Computational modelling and analysis of haemodynamics in a simple model of aortic stenosis

2018 ◽  
Vol 851 ◽  
pp. 23-49 ◽  
Author(s):  
Chi Zhu ◽  
Jung-Hee Seo ◽  
Rajat Mittal
Keyword(s):  
Simple Model ◽  
Aortic Stenosis ◽  
Secondary Flow ◽  
Pressure Fluctuation ◽  
Computational Modelling ◽  
Maximum Pressure ◽  
Cardiac Auscultation ◽  
Curved Pipe ◽  
Free Jet ◽  
Wall Pressure Fluctuation

In a study motivated by considerations associated with heart murmurs and cardiac auscultation, numerical simulations are used to analyse the haemodynamics in a simple model of an aorta with an aortic stenosis. The aorta is modelled as a curved pipe with a$180^{\circ }$turn, and three different stenoses with area reductions of 50 %, 62.5 % and 75 % are examined. A uniform steady inlet velocity with a Reynolds number of 2000 is used for all of the cases and direct numerical simulation is employed to resolve the dynamics of the flow. The poststenotic flow is dominated by the jet that originates from the stenosis as well as the secondary flow induced by the curvature, and both contribute significantly to the flow turbulence. On the anterior surface of the modelled aorta, the location with maximum pressure fluctuation, which may be considered as the source location for the murmurs, is found to be located around$60^{\circ }$along the aortic arch, and this location is relatively insensitive to the severity of the stenosis. For all three cases, this high-intensity wall pressure fluctuation includes contributions from both the jet and the secondary flow. Spectral analysis shows that for all three stenoses, the Strouhal number of the vortex shedding of the jet shear layer is close to 0.93, which is higher than the shedding frequency of a corresponding free jet or a jet confined in a straight pipe. This frequency also appears in the pressure spectra at the location postulated as the source of the murmurs, in the form of a ‘break frequency.’ The implications of these findings for cardiac auscultation-based diagnosis of aortic stenosis are also discussed.

Computational Modeling and Analysis of Murmurs Generated by Modeled Aortic Stenoses

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Chi Zhu ◽  
Jung-Hee Seo ◽  
Rajat Mittal
Keyword(s):  
Aortic Stenosis ◽  
Numerical Study ◽  
Computational Modelling ◽  
Sound Intensity ◽  
Elliptic Cylinder ◽  
Intensity Pattern ◽  
Modeling And Analysis ◽  
Curved Pipe ◽  
Epidermal Surface ◽  
History Of

In this study, coupled hemodynamic–acoustic simulations are employed to study the generation and propagation of murmurs associated with aortic stenoses where the aorta with a stenosed aortic valve is modeled as a curved pipe with a constriction near the inlet. The hemodynamics of the poststenotic flow is investigated in detail in our previous numerical study (Zhu et al., 2018, “Computational Modelling and Analysis of Haemodynamics in a Simple Model of Aortic Stenosis,” J. Fluid Mech., 851, pp. 23–49). The temporal history of the pressure on the aortic lumen is recorded during the hemodynamic study and used as the murmur source in the acoustic simulations. The thorax is modeled as an elliptic cylinder and the thoracic tissue is assumed to be homogeneous, linear and viscoelastic. A previously developed high-order numerical method that is capable of dealing with immersed bodies is applied in the acoustic simulations. To mimic the clinical practice of auscultation, the sound signals from the epidermal surface are collected. The simulations show that the source of the aortic stenosis murmur is located at the proximal end of the aortic arch and that the sound intensity pattern on the epidermal surface can predict the source location of the murmurs reasonably well. Spectral analysis of the murmur reveals the disconnect between the break frequency obtained from the flow and from the murmur signal. Finally, it is also demonstrated that the source locations can also be predicted by solving an inverse problem using the free-space Green's function. The implications of these results for cardiac auscultation are discussed.

