@phdthesis{Doynov2023, author = {Doynov, Nikolay}, title = {Hybride Modelle f{\"u}r Verzugs- und Eigenspannungsberechnung von großen und komplexen Schweißkonstruktionen}, doi = {10.26127/BTUOpen-6453}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-64536}, school = {BTU Cottbus - Senftenberg}, year = {2023}, abstract = {Das Schweißen f{\"u}hrt zu einer lokalen, ungleichm{\"a}ßigen Erw{\"a}rmung der F{\"u}gestelle. Die dadurch hervorgerufenen lokalen plastischen Verformungen und metallurgischen Werkstoffver{\"a}nderungen bewirken nach der Abk{\"u}hlung bleibenden Verzug und Eigenspannungen. Diese beeinflussen die reibungslose Durchf{\"u}hrung des Fertigungsprozesses und die Qualit{\"a}t der geschweißten Konstruktion und schließlich stellen letztlich deren Einsatz in Frage. Somit steht f{\"u}r die meisten Industrieanwendungen die gesicherte Minimierung bzw. Beherrschung des Schweißverzuges und der Schweißeigenspannungen, insbesondere bei großen Konstruktionen im Vordergrund. Mittels der Vorkenntnis {\"u}ber den zu erwartenden Verzug und die Entwicklung der Eigenspannungen w{\"a}hrend und nach dem Schweißen k{\"o}nnen zum einen geeignete Gegenmaßnahmen, wie beispielsweise Einspannszenarien, Vorverformungen oder Schweißreihenfolgen sowie eine gezielte Vor-, Zwischen- oder Nachw{\"a}rmebehandlung zweckm{\"a}ßig gew{\"a}hlt werden. Zum anderen ist es m{\"o}glich, die darauffolgenden notwendigen Nachbehandlungen, wie z.B. das thermische Richten, schon in einem sehr fr{\"u}hen Stadium des Produktentwicklungsprozesses vorauszuplanen. Demzufolge besteht seitens der Forschung ein sehr großes Interesse an der Entwicklung verl{\"a}sslicher Modelle und Methoden zur Schweißverzugs- und Eigenspannungsberechnung. Die vorliegende Habilitationsschrift befasst sich mit den theoretischen Grundlagen und den simulationstechnischen Aspekten der Schweißverzug- und Eigenspannungsberechnung von großen komplexen Schweißkonstruktionen. Im Mittelpunkt stehen die analytisch-numerische Hybridmodelle. Diese bestehen aus einem analytischen Teil f{\"u}r die lokale thermomechanische Berechnung und einen numerischen Teil f{\"u}r die globale strukturmechanische Berechnung. Die beiden Teilaufgaben sind stark gekoppelt. Der Schwerpunkt liegt in der Weiteentwicklung und in den Umsatzm{\"o}glichkeiten des analytischen Ansatzes. Dar{\"u}ber hinaus wird die Anwendung der Hybriden Modellierung zur Berechnung von Verzug und Eigenspannungen in praxisrelevanten Schweißkonstruktionen an zahlreichen Beispielen demonstriert. Die Aspekte der Einbringung der Simulation in die Fertigungs- oder Produktkette werden ebenso thematisiert.}, subject = {Schweißsimulation; Eigendehnung; Schweißverzug; Schweißeigenspannungen; Vortgeschrittene Schweißfertigung; Computational welding mechanics; Inherent strain; Welding distortions; Welding residual stresses; Advanced welding manufacturing; Schweißen; Schweißspannung; Thermomechanik; Strukturmechanik; Tragf{\"a}higkeit; Richten ; Intelligente Fertigung; Computersimulation; Konzeptionelle Modellierung}, language = {de} } @phdthesis{Chauhan2023, author = {Chauhan, Ekta}, title = {Role of community in managing cultural heritage tourism in historical quarters of Delhi : case studies of Nizamudinn Basti and Shahjahanabad}, doi = {10.26127/BTUOpen-6399}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-63990}, school = {BTU Cottbus - Senftenberg}, year = {2023}, abstract = {This doctoral research examines community participation in decision-making for Cultural Heritage Tourism (CHT) in Nizamuddin Basti and Shahjahanabad, historical sites in New Delhi, India. It includes three papers addressing community participation barriers, resident motivation, and collective action dilemmas using the Institutional Analysis and Development-Network of Adjacent Action Situations (IAD-NAAS) framework. The study identifies four main barriers: institutional constraints, limited awareness, capacity issues, and cultural norms inhibiting residents' involvement in CHT decision-making. Despite these obstacles, the community's deep attachment to the area's heritage, appreciation of tangible and intangible heritage, and recognition of communal benefits motivate