Archivo Digital UPM: No conditions. Results ordered -Date Deposited. 2022-12-10T00:09:16ZEPrintshttps://oa.upm.es/style/images/logo-archivo-digital.pnghttps://oa.upm.es/2022-03-02T16:18:39Z2022-03-02T16:18:39Zhttps://oa.upm.es/id/eprint/67041This item is in the repository with the URL: https://oa.upm.es/id/eprint/670412022-03-02T16:18:39ZMotivational impact of active learning methods in aerospace engineering studentsMotivation is a critical factor in academic performance. In the case of aerospace engineering education, it is particularly necessary due to the difficulty of the subject, so it is essential to use reliable instruments to allow aerospace engineering teachers to understand how their students' motivation works. Moreover, it is important to identify educational techniques that enhance the motivation of aerospace engineering students and help them to persevere through a challenging workload. In this contribution, the motivation of students of the Master of Aerospace Engineering degree of the Universidad Politécnica de Madrid is analyzed in two subjects that use different educational techniques. A teaching centered approach is applied in one subject, while active learning methods like Project Based Learning are applied in the other. In this second approach, students are required to perform a preliminary design of a Space Mission starting from Mission requirements and must integrate the subsystems of a microsatellite using demonstration satellites. A reliable instrument tailored for engineering students has been used during two academic years to evaluate the impact of these techniques on the students’ motivation. The empirical experience described here confirms the positive impact of active learning methods and indicates the key factors, both intrinsic and extrinsic, in the motivation of aerospace engineering students.Daniel López FernándezJose Miguel Ezquerro NavarroJacobo Rodriguez OteroJeffrey Brent PorterMaria Victoria Lapuerta Gonzalez2021-10-13T08:10:17Z2021-10-13T08:10:17Zhttps://oa.upm.es/id/eprint/67085This item is in the repository with the URL: https://oa.upm.es/id/eprint/670852021-10-13T08:10:17ZVibroequilibria in microgravity: Comparison of experiments and theoryExperiments on vibrated fluids confined in cylindrical and cuboidal containers were performed under the reduced gravity conditions of a parabolic flight. The results constitute a systematic quantitative investigation of the vibroequilibria effect, which refers to the reorientation of vibrated fluids in response to the inhomogeneous oscillatory velocity field and the accompanying dynamic pressure. This effect is amplified in microgravity where the restoring force of gravity is small or absent. Here the vibrations are transmitted via a pair of piezoelectric ceramics and a cantilever beam, excited in a resonant mode. The first and second resonances exhibit different types of motion and lead to different types of vibroequilibria surfaces, one with a dip or crater in the interior and the other flattened compared to the unforced reference experiment. The general tendency for interfaces to orient more perpendicular, on average, to the vibrational axis is confirmed. In the case of water in a cuboidal container, a quantitative comparison is made with vibroequilibria theory and with direct simulations of the Navier-Stokes equations. The good agreement confirms the predictions of vibroequilibria theory and suggests the capacity of this phenomenon to manipulate and position fluids in space environments through the choice of frequency and resonant mode.Pablo Salgado SanchezJose Javier Fernandez FraileIgnacio Tinao Perez-MiraveteJeffrey Brent Porter2021-06-11T05:04:07Z2021-06-11T05:04:07Zhttps://oa.upm.es/id/eprint/67229This item is in the repository with the URL: https://oa.upm.es/id/eprint/672292021-06-11T05:04:07ZSimulating vibrated fluids and vibroequilibria in the CFVib microgravity experimentThe CFVib experiment investigated the use of piezoelectric actuators to manipulate fluids via the vibroequilibria effect. A model is developed to simulate fluid behaviour in this experiment, including interaction with the container and piezoelectrics. Since vibroequilibria evolve slowly compared to the applied forcing, a separation of timescales is used to obtain a linear problem on the fast timescale whose solution provides a quasisteady source term driving slow vibroequilibria dynamics. We find that the surface adopts different vibroequilibria depending on the selected mode of vibration. Simulations show good agreement with experiments and suggest a potential strategy for manipulating fluids in weightlessness.Pablo Salgado SanchezJose Javier Fernandez FraileIgnacio Tinao Perez-MiraveteJeffrey Brent PorterAlvaro Bello Garcia2021-06-10T09:38:53Z2021-06-10T09:38:53Zhttps://oa.upm.es/id/eprint/67234This item is in the repository with the URL: https://oa.upm.es/id/eprint/672342021-06-10T09:38:53ZVibrational instabilities at the interface separating two immiscible liquids in microgravityA wide variety of interfacial phenomena occurs in vibrated fluid systems, depending on frequency, amplitude and forcing orientation. On earth, there is a clear qualitative difference between vertical and horizontal vibrations. Vertical vibrations can be understood as a modulation of effective gravity and may be stabilizing, as with the Rayleigh-Taylor instability (Wolf 1970), or destabilizing, as with the phenomenon of Faraday waves (Faraday 1831). Horizontal forcing, on the other hand, immediately excites harmonic waves near the container boundaries. When a critical amplitude is reached, it also excites subharmonic cross-waves (Garret, 1970). If the interface separates immiscible layers of different viscosity, vibrations can lead to frozen waves (Lyubimov, Cherepanov 1986; Talib et al. 2007), which are generally bounded by the restoring effects of gravity and interfacial tension.Pablo Salgado SanchezV. YasnouY. GaponenkoA. MialdunJeffrey Brent PorterV. Shevtsova2021-06-02T08:24:55Z2021-06-02T08:24:55Zhttps://oa.upm.es/id/eprint/67019This item is in the repository with the URL: https://oa.upm.es/id/eprint/670192021-06-02T08:24:55ZInterfacial phenomena in immiscible liquids subjected to vibrations in microgravityWe consider the response to periodic forcing between 5 Hz and 50 Hz of an interface separating immiscible fluids under the microgravity conditions of a parabolic flight. Two pairs of liquids with viscosity ratios differing by one order of magnitude are investigated. By combining experimental data with numerical simulations, we describe a variety of dynamics including harmonic and subharmonic (Faraday) waves, frozen waves and drop ejection, determining their thresholds and scaling properties when possible. Interaction between these various modes is facilitated in microgravity by the relative ease with which the interface can move, altering its orientation with respect to the forcing axis. The effects of key factors controlling pattern selection are analysed, including vibrational forcing, viscosity ratio, finite-size effects and residual gravity. Complex behaviour often arises with features on several spatial scales, such as Faraday waves excited on the interface of a larger columnar structure that develops due to the frozen wave instability – this type of state was previously seen in miscible fluid experiments but is described for the first time here in the immiscible case.Pablo Salgado SanchezV. YasnouY. GaponenkoA. MialdunJeffrey Brent PorterV. Shevtsova2019-04-03T10:45:17Z2019-04-03T10:45:17Zhttps://oa.upm.es/id/eprint/53508This item is in the repository with the URL: https://oa.upm.es/id/eprint/535082019-04-03T10:45:17ZThe CFVib Experiment: control of fluids in microgravity with vibrationsThe Control of Fluids in Microgravity with Vibrations (CFVib) experiment was selected for the 2016 Fly Your Thesis! programme as part of the 65th ESA Parabolic Flight Campaign. The aim of the project is to observe the potentially complex behaviour of vibrated liquids in weightless environments and to investigate the extent to which small-amplitude vibrations can be used to influence and control this behaviour. Piezoelectric materials are used to generate high-frequency vibrations to drive surface waves and large-scale reorientation of the interface. The theory of vibroequilibria, which treats the quasi-stationary surface configurations achieved by this reorientation, was used to predict interesting parameter regimes and interpret fluid behaviour. Here we describe the scientific motivation, objectives, and design of the experiment.Jose Javier Fernandez FrailePablo Salgado SanchezIgnacio Tinao Perez-miraveteJeffrey Brent PorterJose Miguel Ezquerro Navarro2019-03-26T13:03:29Z2019-03-26T13:03:29Zhttps://oa.upm.es/id/eprint/53493This item is in the repository with the URL: https://oa.upm.es/id/eprint/534932019-03-26T13:03:29ZPattern selection in a horizontally vibrated containerWe present results of an experimental and numerical investigation of the patterns realized by surface waves within an open rectangular container subjected to horizontal vibrations at frequencies of 40?100 Hz. The first instability exhibited by the primary harmonic wave field is subharmonic, and may be identified with the cross-wave instability often seen in wave tank experiments. We show that, contrary to common theoretical and experimental assumptions, and despite their name, these subharmonic waves are not oriented crosswise, but at an intermediate angle with respect to the axis of vibration. Hence, the pattern selection problem for horizontally forced Faraday waves is more complex than has previously been assumed. We establish the robustness of this obliquely oriented surface wave pattern by varying the forcing frequency and amplitude, the fluid viscosity, the fluid depth, and the boundary conditions. Previous work on cross-waves is reviewed and discussed in relation to the current results. Finally, numerical simulations using a reduced model with an appropriate forcing term are used to support the generality of the experimental observations.Jeffrey Brent PorterIgnacio Tinao Perez-MiraveteAna Laveron SimavillaCarlos A. Lopez2019-03-13T11:19:14Z2019-03-13T11:19:14Zhttps://oa.upm.es/id/eprint/53466This item is in the repository with the URL: https://oa.upm.es/id/eprint/534662019-03-13T11:19:14ZHeteroclinic dynamics in the parametrically driven nonlocal Schrödinger equationFaraday waves are described, under appropriate conditions, by a damped nonlocal parametrically driven nonlinear Schrödinger equation. As the strength of the applied forcing increases this equation