DBIAB - AERO - EP2 - Journal Articleshttp://hdl.handle.net/10016/276332019-09-20T12:50:07Z2019-09-20T12:50:07ZAssessment of experimental optical techniques for characterizing heat transfer using numerical simulationsJuste, G.L.Fajardo Peña, Pablohttp://hdl.handle.net/10016/288432019-09-20T00:02:37Z2015-02-25T00:00:00ZAssessment of experimental optical techniques for characterizing heat transfer using numerical simulations
Juste, G.L.; Fajardo Peña, Pablo
This manuscript addresses the application of numerical simulations for assessing the error in the measurement of the bulk temperature along the laser beam of a 3D flow using a 2D Moire deflectometry analysis. To analyze the effect of different flow parameters on the error, a 3D computational model of an experimental system was developed. The simulated domain represents the well-known solution of the backward facing step in a rectangular channel but includes a hot-plate at the bottom of the step to enhance the heat transfer effects. The geometry resembles that found in a general heat exchanger. The difference between the computed bulk temperature of the flow and the average temperature obtained via the 2D Moire is analytically evaluated for various assumed general temperature profiles; the numerically computed profiles of temperature indicates that the error decreases with the channel aspect ratio. The use of CFD enables the determination of the flow topology and thus an evaluation of the 3D flow behavior that will cause the measurement error. A parametric study was performed for different flow conditions, namely, the aspect ratio of the channel, the inflow conditions (flow velocity or Reynolds number), and the temperature of the hot wall. The results indicate that the Moire technique is suitable for evaluating the bulk temperature in typical heat exchange devices and flow conditions.
2015-02-25T00:00:00ZPlasma detachment in a propulsive magnetic nozzle via ion demagnetizationMerino Martínez, MarioAhedo Galilea, Eduardo Antoniohttp://hdl.handle.net/10016/288262019-09-20T12:36:10Z2014-05-19T00:00:00ZPlasma detachment in a propulsive magnetic nozzle via ion demagnetization
Merino Martínez, Mario; Ahedo Galilea, Eduardo Antonio
Plasma detachment in propulsive magnetic nozzles is shown to be a robust phenomenon caused by the inability of the internal electric fields to bend most of the supersonic ions along the magnetic streamtubes. As a result, the plasma momentum is effectively ejected to produce thrust, and only a marginal fraction of the beam mass flows back. Detachment takes place even if quasineutrality holds everywhere and electrons are fully magnetized, and is intimately linked to the formation of local electric currents. The divergence angle of the 95%-mass flow tube is used as a quantitative detachment performance figure.
2014-05-19T00:00:00ZDevelopment and validation of a radial variable geometry turbine model for transient pulsating flow applicationsGalindo, J.Tiseira, A.Fajardo Peña, PabloGarcia-Cuevas, L. M.http://hdl.handle.net/10016/288202019-09-17T00:02:39Z2014-09-01T00:00:00ZDevelopment and validation of a radial variable geometry turbine model for transient pulsating flow applications
Galindo, J.; Tiseira, A.; Fajardo Peña, Pablo; Garcia-Cuevas, L. M.
This paper presents the development and validation of a one-dimensional radial turbine model able to be used in automotive turbocharger simulations. The model has been validated using results from a numerical 3D CFD simulation of stationary and pulsating flow in a variable geometry radial turbine. As the CFD analysis showed, the main non-quasi-steady behavior of the turbine is due to the volute geometry, so special care was taken in order to properly model it while maintaining low computational costs. The flow in the volute has been decomposed in its radial and azimuthal direction. The azimuthal flow corresponds to the flow moving along the volute, while the radial flow is computed by coupling its flow with a stator model. Although the stator caused fewer accumulation effects than the volute, a small accumulation model has been used for it, which also allows to compute the evolution of the flow inside the turbine with lower costs. The flow in the moving rotor can be considered quasi-steady, so a zero-dimensional model for the rotor has been developed. Several losses models where implemented for both the stator and the rotor. The results show good agreement with the CFD computations.
2014-09-01T00:00:00ZElectron cooling and finite potential drop in a magnetized plasma expansionMartínez Sánchez, ManuelNavarro Cavallé, JaumeAhedo Galilea, Eduardo Antoniohttp://hdl.handle.net/10016/288092019-09-14T00:02:37Z2015-05-05T00:00:00ZElectron cooling and finite potential drop in a magnetized plasma expansion
Martínez Sánchez, Manuel; Navarro Cavallé, Jaume; Ahedo Galilea, Eduardo Antonio
The steady, collisionless, slender flow of a magnetized plasma into a surrounding vacuum is considered. The ion component is modeled as mono-energetic, while electrons are assumed Maxwellian upstream. The magnetic field has a convergent-divergent geometry, and attention is restricted to its paraxial region, so that 2D and drift effects are ignored. By using the conservation of energy and magnetic moment of particles and the quasi-neutrality condition, the ambipolar electric field and the distribution functions of both species are calculated self-consistently, paying attention to the existence of effective potential barriers associated to magnetic mirroring. The solution is used to find the total potential drop for a set of upstream conditions, plus the axial evolution of various moments of interest (density, temperatures, and heat fluxes). The results illuminate the behavior of magnetic nozzles, plasma jets, and other configurations of interest, showing, in particular, in the divergent plasma the collisionless cooling of electrons, and the generation of collisionless electron heat fluxes.
2015-05-05T00:00:00Z