Traditional orthopedic metal implants,such as titanium(Ti),Ti alloys,and cobalt-chromium(Co-Cr)alloys,cannot be degraded in vivo.Fracture patients is must always suffer a second operation to remove the implants.Moreov...Traditional orthopedic metal implants,such as titanium(Ti),Ti alloys,and cobalt-chromium(Co-Cr)alloys,cannot be degraded in vivo.Fracture patients is must always suffer a second operation to remove the implants.Moreover,stress shielding,or stress protection occurs when traditional orthopedic metal implants are applied in fractures surgery.The mechanical shunt produced by traditional orthopedic metal implants can cause bone loss over time,resulting in decreased bone strength and delayed fracture healing.Biodegradable metals that‘biocorrode’are currently attracting significant interest in the orthopedics field due to their suitability as temporary implants.As one of the biodegradable metals,magnesium(Mg)and Mg alloys have gained interest in the field of medicine due to their low density,excellent biocompatibility,high bioresorbability,and proper mechanical properties.Additionally,Mg ions released from the metal implants can promote osteogenesis and angiogenesis during the degradation process in vivo,which is substantially better for orthopedic fixation than other bioinert metal materials.Therefore,this review focuses on the properties,fabrication,biological functions,and surface modification of Mg-based alloys as novel bioabsorbable biomaterials for orthopedic applications.展开更多
Numerical research of flow past a circular cylinder with a splitter at the subcritical Reynolds number region of 5 × 10~4—9 × 10~4 was researched based on Computational Fluid Dynamics(CFD) through solving t...Numerical research of flow past a circular cylinder with a splitter at the subcritical Reynolds number region of 5 × 10~4—9 × 10~4 was researched based on Computational Fluid Dynamics(CFD) through solving twodimensional incompressible unsteady Reynolds-averaged Navier-Stokes(URANS) equations with the shear stress transport(SST) k-ω turbulence model. Three different grid resolutions were employed in the verification and validation study of the adopted turbulence model. Various fluid characteristics such as Strouhal number, lift coefficient of the cylinder and the splitter with respect to various splitter lengths and different Reynolds numbers were investigated. It was revealed that the lift coefficient ratio of the splitter over the cylinder remains near 1.6 when the splitter length is 1.5—4 times the cylinder's diameter. Vortex shedding is strongly inhibited when the splitter length is greater than a critical value of around four times the cylinder's diameter. The phase difference of the lift coefficient on the upper and lower surface of the splitter varies between-30?and 30?. The maximal lift coefficients are reached when the splitter length is about 2 times the cylinder's diameter. Besides, the splitter length has little influence on the separation angle around the cylinder.展开更多
This contribution deals with the development of a three-node triangular plane finite element to analyze the transient hygroscopic behavior of 2/2 twill flax fabric-reinforced epoxy composite.Several plates of this mat...This contribution deals with the development of a three-node triangular plane finite element to analyze the transient hygroscopic behavior of 2/2 twill flax fabric-reinforced epoxy composite.Several plates of this material were fabricated using the vacuum infusion process and composite specimens were then cut and aged in tap water at room temperature until saturation.To simplify,a plane modelling of water diffusion in the aged specimens is adopted and Fick’s model is used to describe the water diffusion kinetics.To highlight the heterogeneity of the flax-epoxy samples,the twill flax fabrics waviness is modelled with a sinusoidal undulation.In particular,we show that the proposed finite element formulation allows estimating the flax fiber radial diffusion coefficient by an inverse approach.展开更多
In this paper an original method based on the link between a piecewise identifiability analysis and a piecewise numerical estimation is presented for estimating parameters of a phenomenological diesel engine combustio...In this paper an original method based on the link between a piecewise identifiability analysis and a piecewise numerical estimation is presented for estimating parameters of a phenomenological diesel engine combustion model. This model is used for design, validation and pre-tuning of engine control laws. A cascade algebro-differential elimination method is used for studying identifiability. This investigation is done by using input-output-parameter relationship. Then these relations are transformed by using iterated integration. They are combined with an original numerical derivative estimation based on distribution theory which gives explicit point-wise derivative?estimation formulas for each given order. Then new approximate relations, linking block of parameters and outputs (without derivative) are obtained. These relations are linear relatively to the blocks of parameters and yield a first estimation of parameters which is used as initial guess for a local optimization method (least square method and a local search genetic algorithm).展开更多
