The thermal transient anemometer

Applications that require the measurement of the spatially averaged velocity over a given area segment can be addressed by the thermal transient anemometer (TTA). The operating principle can be characterized as follows: (i) elevate the temperature of the multi-X patterned sensor—that appropriately samples the area of interest—to an initial overheat condition, (ii) allow the sensor to cool by the heat transfer of the passing fluid (plus end conduction effects), (iii) execute a calibration such that the exponential decay of the sensor resistance can be characterized by the time constant, τ, and (iv) infer the spatially averaged velocity U—or the spatially averaged density–velocity product ρU—from the relationship Note that A'', B'', n are defined by the calibration data. A description of the enabling electronics, demonstration measurements in a calibration air stream and the post-processing strategy to account for ambient temperature changes between calibration and test data are presented in order to characterize this instrument.