ON-LINE MEASUREMENTS AND ANALYSIS OF HIGH TURBULENT AND REVERSE FLOW FIELDS

ABSTRACT
As with most recent turbulence experimental researches, data are collected, stored and
analyzed by digital computers. In this investigation, a wind tunnel measurement and
analysis of flow field with high turbulence and recirculation is carried out. A sophisticated
electronic/computer system is designed and implemented to permit data acquisition and
on-line analysis either for in-situ calibration of the X-hot-wires or for measurement of high
turbulence quantities and re-circulating flows. The technique is called Flying Hot-Wire
probe system which is entirely controlled and operated by computer interfacing. The
present paper involves description the interfacing of the measuring instruments with a
PDP11-23 minicomputer. Also, it presents the digitizing technique to capture high
turbulence and reverse flow. The hardware and the software which permit precise
positioning of the measurement points in the flow field and the transfer of the flow field
signals are presented. The procedure allows evaluation of the velocity components and
the Reynolds stresses in axial and traverse directions. Validation test in still air and in
uniform flow are conducted. The results are compared with those obtained from stationary
hot-wires system. The in-situ calibration of the wires is successfully carried out with
resulted normalized standard deviation of 0.7. The measurements error in the mean flow
velocity is within 0.01% to 0.2%. The longitudinal turbulence intensity measured by the
present technique is 1% compared with 0.8% measured by stationary hot wire. The results
obtained are demonstrating that this is a successful technique for high turbulence intensity
measurement