1996-02-01

Measurement of Wake Flow Fields, Including Reverse Flow, of Scale Vehicle Models Using a New 13-Hole Pitot Tube 960676

Among the various methods for measuring flow velocity vectors, multi-holed pitot tubes offer the advantages of facilitating pressure measurements, low cost and ease of use. On the negative side, the range of measurable flow angles is limited (e.g., to ± 40° with 5-hole tubes) and pitot tubes require time-consuming calibration before use.The authors have developed a new pitot tube with a spherical head and 13 holes arranged such that the pitot head shows a 5-hole pattern when viewed from different right angles. This hole arrangement is equivalent to having several multi-holed pitot tubes connected to one pitot head and expands the measurable range of flow angles substantially to ± 135°. In addition, a robot is used to achieve fully automatic calibration. These two improvements overcome the traditional drawbacks of multi-holed pitot tubes.The new 13-hole pitot tube was used to measure the wake flow fields, including reverse flow, of one-fifth scale vehicle models, and a comparison was made with experimental results obtained with a laser Doppler velocimeter (LDV). Measurements were made for two body styles. The new 13-hole pitot tube accurately captured the effects of differences in the vehicle shape on wake flow characteristics and the results correlated well with the LDV measurements, verifying the usefulness of the new device.

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