Pressure transmission in yield stress fluids - An experimental analysis

The current work presents an experimental investigation of the pressurization of a yield stress fluid contained in a closed pipeline under isothermal conditions. The tests were performed in a laboratory-scale flow loop placed inside a thermally controlled chamber. Sensors located along the pipeline measured fluid pressure and temperature. Differently from Newtonian fluids, experiments conducted with a viscoplastic fluid showed that the pressure imposed at one end of a closed pipeline was not fully transmitted to the other end, supporting prior mathematical model results. The results also revealed that the final pressure distribution was dependent not only on the fluid yield stress but also on the shear history the fluid underwent during pressurization and on the ratio between the pressure wave inertia and viscous dissipation. A comparison of the fluid yield stress obtained from rheometric measurements with the shear stress at the pipeline wall showed that they were of the same order of magnitude and that the higher the pressure wave inertia-viscous dissipation ratio the higher was the discrepancy between them.