OpenFOAM - Science topic

Mehran Sharifi, thank you for your response. I’ve already tried many of the points you mentioned. I believe the problem comes from the geometry itself. I tried using createBaffles for the internal elements, but I realized that this method creates two faces of my elements rather than a solid element inside. In OpenFOAM, it’s quite rare to do that (i.e., create volumes with boundaries inside a room), which is why I was struggling to find a solution.

However, I switched to an empty room at the beginning by changing from OpenFOAM 12 to ESI OpenFOAM, where I can choose specific solvers (in my case, I used buoyantSimpleFoam). In this scenario, the simulation is running well with no bounding values.

That said, I still don’t have a solution for creating internal boundary volumes in OpenFOAM. If you have any ideas, I’d be happy to receive a few hints! 😄

Thanks Douglas! Currently only numerical effort, as looking to run extensive parameter optimisations of the geometry (shield). We're following a 'minimal viable product' approach (blended with scientific validation). We're looking for sufficiency, not cutting-edge (in other words).

I've tried in an amateur fashion to visualise 'theatre smoke' while talking but I don't think I can capture the dominant motion, but as I haven't done experiment methods before I'm guessing I'm missing something.

Depending on whether I can get collaborators will dictate the the strategy. We're very underfunded and could probably spend that money in more effective ways than proving the science (unfortunately).

Hi Marios

It depends on the boundary condition you use at the walls for k and omega. If you use the wall function for k and omega, OpenFOAM models as high Re formulation, whereas if you use fixed value of turbulence kinetic energy as zero, then OpenFOAM models as low Re formulation. You can refer to wolfdynamics documents related to turbulence modeling to get more understanding on this topic.

I hope this information helps you.

Thanks

Hi Ben Wu

Easier or better? ANSYS Fluent is by far better than Flow3D for general use. However, it is more complicated and requires more time to learn.

Thanks Balaji Mohan! Wondering why don't you modify off-the-shelf ML from Google, FaceBook, etc, to cut development times?

Is Coverge CFD 'black-box', or can you see the code? Can you still have a functional solver if the company deoesn't like what your doing and pulls the license? I'm definitely an open-source advocate, based on equity reasons.

What you are referring is defined as Y_plus defined as y+=(rho*y/mu)*u_tau

I am interested in your question but it needs a lot more explanation. Let me explain what I'm wondering about that I'd need to know to think about your question: If you are solving a F(u)=b, the residual is

Residual = b-F(u_approximate).

This is a vector with a lot of components so plots are usually some sort of aggregate statistic.

So what is your system?? Sometimes, people solve F(u)=b by time stepping: (u_n+1 - u_n)/k + F(u_n)=b then the residual means the discrete time derivative. Sometimes codes are written to be very memory efficient so they calculate something they call a residual that is just some easy to get data that serves as an optimistic proxy.

Maojin Gong This AI response is not false as it could be sufficient for a reader Lamda. However, it is not scientifically accurate as we are on a research thread. Furthermore, it does not display the mentioned references...

Hi Nishidh Shailesh Naik Burye ,

If you have a constant, uniform, fixed shear stress field, OpenFOAM does have a "fixedShearStress" boundary which takes as input the vector value of \tau (assuming its constant over the entire boundary).

If you have anything more complicated (like a non-uniform shear stress field), you will unfortunately have to get your hands dirty coding a custom boundary condition. The easiest way would be to make a copy and modify the existing fixedShearStress boundary in OF. It imposes a Dirichlet boundary based on the velocity normal gradient field (from tau) and the cell-centred values of the velocity field from cells neighbouring the boundary. If you do follow this approach, it is important to just make sure you cancel out any velocity in the boundary normal direction, to make sure you don't accidentally, while converging, introduce inlet or outlet flow across the boundary.

Regards

<patchName>

{

type fanPressure;

file "fanCurve";

outOfBounds clamp;

direction in; // in | out

p0 uniform 0;

value uniform 0;

// Optional entries

U U;

phi phi;

}

CFD softwares are based on numerical methods or techniques to predict the fluid behavior for various conditions e.g. LES and RANS turbulence modelling etc. Unlike exact solutions , the numerical methods involve approximations of the governing fluid parameters which cannot be evaluated at once and thus need iterative computational solvers.

