L'AIRE - Laboratori Aeronàutic i Industrial de Recerca i Estudis
http://hdl.handle.net/2117/3480
2017-08-22T05:46:22ZInfluence of data resolution in nonlinear loads model for harmonics prediction
http://hdl.handle.net/2117/106333
Influence of data resolution in nonlinear loads model for harmonics prediction
Balcells Sendra, Josep; Lamich Arocas, Manuel; Griful Ponsati, Eulàlia; Corbalán Fuertes, Montserrat
This paper describes the influence of data resolution in the agreement of models to predict harmonics generated by nonlinear loads (NLL), basically formed by single phase and three phase rectifiers, eventually combined with linear loads. We assume that the network supplying the NLL has significant impedances and that it is disturbed by other parallel, random and unknown neighbor loads, sharing part of the supply system. The aim of building NLL models is to make predictions on the amount and flow paths of harmonic currents generated by such NLL in case of using parallel filters. In this paper, the models are obtained from sets of (V,I) data taken at a certain point, called measuring point (MP) and are valid to predict the NLL behavior when random known or unknown parallel loads are connected upstream of this point. The technique used to obtain the models studied here is based on Multivariate Multiple Outputs Regression (MMOR) and will not be described in detail in this paper. This method allows obtaining a set of equations giving the current harmonics as a function of voltage harmonics observed at the measuring point (MP). The accordance between model and the experimental results is very dependent on the resolution and accuracy of V and I measurements at the MP and is the core matter of this paper.
2017-07-11T07:59:53ZBalcells Sendra, JosepLamich Arocas, ManuelGriful Ponsati, EulàliaCorbalán Fuertes, MontserratThis paper describes the influence of data resolution in the agreement of models to predict harmonics generated by nonlinear loads (NLL), basically formed by single phase and three phase rectifiers, eventually combined with linear loads. We assume that the network supplying the NLL has significant impedances and that it is disturbed by other parallel, random and unknown neighbor loads, sharing part of the supply system. The aim of building NLL models is to make predictions on the amount and flow paths of harmonic currents generated by such NLL in case of using parallel filters. In this paper, the models are obtained from sets of (V,I) data taken at a certain point, called measuring point (MP) and are valid to predict the NLL behavior when random known or unknown parallel loads are connected upstream of this point. The technique used to obtain the models studied here is based on Multivariate Multiple Outputs Regression (MMOR) and will not be described in detail in this paper. This method allows obtaining a set of equations giving the current harmonics as a function of voltage harmonics observed at the measuring point (MP). The accordance between model and the experimental results is very dependent on the resolution and accuracy of V and I measurements at the MP and is the core matter of this paper.A-posteriori error estimation for the finite point method with applications to compressible flow
http://hdl.handle.net/2117/104305
A-posteriori error estimation for the finite point method with applications to compressible flow
Ortega, Enrique; Flores Le Roux, Roberto Maurice; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo
An a-posteriori error estimate with application to inviscid compressible flow problems is presented. The estimate is a surrogate measure of the discretization error, obtained from an approximation to the truncation terms of the governing equations. This approximation is calculated from the discrete nodal differential residuals using a reconstructed solution field on a modified stencil of points. Both the error estimation methodology and the flow solution scheme are implemented using the Finite Point Method, a meshless technique enabling higher-order approximations and reconstruction procedures on general unstructured discretizations. The performance of the proposed error indicator is studied and applications to adaptive grid refinement are presented.
2017-05-11T08:48:09ZOrtega, EnriqueFlores Le Roux, Roberto MauriceOñate Ibáñez de Navarra, EugenioIdelsohn Barg, Sergio RodolfoAn a-posteriori error estimate with application to inviscid compressible flow problems is presented. The estimate is a surrogate measure of the discretization error, obtained from an approximation to the truncation terms of the governing equations. This approximation is calculated from the discrete nodal differential residuals using a reconstructed solution field on a modified stencil of points. Both the error estimation methodology and the flow solution scheme are implemented using the Finite Point Method, a meshless technique enabling higher-order approximations and reconstruction procedures on general unstructured discretizations. The performance of the proposed error indicator is studied and applications to adaptive grid refinement are presented.In situ particle zeta potential evaluation in electroosmotic flows from time-resolved microPIV measurements
http://hdl.handle.net/2117/103563
In situ particle zeta potential evaluation in electroosmotic flows from time-resolved microPIV measurements
Sureda Anfres, Miquel; Miller, Andrew; Diez, F. J.