participation. Using the IAD-NAAS framework, the research unravels collective action dilemmas, emphasizing how individual actions in one context can impact actions in adjacent contexts. Key action situations are monument conservation, local community livelihood development, tourism development, and community decision-making participation. Through in-depth interviews, the study garners a rich understanding of barriers and motivations for community participation. It highlights the role of community involvement in creating inclusive, diverse heritage narratives, challenging the conventional discourses dominating heritage narratives. Thus, fostering a democratic and inclusive approach to heritage.}, subject = {Heritage policy; Community participation; Decision making; Heritage tourism; South Asia; Kulturerbe; Tourismus; S{\"u}dasien; Entscheidungsprozess; Gemeinschaftsbeteiligung; Delhi; Kulturerbe; Tourismus; B{\"u}rgerbeteiligung; Entscheidungsprozess}, language = {en} } @phdthesis{Schreckinger2023, author = {Schreckinger, Jos{\´e}}, title = {Short- and long-term succession in intermittent rivers and ephemeral streams : sediment microbial communities structure and biogeochemical trajectories}, doi = {10.26127/BTUOpen-6379}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-63793}, school = {BTU Cottbus - Senftenberg}, year = {2023}, abstract = {Intermittent rivers and ephemeral streams (IRES) experience drying events, and they are becoming increasingly common due to climate change and anthropogenic water withdrawal. Despite their prevalence, IRES have been less studied than non-drying rivers, and more research is needed to understand their dynamics. This dissertation examines drying events' effects on the sediment microbial community structure and biogeochemistry in temperate IRES. First, a research study was carried out using an outdoor mesocosm setup to track changes in bacterial and fungal communities, microbial functions and properties of sediment-dissolved organic carbon during three different drying events. Results showed that drying duration and intensity and sediment organic matter content regulated river Spree sediment microbial community composition and biogeochemical processes during drying. The associated sediment respiration, assessed as CO2 flux, rapidly declined during all drying treatments, and Bacilli class became the most dominant bacteria after 90 days of drying, except in non-enriched sediment under the most intense drying. Second, a microcosm experiment was conducted to understand how sediment drying history and properties influence biogeochemical dynamics during an IRES expansion phase. Sediment respiration and nutrient release/retention rates were measured through flow resumption, and results showed that drying duration and intensity and sediment organic matter content regulated the dynamics of nutrients and respiration upon flow resumption. Under the most intense and prolonged drying, non-enriched sediment showed a lag response in respiration during the first day after flow resumption, while all other treatments had either a linear increase or a fast pulse in respiration. Finally, the long-term microbial succession in IRES sediment and soil in the experimental catchment of Chicken Creek was investigated. In 2008 and 2018, the sediment of three ephemeral streams and their adjacent soil was analyzed for the structure of the bacterial and fungal communities and microbial functions across different seasons. Results showed that environmental factors, such as vegetation type and organic matter content, mediated sediment and soil microbial succession in Chicken Creek. Ephemeral streams under spare and sporadic flow events remained unique ecosystems with distinctive microbial communities and biogeochemical dynamics, different from its riparian soil. Overall, this dissertation concludes that temperate IRES are dynamic ecosystems where dry-wet cycles and environmental factors modulate their sediment microbial community structure and function trajectories in the short- and long term.