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Linear Truncation Error Analysis (LTEA) was initially presented by Dr. Scott C. Hagen as part of his doctoral research at Notre Dame. Development has continued on the methodology at the University of Central Florida. The LTEA algorithm performs analysis on an existing [[SMS:ADCIRC|ADCIRC]] mesh and its solution to help quantify the error associated with the mesh. Normally, this [[SMS:ADCIRC|ADCIRC]] solution is taken from a  "linear ADCIRC" run. This type of run is used to make the process faster and to simplify the LTEA algorithm applied to the unstructured mesh. A second phase of the LTEA process uses the error values at each node to create a relative size function covering the domain called DelX.
<!--*NOTE: This feature will be deprecated in SMS version 13.2.  This is the last version of the code that will include this tool. A new python library (pyLTEA) has been under development individuals in the ADCIRC community.  Our intent is to include this library as a tool in the SMS python toolbox.-->
{{SMS Deprecated Feature}}
Linear Truncation Error Analysis (LTEA) Toolbox incorporated into SMS uses the LTEA algorithm as the heart of a utility which creates finite element meshes of varying resolution for ADCIRC analysis. The algorithm was initially presented by Dr. Scott C. Hagen as part of his doctoral research at Notre Dame, and development has continued on the methodology at the University of Central Florida. It performs analysis on an existing [[SMS:ADCIRC|ADCIRC]] mesh and its solution to help quantify the error associated with the mesh.  


== The LTEA Toolbox ==
Normally, this [[SMS:ADCIRC|ADCIRC]] solution is taken from a "linear ADCIRC" run. This type of run is used to make the process faster and to simplify the LTEA algorithm applied to the unstructured mesh. A second phase of the LTEA process uses the error values at each node to create a relative size function covering the domain called "Del X". This refines the mesh where the element error values would be greatest such as near shorelines or around islands.
[[File:ADCIRC MeshGenerationToolbox.png|thumb|230 px|ADCIRC ''Mesh Generation Toolbox'' dialog]]
SMS includes a graphical interface that allows the user to use the LTEA theory to guide the generation of a finite element mesh.  The tool requires two inputs which must be loaded into SMS. These include:


== Mesh Generation Toolbox Dialog ==
[[File:ADCIRC MeshGenerationToolbox.png|thumb|230 px|''Mesh Generation Toolbox'' dialog]]
SMS includes a graphical interface that allows using the LTEA algorithm to guide the generation of a finite element mesh. Before using the tool, ADCIRC must be run in order to generate the datasets necessary for LTEA to run.
The tool requires the following inputs to be in the Project Explorer:
* A bathymetry scatter set.
* A bathymetry scatter set.
* An ADCIRC coverage having at least one polygon with the boundary conditions assigned.
* A 2D mesh.
* A mesh generation coverage having at least one polygon.
 
The following may be required, depending on the options selected:
* Harmonic ADCIRC solution dataset(s)
 
The toolbox is accessed by:
#Right-clicking on the mesh generation coverage and selecting '''Mesh Generation Toolbox...''' to bring up the ''Mesh Generation Toolbox'' dialog.
#Select "Localized Truncation Error Analysis (LTEA)" from the list and click '''Run''' to bring up the ''LTEA Tool'' dialog.


If wanting to start the mesh generation process from an existing ADCIRC mesh, the user must convert the mesh to both a scatter set and ADCIRC conceptual model, Right-clicking on the mesh in the project explorer gives access to commands to perform the basic conversion.  The conceptual model must be defined on the arcs created in this way.
The ''LTEA Tool'' dialog is discussed in the next section.


The toolbox is accessed through the '''Mesh Generation Toolbox...''' from the ''ADCIRC'' menu in the Mesh Module. From the dialog that appears, select the ''LTEA'' option and click '''Run'''. The steps that follow include:
==LTEA Tool Dialog==
[[File:LTEA Tool dialog first page.png|thumb|right|450 px|The first page in the ''LTEA Tool'' dialog.]]


