An investigation is undertaken of an integrated mechanical-electromagnetic coupling system consisting of a rigid vehicle with heave, roll, and pitch motions, four electromagnetic energy harvesters and four tires subje...An investigation is undertaken of an integrated mechanical-electromagnetic coupling system consisting of a rigid vehicle with heave, roll, and pitch motions, four electromagnetic energy harvesters and four tires subject to uneven road excitations in order to improve the passengers' riding comfort and harvest the lost engine energy due to uneven roads. Following the derived mathematical formulations and the proposed solution approaches, the numerical simulations of this interaction system subject to a continuous sinusoidal road excitation and a single ramp impact are completed. The simulation results are presented as the dynamic response curves in the forms of the frequency spectrum and the time history, which reveals the complex interaction characteristics of the system for vibration reductions and energy harvesting performance. It has addressed the coupling effects on the dynamic characteristics of the integrated system caused by: (1) the natural modes and frequencies of the vehicle; (2) the vehicle rolling and pitching motions; (3) different road excitations on four wheels; (4) the time delay of a road ramp to impact both the front and rear wheels, etc., which cannot be tackled by an often used quarter vehicle model. The guidelines for engineering applications are given. The developed coupling model and the revealed concept provide a means with analysis idea to investigate the details of four energy harvester motions for electromagnetic suspension designs in order to replace the current passive vehicle isolators and to harvest the lost engine energy. Potential further research directions are suggested for readers to consider in the future.展开更多
Blast-induced traumatic brain injury(bTBI)presents a significant challenge for military personnel and civilians exposed to explosions.Beyond combat,bTBI can arise from civilian incidents like industrial accidents(chem...Blast-induced traumatic brain injury(bTBI)presents a significant challenge for military personnel and civilians exposed to explosions.Beyond combat,bTBI can arise from civilian incidents like industrial accidents(chemical-plant or mining blasts),accidental demolition blasts,fireworks factory explosions,and residential gas-leak detonations.The precise mechanisms by which blast waves damage the brain are still developing.Studies sug-gest that bTBI is primarily an interface-driven injury,where mechanical forces concentrate at anatomical boundaries including graywhite matter junctions,cortical sulci,cerebrospinal fluid(CsF)spaces,and peri-vascular structures.Recent research has shown that fluid structure interaction(FSI)simulations are instrumental in capturing shock wave transmission through the skull,CSF,and brain tissue,directly informing the design of protective gear.Here,we developed a high-resolution FSI model of the human head with approximately five million elements and detailed anatomical features(sulci,gyri,CsF compartments,vascular structures)to examine these biomechanical interactions.We employed Friedlander waveform to simulate the blast wave,with adjustments for attenuation through the skull and pressure transmission into the CSF and brain,with peak overpressures ranging from 100 to 1000 kPa and durations up to 6 ms.Our findings indicate that local CSF pressures dropping below its vapor pressure(around 90 kPa)can initiate cavitation,particularly within sulcal and ventricular spaces.This cavitation is accompanied by elevated shear stresses at adjacent graywhite matter interfaces,with strain rates exceeding 250 s^(-1),co-localizing with diffuse axonal injury(DAI)thresholds.Higher overpressures(500 kPa)also induced intraventricular cavitation and elevated periventricular strain rates.Blast orientation significantly influenced injury distribution,lateral blasts resulted in more diffuse stress fields,while frontal blasts localized damage to anterior cortical regions.展开更多
The numerical modelling of the interactions between water waves and floating structures is significant for different areas of the marine sector, especially seakeeping and prediction of wave-induced loads. Seakeeping a...The numerical modelling of the interactions between water waves and floating structures is significant for different areas of the marine sector, especially seakeeping and prediction of wave-induced loads. Seakeeping analysis involving severe flow fluctuations is still quite challenging even for the conventional RANS method. Particle method has been viewed as alternative for such analysis especially those involving deformable boundary, wave breaking and fluid fragmentation around hull shapes. In this paper, the weakly compressible smoothed particle hydrodynamics(WCSPH), a fully Lagrangian particle method, is applied to simulate the symmetric radiation problem for a stationary barge treated as a flexible body. This is carried out by imposing prescribed forced simple harmonic oscillations in heave, pitch and the two-and three-node distortion modes. The resultant,radiation force predictions, namely added mass and fluid damping coefficients, are compared with results from 3-D potential flow boundary element method and 3-D RANS CFD predictions, in order to verify the adopted modelling techniques for WCSPH.WCSPH were found to be in agreement with most results and could predict the fluid actions equally well in most cases.展开更多
