Permuted proper orthogonal decomposition for analysis of advecting structures

Flow data are often decomposed using proper orthogonal decomposition (POD) of the space–time separated form, $\boldsymbol {q}'\left (\boldsymbol {x},t\right )=\sum _j a_j\left (t\right )\boldsymbol {\phi }_j\left (\boldsymbol {x}\right )$ , which targets spatially correlated flow structures in an optimal manner. This paper analyses permuted POD (PPOD), which decomposes data as $\boldsymbol {q}'\left (\boldsymbol {x},t\right )=\sum _j a_j\left (\boldsymbol {n}\right )\boldsymbol {\phi }_j\left (s,t\right )$ , where $\boldsymbol {x}=(s,\boldsymbol {n})$ is a general spatial coordinate system, $s$ is the coordinate along the bulk advection direction and $\boldsymbol {n}=(n_1,n_2)$ are along mutually orthogonal directions normal to the advection characteristic. This separation of variables is associated with a fundamentally different inner product space for which PPOD is optimal and targets correlations in $s,t$ space. This paper presents mathematical features of PPOD, followed by analysis of three experimental datasets from high-Reynolds-number, turbulent shear flows: a wake, a swirling annular jet and a jet in cross-flow. In the wake and swirling jet cases, the leading PPOD and space-only POD modes focus on similar features but differ in convergence rates and fidelity in capturing spatial and temporal information. In contrast, the leading PPOD and space-only POD modes for the jet in cross-flow capture completely different features – advecting shear layer structures and flapping of the jet column, respectively. This example demonstrates how the different inner product spaces, which order the PPOD and space-only POD modes according to different measures of variance, provide unique ‘lenses’ into features of advection-dominated flows, allowing complementary insights.

1394Better Cardiac Care Data Linkage Project: utilising cross-jurisdictional data to improve patient-flow capture

Background For patients experiencing acute myocardial infarction (AMI), particularly ST-elevation myocardial infarction (STEMI), timely revascularisation is important to optimise prognosis. The AMI patient journey often involves presentation to the closest appropriate facility and transfers between hospitals, including across jurisdictions. The Better Cardiac Care (BCC) dataset consists of cross-jurisdictional linked ambulance, emergency, hospital, outpatient, deaths, Medicare and Pharmaceutical Benefits Scheme records for residents of New South Wales (NSW), Australia. This dataset will be updated annually. Methods The BCC dataset comprises 332 million records, from 18 datasets, across 6 jurisdictions. For NSW residents hospitalised for STEMI between 2013 to 2018, we compared the number of STEMI hospitalisations, the proportion of patients receiving revascularisation procedures, and the time to procedures using only NSW records versus records from all jurisdictions and Medicare Benefits Scheme. Results Compared with NSW hospital data, including data from other jurisdictions increased the ascertainment of STEMI hospitalisations by 8.0% and procedures by 11.2% for NSW residents. This increase was greatest for residents living near state borders, increasing the number of STEMI hospitalisations by up to 210% and the percentage receiving procedures by up to 70%. Conclusions Cross-jurisdictional data is essential to understand patient journeys of residents who live in border areas and to evaluate patient care for STEMI and AMI more broadly. Key messages The BCC dataset is a vital asset that enables a more comprehensive view of care for AMI than has been possible to date.

