A robust direct-forcing immersed boundary method with enhanced stability for moving body problems in curvilinear coordinates

Nicolaou, Laura; Jung, Seo Yoon; Zaki, Tamer A.

doi:10.1016/j.compfluid.2015.06.030

Cited by 30 publications

(23 citation statements)

References 42 publications

(92 reference statements)

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“…The LBM calculations were shown to yield better results than RANS, and reproduced significant detail of the experimentally observed flow features. Nicolaou and Zaki (2013) performed DNS in a set of realistic mouth-throat geometries, using an immersed boundary method (Nicolaou et al, 2015). The authors reported that geometric variation, even within the same subject, has a large impact on both the mean flow and the turbulent fluctuations.…”

Section: Flow Fieldmentioning

confidence: 99%

Regional aerosol deposition in the human airways: The SimInhale benchmark case and a critical assessment of in silico methods

Koullapis

Kassinos

Muela

et al. 2018

European Journal of Pharmaceutical Sciences

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Regional deposition effects are important in the pulmonary delivery of drugs intended for the topical treatment of respiratory ailments. They also play a critical role in the systemic delivery of drugs with limited lung bioavailability. In recent years, significant improvements in the quality of pulmonary imaging have taken place, however the resolution of current imaging modalities remains inadequate for quantifying regional deposition. Computational Fluid-Particle Dynamics (CFPD) can fill this gap by providing detailed information about regional deposition in the extrathoracic and conducting airways. It is therefore not surprising that the last 15years have seen an exponential growth in the application of CFPD methods in this area. Survey of the recent literature however, reveals a wide variability in the range of modelling approaches used and in the assumptions made about important physical processes taking place during aerosol inhalation. The purpose of this work is to provide a concise critical review of the computational approaches used to date, and to present a benchmark case for validation of future studies in the upper airways. In the spirit of providing the wider community with a reference for quality assurance of CFPD studies, in vitro deposition measurements have been conducted in a human-based model of the upper airways, and several groups within MP1404 SimInhale have computed the same case using a variety of simulation and discretization approaches. Here, we report the results of this collaborative effort and provide a critical discussion of the performance of the various simulation methods. The benchmark case, in vitro deposition data and in silico results will be published online and made available to the wider community. Particle image velocimetry measurements of the flow, as well as additional numerical results from the community, will be appended to the online database as they become available in the future.

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Section: Flow Fieldmentioning

confidence: 99%

Regional aerosol deposition in the human airways: The SimInhale benchmark case and a critical assessment of in silico methods

Koullapis

Kassinos

Muela

et al. 2018

European Journal of Pharmaceutical Sciences

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“…Direct numerical simulations of the airflow are performed, and a Lagrangian tracking scheme is adopted for the particles. In order to model the airway geometries, an immersed boundary method is employed (Nicolaou et al, 2015). We study particle transport and deposition at different flow rates, and with and without gravity, in order to assess the relative importance of inertial and gravitational effects in the mouth-throat region, as well as the bronchial airways.…”

Section: Introductionmentioning

confidence: 99%

Inertial and gravitational effects on aerosol deposition in the conducting airways

Nicolaou

2018

Journal of Aerosol Science

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In most inhaled drug delivery applications, aerosol deposition in the upper airways occurs primarily via impaction. However, the effects of gravity become important as particle size increases and flow rate decreases. Sedimentation can therefore be significant in the smaller airways of the tracheobronchial tree, where velocities decrease due to the large increase in cross-sectional area, as well as the larger airways at low inhalation flow rates. In order to assess the relative importance of impaction and sedimentation, particle transport and deposition is examined under different steady inhalation conditions in a mouth-throat and a bifurcation model, using direct numerical simulations. The results are also compared to computations without the effect of gravity on the particles. Two important parameters characterize particle motion: (i) the Stokes number, S tk, and (ii) the ratio of the gravitational settling velocity to the fluid velocity, V * g. The ratio of these two parameters is the Froude number, which measures the relative importance of inertial to gravitational forces. Instantaneous definitions of the Stokes number, non-dimensional settling velocity and Froude number are derived, based on the local flow properties, which provide a more accurate representation of the particle trajectories compared to the reference parameters based on characteristic flow scales. Results show that, in certain regions of the flow, the instantaneous Froude number can be three to four orders of magnitude smaller than the reference value. In these regions, deposition via sedimentation is shown to be significant, and the reference parameter underestimates gravitational effects. In the extrathoracic airways, particles with high V * g deposit primarily in the mouth, via sedimentation, while particles with high S tk deposit mainly in the larynx and trachea, via impaction. In the bifurcation, different orientation angles of the airway geometry are shown to result in non-negligible variation in deposition. Impaction is the dominant mechanism for deposition on the carinal ridge, while sedimentation occurs along airway walls at an angle to the gravity direction. In the daughter branches, both impaction and sedimentation contribute to deposition.

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“…So the higher the kinetic Reynolds number the smaller the term τ Re , i.e., the more accurate the method. Another method was used in [2,30,26] based on the direct-forcing approach proposed by [11] where boundary body forces allow the imposition of boundary conditions on interfaces not coinciding with the computational grid.…”

Section: Algorithm To Enforce Moving Domainsmentioning

confidence: 99%

Turbulence in realistic geometries with moving boundaries: When simulations meet experiments

et al. 2021

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Considering the current advances in experimental capabilities in fluid mechanics and the advances in computing power and numerical methods in computational fluid mechanics, a question that naturally arises is whether the two sets of techniques are approaching a level of sophistication sufficiently high to deliver results on turbulent flows in realistic geometries that are comparable. The purpose of this paper is to give elements of answers to this question by considering the so-called von Kármán flow where the fluid in a cylindrical container is driven by two counter-rotating impellers. We compare in the mentioned flow the torque and the flow topology obtained by experiments, direct numerical simulations (DNS), and large eddy simulations (LES) at various Reynolds numbers ranging from R e = O(10 2) to R e = O(10 5). In addition to validating the proposed LES model, the level of agreement that is observed between the numerical and the experimental data shows that the degree of accuracy of each of these techniques is reaching a threshold beyond which it is possible to use each of them with high confidence to explore and better understand turbulence in complex flows at R e = O(10 5) and beyond.

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A robust direct-forcing immersed boundary method with enhanced stability for moving body problems in curvilinear coordinates

Cited by 30 publications

References 42 publications

Regional aerosol deposition in the human airways: The SimInhale benchmark case and a critical assessment of in silico methods

Regional aerosol deposition in the human airways: The SimInhale benchmark case and a critical assessment of in silico methods

Inertial and gravitational effects on aerosol deposition in the conducting airways

Turbulence in realistic geometries with moving boundaries: When simulations meet experiments

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