Comparison of Shallow and Deep Open Channel Flows
This video explores the setup and analysis of open channel flows using the Volume of Fluid (VOF) method. We compare two cases: a deep channel and a shallow channel, both using the same setup and boundary conditions.
Case 1: Deep Channel
- Depth of branching channels: 200 millimeters
- Depth of the larger channel: 400 millimeters
- The branching channels are not at the same level as the larger channel.
In this setup, the larger cross-sectional area allows for more water flow, as previously observed in data results.
Case 2: Shallow Channel
- Depth of branching channels: 40 millimeters
- The depth is one-fifth of the previous case.
- The channels are at the same level.
The focus here is on how the flow develops after merging and the differences compared to the deeper channel case.
Simulation Setup
- Method: Volume of Fluid (VOF)
- Phases: Air and Water
- Boundary Conditions:
- Inlet velocity: 1 meter per second
- Pressure outlet
- Time steps: 9,000
Observations
- Velocity contours and free surface changes were analyzed.
- In the shallow channel, the water depth is very low, leading to interesting surface wave patterns.
- Converging and diverging wave patterns were observed.
- The flow direction is mainly from the inlet to the outlet, with minimal impact on the branches.
- After the streams converge, the wave patterns differ significantly from the deeper channel case.
Wave Propagation
The wave propagation over the surface in the shallow channel resembles tidal bores seen when sea waves approach a beach. The interaction of waves is more pronounced in shallow water, highlighting the importance of water depth in flow regimes.
Conclusion
The depth of water is a crucial parameter in open channel flow regimes. The flow regime depends on the Froude number, which is a function of velocity and water depth. Different regimes, such as subcritical or supercritical flow, can be observed based on these parameters.
This video demonstrates the significant impact of water depth on flow interactions and surface wave propagation. By using Ozen Engineering, Inc. simulations, we can effectively analyze these effects.
Thank you for watching.
The comparison of shallow and deep open channel flows is shown in this video. In this second video, I want to look at the case where the open channel is set up using the volume of fluid method and compare it to the other case.
As you see, the depth of this therapy is 200 millimeters, so each branch has 200 millimeter depth. These two branches deliver water into the deeper, larger channel, which has a depth of 400 millimeters.
This is the case we already talked about, where the bottom of the branching channels is not at the same level as the bigger channel, resulting in a larger cross-sectional area. We are expecting much more water, as we already saw in the data results. In the second case, we have therapy soil.
Let's look at the cross-section here. The depth is only 10 millimeters. In this case, at the depth of the branch therapy soil, the percentage is only 1/5 of the previous case.
Another difference is that the debris, such as AI, boredom, and weeds, are at the same level, so they do not change the level of the bottom of the channels. They are talking about the lowest part of the images and members, just showing that over their area, the water level is probably low.
Let's go ahead and follow them to see the file and the much less depth into the channel and also into the water. We want to see what happens to the fellow after merging and what we can see differently compared to the previous case. Let's see what we can see from the fellow and the results.
This is what I showed you for the deeper water into the channels. As you see, we have different levels for the bottom of the channels. These two branches deliver water into the big channel. Let's just review what we got. As you can see, the water is mixing and starting to form.
The water is starting to mix together, and the fellow coming back is affected inside the branches. This is what we are seeing in this open channel when we have more depth of the water. Now, let's compare that with the shallow water in the open channel fellow.
I solved this model for the shallow water open channel fellow. The model setup is the same, using the volume of fluid method with two phases, air and water. The phase length of air in the shallow channel follows the filter setting.
I picked a shallow consuming water water and the phase interactions and also the boundary conditions here for the inlet. Again, I consider half of the fluid filled into the channel at the inlet and keep the velocity constant at one meter per second.
The outlets are open parts on the top, open to everything. I keep the boundary conditions the same as before. I already ran this for about 9,000 time steps. Let's compare them. I'm going to show you the simulations compared to see what's going on here.
This is the velocity contours added free surface for the shallow water open channel fellow. Remember what we had before. For this one, I just played again. You see that the water level is much lower than before. The waves converging and then diverging and then converging again.
The water level is much lower, and the shape of the surface wave is different. The main things I want to mention are the wave propagation over the surface and the wave propagation over the build-in. The wave propagation over the surface is different, and the waves are getting to the sides.
This is what we see in the shallow or less depth of the water. Let me show you another case. Here, we also have a little depth in the water, but I extended this larger part of the channel to see the disturbances after the merging of these two branches. This is the animation from that simulation.
As you can see, the waves are propagating over the surface. In this video, we will talk about erasing a big wave inside an open channel fellow.
We keep the fellow velocity constant at one meter per second at the inlets, just changing the geometry regarding to the length of the branching canals and the bigger channel. The main thing we change is the depth of the water. In one case, it is five times more water compared to the other case.
We see the huge difference between them regarding to the fellow reactions and interactions after merging together and also the way the surface waves initiate and propagate over the surface. Hopefully, this video can help you to know that we can simulate this effect in ANSYS Fluent.
Thank you very much.
