Experimental studies on the Reynolds stress in an open channel flow

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Experimental studies on the Reynolds stress were practised by analyzing the time series data in an open channel flow. Experiments were performed at the outdoor agricultural irrigation channel, that is, the Meiji irrigation channel in Aichi prefecture and the Makuwa and Kagami irrigation channel in Gifu prefecture. Instrumental system was composed of a small current meter of the propeller type, a data recorder, a frequency-voltage converter and a monitor recorder. The results obtained were as follows.1. It was found that the time constant of a small current meter was about 0.03-0.05 seconds for the usual flow and was well approximated by the cosine function in the direction. 2. The patterns of the auto-correlogram in the lower parts of the open channel flow were steeper than in the upper parts. The integral time scales were 0.04-0.01 seconds. 3. The shape of the energy spectral density gradually decreased with the high frequency and didn't have a any particular peak. 4. There was a negative correlation between the recognized u and w averaged patterns. 5. The conditional sampling method was carried out to analyze the Reynolds stress structure.