Callum Atkinson

Towards 3C-3D digital holographic fluid velocity vector field measurement-tomographic digital holographic PIV (Tomo-HPIV)

Most unsteady and/or turbulent flows of geophysical and engineering interest have a highly three-dimensional (3D) complex topology and their experimental investigation is in pressing need of quantitative velocity measurement methods that are robust and can provide instantaneous 3C-3D velocity field data over a significant volumetric domain of the flow. This paper introduces and demonstrates a new method that uses multiple digital CCD array cameras to record in-line digital holograms of the same volume of seed particles from multiple orientations. This technique uses the same basic equipment as Tomo-PIV minus the camera lenses, it overcomes the depth-of-field problem of digital in-line holography and does not require the complex optical calibration of Tomo-PIV. The digital sensors can be oriented in an optimal manner to overcome the depth-of-field limitation of in-line holograms recorded using digital CCD or CMOS array cameras, resulting in a 3D reconstruction of the seed particles within the volume of interest, which can subsequently be analysed using 3D cross-correlation PIV analysis to yield a 3C-3D velocity field. A demonstration experiment of Tomo-HPIV using uniform translation with nominally 11 µm diameter seed particles shows that the 3D displacement derived from 3D cross-correlation Tomo-HPIV analysis can be measured within 5% of the imposed uniform translation, where the imposed uniform translation has an estimated standard uncertainty of 4.3%. So this paper proposes a multi-camera digital holographic imaging 3C-3D PIV method, which is identified as tomographic digital holographic PIV or Tomo-HPIV.

Ultra-high-speed tomographic digital holographic velocimetry in supersonic particle-laden jet flows

Ultra-high-speed tomographic digital holographic velocimetry is used to measure the three-component, three-dimensional velocities and trajectories of micron-sized particles in a supersonic underexpanded jet flow. In high-speed digital in-line holography, the depth resolution or depth of field is severely restricted by the limited resolution of the digital recording array, which leads to significant elongation of the reconstructed particles in the depth direction. It is shown that by applying tomographic digital holography, this limitation imposed by the high-speed recording array is relaxed and that the accurate reconstruction of 3D particle intensities is possible without the depth-of-field problem. This method is demonstrated by measuring 110 ?m solid particles suspended in a ?mildly underexpanded? jet with a nozzle pressure ratio of 2.0. The interference pattern produced by both the suspended particles and the density gradient field is simultaneously recorded by two digital high-speed cameras at a frame rate of 500?000 fps with an exposure time of 250?ns. Individual object fields are reconstructed by tomographic holography and the velocity of the micron-sized particles is analyzed by cross-correlation particle tracking velocimetry. The accuracy of the particle velocity measurements is estimated to be within 5 m?s?1 or approximately 4.5% of the particle velocity. In addition, the method is used to study the particle?flow interactions by means of coherent imaging, which reveals a complex interaction between the micron-sized particles and the flow structure of this high-speed 3D unsteady turbulent particle-laden flow.

High spatial range velocity measurements in a high Reynolds number turbulent boundary layer

Here, we detail and analyse a multi-resolution particle image velocity measurement that resolves the wide range of scales prevalent in a zero pressure gradient turbulent boundary layer at high Reynolds numbers (up to Reτ ≈ 20 000). A unique configuration is utilised, where an array of eight high resolution cameras at two magnification levels are used simultaneously to obtain a large field of view, while still resolving the smaller scales prevalent in the flow. Additionally, a highly magnified field of view targeted at the near wall region is employed to capture the viscous sublayer and logarithmic region, with a spatial resolution of a few viscous length scales. Flow statistics from these measurements show good agreement with prior, well resolved hot-wire anemometry measurements. Analysis shows that the instantaneous wall shear stress can be reliably computed, which is historically known to be challenging in boundary layers. A statistical assessment of the wall shear stress shows good agreement with exist...

Validation of International Society of Urological Pathology (ISUP) grading for prostatic adenocarcinoma in thin core biopsies using TROG 03.04 ‘RADAR’ trial clinical data

Summary In 2014 a consensus conference convened by the International Society of Urological Pathology (ISUP) adopted amendments to the criteria for Gleason grading and scoring (GS) for prostatic adenocarcinoma. The meeting defined a modified grading system based on 5 grading categories (grade 1, GS 3+3; grade 2, GS 3+4; grade 3, GS 4+3; grade 4, GS 8; grade 5, GS 9–10). In this study we have evaluated the prognostic significance of ISUP grading in 496 patients enrolled in the TROG 03.04 RADAR Trial. There were 19 grade 1, 118 grade 2, 193 grade 3, 88 grade 4 and 79 grade 5 tumours in the series, with follow-up for a minimum of 6.5 years. On follow-up 76 patients experienced distant progression of disease, 171 prostate specific antigen (PSA) progression and 39 prostate cancer deaths. In contrast to the 2005 modified Gleason system (MGS), the hazards of the distant and PSA progression endpoints, relative to grade 2, were significantly greater for grades 3, 4 and 5 of the 2014 ISUP grading scheme. Comparison of predictive ability utilising Harrells concordance index, showed 2014 ISUP grading to significantly out-perform 2005 MGS grading for each of the three clinical endpoints.

