scholarly journals Kinematic, Dynamic, and Energy Characteristics of Diastolic Flow in the Left Ventricle

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Seyed Saeid Khalafvand ◽  
Tin-Kan Hung ◽  
Eddie Yin-Kwee Ng ◽  
Liang Zhong
Keyword(s):  
Mitral Valve ◽  
Left Ventricle ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Temporal Variations ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Energy Characteristics ◽  
Flow Acceleration ◽  
Acceleration And Deceleration

Blood flow characteristics in the normal left ventricle are studied by using the magnetic resonance imaging, the Navier-Stokes equations, and the work-energy equation. Vortices produced during the mitral valve opening and closing are modeled in a two-dimensional analysis and correlated with temporal variations of the Reynolds number and pressure drop. Low shear stress and net pressures on the mitral valve are obtained for flow acceleration and deceleration. Bernoulli energy flux delivered to blood from ventricular dilation is practically balanced by the energy influx and the rate change of kinetic energy in the ventricle. The rates of work done by shear and energy dissipation are small. The dynamic and energy characteristics of the 2D results are comparable to those of a 3D model.

Effect of Flow Characteristics on the Operation of a Solenoid Switching Control Valve

2015 ◽  
Vol 799-800 ◽  
pp. 1113-1116
Author(s):  
Cheol Heui Han ◽  
Sang Jin Ma ◽  
Myung Jin Chung
Keyword(s):  
Numerical Simulation ◽  
Compressible Flow ◽  
High Speed ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Control Valve ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Flow Acceleration ◽  
Choked Flow

Effect of the compressible flow characteristics inside a high-speed electromagnetic valve on the operation of the valve is investigated using a numerical simulation. The numerical simulation solves Navier-Stokes equations and heat transfer equations by coupling, and the compressible flow phenomena inside the valves are studied focusing on the shock structures. . Fluid-structure interaction is considered using freely moving grid deformations. The flow patterns of subsonic acceleration, choked flow, supersonic expansion, and a strong curved shock were observed inside the valve during on/off operations. The subsonic flow acceleration affected the operation characteristics of the valve.

scholarly journals FLUID DYNAMIC CHARACTERISTICS OF SYSTOLIC BLOOD FLOW OF THE LEFT VENTRICLE

2015 ◽  
Vol 15 (03) ◽  
pp. 1550047 ◽  
Author(s):  
TIN-KAN HUNG ◽  
SEYED SAEID KHALAFVAND ◽  
EDDIE YIN-KWEE NG
Keyword(s):  
Left Ventricle ◽  
Energy Flux ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Navier Stokes ◽  
Shear Stresses ◽  
Ventricular Contraction ◽  
Navier Stokes Equations ◽  
Flow Acceleration ◽  
Ventricular Motion

Ejection of blood from the left ventricle to the aorta is studied using two-dimensional Navier–Stokes equations, the work-energy equation and the magnetic resonance imaging of a normal ventricular motion. Vortex shedding in the sinuses of Valsalva is dominated by the aortic jet, flow acceleration and valve motion. Momentums produced by ventricular contraction are in concert with vortices in the ventricle for blood ejection. Shear stresses and net pressures on the aortic valve are calculated during valve opening and closing. The rate of work done by shear and the energy dissipation in the ventricle are small. The Bernoulli energy flux delivered to blood from ventricular contraction is practically balanced by energy flux at the aortic root and the rate change of kinetic energy in the ventricle.

A finite element method for the Navier-Stokes equations in moving domain with application to hemodynamics of the left ventricle

2017 ◽  
Vol 32 (4) ◽  
Author(s):  
Alexander Danilov ◽  
Alexander Lozovskiy ◽  
Maxim Olshanskii ◽  
Yuri Vassilevski
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Left Ventricle ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Computed Tomography Images ◽  
Time Dependent Domain ◽  
Element Method

AbstractThe paper introduces a finite element method for the Navier-Stokes equations of incompressible viscous fluid in a time-dependent domain. The method is based on a quasi-Lagrangian formulation of the problem and handling the geometry in a time-explicit way. We prove that numerical solution satisfies a discrete analogue of the fundamental energy estimate. This stability estimate does not require a CFL time-step restriction. The method is further applied to simulation of a flow in a model of the left ventricle of a human heart, where the ventricle wall dynamics is reconstructed from a sequence of contrast enhanced Computed Tomography images.

