The Experts below are selected from a list of 86163 Experts worldwide ranked by ideXlab platform
Xiaolong Ge - One of the best experts on this subject based on the ideXlab platform.
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three dimensional numerical simulation of gas liquid interfacial mass transfer with rayleigh convection using hybrid lbm fdm and its mass transfer coefficient Model
Chemical Engineering Science, 2019Co-Authors: Xiaolong Ge, Hongxing Wang, Xigang YuanAbstract:Abstract Rayleigh convection has a significant effect on gas-liquid interfacial mass transfer. However, its intensified mechanism has not been clarified so far. In the present work, three-dimensional hybrid Lattice Boltzmann Method-Finite Difference Method (LBM-FDM) was employed to simulate the Rayleigh convection emerging in the CO2-ethanol absorption process. A gas phase random Disturbance Model was applied to represent the Disturbances on the gas-liquid interface which effectively induces Rayleigh convection. Then the front view images obtained by three-dimensional simulation were compared to the Schlieren observations for validation. Finally, a theoretical mass transfer coefficient Model based on dissipation rate of concentration variance was proposed, by analyzing the overhead view of concentration contour and dissipation rate of concentration variance contour. Compared to the small eddy Model and surface divergence Model, the proposed Model shows its strength in determining molecular diffusion stage and convective mass transfer stage of Rayleigh convection process, as well as eliminating the phase difference in Model prediction.
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numerical simulation of evaporation with rayleigh convection using lbm fdm hybrid method and proposal of the interfacial mass transfer coefficient Model
International Journal of Heat and Mass Transfer, 2019Co-Authors: Xiaolong Ge, Xigang Yuan, Hongxing WangAbstract:Abstract The Rayleigh convection could be induced by solute evaporation in dual solvents, such as acetone-ethyl acetate and isopropanol-water system. The onset of Rayleigh convection and its evolutionary characteristics were simulated using LBM-FDM hybrid method with liquid phase random Disturbance Model. And the simulation results were in reasonable agreement with experimental measurements in four aspects: Rayleigh convection onset time, concentration field acquired by Schlieren and velocity field acquired by PIV, average mass transfer coefficient, and statistical average velocity distribution along the gravitational direction. It proves that the LBM-FDM hybrid method is effective in capturing the key features in this mesoscale phenomenon. Then three mass transfer Model including small eddy Model, surface divergence Model and the new Model based on theoretical parameters concentration variance, its dissipation rate and Reynolds mass flux were proposed to predict the interfacial mass transfer coefficient, and the new developed Model had advantages over other two Models, in the onset time of Rayleigh convection, the peak of mass transfer coefficient and tackling the non-synchronism between velocity and concentration field in fully developed convective stage. The new developed Model shows its strength in determining the mass transfer coefficient in a theoretical way.
Frank E Pfefferkorn - One of the best experts on this subject based on the ideXlab platform.
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physics based interpretation of tool workpiece interface temperature signals for detection of defect formation during friction stir welding
Manufacturing letters, 2015Co-Authors: Amber Shrivastava, Michael R Zinn, Clemens Dingler, Frank E PfefferkornAbstract:Abstract The objective of the work is the reduction and eventual avoidance of post welding inspections that are currently needed to ensure defect-free welds. An analytical thermal Model of the FSW process along with an analytical Disturbance Model is developed. This Disturbance Model relates defect formation to variations in the measured temperature and is based on experimental process identification. A dynamic Disturbance observer computes an estimate of the Disturbance signal, which is further processed in order to provide information about the presence of defects along the weld. Experiments for one kind of Disturbance verify that the observer shows good tracking behavior.
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physics based interpretation of tool workpiece interface temperature signals for detection of defect formation during friction stir welding
Manufacturing letters, 2015Co-Authors: Amber Shrivastava, Michael R Zinn, Clemens Dingler, Frank E PfefferkornAbstract:Abstract The objective of the work is the reduction and eventual avoidance of post welding inspections that are currently needed to ensure defect-free welds. An analytical thermal Model of the FSW process along with an analytical Disturbance Model is developed. This Disturbance Model relates defect formation to variations in the measured temperature and is based on experimental process identification. A dynamic Disturbance observer computes an estimate of the Disturbance signal, which is further processed in order to provide information about the presence of defects along the weld. Experiments for one kind of Disturbance verify that the observer shows good tracking behavior.
Christian Bohn - One of the best experts on this subject based on the ideXlab platform.