Wall pressure-fluctuation spectra at small backward-facing steps

2000 ◽  
Author(s):  
B. Efimtsov ◽  
N. Kozlov ◽  
S. Kravchenko ◽  
A. Andersson
Keyword(s):  
Pressure Fluctuation ◽  
Wall Pressure ◽  
Wall Pressure Fluctuation

scholarly journals Steady and unsteady flow of non-newtonian fluid in curved pipe with triangular

2006 ◽  
Vol 3 (3) ◽  
pp. 470-480
Author(s):  
Baghdad Science Journal
Keyword(s):  
Unsteady Flow ◽  
Pressure Gradient ◽  
Secondary Flow ◽  
Cross Section ◽  
Numerical Study ◽  
Equations Of Motion ◽  
Curved Pipe ◽  
First Case ◽  
Stable Flow ◽  
Flow Cross

This paper deals with numerical study of the flow of stable and fluid Allamstqr Aniotina in an area surrounded by a right-angled triangle has touched particularly valuable secondary flow cross section resulting from the pressure gradient In the first case was analyzed stable flow where he found that the equations of motion that describe the movement of the fluid

Effect of Wakes and Secondary Flow on Re-attachment of Turbine Exit Annular Diffuser Flow

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
David Kluß ◽  
Horst Stoff ◽  
Alexander Wiedermann
Keyword(s):  
New York ◽  
Secondary Flow ◽  
Internal Flow ◽  
Free Jet ◽  
Diffuser Flow ◽  
Ansys Cfx ◽  
Flow Phenomena ◽  
Annular Diffuser ◽  
Commercial Solver ◽  
Turbine Exhaust

In this paper numerical results of wake and secondary flow interaction in diffuser flow fields are discussed. The wake and secondary flow are generated by a rotating wheel equipped with 30 cylindrical spokes with a diameter of 10 mm as a first approach to the turbine exit flow environment. The apex angle of the diffuser is chosen such that the flow is strongly separated according to the well-known performance charts of Sovran and Klomp (1967, “Experimentally Determined Optimum Geometries for Rectilinear Diffusers With Rectangular, Conical or Annular Cross-Section,” in Fluid Mechanics of Internal Flow, Elsevier, New York, pp. 272–319). This configuration has been tested in an experimental test rig at the Leibniz University Hannover (Sieker and Seume 2007, “Influence of Rotating Wakes on Separation in Turbine Exhaust Diffusers,” Paper No. ISAIF8-54). According to these experiments, the flow in the diffuser separates as free jet for low rotational speeds of the spoke-wheel, as expected by theory. However, if the 30 spokes of the upstream wheel rotate beyond the value of 500 rpm the measurements indicate that the flow remains attached to the outer diffuser wall. It will be shown by the present numerical analysis with the commercial solver ANSYS CFX-10.0 that only an unsteady approach using the elaborate scale adaptive simulation with the shear stress transport turbulence model is capable of predicting the stabilizing effect of the rotating wheel to the diffuser flow at larger rotational speeds. The favorable comparison with the experimental data suggests that the mixing effect of wakes and secondary flow pattern is responsible for the reattachment. As a result of our studies, it can be stated that the considerably higher numerical costs associated with unsteady calculations must be accepted in order to increase the understanding of the physical flow phenomena in turbine exit flow and its interaction with the downstream diffuser.

scholarly journals Subaortic stenosis and mitral dysplasia in three Black Russian Terrier puppies

2012 ◽  
Vol 50 (No. 7) ◽  
pp. 321-326
Author(s):  
J. Pikula ◽  
J. Pikulova ◽  
H. Bandouchova ◽  
P. Kohout ◽  
K. Najman ◽  
...  
Keyword(s):  
Mitral Valve ◽  
Aortic Stenosis ◽  
Left Ventricular Outflow Tract ◽  
Ventricular Outflow Tract ◽  
Left Ventricular ◽  
Outflow Tract ◽  
Subaortic Stenosis ◽  
Maximum Pressure ◽  
Mitral Insufficiency ◽  
Left Ventricular Outflow

A combined congenital heart defect of aortic stenosis and mitral dysplasia was diagnosed in three Black Russian Terrier puppies two months old. The aortic stenosis component included both fixed and dynamic obstructions. The fixed obstruction was subvalvularly located at the entrance to the left ventricular outflow tract. The dynamic obstruction was caused by the septal leaflet of the mitral valve protruding into the left ventricular outflow tract. Mitral dysplasia resulted in mitral insufficiency leading to regurgitation through the mitral valve closer to the septal side. The maximum pressure gradient across the aortic valve amounting to 103 mmHg measured in one puppy was consistent with the most severe grade of stenosis. The diagnosis was confirmed by autopsy in all three puppies that were males and originated in one litter, so genetic influences are supposed.

scholarly journals Flow Pressure Behavior Downstream of Ski Jumps

Fluids ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 168 ◽  
Author(s):  
Agostino Lauria ◽  
Giancarlo Alfonsi ◽  
Ali Tafarojnoruz
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Dynamic Pressure ◽  
Pressure Head ◽  
Navier Stokes ◽  
Maximum Pressure ◽  
Navier Stokes Equations ◽  
Free Jet ◽  
Jet Characteristics ◽  
The Impact

