DETECTION OF THE TURBULENT-NON-TURBULENT INTERFACE.
Interim technical rept. no. 1,
JOHNS HOPKINS UNIV BALTIMORE MD DEPT OF MECHANICS
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A new method was developed to form an intermittency function It ON for turbulent, OFF for non-turbulent flow using an analog circuit. The detection process is based on a signal proportional to a spatial derivative of velocity two adjustable detection parameters are used, namely, a threshold and a memory or hold-time. Methods are given for determining the optimum values of the detection parameters for a given flow using a two step procedure. First the detector cirucit performance is calibrated using a synthetic signal of known properties, and then measurements in the particular flow are related to the calibration tests to determine optimum settings. Detailed description is given of the detector circuit and of a circuit for generating a synthetic turbulence signal. Methods of determining detection errors and difficulties met in using the detection method in particular flows are discussed. An analytic model of the detection process is presented. Author
- Fluid Mechanics