scholarly journals 1D network simulations for evaluating regional flow and pressure distributions in healthy and asthmatic human lungs

2019 ◽  
Vol 127 (1) ◽  
pp. 122-133 ◽  
Author(s):  
Sanghun Choi ◽  
Sujin Yoon ◽  
Jichan Jeon ◽  
Chunrui Zou ◽  
Jiwoong Choi ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Airway Resistance ◽  
Flow Distribution ◽  
Lung Compliance ◽  
Cfd Model ◽  
4D Ct ◽  
Regional Flow ◽  
Airway Constriction ◽  
Region Model ◽  
Computational Fluid Dynamics Cfd

This study aimed to introduce a one-dimensional (1D) computational fluid dynamics (CFD) model for airway resistance and lung compliance to examine the relationship between airway resistance, pressure, and regional flow distribution. We employed five healthy and five asthmatic subjects who had dynamic computed tomography (CT) scans (4D CT) along with two static scans at total lung capacity and functional residual capacity. Fractional air-volume change ([Formula: see text]) from 4D CT was used for a validation of the 1D CFD model. We extracted the diameter ratio from existing data sets of 61 healthy subjects for computing mean and standard deviation (SD) of airway constriction/dilation in CT-resolved airways. The lobar mean (SD) of airway constriction/dilation was used to determine diameters of CT-unresolved airways. A 1D isothermal energy balance equation was solved, and pressure boundary conditions were imposed at the acinar region ( model A) or at the pleural region ( model B). A static compliance model was only applied for model B to link acinar and pleural regions. The values of 1D CFD-derived [Formula: see text] for model B demonstrated better correlation with 4D CT-derived [Formula: see text] than model A. In both inspiration and expiration, asthmatic subjects with airway constriction show much greater pressure drop than healthy subjects without airway constriction. This increased transpulmonary pressures in the asthmatic subjects, leading to an increased workload (hysteresis). The 1D CFD model was found to be useful in investigating flow structure, lung hysteresis, and pressure distribution for healthy and asthmatic subjects. The derived flow distribution could be used for imposing boundary conditions of 3D CFD. NEW & NOTEWORTHY A one-dimensional (1D) computational fluid dynamics (CFD) model for airway resistance and lung compliance was introduced to examine the relationship between airway resistance, pressure, and regional flow distribution. The 1D CFD model investigated differences of flow structure, lung hysteresis, and pressure distribution for healthy and asthmatic subjects. The derived flow distribution could be used for imposing boundary conditions of three-dimensional CFD.

Numerical Study of the Winter-Kennedy Method—A Sensitivity Analysis

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Binaya Baidar ◽  
Jonathan Nicolle ◽  
Chirag Trivedi ◽  
Michel J. Cervantes
Keyword(s):  
Boundary Conditions ◽  
Secondary Flow ◽  
Numerical Study ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Local Flow ◽  
Spiral Case ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Changes

The Winter-Kennedy (WK) method is commonly used in relative discharge measurement and to quantify efficiency step-up in hydropower refurbishment projects. The method utilizes the differential pressure between two taps located at a radial section of a spiral case, which is related to the discharge with the help of a coefficient and an exponent. Nearly a century old and widely used, the method has shown some discrepancies when the same coefficient is used after a plant upgrade. The reasons are often attributed to local flow changes. To study the change in flow behavior and its impact on the coefficient, a numerical model of a semi-spiral case (SC) has been developed and the numerical results are compared with experimental results. The simulations of the SC have been performed with different inlet boundary conditions. Comparison between an analytical formulation with the computational fluid dynamics (CFD) results shows that the flow inside an SC is highly three-dimensional (3D). The magnitude of the secondary flow is a function of the inlet boundary conditions. The secondary flow affects the vortex flow distribution and hence the coefficients. For the SC considered in this study, the most stable WK configurations are located toward the bottom from θ=30deg to 45deg after the curve of the SC begins, and on the top between two stay vanes.

