This chapter is part of the book Vortex Flows and Applications (on the front cover: Vortex Domina... more This chapter is part of the book Vortex Flows and Applications (on the front cover: Vortex Dominated Flows), prepared by the members of the Romanian Academic Consortium for Research and Development on Fluid Dynamics: ACCORD-FluiD.
This chapter is part of the book Vortex Flows and Applications (on the front cover: Vortex Domina... more This chapter is part of the book Vortex Flows and Applications (on the front cover: Vortex Dominated Flows), prepared by the members of the Romanian Academic Consortium for Research and Development on Fluid Dynamics: ACCORD-FluiD.
UPB Scientific Bulletin, Series D: Mechanical Engineering
A modified form of Honey Bees Mating Optimization Algorithm (HBMOA) has been used to optimize the... more A modified form of Honey Bees Mating Optimization Algorithm (HBMOA) has been used to optimize the design of a water distribution network for a town with 50,000 inhabitants. HBMOA is an evolutionary algorithm, highly ranked among the most known and effective algorithms in the literature. Within HBMOA, the search procedure is inspired by the process of mating in a real honey bee colony. Optimizing the design of a hydraulic network means to obtain the smallest network cost, under imposed hydraulic constraints. The water distribution network designed in this paper corresponds to a gravity distribution scheme, consisting of a looped network with 42 junctions, 78 pipes and a single source (a reservoir). All pipes were selected among 10 available pipe sizes, with diameters ranging from 50 mm, to 400 mm, meaning that there are 1078 design options. In this paper, 90000 design options have been investigated, by running HBMOA for 50 times, with 30 global iterations per run and 60 design soluti...
This scientific poster synthesizes some of my results on the Highly distorted moving fluid-fluid ... more This scientific poster synthesizes some of my results on the Highly distorted moving fluid-fluid interfaces, e.g. collapsing bubbles; jet break-up; bubbles and drops formation; Drop-on-Demand. Like the falling raindrops on the water surface, the bursting bubble process leads to the production of two types of drops: (i) film droplets; (ii) jet drops. The time spanned between film cap rupture and the first jet drop ejection is of the order of milliseconds. The collapse sequence of a bursting bubble process was modelled using a Boundary Element Method (BEM), in a potential flow of a pure viscous fluid assumption. Drop-on-Demand technology enables to control the drops ejection, from a vertically capillary nozzle, by piezoelectric stimulation. DOD applies in Microfluidics, from the ink-jet printers, to Bio-MEMS. The DOD numerical simulation was made through BEM, by taking into account the capillary effects and only partially the viscous effects. To prevent numerical instabilities, the ti...
Rezumat: Lucrarea îşi propune etalonarea unui canal Venturi cu secţiune dreptunghiulară, proiecta... more Rezumat: Lucrarea îşi propune etalonarea unui canal Venturi cu secţiune dreptunghiulară, proiectat şi construit pentru măsurarea debitelor foarte mici (sub 4 l/s) în curgerile cu suprafaţă liberă. Canalul de măsură Venturi cu pereţi din plexiglass a fost montat pe o instalaţie de laborator în circuit închis, prevăzută cu un canal vitrat şi o conductă de recirculare, pe care debitul real a fost măsurat cu ajutorul unei diafragme. Coeficienţii de debit calibraţi experimental au fost comparaţi cu cei obţinuţi în alte studii dovedind că măsurarea debitelor mici se poate extrapola cu bune rezultate până la debite mai mari decât 2,5 l/s. Curgerea cu suprafaţă liberă a fost modelată în diferenţe finite cu ajutorul programului HEC-RAS obţinându-se valori ale mărimilor hidraulice calculate foarte apropiate de cele măsurate .
Drop-On-Demand technology, abbreviated DOD, enables to eject a drop from a capillary nozzle using... more Drop-On-Demand technology, abbreviated DOD, enables to eject a drop from a capillary nozzle using piezoelectric stimulation. This technology is particularly appropriate to control the frequency, size and velocity of the droplet. There are many DOD applications in Microfluidics, ranging from the classical ink-jet printers or engines injection systems, to the deposition of polymeric fluids on microchips for DNA in-situ synthesis. The present study emphasizes on the numerical simulation of droplet formation at a vertically capillary tip, following a piezoelectric stimulation process applied to the capillary wall.
