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Numerical modeling of transient flows in load pipes with complex geometry

Ramoul S., Fourar A., Massouh F.

Journal of Applied Mathematics and Computational Mechanics

2017

Vol. 16, nr 4

67--78

Changes in the system flow of a fluid in a pipe often cause sudden pressure changes and give rise to so-called transient load flows. So, the study of the phenomenon of transient load flows aims to determine whether the pressure in the whole of a system is within the prescribed limits, following a perturbation of the flow. By defining the scope of a water hammer study, an examination is made of variations in velocity or flow and pressure resulting from poor operation of the hydraulic system, its normal operation and emergency operations. This paper introduces a numerical modeling of the phenomenon of transient flows in load pipes with variable geometries which presents a study of the average pressure and the average velocity of the transient flow in the pipe with quasi-steady term friction. The characteristic method is used to solve the governing equations of “Saint-Venant”. Thanks to the AFT Impulse industrial program, we have obtained very interesting and very practical numerical results to describe the phenomenon of transient flows in variable load pipes.

Unsteady loads evaluation for a wind turbine rotor

Chkir S., Dobrev I., Kuszla P., Massouh F.

Diagnostyka

2009

nr 4(52)

17-22

This paper presents a method for calculating the flow around a wind turbine rotor. The real flow is replaced by a free stream past a vortex model of the rotor. This model consists of lifting vortex lines which replace the blades and a trailing free vorticity. The vorticity shed from the blade is concentrated in two vortices issued from tip and root. To compute the unsteady forces exerted on the rotor, a free wake method is used. The evolution of the wake is obtained by tracking the markers representing the vortices issued from the blade tips and roots. To solve the wake governing equation and to obtain the marker positions, a time-marching method is applied and the solution is obtained by a second order predictor-corrector scheme. To validate the proposed method a comparison is made with experimental data obtained in the case of a model of wind turbine where the flow field immediately behind the rotor is measured by means of PIV. It is shown that the numerical simulation captures correctly the near wake development. The comparison shows satisfactory accuracy for the velocity field downstream of the rotor.