A Statistical Analysis of Surface Pressure Measurements with Particular Reference to Vortex Breakdown. G.U. Aero Report 9806

This paper describes and presents results from static wind tunnel tests conducted on a 60° delta wing at a root chord Reynolds number of 2.7 x 10[sup]6. In these tests, the wing was instrumented with 192 miniature pressure transducers which, in conjunction with a powerful multi-channel data-logging system, allowed the distribution of timevarying surface pressures to be measured at high temporal resolution. Analysis indicates that the distribution of root-mean-square pressure on the leeward surface of the wing can provide considerable insight into the behaviour of both the primary and secondary vortex structures. In addition, it has been established that the frequency content of pressure signals measured in the vicinity of these vortex structures is sensitive to the vortex state. It is suggested that these data features can be directly attributed to previously observed behavioural characteristics of the vortex breakdown process

A Preliminary Study of the Flow around a Delta Wing using High Resolution Pressure Measurements. G. U. Aero Report no. 9720

A study of the flow around delta wings has been carried out in a series of experiments in the University’s Handley-Page Wind-Tunnel facility. The objective of the experiments was to capture high spatial and temporal resolution pressure measurements on a specially designed 60° delta wing model. This project has been devised to analyse the results of the study with a view to determining a reliable method of vortex breakdown detection on delta wings using data obtained from pressure measurements alone. A fundamental requirement of the proposed method is that it should apply equally under static and dynamic conditions. In order to achieve the aim of the project, a broad understanding of the physics of vortical flows is required. This is to be achieved in two ways; firstly, by carrying out a literature research exercise on the nature, causes and effects of vortex breakdown, secondly, to validate the findings of the pressure data analysis by carrying out further experiments using smoke visualisation techniques. The findings of the literature research exercise are presented, together with a description of the wind-tunnel experiments and the preliminary results from the analysis of the pressure data. The models to be used in the forthcoming smoke visualisation experiments have been built and a series of tests have been carried out to evaluate their design. A description of the smoke tunnel models and the results of these tests are also presented. The work of this project has so far highlighted a number of issues to be dealt with in future research as part of this project. To conclude this report, a series of proposals are presented detailing the work required to resolve these issues

Analysis of model rotor blade pressures during parallel interaction with twin vortices

This paper presents and provides analysis of unsteady surface pressures measured on a model rotor blade as the blade experienced near parallel blade vortex interaction with a twin vortex system. To provide a basis for analysis, the vortex system was characterized by hot-wire measurements made in the interaction plane but in the absence of the rotor. The unsteady pressure response resulting from a single vortex interaction is then presented to provide a frame of reference for the twin vortex results. A series of twin vortex interaction cases are then presented and analyzed. It is shown that the unsteady blade pressures and forces are very sensitive to the inclination angle and separation distance of the vortex pair. When the vortex cores lie almost parallel to the blade chord, the interaction is characterized by a two-stage response associated with the sequential passage of the two cores. Conversely, when the cores lie on a plane that is almost perpendicular to the blade chord, the response is similar to that of a single vortex interaction. In all cases, the normal force response is consistent with the distribution of vertical velocity in the flow field of the vortex system. The pitching moment response, on the other hand, depends on the localized suction associated with the vortex cores as they traverse the blade chord

A new stall-onset criterion for low speed dynamic-stall

The Beddoes/Leishman dynamic-stall model has become one of the most popular for the provision of unsteady aerofoil data embedded in much larger codes. The underlying modeling philosophy was that it should be based on the best understanding, or description, of the associated physical phenomena. Even though the model was guided by the flow physics, it requires significant empirical inputs in the form of measured coefficients and constants. Beddoes provided these for a Mach number range of 0.3–0.8. This paper considers one such input for a Mach number of 0.12, where, from the Glasgow data, it is shown that the current stall-onset criterion, and subsequent adjustments, yield problematic results. A new stall criterion is proposed and developed in the best traditions of the model. It is shown to be very capable of reconstructing the Glasgow's data for stall onset both the ramp-up and oscillatory tests

Delay of dynamic stall using pulsed air-jet vortex generators

No abstract available

Control of rotorcraft retreating blade stall using air-jet vortex generators

A series of low-speed wind tunnel tests were carried out on an oscillating airfoil fitted with two rows of air-jet vortex generators (AJVGs). The airfoil used had an RAE 9645 section and the two spanwise arrays of AJVGs were located at x/c=0.12 and 0.62. The devices and their distribution were chosen to assess their ability to modify/control dynamic stall; the goal being to enhance the aerodynamic performance of helicopter rotors on the retreating blade side of the disc. The model was pitched about the quarter chord with a reduced frequency (k) of 0.1 in a sinusoidal motion defined by a=15o+10sin_ t. The measured data indicate that, for continuous blowing from the front row of AJVGs with a momentum blowing coefficient (C μ) greater than 0.008, modifications to the stalling process are encouraging. In particular, the pitching moment behavior exhibits delayed stall and there is a marked reduction in the normal force hysteresis

