The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Harry H. Asada - One of the best experts on this subject based on the ideXlab platform.
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pulse width modulation of water jet propulsion systems using high speed Coanda Effect valves
Journal of Dynamic Systems Measurement and Control-transactions of The Asme, 2013Co-Authors: Anirban Mazumdar, Harry H. AsadaAbstract:An integrated high-speed valve switching and pump output control scheme are developed for precision maneuvering of underwater vehicles. High-speed Coanda-Effect valves combined with a centrifugal pump allow for precise control of thrust force using a unique pulse width modulation (PWM) control scheme, where both pulse width and pulse height are controlled in a coordinated manner. Dead zones and other complex nonlinear dynamics of traditional propeller thrusters and water jet pumps are avoided with use of the integrated pump-valve control. Three control algorithms for coordinating valve switching and pump output are presented. A simplified nonlinear hydrodynamic model of underwater vehicles is constructed, and design trade-offs between PWM frequency and pulse height, with regard to steady state oscillations, are addressed. The control algorithms are implemented on a prototype underwater vehicle and the theoretical results are verified through experiments.
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A compact underwater vehicle using high-bandwidth Coanda-Effect valves for low speed precision maneuvering in cluttered environments
2011 IEEE International Conference on Robotics and Automation, 2011Co-Authors: Anirban Mazumdar, Harry H. AsadaAbstract:A highly maneuver able, compact vehicle for underwater precision inspection of complex structures is presented. The vehicle will have no appendages such as rudders, screws, and other external thrusters, which might get tangled and interfere with the underwater structure in a cluttered environment. A multi-axis, integrated thruster mechanism using Coanda-Effect high-speed valves for switching the direction of jets can be encapsulated in a compact, egg-shaped body. Compared to traditional screw thrusters, these valves have improved dynamic performance in switching the jet stream direction. Furthermore, the reaction forces and moments due to switching can be substantially reduced. First, the principle of Coanda Effect water jet valves is introduced, and its governing equations are obtained. Optimal dimensions and parameters producing a maximum of thrust are obtained, and are experimentally verified. Multiple Coanda-Effect valves are then integrated into a tree structure to create a multi-axis thrust mechanism. A simple planar proof of concept prototype is built and tested.
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ICRA - A compact underwater vehicle using high-bandwidth Coanda-Effect valves for low speed precision maneuvering in cluttered environments
2011 IEEE International Conference on Robotics and Automation, 2011Co-Authors: Anirban Mazumdar, Harry H. AsadaAbstract:A highly maneuverable, compact vehicle for underwater precision inspection of complex structures is presented. The vehicle will have no appendages such as rudders, screws, and other external thrusters, which might get tangled and interfere with the underwater structure in a cluttered environment. A multi-axis, integrated thruster mechanism using Coanda-Effect high-speed valves for switching the direction of jets can be encapsulated in a compact, egg-shaped body. Compared to traditional screw thrusters, these valves have improved dynamic performance in switching the jet stream direction. Furthermore, the reaction forces and moments due to switching can be substantially reduced. First, the principle of CoandaEffect water jet valves is introduced, and its governing equations are obtained. Optimal dimensions and parameters producing a maximum of thrust are obtained, and are experimentally verified. Multiple Coanda-Effect valves are then integrated into a tree structure to create a multi-axis thrust mechanism. A simple planar proof of concept prototype is built and tested.
Song Yang - One of the best experts on this subject based on the ideXlab platform.
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a novel valveless piezoelectric micropump with a bluff body based on Coanda Effect
Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems, 2019Co-Authors: Xiuhua He, Rongqun Bian, Wei Xu, Zhidan Deng, Song YangAbstract:Based on the Coanda Effect, a novel valveless micropump is presented in this paper, the special bluff-body is utilized to enhance the Coanda Effect and increase the net flow of the micropump. In order to reveal the influence of structural parameters on the performance of novel micropump, five micropump samples with different chamber radii (5 mm and 9 mm), aspect ratios (4 and 8) and channel angles (30° and 45°) are fabricated by silicon-based MEMS technology. On the conditions of the voltages (50–300 vpp) and excitation frequencies (25–125 Hz), the performance of the micropumps is studied experimentally in detail. As the voltage V = 300 vpp and the frequency f = 50 Hz, the maximum net flow and back pressure for the optimal sample can attain 4.84 ml/min and 1.75 kPa, respectively. Through numerical simulations, the efficiency of the micropumps with different aspect ratios L1/d (3–9) are investigated as Reynolds number range from 300 to 1000 at the frequencies of 5–400 Hz. When the Reynolds number is constant, the pump efficiency has the optimal value with the increase of frequency, and the streamline diagrams indicate that this is related to the Effects of the internal vortexes.
