Managing Particle Transport In Open Channel Flow is a critical task for hydraulic engineers. Rivers, canals, and drainage systems carry solid particles like sand, gravel, and sediment. These particles interact with the water and the channel walls. If the particles hit the walls too hard, they cause erosion and damage the structure. Predicting this movement is difficult because the water surface also moves. Traditional experiments are expensive and take a long time. Therefore, engineers use Particle Transport In Open Channel Flow CFD simulation to solve these problems on a computer.

In this report, we perform a CFD Analysis of Particle Transport In Open Channel Flow. We use ANSYS Fluent to model the water and the particles together. We use the Open Channel Flow fluent simulation module to handle the free surface of the water. We also use the Discrete Phase Model (DPM) to track individual particles. This simulation helps us predict where sediment will settle and if it will erode the channel bed. For more details on complex flows, please explore our Multiphase tutorials: https://cfdland.com/product-category/module/multiphase-cfd-simulation/

• Reference [1]: Sinha, Nityanand, and Roozbeh Golshan. “Material transport under a wave train in interaction with constant wind: A eulerian RANS approach combined with a Lagrangian particle dispersion model.” Fluids2 (2018): 40.
• Reference [2]: Golshan, Roozbeh, et al. “Oil droplet transport under non-breaking waves: An eulerian rans approach combined with a lagrangian particle dispersion model.” Journal of Marine Science and Engineering1 (2018): 7.

Figure 1: Details of multi-phase wave simulation. [1]

Simulation Process: DPM Tracking and Erosion Setup in Fluent

For this Particle Transport In Open Channel Flow CFD Simulation, we created a realistic 2D channel model. We used a high-quality structured grid with 100,050 cells. We made the mesh very fine near the bottom and the top surface to get the best accuracy. We activated the Volume of Fluid (VOF) model in ANSYS Fluent. This model is necessary to track the free surface where the water meets the air. We also enabled the special Open Channel Flow fluent simulation module. This tool automatically calculates the correct pressure from gravity and keeps the water level stable. This setup ensures that the water flow physics are exactly like a real river or canal.

To simulate the sediment, we used the Discrete Phase Model (DPM). This is a Lagrangian tracking method. We injected inert particles into the water flow. We enabled unsteady particle tracking, which means we calculate the particle position at every moment in time. We also turned on “two-way coupling.” This means the water pushes the particles, and the particles also push back on the water. We included important physical forces like the virtual mass force and pressure gradient force to be very accurate. Finally, we activated the DPM Erosion ANSYS Fluent model. This calculates how much material is removed from the floor when a particle hits it. This is the key step for predicting wear and tear on the structure.

Post-processing: Particle Dynamics, Settlement, and Erosion Analysis

This section analyzes the engineering data to check the safety of the channel. We look deep into the contours and numbers to see if the design is good for the manufacturer. First, we look at the Water Volume Fraction in Figure 2. The contour shows a clear separation. The bottom is Water and the top is Air. The interface is a sharp, flat line. This proves that the Open Channel Flow CFD simulation is stable. The flow is “subcritical,” meaning the water moves calmly without big splashing waves. This stable surface is crucial because it carries the particles downstream smoothly. Next, we analyze the DPM Concentration in Figure 1. We see cyan and light blue dots floating in the water. The concentration is about 1.33e-04 kg/m³. This is a small number, which means the flow is a dilute suspension. The particles do not clump together. For a hydraulic engineer, the distribution is the key finding. We see more particles near the bottom (bed) than at the top. This confirms that gravity settling is happening. The particles are heavier than water, so they sink. However, the turbulence in the Open Channel Flow keeps some of them floating. This balance determines how far sediment travels before blocking the channel.

Figure 2: Particle tracks colored by Residence Time, visualizing the trajectory and settling behavior of particles as they travel downstream in the open channel.

Figure 3: Volume fraction contours showing the water-air interface and free surface position in the Open Channel Flow CFD simulation using the VOF model in ANSYS Fluent.

Figure 4: DPM concentration distribution showing particle locations and mass concentration throughout the open channel in the Particle Transport CFD Simulation using ANSYS Fluent with two-way DPM coupling.

We also study the Particle Tracks in Figure 3. The colors show time. Blue dots are new particles at the inlet (9.94 seconds). Red dots are old particles downstream (10.00 seconds). This color change proves the Particle Transport is working correctly from left to right. We clearly see particles touching the bottom red line. This indicates particle-wall interaction. These are the points where erosion could happen. Finally, we analyze the calculated Erosion Rate. The simulation gives an area-weighted average erosion of 5.616e-16 kg/m².

• Engineering Insight: This value is extremely close to zero. It is negligible.
• Benefit to Manufacturer: This result is very positive. It proves that under these specific flow conditions, the particles do not damage the channel bed. The impact energy is too low to remove material. This means the designer does not need to add expensive concrete lining or protection layers. The Particle Transport In Open Channel Flow CFD analysis confirms that the hydraulic structure will have a long lifespan with minimal maintenance.