Roberto Sosa | Universidad de Buenos Aires (original) (raw)
Papers by Roberto Sosa
cricyt.edu.ar
Se describe el diseño, construcción y validación de un equipo para ensayar rotores eólicos en peq... more Se describe el diseño, construcción y validación de un equipo para ensayar rotores eólicos en pequeña escala. Por un lado se diseñó y construyó un pequeño banco de ensayos que permite estudiar generadores eólicos de paso variable y con diferentes geometrías de las aspas. Dicho equipo permitirá, entre otras cosas, el relevamiento de la curva de potencia extraída por el generador en función de la velocidad del viento incidente. Por otro lado, se implementó un algoritmo basado en la teoría BEM que permite tanto estimar la curva de potencia para un generador eólico a partir del conocimiento de la geometría de las aspas del mismo como determinar el alabeo y la cuerda del aspa ideal para un conjunto de perfiles alares dados a lo largo del aspa y condiciones de diseño del generador definidas previamente.
Abstract. In this paper, we address the problem of estimating the motion of fluid flows that are ... more Abstract. In this paper, we address the problem of estimating the motion of fluid flows that are visualized through a Schlieren system. Such a system is well known in fluid mechanics as it enables the visualization of unseeded flows. As the resulting images exhibit very low photometric contrasts, classical motion estimation methods based on the brightness consistency assumption (correlation-based approaches, optical flow methods) are completely inefficient. This work aims at proposing a sound energy based estimator dedicated to these particular images. The energy function to be minimized is composed of (a) a novel data term describing the fact that the observed luminance is linked to the gradient of the fluid density and (b) a specific div curl regularization term. The relevance of our estimator is demonstrated on real-world sequences. 1
IEEE Transactions on Dielectrics and Electrical Insulation, 2009
Journal of Electrostatics, 2013
ABSTRACT It has been demonstrated that dielectric barrier actuators can be used to induce electro... more ABSTRACT It has been demonstrated that dielectric barrier actuators can be used to induce electrohydrodynamics flows in air as well as in gas. These actuators are often called surface non-thermal plasma actuators in gas applications. Plasma actuators have proved their efficiency for aerodynamics flow control in air. However dielectric barrier devices don't generate plasma in liquids. Electroconvective flows are induced by charge injection at the surface electrode tip. These dielectric barrier injectors (DBI) are particularly well adapted for wall jet production vortex, shedding, and mixing layer applications in dielectric liquids. Dielectric barrier actuators have proved their efficiency on various dielectric liquids. In this study, a dielectric barrier device is tested on silicon oil. Instead of the typical wall jet, a reverse flow is observed in specific configurations. Particle Image Velocimetry and Shlieren measurements are achieved to characterize the unusual electroconvective flow.
Journal of Electrostatics, Jul 1, 2006
This work analyzes the effects produced by an EHD actuator on the flow around an airfoil at low R... more This work analyzes the effects produced by an EHD actuator on the flow around an airfoil at low Re numbers (ReE10 4 ). The analysis is undertaken from flow visualizations and measurements of the surface pressure distributions. The experiments indicate that, for low Re number, the effects of the actuation depend on the power added to the flow and on the relative distance between the actuator and the separation line. r
Surface dielectric barrier discharges (DBD) used for airflow control are investigated by force me... more Surface dielectric barrier discharges (DBD) used for airflow control are investigated by force measurements and time-averaged particle image velocimetry. Three types of plasma actuators are studied: a typical single DBD based on two electrodes flush mounted on both sides of a dielectric plate, an extended DBD that uses a third electrode supplied by a positive dc voltage and a sliding discharge with a negative dc voltage. On one hand, results show that the extended DBD allows us to increase slightly the body force and the produced velocity. On the other hand, in the case of a sliding discharge, and only if the negative dc voltage is well adjusted compared to the ac sine high voltage, there is a significant enhancement of the force. Moreover, the electric wind velocity is increased and its topology is strongly modified, resulting in a more intense suction effect above the discharge.
