Turbulence in a localized puff in a pipe

This is the author accepted manuscript. The final version is available from Springer Verlag via the DOI in this recordWe have performed direct numerical simulations of a spatio-temporally intermittent flow in a pipe for Rem = 2250. From previous experiments and simulations of pipe flow, this value has been estimated as a threshold when the average speeds of upstream and downstream fronts of a puff are identical (Barkley et al., Nature 526, 550–553, 2015; Barkley et al., 2015). We investigated the structure of an individual puff by considering three-dimensional snapshots over a long time period. To assimilate the velocity data, we applied a conditional sampling based on the location of the maximum energy of the transverse (turbulent) motion. Specifically, at each time instance, we followed a turbulent puff by a three-dimensional moving window centered at that location. We collected a snapshot-ensemble (10000 time instances, snapshots) of the velocity fields acquired over T = 2000D/U time interval inside the moving window. The cross-plane velocity field inside the puff showed the dynamics of a developing turbulence. In particular, the analysis of the cross-plane radial motion yielded the illustration of the production of turbulent kinetic energy directly from the mean flow. A snapshot-ensemble averaging over 10000 snapshots revealed azimuthally arranged large-scale (coherent) structures indicating near-wall sweep and ejection activity. The localized puff is about 15-17 pipe diameters long and the flow regime upstream of its upstream edge and downstream of its leading edge is almost laminar. In the near-wall region, despite the low Reynolds number, the turbulence statistics, in particular, the distribution of turbulence intensities, Reynolds shear stress, skewness and flatness factors, become similar to a fully-developed turbulent pipe flow in the vicinity of the puff upstream edge. In the puff core, the velocity profile becomes flat and logarithmic. It is shown that this “fully-developed turbulent flash” is very narrow being about two pipe diameters long

Nanotribological Investigation of Polymer Brushes with Lithographically Defined and Systematically Varying Grafting Densities.

Following controlled photodeprotection of a 2-nitrophenylpropyloxycarbonyl-protected (aminopropyl)triethoxysilane (NPPOC-APTES) film and subsequent derivatization with a bromoester-based initiator, poly(2-(methacryloyloxy)ethylphosphorylcholine) (PMPC) brushes with various grafting densities were grown from planar silicon substrates using atom transfer radical polymerization (ATRP). The grafting density correlated closely with the extent of deprotection of the NPPOC-APTES. The coefficient of friction for such PMPC brushes was measured by friction force microscopy in water and found to be inversely proportional to the grafting density due to the osmotic pressure that resists deformation. Deprotection of NPPOC-APTES via near-field photolithography using a range of writing rates enabled the fabrication of neighboring nanoscopic polymeric structures with dimensions ranging from 100 to 1000 nm. Slow writing rates enable complete deprotection to occur; hence, polymer brushes are formed with comparable thicknesses to macroscopic brushes grown under the same conditions. However, the extent of deprotection is reduced at higher writing rates, resulting in the concomitant reduction of the brush thickness. The coefficient of friction for such polymer brushes varied smoothly with brush height, with lower coefficients being obtained at slower writing rate (increasing initiator density) because the solvated brush layer confers greater lubricity. However, when ultrasharp probes were used for nanotribological measurements, the coefficient of friction increased with brush thickness. Under such conditions, the radius of curvature of the tip is comparable to the mean spacing between brush chains, allowing the probe to penetrate the brush layer leading to a relatively large contact area

Factors associated with the use of complementary and alternative medicines for prostate cancer by long-term survivors

© 2018 Egger et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Objective To assess whether the use of complementary and alternative medicines therapies (CAMs) for prostate cancer and/or its treatment side effects by long-term survivors is associated with selected socio-demographic, clinical, health-related quality-of-life (HRQOL) and/or psychological factors. Design, setting and participants The Prostate Cancer Care and Outcomes Study (PCOS) is a population-based cohort study of men with prostate cancer who were aged less than 70 years at diagnosis in New South Wales, Australia. Included in these analyses were men who returned a 10-year follow-up questionnaire, which included questions about CAM use. Methods Validated instruments assessed patient’s HRQOL and psychological well-being. Poisson regression with robust variance estimation was used to estimate the adjusted relative risks of current CAM use for prostate cancer according to socio-demographic, clinical, HRQOL and psychological factors. Results 996 of 1634 (61%) living PCOS participants completed the 10-year questionnaire. Of these 996 men, 168 (17%) were using CAMs for prostate cancer and 525 (53%) were using CAMs for any reason (including prostate cancer). Those using CAM for prostate cancer were more likely to be regular or occasional support group participants (vs. no participation RR = 2.02; 95%CI 1.41–2.88), born in another country (vs. Australian born RR = 1.59; 95%CI 1.17–2.16), have received androgen deprivation treatment (ADT) since diagnosis (RR = 1.60; 95%CI 1.12–2.28) or in the past two years (RR = 2.34; 95%CI 1.56–3.52). CAM use was associated with greater fear of recurrence (RR = 1.29; 95%CI 1.12–1.48), cancer-specific distress (RR = 1.15; 95%CI 1.01–1.30), cancer-specific hyperarousal (RR = 1.17; 95%CI 1.04–1.31), cancer locus of control (RR = 1.16; 95%CI 1.01–1.34) and less satisfaction with medical treatments (RR = 0.86; 95%CI 0.76–0.97), but not with intrusive thinking, cognitive avoidance, depression, anxiety or any HRQOL domains. Conclusions In this study, about one in six long term prostate cancer survivors used CAMs for their prostate cancer with use centred around ADT, country of birth, distress, cancer control, fear of recurrence and active help seeking