scholarly journals A New Device used in Selective Withdrawal from Reservoirs and its Effectiveness Verified in Computational Fluid Dynamics

2018 ◽  
Vol 14 (03) ◽  
pp. 142
Author(s):  
Jinsuo Lu ◽  
Wei Zhang ◽  
Dengyu Wang ◽  
Xiaoyi Wang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Layer Thickness ◽  
Water Intake ◽  
Flow Distribution ◽  
Water Layer ◽  
Cfd Model ◽  
Selective Withdrawal ◽  
New Device ◽  
Computational Fluid Dynamics Cfd

<p class="16">Water intake with fixed height limits the application of selective withdrawal technology in a certain degree. This study proposes a technological idea to install baffles on water intake. Through the rotation of upper and lower baffle, poor water layer can be blocked. A Computational Fluid Dynamics (CFD) model for the upper baffle on water intake is constructed. The results show that the baffle installed on the upper part of orifice can reduce the withdrawal layer thickness and flow on the upper part of orifice centre. Thereby, the withdrawal flow on lower part can be indirectly increased. While, baffle length and inclining angle are the important factors to influence the withdrawal layer thickness and flow distribution. Therefore, the adjusting range of selective withdrawal can be economically enhanced by installing baffles on water intake.</p>

scholarly journals An Investigation of the Flow Distribution Inside a Radial Sidestream Inlet of a Centrifugal Compressor

2000 ◽  
Author(s):  
Zheji Liu ◽  
D. Lee Hill ◽  
Gary Colby
Keyword(s):  
Test Data ◽  
Centrifugal Compressor ◽  
Flow Distribution ◽  
Production Test ◽  
Cfd Model ◽  
Cfd Models ◽  
Multi Stage ◽  
Final Design ◽  
Computational Fluid Dynamics Cfd ◽  
Return Channel

A radial sidestream inlet is commonly utilized in multi-stage centrifugal compressors to introduce additional gas into the mid-stage of the compressor. The flow distribution after the junction of the sidestream and the main return channel of the upstream stage can significantly affect the performance of the next stage. In this study, the mixing between the fluid from the sidestream component and the fluid from the main return channel was investigated numerically using Computational Fluid Dynamics (CFD). A variety of CFD models of different geometry, different boundary conditions, and different grid density were developed to analyze the uniformity of the flow entering the impeller of the next stage. The flow distribution difference between the sidestream CFD model and the CFD model with the sidestream coupled to the main return channel suggests that both the return channel and the sidestream have to be modeled together to get meaningful results. The results of this effort were used in conjunction with production test data to help resolve a performance shortfall of a multi-stage centrifugal compressor with sidestream injection. The test data from the final design is also provided to show the resulting improvement in head rise.

Modeling of High Temperature Gas Flow 3D Distribution in BF Throat Based on the Computational Fluid Dynamics

2015 ◽  
Vol 19 (2) ◽  
pp. 269-276 ◽  
Author(s):  
Jian Qi An ◽  
◽  
Kai Peng ◽  
Wei Hua Cao ◽  
Min Wu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gas Flow ◽  
Numerical Solutions ◽  
Flow Distribution ◽  
Three Dimensions ◽  
Cfd Model ◽  
Ansys Fluent ◽  
Proposed Model ◽  
Computational Fluid Dynamics Cfd

This paper aims at building a Computational Fluid Dynamics (CFD) model which can describe the gas flow three dimensions (3D) distribution in blast furnace (BF) throat. Firstly, the boundary conditions are obtained by rebuilding central gas flow shape in BF based on computer graphics. Secondly, the CFD model is built based on turbulent model by analyzing the features of gas flow. Finally, a method which can get the numerical solutions of the model is proposed by using CFD software ANSYS/FLUENT. The proposed model can reflect the changes of the gas flow distribution, and can help to guide the operation of furnace burdening and to ensure the BF stable and smooth production.

