A Numerical Test Rig for Turbomachinery Flows Based on Large Eddy Simulations With a High-Order Discontinuous Galerkin Scheme - Part 3: Secondary Flow Effects

In this final paper of a three-part series, we apply the numerical test rig based on a high-order Discontinuous Galerkin scheme to the MTU T161 low pressure turbine with diverging end walls at off-design Reynolds number of 90,000, Mach number of 0.6 and inflow angle of 41'. The inflow end wall boundary layers are prescribed in accordance with the experiment. Validation of the setup is shown against recent numerical references and the corresponding experimental data. Additionally, we propose and conduct a purely numerical experiment with upstream bar wake generators at a Strouhal number of 1.25, which is well above what was possible in the experiment. We discuss the flow physics at midspan and in the end wall region and highlight the influence of the wakes from the upstream row on the complex secondary flow system using instantaneous flow visualization, phase averages and modal decomposition techniques

Bridging ligands comprising two or more di-2-pyridylmethyl or amine arms: alternatives to 2,2'-bipyridyl-containing bridging ligands

Bridging ligands incorporating 2,2'-bipyridine as a chelating component have been utilised for several decades and are widely employed in coordination chemistry, supramolecular chemistry and materials synthesis. Such ligands form stable 5-membered chelate rings upon coordination to a metal. Two related chelating units, di-2-pyridylamine and di-2-pyridylmethane, which form 6-membered chelate rings when coordinated to a metal, have been studied far less as components of bridging ligands but have recently garnered significant levels of attention. Of around 140 reports on the incorporation of these moieties into bridging ligands some 75% have been published in the last 15 years. This review covers the synthesis of bridging ligands containing di-2-pyridylamine and di-2-pyridylmethane chelating moieties, and a survey of their coordination and supramolecular chemistry. Applications of the resulting systems as structural and functional models of enzyme active sites, and spin-crossover materials, and for investigations into anion-π interactions are covered. © 2011 Elsevier B.V.Christopher J. Sumbyhttp://www.elsevier.com/wps/find/journaldescription.cws_home/500845/description#descriptio

Comprehensive characterisation of turbulence dynamics with emphasis on wall-bounded flows

This report describes the work carried out in `universality' aspects of the dynamics of turbulence in compressible flows. Direct numerical simulations (DNSs) are carried out in different inhomogeneous and anisotropic flows. All discussed flows show regions of strong imbalance of turbulent production and turbulent dissipation. This distinguishes this work from most studies in the literature about the fundamentals of turbulent dynamics. A characteristic decomposition in addition to temporal and spatial filtering are applied as tools to compare differences in the turbulent dynamics across different flow topologies. The work includes a discussion about universal aspects of the velocity gradient and related quantities in a turbulent boundary layer, in a jet flow as well as in a wake flow. Invariant features are highlighted and quantified and the differences are pointed out. The velocity gradient and the enstrophy production, as one of the key quantities in the turbulent energy cascading process, are discussed in great detail in the turbulent boundary layer flow. Focus hereby is on the wall-normal development of the structure of the enstrophy production. This is followed by a comprehensive overview of a turbulent boundary layer. This includes the presentation and discussion of global energy redistributing mechanisms from different perspectives. The key role of turbulence in these processes is made clear. The energy cascade is dissected at different locations which reveals three different transfer processes. Two of which are transferring energy from larger scales of motion towards smaller scales of motion. In addition a backscatter mechanism was discovered that transfers energy from smaller scales towards larger scales of motion. Besides this some specific and potentially universal features of turbulence within the turbulent boundary layer results are discussed

Genotypic and phenotypic characterization of hemolysin-producing Vibrio parahaemolyticus strains

