Author : Anis Elaoud, Sayed Chehaibi and Mohamed Ben Amor

In agricultural land can be observed problems regarding water and soil. The problems of water flow can cause breaks in pipes, and the problems associated with soil because of the passage of vehicles and lead to compaction, engender changes in soil parameter directly affects the infiltration water and fruit yield regression plants. In this paper, we will study numerically the flow in pipes and soil compaction. So, a first part examines the phenomena of demurrage pumps; when starting a pump, the speed of the electric motor rises from zero up to the permanent regime speed. This change in regime influences the flow of the hydraulic installation and forced it to follow the starting dynamic law of the motor. Under the effect of the friction force, due to the fluid viscosity, the transient regime is dumped until reaching the normal operating conditions. In this work, we study this phenomenon and see the influence of the pump startup on the hydraulic behaviour of one dimensional flow throw a cylindrical pipe of linear elastic behaviour. The pipe is connected to constant level reservoir at the downstream end. The problem is governed by a two coupled linear hyperbolic partial differential equations which are the equations of continuity and motion. The mathematical model is solved by the method of characteristics where at the upstream end, that is, at the pump station, the boundary condition is given by the differential equation for speed change of the pump motor. A theoretical relationship is introduced to express the motor torque in terms of the time. At the downstream end the discharging reservoir is assumed to be at a constant level. The computed head and discharge time curves, caused by the starting of the pump, are plotted at some cross sections of the pipe. The results show that the evolution of the hydraulic variables is well influenced by the applied motor torque. In a second part of the numerical study of soil compaction is developed.

Keywords: Compaction soil, method of characteristics, pipe, pump start-up, transient flow.

Article published in International Journal of  Advance Industrial  Engineering, Vol.1,No.1 (March- 2013)