ORCID Profile
0000-0002-6922-848X
Current Organisation
University of Adelaide
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Publisher: Elsevier BV
Date: 07-2009
Publisher: Elsevier BV
Date: 06-2017
Publisher: Author(s)
Date: 2016
DOI: 10.1063/1.4949167
Publisher: International Solar Energy Society
Date: 2016
Publisher: Springer Science and Business Media LLC
Date: 25-03-2015
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 09-2013
Publisher: Elsevier BV
Date: 06-2019
Publisher: American Physical Society (APS)
Date: 13-06-2005
Publisher: Elsevier BV
Date: 08-2014
Publisher: Elsevier BV
Date: 07-2004
Publisher: Elsevier BV
Date: 2011
Publisher: AIP Publishing
Date: 12-2004
DOI: 10.1063/1.1824138
Abstract: An experimental investigation of a precessing jet issuing from a mechanically rotating nozzle directed at an angle of α=45° relative to the axis of rotation is reported. Both conventional and conditional statistics of the velocity field of the jet were measured using a combined hot-wire and cold-wire (to identify any reverse flow) probe. Three distinct values (≈0.005, 0.01, and 0.02) of the precession Strouhal number Stp (≡ rotation frequency × nozzle diameter / jet exit bulk velocity) were used to assess the effect of varying Stp. The measurements reveal that the Strouhal number in general has significant influence on the entire mixing field generated by a precessing jet. The occurrence of precession at all the Strouhal numbers of investigation produces a central recirculation zone at x⩽7d, where x is a distance measured from the rotating nozzle exit. A critical Strouhal number, i.e., Stp,cr≈0.008 for the present case, is identified: at Stp⩾Stp,cr the core jet converges to the axis of rotation while at Stp⩾Stp,cr it does not. The characteristics of the turbulent flow in the near and intermediate regions are quite different and depend upon the magnitude of Stp. The near-field region, x∕d⩽10–15, is dominated by a regime of global precession of the entire jet. As a result, the large-scale entrainment of the ambient fluid is substantially enhanced while the fine-scale turbulent mixing is suppressed. Under the supercritical regime (i.e., Stp⩾Stp,cr), the jet in the far field resembles some features of the nonprecessing counterpart. Nevertheless, significant differences still retain in the statistical properties.
Publisher: Elsevier BV
Date: 08-2015
Publisher: American Chemical Society (ACS)
Date: 10-04-2015
Publisher: SAGE Publications
Date: 12-2004
Abstract: The near field of the three-dimensional velocity field in a turbulent precessing jet diffusion flame is investigated. In the present case the precessing jet flame is generated by mechanically rotating a round jet of propane inclined at 45° relative to the axis of rotation. Three-dimensional laser Doppler anemometry enables the fully turbulent, three-dimensional velocity field of a precessing jet flame to be measured. This provides insight into the mechanisms by which the flame is stabilized and supports previous explanations of why NO x emissions are reduced and fuel efficiency is increased in industrial precessing jet gas burners. Velocity data are presented, time-averaged, and phase-averaged at the frequency of precession. The conditional phase-averaging technique enables phase-averaged velocity contours and vectors to be obtained that reveal flow patterns and structures within the flame. Time-averaging of the velocity data also reveals the presence of a reverse flow (recirculation) region between the emerging fuel jet and its spinning axis. The recirculation and high shear is associated with a rapid decay of the mean velocity, which together act to stabilize the flame in the high velocity and high shear region near to the nozzle exit. The characteristics of the velocity field of a precessing jet flame found here are compared with previous cold-flow investigations of the same flow and with other investigations of turbulent jets.
Publisher: Cambridge University Press (CUP)
Date: 19-09-2014
DOI: 10.1017/JFM.2014.496
Abstract: The first measurement of the influence of the Stokes number on the distributions of particle concentration and velocity at the exit of a long pipe are reported, together with the subsequent influence on the downstream evolution of these distributions through a particle-laden jet in co-flow. The data were obtained by simultaneous particle image velocimetry (PIV) and planar nephelometry (PN), using four cameras to provide high resolution through the first 30 jet diameters and also correction for optical attenuation. These data provide much more detailed information than is available from previous measurements. From them, a new understanding is obtained of how the Stokes number influences the flow at the jet exit plane and how this influence propagates throughout the jet.
