Ground resonance is a specific unstable vibration caused by the modal coupling between the blades and fuselage of a helicopter structural system. On the other hand, the unstable vibration in a standard rotor model can also be triggered by lateral-torsional coupling. This paper studies the consistency of instability mechanisms between the ground resonance and the lateral-torsional coupling vibration. Based on the two-dimensional equivalent model of helicopter system, the critical elements leading to the ground resonance are firstly studied by modal analysis. Comparison between the ground resonance and the lateral-torsional coupling vibration is then performed in two aspects: critical elements causing instability in dynamic matrices and modal shapes in the modal coupling ranges. Results demonstrate that the instability mechanism of the ground resonance is consistent with which of the lateral-torsional coupling vibration. The reason why similar instability does not occur in the general rotor system with elastic supports is also clarified.
{"title":"The Consistency of Helicopter ‘Ground Resonance’ and the Unstable Lateral-Torsional Vibration in Standard Rotor Systems","authors":"Xin Qian, Yu Fan, Lin Li, Wenjun Wang","doi":"10.1115/imece2021-70169","DOIUrl":"https://doi.org/10.1115/imece2021-70169","url":null,"abstract":"\u0000 Ground resonance is a specific unstable vibration caused by the modal coupling between the blades and fuselage of a helicopter structural system. On the other hand, the unstable vibration in a standard rotor model can also be triggered by lateral-torsional coupling. This paper studies the consistency of instability mechanisms between the ground resonance and the lateral-torsional coupling vibration. Based on the two-dimensional equivalent model of helicopter system, the critical elements leading to the ground resonance are firstly studied by modal analysis. Comparison between the ground resonance and the lateral-torsional coupling vibration is then performed in two aspects: critical elements causing instability in dynamic matrices and modal shapes in the modal coupling ranges. Results demonstrate that the instability mechanism of the ground resonance is consistent with which of the lateral-torsional coupling vibration. The reason why similar instability does not occur in the general rotor system with elastic supports is also clarified.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78137320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Motion response prediction at the design stage of a vessel can ameliorate the performance of any floating structure. Many naval operations and offshore activities such as oil and gas exploration, aircraft landing, mooring, berthing, etc. are motion-sensitive. Hence, it is apparent, that motion response plays a vital role in these cases and, to keep it to a minimum while designing a vessel, motion prediction is essential. Traditional ways of predicting motion response require a wide range of parameters, which may not be available at the early stage of the design. Besides a significant amount of computation time and human efforts are also necessary. Artificial Intelligence can be beneficial to overcome the aforesaid issues. In this research, the architecture of the neural network model has been explored. A hybrid model is developed using Artificial Neural Network and Lewis Form method along with the numerical solution. The principal particulars of vessels and heave motion responses have been fed to the model to learn the behavior of the vessels with respect to time in presence of excitation force. Based on 15 to 30 seconds of simulation, the trained model can predict the heave motion of a vessel efficiently.
{"title":"Heave Motion Prediction of Rectangular Floating Barge Using Artificial Neural Network","authors":"Z. I. Awal, Nafisa Mehtaj, Rakin Ishmam Pranto","doi":"10.1115/imece2021-73311","DOIUrl":"https://doi.org/10.1115/imece2021-73311","url":null,"abstract":"\u0000 Motion response prediction at the design stage of a vessel can ameliorate the performance of any floating structure. Many naval operations and offshore activities such as oil and gas exploration, aircraft landing, mooring, berthing, etc. are motion-sensitive. Hence, it is apparent, that motion response plays a vital role in these cases and, to keep it to a minimum while designing a vessel, motion prediction is essential. Traditional ways of predicting motion response require a wide range of parameters, which may not be available at the early stage of the design. Besides a significant amount of computation time and human efforts are also necessary. Artificial Intelligence can be beneficial to overcome the aforesaid issues. In this research, the architecture of the neural network model has been explored. A hybrid model is developed using Artificial Neural Network and Lewis Form method along with the numerical solution. The principal particulars of vessels and heave motion responses have been fed to the model to learn the behavior of the vessels with respect to time in presence of excitation force. Based on 15 to 30 seconds of simulation, the trained model can predict the heave motion of a vessel efficiently.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77969135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The SCARA robot has been extensively used for industrial applications. The motivation behind this research is to propose a SCARA variant as an alternative, with the popularity and applications of a SCARA robot. The main objective is to relocate the vertical prismatic joint and study the computational dynamics of the SCARA variant and the performances. The SCARA variant has been analyzed for the forward and inverse kinematics based on the transformation matrix method. The dynamic model for the SCARA variant has been developed by using the Lagrangian method. The dynamic model is compared to the standard SCARA, it has been found that the dynamic models are very similar apart from the mass inertia and Coriolis matrices having terms in columns 2 & 3 exchanged. In this paper, linear and nonlinear trajectories, such as straight line, ellipse, and circular trajectories have been selected in the simulation study. Consistent results for torque requirements have been observed with the linear trajectory having the least values, followed by ellipse, and the circular trajectory.