}, subject = {Rivers; Drying; Biogeochemistry; Bacteria; Fungi; Fl{\"u}sse; Trocknung; Biogeochemie; Bakterien; Pilze; Fluss; Bach; Bakterien; Pilze; Biogeochemie; D{\"u}rre; Klimawandel; Flusssediment}, language = {en} } @phdthesis{Hamede2023, author = {Hamede, Mohammed Hussein Haytham}, title = {The turbulent very wide-gap Taylor-Couette flow : experimental investigation}, doi = {10.26127/BTUOpen-6445}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-64456}, school = {BTU Cottbus - Senftenberg}, year = {2023}, abstract = {Die Taylor-Couette-Str{\"o}mung (TC), die Str{\"o}mung zwischen zwei konzentrischen, unabh{\"a}ngig voneinander rotierenden Zylindern, wird als perfektes Modell zur Untersuchung von Scherstr{\"o}mungen {\"u}ber konkaven Oberfl{\"a}chen verwendet und ist eines der paradigmatischen Systeme der Fluidphysik. In dieser Arbeit wird eine experimentelle Untersuchung der turbulenten TC-Str{\"o}mung in einer sehr breiten Spaltgeometrie mit einem Radiusverh{\"a}ltnis 𝜂 = 0,1 durchgef{\"u}hrt. Das physikalische und dynamische Verhalten der Str{\"o}mung wird in einer Geometrie untersucht, die vor der vorliegenden Studie kaum untersucht wurde, was diese Studie einzigartig macht. Ziel der Studie ist es, die Auswirkungen der Kr{\"u}mmung auf die TC-Str{\"o}mung zu verstehen, insbesondere in F{\"a}llen, in denen die Umfangsl{\"a}nge des inneren Zylinders kleiner ist als die Spaltbreite. Die Str{\"o}mung wird in den verschiedenen Rotationsregimen untersucht: gegenl{\"a}ufige, mitl{\"a}ufige und reine Innenzylinder-Rotationsregime bis zu Scher-Reynoldszahlen Re_s≤ 150000. Das Str{\"o}mungsfeld wurde mit Hilfe von Visualisierungstechniken qualitativ untersucht. Bei der Untersuchung der verschiedenen Str{\"o}mungsparameter zeigen sich bekannte koh{\"a}rente TC-Str{\"o}mungsmuster sowie neu beobachtete Muster, von denen wir annehmen, dass sie nur bei TC-Str{\"o}mungen mit sehr großem Spalt existieren. F{\"u}r eine detailliertere quantitative Untersuchung wurde eine zeitaufgel{\"o}ste Messung des Geschwindigkeitsfeldes mit der Hochgeschwindigkeits-Partikel-Image-Velocimetry-Technik durch die Endplatte des Systems durchgef{\"u}hrt. Die radialen und azimutalen Geschwindigkeitskomponenten in der horizontalen 2D-Ebene werden an verschiedenen axialen Positionen gemessen, um die axiale Varianz der Str{\"o}mung zu erfassen. Das aufgezeichnete Str{\"o}mungsfeld wird verwendet, um den Drehimpulstransport in Form der Quasi-Nusselt-Zahl (Nu_ω) zu berechnen. Die Ergebnisse zeigen ein Maximum der Nu_ω f{\"u}r niedrige gegenl{\"a}ufige Raten von -0,011 ≤ μ_max ≤ -0,0077, was mit großr{\"a}umigen Strukturen verbunden ist, die den gesamten Spalt {\"u}berspannen. Dar{\"u}ber hinaus nimmt Nu_ω f{\"u}r Gegenrotationsraten, die h{\"o}her als μ_max sind, ab, bis es einen Minimalwert erreicht, und steigt dann f{\"u}r h{\"o}here Gegenrotationsf{\"a}lle tendenziell wieder an. Das Raum-Zeit-Verhalten des turbulenten Str{\"o}mungsfeldes f{\"u}r die F{\"a}lle mit hoher Gegenrotation zeigt die Existenz neu beobachteter Muster neben der {\"a}ußeren Zylinderwand, die sich nach innen ausbreiten, den Drehimpulstransport verst{\"a}rken und zu einem zweiten Maximum im Transport f{\"u}r h{\"o}here Gegenrotationsraten f{\"u}hren. Das Raum-Zeit-Verhalten des turbulenten Str{\"o}mungsfeldes f{\"u}r die F{\"a}lle mit hoher Gegenrotation zeigt die Existenz von neu beobachteten Mustern neben der {\"a}ußeren Zylinderwand, die sich nach innen ausbreiten, den Drehimpulstransport verst{\"a}rken und zu einem zweiten Maximum des Transports f{\"u}r h{\"o}here Gegenrotationsraten f{\"u}hren. F{\"u}r den rein rotierenden inneren Zylinder skaliert der Impulstransport.}, subject = {Experimental fluid mechanics; Taylor-Couette flow; Rotating flow; Turbulence; Particle image velocimetry; Experimentelle Str{\"o}mungsmechanik; Taylor-Couette-Str{\"o}mung; Rotationsstr{\"o}mung; Turbulenz; Turbulente Str{\"o}mung; Str{\"o}mungsmechanik; Rotationsstr{\"o}mung; Taylor-Couette-Str{\"o}mung}, language = {en} } @phdthesis{Takam2023, author = {Takam, Paul Honore}, title = {Stochastic optimal control problems of residential heating systems with a geothermal energy storage}, doi = {10.26127/BTUOpen-6450}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-64502}, school = {BTU Cottbus - Senftenberg}, year = {2023}, abstract = {In this thesis we consider a residential heating system equipped with several heat production and consumption units and investigate the stochastic optimal control problem for its cost-optimal management. As a special feature the manager has access to a geothermal storage (GS) which allows for inter-temporal transfer of heat energy by storing leftover solar thermal energy generated in summer for satisfying demand later. It is charged and discharged via heat exchanger pipes filled with a moving fluid. Further, the manager of that system faces uncertainties about the future fuel price and heat demand. The main goal is to minimize the expected aggregated cost for generating heat and running the system. This leads to a challenging mathematical optimization problem. The problem is formulated first as a non-standard continuous-time stochastic optimal control problem for a controlled state process whose dynamics is described by a system of ordinary differential equations (ODEs), stochastic differential equations and a partial differential equation (PDE). The PDE, which describes the temperature distribution in the GS, is first converted into a high-dimensional system of ODEs by semi-discretizing the space variables and its stability is investigated. This makes it possible to compute some aggregated characteristics which are useful for the operation of the GS embedded in the residential heating system. Second, the linear time-varying system of ODEs is approximated by a suitable linear time-invariant system. This allows the Lyapunov balanced truncation model order reduction method to be applied. Finally, we investigate the solution of the resulting standard optimal control problem for a controlled multi-dimensional diffusion process using dynamic programming methods and derive the corresponding Hamilton-Jacobi-Bellman (HJB) equation. However, no analytical solution of the HJB equation can be expected for the control problem under investigation. Therefore, we transform the continuous-time optimal control problem into a discrete-time control problem for a controlled Markov chain with finitely many states by discretizing both the time and the states. After determining the transition probabilities, the problem is solved using methods from the theory of Markovian decision processes. The thesis presents results of extensive numerical experiments carried out with the developed methods which reveal typical properties of the value function and the optimal strategy of the optimization problem. We end this thesis by describing some alternative methods to overcome the curse of dimensionality.}, subject = {Markov-Entscheidungsprozesse; Erdw{\"a}rmespeicher; Numerische Simulation; Modellreduktion; Lyapunov-Balanced-Truncation; Markov decision process; Geothermal energy storage; Numerical simulation; Model order reduction; Lyapunov balanced truncation; Erdw{\"a}rmespeicher; Heizung; Markov-Entscheidungsprozess; Ordnungsreduktion}, language = {en} } @phdthesis{Trinh2023, author = {Trinh, Xuan Manh}, title = {A methodological framework for future flood risk assessment in ungauged and data-scarce coastal river catchments in Southeast Asia}, doi = {10.26127/BTUOpen-6441}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-64411}, school = {BTU Cottbus - Senftenberg}, year = {2023}, abstract = {Ungauged and data-scarce coastal river catchments, small and medium-sized ones in particular, are popular worldwide, especially in developing countries in Southeast Asia. In general, coastal river catchments are exposed to various coastal hazards such as fluvial floods, typhoons, and sea-level rise. In addition, climate change and socio-economic development will substantially change global flood risks. However, in scientific research, flood risk and future flood risk assessments in such coastal river catchments have not been significantly considered. Therefore, the overall objective of this thesis is to propose an innovative methodological framework for modeling and evaluating flood risk in such river catchments in the future under the impacts of climate change, sea-level rise, and land-use change based on using numerical models (hydrological