A time-resolved microPIV method is presented to measure in an EOF the particles zeta potential in situ during the transient start-up of a microdevice. The method resolves the electrophoretic velocity of fluoro-spheres used as tracer particles in microPIV. This approach exploits the short transient regime of the EOF generated after a potential drop is imposed across a microchannel and before reaching quasisteady state. During the starting of the transient regime, the electrophoretic effect is dominant in the center of the channel and the EOF is negligible. By measuring the velocity of the tracer particles with a microPIV system during that starting period, their electrophoretic velocity is obtained. The technique also resolves the temporal evolution of the EOF with three regions identified. The first region occurs before the electroosmotic effect reaches the center of the channel, the second region extends until the EOF reaches steady state, and thereafter is the third region. The two time constants separating these regions are also obtained and compared to the theory. The zeta potential of 860 nm diameter polystyrene particles is calculated for different solutions including borate buffer, sodium chloride, and deionized water. Results show that the magnitudes of the electrophoretic and electroosmotic velocities are in the range of |300| to |700| µm/s for these measurements. The zeta potential values are compared to the well-established closed cell technique showing improved accuracy. The method also resolves the characteristic response time of the EOF, showing small but important deviations from current analytical predictions. Additionally, the measurements can be performed in situ in microfluidic devices under actual working EOF conditions and without the need for calibrations.
2017-04-20T08:07:22ZSureda Anfres, MiquelMiller, AndrewDiez, F. J.A time-resolved microPIV method is presented to measure in an EOF the particles zeta potential in situ during the transient start-up of a microdevice. The method resolves the electrophoretic velocity of fluoro-spheres used as tracer particles in microPIV. This approach exploits the short transient regime of the EOF generated after a potential drop is imposed across a microchannel and before reaching quasisteady state. During the starting of the transient regime, the electrophoretic effect is dominant in the center of the channel and the EOF is negligible. By measuring the velocity of the tracer particles with a microPIV system during that starting period, their electrophoretic velocity is obtained. The technique also resolves the temporal evolution of the EOF with three regions identified. The first region occurs before the electroosmotic effect reaches the center of the channel, the second region extends until the EOF reaches steady state, and thereafter is the third region. The two time constants separating these regions are also obtained and compared to the theory. The zeta potential of 860 nm diameter polystyrene particles is calculated for different solutions including borate buffer, sodium chloride, and deionized water. Results show that the magnitudes of the electrophoretic and electroosmotic velocities are in the range of |300| to |700| µm/s for these measurements. The zeta potential values are compared to the well-established closed cell technique showing improved accuracy. The method also resolves the characteristic response time of the EOF, showing small but important deviations from current analytical predictions. Additionally, the measurements can be performed in situ in microfluidic devices under actual working EOF conditions and without the need for calibrations.Research on fluidic amplifiers dimensional modifications via computer simulation (CFD)
http://hdl.handle.net/2117/103413
Research on fluidic amplifiers dimensional modifications via computer simulation (CFD)
Baghaei, Masoud; Bergadà Granyó, Josep Maria; Campo Sud, David del; Campo Gatell, Vanessa del
When studying active flow control applications, it is already stated that activating the boundary layer via using periodic flow produces better performance than when employing steady blowing or sucking. This is why studying the performance characteristics of devices like fluidic oscillators and zero net mass flow actuators is particularly interesting. In the present paper a particular configuration of fluidic oscillator is carefully analyzed, initially its dynamic performance is compared with experimental results undertaken by previous researchers, then the dimensional internal characteristics are modified in order to obtain how is the dynamic behavior being affected, in a third stage the evaluation of how fluidic oscillators scale is affecting its dynamic performance is also presented. Based on the results obtained it can be concluded that a given actuator working at a given Reynolds number, is capable of producing different frequencies and amplitudes when modifying some dimensional parameters.