* Step 1 &ndash; Linear Run Mesh generation. In this step the user must specify the scatter set and conceptual model to be used for mesh generation.  This step generates a basic mesh from the conceptual model to perform a linear run.  This mesh may be saved for future reference. If a mesh already exists that is suitable for the linear run, the option to generate a linear run mesh should be turned off.
A set of standard buttons can be found at the bottom of the ''LTEA Tool'' dialog:
* Step 2 &ndash; Linear ADCIRC Run. In this step, the toolbox runs ADCIRC in linear mode with the M2 tidal constituent and performs an harmonic analysis on the result. If a run of ADCIRC and harmonic analysis has already been performed, the option to use existing solution data becomes available.  In this case the user must specify the datasets that contain the output of the harmonic analysis.  If this is not the initial pass through the mesh generation toolbox, or if the user wants to generate a "Size guideline function" from anaother source, it may be provided. If this is the case, the linear run as well as the next step "LTEA calculations" are bypassed.
*'''Help...''' &ndash; Opens [[SMS:LTEA]].
* Step 3 &ndash; LTEA Analysis. The LTEA algorithm processes the harmonic analysis output and determines the relative error due to node spacing throughout the domain.  It then computes a size guideline for generating a new  mesh.  The guideline is a dataset (a value for each node of the linear run mesh) named "DelX". The user must instruct LTEA to only perform calcualtions on the interior (no partial molecule) or to approximate the LTEA calculations right up to the boundary. (Note: extra controls exist in the dialog for tools that are under development.)
*'''< Previous''' &ndash; Returns to the previous step in the dialog.
* Step 4 &ndash; Generate Final Mesh. At this point, SMS has almost all the information required for mesh generation.  The user must specify the target size of desired mesh as a number of nodes and a tolerable deviation from that target.  The acceptable size transitions are also specified here (see the [[SMS:Smooth Dataset|Smooth Dataset article]] for a description of this).
*'''Continue >''' &ndash; Moves to next step of the dialog.
*'''Stop and Run''' &ndash; Closes the dialog and runs LTEA. The analysis generates several datasets used as size functions in the mesh generation process. Visible on all but the final page of the dialog.
*'''Run''' &ndash; Runs LTEA at the completion of all steps. Only visible on the ''Generate Final Mesh'' page of the dialog.
*'''Cancel''' &ndash; Closes the ''LTEA Tool'' dialog without saving any information entered.


The tool can be used repetitively to generate various meshes of the same area with varying resolution. In these cases, the first three steps should be bypassed by entering the input data in step 1 and the "DelX" function in step 3 and then proceeding to step 4.
The first page of the ''LTEA Tool'' dialog has the following options on the left:
*''Boundary'' &ndash; Select the desired coverage from the drop-down. There may be only one option in some cases.
*''Bathymetry'' &ndash; Clicking '''Select...''' brings up the ''Select Dataset'' dialog.
**{{anchor|select-dataset}}''Select Dataset'' dialog
***''Select'' section &ndash; Select the desired bathymetry dataset from the tree list.
***''Select time step'' section &ndash; After selecting the dataset, if the dataset has time steps, select the desired time step or turn on ''All time steps''.
***'''Help...''' &ndash; Opens [[SMS:Datasets]].
***'''Select''' &ndash; Closes the ''Select Dataset'' dialog and saves the selected dataset.
***'''Cancel''' &ndash; Closes the ''Select Dataset'' dialog without saving any selections.
*''Bathymetry'' &ndash; Clicking '''Select...''' brings up the ''Select Dataset'' dialog, where the desired mesh can be selected.


