Use of the Split-Film Sensor to Measure Turbulence in Water near a Wall

Because of its small size and unique design, the 0.15-mm diameter split-film sensor has many significant advantages over the conventional X-configuration hot-film sensor and the yaw-wire technique for measuring turbulence near a wall. Calibration of the split- film sensor indicates that the magnitude and yaw angle of the instantaneous velocity vector is dependent only on the sum and ratio of the sensor outputs, respectively. Results of limited measurements of the longitudinal and vertical turbulence intensities and Reynolds stress for hydraulically smooth, free surface flows are presented. Digital time series of the split-film outputs revealed the following information: (1) the split-film sensor longitudinal and vertical turbulence intensities and Reynolds stress compares favorably with previous studies; (2) the split-film sensor can be used as an instantaneous velocity vector transducer; (3) the split-film sensor is capable of making two-dimensional turbulence measurements in water to within five probe diameters of the wall. Calibration and experimental results indicate that the split-film sensor may be useful in improved spatial definition of the turbulent structure in wall shear flows