Weissenberg number
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The Weissenberg number is a dimensionless number used in the study of viscoelastic flows. It is similar to the Deborah number. The dimensionless number is the ratio of a specific process time and the relaxation time of the fluid. For instance if a simple shear test is done the Weissenberg number, often abbreveated with We or Wi, is defined as the shearrate times a specific length devided by the relaxation time (<math>Wi = \frac{\dot{\gamma} L}{\lambda}</math>) Since this number is obtained from scaling the evolution of the stress, it contains choices for the shear or elongation rate and the lenghtscale. Therefore the exact definition of all non dimensional numbers should be given as well as the number itself.de:Weissenberg-Zahl