On-Line Measurements and Analysis of High Turbulent and Reverse Flow Fields

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

KEY WORDS:

Turbulence, Hot wire anemometry, Signal analysis, On-line Data acquisition, Reynolds stresses.