Investigation of the dependence of the Doppler frequency on the flow for a fixed arrangement as regards pipe diameter and Doppler angle
Due to the dependence of the Doppler frequency shift on the flow velocity and the proportionality between volume flow and average velocity in a fixed cross section, the Doppler effect can be used for flow measurement. The precondition is that the liquid shows a sufficient number of scatterers, in which the scattering angle is not equal to 90°. In the first part of the experiment, the Doppler frequency shift is determined for different flows of the fixed measurement arrangement, which are produced with the aid of the pump speeds. From the dependence found between flow and Doppler frequency shift there arises a calibration factor for a simple flow meter. In the second part of the experiment, different flows are produced with the pump, the respective Doppler frequency shift is measured and the volume flow is calculated for the respective pump setting with the aid of the calibration factor.
In the experiment, a linear correlation is found between Doppler frequency shift and volume flow. From the increase of the linear regression lines it is possible to derive a calibration factor, using which the volume flow can be calculated for any measured Doppler frequency shift.