Merging LES Model of MCRE Loop#811
Open
hapfang wants to merge 6 commits into
Open
Conversation
|
Job VTB Documentation, step Sync Docs on 8d8bcae wanted to post the following: View the site here This comment will be updated on new commits. |
GiudGiud
requested changes
May 27, 2026
|
|
||
| [Steady State Results](lotus_results.md) | ||
|
|
||
| [CFD Model of LMCR Loop](lotus_cfd_model.md) |
Collaborator
There was a problem hiding this comment.
Suggested change
| [CFD Model of LMCR Loop](lotus_cfd_model.md) | |
| [High fidelity CFD Model of LMCR Loop](lotus_cfd_model.md) |
|
|
||
| *Contact: Jun Fang, fangj.at.anl.gov* | ||
|
|
||
| *Model link: [LMCR nekRS LES Model](https://github.com/idaholab/virtual_test_bed/tree/mcre/msr/lotus/les)* |
Collaborator
There was a problem hiding this comment.
Suggested change
| *Model link: [LMCR nekRS LES Model](https://github.com/idaholab/virtual_test_bed/tree/mcre/msr/lotus/les)* | |
| *Model link: [LMCR nekRS LES Model](https://github.com/idaholab/virtual_test_bed/tree/devel/msr/lotus/les)* |
| description=High-fidelity large-eddy simulation model of the LMCR primary loop using nekRS | ||
| image=https://github.com/idaholab/virtual_test_bed/tree/mcre/doc/content/media/msr/lotus/les/mean_Umag.png | ||
| pairs=reactor_type:MSR | ||
| reactor:LMCR |
Collaborator
There was a problem hiding this comment.
is that acronym really used? I m thinking either LOTUS_MSR or generic_MCR ?
| open_source:partially | ||
| computing_needs:HPC | ||
| fiscal_year:2024 | ||
| institution:INL |
Collaborator
There was a problem hiding this comment.
this tag needs to move it sits above your page
| institution:ANL | ||
|
|
||
| !alert note | ||
| The CFD solver nekRS is not included in the VTB CI test suites yet. Users are encouraged to reach out to the nekRS developer team at Argonne by emailing the POC (Jun Fang at [fangj@anl.gov](mailto:fangj@anl.gov)). Additionally, a beta version of the nekRS tutorial is available at the [nekRS Documentation](https://nekrs.readthedocs.io/en/latest/index.html). |
Collaborator
There was a problem hiding this comment.
Suggested change
| The CFD solver nekRS is not included in the VTB CI test suites yet. Users are encouraged to reach out to the nekRS developer team at Argonne by emailing the POC (Jun Fang at [fangj@anl.gov](mailto:fangj@anl.gov)). Additionally, a beta version of the nekRS tutorial is available at the [nekRS Documentation](https://nekrs.readthedocs.io/en/latest/index.html). | |
| The CFD solver nekRS is not included in the VTB continuous integration test suite at this time. Users are encouraged to reach out to the nekRS developer team at Argonne by emailing the POC (Jun Fang at [fangj@anl.gov](mailto:fangj@anl.gov)). Additionally, a beta version of the nekRS tutorial is available at the [nekRS Documentation](https://nekrs.readthedocs.io/en/latest/index.html). |
|
|
||
| The LOTUS Molten Chloride Reactor (LMCR) is an open-core, fast-spectrum, liquid-fueled molten salt reactor concept that circulates chloride fuel salt through the reactor vessel and primary loop. The fuel salt, represented here by a UCl$_3$-NaCl eutectic mixture, provides both the fissile material and the primary heat-transfer medium [!citep](MCRreport2022,M3mcr2023). The high-fidelity computational fluid dynamics (CFD) model documented on this page represents an MCRE-like LMCR primary-loop configuration in which the unmoderated core cavity is connected to a curved inlet pipe, outlet pipe, pump region, and heat-exchanger leg. The checked-in nekRS case name is `mcre`, so the run files retain that historical name even though this VTB page documents the LMCR primary-loop LES benchmark. | ||
|
|
||
| Because fission energy is deposited directly into the circulating fuel, the flow field controls more than pressure drop and heat removal. It also affects delayed neutron precursor residence time, spatial reactivity feedback, and the temperature field seen by lower-fidelity multiphysics models. The open core cavity does not contain internal structures that would homogenize the incoming jet. As a result, centrifugal acceleration from the upstream elbow drives the inlet stream toward the vessel wall, producing strongly three-dimensional recirculation, large coherent eddies, and persistent short-circuiting paths between the inlet and outlet. |
Collaborator
Collaborator
There was a problem hiding this comment.
I dont think we have it in the VTB pgh model either
| This nekRS model is intended to generate high-resolution large-eddy simulation (LES) data for understanding the LMCR primary-loop hydrodynamics and for calibrating engineering-scale thermal-hydraulic tools such as Pronghorn. The current checked-in case solves the incompressible isothermal flow problem with the temperature equation disabled, so the documented fields focus on velocity magnitude and the vertical velocity component. Accordingly, this study is centered on the loop flow velocity distribution and its turbulence characteristics. | ||
|
|
||
| !alert note | ||
| The case files are stored in `msr/lotus/les`. The checked-in `mcre.par` file is a demonstration template. To speed up start-up and develop the turbulent state more quickly, begin runs with a lower polynomial order (for example $P=3$ or $P=5$) and a reduced Reynolds number. After the transient has developed, set the nondimensional viscosity to `1/10742.82` and restart at a higher polynomial order (for example $P=7$) to run the long averaging production calculation. |
Collaborator
There was a problem hiding this comment.
Suggested change
| The case files are stored in `msr/lotus/les`. The checked-in `mcre.par` file is a demonstration template. To speed up start-up and develop the turbulent state more quickly, begin runs with a lower polynomial order (for example $P=3$ or $P=5$) and a reduced Reynolds number. After the transient has developed, set the nondimensional viscosity to `1/10742.82` and restart at a higher polynomial order (for example $P=7$) to run the long averaging production calculation. | |
| The case files are stored in `msr/lotus/les`. The checked-in `mcre.par` file is a demonstration template. To speed up start-up and develop the turbulent state more quickly, you should begin runs with a lower polynomial order (for example $P=3$ or $P=5$) and a reduced Reynolds number. After the transient has developed, set the non-dimensional viscosity to `1/10742.82` and restart at a higher polynomial order (for example $P=7$) to run the long-averaging production calculation. |
or longer averaging-production?
|
|
||
| where $u_i$ is velocity, $p$ is pressure, $\nu$ is kinematic viscosity, and $f_i$ is the user-defined momentum source used to drive the loop. The checked-in case disables the scalar temperature solve because this stage of the benchmark is focused on hydrodynamic mixing, residence-time behavior, and velocity-field statistics. | ||
|
|
||
| The high-fidelity workflow uses lower-order transients to develop a turbulent initial condition before restarting at higher polynomial order for the production averaging run. In the documented analysis, initial transients were developed with $P=5$, while the final LES statistics targeting $Re \approx 10{,}742$ used $P=7$ for improved turbulent-scale resolution. |
Collaborator
There was a problem hiding this comment.
production averaging is LES-talk btw. Might be friendlier to define it?
|
|
||
| ## Running the Case | ||
|
|
||
| A typical nekRS workflow is to compile the case, run a lower-cost transient to establish a turbulent state, and then restart at the production polynomial order for time averaging. The exact module names and executable paths depend on the target machine, but the following commands illustrate the expected sequence from the `msr/lotus/les` directory: |
Collaborator
There was a problem hiding this comment.
you don't explain how to restart?
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
The PR related to #802 is now ready for review and merging.