models and land-use change models) and remote sensing data (satellite images and precipitation) in combination with other state-of-the-art methods, tools and models, and new approaches, such as flood risk assessment methods, regionalization methods, and statistical downscaling methods. The proposed framework was adopted, applied, and validated successfully for a case study - Tra Bong River Catchment - on the south-central coast of Vietnam as a test application. The main conclusion of this research is that the proposed framework can provide valuable information and projections of changing future flood risk associated with climatic and socio-economic changes in ungauged and data-scarce coastal river catchments. The proposed framework is designed with free model and method choices, meaning that it can apply different methods and tools for each step depending on the natural characteristics of river catchments, data collection, tools, and understanding of models, etc. Finally, this research can be used as a technical reference for designing and building national, regional, or local frameworks/guidelines for assessing future flood risk in ungauged and data-scarce coastal river catchments in Vietnam and other countries in Southeast Asia.}, subject = {Methodological framework; Numerical models; Flood risks; Climate change; Ungauged catchments; Methodologisches Modellierungskonzept; Numerische Modelle; Hochwasserrisiko; Klimawandel; Einzugsgebiete ohne Messdaten; Mittelvietnam; K{\"u}stengew{\"a}sser; Klimawandel; Hochwasser; Datenerhebung; Methodologie; Modllierung; Numerisches Modell}, language = {en} } @phdthesis{Pizzi2023, author = {Pizzi, Federico}, title = {Numerical studies of a fluid-filled precessing cylinder : a framework for the DRESDYN precession experiment}, doi = {10.26127/BTUOpen-6421}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-64218}, school = {BTU Cottbus - Senftenberg}, year = {2023}, abstract = {Precession driven flows are believed to play a relevant role in planetary dynamics, such as in atmospheric phenomena, and as a complementary energy source for homogeneous dynamo action, i.e. the self-generation of planetary magnetic fields. Precessional motion occurs when a body rotates around an axis, which itself is rotating around another axis. The main influence of this forcing mechanism is a gyroscopic effect on the fluid flow which gives rise to a wavy dynamics even in the laminar regime. If the forcing magnitude is strong enough the flow goes through a series of phenomena such as instabilities, resonant interactions between waves, and transition to turbulence whose occurrence depends on the container shape and the angle between the two axis. Although many phenomena have a satisfactory explanation, others still remain elusive and merit further investigations. The interest in moderate to large forcing is particularly motivated by the need of theoretical supports for the upcoming DRESDYN (DREsden Sodium facility for DYNnamo and thermohydraulic studies) precession experiment, whose main purpose is to test the capability of a precessing fluid system to achieve a dynamo effect. Here, the possibility to generate a magnetic field is connected to the emergence of three large scale structures in the bulk flow: a directly forced standing wave, poloidal vortices, and a geostrophic axisymmetric flow. In this thesis we use numerical simulations to study and understand the flow behavior in a fluid-filled precessing cylinder. We use two types of approaches: a global study to investigate large scale phenomena and the resulting magnetohydrodynamics behavior, and a local model to analyze and unveil the properties of turbulence forced by precession. The bulk flow behavior present different responses with respect to the sense of motion: while prograde precession shows a steep transition to turbulence when increasing the forcing magnitude with a marked breakdown of the directly forced mode, retrograde precession presents a much smoother change. A related distinction has been found also for the dynamo action, which is more likely to occur for perpendicular and retrograde precession. The precession driven turbulence is a complex scenario determined by the coexistence of geostrophic vortices (called also condensates), a typical feature of rotating turbulence prone to an inverse cascade of energy, and small scale 3D waves characterized by a direct energy cascade. We observe the interaction of these two structures as being governed by a clear hierarchy.