Abstract
The present research, in the flow velocity measurement by Laser Doppler Velocimeter (LDV), discusses a new data processing method that it is possible to obtain the flow velocity from the results using the frequency distribution of output voltages of the frequency tracker. In this case, the Doppler burst signals are produced with the only natural particles contained in fluid.
If we use the method, then the velocities of particles passing the middle point of a measuring control volume are obtained from the value at the point of maximum frequency in the frequency distribution.
Therefore, when the number of particles contained in fluid is poor or the flow velocity is low and also there is velocity gradient in the fluid flow, it is not necessary to intermix especially particles in fluid to do excellent the signal processing, and the method is successful and convenient.
Generally speaking, the measured flow velocity has a bias toward larger than practical flow velocity near the inner wall in a circular pipe in case of flow velocity measurement by LDV, but the bias is able to dissolve by the method.
The flow velocities obtained from the results of measurement at each measured points put very well on the flow velocity distribution curve, and the flow rate calculated from the flow velocity distribution agree well with the measurand of flow rate.
The adequacy of the new data processing method is described.