Cluster of High-Powered Racks Within a Raised-Floor Computer Data Center: Effect of Perforated Tile Flow Distribution on Rack Inlet Air Temperatures

2004 ◽  
Vol 126 (4) ◽  
pp. 510-518 ◽  
Author(s):  
Roger Schmidt ◽  
Ethan Cruz
Keyword(s):  
Data Center ◽  
Control Volume ◽  
Flow Distribution ◽  
Computer Code ◽  
Cfd Model ◽  
Computer Data ◽  
Air Temperatures ◽  
Finite Control ◽  
Computational Fluid Dynamics Cfd ◽  
Tile Flow

This paper focuses on the effect on rack inlet air temperatures as a result of maldistribution of airflows exiting the perforated tiles located adjacent to the fronts of the racks. The flow distribution exiting the perforated tiles was generated from a computational fluid dynamics (CFD) tool called Tileflow (trademark of Innovative Research, Inc.). Both raised floor heights and perforated tile-free areas were varied in order to explore the effect on rack inlet temperatures. The flow distribution exiting the perforated tiles was used as boundary conditions to the above-floor CFD model. A CFD model was generated for the room with electronic equipment installed on a raised floor. Forty racks of data processing (DP) equipment were arranged in rows in a data center cooled by chilled air exhausting from perforated floor tiles. The chilled air was provided by four A/C units placed inside a room 12.1 m wide×13.4 m long. Because the arrangement of the racks in the data center was symmetric, only half of the data center was modeled. The numerical modeling for the area above the raised floor was performed using a commercially available finite control volume computer code called Flotherm (trademark of Flomerics, Inc.). The flow was modeled using the k-e turbulence model. Results are displayed to provide some guidance on the design and layout of a data center.

Cluster of High Powered Racks Within a Raised Floor Computer Data Center: Effect of Perforated Tile Flow Distribution on Rack Inlet Air Temperatures

2003 ◽  
Author(s):  
Roger Schmidt ◽  
Ethan Cruz
Keyword(s):  
Data Center ◽  
Control Volume ◽  
Flow Distribution ◽  
Computer Code ◽  
Cfd Model ◽  
Computer Data ◽  
Air Temperatures ◽  
Finite Control ◽  
Computational Fluid Dynamics Cfd ◽  
Tile Flow

This paper focuses on the effect on inlet rack air temperatures as a result of maldistribution of airflows exiting the perforated tiles located adjacent to the fronts of the racks. The flow distribution exiting the perforated tiles was generated from a computational fluid dynamics (CFD) tool called Tileflow (Trademark of Innovative Research, Inc.). Both raised floor heights and perforated tile free area were varied in order to explore the effect on rack inlet temperatures. The flow distribution exiting the perforated tiles was used as boundary conditions to the above floor CFD model. A CFD model was generated for the room with electronic equipment installed on a raised floor. Fourty racks of data processing (DP) equipment were arranged in rows in a data center cooled by chilled air exhausting from perforated floor tiles. The chilled air was provided by four A/C units placed inside a room 12.1 m wide × 13.4 m long. Since the arrangement of the racks in the data center was symmetric only one-half of the data center was modeled. The numerical modeling for above the raised floor was performed using a commercially available finite control volume computer code called Flotherm (Trademark of Flomerics, Inc.). The flow was modeled using the k-e turbulence model. Results are displayed to provide some guidance on the design and layout of a data center.

