I need to simulate a hydrogen explosion near a wall: I need pressure values ​​over time for the structural calculation.
Is it possible to set up the simulation and use BlastFoam in TCFD?
Reading around, I found that the XiFoam or XiFluid solvers exist: does anyone know anything about them? Could they be integrated into TCFD?

Dear CFD Support team,

I am a Master’s student in Mechanical Engineering (Energy Transition specialization) at the University of Brescia, Italy.

For one of my CFD/OpenFOAM exams, I am required to develop a validated simulation project (not a thesis, but an academic project), including comparison with reference or published results. For this purpose, I downloaded your Burj Al Arab simulation example from your platform.

My goal is to reconstruct the case in OpenFOAM and use it as part of my exam project. I would like to kindly ask if it would be possible to receive additional technical details to help me accurately reproduce the simulation in OpenFOAM. In particular, I am looking for:

• Computational domain dimensions and setup;

• Boundary conditions (inlet velocity profile, outlet, wall and ground conditions);

• Turbulence model and main parameters;

• Mesh generation details (refinement regions, layers, resolution);

• Reference values used for force coefficients or validation

If available, even a simplified description of the setup or equivalent OpenFOAM dictionaries (0/, constant/, system/) would be extremely helpful.

The purpose of my work is purely academic, and I aim to ensure the simulation is physically consistent and properly validated.

Thank you very much for your time and support.

Best regards,
Hamza Chokry

I need to simulate this in fluent.

Take a bubble of radius 1 mm with internal pressure as 3 kPa, while the outside liquid is at 1 bar pressure. This bubble is at a distance of 1.1 mm from a flat surface. Gravity acts vertically down.

the bubble is of vapour.

I used multiphase model with VOF.

I created a Rectangular domain to simulate it in 2D with suitable dimensions.

I am facing problems in setting up the pressure difference in and outside the bubble , like I used operation condition has 100kPa , and boundary conditions as pressure oulet for top, right and left side of the Rectangular domain , and wall for bottom side.

Then I patched the bubble with suitable radius, but I am not able to set the presure differnce .

Could anyone help me setting the pressure difference.

I need to learn how to model fire and explosion with cfd. Can any one help me?

Hi, wanted to do Drivaer estate simulation with rotating wheels, moving ground. So i started with tutorial from website, and used the same configuration as starting point, and Cd was way to low, then i changed to Kepsilon back and forth Cd was still low. then i switched to half of car and started to refine mesh and Cd went little higher to 0.3 but still it is inacurate, then refined further and Cd ramped to 0.38 then started to look on Y+ and further refined to achieve average 5, but most of car is 2, and still Cd is very high (0.37), tried also with LowRe wall functions but it seems that Cd is still too high. Any Ideas what to check/ to replicate good- consistent results? Experimental CD for estate is 0.314

Hello everyone,

I have trouble initializing a case using a previous result when I try to run a simulation with the remote computing strategy described in Chapter 7 of the TCAE manual. The graphical interface doesn't allow me to select the source case from the remote machine's files. However, I can do this without any problem when running the same case locally.

Is there a specific procedure for doing this remotely, or is this a bug?

Thanks in advance!

Zacharie

Hi everyone,

It seems to me that the field bounding limits are only applied in stationary simulations, and not in transient simulations. Indeed, in one of my transient tests, many cells of my domain reach values (the velocity in my case) well above the max velocity indicated in SIMULATION/Controls.

Are you aware of this comportment ?

Thanks in advance !

Zacharie

Hello everyone,

I have some questions regarding case initialization:

1) In steady-state simulations, I assume that the conditions defined in the "Initial Conditions" section are only used to initialize the first point of each speedline, and that subsequent points are then initialized from the previously calculated point in the speedline. Is that correct?

2) In transient cases, a new option appears in the "Initial Conditions" section: "Initialize points from the previous point." What happens if this option is not selected? Is each point then initialized with the conditions defined in this section, regardless of its position in the current speedline?

3) Do you recommend simulating the speedline from the highest flow rate to the lowest flow rate, or the other way around (in the case of a centrifugal compressor for example) ?

Thanks in advance!

Zacharie

Hi everybody, 

I ran a steady state + transient CFD simulation on a centrifugal compressor (with a k-omega SST model) and when post-processing the results and comparing the stationary part to the unsteady part of the calculation I have significantly different results. Indeed, the unsteady part shows a higher mass flow rate. This seems to be due to a higher flow speed and a different flow angle, noticeable directly at the inlet of the rotor. On the picture attached you see these differences (on the left: unsteady part; on the right: steady state part). Is it possible that this difference in flow rate could be explained by the fact that the dynamic mesh in the unsteady part could aspire the flow in the rotor and thus change the angle and speed of this one? And maybe this effect could have been lower if I would have set a lower CFL (kept for now to 20 in my case)? 