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Experiment and numerical simulation of a valveless piezoelectric micropump applying Coanda Effect
Mechanics & Industry, 2016Co-Authors: Xiuhua He, Xitong Zhang, Song YangAbstract:To improve the flowrate and the volumetric efficiency of the valveless piezoelectric micropump, a valveless piezoelectric micropump based on Coanda Effect was designed and fabricated by Polymethylmethacrylate (PMMA). Its performance including the flowrate and the maximum back pressure, optimum operating condition, working principle as well as the diffuser angle were discussed. An experiment was carried out to obtain the performance of the micropump and search for the optimum operating condition. The high-speed photograph was utilized to obtain the instantaneous volume changing rate of the chamber in the experiment. A numerical simulation was done to obtain the flow field of the micropump to specialize its working principle. To discuss the Effects of the diffuser angle on the performance, the flowrate and the volumetric efficiency of the micropumps with different diffuser angles from 30° to 45° were studied by the numerical simulation. The numerical simulation results were compared with the experimental data. The findings reveal that the micropump with the diffuser angle of 45° can achieve the flowrate of 5.4 ml.min-1 and the maximum back pressure of 2.82 kPa in the optimum operating condition, 300 Vp-p for the driving voltage and 25 Hz for the frequency. The suitable range of the diffuser angle is about from 30° to 45°. When the maximum Reynolds number is over 600, the entrained flowrate caused by Coanda Effect can contribute a over 50% volumetric efficiency to the micropump.
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a bidirectional valveless piezoelectric micropump with double chambers based on Coanda Effect
Journal of The Brazilian Society of Mechanical Sciences and Engineering, 2016Co-Authors: Song Yang, Xiuhua He, Shouqi Yuan, Xitong ZhangAbstract:Micropumps are essential parts of many microfluidic devices. The valveless micropump has the advantage of simple structure and easy manufacture. A bidirectional valveless piezoelectric micropump with double chambers based on Coanda Effect has been presented in this paper. The micropump has better performance at low Reynolds number and can change the flow direction by regulating the voltage. The numerical simulations have been done for studying the performance of the micropumps. The results show the volume efficiency of the micropump can be over 50 %. The prototype micropump is fabricated by PMMA with precision machining and the experiment has been carried out to obtain the flow rate and back pressure. As only one piezoelectric actuator is excited and the voltage is set at 500 Vp–p, both the flow rate and back pressure reach the maximum which are 0.26 ml/min and 1.79 kPa, respectively, at the frequency of 10 Hz. As the other piezoelectric actuator is excited and the voltage reach 300 Vp–p, the flow rate and back pressure are 0.408 ml/min and 3.18 kPa, respectively, which are 57 and 78 % larger, respectively, than those at zero voltage.
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design of a novel bidirectional valveless piezoelectric micropump with three chambers using Coanda Effect based on numerical simulation
Volume 1B Symposia: Fluid Machinery; Fluid-Structure Interaction and Flow-Induced Noise in Industrial Applications; Flow Applications in Aerospace; Fl, 2014Co-Authors: Xiuhua He, Song Yang, Shouqi Yuan, Xitong ZhangAbstract:A novel bidirectional valveless piezoelectric micropump with three chambers using the Coanda Effect has been developed. The volume efficiency of the micropump is able to reach 50% which is much higher than that of the traditional diffuser/nozzle valveless micropump and its transport direction is easy to change. The chambers are covered by three piezoelectric actuators, respectively. There are three channels connected with each chamber, respectively. And the other ends of the channels join together and connect with a diffuser. One of the channels has the same centerline with the diffuser. The centerline is perpendicular to the other two channels which situate on the two sides of the diffuser symmetrically. Inlet and outlet channels are connected with the other end of the diffuser. Three piezoelectric actuators are driven by the synchronous voltages with different magnitude. When the fluid is discharged from the pump chambers, the flowrate of one channel situated on the side of the diffuser is smaller than that of the two others. Due to the Coanda Effect, the jet flow in the diffuser attaches the wall and all fluid enters the outlet channel. And some fluid is sucked from inlet channel because of the vortex induced by the jet flow. When the fluid is sucked into the pump chambers, the flowrate of fluid sucked into the inlet and outlet channels are same. So the fluid transports from the inlet channel to outlet channel in a cycle. And the micropump could change the transport