This work reveals that the addition of periodically distributed stitches to sandwich structure enables a significant reduction of vibration in stop-band and this new functionality is systematically investigated.Firstl...This work reveals that the addition of periodically distributed stitches to sandwich structure enables a significant reduction of vibration in stop-band and this new functionality is systematically investigated.Firstly,a finite element model which is capable of taking into consideration the three layers of the sandwich as well as the stitches is developed.The diagram of dispersion is calculated by applying Floquet-Bloch theorem to the boundaries of unit cell.With properly chosen properties of stitches,a stop-band for flexural wave is observed.This stop-band is further confirmed by the forced response of a large stitched sandwich panel under point excitation.The level of vibration in the stop-band is significantly reduced.The influence of the stitch rigidity and density on upper and lower limits of stop-band is also examined,which confirms that stitched sandwich can be tuned to mitigate vibration in a certain frequency band with appropriate stitch properties.These investigations have demonstrated the potential application of stitched sandwich in the area of vibration reduction.展开更多
The plastic flow behaviors of AA6061-T4 sheets at different temperatures(21-300°C)and strain rates(0.002-4 s^(-1))were studied.Significant nonlinear effects of temperature and strain rate on flow behaviors were r...The plastic flow behaviors of AA6061-T4 sheets at different temperatures(21-300°C)and strain rates(0.002-4 s^(-1))were studied.Significant nonlinear effects of temperature and strain rate on flow behaviors were revealed,as well as underlying micromechanical factors.Phenomenology and machine learning-based constitutive models were developed.Both models were formulated in the framework of a temperature-dependent linear combination regulated by a transition function to capture the evolution of strain-hardening behavior with increasing temperature.Novel mathematical functions for describing temperature and strain rate sensitivities were formulated for the phenomenological constitutive model.The threshold temperature related to microstructure evolution was considered in the modeling.A data-enrichment strategy based on extrapolating experimental data via classical strain hardening laws was adopted to improve neural network training.An efficient inverse identification strategy,focusing solely on the transition function,was proposed to enhance the prediction accuracy of post-necking deformation by both constitutive models.展开更多
Aqueous zinc-ion batteries provide a most promising alternative to the existing lithium-ion batteries due to their high theoretical capacity,intrinsic safety,and low cost.However,commercializing aqueous zinc-ion batte...Aqueous zinc-ion batteries provide a most promising alternative to the existing lithium-ion batteries due to their high theoretical capacity,intrinsic safety,and low cost.However,commercializing aqueous zinc-ion batteries suffer from dendritic growth and side reactions on the surface of metallic zinc,resulting in poor reversibility.To overcome this critical challenge,here,we report a one-step ultrafast laser processing method for fabricating three-dimensional micro-/nanostructures on zinc anodes to optimize zinc nucleation and deposition processes.It is demonstrated that the three-dimensional micro-/nanostructure with increased specific surface area significantly reduces nucleation overpotential,as well as preferentially absorbs zinc ions to prevent dendritic protuberances and corrosion.As a result,the presence of threedimensional micro-/nanostructures on the zinc metal delivers stable zinc plating/stripping beyond 2500 h(2 mA cm-2/1 mAh cm-2)in symmetric cells,a high Coulombic efficiency(99.71%)in half cells,and moreover an improved capacity retention(71.8%)is also observed in full cells.Equally intriguingly,the pouch cell with three-dimensional micro-/nanostructures can operate across various bending states without severely compromising performance.This work provides an effective strategy to construct ultrafine and high-precision three-dimensional micro-/nanostructures achieving highperformance zinc metal anodes and is expected to be of immediate benefit to other metal-based electrodes.展开更多
This paper presents a numerical investigation of ship manoeuvring under the combined effect of bank and propeller. The incompressible turbulent flow with free surface around the self-propelled hull form is simulated u...This paper presents a numerical investigation of ship manoeuvring under the combined effect of bank and propeller. The incompressible turbulent flow with free surface around the self-propelled hull form is simulated using a commercial CFD software （ANSYS-FLUENT）. In order to estimate the influence of the bank-propeller effect on the hydrodynamic forces acting on the ship, volume forces representing the propeller are added to Navier-Stokes equations. The numerical simulations are carried out using the equivalent of experiment conditions. The validation of the CFD model is performed by comparing the numerical results to the availa- ble experimental data. For this investigation, the impact of Ship-Bank distance and ship speed on the bank effect are tested with and without propeller. An additional parameter concerning the advance ratio of the propeller is also tested.展开更多