2017-04-06T10:39:56ZBaghaei, MasoudBergadà Granyó, Josep MariaCampo Sud, David delCampo Gatell, Vanessa delWhen studying active flow control applications, it is already stated that activating the boundary layer via using periodic flow produces better performance than when employing steady blowing or sucking. This is why studying the performance characteristics of devices like fluidic oscillators and zero net mass flow actuators is particularly interesting. In the present paper a particular configuration of fluidic oscillator is carefully analyzed, initially its dynamic performance is compared with experimental results undertaken by previous researchers, then the dimensional internal characteristics are modified in order to obtain how is the dynamic behavior being affected, in a third stage the evaluation of how fluidic oscillators scale is affecting its dynamic performance is also presented. Based on the results obtained it can be concluded that a given actuator working at a given Reynolds number, is capable of producing different frequencies and amplitudes when modifying some dimensional parameters.Successes and challenges of a collaborative-PBL program in engineering degrees
http://hdl.handle.net/2117/97771
Successes and challenges of a collaborative-PBL program in engineering degrees
González Vila, Joaquin; Font Andreu, Jorge; Salán Ballesteros, Maria Núria; García-Almiñana, Daniel; Ortiz Marzo, José Antonio; Mudarra López, Miguel; Griful Ponsati, Eulàlia
This paper presents an extracurricular program called INSPIRE3 that has been implemented by the ETSEIAT (Escola Tècnica
Superior d’Enginyeries Industrial i Aeronàutica de Terrassa), a center belonging to the UPC-BarcelonaTech (Universitat
Politècnica de Catalunya). This program is mainly aimed at facilitating cross-curricular skills and developing abilities among
students through collaborative-project based learning. The projection of an attractive external image of engineering degrees
offered by ETSEIAT in order to increase the enrollment in such degrees is a secondary goal of this program. Under INSPIRE3,
several real, challenging and multidisciplinary engineering projects are currently under development. The main feature of this
program is that the subjects of the projects are proposed by the students themselves. In this paper, INSPIRE3 motivation,
program management and implementation process are described and a short description of projects under development is also
given.
Comunicació presentada a
2016-12-05T13:03:17ZGonzález Vila, JoaquinFont Andreu, JorgeSalán Ballesteros, Maria NúriaGarcía-Almiñana, DanielOrtiz Marzo, José AntonioMudarra López, MiguelGriful Ponsati, EulàliaThis paper presents an extracurricular program called INSPIRE3 that has been implemented by the ETSEIAT (Escola Tècnica
Superior d’Enginyeries Industrial i Aeronàutica de Terrassa), a center belonging to the UPC-BarcelonaTech (Universitat
Politècnica de Catalunya). This program is mainly aimed at facilitating cross-curricular skills and developing abilities among
students through collaborative-project based learning. The projection of an attractive external image of engineering degrees
offered by ETSEIAT in order to increase the enrollment in such degrees is a secondary goal of this program. Under INSPIRE3,
several real, challenging and multidisciplinary engineering projects are currently under development. The main feature of this
program is that the subjects of the projects are proposed by the students themselves. In this paper, INSPIRE3 motivation,
program management and implementation process are described and a short description of projects under development is also
given.Ram-air parachute simulation with panel methods and staggered coupling
http://hdl.handle.net/2117/91426
Ram-air parachute simulation with panel methods and staggered coupling
Ortega, Enrique; Flores Le Roux, Roberto Maurice; Pons Prats, Jordi
2016-11-03T13:43:42ZOrtega, EnriqueFlores Le Roux, Roberto MauricePons Prats, JordiReliability versus mass optimization of CO2 extraction technologies for long duration missions
http://hdl.handle.net/2117/89135
Reliability versus mass optimization of CO2 extraction technologies for long duration missions
Detrell Domingo, Gisela; Griful Ponsati, Eulàlia; Messerschmid, Ernst
The aim of this paper is to optimize reliability and mass of three CO2 extraction technologies/components: the 4-Bed Molecular Sieve, the Electrochemical Depolarized Concentrator and the Solid Amine Water Desorption. The first one is currently used in the International Space Station and the last two are being developed, and could be used for future long duration missions. This work is part of a complex study of the Environmental Control and Life Support System (ECLSS) reliability. The result of this paper is a methodology to analyze the reliability and mass at a component level, which is used in this paper for the CO2 extraction technologies, but that can be applied to the ECLSS technologies that perform other tasks, such as oxygen generation or water recycling, which will be a required input for the analysis of an entire ECLSS. The key parameter to evaluate any system to be used in space is mass, as it is directly related to the launch cost. Moreover, for long duration missions, reliability will play an even more important role, as no resupply or rescue mission is taken into consideration. Each technology is studied as a reparable system, where the number of spare parts to be taken for a specific mission will need to be selected, to maximize the reliability and minimize the mass of the system. The problem faced is a Multi-Objective Optimization Problem (MOOP), which does not have a single solution. Thus, optimum solutions of MOOP, the ones that cannot be improved in one of the two objectives, without degrading the other one, are found for each selected technology. The solutions of the MOOP for the three technologies are analyzed and compared, considering other parameters such as the type of mission, the maturity of the technology and potential interactions/synergies with other technologies of the ECLSS.
