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Posts posted by yao

  1. The residual ratios used by AcuSolve are a non-dimensional measure of how "out-of-balance" the governing equations are. The residual ratios are recomputed at each timestep to give an indication of how well the solution is converging.

    The solution ratio that is computed by AcuSolve represents the ratio of the change in the solution between timesteps to the solution at the previous timestep. This value indicates the level of unsteadiness present in the solution.

    Note that the solution ratios and residual ratios are computed using the contribution of each node in the model. The single value is obtained by taking the appropriate norm of the contribution from each node. The details of this procedure are described in the attached document.


  2. AcuSolve uses the Finite Element Method to discretize the governing equations. By default, AcuSolve uses linear shape functions and Gaussian quadrature to perform the necessary integrations. This results in a numerical method that is second order accurate in space. Although there is no direct comparison to the common diferencing schemes found when using the finite volume method, this approach most resembles central differencing with a small amount of upwinding blended locally when necessary for stability. There is no way to reduce the spatial accuracy of AcuSolve below second order, however, quadratic tetrahedra elements are supported to increase the spatial accuracy above second order.


  3. If User's are unable to open a database or if it gives an error like "Unable to create path Marker" then we can say that the database is corrupted. In such cases the data from this corrupted database can be extracted by following the below steps,

    1. Install HDFview on the machine (http://www.hdfgroup.org/hdf-java-html/hdfview/)
    2. Open HDFview GUI
    3. Load the database by clicking on File > Open in the menu bar and navigating to the database location. Select the database and click Open
    4. All the data in the database will be displayed in hierarchical format
    5. Click on first item in the tree, press Shift and select the last item. All the items in the tree will be selected
    6. Right click and select Copy
    7. Click on File > New > HDF5
    8. Provide a filename (eg: test.acs) and save the database
    9. Scroll down to the bottom to see the new database created (test.acs.h5)
    10. Right-click on the new database and select Paste. Click Yes to copy the selected objects
    11. You can see all the objects under the new database
    12. Save the database. File > Save, then close the HDFview GUI by clicking on File > Exit
    13. Rename the new database (eg: test.acs.h5 to test.acs)
    14. Load the new database into AcuConsole


  4. If you see an error message such as, "Can't set up a valid OpenGL canvas," "something is seriously wrong with the system!". It might be that you are using VNC for remote display. Unfortunately, OpenGL does not work over VNC, but TurboVNC based on VirtualGL should do the job. Check the following link for more information, https://mailman.coin3d.org/pipermail/coin-discuss/2006-June/006979.html


  5. AcuConsole uses Coin3D for visualization. Coin3D ( http://www.coin3d.org )requires OpenGL. There are multiple sources of problems with display. 1. OpenGL is not installed on your machine. Try running "glxgears" application as a test. 2. The graphics driver used. On Linux try running /sbin/lspci to see the drivers for your video controller. 3. On Linux, check the following files ( mail it to our support ), /etc/X11/XF86Config and /usr/X11R6/lib/X11/Cards


  6. This issue is caused by SELinux. At the current time, the only way to work around this issue is to turn off SELinux. This typically needs to be deactivated by the root user. Using the GNOME desktop environment, this can be done by running system-config-securitylevel and selecting the "SELinux" tab. Disable SELinux and apply the settings.


  7. AcuFieldView requires libstdc++.so.5. This library is present on most Linux systems as part of the GNU C compiler collection. However, newer Linux kernels are updating to libstdc++.so.6, which is not compatible with AcuFieldView. To resolve this issue, users need to install the libstdc++.so.5 library. This can typically be found using the package manager, or by doing a google search for libstdc++ and the name of your Linux flavor/version. These libraries can be downloaded from the various repositories on the web. 

    For 64 bit SuSe Linux, the package may be obtained from the following link: 

    For Ubuntu and other Debian systems, the following link can be used to search for "libstdc++.so.5" in the "Search the contents of packages" field: 

    A direct link to the debian package download is shown below (contained in the most recent debian version as of the date this is being posted): 


  8. AcuFieldview supports client-server operation which allows users to process their data in its original location (i.e. on a compute cluster) while viewing it on their local desktop system. Client-server is supported across platforms (i.e. Windows clients, Linux Servers) and is the fastest and most efficient method of viewing large datasets that reside on remote platforms. 

    Using AcuFieldview in client-server mode requires a few simple set up steps. These steps are outlined in detail in the FV Reference Manual in Chapter 3 under the "Client-Server Mode" subsection. The FV Reference Manual can be accessed on Windows by selecting Help--->Contents-->Reference Manual. On Linux, the manual can be found in the AcuSolve installation directory under the fv/doc subdirectory.


  9. By default when acuFieldView (or FieldView) is launched it tries to make a connection for client/server behavior. The default client port number that is used is 12345. If something else is using that port number, then you will see that error.

    Let's assume that on a Linux system, AcuSolve is installed in /home/Acusim/LINUX64/V1.7f/... There are two ways around this - both involving settings in one of the Acusim.cnf files.

    1. This will disable client/server mode for acuFieldView: 
    acufieldview_executable = /home/Acusim/LINUX64/V1.7f/bin/acuFv -port none

    2. This will use a different port number from the default: 
    acufieldview_executable = /home/Acusim/LINUX64/V1.7f/bin/acuFv -port 12344 
    NOTE - It is good if each user uses a different port number if they are all working on the same machine.

