Introducing CFD to undergraduate students

M. Razi Nalim, Associate Professor of Mechanical Engineering, Indiana University – Purdue University, IN, USA S. Arif Khalid, in association with Indiana University – Purdue University, IN, USA

To meet the needs of graduates entering the work force, the school of Mechanical Engineering, at Purdue University Indianapolis, proposed an introductory undergraduate course in CFD. At the same time, one of the University’s senior engineering students expressed an interest in learning CFD independently, but needed only one or two credit hours to complete her graduation requirements. To meet the needs of this student as well as develop the underpinnings of a full undergraduate course, the University created a guided CFD introduction for this student using STAR-Design.

 

The aim was to develop a hands-on program of instruction to emphasize how CFD can be used to solve engineering problems and can require little or no CFD background to get started. In the spirit of problem-based learning (PBL), equations, terminology, and CFD concepts were to be covered during set-up and post-processing of actual cases, rather than via lectures beforehand. The University also aimed to enhance students’ understanding of how to use CFD as a virtual reality tool. While the CFD software needed to be simple to use, the student still needed to be able to access advanced capabilities and even to export the solution for post-processing with their own custom software.

 

The two problem cases were created using STAR-Design and were two-dimensional.

The first case, a semi-tractor trailer truck, exemplifies an external flow that is both familiar and has obvious aerodynamics shortcomings to address. In a typical introduction to CFD, a student might be given the geometry and mesh with which to carry out his or her first computation. Because STAR-Design has CAD modeling built in, a simplified truck configuration was requested and the student was allowed to create the geometry. The automatic mesh generation within STAR-Design is based on a solid model, and the student simply subtracted the truck from the surrounding block to produce the flow domain.

As an internal flow example, the flow around an axial compressor blade section was chosen. For this case the geometry model was provided to the student after entering the airfoil coordinates into STAR-Design and creating the domain boundaries. This case involved adjusting the mesh parameters to resolve the blade boundary layer and creating periodic boundary conditions. The latter was accomplished in pro-STAR by using a script that was provided. In addition to carrying out the computation, the student studied the relationship between pressure and velocity by examining several flow fields and plotting non-dimensional pressure rise against inlet axial velocity.

 

Using STAR-Design, CFD concepts can be introduced to an undergraduate student with very little software learning curve. The student learned how to obtain qualitative and quantitative results for relevant engineering situations. Meanwhile, this experience laid the groundwork to develop a full undergraduate course.

Figures

01: Velocity vectors for baseline 2D truck.
02: Velocity vectors for 2D truck after student's geometry modifications.
03: Velocity for 2D linear compressor cascade at low flow condition showing boundary layer separation.
04: Mesh for 2D linear compressor cascade with enlarged view near airfoil leading edge showing STAR-Design customization for boundary layer. Contours show velocity magnitude for high flow condition.
05: Graph - plotted pressure rise characteristic showing eventual decrease for low flows.