Traditionally, experimental and analytical methods have been used to demonstrate simplified transport phenomena problems even they have limitations to apply. However, significant progress in computer performances and state-of-the-art computational fluid dynamics (CFD) modeling and simulations to understand the more realistic transport phenomena in realistic biological systems have been made in the past decades as a virtual prototyping tool.
Biomedical engineering (BME) is a relatively new, exciting, interdisciplinary and future-oriented area. An understanding of the transport phenomena in realistic biological systems is essential for successful outcomes from the undergraduate education. BME curriculum at Mercer University has two required courses (Basic Transport Phenomena and Dynamics of Biological Fluids) and one technical elective course (Advanced Biofluids) related to transport phenomena in biological systems. All courses require group course project reports with presentations.
The purposes of the virtual prototyping projects are to improve the students’ understanding of transport phenomena topics, to provide experiences of virtual prototyping with more realistic modeling and simulations. Most of the students appreciated having the virtual prototyping with computational modeling and simulations in the courses and led to better understanding of the course materials related to transport phenomena in biological systems.
Following are the list of the current undergraduate research projects:
Reflux of the Greater Saphenous Vein contributes to “varicose veins” and affects many people, including the elderly and women. Endovenous laser and radiofrequency treatments have been used to treat varicose veins by eliminating the source of venous reflux, using thermal damage of the vein wall. Thermal damage causes an occlusion based on the shrinking of collagen fibers in the vein wall.
However, the optimal thermal power and retraction rate required to successfully eliminate the reflux while causing minimum damage to the perivenous tissue is still being investigated. Computational modeling of endovenous laser treatment is developed to understand appropriate retraction rates and thermal power for the laser probe. Using ANSYS CFX (ANSYS Academic version), the heat transfer through the vein wall and perivenous tissue based on the power and retraction rates of the continuous laser was computed. Four different conditions were tested, in order to find the optimum operating conditions needed to attain a vein wall temperature of 85ºC. The conclusions are that the retraction rate is more significant, and a 15 W laser retracted at 1.5 mm/s achieves the desired temperature at the vein wall.
The appearance of an aneurysm, a localized dilatation of a blood vessel, may result in the onset of local weakening or the rupture of the blood vessel. Theorizing that abdominal aortic aneurysm rupture coincides with characteristic local wall shear stresses and pressure, patient specific computational hemodynamics modeling and simulations were performed for an abdominal aortic arterial system before (i.e., pre-op) and after (i.e., post-op) the endovascular graft surgery. Patient specific three-dimensional geometries generated in SimpleWare software were edited and meshed with ANSYS ICEM CFD release 11.0 (Academic version) . Simulations with ANSYS-CFX for the inlet Reynolds number of 702 demonstrated several characteristic pressure and wall shear stress features. In the pre-op geometry, elevated pressure observed on the inferior and posterior aspect of the sub-mesenteric bulge of the abdominal aorta suggests possible locations of rupture. Examining local calcifications three-dimensionally, low wall shear stress and higher pressure appeared upon the CT-imaged calcifications, possibly indicating a site of rupture, a site of weakening on the arterial wall, or a site of thrombus formation. The characteristic pressure and wall shear profile of the pre-op geometry starkly contrasted the post-op geometry, in which the pressure profile and wall shear stress were more uniform in the sub-mesenteric regions.
Image processing using Simplware
Simpleware geometry meshed using ANSYS ICEM CFD
ANSYS CFX Streamline plot for abdominal aortic aneurysm
Results of undergraduate research using ANSYS-CFX were published in following journal and conference papers:
- Chappell, A., Vines, R.S., Fountas, K., Machinis, T., Robinson, J.S., Jr., and Hyun, S., (2006), Computational modeling and simulations of cerebral hypothermia using selective brain cooling mechanism, 2006 Summer Bioengineering Conference, Amelia Island, FL.
- McConnell, K., Solomon, B., Somani, I., and Hyun, S., (2006), Interspecies comparison of particle transport and deposition in lung airways of human and rat, 2006 Summer Bioengineering Conference, Amelia Island, FL.
- McConnell, K. and Hyun, S., (2005) Nano-particle transport and deposition in human tracheobronchial bifurcating airways, 2005 Summer Bioengineering Conference, Vail Cascade Resort & Spa, Vail, CO.
- Basciano, C.A., Land, A.D., Pham, E.H., and Hyun, S., (2005) Computational fluid particle dynamics modeling and simulation in tracheobronchial airways, 2005 Summer Bioengineering Conference, Vail Cascade Resort & Spa, Vail, CO.
- Hyun, S., (2005) Virtual prototyping presented in undergraduate transport phenomena courses of biomedical engineering curriculum, Biomedical Engineering Society 2005 Annual Meeting ( Baltimore, MD).
- Womack, J., McConnell, K., Bower, C., Carson, T., and Hyun, S., (2005) Heat transfer in breast with enclosed cancer during hyperthermia using microwaves, Biomedical Engineering Society 2005 Annual Meeting (Baltimore, MD).
- Blackburn, T., Hamel, S., and Hyun, S., (2005) Effects of increases blood viscosity on hemodynamic parameters in the carotid artery bifurcation, Biomedical Engineering Society 2005 Annual Meeting ( Baltimore, MD).
- Basciano, C.A., Land, A.D., Pham, E.H., and Hyun, S., (2005) Computational fluid particle dynamics modeling and simulation in human lung airways, 2005 American Society of Engineering Education, South-Eastern Section Conference, Chattanooga, TN, (1 st Award for Undergraduate Research ).
- Hamel, S., Blackburn, T., Garner, C., and Hyun, S., (2005) Computational particle hemodynamics simulations in carotid artery Bifurcation, 2005 American Society of Engineering Education, South-Eastern Section Conference , Chattanooga, TN, (2 nd Award for Undergraduate Research ).
- Cartwright, K.K., Jackson, S.R., and Hyun, S., (2005) Impact of atherosclerotic occlusion position on hemodynamic parameters in the coronary artery, 2005 American Society of Engineering Education, South-Eastern Section Conference, Chattanooga, TN, (Outstanding Poster Award ).
- Jackson , S. and Hyun, S., (2004) Computational thermal modeling for effective thawing of cryopreserved pluripotent epiblastic-like stem cells, Biomedical Medical Engineering Society 2004 Annual Meeting, Philadelphia, PA..
- S. Hyun, (2004) Computational Hemodynamics with Hematocrit-dependent Blood Viscosity Modeling, Health Science Research Conference ( Macon, GA).
- S. Hyun, A. A. Mims, S. S. Neelakantan, and C. Kleinstreuer, (2003) A hematocrit-dependent blood viscosity model, BMES 2003 Annual Fall Meeting ( Nashville, TN).
