TUFLOW Version Backward Compatibility: Difference between revisions

 

=Backward Compatibility Change Register=

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| Testing thus far has not shown any difference between the two methods (other than the substantial gains in processing time of polygons).

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| May change results slightly, but improved stability and a smoother water levels along HX lines result.

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| May change results slightly, but stability should be significantly enhanced in some situations.

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| Will influence results, usually slightly, but more pronounced where there are sudden changes in Manning’s n values such as in the urban environment.

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| Changed the setting of the default width (if eN1 < 0.001) of automatic weirs over R and C channels (i.e. RW and CW) to be the diameter/width multiplied by the number of culverts (previously, the width was not multiplied by the number of culverts).

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| Bug fix that incorrectly set the water levels on dried VG cells (only applies to simulations with source inflows, e.g. SA or RF, somewhere within in the model).

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| Fixed bug that did not correctly apply the reduction in conveyance for a FC BD (bridge deck) of FD (floating deck) cell using the 2d_fc Mannings_n attribute.

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| Uses a new set of defaults for a number of commands.

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| The most pronounced effect of the shallower wet/dry depths is likely to occur in areas that are still filling at the flood peak, such as behind a levee that is only just overtopped. The shallower wet/dry depths provides a greater flow depth for a longer period over the levee.

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| Usually does not have a major influence on results except where very high velocities occur.

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| May select slightly different cells along boundary/link lines. This may cause a difference where the line is along the top of levee, possibly creating a “hole” in embankment.

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| Can have a significant effect where the viscosity term is influential. This occurs where the friction term is less dominant (i.e. low Manning’s n and/or deeper water such as the lower, tidal, reaches of rivers).

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| Can have a significant affect in the vicinity of structures within a 1D network and for culvert networks. Does not affect 1D structures linked to a 2D domain or at the structure ends not connected to another 1D channel.

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| Usually negligible effect unless the model storage is predominantly within 1D closed sections (i.e. B, C and R channels). The 1D domain is likely to be more sensitive to instabilities due to the much smaller storage above the top of the closed sections, therefore, a smaller 1D timestep may be required and/or the Storage Above Structure Obvert (%) increased.

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| No effect as previously the model would have become “unstable” as the trigger for an instability was the top of the channel/node.

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| Usually only minor effects plus improved stability.

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| Minor influence.

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| Negligible influence plus improved stability. However, note the different treatment of energy losses once the bridge deck obvert/soffit is submerged if a BG or LC table is specified.

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| Only affects the presentation of results. Note, that Method A is no longer recommended or supported.

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Does not affect hydraulic calculations, however, if a Blank, B or W channel is now lowered/raised because the inverts are now used, this will affect results/stability - see note at end of Apply All Inverts).

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| Will affect results as ALL PARALLEL can be around 10% more “slippery” than CHANGE IN RESISTANCE. For calibrated or established models developed using build prior to Build 2006-06-AA , recommend setting to CHANGE IN RESISTANCE

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| Negligible effect.

 

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|'''Builds prior to 2006-06-XX'''

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== Why are model results developed in an older release different to a newer release? ==

If comparing a Classic model with HPC, also check the <u>[[HPC_FAQ#Will_TUFLOW_HPC_and_TUFLOW_Classic_results_match.3F | Will TUFLOW HPC and TUFLOW Classic results match?]]</u> page in addition to this answer. <br>

* General improvements and fine-tuning of the solution scheme, especially for the more complex hydraulic physical terms and situations such as: sub-grid turbulence representation; treatment of shocks (e.g. hydraulic jumps); and transitioning between sub-critical and super-critical flow on steep slopes.

* Some new functionality can cause a significant change in results. For example:

** Sub-Grid Sampling (SGS) applied to an existing model that used a too coarse cell resolution in high flow areas of highly variable topography (relative to the 2D cell size). SGS will greatly improve the model's ability to convey water accurately in these situations with vastly improved results.

* Changes to the default settings and values, e.g.:

**different default eddy viscosity formulation and/or coefficients,

* New features that use GIS attributes previously reserved (i.e. unused). If these attributes were not populated with the recommended “reserved” value (usually 0 or blank), then they can cause unpredictable results in later releases.

* Bug fixes noting that most bug fixes are input/output related and rarely affect the model's hydraulic calculations.

* Model orientation (if changed) could also mean slight change in results. This is mostly given by interpolating values from different calculation points. Every cell has nine calculation points. Based on the model origin, all or most of the calculation points would have different topography elevation sampled, which translates to slightly different results.

* If using 1D channel, possibly different cells have been selected as HX boundary and might have different elevations. This can be reviewed in <u>[[Check_Files_1d_to_2d_bc | 1d_to_2d check file]]</u>.

Generally, there should not be substantial differences as the fundamental equations being solved are unchanged and TUFLOW Classic and HPC solvers have always solved all the physical terms using a 2nd order spatial approach. The one exception is the turbulence (eddy viscosity) representation, which is the most complex and challenging to solve of all the physical terms (many 2D schemes simply omit this term). If significant differences (>10% of depth change across the whole model) are observed then it’s most likely due to the first four dot points above. To identify in which release(s) the significant changes occurred, the model can be run with the latest build and for past releases. The changes for each release are documented in their release notes. Past releases and release notes are all available [https://www.tuflow.com/downloads/tuflow-classichpc-archive/. here]. Once the exact release where the changes occurred is tracked down, individual features can be turned off to narrow down the cause.<br>

 

 

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