Electroactive morphing for the aerodynamic performance improvement of next generation airvehicles

The need to improve the aerodynamic performance of air vehicles is the origin of intense research on the real-time optimization of the airfoil shape. This real-time optimization can only be achieved by morphing the airfoil using adequate materials and actuators. The object of this thesis is to study smart-material actuators for aerodynamic performance optimization on different time scales (low-frequent and high-frequent actuation). First, the effects of the distinct actuation types, low-frequency large-displacement shape-memory alloy (SMA) and high-frequency low-displacement piezoelectric, on the surrounding flow are analyzed separately using dedicated time-resolved particle image velocimetry (TR-PIV) measurements. The experiments showed the deformation capacity of the SMA technology under realistic aerodynamic loads. Furthermore, it was highlighted that despite the limited actuation frequency the “quasi-static” hypothesis has to be carefully adapted for the Reynolds number range of 200.000. The PIV measurements conducted behind the piezoelectrically actuated trailing edge showed the capacity of the actuator to reduce the shear-layer instability modes. An open-loop optimum actuation frequency of 60 Hz has been identified. Secondly, a hybridization of the two previously studied technologies has been proposed. The implied actuators, SMAs and macro fiber composites (MFCs), have been modelled and the combined actuation capacity has been demonstrated. The designed prototype NACA4412 airfoil has been tested in the S4 wind-tunnel of IMFT and it was shown that the combination of the two technologies allows acting on the shear-layer vortices as well as control the lift

NLO Corrections and Parton Shower Effects on Electroweak Higgs Production in Association with Two Jets

Nach dem großen Erfolg, den die Entdeckung des Higgs-Bosons im Jahr 2012 für die Teilchenphysik darstellte, konzentriert sich die Forschung in diesem Fachgebiet mittlerweile darauf, das Standardmodell der Teilchenphysik mit höchster Präzision zu testen. Dahinter steht unter anderem die Hoffnung, Aussagen darüber treffen zu können, ob das Standardmodell tatsächlich als die fundamentale Theorie der Teilchenphysik anzusehen ist oder ob ihm eine umfassendere Theorie zugrunde liegt, die auch neue Physik jenseits dieses Modells beschreibt. Besonderer Fokus liegt in der aktuellen Forschung auf den verschiedenen Produktionsprozessen des Higgs-Bosons. Im Rahmen dieser Dissertation wird einer dieser Prozesse untersucht, namentlich die elektroschwache Produktion des Higgs-Bosons in Assoziation mit zwei harten Jets. Dieser Prozess zeichnet sich einerseits durch seine klare experimentelle Signatur aus und gilt andererseits als besonders sensitiv gegenüber den Effekten neuer Physik. Zentraler Bestandteil der Untersuchung in dieser Dissertation ist eine Rechnung, die Korrekturen in der nächstführenden Ordnung sowohl der starken, als auch der elektroschwachen Kopplung berücksichtigen kann. Diese Rechnung wird als Nutzerprozess im frei verfügbaren Programm POWHEG BOX RES implementiert. Durch den POWHEG-Formalismus wird eine Verknüpfung der Matrixelemente für den harten Streuprozess mit einem sogenannten Partonschauer ermöglicht, welcher die Berechnung von exklusiven Observablen erlaubt, die besonders für den Vergleich mit experimentellen Analysen große Relevanz besitzen. Die in dieser Arbeit präsentierte Implementierung stellt in Bezug auf den wichtigen Subprozess der Vektorbosonfusion (VBF) die erste frei verfügbare Rechnung in nächstführender Ordnung der elektroschwachen Kopplung dar, die mit einem QED-Schauer kombiniert werden kann. Gleichzeitig verzichten wir auf die weit verbreitete “VBF-Näherung”, in der nur dieser Subprozess betrachtet wird und der Subprozess der Higgsstrahlung vernachlässigt wird. Der Verzicht auf diese Näherung erlaubt es uns, Vorhersagen in einem deutlich weiter gefassten Bereich des Phasenraums mit hoher Präzision zu treffen. Unsere neue Implementierung ermöglicht es, praktisch beliebige kinematische Verteilungen des Prozesses zu generieren. Beispielhaft werden in dieser Arbeit einige dieser Verteilungen präsentiert und diskutiert. Dabei zeigt sich, dass wir in der Lage sind, bekannte Ergebnisse in nächstführender Ordnung der starken Kopplung und mit Partonschauer zu reproduzieren. Darüber hinaus unterstreichen die Ergebnisse die Wichtigkeit der Korrekturen in der nächstführenden Ordnung der elektroschwachen Kopplung, während sich Effekte durch einen QED-Schauer als vergleichsweise gering herausstellen.While every particle predicted by the Standard Model of particle physics has been observed since the Higgs boson was finally discovered in 2012, researchers in the field continue to test the predictions by this very successful theory with enormous precision. Their hope is to be able to determine whether the Standard Model is actually the fundamental theory of the elementary particles, or whether it is part of a more comprehensive theory. Since its discovery, the properties of the Higgs boson and its various production channels have drawn special attention in the scientific community. This thesis focusses on one of these production modes, namely the electroweak production of a Higgs boson in association with two hard jets. This process is known for its high signal-to-background ratio and is expected to be particularly sensitive to the effects of new physics beyond the Standard Model. We present an implementation of this process in the publicly available framework of the POWHEG BOX RES. This implementation includes corrections at the next-to-leading order of both the strong as well as the electroweak coupling and can be matched to a so-called parton shower, therefore allowing for the calculation of exclusive distributions that can be compared to experimental results. Regarding the sub-process of vector boson fusion (VBF), we present the first calculation that allows for the matching of a parton shower with a precision calculation at the next-to leading order of the electroweak coupling. Furthermore, we do not rely on the widely used VBF approximation, which neglects contributions corresponding to the sub-process of Higgsstrahlung. We are thus able to perform precision calculations in a significantly larger part of the phase space than previous implementations in the POWHEG framework that were limited to the VBF approximation. Using our new implementation, one can calculate arbitrary kinematic distributions of the final state particles. In this thesis, this is demonstrated by a phenomenological study featuring selected important distributions. We thereby not only confirm the ability of our code to reproduce existing results at the next-to-leading order of the strong coupling, but we are also able to show the importance of corrections at next-to-leading order of the electroweak coupling. In contrast, the influence of a QED shower turns out to have only a mild influence

