at the upper bed surface and bed oscillation all failed to explain all observed trends and underestimated the amplitude of pressure fluctuations, suggesting that the global pressure fluctuations in gas-solids bubbling fluidized beds are the superposition of local pressure variations, bed oscillations and pressure waves generated from the bubble formation in the distributor region, bubble coalescence during their rise and bubble eruption at the upper bed surface.

关键词： bubbling fluidized beds pressure fluctuations maximum pressure amplitude pressure waves scaleup effect

EXPERIMENTAL STUDY OF EFFECTS OF AIR CONTENT ON CAVITATION AND pressure fluctuations

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Journal of Hydrodynamics 2010年第5期22卷 634-638页

作者： YE Jin-ming XIONG Ying LI Fang CHEN Shuang-qiao College of Naval Architecture and Power Naval University of Engineering Wuhan 430033 China

This article studies the effects of air content on propeller cavitation and pressure fluctuations. The cavitation is observed while the pressure fluctuations on the hull are measured. When adjusting the air content, the sheet cavitation range does not change distinctly, but the pressure fluctuations see obvious differences. The amplitudes of the pressure fluctuations increase with the decrease of the air content. The results indicate that the air content has little effect on the sheet cavitation range but has an important effect on the bubble cavitation and the tip vortex cavitation. When the air content decreases, the water tensile force increases, which results in the instability of the bubble cavitation and the tip vortex cavitation and the increase of the pressure fluctuations. To minimize the scale effects, the experiments should be run at a high Reynolds number with a high nuclei content. The high Reynolds number is often realized by increasing the flow velocity and the propeller rotation speed, and the high nuclei content is often made by increasing the dissolved air content.

关键词： cavitation pressure fluctuations model test air content

Calculation grid and turbulence model for numerical simulating pressure fluctuations in high-speed train tunnel

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Journal of Central South University 2019年第10期26卷 2870-2877页

作者： JI Peng WANG Tian-tian WU Fan School of Traffic and Transportation Engineering Central South UniversityChangsha 410075China College of Mechanical and Vehicle Engineering Hunan UniversityChangsha 410082China

Calculation grid and turbulence model for numerical simulating pressure fluctuations in a high-speed train tunnel are studied through the comparison analysis of numerical simulation and moving model *** the waveforms and peak-peak values of pressure fluctuations between numerical simulation and moving model test,the structured grid and the SST k-ωturbulence model are selected for numerical simulating the process of high-speed train passing through the *** largest value of pressure wave amplitudes of numerical simulation and moving model test meet each *** the locations of the largest value of the initial compression and expansion wave amplitude of numerical simulation are in agreement with that of moving model *** calculated pressure at the measurement point fully conforms to the propagation law of compression and expansion waves in the tunnel.

关键词： high-speed train calculation grid turbulence model tunnel pressure fluctuations

An Investigation on Cavitation Induced pressure fluctuations of Propeller Blade Section

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An Investigation on Cavitation Induced Pressure Fluctuations...

Characterization of component interactions in two-stage axial turbine

2013年船舶水动力学学术会议

作者： Zeng Zhi-bo Liu Deng-cheng Xiong Zi-ying China Ship Scientific Research Center National Key Laboratory on Ship Vibration & Noise Jiangsu Key Laboratory of Green Ship Technology

Unavoidable cavitation will occur on propeller of high speed naval ships or commercial ships,which causes pressure fluctuations and noise,even erosion and thrust break *** order to reduce cavitation induced pressure fluctuations,propeller cavitation acceleration should be controlled due to the proportional relation between the pressure fluctuations and the corresponding cavitation volume *** cavitation flow(a volume acceleration) on propeller is too complex to conveniently evaluate in the process of propeller *** start the investigation from blade section based on an equivalent *** of cavitation volume on such blade sections is studied with RANS equations and a cavitation model,there a non-dimensional parameter is introduced to present the working cavitation conditions of such blade *** propeller blade sections at 0.8R are designed in behind condition for a 5600TEU container ship,one is designed by Eppler method,the other is a traditional NACA section,cavitation performance is comparatively *** volume accelerations of the two blade sections in behind condition are derived,moreover a FFT analysis is carried out,which potentially show a different characteristics of cavitation induced pressure *** work in the paper would become an important basis for new blade propeller section design for minimizing cavitating pressure fluctuations.

