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A hybrid method for aeroacoustic computation of moving rigid bodies in low Mach number flows

THEORETICAL AND COMPUTATIONAL fluid DYNAMICS 2024年第5期38卷 747-777页

作者： Wang, Kai Ye, Tiangui Wang, Xueren Jin, Guoyong Chen, Yukun Harbin Engn Univ Coll Power & Energy Engn Harbin 150001 Peoples R China Naval Acad Armament Beijing 100161 Peoples R China

To analyze the noise induced by moving rigid structures in low Mach number flows, acoustic governing equations based on the viscous/acoustic splitting method and the arbitrary Lagrangian-Eulerian method are rigorously derived. In order to resolve the numerical instability generated in a non-uniform mean flow, the modified viscous/acoustic method, based on the filtering method, is developed. The acoustic equations are transformed into the same form as the incompressible flow equations by introducing the acoustic co-velocity and solved based on a collocated grid finite volume method. An approach for solving acoustic equation based on the PIMPLE algorithm is presented and computed in open-source computational fluid dynamics software OpenFOAM, which brings down communication costs and speeds up computing efficiency. Furthermore, the source term decomposition is extended to study the noise generated by each source term in a motion grid. Several examples including stationary and moving meshes have been designed to prove the accuracy of this approach. Finally, the aerodynamic and acoustic properties for the flow past a transversely oscillating cylinder at Re = 200, Ma = 0.2 in lock-in and non-lock-in regions is present.

关键词： Viscous/acoustic splitting method Aeroacoustics fluid-structure interaction Finite volume method

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Thermal field and scroll deformation analysis study of a multi-stage dry scroll vacuum pump based on fluid-solid coupling numerical simulation

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VACUUM 2025年 233卷

作者： Zhang, Ying-li Yue, Xiang-ji Ba, De-chun Yang, Fan Northeastern Univ Sch Mech Engn & Automat Shenyang 110819 Peoples R China Midea Co Res Inst Ind Technol Business Grp Foshan 528000 Peoples R China

Based on the conjugate heat transfer theory, a two-way thermal-fluid-solid coupling numerical simulation of the multi-stage scroll vacuum pump is established. The simulation error is reduced to -4.44 %, which improves the simulation accuracy. The gas temperature in the pump gradually increases due to the compression process and heat transfer. For the independent scroll working chamber, the temperature is unbalanced under the combined influence of heat transfer, leakage, and the orbiting scroll work, and the gas temperature is highest at the end. The temperature distribution of the fixed scrolls increases centripetally and gradually increases along the direction of the scroll wrap. The temperature distribution in the orbiting scroll is relatively uniform. The thermal deformation of the scrolls gradually increases outward along the radial direction, and the axial direction deformation is small. The results can provide a theoretical foundation for the structure design and optimization of the dry scroll vacuum pump.

关键词： Dry scroll vacuum pump fluid-structure interaction Thermal field distribution Thermal deformation

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Oscillatory characteristics and propulsive performance of a tuna-like caudal fin driven by macro fiber composites

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MECHANICS OF ADVANCED MATERIALS AND structureS 2025年

作者： Jin, Aiguo Yang, Qinfeng Wen, Zhiwei Hu, Yanhai Ningbo Polytech Intelligent Equipment Res Inst Ningbo 315800 Zhejiang Peoples R China Ningbo Univ Fac Mech Engn & Mech Ningbo 315211 Zhejiang Peoples R China Zhejiang Univ State Key Lab CAD & CG Hangzhou Peoples R China Ningbo Sunny Optech Co Ltd Ningbo Zhejiang Peoples R China

Flexible structures actuated by piezoelectric composites have attracted much attention as underwater bionic thrusters. In this paper, a tuna-like caudal fin propulsion device actuated by macro fiber composite (MFC) is designed and fabricated, and its underwater vibration characteristics and propulsion performance are investigated. The underwater fluid-structure interaction dynamics equations of the variable cross-section bionic caudal fin with the internal driving force provided by MFC are established, and the damping effect of the surrounding fluid is taken into account. Based on the classical Euler-Bernoulli beam theory, the segmented mode shape functions of the variable section flexible caudal fin are derived by the assumed mode method. It is demonstrated that the first-order modal shapes calculated theoretically and measured experimentally are basically coincident when the number of elements is 30. The transverse deflection, vibration amplitude, and average propulsive force of the proposed structure tip at different driving levels are visualized by comprehensive parametric numerical analysis. The simulation results indicate that the maximum vibration velocity at the caudal fin tip does not occur at the first natural frequency, and the trend of average thrust force is generally consistent with that of the vibration velocity. Moreover, underwater experimental results show that the measured amplitude-frequency response curve of the flexible structure closely aligns with the simulation ones, especially for the values of the resonance frequency and the peak response. Specifically, for different driving levels, the experimental data of the underwater maximum vibration velocity and average thrust force for the proposed structure show good agreement with the theoretical predictions. These findings provide valuable insights for the study of underwater bio-inspired robotic fish driven by smart materials as well as its propulsion performance.