direction by changing the flowrate of the two channels situated on the two sides of the diffuser. CFX is applied to simulate the flow field of the micropump and the dynamic mesh method is used for the simulation of the piezoelectric actuator. The sinusoidal vibration is applied to the piezoelectric actuator and the frequency is 10Hz. The narrowest width and height of the diffuser is 200μm. The Reynolds number is between 1000 and 1800 in the simulation and the SST model is chosen. Hexahedral mesh is used and the number of elements is about 1.2 million. The result shows that when the amplitude of two actuators is same and the amplitude of the third one is 20% of the former (the maximum Reynolds number of the diffuser is about 1200), the maximum flowrate of the micropump is 2.43 ml/min and the volume efficiency reaches 58%.Copyright © 2014 by ASME
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Flow characteristic of a valveless piezoelectric micropump applying Coanda Effect
2014 ISFMFE - 6th International Symposium on Fluid Machinery and Fluid Engineering, 2014Co-Authors: Xiuhua He, Xitong Zhang, Song YangAbstract:A valveless piezoelectric micropump based on Coanda Effect was presented. The Effects of the angle and the length of the diffuser as well as the Reynolds number on the performance of the micropump were studied. The numerical simulation was done to obtain the flow field as well as the flow rate and the volumetric efficiency of the micropump. The range of the diffuser angle was from 15°to 60°, and Reynolds numbers was from 200 to 800. It shows that as the diffuser angle increased, the maximum flow rate rose from 15° to 45°, and then dropped sharply after 45°. When the Reynolds number was low, the fluid was discharged through both the inlet and outlet pipes in the pumping process. With the increasing of the Reynolds numbers, more fluid was discharged through the outlet pipe than the other one. When the Reynolds number was as high as 800, the fluid in the chamber was sprayed out only through the outlet pipe and also some fluid was entrained through the inlet pipe and sprayed out through the outlet. Thus, the volumetric efficiency of the micropump could reach over 50%. The maximum net flow rate 0.767 ml/min and volumetric efficiency 50.22% are obtained at the angle 45°, length of the diffuser 362 μm and Re = 800.
Anirban Mazumdar - One of the best experts on this subject based on the ideXlab platform.
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pulse width modulation of water jet propulsion systems using high speed Coanda Effect valves
Journal of Dynamic Systems Measurement and Control-transactions of The Asme, 2013Co-Authors: Anirban Mazumdar, Harry H. AsadaAbstract:An integrated high-speed valve switching and pump output control scheme are developed for precision maneuvering of underwater vehicles. High-speed Coanda-Effect valves combined with a centrifugal pump allow for precise control of thrust force using a unique pulse width modulation (PWM) control scheme, where both pulse width and pulse height are controlled in a coordinated manner. Dead zones and other complex nonlinear dynamics of traditional propeller thrusters and water jet pumps are avoided with use of the integrated pump-valve control. Three control algorithms for coordinating valve switching and pump output are presented. A simplified nonlinear hydrodynamic model of underwater vehicles is constructed, and design trade-offs between PWM frequency and pulse height, with regard to steady state oscillations, are addressed. The control algorithms are implemented on a prototype underwater vehicle and the theoretical results are verified through experiments.
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A compact underwater vehicle using high-bandwidth Coanda-Effect valves for low speed precision maneuvering in cluttered environments
2011 IEEE International Conference on Robotics and Automation, 2011Co-Authors: Anirban Mazumdar, Harry H. AsadaAbstract:A highly maneuver able, compact vehicle for underwater precision inspection of complex structures is presented. The vehicle will have no appendages such as rudders, screws, and other external thrusters, which might get tangled and interfere with the underwater structure in a cluttered environment. A multi-axis, integrated thruster mechanism using Coanda-Effect high-speed valves for switching the direction of jets can be encapsulated in a compact, egg-shaped body. Compared to traditional screw thrusters, these valves have improved dynamic performance in switching the jet stream direction. Furthermore, the reaction forces and moments due to switching can be substantially reduced. First, the principle of Coanda Effect water jet valves is introduced, and its governing equations are obtained. Optimal dimensions and parameters producing a maximum of thrust are obtained, and are experimentally verified. Multiple Coanda-Effect valves are then integrated into a tree structure to create a multi-axis thrust mechanism. A simple planar proof of concept prototype is built and tested.
