Viscoplastic oil's shear pressure calculation in a profiled pipeline

Pipeline start after shut-off can be connected with essential difficulties, especially in case of pumping non-Newtonian oils with complicated rheology. This is caused by the fact that during oil cooling (during shut-off) the starting pressure defined through shear stress can exceed allowable pressure values in the pipeline linear portion and/or allowable head at the oil transfer pumping station outlet. Normally, when evaluating oil temperature distribution over the pipeline axis, temperature variation in radial direction is neglected, and average oil temperature in each route point is used. At that consideration of this parameter shall increase the definition accuracy for the shear stress, starting pressure and time of pipeline safety shut-off. In this paper hydraulic statement and partial solution of the base system of equations in the form of a single-direction running wave are used for description of the initial stage of shutdown "hot" pipeline start. The problem statement incorporates consideration of temperature radial distribution, non-Newtonian oil rheology and its structuring transient kinetics. In comparison with a quasi-static shear pressure, which is identified with the minimum pressure of shutdown "hot" pipeline start, it is offered to consider the pressure in the initial section of the single-direction running wave.