We consider waves generated by the passing of convoys in a restricted waterway. The magnitude of these waves depends mainly on the geometrical and kinematical parameters of the convoy, such as the speed and the hull g...We consider waves generated by the passing of convoys in a restricted waterway. The magnitude of these waves depends mainly on the geometrical and kinematical parameters of the convoy, such as the speed and the hull geometry. The objective of this study is to predict the relationship between these geometrical and kinematical parameters and the amplitude of ship-generated waves as well as the water plane drawdown. Numerical simulations are conducted by solving the 3-D Navier-Stokes equations along with the standard k-c model for turbulent processes. The results are compared first with the empirical model and second with experimental measurements performed by the French company Compagnie National du Rhone （CNR）.展开更多
In this paper, a numerical method based on a coupling between a mathematical model of nonlinear transient ship manoeuvring motion in the horizontal plane and Mathematical Programming （MP） techniques is proposed. The...In this paper, a numerical method based on a coupling between a mathematical model of nonlinear transient ship manoeuvring motion in the horizontal plane and Mathematical Programming （MP） techniques is proposed. The aim of the proposed procedure is an efficient estimation of optimal ship hydrodynamic parameters in a dynamic model at the early design stage. The proposed procedure has been validated through turning circle and zigzag manoeuvres based on experimental data of sea trials of the 190 000- dwt oil tanker. Comparisons between experimental and computed data show a good agreement of overall tendency in manoeuvring traiectories.展开更多
The duration of ship-generated waves （wake waves） and accelerated currents can generate significant influences on the sediment transport. A 3-D numerical model is presented to estimate these effects. The hydrodynami...The duration of ship-generated waves （wake waves） and accelerated currents can generate significant influences on the sediment transport. A 3-D numerical model is presented to estimate these effects. The hydrodynamic model is the 3-D Reynolds averaged Navier-Stokes （RANS） equations including the standard k - ε model while the 3-D convection-diffusion model is for the resuspended sediment transport. This hydro-sedimentary model is firstly validated with the trench experimental results, and then applied to the open channel with a moving ship. The computed results demonstrate that the resuspension generation mainly depends on ship speeds, barge number, and the relative distance away from ship. The acceleration effects of ship on the sediment transport are analyzed as well.展开更多
This contribution presents a multidisciplinary review of the so-called field-dependent nonlinear piezoelectricity.It starts with an introduction that poses the literature analysis framework,through defining this opera...This contribution presents a multidisciplinary review of the so-called field-dependent nonlinear piezoelectricity.It starts with an introduction that poses the literature analysis framework,through defining this operational(that is oftenmet in practice)piezoelectric field-dependent nonlinearity.Indeed,the latter is a less known phenomenon although it is inherent to stress-free actuation responses of corresponding smart materials,actuators and structures.Then,related experimental observations from piezoelectric materials,actuator devices and smart structures tests are multidisciplinary surveyed for understanding the underlying mechanisms of the encountered field-dependent nonlinearity.Next,empirical material and numerical structural modelling and simulation approaches are critically reviewed from,respectively,the constitutive and finite element analysis points of view.Summary conclusions and few future directions for research are finally provided as a closure.It is worth mentioning that,although it is concise(retains only experiments and experimentally-correlated models and simulations),this critical review covers the last three decades period which is almost the whole age of the piezoelectric materials,actuators and smart structures research field.展开更多