undergoes a sequence of transitions to chaotic dynamics. The origin of these transitions is explained using a careful study of a two-mode Galerkin truncation and linked to the presence of heteroclinic connections between the trivial state and spatially periodic standing waves. These connections are associated with cascades of gluing and symmetry-switching bifurcations; such bifurcations are located in the partial differential equations as well.Maria Jesus Higuera TorronJeffrey Brent PorterEdgar Knobloch2019-02-20T08:45:34Z2019-02-20T08:45:34Zhttps://oa.upm.es/id/eprint/53468This item is in the repository with the URL: https://oa.upm.es/id/eprint/534682019-02-20T08:45:34ZFaraday waves, streaming flow, and relaxation oscillations in nearly circular containersFaraday waves near onset in an elliptical container are described by a third-order system of ordinary differential equations with characteristic slow-fast structure. These equations describe the interaction of standing waves with a weakly damped streaming flow driven by Reynolds stresses in boundary layers at the free surface and the rigid walls, and capture the proliferation with decreasing damping of periodic and nonperiodic relaxation oscillations observed near onset in previous simulations. These structures are the result of slow drift through symmetry-related Hopf bifurcations.Maria Jesus Higuera TorronJeffrey Brent PorterEdgar Knobloch2019-02-19T12:55:49Z2019-02-19T12:55:49Zhttps://oa.upm.es/id/eprint/53492This item is in the repository with the URL: https://oa.upm.es/id/eprint/534922019-02-19T12:55:49ZOnset patterns in a simple model of localized parametric forcingWe investigate pattern selection at onset in a parametrically and inhomogeneously forced partial differential equation obtained by generalizing Mathieu's equation to include spatial interactions. No separation of scales is assumed. The proposed model is directly relevant to the case of parametrically forced surface waves, such as cross-waves, excited by the horizontal vibration of a fluid, where the forcing is localized to a finite region near the endwall or wavemaker. The availability of analytical solutions in the limit of piecewise constant forcing allows us investigate in detail the dependence of selected eigenfunctions on spatial detuning, forcing width, damping, boundary conditions, and container size. A wide range of onset patterns are located and described, many of which are rotated, modulated, or both, and deviate far from simple crosswise oriented standing waves. The linear selection mechanisms governing this multiplicity of potential onset patterns are discussed.Jeffrey Brent PorterI. TinaoAna Laverón SimavillaJ. Rodríguez2019-02-19T12:28:11Z2019-02-19T12:28:11Zhttps://oa.upm.es/id/eprint/53484This item is in the repository with the URL: https://oa.upm.es/id/eprint/534842019-02-19T12:28:11ZCross-waves excited by distributed forcing in the gravity-capillary regimeCross-wave descriptions based on a boundary forced nonlinear Schrodinger equation, which have been widely used since Jones [J. Fluid Mech. 138, 53?74 (1984)], rely on the assumption that modulations occur on a slow lengthscale compared with the extent of the forcing. This assumption does not hold for recent higher frequency (large aspect ratio) experiments. We extend the established theory of modulated cross-waves in horizontally vibrated containers by including surface tension and, most importantly, a spatially extended forcing term. The resulting amplitude equations provide predictions for onset values, spatial profiles, and temporal modulations that are compared with previous theory and with experimental measurements. The appearance of temporally modulated solutions, confirmed experimentally, is interpreted as the result of weak symmetry-breaking related to the interaction of waves generated at opposite ends.I. TinaoJeffrey Brent PorterAna Laverón SimavillaJ. Fernández2019-02-19T11:22:58Z2019-02-19T11:22:58Zhttps://oa.upm.es/id/eprint/53485This item is in the repository with the URL: https://oa.upm.es/id/eprint/534852019-02-19T11:22:58ZNonlinear dynamics of confined liquid systems with interfaces subject to forced vibrationsA review is presented of the dynamic behavior of confined fluid systems with interfaces under monochromatic mechanical forcing, emphasizing the associated spatio-temporal structure of the fluid response. At low viscosity, vibrations significantly affect dynamics and always produce viscous mean flows, which are coupled to the primary oscillating flow and evolve on a very slow timescale. Thus, unlike the primary oscillating flow, mean flows may easily interact with the surface rheology, which generates dynamics that usually exhibit a much slower timescale than that of typical gravity?capillary waves. The review is made with an eye to the typical experimental devices used to measure surface properties, which usually consist of periodically forced, symmetric fluid systems with interfaces. The current theoretical description of these systems ignores the fluid mechanics, which could play a larger role than presently assumed.María HigueraJeffrey Brent PorterFernando VarasJ. Vega2019-02-11T11:42:38Z2019-02-11T11:42:38Zhttps://oa.upm.es/id/eprint/53467This item is in the repository with the URL: https://oa.upm.es/id/eprint/534672019-02-11T11:42:38ZScaling