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    Mixing structures in bubble wakes of single bubbles and bubble swarms and their influence on gas-liquid mass transfer and chemical reactions
    The main objective of this proposal is to unveil how mixing structures in the wakes of freely rising single bubbles and in bubble swarms can be incorporated into compact mass transfer correlations for process engineering. In this way the impact of the wakes on chemical reactions can be estimated more easily. The knowledge about the detailed mass transfer is crucial to produce a vast proportion of bulk chemicals used in everyday life that are synthesized in gas-liquid reactions like hydrogenation, oxidation, or chlorination. Furthermore, contained high gas concentrations in bubble wakes can also be potentially harmful to microorganisms and enzymes in gassed reactors leading to a substrate inhibition. To predict how much gas is transferred from a bubble to a surrounding liquid the mass transfer coefficient (or the nondimensionalized Sherwood number )has to be determined. Todays mass transfer models (Sherwood correlations) either build on the two-film theory, on the penetration theory, or on the surface-renewal theory with varying parameters in dependence on bubble relative velocity to the surrounding liquid and laminar or turbulent surrounding flow conditions. Adapted models exist to account for the effect of surfactants onto the mass transfer. All theories assume, however, that once the gas is dissolved in the liquid phase it gets immediately well mixed and that all fluid parcels passing the bubble interface experience the same conditions in the bubble wake once they leave the bubble surface. This picture neglects effects of a heterogeneous concentration wake that will likely influence a reaction taking place close to the bubble interface and in the bubble wake for small to intermediate Hatta numbers as according to Levenspiel. So far, the details of the structure of the mixing in the bubble wake are not considered for mass transfer correlations. In this research proposal, the Lagrangian coherent structures (LCS) in the bubble wake of 3D freely rising bubbles and bubble swarms in stagnant liquid will be analyzed by evaluating 4D-PTV measurements using recently developed mathematical tools stemming from dynamical systems theory. Additionally, a quantitative evaluation of the concentration of the dissolved gas will be obtained using Time Resolved Laser Induced Fluorescence (TRS-LIF). The LCS will be compared to the concentration wakes and both measurements supply input for the development of new Sherwood correlations that incorporate the effect of coherent flow structures in bubble wakes.
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    Critical Components for Distributed and Secure Grid Operation
    Die Elektrifizierung des Mobilitäts- und Wärmesektors und die starke Zunahme der EEG-Einspeisung durch Photovoltaik Anlagen stellt eine Herausforderung für Verteilnetzbetreiber dar, da die elektrischen Verteilnetze nicht für die zu erwartenden Lastzuwächse ausgelegt sind. Deswegen ist eine intelligente Netzautomatisierung erforderlich, um in zukünftigen Szenarien weiterhin eine hohe Versorgungsqualität zu gewährleisten, bei gleichzeitiger Minimierung des Netzausbaus durch optimale Netzausbaustrategien. Hierfür ist eine Netzzustandsüberwachung auf Nieder- und Mittelspannungsebene notwendig, sowie die Integration steuerbarer Anlagen, um im Bedarfsfall Lasten sowie Einspeisungen netzdienlich einzusetzen. Die Digitalisierung des elektrischen Verteilnetzes, beispielsweise anhand einer Energie-Internet-of-Things-Plattform und der darauf aufbauenden Etablierung einer aktiven Netzführung durch Smart Grid Microservices, stellt einen notwendigen und möglichen Schritt dar. Im Projekt DISEGO arbeitet ein interdisziplinärer Verbund aus Forschung und Industrie zusammen. Gemeinsam bündeln sie ihre jeweilige Expertise, um eine zukunftsfähige Technologie zu entwickeln und in die Praxis zu überführen. Der Beitrag der TUHH besteht vorrangig aus der Entwicklung eines Algorithmus zur Netzzustandsschätzung (State Estimation) in Niederspannungsnetzen. Dabei werden Erkenntnisse über die Einflüsse unterschiedlicher Messdurchdringungen und Fehler auf die Robustheit des genannten Algorithmus und die Beobachtbarkeit des Netzes sowie die Einbindung neuartiger Komponenten im Netz berücksichtigt und gesammelt. Darüber hinaus ist die TUHH für eine umfassende Überprüfung der entwickelten Ansätze im Labor mithilfe von Echtzeitsimulationen verantwortlich.
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    Developing and Implementing Sustainability-Based Solutions for Bio-Based Plastic Production and Use to Preserve Land and Sea Environmental Quality in Europe
    The project BIO-PLASTICS EUROPE addresses the topic „Sustainable solutions for bio-based plastics on land and sea“ (Topic identifier: CE-BG-06-2019), within the focus area „Connecting economic and environmental gains - the Circular Econonmy (CE)“ and will focus on sustainability strategies and solutions for bio-based products to support the Plastics Strategy. This shall include innovative product design and business models facilitating efficient reuse and recycling strategies and solutions, including ensuring the safety of recycled materials when used for toys or packaging food stuffs. In line with the EU strategy on international cooperation in research and innovation and in order to encourage the further replication, the European consortium is complemented by a partner in Malaysia, providing an added value and helping them to address the many problems they face.
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