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ICRA - A compact underwater vehicle using high-bandwidth Coanda-Effect valves for low speed precision maneuvering in cluttered environments
2011 IEEE International Conference on Robotics and Automation, 2011Co-Authors: Anirban Mazumdar, Harry H. AsadaAbstract:A highly maneuverable, compact vehicle for underwater precision inspection of complex structures is presented. The vehicle will have no appendages such as rudders, screws, and other external thrusters, which might get tangled and interfere with the underwater structure in a cluttered environment. A multi-axis, integrated thruster mechanism using Coanda-Effect high-speed valves for switching the direction of jets can be encapsulated in a compact, egg-shaped body. Compared to traditional screw thrusters, these valves have improved dynamic performance in switching the jet stream direction. Furthermore, the reaction forces and moments due to switching can be substantially reduced. First, the principle of CoandaEffect water jet valves is introduced, and its governing equations are obtained. Optimal dimensions and parameters producing a maximum of thrust are obtained, and are experimentally verified. Multiple Coanda-Effect valves are then integrated into a tree structure to create a multi-axis thrust mechanism. A simple planar proof of concept prototype is built and tested.
Jose Pascoa Marques - One of the best experts on this subject based on the ideXlab platform.
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the influence of surface temperature on Coanda Effect
Energy Procedia, 2014Co-Authors: Antonio Dumas, Michele Trancossi, Maharshi Subhash, Jose Pascoa MarquesAbstract:Abstract Coanda Effect is the adhesion of fluid on a convex surface. This paper presents the Effect of temperature on the Coanda flow and shows how the temperature of the surface can influence the flow behaviour. It has been found that there are two mechanisms which influence the flow behaviour; both have contrary Effect on the flow. One is based on variable Prandtl number and another is based on constant Prandtl number (thermal diffusivity) Effect. The increment of the thermal diffusivity has prolonged separation of the boundary layer, while other mechanism triggers the earlier detachment of the flow from the curved surface. The preliminary CFD evaluation has provided the important controlling parameter for the thrust deflection.
Xiuhua He - One of the best experts on this subject based on the ideXlab platform.
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a novel valveless piezoelectric micropump with a bluff body based on Coanda Effect
Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems, 2019Co-Authors: Xiuhua He, Rongqun Bian, Wei Xu, Zhidan Deng, Song YangAbstract:Based on the Coanda Effect, a novel valveless micropump is presented in this paper, the special bluff-body is utilized to enhance the Coanda Effect and increase the net flow of the micropump. In order to reveal the influence of structural parameters on the performance of novel micropump, five micropump samples with different chamber radii (5 mm and 9 mm), aspect ratios (4 and 8) and channel angles (30° and 45°) are fabricated by silicon-based MEMS technology. On the conditions of the voltages (50–300 vpp) and excitation frequencies (25–125 Hz), the performance of the micropumps is studied experimentally in detail. As the voltage V = 300 vpp and the frequency f = 50 Hz, the maximum net flow and back pressure for the optimal sample can attain 4.84 ml/min and 1.75 kPa, respectively. Through numerical simulations, the efficiency of the micropumps with different aspect ratios L1/d (3–9) are investigated as Reynolds number range from 300 to 1000 at the frequencies of 5–400 Hz. When the Reynolds number is constant, the pump efficiency has the optimal value with the increase of frequency, and the streamline diagrams indicate that this is related to the Effects of the internal vortexes.
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Experiment and numerical simulation of a valveless piezoelectric micropump applying Coanda Effect
Mechanics & Industry, 2016Co-Authors: Xiuhua He, Xitong Zhang, Song YangAbstract:To improve the flowrate and the volumetric efficiency of the valveless piezoelectric micropump, a valveless piezoelectric micropump based on Coanda Effect was designed and fabricated by Polymethylmethacrylate (PMMA). Its performance including the flowrate and the maximum back pressure, optimum operating condition, working principle as well as the diffuser angle were discussed. An experiment was carried out to obtain the performance of the micropump and search for the optimum operating condition. The high-speed photograph was utilized to obtain the instantaneous volume changing rate of the chamber in the experiment. A numerical simulation was done to obtain the flow field of the micropump to specialize its working principle. To discuss the Effects of the diffuser angle on the performance, the flowrate and the volumetric efficiency of the micropumps with different diffuser angles from 30° to 45° were studied by the numerical simulation. The numerical simulation results were compared with the experimental data. The findings reveal that the micropump with the diffuser angle of 45° can achieve the flowrate of 5.4 ml.min-1 and the maximum back pressure of 2.82 kPa in the optimum operating condition, 300 Vp-p for the driving voltage and 25 Hz for the frequency. The suitable range of the diffuser angle is about from 30° to 45°. When the maximum Reynolds number is over 600, the entrained flowrate caused by Coanda Effect can contribute a over 50% volumetric efficiency to the micropump.
