50 research outputs found
CFD Study of the Flow Field and Particle Dispersion and Deposition in the Upper Human Respiratory System
Das Einatmen von Partikeln in den menschlichen Körper hat zwei verschiedene Aspekte im Hinblick auf die Gesundheit des Menschen. Einerseits existieren schĂ€dliche Partikel wie beispielsweise Feinstaub in der Umwelt, der nach Eintreten in den menschlichen Körper Krankheiten wie Herzerkrankungen und Erkrankungen der Atemwege auslösen kann, und der sogar zum Tod fĂŒhren kann. Hier sind insbesondere Partikel, die kleiner als 2,5 ”m sind, relevant. Andererseits ist es in der medizinischen Therapie einiger Atemwegerkrankungen wĂŒnschenswert, gezielt Partikel den Atemwegen zuzufĂŒhren. Die medikamentöse Aerosol-Therapie, bei der das Medikament durch den nasalen oder oralen Atemweg in die Lunge oder einen anderen Ort des Atemtrakts gebracht wird, wird gern verwendet, um Krankheiten wie z.B. Asthma oder chronisch obstruktive Lungenerkrankungen zu behandeln. Diese Therapie hat den Vorteil der kleinen Dosierung, der minimalen systemischen Nebenwirkungen und der schnellen Wirkung. Das Medikament soll hier tief in die Lunge, in der die Krankheit auftritt, eindringen. Die typische GröĂe dieser Partikel liegt im Bereich von 1 bis 5 ”m. Fokus ist die gezielte Steuerung des Medikaments in spezielle Regionen wie beispielsweise zu einer Tumorposition, sodass Nebenwirkungen durch Ablagerung in anderen Regionen vermieden werden. Ein verbessertes VerstĂ€ndnis des Gesamtprozesses beinhaltet die Kenntnis der charakteristischen Luftströmung und des Partikeltransports sowie deren gegenseitige Beeinflussung. In der vorliegenden Arbeit, in der die Luftströmung sowie die Partikelverteilung und -ablagerung in den menschlichen oberen Atemwegen untersucht werden, werden vier verschiedene Geometrien verwendet: die verengte Luftröhre, das auf einem GussstĂŒck basierende Mund-Rachen-Modell, das auf Computertomographie (CT) basierende Mund-Rachen-Modell und das auf CT-Skans basierende Nasenhöhlen-Modell. Die Software NeuRa2 wird zur Generierung des numerischen OberflĂ€chengitters verwendet und ANSYS ICEM CFD-11.0, um Volumengitter zu erzeugen. Ein-Weg- und Zwei-Wege-Kopplung zwischen der Gasphase und den Partikeln werden in der Arbeit in AbhĂ€ngigkeit verschiedener Partikelvolumenanteile angewendet. Dreidimensionale inkompressible Navier-Stokes (N-S) Gleichungen werden zur Beschreibung der Luftströmung verwendet. Large Eddy Simulation (LES) wird zur Modellierung der turbulenten Strömung herangezogen, und das Smagorinsky Feinskalen-Modell sowie das dynamische Smagorinsky Modell dienen der Beschreibung der kleinen turbulenten Skalen. Unter der Annahme eines groĂen Partikel-Luft DichteverhĂ€ltnisses, der VernachlĂ€ssigbarkeit der Partikelrotation und der Kollision zwischen den Partikeln sowie der Annahme, dass die TrĂ€gheitskraft die Partikelbewegung dominiert, werde Lagrange-Gleichungen herangezogen, um die Bewegung der Partikel zu modellieren. Im Falle von Partikeln, die kleiner als ein Mikrometer sind, wird die Brownsche Kraft zusĂ€tzlich berĂŒcksichtigt. Zur Lösung der Gleichungen wird die Software-Plattform OpenFOAM 1.5 benutzt, fĂŒr die neue Solver entwickelt werden, die die Luftströmung mit LES und die Teilchenbewegung mit Hilfe einer Lagrange-Formulierung lösen können. AbhĂ€ngig von der Partikelbeladung wird Ein-Weg- oder Zwei-Wege-Kopplung mit oder ohne BerĂŒcksichtigung des Einflusses des Partikelimpulses auf die Gasphase verwendet. ZunĂ€chst wird die Luftgeschwindigkeit an der Mittellinie und in unterschiedlichen Querschnitten