{"title":"Design and Modelling of SCARA Robot Variant","authors":"Manjeet Tummalapalli, Puren Ouyang, Johnny Bahri","doi":"10.1115/imece2021-73288","DOIUrl":"https://doi.org/10.1115/imece2021-73288","url":null,"abstract":"\u0000 The SCARA robot has been extensively used for industrial applications. The motivation behind this research is to propose a SCARA variant as an alternative, with the popularity and applications of a SCARA robot. The main objective is to relocate the vertical prismatic joint and study the computational dynamics of the SCARA variant and the performances. The SCARA variant has been analyzed for the forward and inverse kinematics based on the transformation matrix method.\u0000 The dynamic model for the SCARA variant has been developed by using the Lagrangian method. The dynamic model is compared to the standard SCARA, it has been found that the dynamic models are very similar apart from the mass inertia and Coriolis matrices having terms in columns 2 & 3 exchanged. In this paper, linear and nonlinear trajectories, such as straight line, ellipse, and circular trajectories have been selected in the simulation study. Consistent results for torque requirements have been observed with the linear trajectory having the least values, followed by ellipse, and the circular trajectory.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76224357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper we report on the design of an apparatus to study the force distribution on flapping wings during hovering. We designed the system to use a well-known optical technique that measures the deflection of a wing along the wingspan using high speed cameras. Our motivation is to understand the generated aerodynamic forces on flapping wings to be able to design and control flapping flight robots. We are inspired in particular by the wing motion of hummingbirds and dragonflies. Dragonflies have two wings that move at an offset distance from each other and have the ability to rotate about its longitudinal axis in order to change the azimuth angle during its flapping motion. The knowledge gained from such a study can be used to design flapping wing flying robots.
{"title":"Design of an Apparatus to Measure Aerodynamic Forces During Flapping Wing Hovering","authors":"Vernon Fernandez, H. Vejdani, B. Jawad","doi":"10.1115/imece2021-73811","DOIUrl":"https://doi.org/10.1115/imece2021-73811","url":null,"abstract":"\u0000 In this paper we report on the design of an apparatus to study the force distribution on flapping wings during hovering. We designed the system to use a well-known optical technique that measures the deflection of a wing along the wingspan using high speed cameras. Our motivation is to understand the generated aerodynamic forces on flapping wings to be able to design and control flapping flight robots. We are inspired in particular by the wing motion of hummingbirds and dragonflies. Dragonflies have two wings that move at an offset distance from each other and have the ability to rotate about its longitudinal axis in order to change the azimuth angle during its flapping motion. The knowledge gained from such a study can be used to design flapping wing flying robots.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87935386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper studies the linear motion speed control problem of an underactuated spherical robot under unknown disturbances. A novel fractional fixed-time terminal sliding mode control with a nonlinear disturbance observer is proposed for the spherical robot to achieve fast stabilization and robust control performance. First, a novel fixed-time terminal sliding surface is proposed by adding a fractional differential operator in the traditional integer order fixed-time terminal sliding surface. A nonlinear disturbance observer is designed to estimate the unknown disturbances. Then a fractional hierarchical sliding mode speed controller is designed based on the novel fractional fixed-time terminal sliding surface and the nonlinear disturbance observer. Through the Lyapunov stability theorem, the boundedness of each sliding surface is achieved, and the stability of the whole system is guaranteed. The effectiveness of the proposed controller has been verified via simulation work. The simulation results show the fractional sliding mode controller has a shorter settling time and lower overshoot compared to an integer order sliding controller. When subjected to the abrupt changes of rolling friction, the fractional hierarchical sliding mode controller shows stronger robustness than the integer order one.