The overtaking maneuver of two Esso Bernicia 1.9×10^5 DWT tankers was investigated using the system-based maneuvering method. The Brix model was incorporated to account for the overtaking interactions. Forces/mom...The overtaking maneuver of two Esso Bernicia 1.9×10^5 DWT tankers was investigated using the system-based maneuvering method. The Brix model was incorporated to account for the overtaking interactions. Forces/moment acting on the ship hulls and maneuvering motions were analyzed for both ships during the overtaking. The influences of the speed ratio and the passing distance were specially studied. Two fitting formulas for the minimum distance during the overtaking were finally established as functions of the two factors respectively. They can be used to predict the minimum distance during an overtaking maneuver under similar conditions to avoid marine accidents.展开更多
This article investigates the interest of using in-situ piezoelectric(PZT and PVDF)disks to perform real-time Structural Health Monitoring(SHM)of glass fiber-reinforced polymer composites submitted to var-ious tensile...This article investigates the interest of using in-situ piezoelectric(PZT and PVDF)disks to perform real-time Structural Health Monitoring(SHM)of glass fiber-reinforced polymer composites submitted to var-ious tensile loadings.The goal is to evaluate the working range and SHM potential of such embedded transducers for relatively simple mechanical loadings,with the long-term aim of using them to monitor complete 3D structures submitted to more complex loadings.SHM is performed acquiring the electrical capacitance variation of the embedded transducers.To study the potential links between the insitu capacitance signal and the global response of the loaded host specimens,a multi-instrumentation composed of external Nondestructive Testing techniques was implemented on the surfaces of the specimens to search for multi-physical couplings between these external measurements and the capacitance curves.Results confirmed the non-intrusiveness of the embedded transducers,and allowed estimating their working domain.PZT capacitance signal follows well the mechanical loadings,but the piezoceramic transducer gets damaged after a determined relatively low strain level due to its brittleness.The limits of this working domain are extended by using a stretchable PolyVinylidene Fluoride(PVDF)polymer transducer,allowing this one to perform in-situ and real-time SHM of its host tensile specimens until failure.展开更多
The maneuvering simulation is carried out through the continuous captive model test and the system dynamics approach.The mathematical maneuvering group(MMG)model is implemented in the virtual captive model tests by us...The maneuvering simulation is carried out through the continuous captive model test and the system dynamics approach.The mathematical maneuvering group(MMG)model is implemented in the virtual captive model tests by using the computational fluid dynamics(CFD)techniques.The oblique towing test(OTT),the circular motion test(CMT),the rudder force test and the open water test are performed to obtain the hydrodynamic derivatives of the hull,the rudder and the propeller,and the results are validated by experimental data.By designing the tests,the number of cases is reduced to a low level,to allow us to evaluate the maneuverability with a low cost and in a short time.Using these obtained coefficients,the system-based maneuvering simulations are conducted to calculate the position and the attitude of the ship,with results in agreement with the free running test results.This procedure can also be used for other hull forms,with reduced workload and with convenience for maneuvering simulation tasks.展开更多
This paper presents a FEM analysis of a membrane-based Surface Acoustic Wave(SAW)sensor.The sensor is a 2.45GHz Reflective Delay Line(R-DL)based on Lithium Niobate(LiNbO_(3)).As the wave propagation time is much small...This paper presents a FEM analysis of a membrane-based Surface Acoustic Wave(SAW)sensor.The sensor is a 2.45GHz Reflective Delay Line(R-DL)based on Lithium Niobate(LiNbO_(3)).As the wave propagation time is much smaller than the typical time constant of the phenomena to be monitored(deformation,temperature change etc.),the analysis can be performed in three successive steps.First,a static FEM study of the complete sensor(housing included)is carried out,to compute the temperature,stress and strain fields generated in the sensitive area by the measured parameters(pressure,temperature,etc.).Then,a dynamic electro-mechanical study of the R-DL is performed.The simulation takes the previously computed fields into account,which makes it possible to compute the sensor sensitivity to the measured parameters.The model takes advantage of the periodicity of the components of the R-DL to compute phenomenological parameters(Coupling-of-Mode parameters),which can later on be used to compute the electrical response of the sensor(step 3).In this paper,we focus on the first two steps.The COM parameters are extracted,under simultaneous thermal and mechanical stresses.Especially,the sensor sensitivity is obtained from the evolution of the velocity,under various stress configurations.展开更多