Cell fueling and metabolic energy conservation in synthetic cells

We aim for a blue print for synthesizing complex subcellular systems from molecular components and ultimately for constructing life. Without comprehensive instructions and design principles we rely on simple reaction routes to operate the essential functions of life. The first forms of synthetic life will not make every building block for polymers de novo via complex pathways, rather they will be fed with amino acids, fatty acids and nucleotides. Controlled energy supply is crucial for any synthetic cell, no matter how complex. Here, we describe the simplest pathways for efficient generation of ATP and electrochemical ion gradients. We estimated the demand for ATP by polymer synthesis and maintenance processes in small cell-like systems, and we describe circuits to control the needs for ATP. We also present fluorescence-based sensors for pH, ionic strength, excluded volume, ATP/ADP, and viscosity, which allow monitoring and tuning of the major physicochemical conditions inside cells

Diversity within Italian Cheesemaking Brine-Associated Bacterial Communities Evidenced by Massive Parallel 16S rRNA Gene Tag Sequencing

This study explored the bacterial diversity of brines used for cheesemaking in Italy, as well as their physicochemical characteristics. In this context, 19 brines used to salt soft, semi-hard, and hard Italian cheeses were collected in 14 commercial cheese plants and analyzed using a culture-independent amplicon sequencing approach in order to describe their bacterial microbiota. Large NaCl concentration variations were observed among the selected brines, with hard cheese brines exhibiting the highest values. Acidity values showed a great variability too, probably in relation to the brine use prior to sampling. Despite their high salt content, brine microbial loads ranged from 2.11 to 6.51 log CFU/mL for the total mesophilic count. Microbial community profiling assessed by 16S rRNA gene sequencing showed that these ecosystems were dominated by Firmicutes and Proteobacteria, followed by Actinobacteria and Bacteroidetes. Cheese type and brine salinity seem to be the main parameters accountable for brine microbial diversity. On the contrary, brine pH, acidity and protein concentration, correlated to cheese brine age, did not have any selective effect on the microbiota composition. Nine major genera were present in all analyzed brines, indicating that they might compose the core microbiome of cheese brines. Staphylococcus aureus was occasionally detected in brines using selective culture media. Interestingly, bacterial genera associated with a functional and technological use were frequently detected. Indeed Bifidobacteriaceae, which might be valuable probiotic candidates, and specific microbial genera such as Tetragenococcus, Corynebacterium and non-pathogenic Staphylococcus, which can contribute to sensorial properties of ripened cheeses, were widespread within brines. \ua9 2017 Marino, Innocente, Maifreni, Mounier, Cobo-D\uedaz, Coton, Carraro and Cardazzo

Pancreatic hyperamylasemia during acute gastroenteritis: incidence and clinical relevance

BACKGROUND: Many case reports of acute pancreatitis have been reported but, up to now, pancreatic abnormalities during acute gastroenteritis have not been studied prospectively. OBJECTIVES: To evaluate the incidence and the clinical significance of hyperamylasemia in 507 consecutive adult patients with acute gastroenteritis. METHODS: The clinical significance of hyperamylasemia, related predisposing factors and severity of gastroenteritis were assessed. RESULTS: Hyperamylasemia was detected in 10.2 % of patients studied. Although amylasemia was found over four times the normal values in three cases, the clinical features of acute pancreatitis were recorded in only one case (0.1%). Hyperamylasemia was more likely (17%) where a microorganism could be identified in the stools (p < 0.01). Among patients with positive stool samples, Salmonella spp. and in particular S. enteritidis, was the microorganism most frequently associated with hyperamylasemia [17/84 (20.2 %) and 10/45 (22.2%), respectively], followed by Rotavirus, Clostridium difficile and Campylobacter spp. Patients with hyperamylasemia had more severe gastroenteritis with an increased incidence of fever (80 % vs 50.6 %, O.R. 3.0; P < 0.01), dehydration (18% vs 8.5%; O.R. 2.5; P < 0.05), and a higher mean number of evacuations per day (9.2 vs 7.5; P < 0.05) than those with amylasemia in the normal range. Hyperamylasemia was significantly associated with cholelithiasis, (30.0 % vs 10.7%, O.R. 3.5; P < 0.01) and chronic gastritis or duodenal ulceration (22.0 % vs 10.2%, O.R. 2.4, P < 0.05). CONCLUSIONS: Hyperamylasemia is relatively frequent, and is associated with severe gastroenteritis. However, acute pancreatitis in the setting of acute gastroenteritis, is a rare event