Fluid dynamics of capillary tubes is one of the very actual topic of investigation in biofluid me... more Fluid dynamics of capillary tubes is one of the very actual topic of investigation in biofluid mechanics. In particular, the modeling blood flow in capillaries is of great importance in establishing the local flow pattern associated with stenosis and arteriosclerosis. The paper investigates the behavior of Newtonian and shear thinning fluids in Poiseuille capillary flows. Experiments and numerical simulations with FLUENT code are performed in curve capillary geometries for Re∈[1 ÷ 1000] and l/d ∈[10 ÷ 10 4 ]. In simulations two rheological models are used for blood: (i) Newtonian fluid with slipping at the wall, (ii) the shear thinning Cross relation. Both models evidence a decreasing of pressure loss in capillary, in comparison to the pure viscous model with no-slip boundary condition (at the same flow rate). Further investigations are focused on (i) visualizations under microscope of flow separation areas in curved capillaries (oil-water emulsions, similar fluid with blood); (ii) ...
The Honey Bees Mating Optimization Algorithm (HBMOA) has been used to optimize the design of a wa... more The Honey Bees Mating Optimization Algorithm (HBMOA) has been used to optimize the design of a water distribution network, meaning to obtain the least-cost design of that looped hydraulic network. HBMOA is a new evolutionary algorithm, where the search procedure is inspired by the process of mating in a real honey bee colony. The performances of two modified HBMOA forms have been analysed, by comparing our results obtained for the Hanoi water distribution network (a well known test-case), with other results obtained using other stochastic methods for combinatorial optimization (such as the Ant Colony Optimization Algorithm, the Simulated Annealing Algorithm, and various formulations based on Genetic Algorithms). Among all those methods, the 2nd modified form of HBMOA, an original form proposed here, denoted HBMOA-M2, gives the smallest cost of Hanoi network. Thus, HBMOA-M2 can be highly ranked among the most known and effective algorithms in the literature.
Drop-on-Demand (DOD) technology enables to control the ejection of drops, from a vertically capil... more Drop-on-Demand (DOD) technology enables to control the ejection of drops, from a vertically capillary nozzle, by piezoelectric stimulation. DOD applies in microfluidics, from the ink-jet printers to Bio-MEMS. This study emphasizes on the numerical simulation of the drop evolution during its formation and ejection by DOD technology. The highly distorted interface evolution represents an axisymmetric transient free-boundary problem, which is modelled here through a Boundary Element Method. An irrotational flow model can reproduce most observed experimental data on drop size, velocity, frequency, and conditions for non-satellite formation. Viscous effects are included to some extent, as it is allowed for potential flows of fluids with constant viscosity, the normal viscous stress at the interface being expressed in terms of the velocity potential. The time progression is made with a 4th order Runge-Kutta explicit numerical scheme. The time step is varied upon a stability criterion. The...
The paper presents a methodology for computing the chlorine concentration decay in a water distri... more The paper presents a methodology for computing the chlorine concentration decay in a water distribution system over an extended period of time. A numerical model of the distribution network, designed for about 10000 inhabitants, is created in EPANET 2.0. The variable water demand over a 24 h period is implemented via flow pattern statements. Both hydraulic and water quality analysis are performed in order to obtain the time dependent flow within the network, as well as the time dependent pressure and chlorine concentration at each node. A constant concentration of chlorine is injected upstream, at the reservoir; then, the downstream residual is computed. Reactions occurring in the bulk flow are modelled with a first-order decay law, where the instantaneous rate of reaction is assumed to depend upon the chlorine concentration.
UPB Scientific Bulletin, Series C: Electrical Engineering
The paper presents a methodology for computing the pumping stations operating parameters upon a v... more The paper presents a methodology for computing the pumping stations operating parameters upon a variable demand. The study-case is performed for the complex water distribution network of Oradea (Romania), which incorporates 5 interconnected pumping stations, three tanks and a source of water. Oradea’s water distribution network is modelled within EPANET through a main emitter, and the variable water demand is implemented by adjusting the throttle control valves (TCV) placed on 7 main pipes, upstream of the emitter. A TCV simulates a partially closed valve by adjusting the minor head loss coefficient of the valve, using simple controls. The numerical model of the pumping stations is created in EPANET and the operating algorithm of each pumping station is implemented via control statements (rule-based controls). Such an operating algorithm is created for one variable speed driven pump, in each group of pumps coupled in parallel. A hydraulic analysis over a 48 h period is performed wit...
Two-dimensional numerical modelling of the stationary flow around a blade of the Achard turbine, ... more Two-dimensional numerical modelling of the stationary flow around a blade of the Achard turbine, a new water-current turbine concept, is performed both with COMSOL Multiphysics 3.3 and with Fluent 6.01 software, in order to compare the results and the software capabilities. The k − ε turbulence model has been selected and same geometry and boundary conditions were considered within computations.