Ski jump spillways are frequently implemented to dissipate energy from high-speed flows. The general feature of this structure is to transform the spillway flow into a free jet up to a location where the impact of the jet creates a plunge pool, representing an area for potential erosion phenomena. In the present investigation, several tests with different ski jump bucket angles are executed numerically by means of the OpenFOAM® digital library, taking advantage of the Reynolds-averaged Navier–Stokes equations (RANS) approach. The results are compared to those obtained experimentally by other authors as related to the jet length and shape, obtaining physical insights into the jet characteristics. Particular attention is given to the maximum pressure head at the tailwater. Simple equations are proposed to predict the maximum dynamic pressure head acting on the tailwater, as dependent upon the Froude number, and the maximum pressure head on the bucket. Results of this study provide useful suggestions for the design of ski jump spillways in dam construction.

Intrinsic Mode Entropy Analysis of Tube-Wall Pressure Fluctuation Signals in the Kenics Static Mixer

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Hui-Bo Meng ◽  
Zhi-Qiang Liu ◽  
Yan-Fang Yu ◽  
Qiang Xiong ◽  
Jian-Hua Wu
Keyword(s):  
Pressure Fluctuation ◽  
Tube Wall ◽  
Sample Entropy ◽  
Wall Pressure ◽  
High Frequency Component ◽  
Static Mixer ◽  
Flow Rates ◽  
Multi Scale ◽  
Wall Pressure Fluctuation ◽  
Macro Scale

The multi-scale nonlinear hydrodynamics in Kenics Static Mixer (KSM) with 100 mm in diameter and 2 in aspect ratio was investigated in this work. The time series of tube-wall pressure fluctuation signals were measured at different flow rates ranged of 100~600 L•h-1 and at different axial positions in the range of 420~580 mm away from the cross-section of mixer inlet. It is difficult for composite signals to make an effective analysis by Sample Entropy (SampEn) based on a single scale. The complexity of tube-wall pressure fluctuation signals in a Kenics static mixer was investigated using Intrinsic Mode Entropy (IMEn) based on Sample Entropy algorithm and Empirical Mode Decomposition (EMD) method. Data sampling length and tolerance are optimized based on intrinsic mode entropy. Results of multi-scale analysis of pressure fluctuations indicated that the Sample entropy reaches maximum in the first scale and progressively decreases according to increase of the decomposed order. It is clear that the movement of high frequency component of the pressure signal is the most complicated and is rich in randomness. With the decomposition scales increasing, the complexity of signal decreases and approaches periodic motion eventually. The intrinsic mode entropy of the tube wall pressure signals in KSM has similar development tendencies in different flow rates. Besides, as the flow rates increased, the macro-scale vortexes play a more and more important role and guide the system to develop toward the stable state.

Effects of Trailing Edge Position of Splitter Blade on the Pressure Pulsation in a Low Specific Centrifugal Pump

2019 ◽  
Author(s):  
Jinfeng Zhang
Keyword(s):  
Velocity Distribution ◽  
Turbulence Intensity ◽  
Pressure Fluctuation ◽  
Relative Velocity ◽  
Pressure Pulsation ◽  
Suction Side ◽  
Maximum Pressure ◽  
Trailing Edge ◽  
Flow Rates ◽  
Pulsation Amplitude

Abstract A combination of experimental and numerical simulation was carried out to analyze influence of trailing edge position of splitter blade on the pressure fluctuation in low specific pumps with and without splitter blades under different flow rates. Performance experiments and PIV tests were performed to verify the results of numerical calculation. Several monitor points were placed in the calculation model pump to collect the pressure fluctuation signals, which were processed by Fast Fourier Transform to obtain the frequency results for further analysis. Besides, turbulence intensity and relative velocity distribution were also analyzed in regions of impeller and volute. The results showed that compared with prototype without splitter blade and the splitter blade schemes, when the trailing edge of splitter blade deviates to the suction side of main blade, the maximum pressure pulsation amplitudes are the lowest at different monitoring points of model pump. And the variation of pressure pulsation amplitude in this scheme is relatively stable with the change of flow rates compared with other schemes. Furthermore, the splitter blade scheme with an appropriate trailing edge position has the lowest average turbulence intensity and optimal relative velocity distribution in main flow passage component. Therefore, this paper proposes a reference scheme of the trailing edge position of the splitter blade to effectively decrease predominate pressure pulsation amplitude.

Sign in / Sign up

Export Citation Format

Share Document