Smart materials are active materials that are nowadays commonly used for sensing,actuation,and transduction for structural noise(acoustic),shape(morphing)and vibration control and health monitoring of(in historical or...Smart materials are active materials that are nowadays commonly used for sensing,actuation,and transduction for structural noise(acoustic),shape(morphing)and vibration control and health monitoring of(in historical order)offshore petroleum,aerospace,aeronautic,mechanical,civil(including infra-structures and wind turbines)and biomedical engineering.More recently,they were also used for energy harvesting from environment for autonomously and wirelessly powering of various temperature or pressure monitoring sensors and some medical(fluidic)implants and(surgery)devices.展开更多
Propagation of light through curved graded index optical waveguides supporting an arbitrary high number of modes is investigated.The discussion is restricted to optical wave fields which are well confined within the c...Propagation of light through curved graded index optical waveguides supporting an arbitrary high number of modes is investigated.The discussion is restricted to optical wave fields which are well confined within the core region and losses through radiation are neglected.Using coupled mode theory formalism,two new forms for the propagation kernel for the transverse electric(TE)wave as it travels along a curved two-dimensional waveguide are presented.One form,involving the notion of“bend”modes,is shown to be attractive from a computational point of view as it allows an efficient numerical evaluation of the optical field for sharply bent waveguides.展开更多
基金supported by the National Natural Science Foundation of China(31870961,81501879)the Sino-German Center for Research Promotion(GZ1219)+1 种基金the International Cooperation Project of the Science and Technology Department of Sichuan Province(Grant No.2015HH0049,No.2017SZ0127,No.2020YFS0140)the National Clinical Research Center for Geriatrics,West China Hospital,Sichuan University(Z2018A11)。
文摘Traditional orthopedic metal implants,such as titanium(Ti),Ti alloys,and cobalt-chromium(Co-Cr)alloys,cannot be degraded in vivo.Fracture patients is must always suffer a second operation to remove the implants.Moreover,stress shielding,or stress protection occurs when traditional orthopedic metal implants are applied in fractures surgery.The mechanical shunt produced by traditional orthopedic metal implants can cause bone loss over time,resulting in decreased bone strength and delayed fracture healing.Biodegradable metals that‘biocorrode’are currently attracting significant interest in the orthopedics field due to their suitability as temporary implants.As one of the biodegradable metals,magnesium(Mg)and Mg alloys have gained interest in the field of medicine due to their low density,excellent biocompatibility,high bioresorbability,and proper mechanical properties.Additionally,Mg ions released from the metal implants can promote osteogenesis and angiogenesis during the degradation process in vivo,which is substantially better for orthopedic fixation than other bioinert metal materials.Therefore,this review focuses on the properties,fabrication,biological functions,and surface modification of Mg-based alloys as novel bioabsorbable biomaterials for orthopedic applications.
基金the National Natural Science Foundation of China(Nos.51179159 and 61572404)
文摘Numerical research of flow past a circular cylinder with a splitter at the subcritical Reynolds number region of 5 × 10~4—9 × 10~4 was researched based on Computational Fluid Dynamics(CFD) through solving twodimensional incompressible unsteady Reynolds-averaged Navier-Stokes(URANS) equations with the shear stress transport(SST) k-ω turbulence model. Three different grid resolutions were employed in the verification and validation study of the adopted turbulence model. Various fluid characteristics such as Strouhal number, lift coefficient of the cylinder and the splitter with respect to various splitter lengths and different Reynolds numbers were investigated. It was revealed that the lift coefficient ratio of the splitter over the cylinder remains near 1.6 when the splitter length is 1.5—4 times the cylinder's diameter. Vortex shedding is strongly inhibited when the splitter length is greater than a critical value of around four times the cylinder's diameter. The phase difference of the lift coefficient on the upper and lower surface of the splitter varies between-30?and 30?. The maximal lift coefficients are reached when the splitter length is about 2 times the cylinder's diameter. Besides, the splitter length has little influence on the separation angle around the cylinder.
文摘This contribution deals with the development of a three-node triangular plane finite element to analyze the transient hygroscopic behavior of 2/2 twill flax fabric-reinforced epoxy composite.Several plates of this material were fabricated using the vacuum infusion process and composite specimens were then cut and aged in tap water at room temperature until saturation.To simplify,a plane modelling of water diffusion in the aged specimens is adopted and Fick’s model is used to describe the water diffusion kinetics.To highlight the heterogeneity of the flax-epoxy samples,the twill flax fabrics waviness is modelled with a sinusoidal undulation.In particular,we show that the proposed finite element formulation allows estimating the flax fiber radial diffusion coefficient by an inverse approach.