2016-07-25T10:43:03ZDetrell Domingo, GiselaGriful Ponsati, EulàliaMesserschmid, ErnstThe aim of this paper is to optimize reliability and mass of three CO2 extraction technologies/components: the 4-Bed Molecular Sieve, the Electrochemical Depolarized Concentrator and the Solid Amine Water Desorption. The first one is currently used in the International Space Station and the last two are being developed, and could be used for future long duration missions. This work is part of a complex study of the Environmental Control and Life Support System (ECLSS) reliability. The result of this paper is a methodology to analyze the reliability and mass at a component level, which is used in this paper for the CO2 extraction technologies, but that can be applied to the ECLSS technologies that perform other tasks, such as oxygen generation or water recycling, which will be a required input for the analysis of an entire ECLSS. The key parameter to evaluate any system to be used in space is mass, as it is directly related to the launch cost. Moreover, for long duration missions, reliability will play an even more important role, as no resupply or rescue mission is taken into consideration. Each technology is studied as a reparable system, where the number of spare parts to be taken for a specific mission will need to be selected, to maximize the reliability and minimize the mass of the system. The problem faced is a Multi-Objective Optimization Problem (MOOP), which does not have a single solution. Thus, optimum solutions of MOOP, the ones that cannot be improved in one of the two objectives, without degrading the other one, are found for each selected technology. The solutions of the MOOP for the three technologies are analyzed and compared, considering other parameters such as the type of mission, the maturity of the technology and potential interactions/synergies with other technologies of the ECLSS.Review of Lambert's problem
http://hdl.handle.net/2117/86429
Review of Lambert's problem
Torre Sangrà, David de la; Fantino, Elena
Lambert’s problem is the orbital boundary-value problem constrained by two points and elapsed time. It is one of the most extensively studied problems in celestial mechanics and astrodynamics, and, as such, it has always attracted the interest of mathematicians and engineers. Its solution lies at the base of algorithms for, e.g., orbit determination, orbit design (mission planning), space rendezvous and interception, space debris correlation, missile and spacecraft targeting. There is abundance of literature discussing various approaches developed over the years to solve Lambert’s problem. We have collected more than 70 papers and, of course, the issue is treated in most astrodynamics and celestial mechanics textbooks. From our analysis of the documents, we have been able to identify five or six main solution methods, each associated to a number of revisions and variations, and many, so to say, secondary research lines with little or no posterior development. We have ascertained plenty of literature with proposed solutions, in many cases supplemented by performance comparisons with other methods. We have reviewed and organized the existing bibliography on Lambert’s problem and we have performed a quantitative comparison among the existing methods for its solution. The analysis is based on the following issues: choice of the free parameter, number of iterations,generality of the mathematical formulation, limits of applicability (degeneracies, domain of the parameter, special cases and peculiarities), accuracy, and suitability to automatic execution. Eventually we have tested the performance of each code. The solvers that incorporate the best qualities are Bate’s algorithm via universal variables with Newton-Raphson and Izzo’s Householder algorithm. The former is the fastest, the latter exhibits the best ratio between speed, robustness and accuracy.
2016-04-29T13:51:49ZTorre Sangrà, David de laFantino, ElenaLambert’s problem is the orbital boundary-value problem constrained by two points and elapsed time. It is one of the most extensively studied problems in celestial mechanics and astrodynamics, and, as such, it has always attracted the interest of mathematicians and engineers. Its solution lies at the base of algorithms for, e.g., orbit determination, orbit design (mission planning), space rendezvous and interception, space debris correlation, missile and spacecraft targeting. There is abundance of literature discussing various approaches developed over the years to solve Lambert’s problem. We have collected more than 70 papers and, of course, the issue is treated in most astrodynamics and celestial mechanics textbooks. From our analysis of the documents, we have been able to identify five or six main solution methods, each associated to a number of revisions and variations, and many, so to say, secondary research lines with little or no posterior development. We have ascertained plenty of literature with proposed solutions, in many cases supplemented by performance comparisons with other methods. We have reviewed and organized the existing bibliography on Lambert’s problem and we have performed a quantitative comparison among the existing methods for its solution. The analysis is based on the following issues: choice of the free parameter, number of iterations,generality of the mathematical formulation, limits of applicability (degeneracies, domain of the parameter, special cases and peculiarities), accuracy, and suitability to automatic execution. Eventually we have tested the performance of each code. The solvers that incorporate the best qualities are Bate’s algorithm via universal variables with Newton-Raphson and Izzo’s Householder algorithm. The former is the fastest, the latter exhibits the best ratio between speed, robustness and accuracy.Analysis of perturbations and station-keeping requirements in highly-inclined geosynchronous orbits
