Segment V7.5: Wind Tunnel Train Model

(Related to Textbook Section 7.9.2 - Flow Around Immersed Bodies)

To maintain exact similarity between model and prototype flows in a wind tunnel, the model and prototype Reynolds numbers must be equal. This is usually not possible to achieve. Fortunately, flow characteristics are often not strongly influenced by the Reynolds number over the range of interest.

The flow past a train with a cross wind is studied by observing the flow of smoke injected near a model in a wind tunnel. Although the model Reynolds number is less than that for the prototype, the complex flow characteristics observed for the model should also occur for the prototype. (Video courtesy of the National Research Council of Canada and the Institute for Aerospace Research.)