Leakiness and flow capture ratio of insect pectinate antennae

The assumption that insect pectinate antennae, which are multi-scale organs spanning over four orders of magnitude in size among their different elements, are efficient at capturing sexual pheromones is commonly made but rarely thoroughly tested. Leakiness, i.e. the proportion of air that flows within the antenna and not around it, is a key parameter which depends on both the macro- and the microstructure of the antenna as well as on the flow velocity. The effectiveness of a structure to capture flow and hence molecules is a trade-off between promoting large leakiness in order to have a large portion of the flow going through it and a large effective surface area to capture as much from the flow as possible, therefore leading to reduced leakiness. The aim of this work is to measure leakiness in 3D-printed structures representing the higher order structure of an antenna, i.e. the flagellum and the rami, with varying densities of rami and under different flow conditions. The male antennae of the moth Samia cynthia (Lepidoptera: Saturniidae) were used as templates. Particle image velocimetry in water and oil using 3D-printed scaled-up surrogates enabled us to measure leakiness over a wide range of equivalent air velocities, from 0.01 m s −1 to 5 m s −1 , corresponding to those experienced by the moth. We observed the presence of a separated vortex ring behind our surrogate structures at some velocities. Variations in the densities of rami enabled us to explore the role of the effective surface area, which we assume to permit equivalent changes in the number of sensilla that host the chemical sensors. Leakiness increased with flow velocity in a sigmoidal fashion and decreased with rami density. The flow capture ratio, i.e. the leakiness multiplied by the effective surface area divided by the total surface area, embodies the above trade-off. For each velocity, a specific structure leads to a maximum flow capture ratio. There is thus not a single pectinate architecture which is optimal at all flow velocities. By contrast, the natural design seems to be robustly functioning for the velocity range likely to be encountered in nature.

Framework for estimation of nacelle drag on isolated aero-engines with separate jets

Typically, the evaluation of nacelle drag in preliminary design is required to find an overall optimum engine cycle and flight trajectory. This work focuses on the drag characteristics of aero-engine nacelles with separate jet exhausts. The main body of analysis comes from 3D numerical simulations. A new near-field method to compute the post-exit force of a nacelle is presented and evaluated. The effects of the engine size, Mach number, mass flow capture ratio and angle of attack are assessed. The results obtained from the numerical assessments were used to evaluate conventional reduced-order models for the estimation of nacelle drag. Within this context, the effect of the engine size is typically estimated by the scaling ratio between the maximum areas and Reynolds numbers. The effect of the angle of attack on nacelle drag is mostly a function of the nacelle geometry and angle of attack. In general, typical low-order models based on skin friction and form factor can underestimate the friction drag by up to 15% at cruise operating point. Similarly, reduced-order models based solely on Reynolds number, and Mach number can underestimate the overall nacelle drag by up to 74% for free stream Mach number larger than the drag rise Mach number.

The Politics of Sound

This essay considers the politics of sound on the model of migration and borders, that is, as concerning flows and codes, inclusions and exclusions. A rigorously materialist analysis of sound would consider it as one of the many flows that constitute nature and culture. On this model, the fundamental function of society is to code flows, that is, to intercept them, organize them, regulate them, channel them in particular directions, impose meanings and limits on them, and the like. A politics of sound, then, would consider the local and global circulation of sound, its flow, capture, and blockage, the forces (technological, legal, economic, cultural, social, moral, linguistic, racial, gendered, etc.) that accelerate, decelerate, and otherwise inflect it. It would ask: What are the forces that generate sonic flows and propel their movement and circulation? What are the forces that constrain this sonic flux sufficiently to enable it to congeal into languages, musical styles, or scenes? And what are the forces that block, annul, or cancel these sonic flows?

Electroosmotic flow driven microfluidic device for bacteria isolation using magnetic microbeads

The presence of bacterial pathogens in water can lead to severe complications such as infection and food poisoning. This research proposes a point-of-care electroosmotic flow driven microfluidic device for rapid isolation and detection of E. coli in buffered solution (phosphate buffered saline solution). Fluorescent E. coli bound to magnetic microbeads were driven through the microfluidic device using both constant forward flow and periodic flow switching at concentrations ranging from 2 × 105 to 4 × 107 bacteria/mL. A calibration curve of fluorescent intensity as a function of bacteria concentration was created using both constant and switching flow, showing an increase in captured fluorescent pixel count as concentration increases. In addition, the use of the flow switching resulted in a significant increase in the capture efficiency of E. coli, with capture efficiencies up to 83% ± 8% as compared to the constant flow capture efficiencies (up to 39% ± 11%), with a sample size of 3 µL. These results demonstrate the improved performance associated with the use of the electroosmotic flow switching system in a point-of-care bacterial detection assay.