基金supporting S. Zhou to visit University of Southampton for one year to engage in this researchHarbin Engineering University for supporting J. T. Xing to visit Harbin Engineering University (Grant HEUCF160104)
文摘An investigation is undertaken of an integrated mechanical-electromagnetic coupling system consisting of a rigid vehicle with heave, roll, and pitch motions, four electromagnetic energy harvesters and four tires subject to uneven road excitations in order to improve the passengers' riding comfort and harvest the lost engine energy due to uneven roads. Following the derived mathematical formulations and the proposed solution approaches, the numerical simulations of this interaction system subject to a continuous sinusoidal road excitation and a single ramp impact are completed. The simulation results are presented as the dynamic response curves in the forms of the frequency spectrum and the time history, which reveals the complex interaction characteristics of the system for vibration reductions and energy harvesting performance. It has addressed the coupling effects on the dynamic characteristics of the integrated system caused by: (1) the natural modes and frequencies of the vehicle; (2) the vehicle rolling and pitching motions; (3) different road excitations on four wheels; (4) the time delay of a road ramp to impact both the front and rear wheels, etc., which cannot be tackled by an often used quarter vehicle model. The guidelines for engineering applications are given. The developed coupling model and the revealed concept provide a means with analysis idea to investigate the details of four energy harvester motions for electromagnetic suspension designs in order to replace the current passive vehicle isolators and to harvest the lost engine energy. Potential further research directions are suggested for readers to consider in the future.
文摘Blast-induced traumatic brain injury(bTBI)presents a significant challenge for military personnel and civilians exposed to explosions.Beyond combat,bTBI can arise from civilian incidents like industrial accidents(chemical-plant or mining blasts),accidental demolition blasts,fireworks factory explosions,and residential gas-leak detonations.The precise mechanisms by which blast waves damage the brain are still developing.Studies sug-gest that bTBI is primarily an interface-driven injury,where mechanical forces concentrate at anatomical boundaries including graywhite matter junctions,cortical sulci,cerebrospinal fluid(CsF)spaces,and peri-vascular structures.Recent research has shown that fluid structure interaction(FSI)simulations are instrumental in capturing shock wave transmission through the skull,CSF,and brain tissue,directly informing the design of protective gear.Here,we developed a high-resolution FSI model of the human head with approximately five million elements and detailed anatomical features(sulci,gyri,CsF compartments,vascular structures)to examine these biomechanical interactions.We employed Friedlander waveform to simulate the blast wave,with adjustments for attenuation through the skull and pressure transmission into the CSF and brain,with peak overpressures ranging from 100 to 1000 kPa and durations up to 6 ms.Our findings indicate that local CSF pressures dropping below its vapor pressure(around 90 kPa)can initiate cavitation,particularly within sulcal and ventricular spaces.This cavitation is accompanied by elevated shear stresses at adjacent graywhite matter interfaces,with strain rates exceeding 250 s^(-1),co-localizing with diffuse axonal injury(DAI)thresholds.Higher overpressures(500 kPa)also induced intraventricular cavitation and elevated periventricular strain rates.Blast orientation significantly influenced injury distribution,lateral blasts resulted in more diffuse stress fields,while frontal blasts localized damage to anterior cortical regions.
基金funded by the Ministry of Higher Education(MOHE)of Malaysia under the Fundamental Research Grant Scheme(FRGS)No.FRGS17-042-0608
文摘The numerical modelling of the interactions between water waves and floating structures is significant for different areas of the marine sector, especially seakeeping and prediction of wave-induced loads. Seakeeping analysis involving severe flow fluctuations is still quite challenging even for the conventional RANS method. Particle method has been viewed as alternative for such analysis especially those involving deformable boundary, wave breaking and fluid fragmentation around hull shapes. In this paper, the weakly compressible smoothed particle hydrodynamics(WCSPH), a fully Lagrangian particle method, is applied to simulate the symmetric radiation problem for a stationary barge treated as a flexible body. This is carried out by imposing prescribed forced simple harmonic oscillations in heave, pitch and the two-and three-node distortion modes. The resultant,radiation force predictions, namely added mass and fluid damping coefficients, are compared with results from 3-D potential flow boundary element method and 3-D RANS CFD predictions, in order to verify the adopted modelling techniques for WCSPH.WCSPH were found to be in agreement with most results and could predict the fluid actions equally well in most cases.