stromabwĂ€rts der Glottis in der verengten Luftröhre mit numerischen Ergebnissen und experimentellen Daten aus der Literatur verglichen, hier wird ein Modell der Reynolds-gemittelten Navier-Stokes-Gleichungen (RANS) bei niedriger Reynolds-Zahl, das k-omega; Modell, verwendet. Die hier verwendete Methode verbessert die vorliegenden Literaturergebnisse, sodass sie die Basis fĂŒr weitere Berechnungen in den verbleibenden Geometrien bildet. Die Luftströmung wird im GussstĂŒck-basierten Mund-Rachen-Modell fĂŒr drei verschiedene Inhalationsgeschwindigkeiten simuliert. Die numerischen Ergebnisse zeigen, dass das Geschwindigkeitsfeld der instationĂ€ren Luftströmung sehr stark vom mittleren Geschwindigkeitsfeld abweicht, dies gilt insbesondere fĂŒr das Auftreten von Wirbeln. Die numerische Simulation zeigt, dass die Partikelablagerung von der PartikelgröĂe, ihrer Ausgangsposition, der Inhalationsgeschwindigkeit sowie von der Geometrie abhĂ€ngt. Turbulenz und Existenz von Rezirkulationszonen haben ebenfalls groĂen Einfluss auf den Partikeltransport. Eine polydisperse Partikelverteilung, die aus Messungen an einem Trockenpulver-Inhalator zur VerfĂŒgung steht, wird ebenfalls zur Simulation herangezogen. In diesem Fall wird Zwei-Wege-Kopplung verwendet. Polydisperse Partikelablagerung zeigt im Vergleich zur monodispersen Partikelablagerung stark unterschiedliche Charakteristika. Deshalb ist es notwendig, polydisperse Partikelverteilung und Zwei-Wege-Kopplung zu verwenden, wenn die reale medikamentöse Dosis eines Hubs berĂŒcksichtigt wird, die bei der klinischen Behandlung Anwendung findet. Um das Strömungsfeld bei einer realistischeren zeitabhĂ€ngigen Inhalation zu untersuchen, wird eine numerische Simulation fĂŒr das GussstĂŒck-basierte Mund-Rachen-Modell unter den gleichen Bedingungen durchgefĂŒhrt. Die Untersuchung zeigt, dass das Strömungsfeld signifikant verschieden ist in der beschleunigenden und der verlangsamenden Phase der Inhalation: In der Beschleunigungsphase ist die Luftströmung laminar wĂ€hrend sie in der verlangsamenden Phase eher turbulent ist. Zur Untersuchung des Einflusses geometrischer Eigenschaften auf die Partikelablagerung werden numerische Simulationen fĂŒr das CT-basierte Mund-Rachen-Modell durchgefĂŒhrt. Im Ergebnis ist das Strömungsfeld im CT-basierten Mund-Rachen-Modell sehr verschieden von dem im GussstĂŒck-basierten Mund-Rachen-Modell. Obwohl das Geschwindigkeitsfeld sowohl im mittleren als auch im zeitabhĂ€ngigen Fall Ă€hnlich ist, hat das Strömungsfeld ein sehr kompliziertes Wirbelfeld mit hoher rĂ€umlicher und zeitlicher Dynamik. Partikel der GröĂe 2 ”m können den Pharynx passieren, sich in der Luftröhre ablagern oder weiter in die Lungenregion vordringen. Um die Eigenschaften des Geschwindigkeitsfelds in der Nasenhöhle zu untersuchen, wurde ein geometrisches Modell der Nasenhöhle aus CT-Skans konstruiert. Die numerischen Ergebnisse zeigen, dass die Luft durch die Hauptluft-Passage der Nasenhöhle flieĂt und nur wenig Luft die Spitzen der NasengĂ€nge und der olfaktorischen Region erreicht
A sufficient and necessary condition of existence of blow-up radial solutions for a k-Hessian equation with a nonlinear operator
In this paper, we establish the results of nonexistence and existence of blow-up radial solutions for a k-Hessian equation with a nonlinear operator. Under some suitable growth conditions for nonlinearity, the result of nonexistence of blow-up solutions is established, a sufficient and necessary condition on existence of blow-up solutions is given, and some further results are obtained. 