{"title":"A Novel Fractional Fixed-Time Sliding Mode Control Method for Spherical Robot Linear Motion Speed Control","authors":"Zhou Ting, Xu Yugong, Wu Bin","doi":"10.1115/imece2021-70264","DOIUrl":"https://doi.org/10.1115/imece2021-70264","url":null,"abstract":"\u0000 This paper studies the linear motion speed control problem of an underactuated spherical robot under unknown disturbances. A novel fractional fixed-time terminal sliding mode control with a nonlinear disturbance observer is proposed for the spherical robot to achieve fast stabilization and robust control performance. First, a novel fixed-time terminal sliding surface is proposed by adding a fractional differential operator in the traditional integer order fixed-time terminal sliding surface. A nonlinear disturbance observer is designed to estimate the unknown disturbances. Then a fractional hierarchical sliding mode speed controller is designed based on the novel fractional fixed-time terminal sliding surface and the nonlinear disturbance observer. Through the Lyapunov stability theorem, the boundedness of each sliding surface is achieved, and the stability of the whole system is guaranteed. The effectiveness of the proposed controller has been verified via simulation work. The simulation results show the fractional sliding mode controller has a shorter settling time and lower overshoot compared to an integer order sliding controller. When subjected to the abrupt changes of rolling friction, the fractional hierarchical sliding mode controller shows stronger robustness than the integer order one.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88248259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
When iron ore and coal cargo are unloaded onto a ship, some of that cargo falls, and can eventually pollute the sea. As a countermeasure, workers clean the cargo hold doors, but this dangerous activity has caused fatal accidents due to falls. The use of robots in cleaning work has a problem. That is the occurrence of slippage when a compact and lightweight robot attempts to clear a heavy obstacle. In this research, we aim to suppress slippage by controlling the driving force of the cleaning robot according to changes in the suiface conditions. We proposed a slip suppression control system that achieves slip suppression by controlling the driving force according to the estimated variation of the friction coefficient. In order to verify the effectiveness of the proposed method, we produced a test course with essential features of a work site, and then we carried out a heavy load transport test of the cleaning robot. We demonstrated an effective slip suppression system for the lightweight robot that can respond to variable friction on a suiface that changes as it is cleaned.
{"title":"Slip Suppression Control to Improve the Performance of a Mobile Cleaning Robot Under Different Road Surface Conditions","authors":"Tsubasa Yamatogawa, Tatsuhiro Morimoto, Takaya Tsuno, Tian Shen, K. Yano, Toshihiko Arima, Shigeru Fukui","doi":"10.1115/imece2021-69383","DOIUrl":"https://doi.org/10.1115/imece2021-69383","url":null,"abstract":"\u0000 When iron ore and coal cargo are unloaded onto a ship, some of that cargo falls, and can eventually pollute the sea. As a countermeasure, workers clean the cargo hold doors, but this dangerous activity has caused fatal accidents due to falls. The use of robots in cleaning work has a problem. That is the occurrence of slippage when a compact and lightweight robot attempts to clear a heavy obstacle. In this research, we aim to suppress slippage by controlling the driving force of the cleaning robot according to changes in the suiface conditions. We proposed a slip suppression control system that achieves slip suppression by controlling the driving force according to the estimated variation of the friction coefficient. In order to verify the effectiveness of the proposed method, we produced a test course with essential features of a work site, and then we carried out a heavy load transport test of the cleaning robot. We demonstrated an effective slip suppression system for the lightweight robot that can respond to variable friction on a suiface that changes as it is cleaned.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90743103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Alcheikh, H. Ouakad, Sofiane Ben Mbarek, M. Younis
In this paper, we investigate experimentally and theoretically the linear coupling between the first two symmetric and anti-symmetric modes of an electrothermally and electrostatically actuated in-plane V-shaped micro-beam. The micro-beam is fabricated from highly doped silicon and is sandwiched between four electrodes to electrostatically activate both modes of vibrations. When tuning the electrothermal voltage, the natural frequencies of the two modes approach each other until they cross. Under electrostatic actuation, it is shown experimentally that the system undergoes a transition between modes crossing to veering. In addition, an analytical study is presented based on a Galerkin-based reduced-order model of a nonlinear Euler–Bernoulli shallow arch beam equation. The analytical results are compared to experimental data showing excellent agreement.