If you have any ideas about this phenomenon that would be very helpful. 

Thanks and have a great day,

Alex 

Hi everyone,

In the latest version of TCAE (25.03v1), it is possible to set new parameters in the SIMULATION/Controls section: the solver max and min iterations (photo attached). What exactly do these iterations correspond to?

Thanks in advance.

Zacharie Prigent

Hello everybody,

I have a few questions regarding TCAE transient simulations.

1) Are the transient simulations robust?

2) Do you have any recommendations for applying transient simulations  to centrifugal compressors?

3) How do I control the recording of intermediate time steps? I haven't found a way to control it in the GUI, and the controlDict file in ../system/ is automatically restored to its previous version (with the adjustableOnEnd option in the writeControl section), even if we manually modified it before running the calculation!

Zacharie Prigent

Hello everybody, 

I am setting my first CFD transient simulation on a centrifugal compressor and I would like to know if you have any recommendations on the values of parameters like CFL number or PIMPLE algorithm settings. I assume that the default value of CFL number is relatively large (=20 hence >>1) because the PIMPLE algorithm is flexible and that's common to use higher values for turbomachinery applications?

Also, how is the monitoring and post-processing of the results different from the ones of steady state simulations? 

Any clarifications and recommendations would be very helpful. 

Thank you and have a nice day ! 

Alex

Hello everyone,

We are a team of university students currently working on a project to replicate the CFD simulation of the DJI 9450 propeller. First of all, we would like to thank the content creators for the excellent "Acoustic Benchmark Propeller DJI 9450" study. It has been an invaluable resource for our work.

As we try to reproduce the simulation results, we've encountered some confusion regarding the benchmark target values and would be very grateful for any clarification from the community or the official team.

Issue 1: Discrepancy Between Two Reported Results

We have been referencing two main documents:

 [1] The formal PDF research report (Acoustic Benchmark of DJI 9450.pdf).

 [2] The web page report, available at: https://www.cfdsupport.com/download/report/DJI-9450-Propeller-Benchmark/tcfd/TCFDReport.html

We noticed a significant difference in the thrust and torque values at 6000 RPM between these two sources. Specifically:

 * The PDF Research Report [1] lists a target Thrust of 4.256 N and a target Torque of 0.066 N·m.

 * The Web Page Report [2]shows a computed Thrust of 3.438 N and a computed Torque of 0.058 N·m.

Furthermore, the simulation result graph in the PDF report (approx. 4.2 N) also differs from the web page report's result (3.44 N).[1] We suspect this might be due to differences in mesh density. Could anyone confirm if this understanding is correct, and which set of values should we consider the definitive target for our validation?

Issue 2: Question About the Source of the Benchmark Target Value

To delve deeper, we located the original experimental paper cited in the PDF report (Intaratep, N., et al., AIAA 2016-2873).[1, 1] However, upon reviewing this paper, we found that the measured experimental thrust for a single rotor at 6000 RPM is approximately 6.1 N (as read from Fig. 6).[1,1]

This experimental value is considerably different from the benchmark target of 4.256 N listed in the PDF report, which has caused us significant confusion.

Our specific questions are:

 * Could anyone clarify the source of the benchmark target values (Thrust = 4.256 N, Torque = 0.066 N·m) used in the PDF report? Why does this target differ from the ~6.1 N we found in the original experimental paper (AIAA 2016-2873)?

 * To help us perform a more accurate validation and learn from this work, would it be possible to get access to the mesh file (e.g., in OpenFOAM or MSH format) or the complete geometry file (STL/STEP) used for the high-fidelity simulation presented in the PDF report?

Any clarification would be immensely helpful for our academic research.

Thank you for your time and assistance.

Best regards

Hi everyone,

I have a question concerning the mixing plane interface method : it seems to me that the method can generate numerical errors when reverse flow occurs on the interface.

To be more specific, I have a radial interface between the outlet of a centrifugal impeller and the inlet of its diffuser. On a specific zone of the interface, reverse flow occurs with a radial circumferential angle -180° < circAng < -90°, whereas on the rest of the interface, there is no reverse flow and 90° < circAng < 180°. In one of my former post on the forum, you confirmed to me that the weighted surface average of the circumferential angle might be distorted in this situation. It seems to me that the mixing plane method at the interface also encounter issues in this situation to estimate the value of circumferential angles for the inlet patch of the interface, in the strips where circAng oscillate between 90° < circAng < 180° and 180° < circAng < -90°. Indeed, I can see this kind of numerical errors when post-processing my simulations.

Do you have some recommendations to avoid this kind of problems ? For example, use specific configuration options, or different interface conditions ?

Thanks in advance !

Zacharie