On the multidisciplinary control and sensing of a smart hybrid morphing wing

Morphing wing technology is of great interest for improving the aerodynamic performance of future aircraft. A morphing wing prototype using both surface embedded Shape Memory Alloys (SMA) and piezoelectric macro fiber composite (MFC) actuators has been designed for wind tunnel experiments. This smart wing is a mechatronic system that contains embedded sensors to measure the surrounding flow and control the actuators. This article will focus on the control of the cambering system which is achieved using a group of nested control loops as well as on the perspective of a novel control strategy using in-situ temperature measurements. It will be shown that by exploiting the inherent hysteretic properties of the SMAs cambering a significant reduction in power consumption is possible by appropriately tailoring the control strategy. Furthermore, by comparing the post-processed pressure signals recorded during the wind tunnel experiments to the aerodynamic performance gains a perspective for a novel in-situ control will be shown

Parton-shower effects in Higgs production via Vector-Boson Fusion

We present a systematic investigation of parton-shower and matching perturbative uncertainties for Higgs-boson production via vector-boson fusion. To this end we employ different generators at next-to-leading order QCD accuracy matched with shower Monte Carlo programs, PYTHIA8, and HERWIG7, and a next-to-next-to-leading order QCD calculation. We thoroughly analyse the intrinsic sources of uncertainty within each generator, and then compare predictions among the different tools using the respective recommended setups. Within typical vector-boson fusion cuts, the resulting uncertainties on observables that are accurate to next-to-leading order are at the 10% level for rates and even smaller for shapes. For observables sensitive to extra radiation effects uncertainties of about 20% are found. We furthermore show how a specific recoil scheme is needed when PYTHIA8 is employed, in order not to encounter unphysical enhancements for these observables. We conclude that for vector-boson fusion processes an assessment of the uncertainties associated with simulation at next-to-leading order matched to parton showers based only on the variation of renormalisation, factorisation and shower scales systematically underestimates their true size.Comment: v2 matches the version published on EPJ

Implementation of a hybrid electro-active actuated morphing wing in wind tunnel

Amongst current aircraft research topics, morphing wing is of great interest for improving the aerodynamic performance. A morphing wing prototype has been designed for wind tunnel experiments. The rear part of the wing - corresponding to the retracted flap - is actuated via a hybrid actuation system using both low frequency camber control and a high frequency vibrating trailing edge. The camber is modified via surface embedded shape memory alloys. The trailing edge vibrates thanks to piezoelectric macro-fiber composites. The actuated camber, amplitude and frequency ranges are characterized. To accurately control the camber, six independent shape memory alloy wires are controlled through nested closed-loops. A significant reduction in power consumption is possible via this control strategy. The effects on flow via morphing have been measured during wind tunnel experiments. This low scale mock-up aims to demonstrate the hybrid morphing concept, according to actuator capabilities point of view as well as aerodynamic performance

Prednisolone as preservation additive prevents from ischemia reperfusion injury in a rat model of orthotopic lung transplantation