Effects of Over Fire Air on the Combustion and NOx Emission Characteristics of a 600 MW Opposed Swirling Fired Boiler

2012 ◽  
Vol 512-515 ◽  
pp. 2135-2142 ◽  
Author(s):  
Yu Peng Wu ◽  
Zhi Yong Wen ◽  
Yue Liang Shen ◽  
Qing Yan Fang ◽  
Cheng Zhang ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Empirical Method ◽  
Nox Emission ◽  
Emission Characteristics ◽  
Cfd Model ◽  
Nitrogen Release ◽  
Computational Fluid Dynamics Cfd ◽  
Low Nox Emission

A computational fluid dynamics (CFD) model of a 600 MW opposed swirling coal-fired utility boiler has been established. The chemical percolation devolatilization (CPD) model, instead of an empirical method, has been adapted to predict the nitrogen release during the devolatilization. The current CFD model has been validated by comparing the simulated results with the experimental data obtained from the boiler for case study. The validated CFD model is then applied to study the effects of ratio of over fire air (OFA) on the combustion and nitrogen oxides (NOx) emission characteristics. It is found that, with increasing the ratio of OFA, the carbon content in fly ash increases linearly, and the NOx emission reduces largely. The OFA ratio of 30% is optimal for both high burnout of pulverized coal and low NOx emission. The present study provides helpful information for understanding and optimizing the combustion of the studied boiler

Validation of a Computationally Efficient Computational Fluid Dynamics (CFD) Model for Industrial Bubble Column Bioreactors

2014 ◽  
Vol 53 (37) ◽  
pp. 14526-14543 ◽  
Author(s):  
Dale D. McClure ◽  
Hannah Norris ◽  
John M. Kavanagh ◽  
David F. Fletcher ◽  
Geoffrey W. Barton
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Bubble Column ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Computational Fluid Dynamics Cfd

Fast CT-FFR Analysis Method for the Coronary Artery Based on 4D-CT Image Analysis and Structural and Fluid Analysis

2015 ◽  
Author(s):  
Mitsuaki Kato ◽  
Kenji Hirohata ◽  
Akira Kano ◽  
Shinya Higashi ◽  
Akihiro Goryu ◽  
...  
Keyword(s):  
Blood Flow ◽  
Coronary Artery ◽  
Boundary Conditions ◽  
Coronary Arteries ◽  
Computational Time ◽  
Ct Image ◽  
Analysis Method ◽  
Fractional Flow ◽  
4D Ct ◽  
Fluid Analysis

Non invasive fractional flow reserve derived from CT coronary angiography (CT-FFR) has to date been typically performed using the principles of computational fluid analysis in which a lumped parameter coronary vascular bed model is assigned to represent the impedance of the downstream coronary vascular networks absent in the computational domain for each coronary outlet. This approach may have a number of limitations. It may not account for the impact of the myocardial contraction and relaxation during the cardiac cycle, patient-specific boundary conditions for coronary artery outlets and vessel stiffness. We have developed a novel approach based on 4D-CT image tracking (registration) and structural and fluid analysis based on one dimensional mechanical model, to address these issues. In our approach, we analyzed the deformation variation of vessels and the volume variation of vessels to better define boundary conditions and stiffness of vessels. We focused on the blood flow and vessel deformation of coronary arteries and aorta near coronary arteries in the diastolic cardiac phase from 70% to 100 %. The blood flow variation of coronary arteries relates to the deformation of vessels, such as expansion and contraction of the cross-sectional area, during this period where resistance is stable, pressure loss is approximately proportional to flow. We used a statistical estimation method based on a hierarchical Bayes model to integrate 4D-CT measurements and structural and fluid analysis data. Under these analysis conditions, we performed structural and fluid analysis to determine pressure, flow rate and CT-FFR. Furthermore, the reduced-order model based on fluid analysis was studied in order to shorten the computational time for 4D-CT-FFR analysis. The consistency of this method has been verified by a comparison of 4D-CT-FFR analysis results derived from five clinical 4D-CT datasets with invasive measurements of FFR. Additionally, phantom experiments of flexible tubes with and without stenosis using pulsating pumps, flow sensors and pressure sensors were performed. Our results show that the proposed 4D-CT-FFR analysis method has the potential to accurately estimate the effect of coronary artery stenosis on blood flow.

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