关键词： new blade section cavitation volume acceleration pressure fluctuations

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Chinese Journal of Aeronautics 2016年第4期29卷 893-913页

作者： Adel Ghenaiet Kaddour Touil Laboratory of Energetics and Conversion Systems Faculty of Mechanical Engineering University of Sciences and Technology Houari Boumediene Laboratory of Thermal Power Systems Applied Mechanics

This study concerns the characterization of both the steady and unsteady flows and the analysis of stator/rotor interactions of a two-stage axial turbine. The predicted aerodynamic performances show noticeable differences when simulating the turbine stages simultaneously or separately. By considering the multi-blade per row and the scaling technique, the Computational fluid dynamics(CFD) produced better results concerning the effect of pitchwise positions between vanes and blades. The recorded pressure fluctuations exhibit a high unsteadiness characterized by a space–time periodicity described by a double Fourier decomposition. The Fast Fourier Transform FFT analysis of the static pressure fluctuations recorded at different interfaces reveals the existence of principal harmonics and their multiples, and each lobed structure of pressure wave corresponds to the number of vane/blade count. The potential effect is seen to propagate both upstream and downstream of each blade row and becomes accentuated at low mass flow rates. Between vanes and blades, the potential effect is seen to dominate the quasi totality of blade span, while downstream the blades this effect seems to dominate from hub to mid span. Near the shroud the prevailing effect is rather linked to the blade tip flow structure.

关键词： CFD FFT analysis pressure fluctuations Two-stage axial turbine Unsteady flows Vane/blade interactions

Multiscale characterization of nanoparticles in a magnetically assisted fluidized bed

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Particuology 2020年第4期18卷 64-71页

作者： F.Karimi M.Haghshenasfard R.Sotudeh-Gharebagh R.Zarghami N.Mostoufi Department of Chemical Engineering Isfahan University of TechnologyP.O.Box ***IsfahanIran School of Chemical Engineering College of EngineeringUniversity of TehranP.O.Box 11155/4563TehranIran

pressure fluctuations of a fluidized bed of nanoparticles were measured during the fluidization of nanoparticles with and without a magnetic field at a frequency of 50 *** quantification analysis(RQA)and wavelet transform were used to determine the frequency range of various flow structures in the bed at three *** frequency ranges of the macro-,meso-,and micro-structures were determined to be 0-49Hz,49-781 Hz,and 781+Hz,*** of the determinisms of the sub-signals with and without the external field revealed that in the presence the field,breakage of larger agglomerates occurs faster than re-agglomeration of small agglomerates into larger *** power spectral density function of the pressure fluctuations indicated that with an external magnetic field,the power and the frequency range of the pressure signal of macro-structures do not change ***,the power of the meso-structure signal increases and its frequency range is widened toward higher frequencies,confirming that the number of small bubbles and agglomerates increase in the *** addition,the energy of signal analysis indicated that the external field significantly increases the share of meso-structures in the bed,confirming the RQA results.

关键词： Nanoparticles Fluidized bed Magnetic field pressure fluctuations Recurrence quantification analysis Wavelet transform

Multi-scale analysis of flow structures in fluidized beds with immersed tubes

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Particuology 2015年第4期13卷 99-106页

作者： Hamid R.Norouzi Maryam Tahmasebpoor Reza Zarghami Navid Mostoufi Multiphase Systems Research Lab.School of Chemical Engineering College of EngineeringUniversity of Tehran Department of Chemical and Petroleum Engineering University of Tabriz

Multi-scale analysis and non-linear analysis were combined to investigate the hydrodynamics of fluidized beds with and without horizontal tubes. pressure fluctuations were measured and analyzed employing discrete wavelet analysis, recurrence plot analysis, and recurrence quantification analysis. A systematic procedure was followed to determine wavelet parameters. At low gas velocities, the energy of macro-structures reduces with the addition of the first tube and then increases with the addition of a second tube. However, there is no notable difference at high gas velocities. Determinism is high for the bed without tubes, which can be attributed to the periodic behavior of bubbles. Determinism decreases with the addition of tubes because the breakage of bubbles results in less periodic behavior. The three methods of analysis used in this study captured the effects of immersed tubes on the hydrodynamics of fluidized beds. Recurrence quantitative analysis was found to be a powerful and easy-to-use method that can capture the nonlinear characteristics of fluidized beds much more quickly than conventional methods of nonlinear analysis. This method can thus be effectively used for the online monitoring of hydrodynamic changes in fluidized beds.

关键词： Immersed tube Non-linear analysis pressure fluctuations Recurrence plot Wavelet transform