Side channel spillway by ANSYS CFX?

I want to model a part of a river in Ansys-Fluent. The discharge and the water surface level at downstream (or outlet) are known. The model is multi-phase VOF (water+air) and Open Channel option is also selected. My question is what boundary conditions best suit for this model.

Is it proper to use "mass-flow-inlet" for inlet and "pressure-outlet" for outlet? Are any special considerations required? I am relatively new to this kind of problems (CFD, I mean).

I am simulating an open channel flow in a 2d rectangular channel using ANSYS FLUENT. I intend to incorporate a tail-gate at the end of the channel so that , I can create and control a hydraulic jump by raising and lower the tail gate as and when required.

If I am not wrong then , simulating such a tail gate in ansys fluent needs an UDF that can change the boundary condition ,at the channel end, from wall to pressure outlet.

This would also mean that the UDF should include this fact too that the tail gate will rise or lower over a definite time and definite rate(velocity) i.e the boundary condition would change from wall to pressure outlet not instantly rather over a definite time( no. of time steps).

Of course the wall(tail-gate) material is specified as steel.

I need to run the calculations (for simulating the flow) for few time steps with a particular position of the tail gate and then stop the calculation. Make changes in the UDF to specify the next position of the tail gate and re-run the calculation and so on.

Hello everyone

I am working in a 2D channel where I know the inlet Pressure as a function of cosine, and out let pressure at atmospheric level. What should I use for inlet and outlet boundary conditions for velocity? Please see the figure.

Sincerely,

Farzad Farajidizaji

Understanding the results from a open air channel simulation: The output shows very different results when using [Inlet, Outlet,...] Opening vs Entrainment BC. No steady one-direction forced air [fan, pump...] is used, so inlet/outlet BC can't be used and the available air stream(s) is/are turbulent.

- It seems that opening BC has one-directional flow in contrast with all-direction flow entrainment BC?

- If correct, does it explain the huge discrepancies between the inlet(s), outlets(s) flow rates... output results?

Requested information: What should be used as boundary condition (inlet, outlet, etc...) in this condition?

Thanks

I would like to ask that, is that possible to make a for loop with the different boundary conditions via the PyFluent interface? In addition, is that possible to analyse different sized geometries? For example 2 different diameters for a pipe geometry. Can we import 2 different geometry and mesh with the PyFluent script?

I am more interested in knowing the impact of electrodes dimensions rather than the geometry factor on OFET's characteristics, e.g. ON current.

I am working on wind interference effect in Ansys CFD. Even though the domain and geometry are symmetric, the results in the contour in CFX are not symmetric on Leeward side of the wind but the contour is symmetric in windward side of the building what could be the reason, what are the parameters should I check on?

My system is composed of 3 bodies, and the middle body will be the host of a reaction. All those three systems have the porous zone option activated. I want the water liquid which flows through the undermost body and arriving the porous jump boundary, passing through this boundary, reacting with the chemicals I designated in the middle body, creating those other products, and finally once again those products for this time passing through the second porous jump boundary and reaching to the uppermost body.

I hope you could imagine the system. Now I created 2 cell zones just above these porous jump boundaries with a width of 1 grid cell which was 8 m for my case, and also set the Y velocities of those interior cell zones as 0. Logically, since they are just above the porous jump boundaries they are actually in-situ of the reaction area(the middle body). So, I did activate the porous zone and reaction options for my cell zones, and set '0' value for the Y velocities in the fixed values tab (A researcher who encountered the same problem proposed this method, so I wanted to give it a try.).

Now, as for porous jump boundaries, I still set them as porous jump boundaries which I believe where the problem arises. When I didn't create a namedselections for them in mesh section, ANSYS Fluent gives the error for example:

Error: Species are not solved in neighbor cell threads (14 and 16)\n of interior zone 6. \n

Error Object: #f

but when I set them as porous jump boundaries, this time it gives an error of segmentation fault, no flow detected at porous jump 7(exp.).

One more thing, the properties of the porous jump condition:

FACE PERMEABILITY: 1e+10(default) How do I set it, I have a mesh system of 5000x5000 m and 40000 elements(grids) in this system

POROUS MEDIUM THICKNESS: 0 it is.

PRESSURE-JUMP COEFFICIENT: 0(default) I saw some calculations for cylindirical studies but I don't know how to calculate it or what are the values for 2D planar structures(systems).

What is it that I'm doing completely wrong and/or fail to notice?

Any comment would be much appreciated. Thanks in advance.

Cheers,

Selvi

I'm trying to solve the heat equation for a ring (Laplace) in a polar coordinate system with Dirichlet condition in r=Ra and a mixed boundary (Dirichlet and Neumann) in r=Rb. There is an analytical solution for this value problem? Which method is the indicate?

The geometry problem is like the image attached