Numerical simulation of the stalled flow within a vaned centrifugal pump

2004 ◽  
Vol 218 (4) ◽  
pp. 425-435 ◽  
Author(s):  
K M Guleren ◽  
A Pinarbasi
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Pump ◽  
High Speed ◽  
Stokes Equations ◽  
Reverse Flow ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Navier Stokes Equations ◽  
Low Pass

The main goal of the present work is to analyse the numerical simulation of a centrifugal pump by solving Navier-Stokes equations, coupled with the ‘standard k-∊’ turbulence model. The pump consists of an impeller having five curved blades with nine diffuser vanes. The shaft rotates at 890r/min. Flow characteristics are assumed to be stalled in the appropriate region of flowrate levels of 1.31-2.861/s. Numerical analysis techniques are performed on a commercial FLUENT package program assuming steady, incompressible flow conditions with decreasing flowrate. Under stall conditions the flow in the diffuser passage alternates between outward jetting when the low-pass-filtered pressure is high to a reverse flow when the filtered pressure is low. Being below design conditions, there is a consistent high-speed leakage flow in the gap between the impeller and the diffuser from the exit side of the diffuser to the beginning of the volute. Separation of this leakage flow from the diffuser vane causes the onset of stall. As the flowrate decreases both the magnitude of the leakage within the vaneless part of the pump and reverse flow within a stalled diffuser passage increase. As this occurs, the stall-cell size extends from one to two diffuser passages. Comparisons are made with experimental data and show good agreement.

Effect of a Time-Dependent Stenosis on Flow Through a Tube

1968 ◽  
Vol 90 (2) ◽  
pp. 248-254 ◽  
Author(s):  
D. F. Young
Keyword(s):  
Stokes Equations ◽  
Flow Characteristics ◽  
Time Dependent ◽  
Arterial System ◽  
Navier Stokes ◽  
Axially Symmetric ◽  
Navier Stokes Equations ◽  
Flow Through ◽  
Dependent Growth ◽  
Abnormal Tissue

A common occurrence in the arterial system is the narrowing of arteries due to the development of atherosclerotic plaques or other types of abnormal tissue development. As these growths project into the lumen of the artery, the flow is disturbed and there develops a potential coupling between the growth and the blood flow through the artery. A discussion of the various possible consequences of this interaction is given. It is noted that very small growths leading to mild stenotic obstructions, although not altering the gross flow characteristics significantly, may be important in triggering biological mechanisms such as intimal cell proliferation or changes in vessel caliber. An analysis of the effect of an axially symmetric, time-dependent growth into the lumen of a tube of constant cross section through which a Newtonian fluid is steadily flowing is presented. This analysis is based on a simplified model in which the convective acceleration terms in the Navier-Stokes equations are neglected. Effect of growth on pressure distribution and wall shearing stress is given and possible biological implications are discussed.

Numerical Study of Wave Slamming on an Oscillating Flap

2014 ◽  
Author(s):  
Yanji Wei ◽  
Alan Henry ◽  
Olivier Kimmoun ◽  
Frederic Dias
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Ocean Waves ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Numerical Studies ◽  
Wave Slamming ◽  
Volume Method

Bottom hinged Oscillating Wave Surge Converters (OWSCs) are efficient devices for extracting power from ocean waves. There is limited knowledge about wave slamming on such devices. This paper deals with numerical studies of wave slamming on an oscillating flap to investigate the mechanism of slamming events. In our model, the Navier–Stokes equations are discretized using the Finite Volume method with the Volume of Fluid (VOF) approach for interface capturing. Waves are generated by a flap-type wave maker in the numerical wave tank, and the dynamic mesh method is applied to model the motion of the oscillating flap. Basic mesh and time step refinement studies are performed. The flow characteristics in a slamming event are analysed based on numerical results. Various simulations with different flap densities, water depths and wave amplitudes are performed for a better understanding of the slamming.

scholarly journals Effect of Impeller Parameters on the Flow inside the Centrifugal Blower using CFD