关键词： Tuna-like caudal fin macro fiber composite (MFC) propulsion performance fluid-structure interaction dynamics equations damping effect flexible structure

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EARTHQUAKE ENGINEERING & STRUCTURAL DYNAMICS 2025年第3期54卷 816-832页

作者： Chen, Yu Wu, Kun Zhao, Bo Li, Zhong-Xian Civil Aviat Univ China Sch Transportat Sci & Engn Tianjin Peoples R China Tianjin Univ Minist Educ Key Lab Coast Civil Struct Safety Tianjin Peoples R China

For shaking table tests, it is essential to increase the density of the structure by adding artificial masses, which serves as an equivalent density. This modification ensures adherence to the dynamic similarity criterion. However, for underwater shaking table and wave tests, the density of water cannot change, and an increase in the equivalent density of the structure results in a distortion of the test simulation of the fluid-structure interaction. To solve this problem, an innovative similarity law is proposed for the design of fluid-structure models by changing the cross-sectional dimensions of the structure. A series of bidirectional underwater shaking table tests and unidirectional wave tests were conducted to validate the proposed similarity law, and the traditional similarity law was analyzed for comparison. The test results indicated that the traditional scale model predicted the hydrodynamic pressure acting on the prototype with an error of approximately 50%. In contrast, the proposed scale model reduced this error to about 10%. Furthermore, the relative errors in predicting the displacement, acceleration, and strain of the prototype using the proposed scale model were all below 15%. This demonstrated the reliability of the proposed similarity law applied in the test design for fluid-structure models in underwater shaking table and wave tests.

关键词： earthquake fluid-structure interaction similarity relation underwater shaking table test wave test

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Spatial-temporal evolution mechanism of underwater salvo of two slender bodies based on three degrees of freedom model

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OCEAN ENGINEERING 2025年 317卷

作者： Zhang, Lei Gu, Longming Kong, Xiangshao Wang, Shan Pei, Zhiyong Wuhan Univ Technol Sanya Sci & Educ Innovat Pk Sanya 572000 Hainan Peoples R China Wuhan Univ Technol Green & Smart River Sea Going Ship Cruise & Yacht Wuhan 430063 Hubei Peoples R China Univ Lisbon Ctr Marine Technol & Engn CENTEC Inst Super Ten Lisbon Portugal Wuhan Univ Technol Sch Naval Architecture Ocean & Energy Power Engn Wuhan 430063 Hubei Peoples R China

Although the underwater salvo is more efficient than the single launch, the flow-mediated interaction between slender bodies makes the launch more complicated. To address the highly nonlinearity in fluid-structure interactions and the coupling motions of structures, a numerical method is proposed for analyzing the underwater salvo of two slender bodies under transverse flow. The three-degree-of-freedom (3-DOF) motion model of structures, combined with the cavitation and collision models, is adopted. The model is initially validated and verified through a comparison with the experimental results. Subsequently, the applicability of the model in flows is analyzed, and the effects of the launch time interval (zt) and spatial interval (zs) on the salvo are discussed. The findings demonstrate the effectiveness of proposed model, particularly in high-speed transverse flow and the strong flow-mediated interaction. When z t and z s are large, the slender bodies are mainly affected by the transverse flow, reducing success of salvo due to the collision between the bodies and their barrels. It is recommended that z t = 0 with z s >= 2D (diameter of slender bodies) be employed to achieve both efficiency and success in the salvo. The peak pressures within the barrels especially when z t =0 should also be considered in the structural design.