35th AIAA Plasmadynamics and Lasers Conference, 2004
Actuators are devices that add momentum to a flow with the objective of modifying its characteris... more Actuators are devices that add momentum to a flow with the objective of modifying its characteristics. The electrohydrodynamic (EHD) actuators produce a weakly ionized gas and add momentum to the flow by the collisions of charged particles with the neutral ...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2006
We analyze the modifications of the flow around a NACA 0015 airfoil when the flow is perturbed wi... more We analyze the modifications of the flow around a NACA 0015 airfoil when the flow is perturbed with an electrohydrodynamic (EHD) actuator. The device used consists of two bare electrodes flush mounted on the surface of the model operated in a discharge regime ...
Lecture Notes in Computer Science, 2006
In this paper, we address the problem of estimating the motion of fluid flows that are visualized... more In this paper, we address the problem of estimating the motion of fluid flows that are visualized through a Schlieren system. Such a system is well known in fluid mechanics as it enables the visualization of unseeded flows. As the resulting images exhibit very low photometric contrasts, classical motion estimation methods based on the brightness consistency assumption (correlation-based approaches, optical flow methods) are completely inefficient. This work aims at proposing a sound energy based estimator dedicated to these particular images. The energy function to be minimized is composed of (a) a novel data term describing the fact that the observed luminance is linked to the gradient of the fluid density and (b) a specific div curl regularization term. The relevance of our estimator is demonstrated on real-world sequences.
Thin Solid Films, 2008
]. Their principle is to produce a plasma in which ions are submitted to electric field. Then, th... more ]. Their principle is to produce a plasma in which ions are submitted to electric field. Then, the molecules of air are drifted by ions, generating an "electric wind". In the LEA (Laboratoire d'Etudes Aérodynamiques), three kinds of actuators have been mainly performed and studied: the DC actuator, the DBD actuator and the sliding discharge actuator. In the present paper we will first examine briefly the setup of each kind of actuators and how they produce electric wind. Then we will describe a new kind of device based on two DBD actuators and performed to generate a micro-jet in an adjustable direction.
Physica Scripta, 2008
A sliding discharge using two electrodes on a dielectric layer (upper electrodes) and a third ele... more A sliding discharge using two electrodes on a dielectric layer (upper electrodes) and a third electrode on its reverse side, facing the upper inter-electrode gap (lower electrode) was generated in air at atmospheric pressure. Application of a high dc negative voltage to one of the upper electrodes and to the lower electrode, and a high ac voltage to the other upper electrode generates a stable and homogeneous surface plasma (plasma sheet) in the upper electrode's gap. In this work, the plasma sheet optical emission of the spectral bands corresponding to the 0-0 transition of the second positive system of N 2 (λ = 337.1 nm) and the first negative system of N + 2 (λ = 391.4 nm) has been measured and analysed. It was found that the plasma sheet consisted of a set of cathode-directed streamers. The streamer generation frequency and its transit time across the inter-electrode gap have been studied. On the basis of a reliable atomic model to interpret the line emission, the total electron number at the streamer head and the electron temperature have been derived.
Journal of Physics D: Applied Physics, 2008
A quasi-steady sliding discharge at atmospheric pressure is generated by combining a surface diel... more A quasi-steady sliding discharge at atmospheric pressure is generated by combining a surface dielectric barrier together with a DC corona discharge in a three-electrode geometry. The discharge extends along the whole side-length of the electrodes (150 mm) and covers the full inter-electrode gap (30 mm). It is found that this discharge is composed of repetitive streamers that are uniformly distributed along the whole electrode length and that propagate along the inter-electrode gap with an average velocity of ∼2 × 10 7 cm s −1 , and with an average electric field of ∼120 kV cm −1 and a total particle number of ∼5 × 10 8 at the streamer head. Assuming that the electron distribution function reaches an equilibrium value with the electric field, an electron temperature of 9 eV at the streamer head is obtained. The streamer frequency is around 5 × 10 4 Hz for a well-developed sliding discharge regime, and the time-averaged electron density amounts to 1.5 × 10 7 cm −3 .