This chapter is part of the book Vortex Flows and Applications (on the front cover: Vortex Domina... more This chapter is part of the book Vortex Flows and Applications (on the front cover: Vortex Dominated Flows), prepared by the members of the Romanian Academic Consortium for Research and Development on Fluid Dynamics: ACCORD-FluiD.
This chapter is part of the book Vortex Flows and Applications (on the front cover: Vortex Domina... more This chapter is part of the book Vortex Flows and Applications (on the front cover: Vortex Dominated Flows), prepared by the members of the Romanian Academic Consortium for Research and Development on Fluid Dynamics: ACCORD-FluiD.
UPB Scientific Bulletin, Series D: Mechanical Engineering
A modified form of Honey Bees Mating Optimization Algorithm (HBMOA) has been used to optimize the... more A modified form of Honey Bees Mating Optimization Algorithm (HBMOA) has been used to optimize the design of a water distribution network for a town with 50,000 inhabitants. HBMOA is an evolutionary algorithm, highly ranked among the most known and effective algorithms in the literature. Within HBMOA, the search procedure is inspired by the process of mating in a real honey bee colony. Optimizing the design of a hydraulic network means to obtain the smallest network cost, under imposed hydraulic constraints. The water distribution network designed in this paper corresponds to a gravity distribution scheme, consisting of a looped network with 42 junctions, 78 pipes and a single source (a reservoir). All pipes were selected among 10 available pipe sizes, with diameters ranging from 50 mm, to 400 mm, meaning that there are 1078 design options. In this paper, 90000 design options have been investigated, by running HBMOA for 50 times, with 30 global iterations per run and 60 design soluti...
This scientific poster synthesizes some of my results on the Highly distorted moving fluid-fluid ... more This scientific poster synthesizes some of my results on the Highly distorted moving fluid-fluid interfaces, e.g. collapsing bubbles; jet break-up; bubbles and drops formation; Drop-on-Demand. Like the falling raindrops on the water surface, the bursting bubble process leads to the production of two types of drops: (i) film droplets; (ii) jet drops. The time spanned between film cap rupture and the first jet drop ejection is of the order of milliseconds. The collapse sequence of a bursting bubble process was modelled using a Boundary Element Method (BEM), in a potential flow of a pure viscous fluid assumption. Drop-on-Demand technology enables to control the drops ejection, from a vertically capillary nozzle, by piezoelectric stimulation. DOD applies in Microfluidics, from the ink-jet printers, to Bio-MEMS. The DOD numerical simulation was made through BEM, by taking into account the capillary effects and only partially the viscous effects. To prevent numerical instabilities, the ti...
Rezumat: Lucrarea îşi propune etalonarea unui canal Venturi cu secţiune dreptunghiulară, proiecta... more Rezumat: Lucrarea îşi propune etalonarea unui canal Venturi cu secţiune dreptunghiulară, proiectat şi construit pentru măsurarea debitelor foarte mici (sub 4 l/s) în curgerile cu suprafaţă liberă. Canalul de măsură Venturi cu pereţi din plexiglass a fost montat pe o instalaţie de laborator în circuit închis, prevăzută cu un canal vitrat şi o conductă de recirculare, pe care debitul real a fost măsurat cu ajutorul unei diafragme. Coeficienţii de debit calibraţi experimental au fost comparaţi cu cei obţinuţi în alte studii dovedind că măsurarea debitelor mici se poate extrapola cu bune rezultate până la debite mai mari decât 2,5 l/s. Curgerea cu suprafaţă liberă a fost modelată în diferenţe finite cu ajutorul programului HEC-RAS obţinându-se valori ale mărimilor hidraulice calculate foarte apropiate de cele măsurate .
Drop-On-Demand technology, abbreviated DOD, enables to eject a drop from a capillary nozzle using... more Drop-On-Demand technology, abbreviated DOD, enables to eject a drop from a capillary nozzle using piezoelectric stimulation. This technology is particularly appropriate to control the frequency, size and velocity of the droplet. There are many DOD applications in Microfluidics, ranging from the classical ink-jet printers or engines injection systems, to the deposition of polymeric fluids on microchips for DNA in-situ synthesis. The present study emphasizes on the numerical simulation of droplet formation at a vertically capillary tip, following a piezoelectric stimulation process applied to the capillary wall.
