Transverse Dispersion in Oscillatory Channel Flow

An analysis of published data on dye dispersion in homogeneous estuaries shows that the dimensionless transverse dispersion coefficient is large compared with results in steady flow in straight channels. The hypothesis is made that transverse currents of three kinds are responsible for the large coefficients. The results of laboratory tests with oscillatory flow in meandering channels are described. Point injections of dye and subsequent measurements of the dye cloud are made. These results support the hypothesis that the transverse currents cause the large transverse dispersion coefficients. The results suggest that the spiral secondary currents associated with the channel meanders are the principal reason for the large coefficients.