==LTEA Tool Overview==
On the right are the following options:
A set of standard buttons can be found at the bottom of the ''LTEA Toolbox''. They are as follows:
*''Provide harmonic solutions''
*'''Help...''' &ndash; launches the ''Help'' dialogue
**''Eta amplitude'' &ndash; Clicking '''Select...''' brings up the ''Select Dataset'' dialog, where the desired eta amplitude dataset can be selected.
*'''Continue >''' &ndash; Moves to next step of the ''LTEA Toolbox'' dialog.
**''Eta phase'' &ndash; Clicking '''Select...''' brings up the ''Select Dataset'' dialog, where the desired eta phase dataset can be selected.  
*'''< Previous''' &ndash; Allows returning to a an earlier step in the ''LTEA Toolbox'' dialog.
**''Velocity amplitude'' &ndash; Clicking '''Select...''' brings up the ''Select Dataset'' dialog, where the desired velocity amplitude dataset can be selected.  
*'''Stop and Run''' &ndash; causes SMS to close the toolbox and run the LTEA analysis. The analysis generates several datasets used as size functions in the mesh generation process.
**''Velocity phase'' &ndash; Clicking '''Select...''' brings up the ''Select Dataset'' dialog, where the desired velocity phase dataset can be selected.  
*'''Run''' &ndash; activates the model engine at the completion of all steps.
*''Provide Del X''
*'''Cancel''' &ndash; closes the ''LTEA Toolbox'' dialog without saving and information entered.
**''Del X'' &ndash; Clicking '''Select...''' brings up the ''Select Dataset'' dialog, where the desired Del X dataset can be selected.
===Step 1:Linear Rush Mesh===
[[File:LTEA1.jpg|thumb|325 px|Step 1:Linear Rush Mesh]]
*Boundary:
*Bathymeytry:
*Create Linear Run Mesh
<blockquote>
*Override Boundary Spacing
<blockquote>
*Coastline Spacing
*Deep Water Spacing
</blockquote></blockquote>
*Use Current Mesh
*Save Linear Run Mesh


===Step 2: IMS-ADCIRC Linear Run===
If the ''Provide harmonic solutions'' option is selected and '''Continue >''' is clicked, the [[#LTEA Tool → LTEA|''LTEA'' page]] of the dialog will come up. If ''Provide Del X'' is selected and '''Continue >''' is clicked, the [[#LTEA Tool → Generate Final Mesh|''Generate Final Mesh'' page]] of the dialog will come up.
[[File:LTEA2.jpg|thumb|325 px|Step 2:IMS-ADCIRC Linear Run]]
*Run IMS-ADCRIC Linear Run
<blockquote>
*Wave Continuity/Friction Coefficient:
*Minimum Angle for Tangential Flow:
*Absolute Convergence Criteria:
*Ramp Time
*Run Time:
*Time Step:
</blockquote>
*Provide Harmonic Solutions
<blockquote>
*Eta Ampitude:
*Eta Phase:
*Velocity Ampitude:
*Velocity Phase:
</blockquote>
*Provide DelX
<blockquote>
*DelX:
</blockquote>


===Step 3: LTEA Analysis===
===LTEA Tool → LTEA ===
[[File:LTEA3.jpg|thumb|325 px|Step 3: LTEA Analysis]]
[[File:LTEA Tool dialog Run Type page.png|thumb|right|450 px|The second page in the ''LTEA Tool'' dialog after selecting ''Provide harmonic solutions''.]]
*Run Type:
There are several options on the ''LTEA'' page of the ''LTEA Tool'' dialog. This page is reached after selecting ''Provide harmonic solutions'' on the first page.
*Value for dc:
*''LTEA'' section
*Minimum spacing from:
**''Run type'' drop-down &ndash; Select from the following options:
*Node Number:
***"LTEA" &ndash; Local Truncation Error Analysis
*Use Partial molecule
***"LTEACD" &ndash; Local Truncation Error Analysis with Complex Derivatives.
<blockquote>
**''Value for dx'' &ndash; Decimal value for dx.
*Molecule size:
**''Minimum spacing from'' &ndash; Normally grayed out.
</blockquote>
**''Node number'' &ndash; Normally grayed out.
**''Use partial molecule'' &ndash; Not available if "LTEACD" selected from ''Run type'' drop-down. If turned on, LTEA will give values for nodes with partial molecules. If turned off, LTEA will only give values for nodes completely within the domain.
**''Molecule size'' drop-down &ndash; Contains one or more possible molecule sizes.
***"9 x 9" &ndash; a small, equally-spaced grid of nine cells by nine cells is created around each node, and values from the ADCIRC solutions are interpolated for all 81 cells.


