FAQ   

Frequently Asked Questions

Pre-purchase questions

Q:  Do I need to download each module after purchase?
A:  No, the modules are included in the CCHE-GUI+Mesh download and are activated by entering your license key.  There is no need to download anything else.

Q:  Is there any documentation?
A:  Yes, electronic versions of documentation and user manuals are included in the CCHE-GUI+Mesh installation.  In addition, a Quick Start Guide is included which provides step-by-step instructions with example applications in order to help beginners master the use of the CCHE software.  It is recommended that beginners go through the Quick Start Guide before applying CCHE models to real problems.

General questions

Q:  How do I specify initial conditions for the CCHE2D model?
A: 

• Select a variable (e.g., Initial Water Surface) from “Variable View”.
• Select the button with the icon of a rectangle and a plus sign on the “Simulation” toolbar.
• Select two different mesh nodes in the domain to define an area.
• In the dialog window, specify a value and click OK. This value will be assigned to the above selected area.
• Repeat the above process until all of the initial conditions are specified for the entire domain.

Q:  When using the CCHE2D model, the flow simulation doesn’t run or doesn’t give good results or crashes.

A:

• Check to see if the initial boundary conditions, especially the “Initial Water Surface”, were correctly set.
• Check to see if there are too many dry nodes in the domain at the beginning. If so, try to specify a higher initial water surface to reduce the number of dry nodes.
• Check to see if the time step is too big. You may go to “Set Flow Parameters…” in the “Simulation” menu in order to reduce the time step.
• Check to see if the mesh is too coarse. If so, you may need to use the Mesh Editing Tool to refine the mesh locally or use CCHE-Mesh to generate a finer mesh.
   

Q:  When using the CCHE2D model, the sediment transport simulation doesn’t run or doesn’t give good results or crashes.
A:  For sediment parameters:

• Check to see if the sediment “Size Classes” are defined.
• Check to see if the “Number of Bed Layers” is equal to or greater than 3.
• Check to see if the “Bed Samples” are defined.
• Check to see if the sediment “Boundary Condition Files” are prepared.
• Check to see if the sediment “Transport Mode” is selected.
• Check to see if the “Adaptation Length for Bedload” and the “Adaptation Factor for Suspended load” are correctly set.

  For sediment initial conditions:

• Check to see if the Layer Thickness is correctly set for EACH layer. Usually for the first layer, the thickness is 1~2 times that of the D50.
• Check to see if the Layer Sample is set for EACH layer.

  For sediment boundary conditions, check to see if it is attached to the desired flow inlet. If not, select the desired inlet, select “Import SBC File” and/or “Import BBC File” to attach the prepared sediment boundary condition files.

  The sediment transport simulation is based on an existing flow result.  If this flow result is not good enough, it will definitely affect the sediment transport simulation.
 

Q:  How do I convert from a raster to a “DEM” format for CCHE1D model?
A:

• Open ArcMap 9.x.
• Display "ArcToolbox" in your ArcMap window. "ArcToolbox" can be found in the ArcMap menu bar; its icon looks like a red box.
• Expanding "Conversion Tools" under the "ArcToolBox" list, you will find the "From Raster" toolbox. Under this toolbox, you can see "Raster to ASCII" tool.
• Double Click the "Raster to ASCII" Tool. Browse the input raster file you want to convert at the "Input Raster" dialog window and enter a name for the "Output ASCII raster file".  The generated ASCII file is a "DEM" file that CCHE1D can load as a "Grass ASCII file".

Q:   How do I get to the related documents (Users’ Manual, Technical Report, etc.)?
A:   Typically, all related documentation will be included in the Installer (Setup file) for the application.  After installing the CCHE-GUI, CCHE-MESH or CCHE1D software package onto your computer, you can go to the corresponding “Group” by selecting Start-> All Programs. All of the documents can be found in the “Documents” menu.
 

Q:  How do I export or convert results from the CCHE2D program?
A:

• The CCHE-GUI program can export results into a bitmap image.
• It can export into Shape files.
• It can export into TIFF image file.
• The CCHE-GUI program can export and convert the selected results into a text file which can be opened by any text editor. By adding the appropriate header, it can easily be imported by Tecplot. This function can be accessed when viewing the results in a Table (The fourth button in the middle toolbar).
• The CCHE-GUI program can export results from the selected I or J line, or extract results from a predefined polyline into a text file when using the Data Probe tool.
• The CCHE-GUI program can export a selected Frame from History results into an ASCII file when viewing the history results using the History File Editor.
• The CCHE-GUI program can generate animations from the History results by using the History File Editor.
• Other than the above exceptions, the CCHE-GUI program cannot convert results into other file formats, e.g., ArcGIS formats, etc.