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lpv control of speed fluctuations in rotating machines with nonlinear dynamics
Mediterranean Conference on Control and Automation, 2017Co-Authors: Peter Kotzyba, Christian BohnAbstract:This paper presents a method for controlling torsional vibrations in rotating machines with nonlinear dynamics. The work is motivated by rotating machines with cam or crankshaft mechanisms that generate harmonic signal components in the angular speed with respect to the rotation angle. In the system description, the torsional vibrations are Modeled as Disturbances acting upon a linear plant. Thus, the system can be decomposed into a plant Model and a Disturbance Model. Both Models are then described as polytopic linear parameter-varying (pLPV) systems. A Disturbance observer-based controller is used to counteract the time varying fluctuations in the angle speed. The method is tested in a simulation study with a Model of a camshaft drive. The simulation results demonstrate the efficiency of the control approach.
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varying sampling time lpv control for rejecting harmonically related nonstationary multisine Disturbances
Advances in Computing and Communications, 2015Co-Authors: Xin Yu Shu, Pablo Ballesteros, Christian BohnAbstract:In this paper, a novel approach to design linear parameter-varying (LPV) controllers with time-varying sampling time to reject nonstationary harmonically related multisine Disturbances is presented. The sampling time is chosen as a fraction of the smallest period of the harmonically related Disturbance component. The plant is discretized with this sampling time using zero-order hold (ZOH). As a result, the Disturbance Model is regarded as one with fixed state-space representation subject to a time-varying sampling time. A polytopic LPV (pLPV) controller which quadratically stabilizes the plant under the Disturbance is obtained. The number of the scheduling parameters is determined by the precision of the Taylor approximation for the discretized plant, independently of the number of frequencies. Excellent Disturbance rejection is achieved in simulation.
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an lpv discrete time controller for the rejection of harmonic time varying Disturbances in a lightweight flexible structure
American Control Conference, 2013Co-Authors: Franklyn Duarte, Pablo Ballesteros, Xin Yu Shu, Christian BohnAbstract:In this work, control system design and implementation for active vibration control (AVC) of flexible structures with piezoelectric actuators is studied. The goal is to reduce the effect of harmonic Disturbances with known time-varying frequencies acting on a system. As a test bed, a thin flexible aluminum cantilevered beam with two symmetrically bonded piezoelectric actuators is used. The harmonic excitation is generated by two DC motors each of them with an unbalanced mass. A discrete-time Model is obtained through black-box system identification methods. The control algorithm design is based on a plant description with a Disturbance Model as a linear parameter varying (LPV) system in linear fractional transformation (LFT) form. This results in a gain-scheduled controller where the harmonic Disturbance frequencies are the scheduling variables. The experimental real-time results show the effectiveness of the controller and its capability to suppress time-varying harmonic Disturbances, whose frequencies are measured directly from the DC motors. The design method leads to a controller that stabilizes the closed-loop system even for arbitrarily fast changes in the Disturbance frequencies. In the real-time experiment, the controller suppresses a Disturbance consisting of two independent harmonics with frequencies that vary over a range of 15 Hz.
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two parameter plpv Modeling of nonstationary harmonically related multisine Disturbances for reduced order gain scheduling control
Artificial Intelligence and Applications, 2013Co-Authors: Xin Yu Shu, Pablo Ballesteros, Wiebke Heins, Christian BohnAbstract:A two-parameter polytopic linear parameter-varying (pLPV) Modeling approach for nonstationary harmonically related multisine Disturbances is presented, and a pLPV controller based on this Model is introduced. An exact Model for Disturbances with known nonstationary frequencies is used. The number of the scheduling parameters is reduced to two using the Disturbance Model presented. The controller only consists of the Disturbance Model. Therefore, the controller order is the minimal order required for asymptotic Disturbance rejection. Experimental results validate the effectiveness of the controller using an active vibration control (AVC) test bed.
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identification and control of periodic Disturbances
Mediterranean Conference on Control and Automation, 2012Co-Authors: Izziddien Alsogkier, Christian BohnAbstract:A new Adaptive Feed-Forward strategy is presented, that identifies the periodic Disturbances of known frequencies. These Disturbance sources can be external or internal. Internal Disturbance are also called self-excited vibrations that come from the load or its parameter variations. These variations depend periodically on the angle of rotation particularly in the case of rotary machines. The identified parameters of the Disturbance Model are used to design feed forward controller to counteract the Disturbance effect on the system output, this is to be with a minimum interaction with an already existing, set point tracking feedback controller.