'GAP' in radiotherapy services in Australia and New Zealand in 2009

Aim: In this study we estimated (a) the number of linear accelerators required in Australia and New Zealand to achieve a 52.3% treatment rate; (b) the ‘GAP’ between the actual and required number of linear accelerators; c) the number of persons not treated (PNT), premature deaths (PD) and years of life lost (YLL) as a result of the ‘GAP’; and (d) to review the actions being taken by health jurisdictions in Australia and in New Zealand to address the ‘GAP’ and reach the 52.3% treatment rate.

Lagrangian evolution of the invariants of the velocity gradient tensor in a turbulent boundary layer

Lagrangian mean evolution of the invariants of the velocity gradient tensor in different regions of a turbulent boundary layer is investigated using data from a direct numerical simulation of a zero pressure gradient turbulent boundary layer. Conditional mean trajectories (CMTs) are calculated for the evolution of invariants based on their mean rate of change, conditioned on their location in the (RA, QA) plane, which determines the focal or non-focal nature of flow at that point. CMTs are calculated over a larger range of gradients than previously reported boundary layer measurements and show a distinct difference in topological evolution depending on the resolution and the range of invariants considered. In the present case, CMTs for strong gradients in all regions of the boundary layer pass around a focus at the origin and asymptote towards the right-hand side of a saddle point located near the right-hand side of the line dividing unstable focal and unstable nodal structures, consistent with viscous di...

Randomised, placebo-controlled, crossover trial of sildenafil citrate in the treatment of erectile dysfunction following external beam radiation treatment of prostate cancer

Erectile dysfunction (ED) commonly affects the quality of life of men after treatment of prostate cancer. We conducted a placebo‐controlled, crossover randomised trial to assess the efficacy and tolerability of sildenafil citrate in the treatment of ED developing after external beam radiation treatment (EBRT) of localized prostate cancer. Sixty‐six patients who had developed ED following radiation treatment agreed to participate and were allocated to sildenafil or placebo to be taken prior to four sexual attempts. In the crossover period, subjects received the alternative tablet for a further four attempts. Allocation was centrally randomized, and researchers and patients were both blinded to the trial arm. Efficacy was assessed using the International Index of Erectile Function (IIEF) questionnaire and with a separate global efficacy question. Forty‐three subjects completed the study. There was a significant increase in mean scores from baseline for all domains of the IIEF with sildenafil compared with placebo (P < 0.001). Affirmative response to the global efficacy question was more common after taking sildenafil compared with placebo. In approximately half of the patients, the improvement in the erectile function domain score corresponded to a moderate improvement in ED (e.g. success ‘sometimes’ to ‘most times’). Sildenafil was associated with mild flushing, nasal stuffiness or indigestion in 8–10% patients and moderate flushing in 10%. The current study adds to the evidence that phosphodiesterase inhibitors are an effective and well‐tolerated treatment for ED after EBRT for prostate cancer.

Investigation of wall-bounded turbulent flow using Dynamic mode decomposition

Dynamics mode decomposition (DMD) which is a method to construct a linear mapping describing the dynamics of a given time-series of any quantities is applied to the analysis of a turbulent channel flow. The flow fields are generated by direct numerical simulations for the friction Reynolds number Re? = 190. The time-series of the flow fields in a short time-interval in the order of the wall-unit time-scale and in a small spatial domain that encloses a single near-wall structure are used as the inputs to DMD. In some datasets, linearly growing modes that seem to contribute to the well-known self-sustained cycle of the flow structures near the wall are detected.

Extensive characterisation of a high Reynolds number decelerating boundary layer using advanced optical metrology

ABSTRACT Over the last years, the observation of large-scale structures in turbulent boundary layer flows has stimulated intense experimental and numerical investigations. Nevertheless, partly due to the lack of comprehensive experimental data at sufficiently high Reynolds number, our understanding of turbulence near walls, especially in decelerating situations, is still quite limited. The aim of the present contribution is to combine the equipment and skills of several teams to perform a detailed characterisation of a large-scale turbulent boundary layer under adverse pressure gradient. Extensive particle image velocimetry (PIV) measurements are performed, including a set-up with 16 sCMOS cameras allowing the characterisation of the boundary layer on 3.5 m, stereo PIV and high resolution near wall measurements. In this paper, detailed statistics are presented and discussed, boundary conditions are carefully characterised, making this experiment a challenging test case for numerical simulation.

Measuring dynamic phenomena at the sub-micron scale

Measuring the spatio-temporal evolution of dynamic phenomena at sub-micron level is non-trivial due to the diffraction limit of optical systems. This paper describes a technique which allows imaging of sub-micron features of fluid-based phenomena, specifically the determination of their velocity and trajectory.