During this process several types of errors are introduced while approximating variable property e.g round off errors ( machine precision) , truncation errors depending on the type of numerical scheme used.

However , according to the nature of fluid and it's interaction with surrounding environment , ( in your e.g yplus wall function which is measure of the fluid friction resistance near wall ) the solutions obtained through numerical schemes present a significant source of error which can interpret the fluid behavior in entirely different manner.

Therefore, the solution is often tested by repeating the process using better approximations and schemes with a focus to obtain the exactness of parameter value leading to iterations.

During iteration process , the error can amplify or reduce ( which is indicative of the stability of solution ) depending on boundary conditions used to obtain solution. So, often an error tolerance is introduced as condition in numerical algorithm to make the solution more meaningful and realistic which closely approximates the fluid behavior. In your case wall shear stress is being approximated using wall units in logarithmic boundary layer.

Once that condition is satisfied, the process stops and proceeds further by evaluating the next dependent variable and so on until complete solution is obtained.

If you go with Amazon Kindle, there is an option to publish one chapter at a time called Kindle Vella. The details are at the top of the page after you log in. It's intended for fiction but would work for other subjects. I have published 81 books on Amazon (62 of my own + 19 for friends and family). It's a good option.

Hello Sayar and Balachandran Nair,

I am trying to make this geometry. Circular inlet in a rectangular boundary wall.

How can I do it? Is it difficult with OpenFOAM?

Thanks.

To me your results make perfect sense. Firstly, the thickness of the velocity boundary layer is dictated by the thermal boundary layer (buoyancy depends on density differences caused by the varying temperature). Increasing Pr, e.g. by decreasing the thermal diffusivity will lead to a thinner thermal boundary layer, hence also a thinner velocity boundary layer. Given that the buoyancy forces are the same (temp.difference is constant), the thinner velocity boundary layer yields higher shear stresses and as a consequence a lower maximum velocity. Increasing Pr by increasing viscosity would also reduce the max fluid velocity simply because of the increased viscosity.

Many hyporheic zone related studies have modelled this. The river-groundwater interface is treated as a pressure boundary.

Hi Bidesh,

I recently ran into a similar error when I use fe4.1 to solve a multi-mesh region case and I am wondering how you solved this problem? What is the cause?

Best,

Young

Without the full details of your flow problem and numerical method is not possible to answer.

What is the min and max alpha level you have set? Also, have you checked if the unrefinelevel and maxrefinelevels are set properly? Generally, changing the domain size should not affect the AMR.

Dear Gonzalo,

can you perhaps share your OpenFOAM case to have a look?

Thanks!

Both open-source software like OpenFOAM and commercial software like Abaqus are capable of simulating a wide range of multiphysics problems, including phase change, two-phase flow, mechanical stress, and microstructures. However, the choice between these two software packages can depend on several factors, including your specific research needs, budget constraints, and familiarity with the software.

Here are some considerations for each software package:

To find a comparative study or article that directly compares OpenFOAM and Abaqus for your specific research needs, you can perform a literature search on academic databases like IEEE Xplore, ScienceDirect, or Google Scholar. Use keywords related to the multiphysics aspects you're interested in, such as "phase change simulation," "two-phase flow modeling," "mechanical stress analysis," and "microstructure simulation," combined with "OpenFOAM" and "Abaqus."

Keep in mind that the choice between these two software packages should also consider your familiarity with the software, the availability of technical support, and your institution's resources. Additionally, you may find that for certain research projects, a combination of both software tools may be beneficial, leveraging the strengths of each for specific aspects of your simulations.

You can use libAcoustics libary for noise prediction in OpenFOAM

Hi,

I guess you could chose one of the two fluid inter solvers. They are based on Volume of Fluid and easy to apply. But you should really take care about cell resolution for good results of course. To take account for natural convection just apply boussinesq or polynomial thermophysicalProps. For polynomials you need to fit function coefficients according to your const. Pressure and temperature range. Unfortunately it can happen, that property calculation is not that precise.

