Development of a New Calibration Method for Laser Velocimetry toward Establishing Traceability in Flow Measurements

We developed a new calibration method for laser velocimetry for (cid:223) ow measurements to establish the traceability of measurement uncertainty and to reduce calibration uncertainty. In conventional methods, large radial uncertainty of a scattering object is dominant due to the difficulty of accessing the true calibration radius. Our new method successfully solves this difficulty by providing a reliable radial estimate at calibration. It employs a rotating disk and a precision linear stage and utilizes the linear relationship between the true radii and the resulting Doppler frequencies. Uncertainty analysis was performed based on Guide to the Expression of Uncertainty in Measurement (GUM). The traceability chain is established once the elemental traceabilities are obtained. We built prototype calibration setups and conducted three series of calibration experiments. The uncertainty was reduced to around 0.1%, which is suf (cid:222) ciently small compared to the general limit of ordinary laser velocimetry.