Publisher: ASMEDC
Date: 2010
DOI: 10.1115/IHTC14-23422
Abstract: Recent advances in diagnostic methods are providing new capacity for detailed measurement of turbulent, reacting flows in which heat transfer is dominant. Radiation typically becomes dominant in flames containing soot and/or with sufficient physical size, so is important in many flames of practical significance. The presence of particles, including soot, increases the coupling between the turbulence, chemistry and radiative heat transfer processes. Particles also increase the difficulties of laser-based measurements by increasing the interferences to the signal and the attenuation of the beam. The paper reviews recent advances in techniques to measure temperature, mixture fraction, soot volume fraction, velocity, particle number density and the scattered, absorbed and transmitted components of radiation propagation through particle laden systems.
Publisher: Elsevier BV
Date: 11-2008
Publisher: ASME International
Date: 20-04-2017
DOI: 10.1115/1.4035950
Abstract: A comprehensive study on the flow structure of an ensemble-averaged fluidic precessing jet (FPJ) flow is reported. This study is based on the concepts of critical point theory, previous experimental data, and validated simulation results. The unsteady k–ω shear stress transport (SST) turbulence model was adopted for the simulation, which provided high resolution flow details. The numerical model successfully reproduced the four main flow features of the FPJ flow. The predicted equivalent diameter and the centerline velocity of the phase-averaged FPJ flow were compared against the measured results and achieved reasonable agreement. The streamlines, velocity, and vorticity contours in a series of cross-sectional planes are presented. The calculated streamlines at the surfaces of the nozzle and the center-body (CB) are compared with previously deduced surface flow patterns. With these methods, a vortex skeleton with six main vortex cores of the FPJ flow within the nozzle is identified for the first time. This skeleton, which is illustrated diagramatically, is deduced to be responsible for the jet precession.
Publisher: Informa UK Limited
Date: 08-2005
Publisher: Elsevier BV
Date: 11-2007
Publisher: Elsevier BV
Date: 11-2014
Publisher: Elsevier BV
Date: 03-2013
Publisher: Elsevier BV
Date: 05-2017
Publisher: Elsevier BV
Date: 11-2007
Publisher: Cambridge University Press (CUP)
Date: 10-07-2008
DOI: 10.1017/S0022112008001699
Abstract: Phase-averaged and directionally triggered digital particle image velocimetry measurements were taken in longitudinal and transverse planes in the near field of the flow emerging from a fluidic precessing jet nozzle. Measurements were performed at nozzle inlet Reynolds and Strouhal numbers of 59000 and 0.0017, respectively. Results indicate that the jet emerging from the nozzle departs with an azimuthal component in a direction opposite to that of the jet precession. In addition, the structure of the ‘flow convergence’ region, reported in an earlier study, is better resolved here. At least three unique vortex-pair regions containing smaller vortical ‘blobs’ are identified for the first time. These include a vortex-pair region originating from the foci on the downstream face of the nozzle centrebody, a vortex-pair region shed from the edge of the centrebody and a vortex-pair region originating from the downstream surface of the nozzle exit lip.
Publisher: ASME International
Date: 29-06-2001
DOI: 10.1115/1.1412460
Abstract: The differences in mixing performance between axisymmetric turbulent jets issuing from three common types of nozzle, viz. a contoured (or smooth contraction) nozzle, a sharp-edged orifice and a long pipe, are investigated. The investigation is carried out using both qualitative flow visualizations and quantitative measurements of the centerline passive temperature. It is revealed that the jet issuing from an orifice plate provides the greatest rate of mixing with ambient fluid, while the pipe jet has the lowest rate. Physical insight into the differences is explored using a planar imaging technique and measurements of power spectra of the fluctuating velocity.
