scholarly journals Numerical Simulation of the Dispersion and Deposition of a Spray Carried by a Pulsating Airflow in a Patient-Specific Human Nasal Cavity

2017 ◽  
Author(s):  
Ali Farnoud ◽  
Xinguang Cui ◽  
Ingo Baumann ◽  
Eva Gutheil
Keyword(s):  
Nasal Cavity ◽  
High Performance ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Patient Specific ◽  
Process Time ◽  
Nasal Valve ◽  
Time Step ◽  
Real Process

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 µm and 10 µm are uniformly injected at the nostrils. In order to fulfil the stability conditions for the numerical solution, a constant time-step of 10−5 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.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4628

Fused filament printing of specialized biomedical devices: a state-of-the art review of technological feasibilities with PEEK

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Erfan Rezvani Ghomi ◽  
Saeideh Kholghi Eshkalak ◽  
Sunpreet Singh ◽  
Amutha Chinnappan ◽  
Seeram Ramakrishna ◽  
...  
Keyword(s):  
High Performance ◽  
State Of The Art ◽  
Three Dimensional ◽  
Patient Specific ◽  
Biomedical Devices ◽  
Fused Filament Fabrication ◽  
Content Type ◽  
Patient Specific Implants ◽  
Complex Design ◽  
Wide Range

Purpose The potential implications of the three-dimensional printing (3DP) technology are growing enormously in the various health-care sectors, including surgical planning, manufacturing of patient-specific implants and developing anatomical models. Although a wide range of thermoplastic polymers are available as 3DP feedstock, yet obtaining biocompatible and structurally integrated biomedical devices is still challenging owing to various technical issues. Design/methodology/approach Polyether ether ketone (PEEK) is an organic and biocompatible compound material that is recently being used to fabricate complex design geometries and patient-specific implants through 3DP. However, the thermal and rheological features of PEEK make it difficult to process through the 3DP technologies, for instance, fused filament fabrication. The present review paper presents a state-of-the-art literature review of the 3DP of PEEK for potential biomedical applications. In particular, a special emphasis has been given on the existing technical hurdles and possible technological and processing solutions for improving the printability of PEEK. Findings The reviewed literature highlighted that there exist numerous scientific and technical means which can be adopted for improving the quality features of the 3D-printed PEEK-based biomedical structures. The discussed technological innovations will help the 3DP system to enhance the layer adhesion strength, structural stability, as well as enable the printing of high-performance thermoplastics. Originality/value The content of the present manuscript will motivate young scholars and senior scientists to work in exploring high-performance thermoplastics for 3DP applications.

Influence of airflow dynamics on vortices in the human nasal cavity

2019 ◽  
Vol 36 (9) ◽  
pp. 3164-3179
Author(s):  
Punjan Dohare ◽  
Amol P. Bhondekar ◽  
Anupma Sharma ◽  
C. Ghanshyam
Keyword(s):  
Numerical Simulations ◽  
Nasal Cavity ◽  
Three Dimensional ◽  
Nasal Airflow ◽  
Nasal Valve ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Flow Rates ◽  
Content Type ◽  
Human Nose

Purpose The purpose of this paper is to understand the effect of airflow dynamics on vortices for different flow rates using the human nose three-dimensional model. Design/methodology/approach Olfaction originates with air particles travelling from an external environment to the upper segment of the human nose. This phenomenon is generally understood by using the nasal airflow dynamics, which enhances the olfaction by creating the vortices in the human nose. An anatomical three-dimensional model of the human nasal cavity from computed tomography (CT) scan images using the MIMICS software (Materialise, USA) was developed in this study. Grid independence test was performed through volume flow rate, pressure drop from nostrils and septum and average velocity near the nasal valve region using a four computational mesh model. Computational fluid dynamics (CFD) was used to examine the flow pattern and influence of airflow dynamics on vortices in the nasal cavity. Numerical simulations were conducted for the flow rates of 7.5, 10, 15 and 20 L/min using numerical finite volume methods. Findings At coronal cross-sections, dissimilar nasal airflow patterns were observed for 7.5, 10, 15 and 20 L/min rate of fluid flow in the human nasal cavity. Vortices that are found at the boundaries with minimum velocity creates deceleration zone in the nose vestibule region, which is accompanied by flow segregation. Maximum vortices were observed in the nasal valve region and the posterior end of the turbinate region, which involves mixing and recirculation and is responsible for enhancing the smelling process. Practical implications The proposed analysis is applicable to design the sensor chamber for electronic noses. Originality/value In this paper, the influence of airflow dynamics on vortices in the human nasal cavity is discussed through numerical simulations.