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a bidirectional valveless piezoelectric micropump with double chambers based on Coanda Effect
Journal of The Brazilian Society of Mechanical Sciences and Engineering, 2016Co-Authors: Song Yang, Xiuhua He, Shouqi Yuan, Xitong ZhangAbstract:Micropumps are essential parts of many microfluidic devices. The valveless micropump has the advantage of simple structure and easy manufacture. A bidirectional valveless piezoelectric micropump with double chambers based on Coanda Effect has been presented in this paper. The micropump has better performance at low Reynolds number and can change the flow direction by regulating the voltage. The numerical simulations have been done for studying the performance of the micropumps. The results show the volume efficiency of the micropump can be over 50 %. The prototype micropump is fabricated by PMMA with precision machining and the experiment has been carried out to obtain the flow rate and back pressure. As only one piezoelectric actuator is excited and the voltage is set at 500 Vp–p, both the flow rate and back pressure reach the maximum which are 0.26 ml/min and 1.79 kPa, respectively, at the frequency of 10 Hz. As the other piezoelectric actuator is excited and the voltage reach 300 Vp–p, the flow rate and back pressure are 0.408 ml/min and 3.18 kPa, respectively, which are 57 and 78 % larger, respectively, than those at zero voltage.
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design of a novel bidirectional valveless piezoelectric micropump with three chambers using Coanda Effect based on numerical simulation
Volume 1B Symposia: Fluid Machinery; Fluid-Structure Interaction and Flow-Induced Noise in Industrial Applications; Flow Applications in Aerospace; Fl, 2014Co-Authors: Xiuhua He, Song Yang, Shouqi Yuan, Xitong ZhangAbstract:A novel bidirectional valveless piezoelectric micropump with three chambers using the Coanda Effect has been developed. The volume efficiency of the micropump is able to reach 50% which is much higher than that of the traditional diffuser/nozzle valveless micropump and its transport direction is easy to change. The chambers are covered by three piezoelectric actuators, respectively. There are three channels connected with each chamber, respectively. And the other ends of the channels join together and connect with a diffuser. One of the channels has the same centerline with the diffuser. The centerline is perpendicular to the other two channels which situate on the two sides of the diffuser symmetrically. Inlet and outlet channels are connected with the other end of the diffuser. Three piezoelectric actuators are driven by the synchronous voltages with different magnitude. When the fluid is discharged from the pump chambers, the flowrate of one channel situated on the side of the diffuser is smaller than that of the two others. Due to the Coanda Effect, the jet flow in the diffuser attaches the wall and all fluid enters the outlet channel. And some fluid is sucked from inlet channel because of the vortex induced by the jet flow. When the fluid is sucked into the pump chambers, the flowrate of fluid sucked into the inlet and outlet channels are same. So the fluid transports from the inlet channel to outlet channel in a cycle. And the micropump could change the transport direction by changing the flowrate of the two channels situated on the two sides of the diffuser. CFX is applied to simulate the flow field of the micropump and the dynamic mesh method is used for the simulation of the piezoelectric actuator. The sinusoidal vibration is applied to the piezoelectric actuator and the frequency is 10Hz. The narrowest width and height of the diffuser is 200μm. The Reynolds number is between 1000 and 1800 in the simulation and the SST model is chosen. Hexahedral mesh is used and the number of elements is about 1.2 million. The result shows that when the amplitude of two actuators is same and the amplitude of the third one is 20% of the former (the maximum Reynolds number of the diffuser is about 1200), the maximum flowrate of the micropump is 2.43 ml/min and the volume efficiency reaches 58%.Copyright © 2014 by ASME
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Flow characteristic of a valveless piezoelectric micropump applying Coanda Effect
2014 ISFMFE - 6th International Symposium on Fluid Machinery and Fluid Engineering, 2014Co-Authors: Xiuhua He, Xitong Zhang, Song YangAbstract:A valveless piezoelectric micropump based on Coanda Effect was presented. The Effects of the angle and the length of the diffuser as well as the Reynolds number on the performance of the micropump were studied. The numerical simulation was done to obtain the flow field as well as the flow rate and the volumetric efficiency of the micropump. The range of the diffuser angle was from 15°to 60°, and Reynolds numbers was from 200 to 800. It shows that as the diffuser angle increased, the maximum flow rate rose from 15° to 45°, and then dropped sharply after 45°. When the Reynolds number was low, the fluid was discharged through both the inlet and outlet pipes in the pumping process. With the increasing of the Reynolds numbers, more fluid was discharged through the outlet pipe than the other one. When the Reynolds number was as high as 800, the fluid in the chamber was sprayed out only through the outlet pipe and also some fluid was entrained through the inlet pipe and sprayed out through the outlet. Thus, the volumetric efficiency of the micropump could reach over 50%. The maximum net flow rate 0.767 ml/min and volumetric efficiency 50.22% are obtained at the angle 45°, length of the diffuser 362 μm and Re = 800.