Sedimentation in Urban Sewer Conduits, ANSYS Fluent CFD Simulation Training

Description

Description

The problem simulates sand particle sedimentation in a water flow channel using ANSYS Fluent software.

The sedimentation phenomenon is one of the destructive phenomena in the quality of performance of any equipment. Sedimentation can occur when the base fluid contains excess soluble particles.

The discrete sand particle’s diameters are variable, including a minimum diameter of 0.00001 m, a maximum diameter of 0.0002 m, and an average diameter of 0.000131 m. The present model is designed in three dimensions using Design Modeler software.

The model consists of a computational area in the form of a horizontal channel with a square cross-section in which the flow of water and particles move horizontally inside.

On the lower surface of the canal, three rows of plates or diagonal barriers are designed that can help the sedimentation phenomenon.

We carry out the model’s meshing using ANSYS Meshing software, and the mesh type is structured. The element number is 14280.

Sedimentation Methodology

In the present simulation, the Eulerian-Lagrangian perspective on computational fluid dynamics (CFD) is used; So that the Eulerian multiphase model is coupled with the dense discrete phase model (DDPM).

A continuous phase is defined, related to water flow, and a discrete phase is described, related to sand particles. The material of sand is defined as stagnant particles with a density equal to 2650 kg/m3.

The water flows with a flow rate of 15 kg/s and enters the channel horizontally. Simultaneously, the flow of sand particles enters the channel discretely with a flow rate of 0.21 kg/s and a velocity of 0.083 m/s.

Sedimentation Conclusion

Water flows along with sand particles into a canal, and the channel has obstacles in its path, or there is a sudden change of direction within the channel; a sedimentation phenomenon occurs; Because in areas with obstacles and with a sudden change of direction, dissolved sand particles locally relative to the main water flow becomes stagnant and slows down.

At the end of the solution process, two-dimensional contours related to water pressure and velocity and three-dimensional contours related to water pressure and velocity, and a particle sequence based on the residence time and particle diameter are obtained.

For example, the particle sequence indicates that water-soluble particles accumulate in the front area of ​​the barrier after hitting the initial oblique barrier. Thus, the sedimentation phenomenon is possible.