Factors associated with the use of diet and the use of exercise for prostate cancer by long-term survivors

© 2019 Hughes et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Objective To assess the use of diet and the use of exercise for prostate cancer (and/or its treatments’ side effects) by long-term survivors and whether such use is associated with selected socio-demographic, clinical, health-related quality-of-life (HRQOL) and psychological factors. Design, setting and participants Population-based cohort study in New South Wales, Australia of prostate cancer survivors aged <70 years at diagnosis and who returned a 10-year follow-up questionnaire. Methods Validated instruments assessed patient’s HRQOL and psychological well-being. Poisson regression was used to estimate adjusted relative proportions (RRs) of prostate cancer survivor groups who were currently eating differently (‘using diet’) or exercise differently (‘using exercise’) to help with their prostate cancer. Results 996 (61.0% of 1634) participants completed the 10-year questionnaire of whom 118 (11.8%; 95%CI[9.8–13.9]) were using diet and 78 (7.8%; 95%CI[6.2–9.5]) were using exercise to help with their prostate cancer. Men were more likely to use diet or use exercise for prostate cancer if they were younger (p-trend = 0.020 for diet, p-trend = 0.045 for exercise), more educated (p-trend<0.001, p-trend = 0.011), support group participants (p-nominal<0.001, p-nominal = 0.005), had higher Gleason score at diagnosis (p-trend<0.001, p-trend = 0.002) and had knowledge of cancer spread (p-nominal = 0.002, p-nominal = 0.001). Use of diet was also associated with receipt of androgen deprivation therapy (RR = 1.59; 95%CI[1.04–2.45]), a greater fear of cancer recurrence (p-trend = 0.010), cognitive avoidance (p-trend = 0.025) and greater perceived control of cancer course (p-trend = 0.014). Use of exercise was also associated with receipt of prostatectomy (RR = 2.02; 95%CI[1.12–3.63]), receipt of androgen deprivation therapy (RR = 2.20; 95%CI[1.34–3.61]) and less satisfaction with medical treatments (p-trend = 0.044). Conclusions Few long-term prostate cancer survivors use diet or exercise to help with their prostate cancer. Survivors may benefit from counselling on the scientific evidence supporting healthy eating and regular exercise for improving quality-of-life and cancer-related outcomes

Spectral/hp element simulation of flow past a Formula One front wing: validation against experiments

Emerging commercial and academic tools are regularly being applied to the design of road and race cars, but there currently are no well-established benchmark cases to study the aerodynamics of race car wings in ground effect. In this paper we propose a new test case, with a relatively complex geometry, supported by the availability of CAD model and experimental results. We refer to the test case as the Imperial Front Wing, originally based on the front wing and endplate design of the McLaren 17D race car. A comparison of different resolutions of a high fidelity spectral/hp element simulation using under-resolved DNS/implicit LES approach with fourth and fifth polynomial order is presented. The results demonstrate good correlation to both the wall-bounded streaklines obtained by oil flow visualization and experimental PIV results, correctly predicting key characteristics of the time-averaged flow structures, namely intensity, contours and locations. This study highlights the resolution requirements in capturing salient flow features arising from this type of challenging geometry, providing an interesting test case for both traditional and emerging high-fidelity simulations

Fast Barycentric-Based Evaluation Over Spectral/hp Elements

This is the final version. Available on open access from Springer via the DOI in this recordCode Availability: All code is available in the Nektar++ repository at https://gitlab.nektar.infoAs the use of spectral/hp element methods, and high-order finite element methods in general, continues to spread, community efforts to create efficient, optimized algorithms associated with fundamental high-order operations have grown. Core tasks such as solution expansion evaluation at quadrature points, stiffness and mass matrix generation, and matrix assembly have received tremendous attention. With the expansion of the types of problems to which high-order methods are applied, and correspondingly the growth in types of numerical tasks accomplished through high-order methods, the number and types of these core operations broaden. This work focuses on solution expansion evaluation at arbitrary points within an element. This operation is core to many postprocessing applications such as evaluation of streamlines and pathlines, as well as to field projection techniques such as mortaring. We expand barycentric interpolation techniques developed on an interval to 2D (triangles and quadrilaterals) and 3D (tetrahedra, prisms, pyramids, and hexahedra) spectral/hp element methods. We provide efficient algorithms for their implementations, and demonstrate their effectiveness using the spectral/hp element library Nektar++ by running a series of baseline evaluations against the ‘standard’ Lagrangian method, where an interpolation matrix is generated and matrix-multiplication applied to evaluate a point at a given location. We present results from a rigorous series of benchmarking tests for a variety of element shapes, polynomial orders and dimensions. We show that when the point of interest is to be repeatedly evaluated, the barycentric method performs at worst 50% slower, when compared to a cached matrix evaluation. However, when the point of interest changes repeatedly so that the interpolation matrix must be regenerated in the ‘standard’ approach, the barycentric method yields far greater performance, with a minimum speedup factor of 7×. Furthermore, when derivatives of the solution evaluation are also required, the barycentric method in general slightly outperforms the cached interpolation matrix method across all elements and orders, with an up to 30% speedup. Finally we investigate a real-world example of scalar transport using a non-conformal discontinuous Galerkin simulation, in which we observe around 6× speedup in computational time for the barycentric method compared to the matrix-based approach. We also explore the complexity of both interpolation methods and show that the barycentric interpolation method requires O(k) storage compared to a best case space complexity of O(k2) for the Lagrangian interpolation matrix method.Engineering and Physical Sciences Research Council (EPSRC)ARONational Science Foundation (NSF