===Step 4:Generate Final Mesh===
===LTEA Tool → Generate Final Mesh===
[[File:LTEA4.jpg|thumb|325 px|Step 4:Generate Final Mesh]]
[[File:LTEA Tool dialog Generate Final Mesh.png|thumb|right|450 px|The third page in the ''LTEA Tool'' dialog after selecting ''Provide Del X''.]]
*Target number of nodes:
The ''Generate Final Mesh'' is reached by continuing after either selecting ''Provide Del X'' on the first page of the ''LTEA Tool'' dialog or by continuing after the ''LTEA'' page of the dialog. The options in the ''Generate Final Mesh'' section include:
*Element area change limit:
*''Target number of nodes'' &ndash; Fill in the target number of nodes (x) and a value for ''plus/minus'' the number of nodes (y). This gives a range of "x ± y" targeted nodes.
*Redistribute boundaries
*''Element area change limit'' &ndash; A decimal value for the element area change limit.
*Truncate element sizes
*''Redistribute boundaries'' &ndash; Turn on to redistribute boundaries.
<blockquote>
*''Truncate element sizes'' &ndash; Turn on to truncate element sizes according to the minimum and maximum specified.
*Minimum Size
**''Minimum size'' &ndash; Minimum element size in project units
*Maximum Size
**''Maximum size'' &ndash; Maximum element size in project units
</blockquote>


== Case Studies / Sample Problems ==
== Case Studies / Sample Problems ==
Line 91: Line 85:


* Models Section
* Models Section
<blockquote>
** ADCIRC LTEA &ndash; Uses LTEA to mesh Shinnecock bay and the area around it along Long Island, NY.
* ADCIRC LTEA &ndash; Uses LTEA to mesh Shinnecock bay and the area around it along Long Island, NY</blockquote>


=== American Samoa ===
=== American Samoa ===
The following images illustrate the results of the LTEA toolbox applied to a domain around American Samoa.  The first pair of images illustrate a mesh generated for the domain using the paving method.  Density at the coastline was controlled by redistributing the vertices on the arcs representing the coastline and the density varied to a larger ocean boundary density.  This mesh consists of 22,576 nodes (43,055 elements).  The other images illustrate the varying resolution generated by LTEA to result in constant error with target mesh sizes of 24,000 nodes and 12,000 nodes respectively.  The LTEA toolbox created meshes with 24,078 nodes (45,929 elements) and  12,029 nodes ( 22,543 elements).
The following images illustrate the results of the LTEA toolbox applied to a domain around American Samoa.  The first pair of images illustrate a mesh generated for the domain using the paving method.  Density at the coastline was controlled by redistributing the vertices on the arcs representing the coastline and the density varied to a larger ocean boundary density.  This mesh consists of 22,576 nodes (43,055 elements).  The other images illustrate the varying resolution generated by LTEA to result in constant error with target mesh sizes of 24,000 nodes and 12,000 nodes respectively.  The LTEA toolbox created meshes with 24,078 nodes (45,929 elements) and  12,029 nodes ( 22,543 elements).
{|
 