{"title":"Investigations Into the Linear Coupling Between Symmetric and Anti-Symmetric Modes of V-Shaped MEMS Resonators Under Electrostatic Perturbation","authors":"N. Alcheikh, H. Ouakad, Sofiane Ben Mbarek, M. Younis","doi":"10.1115/imece2021-73535","DOIUrl":"https://doi.org/10.1115/imece2021-73535","url":null,"abstract":"\u0000 In this paper, we investigate experimentally and theoretically the linear coupling between the first two symmetric and anti-symmetric modes of an electrothermally and electrostatically actuated in-plane V-shaped micro-beam. The micro-beam is fabricated from highly doped silicon and is sandwiched between four electrodes to electrostatically activate both modes of vibrations. When tuning the electrothermal voltage, the natural frequencies of the two modes approach each other until they cross. Under electrostatic actuation, it is shown experimentally that the system undergoes a transition between modes crossing to veering. In addition, an analytical study is presented based on a Galerkin-based reduced-order model of a nonlinear Euler–Bernoulli shallow arch beam equation. The analytical results are compared to experimental data showing excellent agreement.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91253421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The influence of spanwise vibrations coupled with various levels of heating, on the lift and drag coefficients, is numerically studied in this work. The flow domain consists of a circular region of 64D surrounding the circular cylinder of diameter D. Transient analysis is conducted to solve URANS using Ansys/Fluent for laminar flow at Reynolds number of 100. Spanwise forced oscillations are carried out using user-defined-functions to mimic the flow induced vibrations. Amplitude of oscillation is kept fixed at 0.1D and frequency of oscillation is varied according to the frequency ratios (f/fn) of 0, 0.5, 1, 1.5, and 2, where 0 means the cylinder is stationary. Four levels of heating is applied, ΔT = 0 for isothermal, and ΔT = 300, 600, 900 K for non-isothermal flow, where ΔT is the temperature difference between the cylinder wall and the oncoming fluid. Air is taken as the fluid and temperature dependent properties of air are considered as the properties change significantly in the given temperature range. Mesh sensitivity is done initially to gain good fidelity of the discretized flow domain and the model is validated using the experimental results from the literature. The non-dimensional natural vortex shedding frequency of the stationary cylinder for isothermal flow is found to be 0.165 marking its Strouhal number. It is observed that heating the cylinder decreases the natural vortex shedding frequency. Increasing ΔT to 300 and 600 K decreased the natural vortex shedding frequency by 14.29% and 28.03%, respectively. It is observed that vortex shedding stops at ΔT of 900 K for stationary cylinder and for forced oscillating cylinder only one peak is seen in Fast Fourier Transform (FFT) corresponding to the forcing frequency. It is observed that the rms of the lift coefficient increases with an increase in the frequency ratio at all values of temperatures. FFT of the lift coefficient revealed only one frequency for frequency ratio of 0 and 1 at the natural frequency of the cylinder whereas for other values of frequency ratio, two peaks are observed, one for the natural frequency and the other for the forcing frequency. Lock-in phenomena is observed at the frequency ratio of 1 for isothermal cylinder where a large increase in the average drag coefficient occurred. For all values of frequency ratio, an increase in the temperature difference results in decrease in the lift and increase in the drag coefficient. Increasing ΔT to 300, 600, and 900 K, increases drag by 7.33%, 11.65%, and 16.52%, respectively, for stationary cylinder and a similar trend in observed for the oscillating cylinder. These results show that heating the cylinder decreases the lift coefficient and the natural vortex shedding frequency of the cylinder, whereas it increases the drag coefficient.