On the other hand it is possible to chose euler solvers instead of inter solvers of course. But in my opinion you need really deep knowledge about all those empirical coefficients.

Hope that helps.

Regards David

I found this solver : -

Hi Bowen Li

can you draw a schematic from problem for me?

Is your software Fluent?

Both OpenFOAM and SU2 are popular open-source CFD codes with active communities and extensive capabilities. However, the choice between them depends on your specific requirements and preferences. Here's some information to help you make a decision:

In addition to OpenFOAM and SU2, there are other open-source CFD codes you can consider, such as:

Remember to thoroughly evaluate the features, documentation, and support for each code to determine which one best suits your specific needs and goals.

To extract a specific part of the flow field in OpenFOAM and start a new project on it, you can follow these general steps:

1. Identify the region of interest: Determine the specific part of the flow field that you want to extract for your new project. This could be a particular geometry, a region within the domain, or a specific time frame of the simulation.

2. Define the extraction criteria: Specify the criteria for extracting the desired part of the flow field. This can include conditions based on geometric boundaries, cell labels, time steps, or any other relevant parameters.

3. Use the appropriate OpenFOAM tools: OpenFOAM provides several utilities and functions that can help with extracting and manipulating the flow field. Some commonly used tools include:

- `patchAverage`: This utility can be used to extract averaged values on a specified patch or surface.

- `foamToVTK`: This utility converts OpenFOAM data to VTK format, which is widely supported by visualization tools.

- `sample`: The `sample` utility allows you to sample the flow field at specific locations and save the data in a new file.

- `fieldMinMax`: This utility can be used to find the minimum and maximum values of a field within a specific region.

4. Write custom code or scripts (if needed): Depending on your specific requirements, you may need to write custom code or scripts to perform more complex extraction tasks. OpenFOAM provides a comprehensive C++ library for customization and development.

5. Start a new project: Once you have extracted the desired part of the flow field, you can start a new project based on it. This may involve setting up a new case directory, adjusting boundary conditions, mesh refinement, or any other necessary modifications for your new simulation.

6. Perform analysis or simulation: With the extracted flow field and the new project setup, you can now perform your desired analysis, post-processing, or simulation on the specific region of interest.

Remember to carefully document your steps and maintain clear organization to ensure reproducibility and traceability of your work.

Yes. OpenFOAM can be used for flow and fluid structure interactions encountered in hemodynamic flow problems.

OpenFOAM and ANSYS Fluent are mainly based on finite-volume method. Whereas, COMSOL is mainly built based on finite-element method.

The notable difference between OpenFOAM and the other two commercial softwares will be the user-interface. OpenFOAM is inherently built on a TUI. Whereas, ANSYS and COMSOL have a very user-friendly GUI.

But, OpenFOAM is very powerfool for research purposes due to its easy customization possibilities.

Meshing using blockMesh of OpenFOAM can be tedious for complex geoemtries. Hence, you have to depend on some third-party meshing applications and snappyHexMesh, etc.

Whereas, ANSYS and COMSOL have better stand-alone meshing capabilities.

As you can see, the RANS solution produces an averaged field over the sphere also for laminar vortex shedding.

However, if you have a fully laminar flow, simply solve for it. If You think to have transitional conditions, Depending on you computational power, use LES or DNS.

Hello! I use COMSOL Multiphysics, not for batteries though. But I would recommend it for you too, like Hitesh Kumar Sinha said, as they also have free webinars and example models on their website.

The module you need is https://www.comsol.com/battery-design-module.

Free webinars (feel free to search for more):

https://register.gotowebinar.com/register/5571335796620423766.

You can download the application files for these models:

Hope this helps.

Hongxiang Yu

In general, for dynamic mesh simulations, models that involve additional terms in the turbulence kinetic energy equation, such as WALE (Wall-adapting Local Eddy-Viscosity) or dynamic Smagorinsky, may be more suitable. These models account for the effects of mesh deformation on the turbulence field and can improve the accuracy of the simulations.

