Comparison of two flow measurement devices for use in fire experiments

Bi-directional probes are utilized throughout fire science to measure fire-induced flows due to their ability to measure flow which changes direction, and to withstand hostile environments. However, they are not available commercially and researchers must take it upon themselves to make and manufacture them. S-type pitot probes (S-probes) work on the same principle as bi-directional probes, measuring the differential pressure between two openings, thereby offering the same benefits. However, S-probes also feature reliable manufacturing and calibration standards. In this study, the performance of bi-directional and S-probes is characterized against pitot-static probes in two scenarios. First, measurements of a steady, smooth flow in a well-characterized wind tunnel are examined. Second, the probes are used to measure the velocity profile across a turbulent jet from a blower fan. In both scenarios, the S-probe performed comparable to or better than the bi-directional probe in terms of accuracy. It is found that S-probes have similar performance to bi-directional probes in well conditioned flows. In the turbulent jet flow measurements, S-probe measurements are within 2% of pitot-static measurements in the core region of the jet, while bi-directional probes are within 6%.