A Numerical Investigation of Blood Damage in the Hinge Area of BMHV

2010 ◽  
Author(s):  
Jingshu Wu ◽  
Anna Fallon ◽  
Helene Simon ◽  
Cyrus Aidun ◽  
Ajit Yoganathan
Keyword(s):  
Heart Valves ◽  
Cardiac Cycle ◽  
Three Dimensional ◽  
Flow Fields ◽  
High Fidelity ◽  
Thromboembolic Complications ◽  
Hemodynamic Effects ◽  
Flow Properties ◽  
Blood Damage ◽  
Blood Elements

Bileaflet mechanical heart valves (BMHVs) have been widely used to replace native valves. Unfortunately, the design of bileaflet MHVs produces flow fields that may cause damage to blood elements, especially at the hinge area. The objectives of this study are to analyze the flow properties around the hinge area and through the valve, to further understand the cause of blood damage and provide improved designs to reduce the adverse hemodynamic effects of valves that cause platelet activation and damage blood elements. An important part of this improvement is to understand the hemodynamic effects produced by different valve designs, and how the surrounding flow fields affect thromboembolic formation. The hemodynamics of the valve flow is characterized by complex spatial and temporal three-dimensional structures that arise from the pulsatility of the flow, the complexity of the geometry and the flow-dependent motion of the valve leaflets. High fidelity simulations of the valve flow fields throughout the cardiac cycle is required to improve and refine existing valve designs so as to ultimately develop bileaflet MHVs with minimal thromboembolic complications.

Prediction of Flow Properties on Turbine Vane Airfoil Surface From 3D Geometry With Convolutional Neural Network

2019 ◽  
Author(s):  
Yuan Jin ◽  
Shan Li ◽  
Olivier Jung
Keyword(s):  
Neural Network ◽  
Surrogate Model ◽  
Design Space ◽  
Flow Fields ◽  
High Fidelity ◽  
Flow Properties ◽  
Cfd Simulations ◽  
Airfoil Surface ◽  
3D Geometry ◽  
Turbine Vane

Abstract Nowadays, Computational Fluid Dynamics (CFD) simulations play an increasingly important role for turbine airfoil design. This high-fidelity approach is capable to provide accurate information of flow fields. Meanwhile, the calculation accuracy is always gained at the expense of numerical cost. This gap limits opportunities for design space exploration. To address this problem, surrogate models (also known as metamodels) are introduced to approximate high-fidelity CFD models. However, traditional surrogate models, such as Kriging or Radial Basis Function, construct response surface on a design space with limited dimensions. This prevents users from predicting the flow fields directly from the geometry and performing interactive design of airfoil. In the present work, we propose a Convolutional Neural Network (CNN) based surrogate model to predict flow properties on turbine vane airfoil surface from 3D airfoil profile defined by point cloud. The proposed CNN architecture adopts a symmetric expanding path that is similar to the so-called U-Net. The geometries in the training and testing dataset are generated via varying the parameters defined by the Free-Form Deformation approach. The corresponding flow fields are obtained through high-fidelity CFD simulations performed in a finite volume context. Furthermore, a gaussian process based Bayesian optimization technique is utilized to tune automatically the hyperparameters of the network. In this work, we trained the CNN based surrogate model with static pressure and temperature on the mean section of turbine vane airfoil surface. The trained model is able to predict in a reliable and efficient way the corresponding property directly from the 3D geometry, which allows engineers to agilely adjust their airfoil design.

A Mathematical Model for Shear-Induced Platelet Activation in Response to Time Dependent Shear Stress Histories

2012 ◽  
Author(s):  
João S. Soares ◽  
Jawaad Sheriff ◽  
Danny Bluestein
Keyword(s):  
Platelet Activation ◽  
Heart Valves ◽  
Drug Regimen ◽  
Ventricular Assist Devices ◽  
Prosthetic Heart Valves ◽  
Thromboembolic Complications ◽  
Ventricular Assist ◽  
Blood Damage ◽  
Anticoagulant Drug ◽  
Cardiovascular Implants

The advent of blood recirculating devices and cardiovascular implants (e.g. ventricular assist devices and prosthetic heart valves) has motivated research efforts towards a better understanding of blood damage, hemolysis, and chronic platelet activation that these devices induce. Because of the latter, patients with these classes of implants still develop thromboembolic complications that expose them to a greater risk of cardioembolic stroke and mandate life-long anticoagulant drug regimen with its inherent risks.