Journal of Physics D: Applied Physics, 2009
A study of the electrical characteristics of the trielectrode plasma curtain (TPC) discharge is p... more A study of the electrical characteristics of the trielectrode plasma curtain (TPC) discharge is presented. The influence of the air-gap size (for a fixed value of the inter-electrode distance) on the discharge behaviour has been exhaustively studied. The TPC discharge is based on the combination of a dielectric barrier discharge (DBD) with a corona discharge (CD) in a three electrode system, and basically it consists of the 'stretching' of a pure DBD by the action of a negative CD generated between the active electrode of the dielectric barrier and a remote third electrode. It was found that the general trend of the electrical characteristic curves (the average discharge current and the streamer frequency as functions of the AC and DC biasing voltages) was very similar for all the air-gap values considered. Our results indicate that the development of the TPC discharge requires two conditions: (a) the presence of a positive cycle of a well-developed DBD together with a CD where the remote electrode acts as the cathode and (b) a voltage drop between the DBD electrode and the remote electrode high enough to obtain an average electric field in the gap that must exceed a minimum average electric field value in the streamer channel necessary for its propagation across the gap (≈6.3 kV cm −1 in our experimental conditions).
Journal of Physics D: Applied Physics, 2007
The electrical characteristics of a plasma sheet device used for subsonic airflow control are stu... more The electrical characteristics of a plasma sheet device used for subsonic airflow control are studied in this paper. Experiments are undertaken with a two-wire asymmetrical (different diameters, opposite polarity) electrode configuration connected to dc high voltage sources in the presence of a dielectric plate and under different gases (dry air, nitrogen and oxygen). For large distances electrode-plates it has been found that the discharge current consists of a purely dc component. The proximity of the plate reduces notably this dc current component until a limit situation for which the electrodes practically lay on the plate and a current pulsed regime is superimposed on the dc (small) component, thus establishing a plasma sheet regime. This regime could be reached only when the small wire was positive. This work establishes that the pulsed regime may be associated with a succession of positive streamers (cathode directed) which formation is promoted by different parameters of the gas and surface characteristics (thresholds of photoionization and photoemission, charge deposition,...). The dc component seems to be produced by a small number of electrons originated in the ionization region of the negative corona that are amplified in the ionization region of the positive corona. The charged particles produced during the streamer propagation could contribute appreciably to the ion momentum transfer to the gas. This transfer should be due very likely to the drift of the charged species present in the streamer channel during the streamer collapsing phase. The source of momentum transfer associated with the dc current would always persist with a magnitude that depends on the intensity of this current.
Journal of Physics D: Applied Physics, 2008
Active flow control is a rapidly developing topic because the associated industrial applications ... more Active flow control is a rapidly developing topic because the associated industrial applications are of immense importance, particularly for aeronautics. Among all the flow control methods, such as the use of mechanical flaps or wall jets, plasma-based devices are very promising devices. The main advantages of such systems are their robustness, their simplicity, their low-power consumption and that they allow a real-time control at high frequency. This paper deals with an experimental study about the electric wind produced by a surface discharge based on a three-electrode geometry. This new device is composed of a typical two-electrode surface barrier discharge excited by an AC high voltage, plus a third electrode at which a DC high voltage is applied in order to extend the discharge region and to accelerate the ion drift velocity. In the first part the electrical current of these different surface discharges is presented and discussed. This shows that the current behaviour depends on the DC component polarity. The second part is dedicated to analysing the electric wind characteristics through Schlieren visualizations and to measuring its time-averaged velocity with a Pitot tube sensor. The results show that an excitation of the electrodes with an AC voltage plus a positive DC component can significantly modify the topology of the electric wind produced by a single DBD. In practice, this DC component allows us to increase the value of the maximum induced velocity (up to +150% at a few centimetres downstream of the discharge) and the plasma extension, to enhance the depression occurring above the discharge region and to increase the discharge-induced mass flow rate (up to +100%), without increasing the electrical power consumption.