文摘In this paper an original method based on the link between a piecewise identifiability analysis and a piecewise numerical estimation is presented for estimating parameters of a phenomenological diesel engine combustion model. This model is used for design, validation and pre-tuning of engine control laws. A cascade algebro-differential elimination method is used for studying identifiability. This investigation is done by using input-output-parameter relationship. Then these relations are transformed by using iterated integration. They are combined with an original numerical derivative estimation based on distribution theory which gives explicit point-wise derivative?estimation formulas for each given order. Then new approximate relations, linking block of parameters and outputs (without derivative) are obtained. These relations are linear relatively to the blocks of parameters and yield a first estimation of parameters which is used as initial guess for a local optimization method (least square method and a local search genetic algorithm).
文摘This work reveals that the addition of periodically distributed stitches to sandwich structure enables a significant reduction of vibration in stop-band and this new functionality is systematically investigated.Firstly,a finite element model which is capable of taking into consideration the three layers of the sandwich as well as the stitches is developed.The diagram of dispersion is calculated by applying Floquet-Bloch theorem to the boundaries of unit cell.With properly chosen properties of stitches,a stop-band for flexural wave is observed.This stop-band is further confirmed by the forced response of a large stitched sandwich panel under point excitation.The level of vibration in the stop-band is significantly reduced.The influence of the stitch rigidity and density on upper and lower limits of stop-band is also examined,which confirms that stitched sandwich can be tuned to mitigate vibration in a certain frequency band with appropriate stitch properties.These investigations have demonstrated the potential application of stitched sandwich in the area of vibration reduction.
文摘The plastic flow behaviors of AA6061-T4 sheets at different temperatures(21-300°C)and strain rates(0.002-4 s^(-1))were studied.Significant nonlinear effects of temperature and strain rate on flow behaviors were revealed,as well as underlying micromechanical factors.Phenomenology and machine learning-based constitutive models were developed.Both models were formulated in the framework of a temperature-dependent linear combination regulated by a transition function to capture the evolution of strain-hardening behavior with increasing temperature.Novel mathematical functions for describing temperature and strain rate sensitivities were formulated for the phenomenological constitutive model.The threshold temperature related to microstructure evolution was considered in the modeling.A data-enrichment strategy based on extrapolating experimental data via classical strain hardening laws was adopted to improve neural network training.An efficient inverse identification strategy,focusing solely on the transition function,was proposed to enhance the prediction accuracy of post-necking deformation by both constitutive models.
基金support of the National Key Research and Development Program(No.2023YFB4605102)National Natural Science Foundation of China(No.52105437)+2 种基金Heilongjiang Touyan Team(No.HITTY-20190036)Shanghai Aerospace Science and Technology Innovation Fund(No.SAST2021-067)National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(Grant RS-2023-00235596,RS-2023-00243788).
文摘Aqueous zinc-ion batteries provide a most promising alternative to the existing lithium-ion batteries due to their high theoretical capacity,intrinsic safety,and low cost.However,commercializing aqueous zinc-ion batteries suffer from dendritic growth and side reactions on the surface of metallic zinc,resulting in poor reversibility.To overcome this critical challenge,here,we report a one-step ultrafast laser processing method for fabricating three-dimensional micro-/nanostructures on zinc anodes to optimize zinc nucleation and deposition processes.It is demonstrated that the three-dimensional micro-/nanostructure with increased specific surface area significantly reduces nucleation overpotential,as well as preferentially absorbs zinc ions to prevent dendritic protuberances and corrosion.As a result,the presence of threedimensional micro-/nanostructures on the zinc metal delivers stable zinc plating/stripping beyond 2500 h(2 mA cm-2/1 mAh cm-2)in symmetric cells,a high Coulombic efficiency(99.71%)in half cells,and moreover an improved capacity retention(71.8%)is also observed in full cells.Equally intriguingly,the pouch cell with three-dimensional micro-/nanostructures can operate across various bending states without severely compromising performance.This work provides an effective strategy to construct ultrafine and high-precision three-dimensional micro-/nanostructures achieving highperformance zinc metal anodes and is expected to be of immediate benefit to other metal-based electrodes.