}, subject = {Inertial waves; Precession-driven flows; Rotating turbulcence; Dynamo action; Pr{\"a}zessionsgetriebene Str{\"o}mungen; Inertialwellen; Dynamo-Aktion; Rotierende Turbulenzen; Turbulente Str{\"o}mung; Atmosph{\"a}rische Turbulenz; Inertialsystem; Dynamotheorie; Gyroskop}, language = {en} } @phdthesis{Zhang2023, author = {Zhang, Yangwen}, title = {Self-sufficient semi-active vibration control of high-rise buildings under wind excitation by moveable double-skin facades}, issn = {2569-2798}, doi = {10.26127/BTUOpen-6381}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-63811}, school = {BTU Cottbus - Senftenberg}, year = {2023}, abstract = {The accelerated urbanization has led to increasing tension on urban land use. In this context, more and more slender high-rise buildings are being built worldwide in pursuit of better economic benefits. However, these structures are susceptible to wind excitation due to their lower first natural frequency. Different passive, semi-active, and active damping systems have been developed to reduce wind-induced structural vibration. Among them, the tuned mass dampers are widely used and proved as a very effective method in practice. However, this system requires a large additional damping mass. This also causes additional reinforcement, which increases the cost and carbon footprint. A huge space near the top story of the building is needed for the installation. In this research, a novel system named distributed-Multiple Tuned Facade Damping (d-MTFD) system is proposed by using specially designed parallel moveable Double-Skin Facade (DSF) outer skin as damping mass. These moveable facade elements can be installed on the upper stories of the high-rise building. Smooth-running guide rail systems are used to achieve the parallel moveability. Multi-objective optimization based on the Genetic Algorithm (GA) is applied to reduce the maximum top floor acceleration (Objective I) and to reduce the maximum facade relative displacement (Objective II) simultaneously. The optimization results for the passive and semi-active systems are presented in the form of the Pareto front. The trade-off between these selected two competing optimization objectives is observed. This approach was first validated in a simulation using a 306 m tall reference building for a wind speed of 13.5 m/s at 10 m above ground level with a return period of 10 years. Acceptable peak accelerations at the top story for hotel use and a maximum facade relative displacement of less than ±0.5 m could be achieved for the benchmark building with the d-MTFD system. For semi-active control, the variable damping coefficient can be achieved by using stepper motors in generator mode. The electrical damping coefficient can be continuously adjusted by the developed power electronics. In addition, electrical energy can be generated and stored in a battery. A full-scale prototype with one parallel moveable facade element was built. Based on the prototype, the functionality of the semi-active control using a stepper motor and its energy harvesting performance was tested by applying Hardware-in-the-Loop (HiL) simulations. Greybox system identification was used to estimate some parameters (spring stiffness, friction, etc.) in the connection. The accurate system identification results ensure further validation using HiL simulations. The HiL simulations successfully demonstrated the feasibility of a self-powered semi-active d-MTFD system.