WALE model includes additional terms in the eddy-viscosity calculation that account for the effects of rotation rate, strain rate, and dissipation rate. This model can be more accurate for complex flows with high strain rates and rotation rates, such as flows with vortices or swirling motions.

On the other hand, the Smagorinsky model is a popular choice for LES simulations in OpenFOAM and is widely used for a range of flows. This model uses a constant eddy viscosity coefficient that is proportional to the grid size, which means that it can be computationally efficient for large-scale simulations. However, it may not be as accurate for complex flows or when mesh deformation effects are significant.

When choosing an LES model for dynamic mesh simulations, it is important to consider the specific characteristics of the flow and the desired level of accuracy. It is also recommended to perform sensitivity studies to investigate the effect of different LES models on the results and to validate the simulations against experimental data or other established methods.

Hi Lee,

Why not you obtain the force from OpenFOAM and then calculate the force coefficients by yourself. It takes you much more time to go deeply in the code.

By the way, you might find more solutions in CFD online forum.

Best Regards,

Yongbo

Farzad Farajidizaji

1- It is possible to generate a harmonic impact test (HIT) inside a rectangle, but the specific terminology for this type of test may vary. HIT is a type of test used to study the response of a structure to dynamic loading. A HIT inside a rectangle would involve applying a dynamic load to a structure in the shape of a rectangle. The specific terminology used to describe this test may vary depending on the field or industry.

2- If Nx = Nz but Ny is different, you can still calculate the power spectrum by analyzing the frequency components of the signals along the three different axes (Nx, Ny, Nz). The frequency components can be obtained using a Fast Fourier Transform (FFT) or similar technique. The power spectrum can be calculated by squaring the magnitude of the FFT and normalizing the result by the number of data points. To account for the difference in Ny, you may need to apply some modifications to the normalization or analysis process.

After getting to know more about C++ and OpenFoam, I wanna provide an answer to my Q (which is not yet answered!!!). It can be helpful for those who are facing similar problems.

For coupled boundary condition, there are generally two methods in CFD which are ((Partitioned)) and ((Monolithic)).

using the first method, you should firstly define an iteration-based algorithm especially to satisfy the boundary condition (BC)at the interface of the regions (some solvers use this approach).

in second one (Monolithic), you do not need to separate the regions. you can consider just one region for your simulation. In openFoam language, It means that you have just one (fvMatrix) to solve for every EQ. In my case, it is more convenient to use the second method. So, generally you can follow the steps below:

1- Consider the most general equation that can be used for all the regions with modified coefficients (properties).

2- Define your fields (volFields<>).

3- Use setField utility to adjust the coefficients of the equations(properties) according the region.

4- You should simply define just uncoupled BC.

Be aware that in some cases it would be better to (or you must) choose Partitioned method.

Good luck.

Hi,

You also have BLAST and, for this, the Battery Software Open Source Landscape, BOLD, GT-AUTOLION...

For more information about this subject, I suggest you see the links on the topic.

Best regards

First, I would recommend NOT using png. Journals usually require high-quality vector graphics, so vector eps/pdf should be preferred.

If the comparison is visual, then you might show an array of figures like

mesh1 k-e mesh1 k-w

mesh2 k-e mesh2 k-w

Although presentation of results is mostly a subjective matter, I would arrange smaller figures closer and easier to compare rather than large figures far from one another. This depends a lot on the kind of comparison you have to perform, however.

Hi Anglia,

I would say that OpenFOAM is a great software for your project. OpenFOAM's compressible solvers rhoSimpleFoam or rhoPimpleFoam are initially a good choice.

Regarding optimisation, OpenFOAM also has solvers to perform shape and topology optimisation which can be helpful for your application. Nevertheless, the adjoint implementation is not as straightforward as it can initially seem and currently is somewhat restricted to incompressible flows.

You can check the article from C. Othmer to give you a good perspective on the whole fluid mechanics adjoint implementation.

Hope that you find it useful

Zhuo Zhang Dear Mr. Zhuo Zhang

I tried to use the ICEM to generate the MultiBlockMesh and imported it into OpenFOAM. However, the solver ANSYS Fluent only supports unstructured mesh. So, I wonder what solver you chose when you output the MultiBlockMesh? Any comments or help is welcome.