文摘This paper presents a numerical investigation of ship manoeuvring under the combined effect of bank and propeller. The incompressible turbulent flow with free surface around the self-propelled hull form is simulated using a commercial CFD software （ANSYS-FLUENT）. In order to estimate the influence of the bank-propeller effect on the hydrodynamic forces acting on the ship, volume forces representing the propeller are added to Navier-Stokes equations. The numerical simulations are carried out using the equivalent of experiment conditions. The validation of the CFD model is performed by comparing the numerical results to the availa- ble experimental data. For this investigation, the impact of Ship-Bank distance and ship speed on the bank effect are tested with and without propeller. An additional parameter concerning the advance ratio of the propeller is also tested.
基金sponsored by the program of UT-INSA-CSC(The program between UTC and the China Scholarship Council)
文摘We consider waves generated by the passing of convoys in a restricted waterway. The magnitude of these waves depends mainly on the geometrical and kinematical parameters of the convoy, such as the speed and the hull geometry. The objective of this study is to predict the relationship between these geometrical and kinematical parameters and the amplitude of ship-generated waves as well as the water plane drawdown. Numerical simulations are conducted by solving the 3-D Navier-Stokes equations along with the standard k-c model for turbulent processes. The results are compared first with the empirical model and second with experimental measurements performed by the French company Compagnie National du Rhone （CNR）.
文摘In this paper, a numerical method based on a coupling between a mathematical model of nonlinear transient ship manoeuvring motion in the horizontal plane and Mathematical Programming （MP） techniques is proposed. The aim of the proposed procedure is an efficient estimation of optimal ship hydrodynamic parameters in a dynamic model at the early design stage. The proposed procedure has been validated through turning circle and zigzag manoeuvres based on experimental data of sea trials of the 190 000- dwt oil tanker. Comparisons between experimental and computed data show a good agreement of overall tendency in manoeuvring traiectories.
文摘The duration of ship-generated waves （wake waves） and accelerated currents can generate significant influences on the sediment transport. A 3-D numerical model is presented to estimate these effects. The hydrodynamic model is the 3-D Reynolds averaged Navier-Stokes （RANS） equations including the standard k - ε model while the 3-D convection-diffusion model is for the resuspended sediment transport. This hydro-sedimentary model is firstly validated with the trench experimental results, and then applied to the open channel with a moving ship. The computed results demonstrate that the resuspension generation mainly depends on ship speeds, barge number, and the relative distance away from ship. The acceleration effects of ship on the sediment transport are analyzed as well.
文摘This contribution presents a multidisciplinary review of the so-called field-dependent nonlinear piezoelectricity.It starts with an introduction that poses the literature analysis framework,through defining this operational(that is oftenmet in practice)piezoelectric field-dependent nonlinearity.Indeed,the latter is a less known phenomenon although it is inherent to stress-free actuation responses of corresponding smart materials,actuators and structures.Then,related experimental observations from piezoelectric materials,actuator devices and smart structures tests are multidisciplinary surveyed for understanding the underlying mechanisms of the encountered field-dependent nonlinearity.Next,empirical material and numerical structural modelling and simulation approaches are critically reviewed from,respectively,the constitutive and finite element analysis points of view.Summary conclusions and few future directions for research are finally provided as a closure.It is worth mentioning that,although it is concise(retains only experiments and experimentally-correlated models and simulations),this critical review covers the last three decades period which is almost the whole age of the piezoelectric materials,actuators and smart structures research field.
文摘The overtaking maneuver of two Esso Bernicia 1.9×10^5 DWT tankers was investigated using the system-based maneuvering method. The Brix model was incorporated to account for the overtaking interactions. Forces/moment acting on the ship hulls and maneuvering motions were analyzed for both ships during the overtaking. The influences of the speed ratio and the passing distance were specially studied. Two fitting formulas for the minimum distance during the overtaking were finally established as functions of the two factors respectively. They can be used to predict the minimum distance during an overtaking maneuver under similar conditions to avoid marine accidents.
