To measure velocity distribution in unsteady fluid flow is very difficult but very important to analysis and control of fluid devices and biological systems. As to this problem, we have proposed a model-based method by which transient flow velocity profiles in a pipe are computationally estimated.
In this paper, we apply this method to the measurement process of a hot film velocimeter and realize a Kalman filter which estimates unsteady laminar flow velocity profiles in a pipe using the velocimeter.
First, the process of measurement with the velocimeter is analyzed theoretically and experimentally and it is shown that the velocimeter can be substantially regarded as a point-measuring velocimeter which takes measurement of flow velocity at the center point of a hot film sensor without disturbing the flow around it, if the length of the sensor is short enough compared to the inside diameter of the pipe in which the sensor is inserted.
Based upon the above result, a Kalman filter to estimate the velocity profile is derived, implemented on a personal computer, and executed in real time, yielding successfull estimation of fluid velocity profiles on the CRT display of the computer.