Regards

Samuel Oluwakorede Oyefusi Thanks for your suggestion.

Rishikesh Mishra Thank you very much.

Hi, I'm welling to help you. I work with Ansys Fluent. I'm interrested in learning to work with Openfoam. If you are interrested, we can try to find a preresult using Ansys and then do the work using Openfoam and then compare results of both codes.

Have you tried the Gambit?

The fault was in controlDict file thanks for responding. I have solved it.

For the pressure B.C, you can use zeroGradient boundary (of course you define pressure initially and suitable pressure BC at the inlet or better at the outlet of the flow). On the other hand velocity B.C is very important in your case look into noSlip, Slip, zeroGradient and partialSlip boundaries.

You should pay attention to near-wall region especially if you have a turbulent flow.

Hello Mrs. Raeisi, I am not sure what you mean by having access (you cannot read the files, or find/access the folders), but maybe it can be related to sudo permissions. Depending on the version you are using and how you installed it (some tutorials says to use super users permissions when installing). So, you can try to change the permissions of the folders.

Yes, and it does not show good precision.

Yes, Im interested.

did olaflow compatible with openfoam 2112????

The more stable solvers 'RheoTool' for viscoelastic fluid flow simulations is developed by Pimenta et al. The solver, along with tutorials, is available is https://github.com/fppimenta/rheoTool

You cannot directly import a CAD file into Openfoam. You need to convert it into a good surface mesh (STL) and then use snappyHexMesh or cfMesh to create a hex-dominant mesh. Then, use checkMesh utility to verify the mesh quality. Also, you can visualize the mesh in Paraview.

Hi, if you are using a compressible solver, you should give rhoInf the value of the "free stream density", so the density of your medium far from your region of interest, where the compressibility effects occur, in kg/m^3.

If your solver is incompressible, I think you could leave out rhoInf completely, but I am not sure. Probably for a LPT solver you may still need to specify it. Then just put in the value of the then constant density. Your solver is called pimpleLPTFoam? If it is based on pimpleFoam, it should be incompressible.

For a start, you can just try what it does, if you either leave rhoInf out, or give it a random value. After that, you may need to find out what the correct value is for your case.

you can use TemporalStatistics filter.

@Anoop Narain Singh, you need to learn a little bit ubuntu. You can search your questions in OpenFoam forum website:

Yade is open source and allows the use of non-spherical particles (angular polyhedral or clumps of round particles to make complex one). It works with granular flow, but you can also have your solid particles in a fluid by using the integrated version with OpenFoam (you need to compile it and can't use the version that is pre-compiled). It works rather well and it is easy to install and use on Linux. There is a good library of examples and tutorials.

Pradyumn Chiwhane I am posting here a previous answer I provided on submerged oscillating bodies in quiescent fluid. The total force exerted by the fluid on the cylinder, you should consider besides the drag the added mass force. Academic references are provided within the following research projects:

Qamar Ul Islam thank you for your answer. Actually, I have found a feasible way to interact them and would like to share them with you.

If you want to do a gradient-based optimization, the best framework is DAFoam which integrates Open foam and python in a very practical way for running gradient-based optimizations. On the other hand, if you want to run a gradient-free optimization like me, the pyOptSparse is the ultimate choice as it has multiple optimizers included, but the only thing that remains is the interaction with OpenFOAM which I think is very feasible by adding some lines of code in the script.

Best wishes

Dear Harshal Akolekar,

I have just come across your question. Maybe you already found the solution, but I wanted to add this answer in case it is still useful to you or others.

You could try converting from structured to unstructured grid with VTK and later convert to FOAM with the built-in vtkUnstructuredToFoam tool. A starting point would be adding a structured VTK reader and later following the approach in the following thread to write an unstructured one: https://public.kitware.com/pipermail/vtkusers/2016-November/097119.html.

Hope this helps too.

Kind regards,

Carlos.