Journal of Physics: Conference Series, 2009
The drag reduction in a circular cylinder was explored by means of a novel three electrode plasma... more The drag reduction in a circular cylinder was explored by means of a novel three electrode plasma actuator (DBDE). The DBDE actuator can reduce the drag coefficient up to a ~25% respect to the base flow drag coefficient. It has been demonstrated that, within the present experimental conditions, the DBDE actuator, for a fixed value of the power coefficient, adds a higher momentum to the flow and, consequently, produces a higher drag reduction than the DBD actuator with the same power coefficient. The actuator efficiency was analysed in terms of the momentum added to the flow revealing similar behaviour for both kind of actuators. However to produce similar levels of actuation both kind of actuators require different values of V AC voltages that resulted always lower for DBDE. The reduction in this high voltage value is highly beneficial as is directly related to: a lower HV AC source power requirement, a reduction in the dielectric breakdown probability of the device and a reduction in leakage currents.
Journal of Physics: Conference Series, 2009
We present in this work a way to construct reduced order model (ROM) for wake flows at low Reynol... more We present in this work a way to construct reduced order model (ROM) for wake flows at low Reynolds numbers, from experimental data of particle image velocimetry (PIV). The proper orthogonal decomposition method (POD) allows the extraction of a small number of functions or modes that describes the flow velocity field. Galerkin projection of Navier Stokes equations onto these modes leads to obtain a system of ordinary equations, the reduced order model. We take interest particularly in the study of the modifications introduced by an electrohydrodynamic (EHD) actuator on the flow. EHD action is obtained from a gaseous discherge of dielectric barrier type (DBD), produced by electrodes flush mounted on a cylinder surface. The reduced order model presents as an effective tool in order to analyse the coupled electrical and hydrodynamic phenomena. We focus on the flow changes considering the voltage between the electrodes as a control parameter.
cricyt.edu.ar
Se describe el diseño, construcción y validación de un equipo para ensayar rotores eólicos en peq... more Se describe el diseño, construcción y validación de un equipo para ensayar rotores eólicos en pequeña escala. Por un lado se diseñó y construyó un pequeño banco de ensayos que permite estudiar generadores eólicos de paso variable y con diferentes geometrías de las aspas. Dicho equipo permitirá, entre otras cosas, el relevamiento de la curva de potencia extraída por el generador en función de la velocidad del viento incidente. Por otro lado, se implementó un algoritmo basado en la teoría BEM que permite tanto estimar la curva de potencia para un generador eólico a partir del conocimiento de la geometría de las aspas del mismo como determinar el alabeo y la cuerda del aspa ideal para un conjunto de perfiles alares dados a lo largo del aspa y condiciones de diseño del generador definidas previamente.
Abstract. In this paper, we address the problem of estimating the motion of fluid flows that are ... more Abstract. In this paper, we address the problem of estimating the motion of fluid flows that are visualized through a Schlieren system. Such a system is well known in fluid mechanics as it enables the visualization of unseeded flows. As the resulting images exhibit very low photometric contrasts, classical motion estimation methods based on the brightness consistency assumption (correlation-based approaches, optical flow methods) are completely inefficient. This work aims at proposing a sound energy based estimator dedicated to these particular images. The energy function to be minimized is composed of (a) a novel data term describing the fact that the observed luminance is linked to the gradient of the fluid density and (b) a specific div curl regularization term. The relevance of our estimator is demonstrated on real-world sequences. 1
IEEE Transactions on Dielectrics and Electrical Insulation, 2009
Journal of Electrostatics, 2013
ABSTRACT It has been demonstrated that dielectric barrier actuators can be used to induce electro... more ABSTRACT It has been demonstrated that dielectric barrier actuators can be used to induce electrohydrodynamics flows in air as well as in gas. These actuators are often called surface non-thermal plasma actuators in gas applications. Plasma actuators have proved their efficiency for aerodynamics flow control in air. However dielectric barrier devices don't generate plasma in liquids. Electroconvective flows are induced by charge injection at the surface electrode tip. These dielectric barrier injectors (DBI) are particularly well adapted for wall jet production vortex, shedding, and mixing layer applications in dielectric liquids. Dielectric barrier actuators have proved their efficiency on various dielectric liquids. In this study, a dielectric barrier device is tested on silicon oil. Instead of the typical wall jet, a reverse flow is observed in specific configurations. Particle Image Velocimetry and Shlieren measurements are achieved to characterize the unusual electroconvective flow.