Vibrio parahaemolyticus ist weltweit der bedeutendste Erreger von Lebensmittelinfektionen durch Verzehr von rohen oder ungenügend erhitzten Meeresfrüchten und Fisch. Dabei können Symptome einer akuten Gastroenteritis, wie Erbrechen, Durchfall oder abdominale Krämpfe auftreten. Als wichtige Pathogenitätsfaktoren gelten die Hämolysine TDH (thermostable direct hemolysin) und TRH (TDH-related hemolysin) sowie das T3SS2 (Typ 3 Sekretionssystem 2). In deutschen Küstengewässern treten tdh positive Stämme nur sehr selten auf, während trh positive Isolate regelmäßig detektiert werden. In dieser Arbeit wurde eine Vielzahl an V. parahaemolyticus Stämmen verschiedenen geographischen Ursprungs auf Virulenzgene mittels PCR untersucht und über verschiedene phänotypische Tests, wie z.B. hämolytische Aktivität, Sekretion extrazellulärer Enzyme, Resistenz gegenüber humanem Serum und Biofilmbildung, welche als potentiell pathogene Eigenschaften gelten, charakterisiert. Zur genaueren Untersuchung und Charakterisierung der Hämolysine TDH und TRH wurde deren Synthese in einem zellfreien System etabliert. Um den Einfluss des Signalpeptids und verschiedener Protein-Tags auf die Funktionalität zu untersuchen, wurden acht TDH-Konstrukte mittels zellfreier Proteinsynthese hergestellt und anschließend die hämolytische Aktivität getestet. TDH-Konstrukte mit Signalpeptid, also Voräluferproteine, wiesen fast keine Löslichkeit in wässriger Lösung auf und waren nicht hämolytisch, während TDH-Konstrukte ohne Signalpeptid, also reife Proteine, löslich waren und eine eindeutige hämolytische Aktivität zeigten. Die Protein- Tag-Kombinationen zeigten eine geringe bis starke Hemmung der Proteinfunktionalität. Als zentraler Aspekt dieser Arbeit wurde eine Auswahl an einheimischen trh positiven V. parahaemolyticus Stämmen mit trh positiven Stämmen aus anderen Regionen der Welt bezüglich ihres pathogenen Potentials und des Verwandtschaftsgrads miteinander verglichen. Die kodierende Sequenz der trh-Gene zeigte eine Clusterung in drei Varianten: trh1, trh2 und ψtrh. Letzteres ist vermutlich ein Pseudogen. Alle deutschen Stämme, welche aus Muscheln, Meerwasser und Patienten isoliert wurden, trugen die trh2-Genvariante. Die Multilokus-Sequenz-Analyse zeigte eine nahe Verwandtschaft zwischen deutschen und norwegischen Isolaten, welche somit wahrscheinlich Teil der autochthonen marinen Mikroflora in Nordeuropa sind. Bei Stämmen, welche das Pseudogen ψtrh im Genom trugen, konnte das vopC-Gen, welches für einen Effektor des T3SS2 kodiert, nicht nachgewiesen werden. Alle anderen trh positiven Stämme dagegen besaßen das vopC-Gen. Die Transkription der trh-Varianten sowie des vopC-Gens wurde unter verschiedenen Wachstumsbedingungen untersucht. Dabei wurde der Einfluss von Galle und Harnstoff untersucht, welche u.a. in den menschlichen Gastrointestinaltrakt ausgeschieden werden. Die trh1-Transkription konnte mithilfe von Gallenextrakt induziert werden, während keine Induktion der trh2-Genexpression beobachtet wurde. Die vopC-Transkription konnte in trh2 positiven Stämmen durch Harnstoff induziert werden. Die meisten trh1-tragenden Stämme waren gegenüber Schaferythrozyten hämolytisch, während alle trh2 positiven Stämme keine hämolytische Aktivität zeigten. Auch das zellfrei hergestellte TRH1-Protein war stark hämolytisch, während zellfrei synthetisierte TRH2-Proteine keine Aktivität zeigten. Die Ergebnisse dieser Arbeit zeigen eine hohe Diversität unter trh positiven V. parahaemolyticus Stämmen und stellen die Funktionalität der TRH2-Proteine sowie die Rolle des ψtrh-Gens als Pathogenitätsfaktor in Frage. Für eine Bewertung des pathogenen Potentials von V. parahaemolyticus Stämmen wäre eine Differenzierung zwischen den trh-Varianten sowie die Detektion von Komponenten des T3SS2 wie VopC eine sinnvolle Maßnahme in der Diagnostik und könnte zu einer verbesserten Risikobewertung beitragen.Vibrio parahaemolyticus is the major pathogen associated with the consumption of raw or undercooked seafood and causing acute gastroenteritis. The hemolysins TDH (thermostable direct hemolysin) and TRH (TDH-related hemolysin) as well as T3SS2 (type 3 secretion system 2) are considered to be major pathogenicity factors. While tdh positive strains are rarely detected in coastal waters of Germany, trh harbouring strains are found regularly. In this work V. parahaemolyticus strains of different geographic origin were analyzed for pathogenicity factors using PCR. Selected phenotypic traits which might contribute to pathogenicity, like hemolytic activity, secretion of extracellular enzymes, serum resistance and biofilm formation were tested in various assays. The cell-free synthesis of hemolysins TDH and TRH was established to analyze and compare the hemolysins. Eight TDH constructs were synthesized in a cell-free system to investigate the influence of signal peptide and protein tags on protein functionality. Precursor proteins with signal peptide and mature proteins were tested by hemolysis assays showing that precursor proteins were not soluble and therefore not active while mature proteins were soluble and revealed hemolytic activity. Inhibition of protein functionality by protein tags varied between tag types and tag combinations. Major part of this work was the characterization of the pathogenic potential of trh habouring V. parahaemolyticus strains from Germany which were compared to trh positive strains from other geographical regions. The complete trh sequences revealed a clustering into three different types: trh1 and trh2 genes and a pseudogene ψtrh. All German isolates possessed alleles of the trh2 gene. Multilocus sequence typing analysis indicated a close relationship of German and Norwegian isolates suggesting that these strains belong to the autochthonous microflora of Northern Europe seawaters. Strains carrying the pseudogene ψtrh were negative for T3SS2 effector vopC while all other trh positive strains exhibited vopC gene. Transcription of trh and vopC genes was analyzed under different growth conditions to examine the influence of bile and urea as both substances are present in the human intestinal tract. Trh2 gene expression was not altered by bile while trh1 genes were inducible. VopC could be induced by urea in trh2 bearing strains. Most trh1 carrying strains were hemolytic against sheep erythrocytes while all trh2 positive strains did not show any hemolytic activity. TRH variants were synthesized in a cell-free system and their hemolytic activity was analyzed. TRH1 was active against sheep erythrocytes while TRH2 variants were not active at all. This work reveals a high diversity among trh positive V. parahaemolyticus strains. The function of TRH2 hemolysins and the role of the pseudogene ψtrh as a pathogenicity factor are questionable. To assess the pathogenic potential of V. parahaemolyticus strains a differentiation of trh variants and the detection of T3SS2 components like vopC would improve V. parahaemolyticus diagnostics and could lead to a refinement of the risk assessment in food analyses and clinical diagnostics

Evolution of the velocity gradient tensor invariant dynamics in a turbulent boundary layer

In order to improve the physical understanding of the development of turbulent structures, the compressible evolution equations for the first three invariants P,Q and R of the velocity gradient tensor have been derived. The mean evolution of characteristic turbulent structure types were studied and compared at different wall-normal locations of a compressible turbulent boundary layer. The evolution of these structure types are fundamental to the physics that need to be captured by turbulence models. Significant variations of the mean evolution are found. The key features of the changes of the mean trajectories in the invariant phase space are highlighted and the consequences of the changes are discussed. Further, the individual elements of the overall evolution are studied separately to identify the causes that lead to the evolution varying with the distance to the wall. Significant impact of the wall-normal location on the coupling between the pressure-Hessian tensor and the velocity gradient tensor was found