{"title":"Heated Circular Cylinder Subjected to Forced Spanwise Oscillations","authors":"Ussama Ali, Md. Islam, I. Janajreh","doi":"10.1115/imece2021-70713","DOIUrl":"https://doi.org/10.1115/imece2021-70713","url":null,"abstract":"\u0000 The influence of spanwise vibrations coupled with various levels of heating, on the lift and drag coefficients, is numerically studied in this work. The flow domain consists of a circular region of 64D surrounding the circular cylinder of diameter D. Transient analysis is conducted to solve URANS using Ansys/Fluent for laminar flow at Reynolds number of 100. Spanwise forced oscillations are carried out using user-defined-functions to mimic the flow induced vibrations. Amplitude of oscillation is kept fixed at 0.1D and frequency of oscillation is varied according to the frequency ratios (f/fn) of 0, 0.5, 1, 1.5, and 2, where 0 means the cylinder is stationary. Four levels of heating is applied, ΔT = 0 for isothermal, and ΔT = 300, 600, 900 K for non-isothermal flow, where ΔT is the temperature difference between the cylinder wall and the oncoming fluid. Air is taken as the fluid and temperature dependent properties of air are considered as the properties change significantly in the given temperature range. Mesh sensitivity is done initially to gain good fidelity of the discretized flow domain and the model is validated using the experimental results from the literature. The non-dimensional natural vortex shedding frequency of the stationary cylinder for isothermal flow is found to be 0.165 marking its Strouhal number. It is observed that heating the cylinder decreases the natural vortex shedding frequency. Increasing ΔT to 300 and 600 K decreased the natural vortex shedding frequency by 14.29% and 28.03%, respectively. It is observed that vortex shedding stops at ΔT of 900 K for stationary cylinder and for forced oscillating cylinder only one peak is seen in Fast Fourier Transform (FFT) corresponding to the forcing frequency. It is observed that the rms of the lift coefficient increases with an increase in the frequency ratio at all values of temperatures. FFT of the lift coefficient revealed only one frequency for frequency ratio of 0 and 1 at the natural frequency of the cylinder whereas for other values of frequency ratio, two peaks are observed, one for the natural frequency and the other for the forcing frequency. Lock-in phenomena is observed at the frequency ratio of 1 for isothermal cylinder where a large increase in the average drag coefficient occurred. For all values of frequency ratio, an increase in the temperature difference results in decrease in the lift and increase in the drag coefficient. Increasing ΔT to 300, 600, and 900 K, increases drag by 7.33%, 11.65%, and 16.52%, respectively, for stationary cylinder and a similar trend in observed for the oscillating cylinder. These results show that heating the cylinder decreases the lift coefficient and the natural vortex shedding frequency of the cylinder, whereas it increases the drag coefficient.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89502891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ankit Saxena, G. Rai, Valentin Lanari, C. Rahn, G. Manogharan
Fluidlastic dampers, isolators and absorbers are stand alone components used to reduce vibrations in many civil, mechanical and aerospace structures. This research demonstrates how additive manufacturing can integrate fluidlastic circuits inside a metal part. An example device with relatively simple monolithic construction consists of two chambers separated by a thin membrane that is connected to the upper chamber by a bridge compliant mechanism. The chambers are filled with fluid and are connected by a long thin channel inertia track that coils around their periphery. Elastic strain deflects the bridge causing the membrane to bulge into the upper chamber. This causes a pressure gradient that drives the fluid flow from the upper chamber to the lower chamber through the inertia track. Enabled by additive manufacturing, design parameters such as chamber dimensions, constitutive material, fluid viscosity, etc. can be easily tailored to provide targeted resonance over a desired frequency range. Experimental results provide evidence of fluid pumping at the membrane’s first resonant frequency.
