Coanda Effect for Incompressible Flows in Moving Domains

运动域中不可压缩流动的康达效应

• 批准号: 1109189
• 负责人: Suncica Canic
• 金额: $ 26.36万
• 依托单位: University of Houston
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-15 至 2015-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1109189&HistoricalAwards=false
• 关键词: Coanda; Effect; Incompressible; Flows; Moving

Coanda effect is a phenomenon that has been described in scientific literature as a tendency of a fluid jet to be attracted to a nearby surface. Recently, Coanda effect has been used in cardiology to describe the wall-hugging jets in mitral regurgitation: regurgitant blood flow through a leaky mitral valve sometimes hugs the wall of the left atrium which makes it difficult to assess the severity of mitral regurgitation using classical color Doppler imaging techniques. Despite the large cardiovascular and biomedical literature reporting on the Coanda effect in echocardiography, a connection with the fluid dynamics studies that could help identify and understand the main features of the corresponding flow conditions is lacking. This project makes this connection and explores the fluid dynamics properties leading to the Coanda effect in a novel environment: moving geometries and time periodic flow conditions, which will include those encountered in patients with mitral regurgitation. The corresponding fluid dynamics problem is associated with the behavior of flow through an orifice at Reynolds numbers below turbulence. Coanda effect corresponds to the breaking of symmetry (a bifurcation) in the solution of the Navier-Stokes equations at certain Reynolds numbers and for certain orifice shapes. While flows through orifices have been extensively studied (numerically and experimentally) in the context of fixed orifices and fixed fluid domains, there have been no results that shed light on the flow conditions leading to Coanda effect in moving orifices under time-periodic pressure loads. This project addresses this problem by combining sophisticated computational methodology and analytical techniques associated with fluid-structure interaction (FSI) between a viscous, incompressible fluid, and an elastic structure. The methodology is based on a monolithic, semi-implicit algorithm to solve an Arbitrary Lagrangian-Eulerian (ALE) formulation of the underlying FSI problem, and on the corresponding energy estimates. Experimental validation of the mathematical models and computer simulations will be performed with the medical collaborators at the DeBakey Heart and Vascular Center in Houston.Although over 50% of the US population has some degree of heart valve dysfunction, most cases do not require any medical treatment. In the cases when valve regurgitation is severe, failure of treatment can lead to arrhythmias, congestive heart failure and death. Doppler echocardiography is routinely used by physicians to diagnose and assess the severity of mitral valve regurgitation. The accurate assessment of valve regurgitation using echocardiography is, however, an ongoing challenge. In particular, regurgitant blood flow through a leaky mitral valve sometimes hugs the wall of the left atrium (known as the Coanda effect), which makes it difficult to see and measure the regurgitant volume. By using sophisticated mathematics, scientific computing, and experimental validation, the interdisciplinary team consisting of mathematicians and echocardiographic specialists, is investigating the blood flow conditions, and the shape of the regurgitant valves, that lead to the Coanda effect. This is a novel fluid-dynamics problem that has not been studied before due to the difficulties in resolving the interaction between blood flow and the moving regurgitant valve. By using a recently developed state-of-the-art computational algorithm that is capable of resolving this problem, and by developing novel mathematical techniques that will capture the bifurcation in the flow associated with Coanda effect, the results of this project will shed light on the complex intracardiac flow conditions associated with this phenomenon, and lead the way in designing novel protocols in echocardiographic assessment of mitral regurgitation. Students participate in all the aspects of this research. They are being trained in computer simulations, mathematical modeling, and in experimental validation of the mathematical models.

coanda效应是一种现象，在科学文献中被描述为流体射流被吸引到附近表面的趋势。 最近，Coanda效应已用于心脏病学中，以描述二尖瓣反流中的壁式射流：流经渗漏的二尖瓣流体流动有时会拥抱左心房的壁，从而难以评估使用经典的颜色多普勒成像技术来评估二尖瓣反流的严重程度。 尽管关于超声心动图中Coanda效应的心血管和生物医学文献大量报告，但与流体动力学研究的联系可能有助于识别和理解相应的流动条件的主要特征。该项目使这种联系并探讨了在新的环境中导致Coanda效应的流体动力学特性：移动几何和时间周期性流动条件，其中包括二尖瓣反流的患者遇到的那些。相应的流体动力学问题与湍流低于雷诺的流动孔的流动行为有关。 coanda效应对应于某些雷诺数和某些孔口形状的Navier-Stokes方程解中对称性（分叉）的破坏。尽管在固定的孔口和固定的流体结构域的背景下，已经对孔口的流量进行了广泛的研究（数值和实验性），但没有结果可以阐明在时间周期压力载荷下移动孔口的流动条件。该项目通过结合与粘性，不可压缩的流体和弹性结构之间与流体结构相互作用（FSI）相关的复杂计算方法和分析技术来解决此问题。该方法基于一种单层的半平算算法，以解决基本FSI问题的任意拉格朗日 - 欧拉（ALE）配方，以及相应的能量估计。将对休斯顿Debakey心脏和血管中心的医疗合作者进行数学模型和计算机模拟的实验验证。尽管超过50％的美国人群具有一定程度的心脏瓣膜功能障碍，但大多数情况不需要任何医疗治疗。在瓣膜反流严重的情况下，治疗失败会导致心律不齐，充血性心力衰竭和死亡。多普勒超声心动图通常被医生通常用于诊断和评估二尖瓣反流的严重程度。然而，使用超声心动图对阀门反流的准确评估是一个持续的挑战。特别是，经过泄漏的二尖瓣流动的流动流动有时会拥抱左心房的壁（称为Coanda效应），这使得难以看见并测量反流体积。通过使用复杂的数学，科学计算和实验验证，由数学家和超声心动图专家组成的跨学科团队正在研究引起coanda效应的血流条件以及反流瓣的形状。这是一个新型的液体动力学问题，由于难以解决血流与移动反流瓣之间的相互作用的困难。 By using a recently developed state-of-the-art computational algorithm that is capable of resolving this problem, and by developing novel mathematical techniques that will capture the bifurcation in the flow associated with Coanda effect, the results of this project will shed light on the complex intracardiac flow conditions associated with this phenomenon, and lead the way in designing novel protocols in echocardiographic assessment of mitral regurgitation.学生参与了这项研究的所有方面。他们正在接受计算机模拟，数学建模以及数学模型实验验证的培训。