|-
<gallery widths="240px" heights="160px" perrow="5">
|[[Image:AmericanSamoaPaved.jpg|thumb|200px|Paved Mesh]]
Image:AmericanSamoaPaved.jpg|Paved Mesh
|[[Image:AmericanSamoaLT24K.jpg|thumb|200px|24000 Node Mesh]]
Image:AmericanSamoaLT24K.jpg|24000 Node Mesh
|[[Image:AmericanSamoaLT12K.jpg|thumb|200px|12000 Node Mesh]]
Image:AmericanSamoaLT12K.jpg|12000 Node Mesh
|-
Image:AmericanSamoaPaved_Zoom.jpg|Paved Mesh Detail
|[[Image:AmericanSamoaPaved_Zoom.jpg|thumb|200px|Paved Mesh Detail]]
Image:AmericanSamoaLT24K_Zoom.jpg|24000 Node Detail
|[[Image:AmericanSamoaLT24K_Zoom.jpg|thumb|200px|24000 Node Detail]]
Image:AmericanSamoaLT12K_Zoom.jpg|12000 Node Detail
|[[Image:AmericanSamoaLT12K_Zoom.jpg|thumb|200px|12000 Node Detail]]
</gallery>
|}


These images illustrate the redistribution of density to increase the density in areas that require additional detail for solution variations, or to reduce the number of nodes in the mesh.
These images illustrate the redistribution of density to increase the density in areas that require additional detail for solution variations, or to reduce the number of nodes in the mesh.
Line 111: Line 103:
=== Glacier Bay Alaska ===
=== Glacier Bay Alaska ===
The case of [http://water.engr.psu.edu/hill/research/glba/default.stm Glacier Bay Alaska], by [http://water.engr.psu.edu/hill/default.stm Dave F. Hill's] research group, poses another problem for the LTEA toolbox. This case includes two ocean boundaries.  The figures below show three meshes generated for this case and illustrate the large variation in node density that can be produced by the procedure.
The case of [http://water.engr.psu.edu/hill/research/glba/default.stm Glacier Bay Alaska], by [http://water.engr.psu.edu/hill/default.stm Dave F. Hill's] research group, poses another problem for the LTEA toolbox. This case includes two ocean boundaries.  The figures below show three meshes generated for this case and illustrate the large variation in node density that can be produced by the procedure.
{|
<gallery widths="260px" heights="260px">
|-
Image:GlacierBayImage.jpg|Glacier Bay Domain over areal photo
|[[Image:GlacierBayImage.jpg|thumb|200px|Glacier Bay Domain over areal photo]]
Image:GlacierBayConceptual.jpg|Glacier Bay Domain with second ocean boundary highlighted
|[[Image:GlacierBayConceptual.jpg|thumb|200px|Glacier Bay Domain with second ocean boundary highlighted]]
</gallery>
|}
This case includes two ocean boundaries.  Currently, the LTEA toolbox makes a sometimes erroneous assumption that only one ocean boundary exists.  To work around this problem in the current version of SMS, the following steps are required:
This case includes two ocean boundaries.  Currently, the LTEA toolbox makes a sometimes erroneous assumption that only one ocean boundary exists.  To work around this problem in the current version of SMS, the following steps are required:
* Change the inland ocean boundary to land
* Change the inland ocean boundary to land
Line 122: Line 113:
|-
|-
|[[Image:GlacierBayLiinear.jpg|thumb|200px|Linear mesh for Glacier Bay (17,717 nodes)]]
|[[Image:GlacierBayLiinear.jpg|thumb|200px|Linear mesh for Glacier Bay (17,717 nodes)]]
|[[Image:LTEA_Harmonics.jpg|thumb|250px|Harmonic datasets for LTEA analysis]]
|valign="top"|[[Image:LTEA_Harmonics.png|thumb|250px|Harmonic datasets for LTEA analysis]]
|}
|}
* Outside of the toolbox, change the second ocean boundary to ocean on the linear run mesh and run a linear run of ADCIRC with harmonic analysis turned on. This will generate the datasets for LTEA calcuations.
* Outside of the toolbox, change the second ocean boundary to ocean on the linear run mesh and run a linear run of ADCIRC with harmonic analysis turned on. This will generate the datasets for LTEA calcuations.
* Relaunch the toolbox and select the datasets from the linear run to guide the mesh generation process.
* Relaunch the toolbox and select the datasets from the linear run to guide the mesh generation process.


