Static pressure distribution along the main current channel of drip irrigation pipe

Abstract

Based on the conservation law of mass and momentum, a mathematical model of variable mass flow was established. Combined with the pressure test data, the expression of static pressure distribution along the main current channel of the drip irrigation pipe was obtained. The results show that the static pressure variation along the main current channel of the drip irrigation pipe depends on the frictional resistance and the momentum exchange. The frictional resistance term diminishes the static pressure, and the momentum exchange term makes the static pressure tend to increase. The pressure test shows that the axial flow velocity distribution index m of the drip irrigation pipe is independent of the dripper characteristic parameters and linear with the drip number N . Based on the theoretical analysis and experimental data regression, the expression of the momentum exchange coefficient k is obtained, and the equation is solved by the Blasius resistance formula. The calculated value of the static pressure agrees well with the measured value. In the static pressure distribution model, the influence factors of static pressure are attributed to the length-diameter ratio of the drip irrigation pipe and the Reynolds number Re0 of the inlet, which is convenient for optimizing the structural design and determining the optimal operating conditions. This paper can provide a reference for the hydraulic calculation of drip irrigation pipe and the hydrodynamics study of porous pipes.