A quasi-3D model has been developed to simulate the flow in planar microfluidic systems with low ... more A quasi-3D model has been developed to simulate the flow in planar microfluidic systems with low Reynolds numbers. The model was developed by decomposing the flow profile along the height of a microfluidic system into a Fourier series. It was validated against the analytical solution for flow in a straight rectangular channel and the full 3D numerical COMSOL Navier-Stokes solver for flow in a T-channel. Comparable accuracy to the full 3D numerical solution was achieved by using only three Fourier terms with a significant decrease in computation time. The quasi-3D model was used to model flows in a micro-flow cytometer chip on a desktop computer and good agreement between the simulation and the experimental results was found.
A quasi-3D model has been developed to simulate the flow in planar microfluidic systems with low ... more A quasi-3D model has been developed to simulate the flow in planar microfluidic systems with low Reynolds numbers. The model was developed by decomposing the flow profile along the height of a microfluidic system into a Fourier series. It was validated against the analytical solution for flow in a straight rectangular channel and the full 3D numerical COMSOL Navier-Stokes solver for flow in a T-channel. Comparable accuracy to the full 3D numerical solution was achieved by using only three Fourier terms with a significant decrease in computation time. The quasi-3D model was used to model flows in a micro-flow cytometer chip on a desktop computer and good agreement between the simulation and the experimental results was found.
This paper describes the development of a prototype of a microcontroller-based phase angle contro... more This paper describes the development of a prototype of a microcontroller-based phase angle controlled single-phase AC voltage controller that can efficiently control AC voltage and also accommodates soft start capability for single-phase induction motors. The output voltage of the controller is regulated to maintain a desired fixed RMS value and provide stabilized output by implementing a feedback control system. One microcontroller generates PWM signals in synchronism with the supply voltage to control the firing angle of thyristors while a second microcontroller remains dedicated for measuring the RMS value of the output voltage and sending that to the main microcontroller for the purpose of feedback control. The provision for soft starting of a load is also incorporated into this prototype. Index Terms-AC voltage controller, Automatic voltage regulation, Soft start I. INTRODUCTION PWM-based AC voltage controllers are widely used in UPS and high power flexible AC transmission systems. This varying voltage output is used for dimming street lights, varying heating temperature in homes and industry, speed control of fans and winding machines and many other applications. These systems need switching elements which can bear high voltage. Frequently, high power MOSFETS are used as the switching element. Their advantage is that they generate less lower-order harmonics. They have the physical limitation of maximum blocking voltage; excessive heating is also an issue for MOSFET based controllers. Amongst other options, an anti-parallel pair of SCRs has the advantage over a TRIAC in controlling highly inductive loads. Although TRIACs have the advantage of a comparatively simpler gate circuit, TRIACs have lower dv/dt ratings than SCRs and are available in only small ratings. Moreover, the reliability of a SCR is more than that of a TRIAC [1]. SCR is a reliable solution when it comes to AC voltage control at high power as they are available in higher ratings. However, SCR based system can only be controlled by phase angle control method. This method generates more harmonic distortions [2]. Moreover synchronization with AC supply is necessary when the control mechanism is provided by microcontrollers. The gating circuit required is relatively more complex. The provision of feedback allows output voltage to be stable and maintain the same RMS value of voltage while there is change in the supply voltage [3]. The gain of the error signal of the feedback control system can be varied to obtain a slower or faster response of the system thus allowing soft start.
A quasi-3D model has been developed to simulate the flow in planar microfluidic systems with low ... more A quasi-3D model has been developed to simulate the flow in planar microfluidic systems with low Reynolds numbers. The model was developed by decomposing the flow profile along the height of a microfluidic system into a Fourier series. It was validated against the analytical solution for flow in a straight rectangular channel and the full 3D numerical COMSOL Navier-Stokes solver for flow in a T-channel. Comparable accuracy to the full 3D numerical solution was achieved by using only three Fourier terms with a significant decrease in computation time. The quasi-3D model was used to model flows in a micro-flow cytometer chip on a desktop computer and good agreement between the simulation and the experimental results was found.
A quasi-3D model has been developed to simulate the flow in planar microfluidic systems with low ... more A quasi-3D model has been developed to simulate the flow in planar microfluidic systems with low Reynolds numbers. The model was developed by decomposing the flow profile along the height of a microfluidic system into a Fourier series. It was validated against the analytical solution for flow in a straight rectangular channel and the full 3D numerical COMSOL Navier-Stokes solver for flow in a T-channel. Comparable accuracy to the full 3D numerical solution was achieved by using only three Fourier terms with a significant decrease in computation time. The quasi-3D model was used to model flows in a micro-flow cytometer chip on a desktop computer and good agreement between the simulation and the experimental results was found.
This paper describes the development of a prototype of a microcontroller-based phase angle contro... more This paper describes the development of a prototype of a microcontroller-based phase angle controlled single-phase AC voltage controller that can efficiently control AC voltage and also accommodates soft start capability for single-phase induction motors. The output voltage of the controller is regulated to maintain a desired fixed RMS value and provide stabilized output by implementing a feedback control system. One microcontroller generates PWM signals in synchronism with the supply voltage to control the firing angle of thyristors while a second microcontroller remains dedicated for measuring the RMS value of the output voltage and sending that to the main microcontroller for the purpose of feedback control. The provision for soft starting of a load is also incorporated into this prototype. Index Terms-AC voltage controller, Automatic voltage regulation, Soft start I. INTRODUCTION PWM-based AC voltage controllers are widely used in UPS and high power flexible AC transmission systems. This varying voltage output is used for dimming street lights, varying heating temperature in homes and industry, speed control of fans and winding machines and many other applications. These systems need switching elements which can bear high voltage. Frequently, high power MOSFETS are used as the switching element. Their advantage is that they generate less lower-order harmonics. They have the physical limitation of maximum blocking voltage; excessive heating is also an issue for MOSFET based controllers. Amongst other options, an anti-parallel pair of SCRs has the advantage over a TRIAC in controlling highly inductive loads. Although TRIACs have the advantage of a comparatively simpler gate circuit, TRIACs have lower dv/dt ratings than SCRs and are available in only small ratings. Moreover, the reliability of a SCR is more than that of a TRIAC [1]. SCR is a reliable solution when it comes to AC voltage control at high power as they are available in higher ratings. However, SCR based system can only be controlled by phase angle control method. This method generates more harmonic distortions [2]. Moreover synchronization with AC supply is necessary when the control mechanism is provided by microcontrollers. The gating circuit required is relatively more complex. The provision of feedback allows output voltage to be stable and maintain the same RMS value of voltage while there is change in the supply voltage [3]. The gain of the error signal of the feedback control system can be varied to obtain a slower or faster response of the system thus allowing soft start.
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Papers by Zahurul Islam