Journal of Electrostatics, Jul 1, 2006
This work analyzes the effects produced by an EHD actuator on the flow around an airfoil at low R... more This work analyzes the effects produced by an EHD actuator on the flow around an airfoil at low Re numbers (ReE10 4 ). The analysis is undertaken from flow visualizations and measurements of the surface pressure distributions. The experiments indicate that, for low Re number, the effects of the actuation depend on the power added to the flow and on the relative distance between the actuator and the separation line. r
Surface dielectric barrier discharges (DBD) used for airflow control are investigated by force me... more Surface dielectric barrier discharges (DBD) used for airflow control are investigated by force measurements and time-averaged particle image velocimetry. Three types of plasma actuators are studied: a typical single DBD based on two electrodes flush mounted on both sides of a dielectric plate, an extended DBD that uses a third electrode supplied by a positive dc voltage and a sliding discharge with a negative dc voltage. On one hand, results show that the extended DBD allows us to increase slightly the body force and the produced velocity. On the other hand, in the case of a sliding discharge, and only if the negative dc voltage is well adjusted compared to the ac sine high voltage, there is a significant enhancement of the force. Moreover, the electric wind velocity is increased and its topology is strongly modified, resulting in a more intense suction effect above the discharge.
35th AIAA Plasmadynamics and Lasers Conference, 2004
Actuators are devices that add momentum to a flow with the objective of modifying its characteris... more Actuators are devices that add momentum to a flow with the objective of modifying its characteristics. The electrohydrodynamic (EHD) actuators produce a weakly ionized gas and add momentum to the flow by the collisions of charged particles with the neutral ...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2006
We analyze the modifications of the flow around a NACA 0015 airfoil when the flow is perturbed wi... more We analyze the modifications of the flow around a NACA 0015 airfoil when the flow is perturbed with an electrohydrodynamic (EHD) actuator. The device used consists of two bare electrodes flush mounted on the surface of the model operated in a discharge regime ...
Lecture Notes in Computer Science, 2006
In this paper, we address the problem of estimating the motion of fluid flows that are visualized... more In this paper, we address the problem of estimating the motion of fluid flows that are visualized through a Schlieren system. Such a system is well known in fluid mechanics as it enables the visualization of unseeded flows. As the resulting images exhibit very low photometric contrasts, classical motion estimation methods based on the brightness consistency assumption (correlation-based approaches, optical flow methods) are completely inefficient. This work aims at proposing a sound energy based estimator dedicated to these particular images. The energy function to be minimized is composed of (a) a novel data term describing the fact that the observed luminance is linked to the gradient of the fluid density and (b) a specific div curl regularization term. The relevance of our estimator is demonstrated on real-world sequences.
Thin Solid Films, 2008
]. Their principle is to produce a plasma in which ions are submitted to electric field. Then, th... more ]. Their principle is to produce a plasma in which ions are submitted to electric field. Then, the molecules of air are drifted by ions, generating an "electric wind". In the LEA (Laboratoire d'Etudes Aérodynamiques), three kinds of actuators have been mainly performed and studied: the DC actuator, the DBD actuator and the sliding discharge actuator. In the present paper we will first examine briefly the setup of each kind of actuators and how they produce electric wind. Then we will describe a new kind of device based on two DBD actuators and performed to generate a micro-jet in an adjustable direction.