The lung is, more than other solid organs, susceptible for ischemia reperfusion injury after orthotopic transplantation. Corticosteroids are known to potently suppress pro-inflammatory processes when given in the post-operative setting or during rejection episodes. Whereas their use has been approved for these clinical indications, there is no study investigating its potential as a preservation additive in preventing vascular damage already in the phase of ischemia. To investigate these effects we performed orthotopic lung transplantations (LTX) in the rat. Prednisolone was either added to the perfusion solution for lung preservation or omitted and rats were followed for 48 hours after LTX. Prednisolone preconditioning significantly increased survival and diminished reperfusion edema. Hypoxia induced vasoactive cytokines such as VEGF were reduced. Markers of leukocyte invasiveness like matrix metalloprotease (MMP)-2, or common pro-inflammatory molecules like the CXCR4 receptor or the chemokine (C-C motif) ligand (CCL)-2 were downregulated by prednisolone. Neutrophil recruitment to the grafts was only increased in Perfadex treated lungs. Together with this, prednisolone treated animals displayed significantly reduced lung protein levels of neutrophil chemoattractants like CINC-1, CINC-2α/β and LIX and upregulated tissue inhibitor of matrix metalloproteinase (TIMP)-1. Interestingly, lung macrophage invasion was increased in both, Perfadex and prednisolone treated grafts, as measured by MMP-12 or RM4. Markers of anti-inflammatory macrophage transdifferentiation like MRC-1, IL-13, IL-4 and CD163, significantly correlated with prednisolone treatment. These observations lead to the conclusion that prednisolone as an additive to the perfusion solution protects from hypoxia triggered danger signals already in the phase of ischemia and thus reduces graft edema in the phase of reperfusion. Additionally, prednisolone preconditioning might also lead to macrophage polarization as a beneficial long-term effect

Conditional Deletion of LRP1 Leads to Progressive Loss of Recombined NG2-Expressing Oligodendrocyte Precursor Cells in a Novel Mouse Model

The low-density lipoprotein receptor-related protein 1 (LRP1) is a transmembrane receptor, mediating endocytosis and activating intracellular signaling cascades. LRP1 is highly expressed in the central nervous system (CNS), especially in oligodendrocyte precursor cells (OPCs). Previous studies have suggested LRP1 as a regulator in early oligodendrocyte development, repair of chemically induced white matter lesions, and cholesterol homeostasis. To circumvent embryonic lethality observed in the case of global LRP1 deletion, we generated a new inducible conditional knockout (KO) mouse model, which enabled an NG2-restricted LRP1 deficiency (NG2-CreERT2ct2/wtxR26eGFPflox/floxxLRP1flox/flox). When characterizing our triple transgenic mouse model, we noticed a substantial and progressive loss of recombined LRP1-deficient cells in the oligodendrocyte lineage. On the other hand, we found comparable distributions and fractions of oligodendroglia within the Corpus callosum of the KO and control animals, indicating a compensation of these deficits. An initial study on experimental autoimmune encephalomyelitis (EAE) was performed in triple transgenic and control mice and the cell biology of oligodendrocytes obtained from the animals was studied in an in vitro myelination assay. Differences could be observed in these assays, which, however, did not achieve statistical significance, presumably because the majority of recombined LRP1-deficient cells has been replaced by non-recombined cells. Thus, the analysis of the role of LRP1 in EAE will require the induction of acute recombination in the context of the disease process. As LRP1 is necessary for the survival of OPCs in vivo, we assume that it will play an important role in myelin repair

Parton-shower effects in electroweak WZjjWZjj production at the next-to-leading order of QCD

We present an implementation of WZjj production via vector-boson fusion in the POWHEG BOX, a public tool for the matching of next-to-leading order QCD calculations with multi-purpose parton-shower generators. We provide phenomenological results for electroweak WZjj production with fully leptonic decays at the LHC in realistic setups and discuss theoretical uncertainties associated with the simulation. We find that beyond the leading-order approximation the dependence on the unphysical factorization and renormalization scales is mild. The two tagging jets are furthermore very stable against parton-shower effects. However, considerable sensitivities to the shower Monte-Carlo program used are observed for central-jet veto observables

An experimental platform for surface embedded SMAs in morphing applications

This article will address the modeling and control of surface embedded shape memory alloys (SMAs) for the camber modification of a hybrid morphing airfoil. An analytical model will be derived. The results of this models will be discussed and compared to the experiments. The advantages of this modeling approach will be highlighted and alternatives will be briefly revisited. This discussion will figure into the utility of these models in the sizing of a full scale prototype of a SMA actuated active trailing edge of an airfoil. Throughout this article the prototype specifications are detailed and the design choices will be discussed. Performance improvements stemming from the inherent nature of the SMAs will be analyzed. It will be shown in this article that through the use of forced convection the overall cycle time can be reduced

Dynamics of a hybrid morphing wing with active open loop vibrating trailing edge by Time-Resolved PIV and force measures

A quantitative characterization of the effects obtained by high frequency-low amplitude trailing edge actuation is presented. Particle image velocimetry, pressure and aerodynamic forces measurements are carried out on a wing prototype equipped with shape memory alloys and trailing edge piezoelectric-actuators, allowing simultaneously high deformations (bending) in low frequency and higher-frequency vibrations. The effects of this hybrid morphing on the forces have been quantified and an optimal actuation range has been identified, able to increase lift and decrease drag. The present study focuses more specifically on the effects of the higher-frequency vibrations of the trailing edge region. This actuation allows manipulation of the wake turbulent structures. It has been shown that specific frequency and amplitude ranges achieved by the piezoelectric actuators are able to produce a breakdown of larger coherent eddies by means of upscale energy transfer from smaller-scale eddies in the near wake. It results a thinning of the shear layers and the wake's width, associated to reduction of the form drag, as well as a reduction of predominant frequency peaks of the shear-layer instability. These effects have been shown by means of frequency domain analysis and Proper Orthogonal Decomposition