文摘This article investigates the interest of using in-situ piezoelectric(PZT and PVDF)disks to perform real-time Structural Health Monitoring(SHM)of glass fiber-reinforced polymer composites submitted to var-ious tensile loadings.The goal is to evaluate the working range and SHM potential of such embedded transducers for relatively simple mechanical loadings,with the long-term aim of using them to monitor complete 3D structures submitted to more complex loadings.SHM is performed acquiring the electrical capacitance variation of the embedded transducers.To study the potential links between the insitu capacitance signal and the global response of the loaded host specimens,a multi-instrumentation composed of external Nondestructive Testing techniques was implemented on the surfaces of the specimens to search for multi-physical couplings between these external measurements and the capacitance curves.Results confirmed the non-intrusiveness of the embedded transducers,and allowed estimating their working domain.PZT capacitance signal follows well the mechanical loadings,but the piezoceramic transducer gets damaged after a determined relatively low strain level due to its brittleness.The limits of this working domain are extended by using a stretchable PolyVinylidene Fluoride(PVDF)polymer transducer,allowing this one to perform in-situ and real-time SHM of its host tensile specimens until failure.
基金supported by the National Natural Science Foundation of China(Grant Nos.51979226,52171324).
文摘The maneuvering simulation is carried out through the continuous captive model test and the system dynamics approach.The mathematical maneuvering group(MMG)model is implemented in the virtual captive model tests by using the computational fluid dynamics(CFD)techniques.The oblique towing test(OTT),the circular motion test(CMT),the rudder force test and the open water test are performed to obtain the hydrodynamic derivatives of the hull,the rudder and the propeller,and the results are validated by experimental data.By designing the tests,the number of cases is reduced to a low level,to allow us to evaluate the maneuverability with a low cost and in a short time.Using these obtained coefficients,the system-based maneuvering simulations are conducted to calculate the position and the attitude of the ship,with results in agreement with the free running test results.This procedure can also be used for other hull forms,with reduced workload and with convenience for maneuvering simulation tasks.
基金This project has been partly supported by the COMET K1 center ASSIC Austrian Smart Systems Integration Research Center.The COMET‘Competence Centers for Excellent Technologies’program is supported by BMVIT,BMWFW and the federal provinces of Carinthia and Styria.
文摘This paper presents a FEM analysis of a membrane-based Surface Acoustic Wave(SAW)sensor.The sensor is a 2.45GHz Reflective Delay Line(R-DL)based on Lithium Niobate(LiNbO_(3)).As the wave propagation time is much smaller than the typical time constant of the phenomena to be monitored(deformation,temperature change etc.),the analysis can be performed in three successive steps.First,a static FEM study of the complete sensor(housing included)is carried out,to compute the temperature,stress and strain fields generated in the sensitive area by the measured parameters(pressure,temperature,etc.).Then,a dynamic electro-mechanical study of the R-DL is performed.The simulation takes the previously computed fields into account,which makes it possible to compute the sensor sensitivity to the measured parameters.The model takes advantage of the periodicity of the components of the R-DL to compute phenomenological parameters(Coupling-of-Mode parameters),which can later on be used to compute the electrical response of the sensor(step 3).In this paper,we focus on the first two steps.The COM parameters are extracted,under simultaneous thermal and mechanical stresses.Especially,the sensor sensitivity is obtained from the evolution of the velocity,under various stress configurations.
文摘Smart materials are active materials that are nowadays commonly used for sensing,actuation,and transduction for structural noise(acoustic),shape(morphing)and vibration control and health monitoring of(in historical order)offshore petroleum,aerospace,aeronautic,mechanical,civil(including infra-structures and wind turbines)and biomedical engineering.More recently,they were also used for energy harvesting from environment for autonomously and wirelessly powering of various temperature or pressure monitoring sensors and some medical(fluidic)implants and(surgery)devices.
文摘Propagation of light through curved graded index optical waveguides supporting an arbitrary high number of modes is investigated.The discussion is restricted to optical wave fields which are well confined within the core region and losses through radiation are neglected.Using coupled mode theory formalism,two new forms for the propagation kernel for the transverse electric(TE)wave as it travels along a curved two-dimensional waveguide are presented.One form,involving the notion of“bend”modes,is shown to be attractive from a computational point of view as it allows an efficient numerical evaluation of the optical field for sharply bent waveguides.