关键词： Underwater salvo Cavitation phenomenon Three-degrees-of-freedom motion fluid-structure interaction Spatial-temporal evolution

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Dynamics of a flutter-excited articulated ichthyoid propulsor

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MECCANICA 2025年第4期60卷 1035-1052页

作者： Szmidt, Tomasz Polish Acad Sci Inst Fundamental Technol Res Pawinskiego 5B PL-02106 Warsaw Poland

A concept of an ichthyoid propulsor mimicking the undulating motion of a swimming fish is proposed and verified. The propulsor consists of an articulated fluid-conveying pipe with a triangular fin attached to its free end. A sufficiently high flow velocity in the propulsor leads to the instability of the system and the possible appearance of snake-like flutter vibrations. A dynamical model of the system is proposed. It is based on classical Benjamin's model of the dynamics of an articulated fluid-conveying pipe and Lighthill's elongated body theory, which quantifies hydrodynamic forces generated by the swimming fish. Parameters of the system for which the propulsor is subject to dynamic loss of stability, leading to the appearance of periodic flutter vibrations, are identified. Methods of bifurcation analysis, supported by numerical simulations, prove that the system can undergo a supercritical Hopf bifurcation. This soft self-excitation yields a stable limit cycle of the system, for which the thrust and lateral forces generated by the propulsor are calculated. It is shown that the mean value of the thrust is positive for a range of swimming speeds. The performance of the propulsor is assessed in relation to the swimming speed. The research may broaden knowledge about articulated pipes conveying fluid and support possible applications of the proposed propulsor.

关键词： Fish swimming fluid-structure interaction Articulated pipe Dynamic stability Hopf bifurcation

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Response of shear thickening fluids to high velocity ballistic impact

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INTERNATIONAL JOURNAL OF IMPACT ENGINEERING 2025年 200卷

作者： Long, Shuchang Chen, Huanming Yao, Xiaohu Liu, Tao South China Univ Technol Dept Engn Mech Guangzhou 510640 Guangdong Peoples R China Univ Nottingham Fac Engn Nottingham NG7 2RD England South China Univ Technol State Key Lab Subtrop Bldg & Urban Sci Guangzhou 510640 Guangdong Peoples R China Queen Mary Univ London Sch Engn & Mat Sci London E1 4NS England

Shear thickening fluid is widely used in protective structures due to its distinctive rheology, exhibiting a transition from liquid to a solid-like state under impact. This paper presents experimental, numerical and analytical studies on shear thickening fluid under ballistic impact. First of all, corn starch suspensions with various fractions were prepared, and their shear thickening properties were verified by rheological tests. Then, ballistic impact tests were carried out on the suspensions, and a finite element model was established for numerical calculation. Subsequently, a novel analytical model based on Oseen equations was proposed to predict the ballistic behavior of shear thickening fluid. The model was verified by both test and simulation results, and utilized in the parametric studies. The ballistic limit velocities of shear thickening fluid under different rheological parameters and impact conditions were obtained, which lays a foundation for the application of shear thickening fluid in impact resistant structures.

关键词： Shear thickening fluid Ballistic impact Numerical simulation Analytical model fluid-structure interaction

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Study on transient characteristics during closing process of large ball valve in pumped storage power station

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ENERGY 2025年 323卷

作者： Li, Xiaoqin Tang, Xuelin Wang, Yuanbo Liu, Qihang Zou, Mingde Li, Hao China Agr Univ Coll Water Resources & Civil Engn Beijing 100083 Peoples R China China Agr Univ Beijing Engn Res Ctr Safety & Energy Saving Techno Beijing 100083 Peoples R China Huadian Elect Power Res Inst CO LTD Hangzhou 310000 Peoples R China North China Univ Water Resources & Elect Power Zhengzhou 450000 Peoples R China China Southern Power Grid Energy Storage Co Ltd Guangzhou 510635 Peoples R China China Inst Atom Energy Beijing 102413 Peoples R China

The 1D MOC and 3D hydraulic transient are proposed respectively to investigate transient flow characteristics inside a ball valve, as well as the UFSI models for its relevant dynamic structural responses during ball-valve closing and load rejection in a pumped storage power station. The historical transient-pressure evolution is in good agreement with the experimental data with the corresponding relative errors of 0.37 % and 7.36 % respectively. Based on 3D standard k-epsilon and sliding-grid technology, there are six vortices in the Y = 0 m plane and two anticlockwise vortices in the X = 0 m plane, and the predicted steady-resistance coefficients are closer to the experimental data compared with the predicted unsteady ones. The predicted pressure evolutions are both consistent with the results by 1D MOC and the experimental data, but pressure fluctuations can be captured, compared to the experimental data, the corresponding relative errors are 0.23 % and 0.37 % respectively. Based on dynamically applied pressure load along with sliding-grid technology and the USFI, compared to the experimental data, all these predicted maximum relative errors including circumferential dynamic stress, axial dynamic stress, axial displacement, vertical displacement, the accelerations at two monitoring points are 35.7 %, 17.3 %, 29.42 %, 8.82 %, 38.46 % and 4.45 % respectively, which are within the allowable safe range.