2020 ◽  
Vol 8 (6) ◽  
pp. 3977-3980
Keyword(s):  
Numerical Analysis ◽  
Stokes Equations ◽  
Control Volume ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Computational Domain ◽  
Centrifugal Blower ◽  
Impeller Blade ◽  
Navier Stokes Equations

A numerical analysis is carried out to understand the flow characteristics for different impeller configurations of a single stage centrifugal blower. The volute design is based on constant velocity method. Four different impeller configurations are selected for the analysis. Impeller blade geometry is created with point by point method. Numerical simulation is carried out by CFD software GAMBIT 2.4.6 and FLUENT 6.3.26. GAMBIT work includes geometry definition and grid generation of computational domain. This process includes selection of grid types, grid refinements and defining correct boundary conditions. Processing work is carried out in FLUENT. The viscous Navier-Stokes equations are solved with control volume approach and the k-ε turbulence model. In this three dimensional numerical analysis is carried out with steady flow approach. The rotor and stator interaction is solved by mixing plane approach. Results of simulation are presented in terms of flow parameters, at impeller outlet and various angular positions inside the volute. Also, the contours of flow properties are presented at the outlet plane of fluid domain. Results suggest that for the same configurations of centrifugal blower, as we change geometrical parameter of impeller the flow inside the blower get affected.

scholarly journals Prediction of By-Pass Transition by Means of a Turbulence Weighting Factor: Part I — Theory and Validation

1999 ◽  
Author(s):  
J. Steelant ◽  
E. Dick
Keyword(s):  
Transport Equation ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Weighting Factor ◽  
Navier Stokes ◽  
Freestream Turbulence ◽  
Transitional Layer ◽  
Turbulent Spots ◽  
Navier Stokes Equations ◽  
Intermittency Factor

The classical intermittency factor γ for quantifying transition is redefined and extended to enable the modelling of by-pass transition. Therefore, a new parameter, the turbulence weighting factor τ, is introduced to cover both the physics of freestream turbulence diffusion and of turbulent spots. A transport equation is presented for the τ-factor including convective, diffusive, production and sink terms. In combination with the conditioned Navier-Stokes equations, this leads to improvements in the calculation of flow characteristics in both the transitional layer and the freestream.

Numerical Study on the Flow Characteristics of the Francis Turbine With Various Blade Profiles

2013 ◽  
Author(s):  
J.-H. Jeon ◽  
S.-S. Byeon ◽  
Y.-J. Kim
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Francis Turbine ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Ansys Cfx ◽  
Commercial Code ◽  
Sst Turbulence Model

The Francis turbine is a kind of reaction turbines, which means that the potential energy of water converted to rotational kinetic energy. In this study, the flow characteristics have been investigated numerically in a Francis turbine on the 15 MW hydropower generation with various blade profiles (NACA 65 and NACA 16 series) and discharge angles (14°, 15°, 17°, and 18°), using the commercial code, ANSYS CFX. The k-ω SST turbulence model is employed in the Reynolds averaged Navier-Stokes equations. The computing domain includes the spiral casing, guide vanes, and draft tube, which are discretized with a full three-dimensional mesh system of unstructured tetrahedral shapes. The results showed that the change of blade profiles and discharge angles significantly influenced the performance of the Francis turbine.

The oblique ascent of a viscous vortex pair toward a free surface

1992 ◽  
Vol 236 ◽  
pp. 461-476 ◽  
Author(s):  
Hans J. Lugt ◽  
Samuel Ohring
Keyword(s):  
Free Surface ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Vortex Pair ◽  
Nonlinear Boundary Conditions ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Directional Change ◽  
Secondary Vortices

The problem of a vortex pair, rising obliquely at an angle of 45° toward a deformable free surface in a viscous, incompressible fluid, is solved with the aid of the Navier—Stokes equations. The full nonlinear boundary conditions at the free surface are applied. The oblique interaction of the vortex pair with the free surface results in a number of novel features that have not been observed for the special case of a vertical rise, reported earlier. These features include the directional change of trajectories near the free surface and the occurrence of waves driven by the vortex pair. Moreover, surface tension can completely change the flow characteristics such as the direction of the trajectories and the generation of secondary vortices. Numerical solutions are presented for selected Reynolds, Froude, and Weber numbers.

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