June 24, 2007
June 24, 2007
June 27, 2007
12.195.1 - 12.195.15
Alternative Methods for Producing Wind Tunnel Models for Student Projects in Fluid Mechanics
Abstract Project-based approaches to engineering education make it desirable for students to create functional wind tunnel models for testing of original designs in fluid mechanics courses. This paper compares several rapid-prototyping (RP) methods with conventional mold/cast techniques for fabrication of fluid-dynamic models on the basis of cost, production time, ease-of-use, and accessibility of equipment and materials. RP technologies considered include stereolithography (SLA), selective laser sintering (SLS), fused-deposition modeling (FDM), 3-D printing, and CNC machining. These approaches start from an original design in digital format, while conventional methods, such as casting with silicone-rubber or alginate molds require at least a rough physical prototype. Coating and finishing processes for RP models are also discussed.
Background and Introduction The Mechanical Engineering Department at the University of Texas at Austin has been engaged for 6 years in a comprehensive program to implement project-based methods throughout the undergraduate curriculum . One element of this program includes wind-tunnel testing in parallel with the introductory course in fluid mechanics. The undergraduate fluid mechanics lab houses two wind tunnels, with 12"x12" and 24"x24" test sections respectively. Currently, students use the wind tunnels only for classical experiments using off-the-shelf models such as a cylinder in a cross-flow and airfoils, and for flow visualization demonstrations. The objects being tested are simple shapes and offer limited opportunity for creative experimentation. We wish to enhance this experience by offering our students the opportunity to design and test original aerodynamic models, such as automobile body shapes. This has motivated an investigation of alternative methods for rapidly producing wind tunnel models of original designs. Two fundamentally different approaches are considered: (1) molding/casting of models starting from a rough physical prototype and (2) creation of functional physical models from a digital image.
Molding/casting techniques are capable of producing models of all sizes and geometric tolerances. These approaches can utilize a variety of different materials for both mold-making and casting, including hot melts, latex, silicone rubbers, polysulfide rubbers, polyurethane, alginate, plastic resins, epoxies, wax, foam, clay, and water based plaster or concrete. The multistep process can be lengthy and requires some skill in forming of both a reusable mold and the cast model.
Rapid prototyping (RP) refers to a process in which physical objects are fabricated directly from CAD files. This category of prototyping techniques includes processes such as stereolithography (SLA), selective laser sintering (SLS), fused deposition modeling (FDM), 3-dimensional printing, and CNC machining. Each of these processes produces durable, long lasting models which can be enhanced by a variety of secondary surface finishes. Both the equipment and the
Zissman, E., & Schmidt, P. (2007, June), Alternative Methods For Producing Wind Tunnel Models For Student Projects In Fluid Mechanics Paper presented at 2007 Annual Conference & Exposition, Honolulu, Hawaii. https://peer.asee.org/3060
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