Alta Dynamics Knowledge Center - New pages [en]

Installation

2015-10-21T21:54:45Z

Altadyna:

The installation process is composed of two major steps: 1. Installing Alta License Service; 2. Installing Polaris CFD

Both Windows and Linux are supported. However both systems must be 64 bit. Mac OS is not supported at this moment.

On Windows users shall first install "Microsoft Visual C++ 2008 SP1 Redistributable Package (x64)". It can be downloaded from Microsoft directly, or from Alta Dynamics. In some cases users may have already installed it due to prior installation of other software.

=Installing Alta License Service=

The Alta License Service is a software that manages the Polaris CFD software's license usage. It must be running with proper licenses in order for Polaris CFD software to function properly. Alta License Service is relatively small and it does not require much resources to run. It can be installed on a low end computer, or on a computer that runs the actual CFD. A computer running the license service is called the license server.

On Windows, run the installer to install the software. On Linux simply untar the file. Read the PDF manual in the doc folder to configure your license server.

==Testing your license==

Download a free license file from Alta Dynamics. Follow the manual to complete the license server setup. If you obtained another license file from Alta Dynamics you can test it as well.

=Installing Polaris CFD=

==On Windows==
First install MsMpi software that can be download from Alta Dynamics. To avoid version mismatch please do not download this software from Microsoft's website. During the installation process accept the default location for this installation, which is "C:\Program Files\". If it's different you will need to edit the script "bin\polaris_solver.bat" to reflect the correct path for MS MPI, after Polaris CFD is installed.

Run the Polaris CFD software installer as administrator. Follow the prompts to complete the installation. This should be a straight forward process.

==On Linux==
Simply copy the Polaris_*.tar.gz file to your intended installation location, run "tar xzf Polaris_*.tar.gz" to untar the file. You're done.

==Configuring your license server==

Before running the Polaris CFD software, you should have a copy of the "Server certificate" file that was generated by the license server. This certificate file will enable the computer running Polaris CFD to connect the license server. The license server's port number shall be obtained as well.

For the viewer, click on menu "File->Licening", the licensing dialog shows up. Click on "Network", then enter "Server name/ip". Next click on "Server certificate" button to select the file. Enter the port number if it's not 1024.

[[File:Licensing_dialog.png|600px]]

After entering above information, click on "Query". Some text message will be shown. If no error is shown, you're done! Congratulations!

You only need to configure this dialog once on a computer.

For the Polaris CFD solver to communicate with the license server, the same information shall be provided. Edit the file "res/a_config.xml" to enter the same information.

<license_server
name_or_ip = "localhost"
port_number = "1024"
certificate_file = "/opt/share/Lantern/lic_dir/key/server.crt"
/>

=Configuring MPI=
On Linux, Polaris CFD is packed with openmpi. Users do not need to install MPI separately. However in order to run the Polaris CFD solver on a parallel cluster, MPI must be configured properly between all nodes. Please contact your system administrator if you do not know this. You can also contact Alta Dynamics for support.

[[Category:Installation]]

Common Filters

2015-07-26T12:42:52Z

Altadyna:

This page introduces some of the commonly used filters. Click on menu "PostProcessing->Data Analysis" to see a list of such filters. All filters are under the "Filters" menu.

[[Category:Data operations]]

Viewing an object

2015-07-25T19:18:06Z

Altadyna:

This page illustrates how to view an object in Polaris Viewer. An object can be a geometry object such as a sphere or an airplane, or a data object such as the fluid flow results. It can also be other objects such as a data table. In this page a geometry object is used to explain some of the major functions in Polaris Viewer.

In Polaris Viewer, click on menu "Setup->Create->Airfoil", then click on "Apply" in the "Properties" panel. An airfoil object is seen below. If the "BC" panel is seen on the right side, one can close it since it is not related to this topic.

[[File:Viewer airfoil 01.png|600px]]

Drag the object in the viewer to rotate it. Then click on the "Information" panel. The "Data Hierarchy" shows this is a "Mulit-block Dataset" and there are four strings under it. Each block in this case is a collection of facets and it is called a face in Polaris. This airfoil has four faces that we will explore later. The "Information" panel also shows the number of cells (facets) and points (vertices) of this object. The X Y Z bounds of the object are also shown.