Real gas flow fields about three dimensional configurations

1983 ◽  
Author(s):  
A. BALAKRISHNAN ◽  
C. LOMBARD ◽  
W.C. DAVY
Keyword(s):  
Gas Flow ◽  
Three Dimensional ◽  
Flow Fields ◽  
Real Gas

Automatic Three-Dimensional Optimisation of a Modern Tandem Compressor Vane

2014 ◽  
Author(s):  
R. C. Schlaps ◽  
S. Shahpar ◽  
V. Gümmer
Keyword(s):  
Pressure Ratio ◽  
Three Dimensional ◽  
Trust Region ◽  
Automatic Generation ◽  
Navier Stokes ◽  
Design Parameters ◽  
High Fidelity ◽  
Stall Margin ◽  
Design Choice ◽  
Multipoint Approximation

In order to increase the performance of a modern gas turbine, compressors are required to provide higher pressure ratio and avoid incurring higher losses. The tandem aerofoil has the potential to achieve a higher blade loading in combination with lower losses compared to single vanes. The main reason for this is due to the fact that a new boundary layer is generated on the second blade surface and the turning can be achieved with smaller separation occurring. The lift split between the two vanes with respect to the overall turning is an important design choice. In this paper an automated three-dimensional optimisation of a highly loaded compressor stator is presented. For optimisation a novel methodology based on the Multipoint Approximation Method (MAM) is used. MAM makes use of an automatic design of experiments, response surface modelling and a trust region to represent the design space. The CFD solutions are obtained with the high-fidelity 3D Navier-Stokes solver HYDRA. In order to increase the stage performance the 3D shape of the tandem vane is modified changing both the front and rear aerofoils. Moreover the relative location of the two aerofoils is controlled modifying the axial and tangential relative positions. It is shown that the novel optimisation methodology is able to cope with a large number of design parameters and produce designs which performs better than its single vane counterpart in terms of efficiency and numerical stall margin. One of the key challenges in producing an automatic optimisation process has been the automatic generation of high-fidelity computational meshes. The multi block-structured, high-fidelity meshing tool PADRAM is enhanced to cope with the tandem blade topologies. The wakes of each aerofoil is properly resolved and the interaction and the mixing of the front aerofoil wake and the second tandem vane are adequately resolved.

scholarly journals Modelling Polycrystalline Materials: An Overview of Three-Dimensional Grain-Scale Mechanical Models

2013 ◽  
Vol 05 (01) ◽  
pp. 1350002 ◽  
Author(s):  
I. Benedetti ◽  
F. Barbe
Keyword(s):  
Three Dimensional ◽  
Constitutive Modelling ◽  
Polycrystalline Materials ◽  
High Fidelity ◽  
Computational Capability ◽  
Mechanical Models ◽  
Three Dimensional Models ◽  
The Individual ◽  
Individual Grains ◽  
Micro Structures

A survey of recent contributions on three-dimensional grain-scale mechanical modelling of polycrystalline materials is given in this work. The analysis of material micro-structures requires the generation of reliable micro-morphologies and affordable computational meshes as well as the description of the mechanical behavior of the elementary constituents and their interactions. The polycrystalline microstructure is characterized by the topology, morphology and crystallographic orientations of the individual grains and by the grain interfaces and microstructural defects, within the bulk grains and at the inter-granular interfaces. Their analysis has been until recently restricted to two-dimensional cases, due to high computational requirements. In the last decade, however, the wider affordability of increased computational capability has promoted the development of fully three-dimensional models. In this work, different aspects involved in the grain-scale analysis of polycrystalline materials are considered. Different techniques for generating artificial micro-structures, ranging from highly idealized to experimentally based high-fidelity representations, are briefly reviewed. Structured and unstructured meshes are discussed. The main strategies for constitutive modelling of individual bulk grains and inter-granular interfaces are introduced. Some attention has also been devoted to three-dimensional multiscale approaches and some established and emerging applications have been discussed.

scholarly journals Statistics of highly heterogeneous flow fields confined to three-dimensional random porous media

2016 ◽  
Vol 93 (1) ◽  
Author(s):  
C. Jin ◽  
P. A. Langston ◽  
G. E. Pavlovskaya ◽  
M. R. Hall ◽  
S. P. Rigby
Keyword(s):  
Porous Media ◽  
Three Dimensional ◽  
Flow Fields ◽  
Heterogeneous Flow ◽  
Random Porous Media
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