Experimental investigation of meandering jets in shallow reservoirs

Meandering flows in rectangular shallow reservoirs were experimentally investi-
gated. The characteristic frequency, the longitudinal wave length and the mean lateral exten-
sion of the meandering jet were extracted from the first paired modes, obtained by a proper
orthogonal decomposition of the surface velocity field measured by large scale PIV. The
depth-normalised characteristic lengths and the Strouhal number were then compared to the
main dimensionless numbers characterizing the experiments: Froude number, friction num-
ber and reservoir shape factor. The normalised wave length and mean lateral extension of the
meandering jet are neither correlated with the Froude number nor with the reservoir shape
factor; but a clear relationship is found with the friction number. Similarly, the Strouhal num-
ber is found proportional to a negative power of the friction number. In contrast, the Froude
number and the reservoir shape factor enable to predict the occurrence of a meandering flow
pattern: meandering jets occur for Froude number greater than 0.21 and for a shape factor
smaller than 6.2.