臺灣博碩士論文加值系統

近年於心室輔助器發展中，心瓣的作動對流體的運動帶來相當顯著的擾動，並於1980年，空化現象已被發現於機械心瓣表面生成，空泡的出線將導致血液細胞的破壞、以及血栓栓塞症。目前相關的研究假設心瓣作動為已知，然後模擬血液於心瓣附近之流場，並有相關實驗結果顯示空化現象在心瓣關閉瞬間產生，因此我們關注在心瓣關閉速度對流體的影響，局部流場的速度因心瓣的關閉而增加。本論文對機械心瓣的數值模擬，採用黏性流與動態網格的技術來解決流場中移動邊界的問題，並運用「完全空化模型」分析流道於心瓣作動下可能產生的物理現象，尤其瓣膜於關閉期間，流體受到瓣膜尾緣與管壁面的擠壓，造成此時部分流場區域之流體質點速度增加，導致空化現象。另外，我們假設液體相為不可壓縮，且所有物理參數與環境溫度無關。我們發現空化現象發生的時間段非常的短，因此運用數值方法進行模擬分析時必頇採用足夠小的時間步距，方能解析出空化的現象。

Cavitation was first related to valves of a mechanical heart in the 1980s after a series of valve fractures of a particular valve were observed. In the present study, the cavitating flow phenomena are computationally studied with the assumption that the valve motion is known. We focus on the effects of closing velocity of the valve on the flow development since it is known that cavitation often occurs at the moments when the valve is closing due to the fact that at these moments, the local flow often accelerates and a local high velocity distribution results. In the present series of computations, a viscous flow model is incorporated with a dynamic mesh strategy to cope with the movement of the valve. Furthermore, the simulation of cavitation will be modeled by the “full cavitation model,” which takes considerations of the first-order effect of the formation and transport of vapor bubbles, the turbulent fluctuations of pressure and velocity, and the magnitude of non-condensable gases. In addition, we also assume that the liquid phase is incompressible, and all parameters and physical variables are independent of temperature.

摘要
Abstract
目錄
圖目錄
表目錄
第一章緒論
1-1 前言
1-2 人工瓣膜簡介
1-3 文獻回顧
1-3-1 流場剪應力
1-3-2 紊流與渦流
1-3-3 空化現象
1-4 研究動機
1-5 論文架構
第二章物理問題與理論基礎
2-1 物理問題探討
2-2 假設條件
2-3 統御方程式
2-3-1 邊界與初始條件
2-3-2 紊流模型
2-3-3 完全空化模型
第三章數值模型與驗證
3-1 數值方法
3-2 網格建置
3-3 數值計算驗證
3-3-1 時間步距的影響
3-3-2 速度流線與分佈
3-3-3 壓力分佈
第四章結果與討論
4-1 空化之前的速度流線與分佈
4-1-1 速度流線與分佈
4-1-2 瓣膜表面之剪應力分佈
4-1-3 流場之應變率
4-2 空化之前的壓力分佈
4-3 空化流場分析
4-3-1 流場體積分率與壓力擾動
4-3-2 微小噴流之速度流線
第五章結論與建議
參考文獻

[1] Hufnagel CA, Harvey WP,” The surgical correction of aortic regurgitation-Preliminary report,” Bull Georgetown Uni-Med Center, Vol.6, pp.60-61, 1953

[2] Lakshmi P. Dasi, Helene A. Simon, Philippe Sucosky, Ajit P. Yoganathan,” Fluid Mechanics of Artificial Heart Valves,” Clinical and Experimental Pharmacology and Physiology, Vol.36, P.P.225-237, 2009.

[3] Klepetko W, Moritz A, Mlczoch J,” Schurawitzki H, Domanig E, Wolner E, Leaflet fracture in Edward-Duromedics bileaflet valves,” J Thorac Cardiovasc Surg, Vol.97, P.P.90-94, 1989.

[4] Kalyani N., C.V. M., And G.S. Bhuvaneshwar,” Developments in mechanical heart valve prosthesis,” 2003.

