本文選題：血流動力學 + 數(shù)值模擬��； 參考：《鄭州大學》2017年碩士論文

【摘要】：據(jù)《中國心血管病防治現(xiàn)狀藍皮書·2015》報道,目前我國約有2.9億心血管病患者且呈現(xiàn)出逐年上升的趨勢。每一年就有約260萬人因心血管疾病而死亡,平均每12秒就有1人被心血管疾病奪去生命,其發(fā)病率和死亡率位居所有疾病的首位。對人類健康這一公共衛(wèi)生問題構(gòu)成嚴重威脅,亟待通過多方研究加以解決。動脈粥樣硬化(Atherosclerosis,AS)是一種常見的血管疾病,可能會引起腦卒中、冠心病、心肌梗死等嚴重并發(fā)癥。對于60歲以上的老年人,其發(fā)病率高達79.9%。如果同時伴有心腦血管疾病,患者5年內(nèi)的生存率只有59%,而對于“三高癥”患者,其生存率更低。由此可見,AS對于人類健康具有嚴重的潛在威脅。但是,AS的致病成因和發(fā)展機理較為復雜,尚未被完全認知掌握。探索AS的發(fā)病規(guī)律和具體原因,對于病情控制、風險評估以及臨床預后工作都具有十分重要的意義。大量研究表明,動脈粥樣硬化的發(fā)展受到生物、物理、化學等多方面刺激的影響。各方學者也依據(jù)相關(guān)病例及實驗結(jié)果,提出了各種學說試圖解釋AS的產(chǎn)生與發(fā)展機理。但這些學說均沒有系統(tǒng)的分析AS產(chǎn)生與發(fā)展過程中的力學機理。Caro在對尸體的解剖研究中發(fā)現(xiàn),AS主要發(fā)生于分岔、狹窄、彎曲等血流動力學易受擾動的部位,表現(xiàn)出非常明顯的無差異局部病灶性特征,從而證明血流動力學環(huán)境的改變對AS的形成和發(fā)展具有重要影響,但對于其具體作用方式和影響程度的了解還不深。本文的研究思路是采用逆向工程建模,通過數(shù)值仿真證明血管形貌會對管壁受力造成一定影響,導致局部壁面切應力較低。隨后再結(jié)合Caro低切應力學說,利用被動式動網(wǎng)格方法,將壁面切應力作為判據(jù),模擬AS的動態(tài)發(fā)展過程。本文的模擬計算工作是通過FLUENT計算流體動力學軟件完成的,其操作界面簡潔美觀,具有豐富的物理模型以及先進的數(shù)值算法,還具有配套的前后處理功能。在計算流體領(lǐng)域認可度較高,計算結(jié)果也較精確可靠。FLUENT還提供了二次開發(fā)的程序接口(UDF),方便用戶實現(xiàn)更多元化的模型求解功能。本文以血流動力學為切入點,考慮壁面低切應力對斑塊增生的促進作用以及流場邊界的變化對血液流動重分布的影響,實現(xiàn)血管壁邊界變化與血流動力學之間的相互耦合作用,這也正是此方法的技術(shù)難點。本文在考察主動式動網(wǎng)格和單元填充法后,發(fā)現(xiàn)其模擬效果和計算效率存在不足。為此,本文創(chuàng)新性的采用了二次開發(fā)的UDF(User Defined Function)動網(wǎng)格程序,實現(xiàn)在計算過程中提取血管壁面切應力并做出判斷,進而調(diào)控動網(wǎng)格節(jié)點的移動,模擬血管斑塊的增生過程。經(jīng)過對比,發(fā)現(xiàn)模擬結(jié)果與一些臨床血管造影的相似度較高,證明了本方法的可行性。
[Abstract]:According to Blue Book 2015, there are about 290 million patients with cardiovascular diseases in China. Every year, about 2.6 million people die from cardiovascular disease, and an average of one person is killed by cardiovascular disease every 12 seconds, the highest morbidity and mortality rate of all diseases. It poses a serious threat to the public health problem of human health, and needs to be solved in many ways. Atherosclerotic Atherosclerosis (ASA) is a common vascular disease, which may cause severe complications such as stroke, coronary heart disease, myocardial infarction and so on. For the elderly over 60 years old, its incidence is as high as 79. 9%. If accompanied by cardio-cerebrovascular disease, the 5-year survival rate is only 59, and for the "three high" patients, the survival rate is even lower. This shows that as has a serious potential threat to human health. However, the pathogenetic and developmental mechanism of as is complicated and has not been fully understood. It is of great significance for disease control, risk assessment and clinical prognosis to explore the pathogenesis and causes of as. Numerous studies have shown that the development of atherosclerosis is influenced by biological, physical and chemical stimuli. According to the relevant cases and experimental results, scholars have put forward various theories to explain the mechanism of as production and development. But none of these theories systematically analyzed the mechanical mechanism in the process of as production and development. Caro found in the autopsy of cadavers that as mainly occurred in bifurcation, stenosis, bending and other hemodynamic easily disturbed sites. It is proved that the change of hemodynamic environment has an important influence on the formation and development of as, but the specific mode of action and the degree of influence are not well understood. The research idea of this paper is to use reverse engineering modeling. The numerical simulation results show that the shape of blood vessel will have a certain effect on the wall force, resulting in a low shear stress on the local wall. Based on Caro's theory of low shear stress and passive dynamic grid method, wall shear stress is taken as criterion to simulate the dynamic development of as. The simulation and calculation work in this paper is accomplished by FLUENT computational fluid dynamics software. The operation interface is simple and beautiful, it has abundant physical models and advanced numerical algorithms, and it also has the function of pre-processing and pre-processing. In the field of computational fluid recognition is high, the calculation results are more accurate and reliable. Fluent also provides a secondary development of the program interface to facilitate users to achieve more diversified model solving functions. In this paper, we consider the effect of wall low shear stress on plaque proliferation and the effect of flow field boundary change on blood flow redistribution, so as to realize the interaction between vascular wall boundary change and hemodynamics. This is the technical difficulty of this method. After investigating the active dynamic mesh and element filling method, it is found that the simulation effect and computational efficiency are insufficient. In this paper, the second developed UDF(User Defined function dynamic grid program is used to extract the wall shear stress and make the judgment in the process of calculation, and then to regulate the moving of the dynamic grid node and simulate the plaque proliferation process. By comparison, it is found that the simulation results are similar to some clinical angiography, which proves the feasibility of this method.
【學位授予單位】：鄭州大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O39;R543.5

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