1. © Copyright 2014 COMSOL. Any of the images, text, and equations here may be copied and modified for your own internal use. All trademarks are the property of their respective owners. See www.comsol.com/trademarks.www.comsol.com/trademarks Pipe Erosion due to Contaminant Particles

2. Background and Motivation Erosion often occurs in pipe bends, tube constrictions, and other structures that alter the flow field. In this model, particle tracing and wall erosion boundary conditions are used to estimate the mass loss due to erosion on a pipe elbow.

3. Geometry The model symmetry is used to reduce the computational cost of the model. The diameter of the pipe is 0.2m. The 90 degree bend has a radius of 0.5m.

4. Physics Interfaces - Turbulent Flow A RANS turbulence model is used due to the flow high Reynolds number. Because of the curvature in the geometry, the k- w turbulence is the most appropriate turbulence model.

5. Boundary Conditions – Flow Symmetry Inlet Outlet

6. Boundary Conditions – Inlet A one-seventh power law velocity profile is defined at the inlet. The turbulent length scale at the inlet is set to 7% of the inlet diameter.

7. Physics Interfaces – Particle Tracing The particle tracing interface is used to model the contaminant particles. The wall erosion features compute the mass loss due to particles hitting the wall.

8. Physics Interfaces – Particle Tracing Release type is set to static to model a constant mass flow rate of particles.

9. Physics Interfaces – Particle Tracing Three different erosion models are specified: –Finnie –DNV –E/CRC

10. Boundary Conditions – Inlet The particle mass flow rate at the inlet is set to 0.6kg/h. The initial velocity of the particles is set to the velocity of the fluid.

11. Boundary Conditions – Symmetry A bounce wall boundary condition is used as a symmetry boundary condition for the particle tracing physics.

12. Meshing A structured mesh reduces the computational cost of the model. The boundary layer mesh ensures that the turbulent wall boundary layer is well resolved.

13. Study Settings Since the particles do not affect the flow field, this model first solves the flow field in study 1 (stationary), before computing the erosion process in study 2 (time dependent). Study 2 uses a direct solver with absolute and relative tolerances set to 1e- 3.

14. Results Velocity (m/s)Pressure (Pa)

15. Particle positions at t=0.5s

16. Erosion rate The full geometry is built in postprocessing using a mirror dataset feature. This graph shows the erosion rate, in kg/(m^2*s), for the Finnie model.