Xigang Yuan - One of the best experts on this subject based on the ideXlab platform.
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three dimensional numerical simulation of gas liquid interfacial mass transfer with rayleigh convection using hybrid lbm fdm and its mass transfer coefficient Model
Chemical Engineering Science, 2019Co-Authors: Xiaolong Ge, Hongxing Wang, Xigang YuanAbstract:Abstract Rayleigh convection has a significant effect on gas-liquid interfacial mass transfer. However, its intensified mechanism has not been clarified so far. In the present work, three-dimensional hybrid Lattice Boltzmann Method-Finite Difference Method (LBM-FDM) was employed to simulate the Rayleigh convection emerging in the CO2-ethanol absorption process. A gas phase random Disturbance Model was applied to represent the Disturbances on the gas-liquid interface which effectively induces Rayleigh convection. Then the front view images obtained by three-dimensional simulation were compared to the Schlieren observations for validation. Finally, a theoretical mass transfer coefficient Model based on dissipation rate of concentration variance was proposed, by analyzing the overhead view of concentration contour and dissipation rate of concentration variance contour. Compared to the small eddy Model and surface divergence Model, the proposed Model shows its strength in determining molecular diffusion stage and convective mass transfer stage of Rayleigh convection process, as well as eliminating the phase difference in Model prediction.
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numerical simulation of evaporation with rayleigh convection using lbm fdm hybrid method and proposal of the interfacial mass transfer coefficient Model
International Journal of Heat and Mass Transfer, 2019Co-Authors: Xiaolong Ge, Xigang Yuan, Hongxing WangAbstract:Abstract The Rayleigh convection could be induced by solute evaporation in dual solvents, such as acetone-ethyl acetate and isopropanol-water system. The onset of Rayleigh convection and its evolutionary characteristics were simulated using LBM-FDM hybrid method with liquid phase random Disturbance Model. And the simulation results were in reasonable agreement with experimental measurements in four aspects: Rayleigh convection onset time, concentration field acquired by Schlieren and velocity field acquired by PIV, average mass transfer coefficient, and statistical average velocity distribution along the gravitational direction. It proves that the LBM-FDM hybrid method is effective in capturing the key features in this mesoscale phenomenon. Then three mass transfer Model including small eddy Model, surface divergence Model and the new Model based on theoretical parameters concentration variance, its dissipation rate and Reynolds mass flux were proposed to predict the interfacial mass transfer coefficient, and the new developed Model had advantages over other two Models, in the onset time of Rayleigh convection, the peak of mass transfer coefficient and tackling the non-synchronism between velocity and concentration field in fully developed convective stage. The new developed Model shows its strength in determining the mass transfer coefficient in a theoretical way.
Amber Shrivastava - One of the best experts on this subject based on the ideXlab platform.
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physics based interpretation of tool workpiece interface temperature signals for detection of defect formation during friction stir welding
Manufacturing letters, 2015Co-Authors: Amber Shrivastava, Michael R Zinn, Clemens Dingler, Frank E PfefferkornAbstract:Abstract The objective of the work is the reduction and eventual avoidance of post welding inspections that are currently needed to ensure defect-free welds. An analytical thermal Model of the FSW process along with an analytical Disturbance Model is developed. This Disturbance Model relates defect formation to variations in the measured temperature and is based on experimental process identification. A dynamic Disturbance observer computes an estimate of the Disturbance signal, which is further processed in order to provide information about the presence of defects along the weld. Experiments for one kind of Disturbance verify that the observer shows good tracking behavior.
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physics based interpretation of tool workpiece interface temperature signals for detection of defect formation during friction stir welding
Manufacturing letters, 2015Co-Authors: Amber Shrivastava, Michael R Zinn, Clemens Dingler, Frank E PfefferkornAbstract:Abstract The objective of the work is the reduction and eventual avoidance of post welding inspections that are currently needed to ensure defect-free welds. An analytical thermal Model of the FSW process along with an analytical Disturbance Model is developed. This Disturbance Model relates defect formation to variations in the measured temperature and is based on experimental process identification. A dynamic Disturbance observer computes an estimate of the Disturbance signal, which is further processed in order to provide information about the presence of defects along the weld. Experiments for one kind of Disturbance verify that the observer shows good tracking behavior.