The bidirectional velocity probe has been used in various flames to measure local velocity. The device is based on the pressure difference between a closed forward facing cavity and a closed rearward facing cavity. The probes have been noted to indicate a pressure difference greater than that which would be predicted based on Bernoulli's equation. Each device must be experimentally calibrated in a wind tunnel at similar Reynolds number to determine its “amplification factor.” This study uses PIV, flow visualization and CFD to examine the flow field around the probe, as well as an experimental study which compares various probe configurations for measurement of velocity by pressure differential. The conclusion is that the amplification factor is indeed greater than unity but use of the wind tunnel for calibration is questionable.

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