{|
<gallery widths="260px" heights="240px" perrow="5">
|-
Image:GlacierBay10K.jpg|20000 Node Mesh (19,929 nodes)
|[[Image:GlacierBay10K.jpg|thumb|250px|20000 Node Mesh (19,929 nodes)]]
Image:GlacierBay20K.jpg|20000 Node Mesh (30,227 nodes)
|[[Image:GlacierBay20K.jpg|thumb|250px|20000 Node Mesh (30,227 nodes)]]
Image:GlacierBay30K.jpg|30000 Node Mesh (10,072 nodes)
|[[Image:GlacierBay30K.jpg|thumb|250px|30000 Node Mesh (10,072 nodes)]]
</gallery>
|}


== Related Topics ==
== Related Topics ==
* [[SMS:ADCIRC|ADCIRC]]
* [[SMS:ADCIRC|ADCIRC]]
* [[SMS:Steering|Steering]]
* [[SMS:Steering|Steering]]
* [[ADCIRC LTEA Workflow|ADCIRC LTEA Workflow]]


== External Links ==
== Additional Reading ==
* [http://champs.cecs.ucf.edu/ Coastal Hydroscience Analysis, Modeling & Predictive Simulations Laboratory (CHAMPS Lab)]
* [http://champs.cecs.ucf.edu/ Coastal Hydroscience Analysis, Modeling & Predictive Simulations Laboratory (CHAMPS Lab)]
* [http://contentdm.lib.byu.edu/ETD/image/etd1550.pdf Dec 2006 Automatic, unstructured mesh generation for 2D, shelf-based tidal models]
* [http://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=1780&context=etd Sep 2006 Automatic, unstructured mesh generation for 2D, shelf-based tidal models]
* [http://champs.cecs.ucf.edu/Publications/Refereed/IJCFD_Hagen_et_al_2006.pdf Sep 2006 Automatic, unstructured mesh generation for tidal calculations in a large domain]
* [http://champs.cecs.ucf.edu/Publications/Refereed/IJCFD_Hagen_et_al_2006.pdf Sep 2006 Automatic, unstructured mesh generation for tidal calculations in a large domain]
* [http://poc.omp.obs-mip.fr/DOCUMENTS/t-ugo/res.pdf Sep 2006 Resolution Issues in Numerical Models of Oceanic and Coastal Circulation]
* [http://poc.omp.obs-mip.fr/DOCUMENTS/t-ugo/res.pdf Sep 2006 Resolution Issues in Numerical Models of Oceanic and Coastal Circulation]
* [http://www.nd.edu/~adcirc/pubs/IJNMF-hwkh-2001-PUBL.pdf 2001 Two-dimensional, unstructured mesh generation for tidal models]
* [http://www.nd.edu/~adcirc/pubs/IJNMF-hwkh-2001-PUBL.pdf 2001 Two-dimensional, unstructured mesh generation for tidal models]
* [http://www.nd.edu/~adcirc/pubs/ijnmf-hwk-2000-PUBL.pdf 2000 One-dimensional finite element grids based on a localized truncation error analysis]
* [http://www.nd.edu/~adcirc/pubs/ijnmf-hwk-2000-PUBL.pdf 2000 One-dimensional finite element grids based on a localized truncation error analysis]
* [http://kfki.baw.de/conferences/ICHE/1998-Cottbus/45.pdf 1998 2D Finite Element Grids Based on a Localized Truncation Error Analysis]
* [http://water.engr.psu.edu/hill/research/glba/default.stm Glacier Bay Test Case by Dave F. Hill]
* [http://water.engr.psu.edu/hill/research/glba/default.stm Glacier Bay Test Case by Dave F. Hill]


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[[Category:ADCIRC|L]]
[[Category:ADCIRC|L]]
[[Category:External Links]]
[[Category:External Links]]
[[Category:Needs Update]] <!--Need clarification on steps-->

Latest revision as of 18:50, 24 March 2023

Linear Truncation Error Analysis (LTEA) Toolbox incorporated into SMS uses the LTEA algorithm as the heart of a utility which creates finite element meshes of varying resolution for ADCIRC analysis. The algorithm was initially presented by Dr. Scott C. Hagen as part of his doctoral research at Notre Dame, and development has continued on the methodology at the University of Central Florida. It performs analysis on an existing ADCIRC mesh and its solution to help quantify the error associated with the mesh.