Thermodynamic Analysis of Heat and Fluid Flow in a Microchannel With Internal Fins

2009 ◽  
Author(s):  
Ramesh Narayanaswamy ◽  
Tilak T. Chandratilleke ◽  
Andrew J. L. Foong
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Thermodynamic Analysis ◽  
Entropy Generation ◽  
High Performance ◽  
Numerical Study ◽  
Three Dimensional ◽  
Heat Sinks ◽  
Heat Transfer Fluid ◽  
Internal Fins

Efficient cooling techniques are one of the critical design requirements for maintaining reliable operational characteristics of modern, miniaturised high performance electronic components. Microchannel heat sinks form an integral part of most devices used for thermal management in electronic equipment cooling. A microchannel of square cross section, having internal longitudinal fins is considered for analysis. A numerical study is carried out to investigate the fluid flow and heat transfer characteristics. Three-dimensional numerical simulations are performed on the microchannel in the presence of a hydrodynamically developed, thermally developing laminar flow. Further on, a thermodynamic analysis is carried out, for a range of fin heights and thermophysical parameters, in order to obtain the irreversibilities due to heat transfer and fluid flow within the microchannel. An optimum fin height, corresponding to the thermodynamically optimum conditions that minimize the entropy generation rates has been obtained. The effect of the presence of internal fins on the entropy generated due to heat transfer, fluid friction, and the total entropy generation is also provided.

RISK OF ANEURYSMAL RUPTURE

Neurosurgery ◽  
2008 ◽  
Vol 62 (4) ◽  
pp. 767-775 ◽  
Author(s):  
Tomotaka Ohshima ◽  
Shigeru Miyachi ◽  
Ken-ichi Hattori ◽  
Ichiro Takahashi ◽  
Katsuya Ishii ◽  
...  
Keyword(s):  
Flow Separation ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Type A ◽  
Patient Specific ◽  
Parent Artery ◽  
Type B ◽  
Unruptured Aneurysms ◽  
Risk Of Rupture ◽  
Type C

Abstract OBJECTIVE The aim of the present study was to clarify the risk of rupture in terminal-type intracranial aneurysms using computational flow simulation analysis. METHODS First, idealized three-dimensional aneurysmal models were built from a solid voxel on the computer. We focused on round terminal-type aneurysms with the positioning of the neck orifice set according to the following three patterns in relationship to the axis of the parent artery: the Type-A neck orifice was positioned directly in line with the flow of the parent artery; the Type-B neck orifice was shifted 1.5 mm offline toward the unilateral branch; and the Type-C neck orifice was shifted 3 mm offline. Computational flow simulations were applied with Fujitsu α-Flow software (Fujitusu, Tokyo, Japan). We analyzed flow patterns using modified patient-specific models. We also investigated actual clinical situations to evaluate the differences in neck-orifice positioning between 20 ruptured aneurysms and 26 unruptured ones using three-dimensional angiograms. RESULTS The Type-A neck orifice showed completely symmetrical stream lines in the aneurysm, whereas the Type-C orifice showed a clear round circulation. The Type-B neck orifice, on the other hand, exhibited intra-aneurysmal flow separation. The clinical research demonstrated that Type-B aneurysms were more likely to be found in the ruptured group (P < 0.05). CONCLUSION Flow separation, recognized as one of the causes of intimal injury, could be observed only in Type-B aneurysms, a result that corresponded well with our clinical experience. From the flow-dynamics point of view, this positioning of the neck orifice may be one of the risk factors most likely to induce the rupture of unruptured aneurysms.

A Navier–Stokes Analysis of Airfoils in Oscillating Transonic Cascades for the Prediction of Aerodynamic Damping

1997 ◽  
Vol 119 (1) ◽  
pp. 77-84 ◽  
Author(s):  
R. S. Abhari ◽  
M. Giles
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Outer Region ◽  
Navier Stokes ◽  
Compressor Cascade ◽  
Time Step ◽  
Aerodynamic Damping ◽  
Transonic Compressor ◽  
Standard Configuration ◽  
The Impact

