Publications Repository - Gdańsk University of Technology

This study is devoted to the derivation of approximate equations governing acoustic pulses in flows with yieldstress, including some time-dependent flows with a slow dependence on time of yield stress and apparent viscosity. Themodeling of yield stress and apparent viscosity in the vicinity of a zero deformation rate allows us to consider a thixotropicfluid as a Bingham plastic with coefficients that are dependent on time. The ordering scheme results in equationsthat are valid in leading order with respect to a number of small parameters. The unusual property of the domains of awaveform with positive and negative shear stress to propagate with different velocities is discovered. The illustration concernsthe initially bipolar acoustic pulse, which becomes positive after some time. The proposed theory predicts broadeningof a pulse due to the yield stress, starting at some time after the beginning of its evolution.

Authors

• prof. dr hab. Anna Perelomova link open in new tab