Physica Scripta, 2008
A sliding discharge using two electrodes on a dielectric layer (upper electrodes) and a third ele... more A sliding discharge using two electrodes on a dielectric layer (upper electrodes) and a third electrode on its reverse side, facing the upper inter-electrode gap (lower electrode) was generated in air at atmospheric pressure. Application of a high dc negative voltage to one of the upper electrodes and to the lower electrode, and a high ac voltage to the other upper electrode generates a stable and homogeneous surface plasma (plasma sheet) in the upper electrode's gap. In this work, the plasma sheet optical emission of the spectral bands corresponding to the 0-0 transition of the second positive system of N 2 (λ = 337.1 nm) and the first negative system of N + 2 (λ = 391.4 nm) has been measured and analysed. It was found that the plasma sheet consisted of a set of cathode-directed streamers. The streamer generation frequency and its transit time across the inter-electrode gap have been studied. On the basis of a reliable atomic model to interpret the line emission, the total electron number at the streamer head and the electron temperature have been derived.
Journal of Physics D: Applied Physics, 2008
A quasi-steady sliding discharge at atmospheric pressure is generated by combining a surface diel... more A quasi-steady sliding discharge at atmospheric pressure is generated by combining a surface dielectric barrier together with a DC corona discharge in a three-electrode geometry. The discharge extends along the whole side-length of the electrodes (150 mm) and covers the full inter-electrode gap (30 mm). It is found that this discharge is composed of repetitive streamers that are uniformly distributed along the whole electrode length and that propagate along the inter-electrode gap with an average velocity of ∼2 × 10 7 cm s −1 , and with an average electric field of ∼120 kV cm −1 and a total particle number of ∼5 × 10 8 at the streamer head. Assuming that the electron distribution function reaches an equilibrium value with the electric field, an electron temperature of 9 eV at the streamer head is obtained. The streamer frequency is around 5 × 10 4 Hz for a well-developed sliding discharge regime, and the time-averaged electron density amounts to 1.5 × 10 7 cm −3 .
Journal of Physics D: Applied Physics, 2009
A study of the electrical characteristics of the trielectrode plasma curtain (TPC) discharge is p... more A study of the electrical characteristics of the trielectrode plasma curtain (TPC) discharge is presented. The influence of the air-gap size (for a fixed value of the inter-electrode distance) on the discharge behaviour has been exhaustively studied. The TPC discharge is based on the combination of a dielectric barrier discharge (DBD) with a corona discharge (CD) in a three electrode system, and basically it consists of the 'stretching' of a pure DBD by the action of a negative CD generated between the active electrode of the dielectric barrier and a remote third electrode. It was found that the general trend of the electrical characteristic curves (the average discharge current and the streamer frequency as functions of the AC and DC biasing voltages) was very similar for all the air-gap values considered. Our results indicate that the development of the TPC discharge requires two conditions: (a) the presence of a positive cycle of a well-developed DBD together with a CD where the remote electrode acts as the cathode and (b) a voltage drop between the DBD electrode and the remote electrode high enough to obtain an average electric field in the gap that must exceed a minimum average electric field value in the streamer channel necessary for its propagation across the gap (≈6.3 kV cm −1 in our experimental conditions).