Publisher: Elsevier BV
Date: 2017
Publisher: Elsevier BV
Date: 09-2017
Publisher: Elsevier BV
Date: 05-2003
Publisher: Elsevier BV
Date: 02-2012
Publisher: Cambridge University Press (CUP)
Date: 09-11-2016
DOI: 10.1017/JFM.2016.666
Abstract: Simultaneous measurements of particle velocity and concentration (number density) in a series of mono-disperse, two-phase turbulent jets issuing from a long, round pipe into a low velocity co-flow were performed using planar nephelometry and digital particle image velocimetry. The exit Stokes number, $Sk_{D}$ , was systematically varied over two orders of magnitude between 0.3 and 22.4, while the Reynolds number was maintained in the turbulent regime ( $10\\,000\\leqslant Re_{D}\\leqslant 40\\,000$ ). The mass loading was fixed at $\\unicode[STIX]{x1D719}=0.4$ , resulting in a flow that is in the two-way coupling regime. The results show that, in contrast to all previous work where a single Stokes number has been used to characterise fluid–particle interactions, the characteristic Stokes number in the axial direction is lower than that for the radial direction. This is attributed to the significantly greater length scales in the axial motions than in the radial ones. It further leads to a preferential response of particles to gas-phase axial velocity fluctuations, $u_{p}^{\\prime }$ , over radial velocity fluctuations, $v_{p}^{\\prime }$ . This, in turn, leads to high levels of anisotropy in the particle-phase velocity fluctuations, $u_{p}^{\\prime }/v_{p}^{\\prime } $ , throughout the jet, with $u_{p}^{\\prime }/v_{p}^{\\prime }$ increasing as $Sk_{D}$ is increased. The results also show that the region within the first few diameters of the exit plane is characterised by a process of particle reorganisation, resulting in significant particle migration to the jet axis for $Sk_{D}\\leqslant 2.8$ and away from the axis for $Sk_{D}\\geqslant 5.6$ . This migration, together with particle deceleration along the axis, causes local humps in the centreline concentration whose value can even exceed those at the exit plane.
Publisher: Elsevier BV
Date: 10-2012
Publisher: Elsevier BV
Date: 04-2017
Publisher: Springer Science and Business Media LLC
Date: 06-2003
Publisher: Elsevier BV
Date: 05-2015
Publisher: Elsevier BV
Date: 08-2007
Publisher: Elsevier BV
Date: 02-2013
Publisher: Elsevier BV
Date: 09-2011
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 2016
Publisher: Elsevier BV
Date: 12-2016
Publisher: Elsevier BV
Date: 03-2012
Publisher: Elsevier BV
Date: 08-2010
Publisher: Elsevier BV
Date: 2017
Publisher: SAGE Publications
Date: 07-2012
DOI: 10.1366/11-06553
Abstract: This paper presents the first demonstration of the pulsed laser ablation technique to seed a laminar non-reacting gaseous jet at atmospheric pressure. The focused, second harmonic from a pulsed Nd:YAG laser is used to ablate a neutral indium rod at atmospheric pressure and temperature. The ablation products generated with the new seeding method are used to seed the jet, as a marker of the scalar field. The neutral indium atoms so generated are found to be stable and survive a convection time of the order of tens of seconds before entering the interrogation region. The measurements of planar laser-induced fluorescence (PLIF) with indium and laser nephelometry measurements with the ablation products are both reported. The resulting average and root mean square (RMS) of the measurements are found to agree reasonably well although some differences are found. The results show that the pulsed laser ablation method has potential to provide scalar measurement for mixing studies.
Publisher: Elsevier BV
Date: 2017
Publisher: Elsevier BV
Date: 2014
Publisher: Springer Science and Business Media LLC
Date: 17-12-2014
Publisher: Elsevier BV
Date: 2017
Publisher: AIP Publishing
Date: 05-2019
DOI: 10.1063/1.5089904
Abstract: An experimental study is reported of the interaction between multiple isothermal jets within a cylindrical chamber under conditions relevant to a wide range of engineering applications, including the confined swirl combustors, industrial mixers, and concentrated solar thermal devices. The particle image velocimetry technique was used to investigate the swirling and precessing flows generated with four rotationally symmetric inlet pipes at a fixed nozzle Reynolds number of ReD = 10 500 for two configurations of swirl angle (5° and 15°) and two alternative tilt angles (25° and 45°). The measurements reveal three distinctive rotational flow patterns within the external recirculation zone (ERZ) and the central recirculation zone (CRZ) for these configurations. It was found that the mean and root-mean-square flow characteristics of the swirl within the chamber depend strongly on the relative significance of the ERZ and CRZ, with the swirling velocity being higher in the CRZ than that in the ERZ. A precessing vortex core was identified for all experimental conditions considered here, although its significance was less for the cases with a dominant CRZ.
Publisher: Elsevier BV
Date: 2013
Publisher: Cambridge University Press (CUP)
Date: 23-09-2022
DOI: 10.1017/JFM.2022.745
Abstract: Numerical simulations have been conducted to identify the dominant mechanism responsible for driving secondary flow motions in horizontal particle-laden pipe flows, based on an analysis of the forces acting on each phase. A four-way coupling Euler–Lagrangian approach was employed, using direct numerical simulations for the gas phase and Lagrangian particle tracking to account for the drag, gravitational and lift forces, together with the interactions that occur for both particle–wall and inter-particle collisions. The four different flow regimes, which had been identified previously as depending on various combinations of flow parameters and are characterised by the secondary flow structures of both the fluid and particle phases, were identified via varying the mass loading alone from $\\varPhi _m=0.4$ to $\\varPhi _m=1.8$ . The distribution of the ergence of Reynolds stresses was used to help characterise the classes of the secondary fluid flow. This shows that secondary fluid flows of both the first and second kinds can either exist separately or co-exist in such flows. The forces exerted on the fluid phase by the pressure gradient and fluid–particle interactions were examined qualitatively and quantitatively to identify their contribution to the secondary fluid flow motions. A similar study was also applied to the drag, lift and gravitational forces exerted on the particle phase for the secondary particle flow motions. These were found to explain the secondary flows of both the fluid and particle phases with regard to both the flow direction and magnitude, together with the interaction between the two phases.
Publisher: Elsevier BV
Date: 2017
Publisher: Optica Publishing Group
Date: 20-02-2009
DOI: 10.1364/AO.48.001237
Abstract: This work aims to advance understanding of the coupling between temperature and soot. The ability to image temperature using the two-line atomic fluorescence (TLAF) technique is demonstrated. Previous TLAF theory is extended from linear excitation into the nonlinear fluence regime. Nonlinear regime two-line atomic fluorescence (NTLAF) provides superior signal and reduces single-shot uncertainty from 250 K for conventional TLAF down to 100 K. NTLAF is shown to resolve the temperature profile across the stoichiometric envelope for hydrogen, ethylene, and natural gas flames, with deviation from thermocouple measurements not exceeding 100 K, and typically ≲30 K. Measurements in flames containing soot demonstrate good capacity of NTLAF to exclude interferences that h er most two-dimensional thermometry techniques.
Publisher: Springer Science and Business Media LLC
Date: 2001
Publisher: Elsevier BV
Date: 12-2015
Publisher: Author(s)
Date: 2016
DOI: 10.1063/1.4949029
Publisher: Elsevier BV
Date: 07-2010
Publisher: Elsevier BV
Date: 09-2010
Publisher: American Chemical Society (ACS)
Date: 03-2017
Publisher: Informa UK Limited
Date: 18-02-2008
Publisher: Elsevier BV
Date: 04-2012
Publisher: Elsevier BV
Date: 06-2017
Publisher: Elsevier BV
Date: 1998
Publisher: Elsevier BV
Date: 09-2023
Publisher: Elsevier BV
Date: 05-2015
Publisher: Elsevier BV
Date: 2018
Publisher: Author(s)
Date: 2017
DOI: 10.1063/1.4984354
Publisher: Elsevier BV
Date: 04-2017
Publisher: Elsevier BV
Date: 07-2013
Publisher: Elsevier BV
Date: 02-2016
Publisher: Elsevier BV
Date: 07-2017
Publisher: Elsevier BV
Date: 06-2017
Publisher: Springer Science and Business Media LLC
Date: 16-04-2011
Publisher: ASME International
Date: 05-04-2016
DOI: 10.1115/1.4032943
Abstract: This paper presents assessments of the sensitivity of the performance of high flux solar simulators to the key variables of conical secondary concentrators for metal halide l s, which offer complementary benefits compared with xenon arc l s. The assessment is performed for both a single-l configuration and a seven-l array, each l close-coupled with its own elliptical reflector, and then aligned with a common conical secondary concentrator. The simulation of heat flux from both the single- and the seven-l systems was performed with the Monte Carlo ray-tracing code, which was validated with the experimental results from the single-l system. The calculated heat flux at the focal plane agrees with the measured peak flux to within 5% and to within 13% of the measured half width. Calculated results also show that the addition of the secondary concentrator to the single-l system can increase the peak flux by 294% and the average flux by up to 93% within a target of 100 mm in diameter, with a corresponding reduction in total power by 15%. The conical secondary concentrator is less effective for a seven-l system, increasing the peak and average fluxes by 87.3% and 100%, respectively, within 100 mm diameter focal plane, with a corresponding reduction in total power by 48%. The model was then used to assess the sensitivity of the geometry of the secondary concentrators for both the single- and seven-l systems. The results show that the average heat flux is sensitive to the surface reflectance of the secondary concentrator, with the average flux decreasing almost linearly with the surface reflectance. The presence of the secondary cone greatly reduces the sensitivity of the concentrated heat flux to misalignment of the tilting angle of the elliptical reflector relative to the arc.
Publisher: Elsevier BV
Date: 10-2012
Publisher: AIP Publishing
Date: 2013
DOI: 10.1063/1.4776782
Abstract: A similarity analysis is presented of the momentum field of a subsonic, plane air jet over the range of the jet-exit Reynolds number Reh (≡ Ubh/υ where Ub is the area-averaged exit velocity, h the slot height, and υ the kinematic viscosity) = 1500 − 16 500. In accordance with similarity principles, the mass flow rates, shear-layer momentum thicknesses, and integral length scales corresponding to the size of large-scale coherent eddy structures are found to increase linearly with the downstream distance from the nozzle exit (x) for all Reh. The autocorrelation measurements performed in the near jet confirmed reduced scale of the larger coherent eddies for increased Reh. The mean local Reynolds number, measured on the centerline and turbulent local Reynolds number measured in the shear-layer increases non-linearly following x1/2, and so does the Taylor microscale local Reynolds number that scales as x1/4. Consequently, the comparatively larger local Reynolds number for jets produced at higher Reh causes self-preservation of the fluctuating velocity closer to the nozzle exit plane. The near-field region characterized by over-shoots in turbulent kinetic energy spectra confirms the presence of large-scale eddy structures in the energy production zone. However, the faster rate of increase of the local Reynolds number with increasing x for jets measured at larger Reh is found to be associated with a wider inertial sub-range of the compensated energy spectra, where the −5/3 power law is noted. The downstream region corresponding to the production zone persists for longer x/h for jets measured at lower Reh. As Reh is increased, the larger width of the sub-range confirms the narrower dissipative range within the energy spectra. The variations of the dissipation rate (ɛ) of turbulent kinetic energy and the Kolmogorov (η) and Taylor (λ) microscales all obey similarity relationships, $\\varepsilon h/U_{\\rm b}^3 \\sim Re_h^3$ɛh/Ub3∼Reh3, η/h ∼ Reh−3/4, and λ/h ∼ Reh−1/2. Finally, the underlying physical mechanisms related to discernible self-similar states and flow structures due to disparities in Reh and local Reynolds number is discussed.
Publisher: Elsevier BV
Date: 09-2016
Publisher: Elsevier BV
Date: 12-2019
Publisher: Elsevier BV
Date: 2015
Publisher: AIP Publishing
Date: 12-2021
DOI: 10.1063/5.0075440
Abstract: Numerical simulations of the particle-laden gas–solid flow in horizontal circular pipes have been used to identify the role of particle collision coefficients in flow regimes within it. A four-way coupling Euler–Lagrangian approach was employed, using direct numerical simulations of the gas phase and Lagrangian particle tracking to account for the drag, gravitational and lift forces, together with particle–wall and inter-particle interactions. The influences on the flow of the mass loading ratio (Φm) and of the coefficients of restitution for collisions both between particles and the wall (ep−w) and between particles (ep−p) are assessed by examining the fluid and particle velocities, particle concentration distribution, turbulence kinetic energy, static pressure, inter-phase transferred momentum, and the secondary flow motions of both the fluid and particle phases. Three dominant flow regimes that include three sub-regimes based on their secondary flow patterns are identified, the transition between which depends on the combination of Φm, ep−w, and ep−p. Additionally, the quantitative dependence of these transitions on these three parameters is also reported for a series of Stokes and Froude numbers.
Publisher: Elsevier BV
Date: 2019
Publisher: Springer Science and Business Media LLC
Date: 2004
Publisher: Springer Science and Business Media LLC
Date: 28-10-2014
Publisher: Elsevier BV
Date: 05-2013
Publisher: American Chemical Society (ACS)
Date: 17-01-2017
Publisher: Elsevier BV
Date: 04-2017
Publisher: Elsevier BV
Date: 06-2011
Publisher: Elsevier BV
Date: 03-2009
Publisher: Elsevier BV
Date: 1998
Publisher: Elsevier BV
Date: 12-2011
Publisher: Elsevier BV
Date: 09-2017
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 2006
Publisher: Trans Tech Publications, Ltd.
Date: 10-2011
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMR.347-353.2875
Abstract: Using geothermal resources to instead of steam bled form the turbine steam to preheat feed water in a conventional Rankine cycle power station is also termed as geothermal aided power generation (GAPG), this offers a significant potential for the large-scale utilization of geothermal energy for power generation. GAPG enables the conversion of low temperature geothermal energy in the case of 90-260°C into power at a higher efficiency. In GAPG system, geothermal heat is used to preheat the feed water of power generation, instead of the extraction steam, thus the steam flows through the lower stages turbine have changed. In other words, the lower stage turbine works under off-design conditions. However, previous simulation models for the GAPG and solar aided power generation (SAPG), have not considered this turbine off-design operation. Under the off-design conditions, the isentropic efficiency of the turbine and pressure, temperature of each stage of turbines change which lead to the change of the output of turbine. In this paper, a modified thermodynamic model has been developed, considering these changes, which then can estimate the performance of a GAPG plant more accurately than the previous models. The results from various models are compared in this paper.
Publisher: Optica Publishing Group
Date: 04-03-2010
DOI: 10.1364/AO.49.001257
Publisher: Elsevier BV
Date: 03-2006
Publisher: Elsevier BV
Date: 2009
Publisher: Elsevier BV
Date: 05-2015
Publisher: Elsevier BV
Date: 08-2007
Publisher: Elsevier BV
Date: 07-2009
Publisher: Author(s)
Date: 2017
DOI: 10.1063/1.4984481
Publisher: Springer Science and Business Media LLC
Date: 18-02-2007
Publisher: Author(s)
Date: 2017
DOI: 10.1063/1.4984483
Publisher: Elsevier BV
Date: 08-2016
Publisher: American Chemical Society (ACS)
Date: 11-06-2013
DOI: 10.1021/EF400198V
Publisher: IOP Publishing
Date: 03-2013
Publisher: Elsevier BV
Date: 2017
Publisher: Elsevier BV
Date: 09-2006
Publisher: AIP Publishing
Date: 27-05-2005
DOI: 10.1063/1.1928667
Abstract: Turbulent free jets issuing from rectangular slots with various high aspect ratios (15–120) are characterized. The centerline mean and rms velocities are measured using hot-wire anemometry over a downstream distance of up to 160 slot heights at a slot-height-based Reynolds number of 10 000. Experimental results suggest that a rectangular jet with sufficiently high aspect ratio (& ) may be distinguished between three flow zones: an initial quasi-plane-jet zone, a transition zone, and a final quasi-axisymmetric-jet zone. In the quasi-plane-jet zone, the turbulent velocity field is statistically similar, but not identical, to those of a plane jet.
Publisher: Springer Science and Business Media LLC
Date: 19-03-2020
Publisher: Elsevier BV
Date: 03-2017
Publisher: Springer Science and Business Media LLC
Date: 27-10-2009
Publisher: Elsevier BV
Date: 12-2015
Publisher: Optica Publishing Group
Date: 05-10-2007
DOI: 10.1364/AO.46.007227
Abstract: Part 1 describes a model to account for the effect of particles on laser sheet attenuation in flows where particles are heterogeneously distributed and where particles are small compared with the imaged volume. Here we extend the model to account for the effect of a strongly erging light sheet, which is desirable when investigating many turbulent flows, e.g., in two-phase combustion problems. A calibration constant, C(kappa), is derived to account for the attenuation of the incident laser sheet due to extinction of the laser beam through a seeded medium. This is shown to be effective in correcting both the effect of in-plane laser sheet attenuation and out-of-plane signal trapping due to particles in a jet flow heavily seeded with 5 g/s of 25-40 microm spherical particles. In the uncorrected case, attenuation causes up to 15% error in the mean concentration and 35% error on the rms fluctuations. Selecting an appropriate C(kappa) was found to remove the error in the mean concentration and reduce error on the rms fluctuation by half. Methods to estimate or measure an appropriate value of C(kappa) are also presented.