关键词： Ball valve Pumped storage power station Transient flow fluid-structure interaction

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Effect of Epoxy Material Viscosity and Gold Wire Configuration on Light-Emitting Diode Encapsulation Process

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JOURNAL OF ELECTRONIC MATERIALS 2025年第4期54卷 2601-2617页

作者： Khor, C. Y. Aziz, Mohd Sharizal Abdul Qi, Chooi Jing Lim, Xing Qi Ishak, M. H. H. Salleh, Mohd Arif Anuar Mohd Univ Malaysia Perlis Fac Mech Engn & Technol Arau 02600 Perlis Malaysia Univ Sains Malaysia Sch Mech Engn Engn Campus Nibong Tebal 14300 Penang Malaysia Univ Sains Malaysia Sch Aerosp Engn Engn Campus Nibong Tebal 14300 Penang Malaysia Univ Malaysia Perlis Fac Chem Engn & Technol Arau Malaysia Perlis Malaysia

This paper investigates the impacts of epoxy material viscosity and different gold wire configurations on the total maximum deformation, maximum von Mises stress, and maximum equivalent elastic strain on the light-emitting diode (LED) encapsulation process. The simulation of the LED encapsulation process employed the Volume of fluid (VOF), fluid-structure interaction (FSI), and System Coupling methods within ANSYS software. The simulation results for an epoxy molding compound (EMC) with viscosity of 0.448 kg/ms were validated by an experiment. A grid independence test was run to determine the minimum mesh refinement required for the simulation. The results revealed that the final fluid profile of the EMC at 0.448 kg/ms conformed more closely to the experimental results than the other epoxies. The overall best performance of the wire configuration to the EMC on the LED encapsulation process, in descending order, was the square-loop, triangle-loop, S-loop, Q-loop, and M-loop. This study contributes to understanding the effects of epoxy materials and various gold wire configurations on key mechanical parameters in the LED encapsulation process, hence guiding LED manufacturers in selecting optimal epoxy materials and wire configurations to improve process reliability and performance.

关键词： LED encapsulation process wire configuration epoxy fluid-structure interaction

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Study on Acoustic-Vibration Characteristics and Noise Reduction Methods for Elbows

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PROCESSES 2025年第2期13卷 389-389页

作者： Zhang, Shi-Wan Wang, Fei Li, Cong Zhu, Si-Min Lan, Hui-Qing Beijing Jiaotong Univ Sch Mech Elect & Control Engn Beijing 100044 Peoples R China Infrastruct Construct Co Ltd China Xiongan Grp Baoding 071700 Peoples R China CRRC Qi Hang New Energy Technol Co Ltd Beijing 100039 Peoples R China Beijing Jiaotong Univ Tangshan Res Inst Tangshan 063000 Peoples R China

fluid pipelines with large flow changes often result in noise due to multi-physical interactions (fluid-structure and acoustic-vibration interactions) between the pulsating fluid and the pipe wall, especially at the elbows. Therefore, the acoustic-vibration characteristics and noise reduction methods of elbows are studied in this paper. Firstly, a two-way fluid-structure interaction (FSI) model is established to analyze the vibration characteristics of the elbow under water excitation. Maximum stress occurs at the elbow inlet, with maximum deformation in the elbow. Experimental validation confirms the model's accuracy. Secondly, the effects of water and structural parameters on elbow vibration are studied, revealing that increased water pressure, pulsating frequency, and flow rate intensify pipe vibration. Finally, an acoustic-vibration coupled model is built;the simulations suggest that increasing wall thickness and elbow radius and reducing elbow angle effectively reduce the noise level of the elbow. Using elastic supports and damping materials can reduce elbow noise by at least 26.3%. This study provides guidance for the noise reduction and structural optimization of elbows by coupled multi-physics.

关键词： fluid-structure interaction elbow modal analysis natural frequency noise

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