An unsteady, compressible, two-dimensional, thin shear layer Navier–Stokes solver is modified to predict the motion-dependent unsteady flow around oscillating airfoils in a cascade. A quasi-three-dimensional formulations is used to account for the stream-wise variation of streamtube height. The code uses Ni’s Lax–Wendroff algorithm in the outer region, an implicit ADI method in the inner region, conservative coupling at the interface, and the Baldwin–Lomax turbulence model. The computational mesh consists of an O-grid around each blade plus an unstructured outer grid of quadrilateral or triangular cells. The unstructured computational grid was adapted to the flow to better resolve shocks and wakes. Motion of each airfoil was simulated at each time step by stretching and compressing the mesh within the O-grid. This imposed motion consists of harmonic solid body translation in two directions and rotation, combined with the correct interblade phase angles. The validity of the code is illustrated by comparing its predictions to a number of test cases, including an axially oscillating flat plate in laminar flow, the Aeroelasticity of Turbomachines Symposium Fourth Standard Configuration (a transonic turbine cascade), and the Seventh Standard Configuration (a transonic compressor cascade). The overall comparison between the predictions and the test data is reasonably good. A numerical study on a generic transonic compressor rotor was performed in which the impact of varying the amplitude of the airfoil oscillation on the normalized predicted magnitude and phase of the unsteady pressure around the airfoil was studied. It was observed that for this transonic compressor, the nondimensional aerodynamic damping was influenced by the amplitude of the oscillation.

scholarly journals Numerical study on snow transport and drift formation

1993 ◽  
Vol 18 ◽  
pp. 135-141 ◽  
Author(s):  
Takahiko Uematsu
Keyword(s):  
Continuity Equation ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Density Field ◽  
Particle Movement ◽  
Snow Density ◽  
Fall Velocity ◽  
Snow Transport ◽  
Good Agreement

A three-dimensional, numerical simulation model for snow transport and drift formation is proposed in which saltation as well as suspension are considered as dynamic behavioral factors of moving snow particles. The procedure for simulation is as follows: (1) Air flow field is simulated solving the Reynolds equations and the continuity equation. (2) Using the result of the air field flow simulation, the blown-snow density field is simulated using the diffusion equations in which the fall velocity of blown snow particles is considered. In the boundary conditions, the particle movement of saltation is taken into consideration. (3) Finally, the snowdrift rate is computed based on the amount of snow particles not transported by saltation. This model was quantitatively tested for the phenomenon of snowdrift development. The computed results showed good agreement with observations.

NUMERICAL STUDY OF MUCOUS LAYER EFFECTS ON NASAL AIRFLOW

2012 ◽  
Vol 24 (04) ◽  
pp. 327-332 ◽  
Author(s):  
Chih Fang Lee ◽  
Kamarul Arifin Ahmad ◽  
Rushdan Ismail ◽  
Suzina Abdul Hamid
Keyword(s):  
Fluid Dynamics ◽  
Nasal Cavity ◽  
Layer Thickness ◽  
Cross Sections ◽  
Numerical Study ◽  
Three Dimensional ◽  
Nasal Airflow ◽  
Mucous Layer ◽  
Turbulent Airflow ◽  
Computational Fluid Dynamics Cfd

The aim of this study is to visualize and analyze the mucous layer effects towards the nasal airflow. Mucous layer had been neglected in previous works as it is considered a very thin layer along the nasal passageway. This paper discussed the effects in nasal airflow caused by the micrometer changes of the mucous layer thickness along the nasal passageway. Differences in maximum velocities caused by the mucous layer and visualization of the nasal airflow were studied. Computational fluid dynamics (CFD) was used to study three-dimensional nasal cavity of an adult Malaysian female. Six different models with various thickness of mucous layer within the range of 5–50 μm were implemented in the analysis with mass flow rate of 7.5 and 20 L/min. Mucous layer is assumed to be uniform, solid, and also stationary for this study. The results from all the six models were compared with the model with non-mucous effects. Based on both laminar and turbulent airflow simulations, it is shown that the addition of mucous layer thickness in analysis increased the maximum velocities at the four cross sections along the nasal cavity.