{"title":"Strain-Coupled Fluidlastic Circuits Inside Metal Additive Manufactured Structures","authors":"Ankit Saxena, G. Rai, Valentin Lanari, C. Rahn, G. Manogharan","doi":"10.1115/imece2021-69721","DOIUrl":"https://doi.org/10.1115/imece2021-69721","url":null,"abstract":"\u0000 Fluidlastic dampers, isolators and absorbers are stand alone components used to reduce vibrations in many civil, mechanical and aerospace structures. This research demonstrates how additive manufacturing can integrate fluidlastic circuits inside a metal part. An example device with relatively simple monolithic construction consists of two chambers separated by a thin membrane that is connected to the upper chamber by a bridge compliant mechanism. The chambers are filled with fluid and are connected by a long thin channel inertia track that coils around their periphery. Elastic strain deflects the bridge causing the membrane to bulge into the upper chamber. This causes a pressure gradient that drives the fluid flow from the upper chamber to the lower chamber through the inertia track. Enabled by additive manufacturing, design parameters such as chamber dimensions, constitutive material, fluid viscosity, etc. can be easily tailored to provide targeted resonance over a desired frequency range. Experimental results provide evidence of fluid pumping at the membrane’s first resonant frequency.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88467071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The fluid-structure interaction mechanism of flow past multiple structures in proximity is complex. Depending on the initial spacing between a pair of circular cylinders and the reduced flow velocity parameter, the downstream cylinder may undergo wake-induced vibration (WIV) and/or vortex-induced vibration (VIV). This study presents an advanced numerical time-domain simulation model to predict a two-degree-of-freedom WIV, combined with VIV response, of an elastically mounted rigid circular cylinder behind a stationary cylinder in staggered arrangements. The wake deficit flow is modelled based on the boundary layer theory, whereas the unsteady drag and lift hydrodynamic forces due to the vortex shedding of the downstream cylinder are modelled by using the nonlinear van der Pol wake oscillators. The proposed numerical prediction model is calibrated and compared versus experimental data in the literature. For the initial longitudinal centre-to-centre spacing of 4 diameters and the initial transverse spacing of less than 2 diameters, the downstream cylinder first behaves as an isolated cylinder undergoing VIV at a low deficit flow velocity. With increasing flow velocity and Reynolds number, the downstream cylinder exhibits WIV response with progressively increasing oscillation amplitudes in both cross-flow and in-line directions. For staggered cylinders, the time-varying feature of the mean lift force, directed towards the wake centreline and acting on the downstream cylinder, becomes locally asymmetric through the course of the cylinder motion trajectories. This feature modifies WIV response frequencies and leads to an asymmetric trajectory of the cylinder’s two-directional displacements.
{"title":"Nonlinear Wake-Induced Vibration of Downstream Cylinder in Staggered Arrangements","authors":"Bruno Soares, N. Srinil","doi":"10.1115/imece2021-67776","DOIUrl":"https://doi.org/10.1115/imece2021-67776","url":null,"abstract":"\u0000 The fluid-structure interaction mechanism of flow past multiple structures in proximity is complex. Depending on the initial spacing between a pair of circular cylinders and the reduced flow velocity parameter, the downstream cylinder may undergo wake-induced vibration (WIV) and/or vortex-induced vibration (VIV). This study presents an advanced numerical time-domain simulation model to predict a two-degree-of-freedom WIV, combined with VIV response, of an elastically mounted rigid circular cylinder behind a stationary cylinder in staggered arrangements. The wake deficit flow is modelled based on the boundary layer theory, whereas the unsteady drag and lift hydrodynamic forces due to the vortex shedding of the downstream cylinder are modelled by using the nonlinear van der Pol wake oscillators. The proposed numerical prediction model is calibrated and compared versus experimental data in the literature. For the initial longitudinal centre-to-centre spacing of 4 diameters and the initial transverse spacing of less than 2 diameters, the downstream cylinder first behaves as an isolated cylinder undergoing VIV at a low deficit flow velocity. With increasing flow velocity and Reynolds number, the downstream cylinder exhibits WIV response with progressively increasing oscillation amplitudes in both cross-flow and in-line directions. For staggered cylinders, the time-varying feature of the mean lift force, directed towards the wake centreline and acting on the downstream cylinder, becomes locally asymmetric through the course of the cylinder motion trajectories. This feature modifies WIV response frequencies and leads to an asymmetric trajectory of the cylinder’s two-directional displacements.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76210144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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