Understanding Schlieren and Shadowgraph Techniques — Lesson 2

This lesson covers the detailed discussion on Schlieren and Shadowgraph techniques, which are used in wind tunnel testing. It explains the concept of refractive index, density of the medium, and how these factors influence the deflection of light rays. The lesson also delves into the design, fabrication, and mounting arrangements of models used in these techniques. It further explains the importance of model design, the choice of material, and the considerations for mounting arrangements. The lesson uses illustrative examples of different models and their mounting arrangements to provide a practical understanding of these techniques.

Video Highlights

01:23 - Explanation of the radius of curvature of the light ray and its link with the refractive index.
06:47 - Explanation of the shadow graph effect and its dependence on the second derivative of the density.
09:46 - Explanation of the considerations involved in model design and fabrication, including material choice, machining processes, dimensions and tolerances, and model mounting arrangement.
20:16 - Discussion on different types of model mounting arrangements, including sting mounted models and strut mounted models.

Key Takeaways

- Schlieren and Shadowgraph techniques are used to study the change in density of a medium as it moves through the test section of a wind tunnel.
- The refractive index of the medium and the density of the medium play a crucial role in these techniques.
- The design, fabrication, and mounting arrangements of models are critical aspects of these techniques.
- The choice of material for the model, its dimensions, tolerances, and surface finish are important considerations in model design.
- Different mounting arrangements, such as sting mounted and strut mounted, are used based on the requirements of the experiment.