Langley Research Center

Turbulence Modeling Resource

Model Readiness Rating (MRR) System

The model readiness rating system is a system for labeling the "readiness" of models so that developers and users can assess the maturity of a given model when determining whether to implement and test it for their own specific applications. This system does not judge the quality or capability of turbulence models. Instead, it is intended to provide information to the end user regarding how "well-defined," "well-used," and "well tested" a model is. A model that has been implemented and used in multiple codes and by multiple people will receive a higher rating than a model that has only been implemented and used in a single code. Furthermore, an attempt is made with this rating system to insure that the same model version in multiple codes will yield very close to the same results.

Disclaimer: The MRR level is based on applications and implementation associated with this website only. It does not account for possible independent codes, usages, or results that the TMBWG does not have access to. Therefore, the MRR rating is not to be construed as a broad assessment, but rather as the opinion of the TMBWG based on its own limited testing.

Comments about the system are welcome. Please contact the Turbulence Model Benchmarking Working Group (TMBWG).

MRR Level

Description	Level 0	Level 1	Level 2	Level 3	Level 4
Sponsor exists for the turbulence model	required	required	required	required	required
Model completely described and referenceable	required	required	required	required	required
Model in at least 1 CFD code		required	required	required	required
Model run on 1 or more verification/validation cases, and results made available		required	required	required	required
Model in two or more codes, and results (reasonably) agree as grids refined			required	required	required
Model run on 2 or more verification/validation cases, and results made available			required	required	required
Model tested on at least one verification case, including full grid convergence study				required	required
Model implemented in codes from at least 2 different organizations				required	required
Results independently obtained/verified				required	required
Turbulence model underwent Method of Manufactured Solutions in at least 1 code					required

Notes:

The minimum level (Level 0) indicates that a model is well-described in a referenceable publication and has a sponsor. This level carries no negative connotations; it simply means that the model in question has not been widely tested or sufficiently verified beyond the original reference as yet.
A sponsor is a person who pushes a given model through the process: running cases and reporting results as necessary, and working with the committee and page curator to meet any requirements needed to list the model on the website.
A thorough grid refinement study should be conducted when documenting the results for any model, so as to unambiguously establish the grid-converged results.
Use of Method of Manufactured Solutions (MMS) may not be easy (or possible) for some turbulence models (see Information from Lisbon "Workshop on CFD Uncertainty Analysis" series). Therefore, Level 4 is considered here to be somewhat of a bonus beyond the very high Level 3 rating. In other words, when MMS is possible, its implementation adds an additional layer of certainty that a turbulence model has been coded correctly, meriting a higher MRR rating.

Turbulence models currently rated at Level 4:

SA - See NASA/TM-2008-215537, Nov 2008 for documentation of MMS

Return to: Turbulence Modeling Resource Home Page

Recent significant updates:
07/05/2016 - added Level 4; also modified requirements for Level 1 and 3 to be consistent with actual practice
05/15/2015 - minor wording change for level 3

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Responsible NASA Official: Ethan Vogel
Page Curator: Clark Pederson
Last Updated: 07/14/2016