Sedimentation by gravity is the oldest water treatment. Inlet and outlet of rectangular sedimentation tank are often located in the middle of the tank. The present investigation studies the effect of changing inlet and outlet position of rectangular sedimentation tank on removal efficiency using Computational Fluid Dynamics method. Two different configurations are proposed and they have been tested with varying particles diameters and concentration. Numerical model ability to describe flow field behaviour inside the tank is confirmed by an experimentation data. Results show that inlet and outlet position influence the flow field and removal efficiency of sedimentation tanks, especially for the case of fine particles (50 and 120µm).

The clogging of emitters has been considered as one of the most troublesome problems inhibiting the extension of drip irrigation. This paper investigates the flow field of water and behaviour of suspended particles in the trapezoidal labyrinth-channel. Computational Fluid Dynamics methods has been executed on liquid-solid two-phase flow in labyrinth-channel emitters. RNG k-e turbulence model was used to evaluate four types of emitters that have the same characteristics and differ in the elbow width S. This study has shown that as the value of S increases, the maximum velocity in the labyrinth-channel decreases and the number of vortices increases. However, emitter with a high S value are more subtle to clogging. In addition, it was also observed that smaller diameter particles behave best when they pass through the channel and follow the streamline flow. As the particle diameters become larger, the particles tend to leave the mean stream and enter the vortex zones under the force of inertia. So, more suspended particles trapped in the vortex area , more the chances of emitter clogging increase. All of these furthermore confirm that vortex and low speed regions were the main causes leading to emitter clogging.

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