Normally, this ADCIRC solution is taken from a "linear ADCIRC" run. This type of run is used to make the process faster and to simplify the LTEA algorithm applied to the unstructured mesh. A second phase of the LTEA process uses the error values at each node to create a relative size function covering the domain called "Del X". This refines the mesh where the element error values would be greatest such as near shorelines or around islands.

Mesh Generation Toolbox Dialog

Mesh Generation Toolbox dialog

SMS includes a graphical interface that allows using the LTEA algorithm to guide the generation of a finite element mesh. Before using the tool, ADCIRC must be run in order to generate the datasets necessary for LTEA to run.

The tool requires the following inputs to be in the Project Explorer:

  • A bathymetry scatter set.
  • A 2D mesh.
  • A mesh generation coverage having at least one polygon.

The following may be required, depending on the options selected:

  • Harmonic ADCIRC solution dataset(s)

The toolbox is accessed by:

  1. Right-clicking on the mesh generation coverage and selecting Mesh Generation Toolbox... to bring up the Mesh Generation Toolbox dialog.
  2. Select "Localized Truncation Error Analysis (LTEA)" from the list and click Run to bring up the LTEA Tool dialog.

The LTEA Tool dialog is discussed in the next section.

LTEA Tool Dialog

The first page in the LTEA Tool dialog.

A set of standard buttons can be found at the bottom of the LTEA Tool dialog:

  • Help... – Opens SMS:LTEA.
  • < Previous – Returns to the previous step in the dialog.
  • Continue > – Moves to next step of the dialog.
  • Stop and Run – Closes the dialog and runs LTEA. The analysis generates several datasets used as size functions in the mesh generation process. Visible on all but the final page of the dialog.
  • Run – Runs LTEA at the completion of all steps. Only visible on the Generate Final Mesh page of the dialog.
  • Cancel – Closes the LTEA Tool dialog without saving any information entered.

The first page of the LTEA Tool dialog has the following options on the left:

  • Boundary – Select the desired coverage from the drop-down. There may be only one option in some cases.
  • Bathymetry – Clicking Select... brings up the Select Dataset dialog.
    • Select Dataset dialog
      • Select section – Select the desired bathymetry dataset from the tree list.
      • Select time step section – After selecting the dataset, if the dataset has time steps, select the desired time step or turn on All time steps.
      • Help... – Opens SMS:Datasets.
      • Select – Closes the Select Dataset dialog and saves the selected dataset.
      • Cancel – Closes the Select Dataset dialog without saving any selections.
  • Bathymetry – Clicking Select... brings up the Select Dataset dialog, where the desired mesh can be selected.

On the right are the following options:

  • Provide harmonic solutions
    • Eta amplitude – Clicking Select... brings up the Select Dataset dialog, where the desired eta amplitude dataset can be selected.
    • Eta phase – Clicking Select... brings up the Select Dataset dialog, where the desired eta phase dataset can be selected.
    • Velocity amplitude – Clicking Select... brings up the Select Dataset dialog, where the desired velocity amplitude dataset can be selected.
    • Velocity phase – Clicking Select... brings up the Select Dataset dialog, where the desired velocity phase dataset can be selected.
  • Provide Del X
    • Del X – Clicking Select... brings up the Select Dataset dialog, where the desired Del X dataset can be selected.