Numerical Simulation of the Dispersion and Deposition of a Spray Carried by a Pulsating Airflow in a Patient-Specific Human Nasal Cavity
[EN] The present numerical study concerns the dispersion and deposition of a nasal spray in a patient-specific human
nose. The realistic three-dimensional geometry of the nasal cavity is reconstructed from computer tomography
(CT) scans. Identification of the region of interest, removal of artifacts, segmentation, generation of the .STL file
and the triangulated surface grid are performed using the software packages ImageJ, meshLab, and NeuRA2. An
unstructured computational volume grid with approximately 15 million tetrahedral grid cells is generated using the
software Ansys ICEM-CFD 11.0. An unsteady Eulerian-Lagrangian formulation is used to describe the airflow and
the spray dispersion and deposition in the realistic human nasal airway using two-way coupling. A new solver called
pimpleParcelFoam is developed, which combines the lagrangianParcel libraries with the pimpleFoam solver within
the software package OpenFOAM 3.0.0. A large eddy simulation (LES) with the dynamic sub-grid scale (SGS)
model is performed to study the spray in both a steady and a pulsating airflow with an inflow rate of 7.5 L/min
(or maximum value in case of the pulsating spray) and a frequency of 45 Hz for pulsation as used in commercial
inhalation devices. 10,000 mono-disperse particles with the diameters of 2.4 ”m and 10 ”m are uniformly injected
at the nostrils. In order to fulfil the stability conditions for the numerical solution, a constant time-step of 10â5
s
is implemented. The simulations are performed for a real process time of 1 s, since after the first second of the
process, all particles have escaped through the pharynx or they are deposited at the surface of the nasal cavity. The
numerical computations are performed on the high-performance computer bwForCluster MLS&WISO Production
using 256 processors, which take around 32 and 75 hours for steady and pulsating flow simulation, respectively.
The study shows that the airflow velocity reaches its maximum values in the nasal valve, in parts of the septum
and in the nasopharynx. A complex airflow is observed in the vestibule and in the nasopharynx region, which may
directly affect the dispersion and deposition pattern of the spray. The results reveal that the spray tends to deposit in
the nasal valve, the septum and in the nasopharynx due to the change in the direction of the airflow in these regions.
Moreover, it is found that due to the pulsating airflow, the aerosols are more dispersed and penetrate deeper into
the posterior regions and the meatuses where the connections to the sinuses reside.The authors thank Dr. H. Mentzel from PARI Respiratory Equipment, Inc. for intense discussions about the pulsating spray initial conditions. The current study is part of a project supported by the German Research Foundation (DFG) through a research fellowship of the HGS MathComp. Furthermore, high-performance computing time at the bwForCluster MLS&WISO Production which is funded by the state of Baden-WĂŒrttemberg through bwHPC and DFG through grant INST 35/1134-1 FUGG.Farnoud, A.; Cui, X.; Baumann, I.; Gutheil, E. (2017). Numerical Simulation of the Dispersion and Deposition of a Spray Carried by a Pulsating Airflow in a Patient-Specific Human Nasal Cavity. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat PolitĂšcnica de ValĂšncia. 529-536. https://doi.org/10.4995/ILASS2017.2017.4628OCS52953
Solvability and asymptotic properties for an elliptic geophysical fluid flows model in a planar exterior domain
In this paper, we study the solvability and asymptotic properties of a recently derived gyre model of nonlinear elliptic Schrödinger equation arising from the geophysical fluid flows. The existence theorems and the asymptotic properties for radial positive solutions are established due to space theory and analytical techniques, some special cases and specific examples are also given to describe the applicability of model in gyres of geophysical fluid flows
Existence and asymptotic analysis of positive solutions for a singular fractional differential equation with nonlocal boundary conditions
In this paper, we focus on the existence and asymptotic analysis of positive solutions for a class of singular fractional differential equations subject to nonlocal boundary conditions. By constructing suitable upper and lower solutions and employing Schauderâs fixed point theorem, the conditions for the existence of positive solutions are established and the asymptotic analysis for the obtained solution is carried out. In our work, the nonlinear function involved in the equation not only contains fractional derivatives of unknown functions but also has a stronger singularity at some points of the time and space variables
Comparison of Efficacy of Deep Brain Stimulation of Different Targets in Parkinson's Disease: A Network Meta-Analysis
Background: Deep brain stimulation (DBS) is considered an effective treatment option for Parkinson's disease (PD). Several studies have demonstrated the efficacy of neurostimulation in patients with advanced PD. The subthalamic nucleus (STN), the internal globus pallidus (GPi), ventral intermediate nucleus (Vim), and pedunculopontine nucleus (PPN) are reportedly effective DBS targets for control of Parkinsonian tremors. However, there is no consensus on the ideal target for DBS in patients with Parkinson's disease. Only a few studies have directly compared the efficacy of DBS of the Vim, STN, and GPi. Therefore, we searched PubMed, Embase, Cochrane Library, and other databases for observational studies, extracted data on unified Parkinson's disease rating scale (UPDRS) scores and performed a comprehensive network meta-analysis of different strategies of DBS and compared the efficiency of DBS at different targets.Methods: Forest plot was used to examine the overall efficiency of DBS; cumulative probability value was used to rank the strategies under examination. A node-splitting model was employed to assess consistency of reported outcomes inconsistency. A total of 16 studies which focused on UPDRS improvement were included in the network meta-analysis.Results: By comparing the overall efficiency associated with each target, we confirmed the efficacy of DBS therapy in PD. Our findings revealed similar efficacy of DBS targeted at GPi and STN in the on-medication phase [GPi-3.9 (95% CI â7.0 to â0.96); STN-3.1 (â5.9 to â0.38)]; however, in the off-medication phase, Vim-targeted DBS was associated with better improvement in UPDRS scores and could be a choice as a DBS target for tremor-dominant Parkinsonism.Conclusions: Our findings will help improve clinical application of DBS
Inverse Estimation of an Annual Cycle of California's Nitrous Oxide Emissions
Nitrous oxide (N_2O) is a potent longâlived greenhouse gas (GHG) and the strongest current emissions of global anthropogenic stratospheric ozone depletion weighted by its ozone depletion potential. In California, N_2O is the third largest contributor to the state's anthropogenic GHG emission inventory, though no study has quantified its statewide annual emissions through topâdown inverse modeling. Here we present the first annual (2013â2014) statewide topâdown estimates of anthropogenic N_2O emissions. Utilizing continuous N_2O observations from six sites across California in a hierarchical Bayesian inversion, we estimate that annual anthropogenic emissions are 1.5â2.5 times (at 95% confidence) the state inventory (41 Gg N_2O in 2014). Without mitigation, this estimate represents 4â7% of total GHG emissions assuming that other reported GHG emissions are reasonably correct. This suggests that control of N_2O could be an important component in meeting California's emission reduction goals of 40% and 80% below 1990 levels of the total GHG emissions (in CO_2 equivalent) by 2030 and 2050, respectively. Our seasonality analysis suggests that emissions are similar across seasons within posterior uncertainties. Future work is needed to provide source attribution for subregions and further characterization of seasonal variability
Atmospheric observation-based estimation of fossil fuel CO_2 emissions from regions of central and southern California
Combustion of fossil fuel is the dominant source of greenhouse gas emissions to the atmosphere in California. Here, we describe radiocarbon (^(14)CO_2) measurements and atmospheric inverse modeling to estimate fossil fuel CO_2 (ffCO_2) emissions for 2009â2012 from a site in central California, and for June 2013âMay 2014 from two sites in southern California. A priori predicted ffCO_2 mixing ratios are computed based on regional atmospheric transport model (WRF-STILT) footprints and an hourly ffCO_2 prior emission map (Vulcan 2.2). Regional inversions using observations from the central California site suggest that emissions from the San Francisco Bay Area (SFBA) are higher in winter and lower in summer. Taking all years together, the average of a total of fifteen 3-month inversions from 2009 to 2012 suggests ffCO_2 emissions from SFBA were within 6âŻÂ±âŻ35% of the a priori estimate for that region, where posterior emission uncertainties are reported as 95% confidence intervals. Results for four 3-month inversions using measurements in Los Angeles South Coast Air Basin (SoCAB) during June 2013âMay 2014 suggest that emissions in SoCAB are within 13âŻÂ±âŻ28% of the a priori estimate for that region, with marginal detection of any seasonality. While emissions from the SFBA and SoCAB urban regions (containing ~50% of prior emissions from California) are constrained by the observations, emissions from the remaining regions are less constrained, suggesting that additional observations will be valuable to more accurately estimate total ffCO_2 emissions from California as a whole
Atmospheric observation-based estimation of fossil fuel CO_2 emissions from regions of central and southern California
Combustion of fossil fuel is the dominant source of greenhouse gas emissions to the atmosphere in California. Here, we describe radiocarbon (^(14)CO_2) measurements and atmospheric inverse modeling to estimate fossil fuel CO_2 (ffCO_2) emissions for 2009â2012 from a site in central California, and for June 2013âMay 2014 from two sites in southern California. A priori predicted ffCO_2 mixing ratios are computed based on regional atmospheric transport model (WRF-STILT) footprints and an hourly ffCO_2 prior emission map (Vulcan 2.2). Regional inversions using observations from the central California site suggest that emissions from the San Francisco Bay Area (SFBA) are higher in winter and lower in summer. Taking all years together, the average of a total of fifteen 3-month inversions from 2009 to 2012 suggests ffCO_2 emissions from SFBA were within 6âŻÂ±âŻ35% of the a priori estimate for that region, where posterior emission uncertainties are reported as 95% confidence intervals. Results for four 3-month inversions using measurements in Los Angeles South Coast Air Basin (SoCAB) during June 2013âMay 2014 suggest that emissions in SoCAB are within 13âŻÂ±âŻ28% of the a priori estimate for that region, with marginal detection of any seasonality. While emissions from the SFBA and SoCAB urban regions (containing ~50% of prior emissions from California) are constrained by the observations, emissions from the remaining regions are less constrained, suggesting that additional observations will be valuable to more accurately estimate total ffCO_2 emissions from California as a whole