No Flow Underfill Process Development for Fine Pitch Flip Chip Silicon to Silicon Wafer Level Integration

2010 ◽  
Vol 2010 (DPC) ◽  
pp. 000708-000735 ◽  
Author(s):  
Zhaozhi Li ◽  
John L. Evans ◽  
Paul N. Houston ◽  
Brian J. Lewis ◽  
Daniel F. Baldwin ◽  
...  
Keyword(s):  
High Performance ◽  
Flip Chip ◽  
Process Development ◽  
Low Cost ◽  
Three Dimensional ◽  
High Yield ◽  
Process Time ◽  
Assembly Process ◽  
Wafer Level ◽  
Fine Pitch

The industry has witnessed the adoption of flip chip for its low cost, small form factor, high performance and great I/O flexibility. As the Three Dimensional (3D) packaging technology moves to the forefront, the flip chip to wafer integration, which is also a silicon to silicon assembly, is gaining more and more popularity. Most flip chip packages require underfill to overcome the CTE mismatch between the die and substrate. Although the flip chip to wafer assembly is a silicon to silicon integration, the underfill is necessary to overcome the Z-axis thermal expansion as well as the mechanical impact stresses that occur during shipping and handling. No flow underfill is of special interest for the wafer level flip chip assembly as it can dramatically reduce the process time as well as bring down the average package cost since there is a reduction in the number of process steps and the dispenser and cure oven that would be necessary for the standard capillary underfill process. Chip floating and underfill outgassing are the most problematic issues that are associated with no flow underfill applications. The chip floating is normally associated with the size/thickness of the die and volume of the underfill dispensed. The outgassing of the no flow underfill is often induced by the reflow profile used to form the solder joint. In this paper, both issues will be addressed. A very thin, fine pitch flip chip and 2x2 Wafer Level CSP tiles are used to mimic the assembly process at the wafer level. A chip floating model will be developed in this application to understand the chip floating mechanism and define the optimal no flow underfill volume needed for the process. Different reflow profiles will be studied to reduce the underfill voiding as well as improve the processing yield. The no flow assembly process developed in this paper will help the industry understand better the chip floating and voiding issues regarding the no flow underfill applications. A stable, high yield, fine pitch flip chip no flow underfill assembly process that will be developed will be a very promising wafer level assembly technique in terms of reducing the assembly cost and improving the throughput.

Drag and Cavity Development of Two Slender Bodies: A Numerical Study

2015 ◽  
Author(s):  
Yong-Du Jun ◽  
Kang-Sik Bae ◽  
Seok-Soon Lee ◽  
Jong Soo Lee
Keyword(s):  
Drag Coefficient ◽  
Stokes Equations ◽  
Numerical Study ◽  
Phase Interface ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Navier Stokes ◽  
Slender Bodies ◽  
Cavity Development ◽  
Disk Cavitator

In the present study, an unsteady three-dimensional flow simulation based on the RANS (Reynolds Average Navier-Stokes) equations with k-ε turbulence model and Singhal et al.’s cavitation model is conducted to study the cavity development behavior of two slender bodies, that is, a flat-headed cylinder and a step-headed cylinder of 50 mm in length and 10 mm in diameter. Using so called VOF method to track the liquid-vapor phase interface, time dependent solutions with varying approach speed range from 10 m/s to 55 m/s are obtained and analyzed to provide key information such as cavity initiation speed, drag coefficient and the cavity shape and size (max. length and diameter). The implemented numerical model is validated for flows over a flat disk cavitator against the experimental correlation. According to the present simulation results, slender bodies with two different head shapes, that is, a flat cylinder and a stepped one, respectively, showed very close behavior in their cavity initiation speed, maximum developed cavity diameter and length, but consistently lower drag coefficient with the step-headed cylinder case, which suggests the possible advantage of seeking optimized cavitator shape.

Numerical Study of Nonreacting Gas Turbine Combustor Swirl Flow Using Reynolds Stress Model

2003 ◽  
Vol 125 (3) ◽  
pp. 804-811 ◽  
Author(s):  
S. L. Yang ◽  
Y. K. Siow ◽  
B. D. Peschke ◽  
R. R. Tacina
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Reynolds Stress Model ◽  
Swirl Flow ◽  
High Degree

This paper presents recent research on the use of a Reynolds stress turbulence model (RSTM) for three-dimensional flowfield simulation inside gas turbine combustors. It intends to show the motivations for using the RSTM in engine flow simulation, to present a further validation of the RSTM implementation in the KIVA code using the available experimental data, and to provide comparisons between RSTM and k-ε turbulence model results for chemically nonreacting swirling flows. The results show that, for high-degree swirl flow, the RSTM can provide predictions in favorable agreement with the experimental data, and that the RSTM predicts recirculations and high velocity gradients better than does the k-ε turbulence model. The results also indicate that the choice of swirler has a significant influence on the structure of the combustor flowfield.

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