Courtesy of Professor Ashim K. Datta, Dept. of Biological & Environmental Engineering, Cornell University

Students from the Department of Biological & Environmental Engineering of Cornell University in Ithaca, NY have been using FIDAP to simulate biomedical applications as part of a junior-senior level course, which has been taught for six years. During the course, students are taught about methods for solving systems of equations, including the finite element method used in FIDAP. They are trained to use FIDAP through the use of lectures and hands-on examples created by the faculty. Graduate teaching assistants with a knowledge of CFD have served a vital role over the years in teaching students how to use FIDAP and in providing debugging assistance on the individual projects. Towards the end of the course, the students review carefully chosen computational case studies from the literature in areas of bio-medical engineering and food processing.

The students then divide into teams to work on separate independent projects. They choose the biomedical examples that are to serve as project topics, and claim that this selection process is one of the most rewarding aspects of the course. The FIDAP simulations are performed on one of four departmental machines, supplied by a grant from Intel. In the past, super-computers at the Cornell Theory Center have also been used.

Numerous applications have been simulated by the students in the course during recent years. In one example ¹ (Figure 1), heat transfer to the cornea was examined during laser surgery procedures to correct either myopia (nearsightedness) or hyperopia (farsightedness). Operations using a single laser beam were compared to those using multiple laser beams. Through their simulations, the students optimized the laser beam shape and were able to obtain good images of the resulting temperature distributions. Knowledge of the temperature distribution could minimize the risk of failure during the actual operation. For example, when the laser is applied at multiple locations, the surgeon has better control of the heat flux delivered, and the procedure can be completed in a shorter time.

Figure 1: Temperature contours on the surface of the cornea following laser surgery with a single off-center laser (top) used to treat myopia, and multiple lasers (bottom) used to treat hyperopia

In another example ² (Figure 2), the temperature profile in the prostate gland was studied during cryogenic surgery to destroy a tumor. When applied to the prostate, cryosurgery is claimed to have fewer side effects than radiation or surgical removal. The benefits include less blood loss, fewer incisions, and faster recovery. During the procedure, the surrounding good tissue should be affected only slightly. The students found that using one probe to freeze the entire tumor is impractical.

Figure 2: Temperature vs. time in a prostate tumor cooled using one, three, and five probes

Because the tumor is not a good thermal conductor, a long period of time is needed to destroy it, and a significant amount of destruction occurs in the good tissue surrounding the site during this time. By using more probes, the tumor can be cooled more uniformly and with less damage to the surrounding good tissue. They also found that colder cryogens are best because they help to localize the freezing.

In a third example ³ (Figure 3), transient heat transfer during a tooth drilling procedure was studied. For three drill speeds, a thermal boundary condition was computed separately as a function of frictional effects. Cooling water over the tooth was used to modify this boundary condition. Using FIDAP, transient temperature prof iles in the tooth were computed as the hole was allowed to grow (through the use of the moving boundary model). The high-speed drill was found to be preferable, since it led to a quicker procedure, resulting in less heat transfer to the base of the tooth, with the likelihood of reducing pain sensation.

Figure 3: Temperature contours in a tooth after a high-speed drilling procedure

The course has been helpful in exposing students to simulation-based engineering. It shows how simulation can be used to speed up the design process. It gives them a depth of understanding about bio-medical processes that they cannot get without doing the detailed computations. Through the project work, the students learn about the sensitivity of CFD results to choices of input and solution parameters, such as boundary conditions or convergence level. While they do not leave the class claiming to be experts in CFD or numerical methods, the experience does play a significant role on their resumés as they begin searching for jobs after graduation.

Example References:

1. Chih Hao Chen, Diana Chen, Kim Foo Chow, JenYee Hui, and Darrick Lo

2. Brian Chow, Ingar Lau, Mike Neidrauer, and Jennifer Park

3. Julian Mintseris, Yuri Bunimovich, Vivek Mohan, and Becky Kim

FluentNEWS