Modelling the squeeze flow in a deformed rectangular microchannel

Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.Rheinforce cork composites, previously named elsewhere as CorkSTFluidics [1], are sandwiches consis?ng of two microagglomerated cork pads embedding microfluidic paCerns that are filled with a shear thickening fluid (see Figure 1 (a)), whose mechanical performance under impact loads is determined by the microfluidic paCern and the rheological proper?es of the fluid [2]. From the experimental results it is impossible to decouple the fluid contribu?on from the solid contribu?on to the force?me response of the composite. In this work, we have developed a simple model of the fluid-flow dynamics that it is able to predict the fluid contribu?on in the energy dissipa?on of the Rheinforce cork composites under impact loads. To that end, we model the viscous flow inside a microchannel for a known displacement of the upper lid h(t, x), calcula?ng as a result the needed force to create that movement

Transition to turbulence in the bottom boundary layer under a solitary wave.

Se estudia la transición a la turbulencia en una capa límite oscilatoria.Se estudia la transición a la turbulencia en una capa límite oscilatoria.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Two-dimensional instability of smooth compressible vortices

International audienc

Theoretical parameters of trailing vortices versus aspect ratio of wing models

We perform 2D-PIV measurements to characterize trailing vortices in NACA0012 wing models for aspect ratios ranging between 1 and 2.5, and for chord-based Reynolds numbers from 7000 to 40000. Firstly, and regarding the influence of the Reynolds number, the increase of this dimensionless parameter generates a more concentrated and intense vortex, presenting, therefore, an increase in all its characteristic magnitudes: maximum azimuthal velocity and vorticity. Secondly, the greater the aspect ratio, the greater the vortex strength is observed. Thirdly, the radial location of the peak of the azimuthal velocity has a strong decay as the aspect ratio increases for Re=7000, but it changes its trend for Re=40000.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.. Ministerio de Economía y Competitividad (Spain) Grant No. DPI2013-40479-P and DPI2016-76151-C2-1-R and Junta de Andalucía Grant No. P11-TEP-7776

Stability analysis of flow structures in hovering using robotic experiments and flow visualizations

We investigate the kinematics and stability of hovering flight making use of a robotic experimental device that simulate the movement of insects or birds. We carried out this analysis based on the characterization of this movement with flow visualizations and particle image velocimetry -PIV-. First, we characterized the kinematics of the robotic device inside water. Therefore, it has been verified that the robotic experiments follow the desired input signal precisely. Second, we give qualitative and quantitative information from the experimental tests as a function of frequency and angular amplitude. The kinematics of the hovering flight produces vortices that are stable or unstable around the rigid flat plate, as well as one transient regime that has been also found between these two latter states. Finally, dimensional velocity field plus associated vorticity have been characterized in these flow regimes through PIV measurements, and we also validated the reproducibility of experiment finding excellent agreement between different set of experiments.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Nonlinear evolution of harmonically forced perturbations on a wingtip vortex

Wingtip vortices are created by flying airplanes due to lift generation. The vortex interaction with the trailing aircraft has sparked researchers’ interest to develop an efficient technique to destroy these vortices. Different models have been used to describe the vortex dynamics and they all show that, under real flight conditions, the most unstable modes produce a very weak amplification. Another linear instability mechanism that can produce high energy gains in short times is due to the non-normality of the system. Recently, it has been shown that these non-normal perturbations also produce this energy growth when they are excited with harmonic forcing functions. In this study, we analyze numerically the nonlinear evolution of a spatially, pointwise and temporally forced perturbation, generated by a synthetic jet at a given radial distance from the vortex core. This type of perturbation is able to produce high energy gains in the perturbed base flow (10^3), and is also a suitable candidate for use in engineering applications. The flow field is solved for using fully nonlinear three-dimensional direct numerical simulation with a spectral multidomain penalty method model. Our novel results show that the nonlinear effects are able to produce locally small bursts of instability that reduce the intensity of the primary vortex.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Wingtip vortex in a NACA0012 airfoil and its active control

Contribución mediante sesión pósterWe conduct experiments in a towing-tank to analyse the flow patterns of wingtip vortices in a NACA 0012 airfoil. In this experimental research, we provide PIV measurements and flow visualisations. Without active control, several parameters are given experimentally as function of the Reynolds number, so we compare these data with the theoretical models of Batchelor, and Moore and Saffman together with DNS. Secondly, we analyse the effect of a continuous injection in the spanwise direction. The continuous jet has a strong influence on the wing-tip vortex formation. We explore this effect at low chord based Reynolds number ranging from 7000 up to 20000. We change the aspect ratio of the injection, R, defined as the ratio of the velocities between the jet (Uj) and free-stream (U). For R=1, we find that the jet strongly affects the wingtip vortex formation with a sudden decrement of the axial vorticity and the azimuthal velocity. This technique is a challenge and a promising tool to reduce the intensity of the vortex core.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Effect of the axial jet on the optimal response in Batchelor vortex

En este póster se estudia la respuesta óptima del torbellino de Batchelor para distintos números de onda. Se demuestra que incluso teniendo la velocidad axial, un torbellino es capaz de tener grandes amplificaciones de energía.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech