Publications
138 results found
Rennie CE, Gouder K, Taylor DJ, et al., 2011, Nasal inspiratory flow: at rest and sniffing, International Forum of Allergy & Rhinology, Vol: 1, Pages: 128-135
BackgroundThis study quantifies the time-varying flow rate during inspiration at rest and in sniffing, both predecongestion and postdecongestion. It aims to provide a better understanding of nasal airflow mechanics, for application to the physiological modeling of nasal respiration and to therapeutic drug delivery.MethodsThe temporal profiles of nasal inspiration were measured at high fidelity in 14 healthy individuals using simultaneous bilateral hot-wire anemometry. Peak nasal inspiratory flow (PNIF) rate, acoustic rhinometry (AR), and the sinonasal outcome test (SNOT) provided complementary clinical measurements. The impact of decongestion was also investigated.ResultsIn the initial phase of inspiration, a rapid rise in flow rate was observed. Flow first exceeded 150 mL/second in either passage within a median time of approximately 120 ms for inspiration at rest and approximately 60 ms in sniffing (∼20 ms in the fastest sniffs). The mean sustained flow rate attained and the overall period of each measured inspiratory profile were analyzed. AR showed a significant change in nasal volume with decongestion, although these change were not manifest in the temporal profiles of inspiratory flow (barring a weak effect associated with the most vigorous sniffs).ConclusionNovel methods were applied to investigate the temporal profiles of nasal inspiration. Characteristic features of the profile were identified and found to be significantly different between inspiration at rest and sniffing. Decongestion was found to have little effect on the temporal profiles for the flow regimes studied.
Rossi L, Doorly D, Durant A, et al., 2011, Lamination and mixing in canonical and turbulent flows
Lamination and mixing properties are characterised for a canonical flow (cat's eyes flip) at low Reynolds number (~13) and a turbulent flow. The cat's eyes flow is experimentally driven by electromagnetic forces while the turbulent flow is generated using 2D DNS. It is shown that lamination and stretching grow exponentially for both flows with an exponent higher for the stretching than for the lamination. Noticeably, the difference between the stretching and lamination exponents is higher for the turbulent flow than for the low Reynolds number flow with ratios respectively about 1.32 and 1.12. Moreover, lamination enhances mixing locally by reducing the distance over which diffusion needs to act to finalise mixing. The difference in the mixing properties of the flows is related to the distribution of lamination. The turbulent flow saturates locally, i.e. it reaches locally high lamination values where diffusion can act swiftly over short distances to finalise mixing while most of the flow is still with low values of lamination. This leads to an algebraic growth of the mixing coefficient. The cat's eyes flip flow globally increases lamination with a better space filling than the turbulent flow. This delays the saturation of mixing and leads to an initial exponential growth of the mixing coefficient.
Cookson AN, Doorly DJ, Sherwin SJ, 2010, Using coordinate transformation of Navier–Stokes equations to solve flow in multiple helical geometries, Journal of Computational and Applied Mathematics, Vol: 234, Pages: 2069-2079
Recent research on small amplitude helical pipes for use as bypass grafts and arterio-venous shunts, suggests that mixing may help prevent occlusion by thrombosis. It is proposed here that joining together two helical geometries, of different helical radii, will enhance mixing, with only a small increase in pressure loss. To determine the velocity field, a coordinate transformation of the Navier–Stokes equations is used, which is then solved using a 2-D high-order mesh combined with a Fourier decomposition in the periodic direction. The results show that the velocity fields in each component geometry differ strongly from the corresponding solution for a single helical geometry. The results suggest that, although the mixing behaviour will be weaker than an idealised prediction indicates, it will be improved from that generated in a single helical geometry.
Rennie C, Hood C, Blenke E, et al., 2010, Analysis of Maxillary Sinus Ventilation, Otolaryngology–Head and Neck Surgery, Vol: 143, ISSN: 0194-5998
Gambaruto AM, Doorly DJ, Yamaguchi T, 2010, Wall shear stress and near-wall convective transport: Comparisons with vascular remodelling in a peripheral graft anastomosis, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 229, Pages: 5339-5356, ISSN: 0021-9991
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- Citations: 32
Taylor DJ, Doorly DJ, Schroter RC, 2010, Inflow boundary profile prescription for numerical simulation of nasal airflow, JOURNAL OF THE ROYAL SOCIETY INTERFACE, Vol: 7, Pages: 515-527, ISSN: 1742-5689
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- Citations: 69
Hood CM, Schroter RC, Doorly DJ, et al., 2010, Modeling of Human Maxillary Sinus Nitric Oxide Transport, 6th World Congress of Biomechanics (WCB 2010), Publisher: SPRINGER, Pages: 706-+, ISSN: 1680-0737
Hood CM, Schroter RC, Doorly DJ, et al., 2009, Computational modeling of flow and gas exchange in models of the human maxillary sinus, JOURNAL OF APPLIED PHYSIOLOGY, Vol: 107, Pages: 1195-1203, ISSN: 8750-7587
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- Citations: 45
Gambaruto AA, Taylor DJ, Doorly DJ, 2009, Modelling nasal airflow using a Fourier descriptor representation of geometry, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Vol: 59, Pages: 1259-1283, ISSN: 0271-2091
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- Citations: 21
Denis Doorly, Spencer Sherwin, 2009, Geometry and Flow, Cardiovascular Mathematics, Editors: Quarteroni, Formaggia, Veneziani, Publisher: Springer
Cookson A, 2009, Computational Investigation of Helical Pipe Geometries From a Mixing Perspective
Recent research on small amplitude helical pipes for use as bypass grafts and arterio- venous shunts suggest that in-plane mixing induced by the geometry may help pre- vent occlusion by thrombosis. In this thesis, a coordinate transformation of the Navier-Stokes equations is solved within a spectral/hp element framework to study the flow field and mixing behaviour of small-amplitude helical pipes. An apparent discrepancy between the flow field and particle trajectories is observed, whereby particle paths display a pattern characteristic of a double vortex, though the flow field reveals only a single dominant vortex. It is shown that a combination of trans- lational and rotational reference frames changes resolves this discrepancy.It is then proposed that joining together two helical geometries, of differing helical radii, will enhance mixing, through the phenomenon of ‘streamline crossing’. An idealised prediction of the mixing is obtained by concatenating the velocity field solutions from the respective single helical geometries. The mixing is examined using Poincar ́e sections, residence time data and information entropy. The flow is then solved for those combined geometries showing the most improvement in mixing, with a 70% increase in mixing efficiency achieved, with only a small increase in pressure loss. It is found that although the true velocity fields vary significantly from the prediction, the overall mixing behaviour is captured, allowing the use of the idealised prediction for guiding future designs of combined geometries.
Taylor DJ, Doorly DJ, Schroter RC, 2009, AIRFLOW IN THE HUMAN NASAL CAVITY: AN INTER-SUBJECT COMPARISON, ASME Summer Bioengineering Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 1071-1072
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- Citations: 2
Arimon JA, Balossino R, D'Angelo C, et al., 2009, Applications and test cases, CARDIOVASCULAR MATHEMATICS: MODELING AND SIMULATION OF THE CIRCULATORY SYSTEM, Editors: Formaggia, Quarteroni, Veneziani, Publisher: SPRINGER, Pages: 447-475, ISBN: 978-88-470-1151-9
Doorly DJ, Taylor DJ, Schroter RC, 2008, Mechanics of Airflow in the Human Nasal Airways, Respiratory Physiology & Neurobiology, Vol: 163, Pages: 100-110
The mechanics of airflow in the human nasal airways is reviewed, drawing on the findings of experimental and computational model studies. Modelling inevitably requires simplifications and assumptions, particularly given the complexity of the nasal airways. The processes entailed in modelling the nasal airways (from defining the model, to its production and, finally, validating the results) is critically examined, both for physical models and for computational simulations. Uncertainty still surrounds the appropriateness of the various assumptions made in modelling, particularly with regard to the nature of flow. New results are presented in which high-speed particle image velocimetry (PIV) and direct numerical simulation are applied to investigate the development of flow instability in the nasal cavity. These illustrate some of the improved capabilities afforded by technological developments for future model studies. The need for further improvements in characterising airway geometry and flow together with promising new methods are briefly discussed.
Doorly DJ, Taylor DJ, Gambaruto AM, et al., 2008, Nasal architecture: form and flow, Phil. Trans. R. Soc. A, Vol: 366, Pages: 3225-3246
Current approaches to model nasal airflow are reviewed in this study, and new findings presented. These new results make use of improvements to computational and experimental techniques and resources, which now allow key dynamical features to be investigated, and offer rational procedures to relate variations in anatomical form. Specifically, both replica and simplified airways of a single subject were investigated and compared with the replica airways of two other individuals with overtly differing geometries. Procedures to characterize and compare complex nasal airway geometry are first outlined. It is then shown that coupled computational and experimental studies, capable of obtaining highly resolved data, reveal internal flow structures in both intrinsically steady and unsteady situations. The results presented demonstrate that the intimate relation between nasal form and flow can be explored in greater detail than hitherto possible. By outlining means to compare complex airway geometries and demonstrating the effects of rational geometric simplification on the flow structure, this work offers a fresh approach to studies of how natural conduits guide and control flow. The concepts and tools address issues that are thus generic to flow studies in other physiological systems.
Gambaruto AM, Peiro J, Doorly DJ, et al., 2008, Reconstruction of shape and its effect on flow in arterial conduits, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Vol: 57, Pages: 495-517, ISSN: 0271-2091
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- Citations: 20
Cookson AN, Doorly DJ, Sherwin SJ, 2008, Mixing through stirring of steady flow in small amplitude helical pipes, Ann. Biomed. Engrg., Vol: 37, Pages: 710-721
In this paper we numerically simulate flow in a helical tube for physiological conditions using a co-ordinate mapping of the Navier–Stokes equations. Helical geometries have been proposed for use as bypass grafts, arterial stents and as an idealized model for the out-of-plane curvature of arteries. Small amplitude helical tubes are also currently being investigated for possible application as A–V shunts, where preliminary in vivo tests suggest a possibly lower risk of thrombotic occlusion. In-plane mixing induced by the geometry is hypothesized to be an important mechanism. In this work, we focus mainly on a Reynolds number of 250 and investigate both the flow structure and the in-plane mixing in helical geometries with fixed pitch of 6 tube diameters (D), and centerline helical radius ranging from 0.1D to 0.5D. High-order particle tracking, and an information entropy measure is used to analyze the in-plane mixing. A combination of translational and rotational reference frames are shown to explain the apparent discrepancy between flow field and particle trajectories, whereby particle paths display a pattern characteristic of a double vortex, though the flow field reveals only a single dominant vortex. A radius of 0.25D is found to provide the best trade-off between mixing and pressure loss, with little increase in mixing above R = 0.25D, whereas pressure continues to increase linearly.
Doorly DJ, Taylor DJ, Franke P, 2008, Experimental investigation of nasal airflow, Journal of Engineering in Medicine, Vol: 222
The airway geometry of the nasal cavity is manifestly complex, and the manner in which it controls the airflow to accomplish its various physiological functions is not fully understood. Since the complex morphology and inaccessibility of the nasal passageways precludes detailed in-vivo measurements, either computational simulation or in-vitro experiments are needed to determine how anatomical form and function are related. The fabrication of a replica model of the nasal cavity, of a high optical clarity and derived from invivo scan data is described here, together with characteristics of the flow field investigated using particle image velocimetry (PIV) and flow visualization. Flow visualization is shown to be a capable and convenient technique for identifying key phenomena. Specifically the emergence of the jet from the internal nasal valve into the main cavity, how it impacts on the middle turbinate, and the large enhancement of dispersion that accompanies the initial appearance of flow instability are revealed as particularly significant features. The findings from the visualization experiments are complemented by PIV imaging, which provides quantitative detail on the variations in velocity in different regions of the nasal cavity. These results demonstrate the effectiveness of the cavity geometry in partitioning the flow into high shear zones, which facilitate rapid heat transfer and humidification from the nasal mucosa, and slower zones affording greater residence times to facilitate olfactory sensing. The experimental results not only provide a basis for comparison with other computational modelling but also demonstrate an alternative and flexible means to investigate complex flows, relevant to studies in different parts of the respiratory or cardiovascular systems.
Lee KL, Doorly DJ, Firmin DN, 2006, Numerical simulations of phase contrast velocity mapping of complex flows in an anatomically realistic bypass graft geometry, MEDICAL PHYSICS, Vol: 33, Pages: 2621-2631, ISSN: 0094-2405
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- Citations: 17
Gambaruto A, Doorly D, 2006, Characterisation of nasal geometry and flow, Journal of Biomechanics, Vol: 39, Pages: S272-S272, ISSN: 0021-9290
Lee KL, Firmin DN, Doorly DJ, 2005, Assessment of MR angiography using in-vitro models and computer simulation, Proceedings of the 2005 Summer Bioengineering Conference, Vol: 2005, Pages: 711-712
Gambaruto AM, Radaelli A, Doorly DJ, et al., 2005, Sensitivity study on by-pass graft reconstruction with emphasis on flow solutions, Pages: 832-833
Giordana S, Sherwin SJ, Peiró J, et al., 2005, Local and global geometric influence on steady flow in distal anastomoses of peripheral bypass grafts, JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME, Vol: 127, Pages: 1087-1098, ISSN: 0148-0731
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- Citations: 39
Thomson J, Jha R, Doorly D, 2005, Evolutionary neuro controller design for autonomous unmanned aerial vehicles, Pages: 9125-9135
The development of an Evolutionary Neuro Controller (ENC) is presented for automating the flight of Unmanned Aerial Vehicles (UAVs). The ENC is based on the Neuro-Adaptive Predictive Controller (NAPC) and the ENC controls an aircraft using several Neural Networks (NNs), each one trained to handle a different set of flight conditions. An evolutionary neural network (E-Net) is implemented using a pair of genetic algorithms (GAs) to determine which NN makes the best prediction for a particular flight condition. The predictive NNs and the E-Net evolve together to generate a controller capable of robustly controlling an UAV. A Matlab model is developed and used to simulate the longitudinal dynamics of an aircraft. Results show good performance for the combined E-Net and NNs to classify the flight condition and make predictions.
Giordana S, Sherwin SJ, Peiró J, et al., 2005, Automated classification of peripheral distal by-pass geometries reconstructed from medical data, JOURNAL OF BIOMECHANICS, Vol: 38, Pages: 47-62, ISSN: 0021-9290
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- Citations: 24
Thomson J, Clarkson RJ, Doorly D, 2005, Evolutionary neuro-controller design for autonomous unmanned aerial vehicles (Papers no.AIAA-2005-913), 43rd AIAA Aerospace Sciences Meeting and Exhibition, 10 - 13 January 2005, Reno, Nevada, Publisher: AIAA, Pages: 1-11
Taylor DJ, Franke VE, Doorly DJ, et al., 2005, Airflow in the human nasal cavity, Proc. ASME 2005 Bioengineering Conference
Franke VE, Franke PT, Doorly DJ, et al., 2005, Computational modelling of flow in the nasal cavities, Proc ASME SBC05 Summer Bioengineering meeting, 22 - 26 June 2005, Colorado, USA, Publisher: ASME
Giordana S, Radaelli A, Peiro J, et al., 2004, Geometry reconstruction and CFD modeling of arterial flows, Proceedings ICFD conference on numerical methods for fluid dynamics, Oxford, England, 29 March - 1 April 2004
Jackson MJ, Bicknell CD, Zervas V, et al., 2003, Three-dimensional reconstruction of autologous vein bypass graft distal anastomoses imaged with magnetic resonance:: Clinical and research applications, JOURNAL OF VASCULAR SURGERY, Vol: 38, Pages: 621-625, ISSN: 0741-5214
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- Citations: 11
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