Publisher: Elsevier BV
Date: 2015
Publisher: Elsevier BV
Date: 12-2016
Publisher: Elsevier BV
Date: 2007
Publisher: Springer Science and Business Media LLC
Date: 31-03-2021
Publisher: Elsevier BV
Date: 12-2018
Publisher: Elsevier BV
Date: 07-2008
Publisher: Inderscience Publishers
Date: 2015
Publisher: Elsevier BV
Date: 1992
Publisher: Elsevier BV
Date: 06-2017
Publisher: Elsevier BV
Date: 02-2010
Publisher: Elsevier BV
Date: 02-2016
Publisher: Elsevier BV
Date: 02-2016
Publisher: Wiley
Date: 05-09-2016
Publisher: Springer Science and Business Media LLC
Date: 25-05-2012
Publisher: Elsevier BV
Date: 12-2011
Publisher: Springer Science and Business Media LLC
Date: 2004
Publisher: Elsevier BV
Date: 04-2015
Publisher: Elsevier BV
Date: 05-2003
Publisher: Elsevier BV
Date: 10-2018
Publisher: Elsevier BV
Date: 02-2009
Publisher: Elsevier BV
Date: 05-2015
Publisher: Elsevier BV
Date: 07-2016
Publisher: American Chemical Society (ACS)
Date: 28-05-2013
DOI: 10.1021/EF400217N
Publisher: ASME International
Date: 10-2011
DOI: 10.1115/1.4004991
Abstract: Turbulent secondary flows are motions in the transverse plane, perpendicular to a main, axial flow. They are encountered in non-circular ducts and can, although the velocity is only of the order of 1–3% of the streamwise bulk velocity, affect the characteristics of the mean flow and the turbulent structure. In this work, the focus is on secondary flow in semi-circular ducts which has previously not been reported. Both numerical and experimental analyses are carried out with high accuracy. It is found that the secondary flow in semi-circular ducts consists of two pairs of counter rotating corner vortices, with a velocity in the range reported previously for related configurations. Agreement between simulation and experimental results are excellent when using a second moment closure turbulence model, and when taking the experimental and numerical uncertainty into account. New and unique results of the secondary flow in semi-circular ducts have been derived from verified simulations and validating laser-based experiments.
Publisher: Elsevier BV
Date: 05-2017
Publisher: Elsevier BV
Date: 2011
Publisher: Springer Science and Business Media LLC
Date: 2000
Publisher: Elsevier BV
Date: 05-2017
Publisher: AIP Publishing
Date: 07-2008
DOI: 10.1063/1.2959171
Abstract: The present study systematically investigates through experiments the influence of Reynolds number on a plane jet issuing from a radially contoured, rectangular slot nozzle of large aspect ratio. Detailed velocity measurements were performed for a jet exit Reynolds number spanning the range 1500≤Reh≤16 500, where Reh≡Ubh/υ with Ub as the momentum-averaged exit mean velocity, h as the slot height, and υ as the kinematic viscosity. Additional centerline measurements were also performed for jets from two different nozzles in the same facility to achieve Reh=57 500. All measurements were conducted using single hot-wire anemometry to an axial distance (x) of x≤160h. These measurements revealed a significant dependence of the exit and the downstream flows on Reh despite all exit velocity profiles closely approximating a “top-hat” shape. The effect of Reh on both the mean and turbulent fields is substantial for Reh& 000 but becomes weaker with increasing Reh. The length of the jet’s potential core, initial primary-vortex shedding frequency, and far-field rates of decay and spread all depend on Reh. The local Reynolds number, Rey0.5≡2Ucy0.5/υ, where Uc and y0.5 are the local centerline velocity and half-width, respectively, are found to scale as Rey0.5∼x1/2. It is also shown that, for Reh≥1500, self-preserving relations of both the turbulence dissipation rate (ε) and smallest scale (η), i.e., ε∼Reh3(x/h)−5/2 and η∼Reh−3/4(x/h)5/8, become valid for x/h≥20.
Publisher: Elsevier BV
Date: 05-2011
Publisher: Springer Science and Business Media LLC
Date: 07-05-2013
Publisher: Elsevier BV
Date: 2005
Publisher: Springer Science and Business Media LLC
Date: 02-04-2011
Publisher: Elsevier BV
Date: 11-2017
Publisher: Elsevier BV
Date: 05-2016
Publisher: Elsevier BV
Date: 2017
Publisher: Elsevier BV
Date: 10-2014
Publisher: Elsevier BV
Date: 02-2019
Publisher: IOP Publishing
Date: 28-11-2014
Publisher: Springer Science and Business Media LLC
Date: 10-07-2009
Publisher: Elsevier BV
Date: 05-2012
Publisher: Elsevier BV
Date: 07-2009
Publisher: Elsevier BV
Date: 2009
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 06-2010
Publisher: American Chemical Society (ACS)
Date: 06-2016
Publisher: Elsevier BV
Date: 06-2019
Publisher: Springer Science and Business Media LLC
Date: 14-11-2009
Publisher: Elsevier BV
Date: 11-2017
Publisher: No publisher found
Date: 2014
DOI: 10.1021/EF402542B
Publisher: Optica Publishing Group
Date: 09-08-2007
DOI: 10.1364/AO.46.005823
Abstract: Planar nephelometry is a laser-based technique of imaging the light scattered from particles to provide information about the local number density of these particles. In many seeded flows of practical interest, such as pulverized coal flames, particle loadings are sufficiently high for the incident laser beam to be severely attenuated. Measurements in these flows are therefore difficult, and limited data are available under these conditions. Laser attenuation experiments were conducted in suspensions of spherical particles in water at various concentrations. This is used to formulate a calibration for the effects of diffuse scattering and laser sheet extinction. A model for the distribution of light through a heavily seeded, light-scattering medium is also developed and is compared with experimental results. It is demonstrated that the scattered signal may be considered proportional to the local particle concentration multiplied by the incident laser power. The incident laser power varies as a function of the attenuation by obscurement. This correction for planar nephelometry images thus extends the technique to provide pseudoquantitative data for instantaneous particle concentration measurements.
