Verification of Turbulence Models for Flow in a Constricted Pipe at Low Reynolds Number

Khalili, Fardin; Gamage, Peshala T.; Mansy, Hansen A.

doi:10.1615/tfec2018.tfl.021662

Cited by 13 publications

(21 citation statements)

References 40 publications

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“…CFD may also provide valuable information to speed up the design of implantable devices during the prototype development [ 29 ] and reduce the costs and risks associated with new heart valve designs [ 30 ]. Hence, analysis of flow dynamics and the resulting turbulence [ 31 , 32 , 33 , 34 ] and sounds [ 35 , 36 , 37 , 38 , 39 , 40 ] has been an active area of research.…”

Section: Introductionmentioning

confidence: 99%

Adverse Hemodynamic Conditions Associated with Mechanical Heart Valve Leaflet Immobility

et al. 2018

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Artificial heart valves may dysfunction, leading to thrombus and/or pannus formations. Computational fluid dynamics is a promising tool for improved understanding of heart valve hemodynamics that quantify detailed flow velocities and turbulent stresses to complement Doppler measurements. This combined information can assist in choosing optimal prosthesis for individual patients, aiding in the development of improved valve designs, and illuminating subtle changes to help guide more timely early intervention of valve dysfunction. In this computational study, flow characteristics around a bileaflet mechanical heart valve were investigated. The study focused on the hemodynamic effects of leaflet immobility, specifically, where one leaflet does not fully open. Results showed that leaflet immobility increased the principal turbulent stresses (up to 400%), and increased forces and moments on both leaflets (up to 600% and 4000%, respectively). These unfavorable conditions elevate the risk of blood cell damage and platelet activation, which are known to cascade to more severe leaflet dysfunction. Leaflet immobility appeared to cause maximal velocity within the lateral orifices. This points to the possible importance of measuring maximal velocity at the lateral orifices by Doppler ultrasound (in addition to the central orifice, which is current practice) to determine accurate pressure gradients as markers of valve dysfunction.

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Section: Introductionmentioning

confidence: 99%

Adverse Hemodynamic Conditions Associated with Mechanical Heart Valve Leaflet Immobility

et al. 2018

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“…Cardiovascular disease is a leading cause of death in the world. Analysis of blood flow dynamics [20]- [26] and heart related signals might result in improving current diagnostic methods, and eventually decreasing the mortality rate associated with cardiovascular disease. Cardiac time intervals (CTIs) have been widely used as clinical metrics for cardiovascular diagnosis.…”

Section: Application In Cardiovascular Diagnosismentioning

confidence: 99%

Heart Rate Monitoring During Different Lung Volume Phases Using Seismocardiography

et al. 2018

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Seismocardiography (SCG) is a non-invasive method that can be used for cardiac activity monitoring. This paper presents a new electrocardiogram (ECG) independent approach for estimating heart rate (HR) during low and high lung volume (LLV and HLV, respectively) phases using SCG signals. In this study, SCG, ECG, and respiratory flow rate (RFR) signals were measured simultaneously in 7 healthy subjects. The lung volume information was calculated from the RFR and was used to group the SCG events into low and high lung-volume groups. LLV and HLV SCG events were then used to estimate the subjects HR as well as the HR during LLV and HLV in 3 different postural positions, namely supine, 45 degree heads-up, and sitting. The performance of the proposed algorithm was tested against the standard ECG measurements. Results showed that the HR estimations from the SCG and ECG signals were in a good agreement (bias of 0.08 bpm). All subjects were found to have a higher HR during HLV (HRHLV) compared to LLV (HRLLV) at all postural positions. The HRHLV/HRLLV ratio was 1.11±0.07, 1.08±0.05, 1.09±0.04, and 1.09±0.04 (mean±SD) for supine, 45 degree-first trial, 45 degree-second trial, and sitting positions, respectively. This heart rate variability may be due, at least in part, to the well-known respiratory sinus arrhythmia. HR monitoring from SCG signals might be used in different clinical applications including wearable cardiac monitoring systems.

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“…Detailed description of the mesh, CFD model and validation against LDA measurements can be found in previous studies. [7][8][9] A time step of 0.0001 seconds was used in the simulations. The density and the dynamic viscosity of the air were selected as 1.184 kgm -3 and 1.855×10 -5 Pa.s, respectively.…”

Section: Computational Modellingmentioning

confidence: 99%

“…Here, the minimum value of the velocity scale is limited to 1 ms -1 to get a clear representation of the different flow regions observed in the flow domain, which were similar to previous studies, 13,14 More details about CFD results can be found in the previous study. 8 A volumetric representation of the APE acoustic sources (source term: Figure 2B. The acoustic sources seem to appear from the edges of the constriction and stay as more organized structures in the "flow jet and separation region".…”

Section: Computational Modellingmentioning

confidence: 99%

“…The detailed description of the CFD simulation and the experimental measurements can be found in previous studies. [7][8][9] CAA simulation results were validated by comparing the simulated sound pressure spectra with measured sound pressure spectra at different points on the pipe wall. Furthermore, CAA simulation results were analyzed to study the acoustic sources and acoustic propagation in the pipe.…”

Section: Introductionmentioning

confidence: 99%

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Aero–acoustics in constricted pipe flow at low mach number

Gamage

Khalili

Mansy

2018

JABB

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In this study, the sound generation in a constricted pipe at low Mach number (M=0.003, Re=1170 at the inlet) flow is investigated using a hybrid modeling approach of computational aero-acoustics (CAA). Large Eddy Simulation (LES) model is used simulate the flow and accurately capture the flow instabilities associated with the constriction. The Acoustic Perturbation Equation (APE) method is used to model the acoustic field where the source terms are derived from the incompressible flow simulation results. The acoustic spectra from the APE simulation results showed good agreement (within 9%) with measured values on the pipe wall downstream of the constriction. The strongest APE acoustic sources were found to occur in the jet core breakdown region that contained the highest pressure fluctuations in the flow field. Proper Orthogonal Decomposition (POD) was used to study the Coherent flow structures in the jet core breakdown region in order to further understand the characteristics of acoustic sources. The strongest structure corresponds to the peak frequency of the measured sound pressure spectra. The study results improve our understanding of the sound generation mechanisms in biomedical applications involving the airways such as phonation and partial airway obstruction.

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Verification of Turbulence Models for Flow in a Constricted Pipe at Low Reynolds Number

Cited by 13 publications

References 40 publications

Adverse Hemodynamic Conditions Associated with Mechanical Heart Valve Leaflet Immobility

Adverse Hemodynamic Conditions Associated with Mechanical Heart Valve Leaflet Immobility

Heart Rate Monitoring During Different Lung Volume Phases Using Seismocardiography

Aero–acoustics in constricted pipe flow at low mach number

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