Fluid dynamics of capillary tubes is one of the very actual topic of investigation in biofluid me... more Fluid dynamics of capillary tubes is one of the very actual topic of investigation in biofluid mechanics. In particular, the modeling blood flow in capillaries is of great importance in establishing the local flow pattern associated with stenosis and arteriosclerosis. The paper investigates the behavior of Newtonian and shear thinning fluids in Poiseuille capillary flows. Experiments and numerical simulations with FLUENT code are performed in curve capillary geometries for Re∈[1 ÷ 1000] and l/d ∈[10 ÷ 10 4 ]. In simulations two rheological models are used for blood: (i) Newtonian fluid with slipping at the wall, (ii) the shear thinning Cross relation. Both models evidence a decreasing of pressure loss in capillary, in comparison to the pure viscous model with no-slip boundary condition (at the same flow rate). Further investigations are focused on (i) visualizations under microscope of flow separation areas in curved capillaries (oil-water emulsions, similar fluid with blood); (ii) ...
The Honey Bees Mating Optimization Algorithm (HBMOA) has been used to optimize the design of a wa... more The Honey Bees Mating Optimization Algorithm (HBMOA) has been used to optimize the design of a water distribution network, meaning to obtain the least-cost design of that looped hydraulic network. HBMOA is a new evolutionary algorithm, where the search procedure is inspired by the process of mating in a real honey bee colony. The performances of two modified HBMOA forms have been analysed, by comparing our results obtained for the Hanoi water distribution network (a well known test-case), with other results obtained using other stochastic methods for combinatorial optimization (such as the Ant Colony Optimization Algorithm, the Simulated Annealing Algorithm, and various formulations based on Genetic Algorithms). Among all those methods, the 2nd modified form of HBMOA, an original form proposed here, denoted HBMOA-M2, gives the smallest cost of Hanoi network. Thus, HBMOA-M2 can be highly ranked among the most known and effective algorithms in the literature.
Drop-on-Demand (DOD) technology enables to control the ejection of drops, from a vertically capil... more Drop-on-Demand (DOD) technology enables to control the ejection of drops, from a vertically capillary nozzle, by piezoelectric stimulation. DOD applies in microfluidics, from the ink-jet printers to Bio-MEMS. This study emphasizes on the numerical simulation of the drop evolution during its formation and ejection by DOD technology. The highly distorted interface evolution represents an axisymmetric transient free-boundary problem, which is modelled here through a Boundary Element Method. An irrotational flow model can reproduce most observed experimental data on drop size, velocity, frequency, and conditions for non-satellite formation. Viscous effects are included to some extent, as it is allowed for potential flows of fluids with constant viscosity, the normal viscous stress at the interface being expressed in terms of the velocity potential. The time progression is made with a 4th order Runge-Kutta explicit numerical scheme. The time step is varied upon a stability criterion. The...
The paper presents a methodology for computing the chlorine concentration decay in a water distri... more The paper presents a methodology for computing the chlorine concentration decay in a water distribution system over an extended period of time. A numerical model of the distribution network, designed for about 10000 inhabitants, is created in EPANET 2.0. The variable water demand over a 24 h period is implemented via flow pattern statements. Both hydraulic and water quality analysis are performed in order to obtain the time dependent flow within the network, as well as the time dependent pressure and chlorine concentration at each node. A constant concentration of chlorine is injected upstream, at the reservoir; then, the downstream residual is computed. Reactions occurring in the bulk flow are modelled with a first-order decay law, where the instantaneous rate of reaction is assumed to depend upon the chlorine concentration.
UPB Scientific Bulletin, Series C: Electrical Engineering
The paper presents a methodology for computing the pumping stations operating parameters upon a v... more The paper presents a methodology for computing the pumping stations operating parameters upon a variable demand. The study-case is performed for the complex water distribution network of Oradea (Romania), which incorporates 5 interconnected pumping stations, three tanks and a source of water. Oradea’s water distribution network is modelled within EPANET through a main emitter, and the variable water demand is implemented by adjusting the throttle control valves (TCV) placed on 7 main pipes, upstream of the emitter. A TCV simulates a partially closed valve by adjusting the minor head loss coefficient of the valve, using simple controls. The numerical model of the pumping stations is created in EPANET and the operating algorithm of each pumping station is implemented via control statements (rule-based controls). Such an operating algorithm is created for one variable speed driven pump, in each group of pumps coupled in parallel. A hydraulic analysis over a 48 h period is performed wit...
Two-dimensional numerical modelling of the stationary flow around a blade of the Achard turbine, ... more Two-dimensional numerical modelling of the stationary flow around a blade of the Achard turbine, a new water-current turbine concept, is performed both with COMSOL Multiphysics 3.3 and with Fluent 6.01 software, in order to compare the results and the software capabilities. The k − ε turbulence model has been selected and same geometry and boundary conditions were considered within computations.
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