    You can see the default setting for acufieldview_executable via 
    'acuConsole -h'

    It is also possible that a firewall is blocking access to that default port 12345.


  10. This date says the license manager is reading your license.dat but can't find a valid license key. Check that there are no spurious characters in the license.dat file.

    If on LINUX try

    dos2unix license.dat

    If on Windows edit the license.dat deleting all text but the license feature lines (comment lines start with #). A sample license feature line looks like:

    yCTxePXm3CPElP5oe6bIya AcuConsole 1 0 Dec-31-2010 0xa3be71g5 host1


  11. "OpenSCManager failed: Access Denied" 
    "rexed.exe: can't establish connection"

    This error is related to the permissions associated with the UAC (User Access Control) feature in Windows Vista or 7. Even when users are logged in as Administrator, you don't have administrative privilege by default unless you specifically request it for a given program. To resolve this problem, right click on acuLmd.exe in the "bin" folder of the AcuSolve installation and select "Run as administrator".



    This type of output is a simple average. The value that is printed in the output file is computed as follows:UTimeAve = sum( U_n )/n, where n = the step number. The reset_frequency tells AcuSolve to start the time averaging procedure over by deleting the previous time averaged field, setting n=0, then starting the process out with a fresh set of values. Note that these values are not carried forward across restarts. So, every time you restart AcuSolve, the time average output is reinitialized. 


    This type of output uses a weighted average to compute the output value. This is useful for cases where you may want to weight the initial time steps less as the flow field is developing. The value that is printed in the output file is computed as follows: URunAve = 1/N*U_n + (1-1/N)*URunAve_n-1. Where N = min(step,N_max), step= the current time step number, and N_max=running_average_steps. The running_average_steps parameter is set in the EQUATION command. So, setting the running_average_steps essentially defines an averaging "window" over which to compute the output. This value is carried forward across restarts, and may also be initialized using the NODAL_INITIAL_CONDITION command. Note that TIME_AVERAGE_OUTPUT is simply an output quantity, whereas the RUNNING_AVERAGE_OUTPUT field is used in other areas internal to AcuSolve such as the non-reflecting boundary conditions, and running_average_wall_function. 

    Both types of output can be visualized using Fieldview, Ensight, and Paraview. They are included in the extended output variables when using acuTrans to convert nodal output. Here is an example: 

    acuTrans -out -to fieldview -extout 

    If either TIME_AVERAGE_OUTPUT or RUNNING_AVERAGE_OUTPUT are defined, their variables will be written into the output file.


  13. The Lighthill stress tensor is constructed by taking derivatives of the velocity field. It is possible to build all terms of the Lighthill stress tensor within a post processing package (Fieldview, Ensight, or Paraview) by using the function calculator. To make this calculation efficient, it is suggested that the -extout flag is used on acuTrans when converting the solution to the post-processor format. This writes the velocity gradients to the file. The velocity gradients can then be assembled appropriately in the post processing package to form the Lighthill stress tensor without havin to compute each derivative in the post processor. The divergence of the Lighthill stress tensor is typically used for visualizing the acoustic source strength. Creating and animating isosurfaces of divT can provide insight into the acoustic source characteristics.


  14. The AcuSolve direct reader for ParaView functions as a plug-in. So, if you intend to use the version ofParaView available on the Kitware webpage, you will need to download and install the plug-in reader. The most recent version of ParaView can be retrieved from the following link: 


    The AcuSolve direct reader plug-in can be be downloaded from this link: 


    Once you have installed Paraview, unpack the plug-in and follow these instructions: 

    On Windows platforms: 
    Place the AcuSolveReader.dll file into the /bin/plugins folder of the ParaView installation 

    On Linux platforms: 
    Place the file called libAcuSolveReader.so into the lib/paraview-3.6/plugins directory. Note that you may need to create this directory.


  15. We typically suggest to use temperature_flow if the properties are strongly dependent on temperature. Treating flow and temperature as one large matrix can aid convergence in these cases. The degree to which it aids convergence will be extremely problem dependent, so it is difficult to make a blanket statement. If the free convection is dominant, temp-flow would have more effect than if the forced convection is dominant.

    If the flow equations don't depend on temperature, solving them separately will be faster.


  16. The relaxation_factor parameter is available through the AUTO_SOLUTION_STRATEGY command. By default the relaxation factor is 0 (i.e. no relaxation). When relaxation_factor is set to a non-zero value, a number of changes to the solution strategy are made. These changes are primarily made through the LINEAR_SOLVER_PARAMETERS command. It should be noted that these changes typically cause slower non-linear convergence for steady state cases, so relaxation should only be used for cases that are very stiff or difficult to converge. Also, the relaxation factor should always be set to 0 for transient simulations. When relaxation is used, AcuSolve adjusts the number of projection vectors, the regularization factor, and the update factor that is used for each equation. These parameters are automatically adjusted when relaxation is used through the AUTO_SOLUTION_STRATEGY command. This ensures that suitable values are set for each parameter. Although it is not recommended, users can manually adjust the various parameters (i.e. update factor, regularization, number of projection vector) through the LINEAR_SOLVER_PARAMETERS command.


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