}, subject = {Energy harvesting; Energiegewinnung; Distributed-Multiple Tuned Facade Damping system; d-MTFD; Hardware-in-the-Loop simulation; HiL; System identification; Systemidentifikation; Semi-active vibration control; Semi-aktive Schwingungskontrolle; Hochhaus; Schlankes Bauwerk; Doppelte Fassade; Schwingungsd{\"a}mpfung; Windlast; Mehrkriterielle Optimierung; Hardware-in-the-loop; Genetischer Algorithmus; Energieerzeugung; Prototyp}, language = {en} } @phdthesis{Rakhi2023, author = {Rakhi,}, title = {Stochastic modeling of the turbulent boundary layer}, doi = {10.26127/BTUOpen-6416}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-64162}, school = {BTU Cottbus - Senftenberg}, year = {2023}, abstract = {The incompressible temporally developing turbulent boundary layer (TBL) and spatially developing turbulent boundary layer (SBL) with and without blowing is analyzed using the map-based stochastic one-dimensional turbulence (ODT) model. An understanding of these idealized flows is of fundamental relevance for boundary layer-type problems, which are frequently encountered in several applications, from atmospheric sciences to engineering. In the ODT model, the flow variables are resolved on all scales along a wall-normal, 1-D domain. These variables are evolved by a deterministic process representing molecular diffusion and by a stochastic process modeling the effect of turbulent advection and pressure fluctuations. Due to the reduction in dimensionality, the model is particularly appropriate for high Reynolds number flow. It is shown that the ODT model is able to capture salient features of the turbulent boundary layer-type flows by comparing the results with various available reference direct numerical simulation (DNS), large eddy simulation (LES) and experimental results. The comparison is presented for the mean velocity profiles, turbulent velocity fluctuation profiles (up to fourth order), the skin friction coefficient and shape factor for different bulk (Reb) and momentum Reynolds numbers (Reθ) using fixed model parameters. The influence of the model parameters is also discussed for various momentum Reynolds numbers for each investigated flow configuration. The results discussed in this thesis suggest that the ODT model is an economical and reasonably accurate approach for the simulation of turbulent boundary layer flows.}, subject = {Turbulent flow; Turbulent boundary layer; Stochastic modeling; One-dimensional turbulence; Turbulente Str{\"o}mung; Turbulente Grenzschicht; Stochastische Modellierung; Eindimensionale Turbulenz; Turbulente Str{\"o}mung; Turbulente Grenzschicht; Statistisches Modell}, language = {en} } @article{OttoAlipoursarbaniTorrentetal.2023, author = {Otto, Pascal and Alipoursarbani, Mozhdeh and Torrent, Daniel and Latorre-P{\´e}rez, Adriel and Paust, Thomas and Albert, Alfred and Abendroth, Christian}, title = {Microbiome characterization after aerobic digestate reactivation of anaerobically digested sewage sludge}, volume = {9}, number = {5}, publisher = {MDPI}, address = {Basel}, issn = {2311-5637}, doi = {10.3390/fermentation9050471}, year = {2023}, abstract = {A demonstrator plant of a recently patented process for improved sludge degradation has been implemented on a municipal scale. In a 1500 m3 sewage sludge digester, an intermediary stage with aerobic sewage sludge reactivation was implemented. This oxic activation increased the biogas yield by up to 55\% with a 25\% reduction of the remaining fermentation residue volume. Furthermore, this process allowed an NH4-N removal of over 90\%. Additionally, 16S rRNA gene amplicon high-throughput sequencing of the reactivated digestate showed a reduced number of methane-forming archaea compared to the main digester. Multiple ammonium-oxidizing bacteria were detected. This includes multiple genera belonging to the family Chitinophagaceae (the highest values reached 18.8\% of the DNA sequences) as well as a small amount of the genus Candidatus nitrosoglobus (<0.3\%). In summary, the process described here provides an economically viable method to eliminate nitrogen from sewage sludge while achieving higher biogas yields and fewer potential pathogens in the residuals.}, subject = {Anaerobic digestion; Anaerobic microbiomes; Aerobic sludge activation; 16S rRNA sequencing; Water treatment; Belebtschlammverfahren; Schlammfaulung; Mikroorganismus; G{\"a}rung; Biogas; Stickstoff-Elimination; Anaerobe Verg{\"a}rung; Anaerobe Mikrobiome; Aerobe Schlammaktivierung; 16S-rRNA-Sequenzierung; Wasserversorgung}, language = {en} }