Taha Zier, if you have the function that represents your Gaussian distribution pulse you can implement that using uniformFixedValue BC. There's a usage example for a step function in the documentation:

https://www.openfoam.com/documentation/guides/latest/api/classFoam_1_1Function1Types_1_1Function1Expression.html#details

The example is for a vector BC. You would need to remove the 'vector(1, 0, 0)' and put your expression for the scalar.

If you already have a table file data represents your pulse, you can also set your BC with:

https://www.openfoam.com/documentation/guides/latest/api/classFoam_1_1Function1Types_1_1TableFile.html#details.

Hope the above helps. If you can provide with the function you want to reproduce for the 0-2 seconds I would be happy to share a reproducible example. Please see the discussion below in case it's relevant:

Best regards,

Carlos.

I refer you to two discussions which bear on the two problems of Eulerian two-fluid models closures: Turbulence and momentum interfacial transfer:

(6) Turbulence Closure for Two-Fluid RANS Modeling (researchgate.net)

(6) Interfacial Transfer Closure for Two-Fluid RANS Modeling (researchgate.net)

Look forward to exchanges on these topics

Daniil A. Ryazanov Thanks for your help.

I would prefer to use the TRNSYS software. TRNSYS is a transient systems simulation program with a modular structure. It recognizes a system description language in which the user specifies the components that constitute the system and the manner in which they are connected. The TRNSYS library includes many of the components commonly found in thermal and electrical energy systems, as well as component routines to handle input of weather data or other time-dependent forcing functions and output of simulation results. The modular nature of TRNSYS gives the program tremendous flexibility, and facilitates the addition to the program of mathematical models not included in the standard TRNSYS library. TRNSYS is well suited to detailed analyses of any system whose behaviour is dependent on the passage of time. TRNSYS has become reference software for researchers and engineers around the world. Main applications include: solar systems (solar thermal and photovoltaic systems), low energy buildings and HVAC systems, renewable energy systems, cogeneration, fuel cells.

I think these articles may help you:

Hi Divyajyoti,

you definitely have to export the mesh from Fluent in ASCII format. So here you didn't make a mistake. I assume that there is another problem: Do you have a folder "system" with a file "controlDict" in the directory "sub"? FluentMeshToFoam and Fluent3DMeshToFoam somehow check, if this folder and file exist.

Best regards, Florian

You can give a chance to Gmsh software. Just upload your .stl file and try different meshing algorithms.

https://gmsh.info/

check the articles that I have attached:

Thank you very much for this information. Can you kindly give some idea when we expect its release?

@Kazi Md. Jahid Hasan, I agree that we can do transient vortex-resolving simulation of flows with OpenFoam. I have used it for such simulations several times. But since it is 2nd order, truncation error can be larger or comparable to modelled properties. See for example Smagorinsky model, where nut is proportional to dx^2. Therefore, I don't think OpenFoam implements LES technology strictly, but most likely it works as something similar.

As i know, there is one third order implementation for OpenFoam by Wildkatze and Arjun Yadav, but I'm not sure whether it is open to community.

The second question is diffusion introduced in implementation of Rhie-Chow interpolation. This artificial diffusion term presents in all transient OpenFoam viscous solvers, regardless of version. Value of this term was unsatisfactory large for some of my problems, that's why I've changed original algorithm. If you want to do LES-like simulations with OpenFoam, then probably you should tune original solver.

Finally, you can take any latest version from openfoam.org (v.9) or openfoam.com (v. 2106) and it should give you similar results if you use incompressible viscous flow model.

Hi, you can try:

1) reactingPimpleCentralFoam, which is a part of https://github.com/unicfdlab/hybridCentralSolvers

2) reactingLagrangianQGDFoam, which is a part of https://github.com/unicfdlab/QGDsolver#QGDsolver-library-brief

You can use special packages:

1) precIce

2) openPalm

Interesting

Interesting

Use on OpenFOAM the following command:

fluentMeshToFoam [options] [file.msh] ;

If it is a 3D mesh, only put 3DMesh on the above command. Please refer to this wiki to have more information: https://openfoamwiki.net/index.php/FluentMeshToFoam

You're welcome Ivan Nepomnyashchikh