properties of weakly nonlinear coefficients in the Faraday problemInteresting and exotic surface wave patterns have regularly been observed in the Faraday experiment. Although symmetry arguments provide a qualitative explanation for the selection of some of these patterns (e.g., superlattices), quantitative analysis is hindered by mathematical difficulties inherent in a time-dependent, free-boundary Navier-Stokes problem. More tractable low viscosity approximations are available, but these do not necessarily capture the moderate viscosity regime of the most interesting experiments. Here we focus on weakly nonlinear behavior and compare the scaling results derived from symmetry arguments in the low viscosity limit with the computed coefficients of appropriate amplitude equations using both the full Navier-Stokes equations and a reduced set of partial differential equations due to Zhang and Vinãls. We find the range of viscosities over which one can expect ?low viscosity? theories to hold. We also find that there is an optimal viscosity range for locating superlattice patterns experimentally?large enough that the region of parameters giving stable patterns is not impracticably small, yet not so large that crucial resonance effects are washed out. These results help explain some of the discrepancies between theory and experiment.Anne C. SkeldonJeffrey Brent Porter2019-02-11T09:03:42Z2019-02-11T09:03:42Zhttps://oa.upm.es/id/eprint/53509This item is in the repository with the URL: https://oa.upm.es/id/eprint/535092019-02-11T09:03:42ZDynamics of weakly coupled parametrically forced oscillatorsThe dynamics of two weakly coupled parametric oscillators are studied in the neighborhood of the primary subharmonic instability. The nature of both primary and secondary instabilities depends in a critical way on the permutation symmetries, if any, that remain after coupling is considered, and this depends on the relative phases of the parametric forcing terms. Detailed bifurcation sets, revealing a complex series of transitions organized in part by Bogdanov-Takens points, are calculated for representative sets of parameters. In the particular case of out-of-phase forcing the predictions of the coupled oscillator model are compared with direct numerical simulations and with recent experiments on modulated cross waves. Both the initial Hopf bifurcation and the subsequent saddle-node heteroclinic bifurcation are confirmed.P. Salgado SánchezJeffrey Brent PorterI. TinaoAna Laveron Simavilla2019-02-04T13:22:02Z2019-02-04T13:22:02Zhttps://oa.upm.es/id/eprint/53495This item is in the repository with the URL: https://oa.upm.es/id/eprint/534952019-02-04T13:22:02ZGlobal error analysis of two-dimensional panel methods for dirichlet formulationA rigorous analytical study of the global error of panel methods is presented. The analysis is performed for a wide variety of body shapes and different panel geometries to fully understand their effect on the convergence of the method. In particular, we study the global error associated with panel methods applied to thin or thick bodies with purely convex parts or with both convex and concave parts, and with smooth or non-smooth boundaries. Most previous studies focused on the analysis of local error, considering only the influence of the nearest panels and excluding the rest. The difference is shown to be appreciable in many configurations. Generally, there is a lack of consensus concerning the order of magnitude of the error for panel methods even in the simplest case with flat panels and a constant distribution of doublets along them. This paper clarifies apparently different or inconsistent results obtained by other authors.Jose Miguel Ezquerro NavarroAna Laveron SimavillaMaria Victoria Lapuerta GonzalezJeffrey Brent Porter2019-02-04T12:43:26Z2019-04-23T13:38:21Zhttps://oa.upm.es/id/eprint/53496This item is in the repository with the URL: https://oa.upm.es/id/eprint/534962019-02-04T12:43:26ZInstabilities of vibroequilibria in rectangular containersVibroequilibria theory, based on minimizing an averaged energy functional, predicts the quasi-equilibrium shape that a fluid volume will take when subjected to high-frequency vibrations. Here we present a detailed comparison of the predictions of vibroequilibria theory with the results of direct numerical simulations in horizontally vibrated rectangular containers, finding very good agreement over a range of parameters. The calculations also reveal an important difference in the behavior between small and large fluid volumes. With dimensionless volume larger than about 0.36, the symmetric vibroequilibria solution suffers a saddle-node instability prior to contact with the container bottom. This saddle-node bifurcation is analyzed using a simplified family of surfaces and shown to persist when gravity is included. Finally, an investigation of dynamic effects is presented, where a strong correlation is found between modulated subharmonic surface waves and the first odd sloshing mode. At large enough amplitude, this sloshing destroys the underlying vibroequilibria state and thus represents a possible instability for vibroequilibria in low viscosity fluids.Jose Javier Fernandez FraileIgnacio Tinao Perez-MiraveteJeffrey Brent PorterAna Laveron Simavilla