Publisher: Elsevier BV
Date: 07-2018
Publisher: Elsevier BV
Date: 2016
Publisher: Elsevier BV
Date: 05-2015
Publisher: Elsevier BV
Date: 05-2014
Publisher: Springer Science and Business Media LLC
Date: 25-09-2014
Publisher: SAGE Publications
Date: 06-2011
DOI: 10.1366/10-06108
Abstract: A quantitative point measurement of total sodium ([Na] total ) and potassium ([K] total ) in the plume of a burning particle of Australian Loy Yang brown coal (23 ± 3 mg) and of pine wood pellets (63 ± 3 mg) was performed using laser-induced breakdown spectroscopy (LIBS) in a laminar premixed methane flame at equivalence ratios (Φ) of 1.149 and 1.336. Calibration was performed using atomic sodium or potassium generated by evaporation of droplets of sodium sulfite (Na 2 SO 3 ) or potassium sulfate (K 2 SO 4 ) solutions seeded into the flame. The calibration compensated for the absorption by atomic alkalis in the seeded flame, which is significant at high concentrations of solution. This allowed quantitative measurements of sodium (Na) and potassium (K) released into the flame during the three phases of combustion, namely devolatilization, char, and ash cooking. The [Na] total in the plume released from the combustion of pine wood pellets during the devolatilization was found to reach up to 13 ppm. The maximum concentration of total sodium ([Na] max total ) and potassium ([K] max total ) released during the char phase of burning coal particles for Φ = 1.149 was found to be 9.27 and 5.90 ppm, respectively. The [Na] max total and [K] max total released during the char phase of burning wood particles for Φ = 1.149 was found to be 15.1 and 45.3 ppm, respectively. For the case of Φ = 1.336, the [Na] max total and [K] max total were found to be 13.9 and 6.67 ppm during the char phase from burning coal particles, respectively, and 21.1 and 39.7 ppm, respectively, from burning wood particles. The concentration of alkali species was higher during the ash phase. The limit of detection (LOD) of sodium and potassium with LIBS in the present arrangement was estimated to be 29 and 72 ppb, respectively.
Publisher: Elsevier BV
Date: 08-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7GC00585G
Abstract: Demonstrating technical feasibility and potential for process benefits from alumina calcination with concentrated solar thermal energy.
Publisher: ASME International
Date: 24-04-2017
DOI: 10.1115/1.4036151
Abstract: We report the first systematic investigation of the phenomenon of “switching” between the two bistable axial jet (AJ) and precessing jet (PJ) flow modes in the fluidic precessing jet (FPJ) nozzle. While geometric configurations have been identified where the fractional time spent in the AJ mode is much less than that in the PJ mode, nevertheless, the phenomenon is undesirable and also remains of fundamental interest. This work was undertaken numerically using the unsteady shear stress transport (SST) model, the validation of which showed a good agreement with the experimental results. Three methods were employed in the current work to trigger the flow to switch from the AJ to the PJ modes. It is found that some asymmetry in either the inlet flow or the initial flow field is necessary to trigger the mode switching, with the time required to switch being dependent on the extent of the asymmetry. The direction and frequency of the precession were found to depend on the direction and intensity of the imposed inlet swirling, which will be conducive to the control of the FPJ flow for related industrial applications and academic research. The process with which the vortex skeleton changes within the chamber is also reported. Furthermore, both the rate of spreading and the maximum axial velocity decay of the jet within the nozzle are found to increase gradually during the switching process from the AJ to the PJ modes, consistent with the increased curvature within the local jet.
Publisher: Elsevier BV
Date: 04-2010
Publisher: Elsevier BV
Date: 09-2016
No related grants have been discovered for Graham Nathan.