[5] Ajit Yoginathan,” Cardiac valve prosthesis,” Handbook of biomedical engineering (NewYork: CRC Press) Vol.123, P.P.1847-1870, 1995.

[6] Svennevig JL, Abdelnoor M, Nitter-Hauge S,” Twenty-five-year experience with the Medtronic-Hall valve prosthesis in the aortic position: a follow-up cohort study of 816 consecutive patients,” Circulation, Vol.116, P.P.1795-1800, 2007.

[7] Steven Deutsch, John M. Tarbell, Keefe B. Manning, Gerson Rosenberg, and Arnold A. Fontaine,” Experimental Fluid Mechanics of Pulsatile Artificial Blood Pumps,” The Annual Review of Fluid Mechanics, Vol.38, P.P.65-86, 2006.

[8] Hubbell JA, McIntire LV,” Visualization and analysis of mural thrombogenesis on collagen, polyurethane and nylon,” Biomaterials Vol.7, P.P.354-363, 1986.

[9] Medvitz RB, Kreider JW, Manning KB, Fontaine AA, Deutsch S, Paterson EG,” Development and validation of a computational fluid dynamics methodology for simulation of pulsatile left ventricular assist devices,” ASAIO J, Vol.53, P.P.122-131, 2007.

[10] Idit Avrahami, Moshe Rosenfeld, Shmuel Einav,” The Hemodynamics of the Berlin Pulsatile VAD and the Role of its MHV Configuration,” Annals of Biomedical Engineering, Vol.34, P.P.1373-1388, 2006.

[11] 羅啟文, 機械心瓣穴蝕成因探討, 淡江大學水資源及環境工程學系博士論文, 2008.

[12] H. Lee, Eiki A., Eisuke Tatsumi, Yoshiyuki Taenaka,” Characteristics of cavitation intensity in a mechanical heart valve using a pulsatile device: synchronized analysis between visual images and pressure signals,” Journal of Artificial Organs, Vol.11, P.P.60-66, 2008.

[13] H. Lee, Yoshiyuki Taenaka,” Characteristics of Mechanical Heart Valve Cavitation in a Pneumatic Ventricular Assist Device,” Journal of Artificial Organs, Vol.32, p.p.453-460, 2008.

[14] Yong G. Lai, Krishnan B. Chandran, Jack Lemmon,” A Numerical Simulation of Mechanical Heart Valve Closure Fluid Dynamics,” Journal Of Biomechanics, Vol.35, P.P.881-892, 2002

[15] Wei Yin, Yared Alemu, Klaus Affeld, Jolyon Jesty, and Danny Bluestein,” Flow-Induced Platelet Activation in Bileaflet and Monoleaflet Mechanical Heart Valves,” Ann. Biomedical Engineering, Vol.32, pp.1058-1066, 2004.

[16] Fung, Y.C.,” Biomechanics:Mechanical properties of living tissues,” Springer Verlag, 1993.

[17] Lee Waite, Jerry Fine,” Applied Biofluid Mechanics.”

[18] Karlis Adamsons JR., Salha S. Daniel, Gillian Gandy, and L. Stanley James,” Influence of temperature on blood pH of the human adult and newborn,” Journal of Applied Physiology, Vol.19, pp.897-900, 1964.

[19] Wilcox D.,” Turbulence Modeling for CFD,” DCW Inc., 1994.

[20] Ashok Singhal, Mahesh Athavale, H. Li, Yu Jiang,” Mathematical Basis and Validation of The Full Cavitation Model,” Journal of Fluids Engineering, Vol.124, pp.617-624, 2002.
[21] Edward A., Ernst, and Pablo Perez-Zamora, B.S.,” Water Vapor Pressure in Blood and Tissues,” 1969

[22] Issa, R.I.,” Solution of the implicitly discretized fluid flow equation by operator splitting,” Jornal Comput. Phys., Vol62, pp.40-65, 1986.

[23] Patankar, S.V.,” Numerical Heat Transfer and Fluid Flow,” Hemisphere Publishing Corp., Washington, D.C., USA, 1980.