Journal of Physics D: Applied Physics, 2007
The electrical characteristics of a plasma sheet device used for subsonic airflow control are stu... more The electrical characteristics of a plasma sheet device used for subsonic airflow control are studied in this paper. Experiments are undertaken with a two-wire asymmetrical (different diameters, opposite polarity) electrode configuration connected to dc high voltage sources in the presence of a dielectric plate and under different gases (dry air, nitrogen and oxygen). For large distances electrode-plates it has been found that the discharge current consists of a purely dc component. The proximity of the plate reduces notably this dc current component until a limit situation for which the electrodes practically lay on the plate and a current pulsed regime is superimposed on the dc (small) component, thus establishing a plasma sheet regime. This regime could be reached only when the small wire was positive. This work establishes that the pulsed regime may be associated with a succession of positive streamers (cathode directed) which formation is promoted by different parameters of the gas and surface characteristics (thresholds of photoionization and photoemission, charge deposition,...). The dc component seems to be produced by a small number of electrons originated in the ionization region of the negative corona that are amplified in the ionization region of the positive corona. The charged particles produced during the streamer propagation could contribute appreciably to the ion momentum transfer to the gas. This transfer should be due very likely to the drift of the charged species present in the streamer channel during the streamer collapsing phase. The source of momentum transfer associated with the dc current would always persist with a magnitude that depends on the intensity of this current.
Journal of Physics D: Applied Physics, 2008
Active flow control is a rapidly developing topic because the associated industrial applications ... more Active flow control is a rapidly developing topic because the associated industrial applications are of immense importance, particularly for aeronautics. Among all the flow control methods, such as the use of mechanical flaps or wall jets, plasma-based devices are very promising devices. The main advantages of such systems are their robustness, their simplicity, their low-power consumption and that they allow a real-time control at high frequency. This paper deals with an experimental study about the electric wind produced by a surface discharge based on a three-electrode geometry. This new device is composed of a typical two-electrode surface barrier discharge excited by an AC high voltage, plus a third electrode at which a DC high voltage is applied in order to extend the discharge region and to accelerate the ion drift velocity. In the first part the electrical current of these different surface discharges is presented and discussed. This shows that the current behaviour depends on the DC component polarity. The second part is dedicated to analysing the electric wind characteristics through Schlieren visualizations and to measuring its time-averaged velocity with a Pitot tube sensor. The results show that an excitation of the electrodes with an AC voltage plus a positive DC component can significantly modify the topology of the electric wind produced by a single DBD. In practice, this DC component allows us to increase the value of the maximum induced velocity (up to +150% at a few centimetres downstream of the discharge) and the plasma extension, to enhance the depression occurring above the discharge region and to increase the discharge-induced mass flow rate (up to +100%), without increasing the electrical power consumption.
Journal of Physics: Conference Series, 2009
The drag reduction in a circular cylinder was explored by means of a novel three electrode plasma... more The drag reduction in a circular cylinder was explored by means of a novel three electrode plasma actuator (DBDE). The DBDE actuator can reduce the drag coefficient up to a ~25% respect to the base flow drag coefficient. It has been demonstrated that, within the present experimental conditions, the DBDE actuator, for a fixed value of the power coefficient, adds a higher momentum to the flow and, consequently, produces a higher drag reduction than the DBD actuator with the same power coefficient. The actuator efficiency was analysed in terms of the momentum added to the flow revealing similar behaviour for both kind of actuators. However to produce similar levels of actuation both kind of actuators require different values of V AC voltages that resulted always lower for DBDE. The reduction in this high voltage value is highly beneficial as is directly related to: a lower HV AC source power requirement, a reduction in the dielectric breakdown probability of the device and a reduction in leakage currents.
Journal of Physics: Conference Series, 2009
We present in this work a way to construct reduced order model (ROM) for wake flows at low Reynol... more We present in this work a way to construct reduced order model (ROM) for wake flows at low Reynolds numbers, from experimental data of particle image velocimetry (PIV). The proper orthogonal decomposition method (POD) allows the extraction of a small number of functions or modes that describes the flow velocity field. Galerkin projection of Navier Stokes equations onto these modes leads to obtain a system of ordinary equations, the reduced order model. We take interest particularly in the study of the modifications introduced by an electrohydrodynamic (EHD) actuator on the flow. EHD action is obtained from a gaseous discherge of dielectric barrier type (DBD), produced by electrodes flush mounted on a cylinder surface. The reduced order model presents as an effective tool in order to analyse the coupled electrical and hydrodynamic phenomena. We focus on the flow changes considering the voltage between the electrodes as a control parameter.