http://hdl.handle.net/2117/86428
Analysis of perturbations and station-keeping requirements in highly-inclined geosynchronous orbits
Fantino, Elena; Flores Le Roux, Roberto Maurice; Di Salvo, Alessio; Di Carlo, Marilena
There is a demand for communications services at high latitudes that is not well served by conventional geostationary satellites. Alternatives using low-altitude orbits require too large constellations. Other options are the Molniya and Tundra families (critically-inclined, eccentric orbits with the apogee at high latitudes). In this work we have considered derivatives of the Tundra type with different inclinations and eccentricities. By means of a high-precision model of the terrestrial gravity field and the most relevant environmental perturbations, we have studied the evolution of these orbits during a period of two years. The effects of the different perturbations on the constellation ground track (which is more important for coverage than the orbital elements themselves) have been identified. We show that, in order to maintain the ground track unchanged, the most important parameters are the orbital period and the argument of the perigee. Very subtle changes in the orbital period (due mainly to lunar perturbations) cause a large east-west drift of the ground trace which dwarfs the displacement due to the regression of the ascending node. From these findings, a station-keeping strategy that minimizes propellant consumption has then been devised. Our results offer interesting guidelines for the design and operation of satellite constellations using these orbits.
2016-04-29T13:21:01ZFantino, ElenaFlores Le Roux, Roberto MauriceDi Salvo, AlessioDi Carlo, MarilenaThere is a demand for communications services at high latitudes that is not well served by conventional geostationary satellites. Alternatives using low-altitude orbits require too large constellations. Other options are the Molniya and Tundra families (critically-inclined, eccentric orbits with the apogee at high latitudes). In this work we have considered derivatives of the Tundra type with different inclinations and eccentricities. By means of a high-precision model of the terrestrial gravity field and the most relevant environmental perturbations, we have studied the evolution of these orbits during a period of two years. The effects of the different perturbations on the constellation ground track (which is more important for coverage than the orbital elements themselves) have been identified. We show that, in order to maintain the ground track unchanged, the most important parameters are the orbital period and the argument of the perigee. Very subtle changes in the orbital period (due mainly to lunar perturbations) cause a large east-west drift of the ground trace which dwarfs the displacement due to the regression of the ascending node. From these findings, a station-keeping strategy that minimizes propellant consumption has then been devised. Our results offer interesting guidelines for the design and operation of satellite constellations using these orbits.A meshless finite point method for three-dimensional analysis of compressible flow problems involving moving boundaries and adaptivity
http://hdl.handle.net/2117/86276
A meshless finite point method for three-dimensional analysis of compressible flow problems involving moving boundaries and adaptivity
Ortega, Enrique; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo; Flores Le Roux, Roberto Maurice
A finite point method for solving compressible flow problems involving moving boundaries and adaptivity is presented. The numerical methodology is based on an upwind-biased discretization of the Euler equations, written in arbitrary Lagrangian–Eulerian form and integrated in time by means of a dual-time steeping technique. In order to exploit the meshless potential of the method, a domain deformation approach based on the spring network analogy is implemented, and h-adaptivity is also employed in the computations. Typical movable boundary problems in transonic flow regime are solved to assess the performance of the proposed technique. In addition, an application to a fluid–structure interaction problem involving static aeroelasticity illustrates the capability of the method to deal with practical engineering analyses. The computational cost and multi-core performance of the proposed technique is also discussed through the examples provided.
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2016-04-27T14:59:20ZOrtega, EnriqueOñate Ibáñez de Navarra, EugenioIdelsohn Barg, Sergio RodolfoFlores Le Roux, Roberto MauriceA finite point method for solving compressible flow problems involving moving boundaries and adaptivity is presented. The numerical methodology is based on an upwind-biased discretization of the Euler equations, written in arbitrary Lagrangian–Eulerian form and integrated in time by means of a dual-time steeping technique. In order to exploit the meshless potential of the method, a domain deformation approach based on the spring network analogy is implemented, and h-adaptivity is also employed in the computations. Typical movable boundary problems in transonic flow regime are solved to assess the performance of the proposed technique. In addition, an application to a fluid–structure interaction problem involving static aeroelasticity illustrates the capability of the method to deal with practical engineering analyses. The computational cost and multi-core performance of the proposed technique is also discussed through the examples provided.