If the Provide harmonic solutions option is selected and Continue > is clicked, the LTEA page of the dialog will come up. If Provide Del X is selected and Continue > is clicked, the Generate Final Mesh page of the dialog will come up.

LTEA Tool → LTEA

The second page in the LTEA Tool dialog after selecting Provide harmonic solutions.

There are several options on the LTEA page of the LTEA Tool dialog. This page is reached after selecting Provide harmonic solutions on the first page.

  • LTEA section
    • Run type drop-down – Select from the following options:
      • "LTEA" – Local Truncation Error Analysis
      • "LTEACD" – Local Truncation Error Analysis with Complex Derivatives.
    • Value for dx – Decimal value for dx.
    • Minimum spacing from – Normally grayed out.
    • Node number – Normally grayed out.
    • Use partial molecule – Not available if "LTEACD" selected from Run type drop-down. If turned on, LTEA will give values for nodes with partial molecules. If turned off, LTEA will only give values for nodes completely within the domain.
    • Molecule size drop-down – Contains one or more possible molecule sizes.
      • "9 x 9" – a small, equally-spaced grid of nine cells by nine cells is created around each node, and values from the ADCIRC solutions are interpolated for all 81 cells.

LTEA Tool → Generate Final Mesh

The third page in the LTEA Tool dialog after selecting Provide Del X.

The Generate Final Mesh is reached by continuing after either selecting Provide Del X on the first page of the LTEA Tool dialog or by continuing after the LTEA page of the dialog. The options in the Generate Final Mesh section include:

  • Target number of nodes – Fill in the target number of nodes (x) and a value for plus/minus the number of nodes (y). This gives a range of "x ± y" targeted nodes.
  • Element area change limit – A decimal value for the element area change limit.
  • Redistribute boundaries – Turn on to redistribute boundaries.
  • Truncate element sizes – Turn on to truncate element sizes according to the minimum and maximum specified.
    • Minimum size – Minimum element size in project units
    • Maximum size – Maximum element size in project units

Case Studies / Sample Problems

Tutorials

The following tutorials may be helpful for learning to use LTEA in SMS:

  • Models Section
    • ADCIRC LTEA – Uses LTEA to mesh Shinnecock bay and the area around it along Long Island, NY.

American Samoa

The following images illustrate the results of the LTEA toolbox applied to a domain around American Samoa. The first pair of images illustrate a mesh generated for the domain using the paving method. Density at the coastline was controlled by redistributing the vertices on the arcs representing the coastline and the density varied to a larger ocean boundary density. This mesh consists of 22,576 nodes (43,055 elements). The other images illustrate the varying resolution generated by LTEA to result in constant error with target mesh sizes of 24,000 nodes and 12,000 nodes respectively. The LTEA toolbox created meshes with 24,078 nodes (45,929 elements) and 12,029 nodes ( 22,543 elements).

These images illustrate the redistribution of density to increase the density in areas that require additional detail for solution variations, or to reduce the number of nodes in the mesh.

Glacier Bay Alaska

The case of Glacier Bay Alaska, by Dave F. Hill's research group, poses another problem for the LTEA toolbox. This case includes two ocean boundaries. The figures below show three meshes generated for this case and illustrate the large variation in node density that can be produced by the procedure.

This case includes two ocean boundaries. Currently, the LTEA toolbox makes a sometimes erroneous assumption that only one ocean boundary exists. To work around this problem in the current version of SMS, the following steps are required:

  • Change the inland ocean boundary to land
  • Run the first step of the LTEA toolbox to generate the "Linear Run Mesh" and then "Stop and Run" to that point.
Linear mesh for Glacier Bay (17,717 nodes)
Harmonic datasets for LTEA analysis
  • Outside of the toolbox, change the second ocean boundary to ocean on the linear run mesh and run a linear run of ADCIRC with harmonic analysis turned on. This will generate the datasets for LTEA calcuations.
  • Relaunch the toolbox and select the datasets from the linear run to guide the mesh generation process.

Related Topics

Additional Reading