The "Data Arrays" and "Time" information is empty because this object does not contain such information.

[[File:Viewer airfoil 02.png|600px]]

Next click on the "Display" panel and set the "Representation" style to "Surface With Edges". This can also be set in the toolbar below the main menu (see the mouse pointer in the figure below).

[[File:Viewer airfoil 03.png|600px]]

Users can easily inspect the surface normals by setting the object colored by "cellNormals", and picking a normal component, e.g. Y. The color legend can be toggled to be visible as seen in the figure below.

[[File:Viewer airfoil 04.png|600px]]

Now set the representation style back to "Surface" and the color to "Solid Color". Click on menu "View->Selection Inspector". The "Selection Inspector" panel is shown. Click on "Create Selection" near the top and set the "Selection Type" to "Blocks". The four blocks (faces) are seen in the list of blocks. Click on any of them to see the block/face to be highlighted in the view area.

[[File:Viewer airfoil 05.png|600px]]

[[Category:Viewer]]

Geometry BC

2015-07-25T14:44:19Z

Altadyna: Altadyna moved page Geometry BC to Geometry Usage

A geometry is not used if no usage (boundary condition, initial condition, VR) is assigned to it, even though it is shown in the viewer. When applying boundary conditions it makes no difference if the geometry is created internally or imported from different formats.

Saving a project will bring up the "BC" panel. User can also manually display/hide this panel. The "BC" panel is dockable. It is placed at the right side of the main window in the figure below.

[[File:Setup bc panel.png|600px]]

By default a geometry is not used. User can click on "Fluid", "Solid" or "Measurement" to use the region for that purpose. If a geometry is "Fluid", a fluid material and initial condition must be assigned. Same requirement will apply to solid regions when solid/fluid coupling analysis is enabled.

If a geometry is "Solid" the wall type must be specified as either "Regular" or "Frictionless". A face boundary condition can be assigned to the entire geometry. If the geometry is moving or rotating, "Moving" must be check and one of the defined motions must be selected. Inverted solid refers to a solid that inverts its fluid and solid volumes. This means inside the solid is fluid and outside is solid. This can be used for internal flow simulations such as nozzles.

The "VR" checkbox can be used for any geometries. If a VR level is assigned to a solid geometry/region, only the voxels intersecting its surface will be refined to the designated refinement level. For other regions all voxels contained inside the region will be flagged for refinement.

On the bottom of the "BC" panel is a table listing the faces of the geometry. A face is a collection of facets, usually connected facets. One or several faces form a enclosed geometry. All faces will inherit the boundary conditions defined on the region. However each face can have its own boundary conditions. Double click the face in the table and a dialog will pop up for assigning/modifying face usage.

[[File:Setup face bc.png|500px]]

[[Category:Geometries]]

Import geometries

2015-07-25T11:29:54Z

Altadyna:

Polaris CFD can import a variety of external geometries that are generated by other software. Here is the list of supported formats:
# Nastran (.nas) mesh format
# STL (.stl) mesh format
# STEP (.stp .step) CAD format
# IGS (.igs .iges) CAD format
# ply mesh format
# off mesh format
# vtk mesh format
# Airfoil profile (.dat) from UIUC Airfoid Database

[[File:Setup import.png|600px]]

When "Check geometry" is checked the imported geometry will go through a quick check for integrity. If a problem is detected it will be reported on a dialog. User shall inspect the geometry, fix the problem and reimport it. Surface normal must point away from the volume. It the imported geometry has wrong normals, user can click on "Flip normal". The transformation matrix on the "Properties" panel is the same as seen at other places.

When a STEP or IGS CAD file is imported, Polaris Viewer will automatically tessellate the surfaces. The meshed surface will be shown in the viewer.

[[Category:Geometries]]

Internal geometries

2015-07-25T11:29:30Z

Altadyna: /* Triad Axes */

Polaris CFD can create several kinds of geometries internally. These geometries are relatively simple in shape, but common to many analyses. This feature is very handy for many users.

Click on menu "Setup->Create" to see a list of geometries that can be created.

=Airfoil=
The airfoil created by Polaris CFD is based on NACA 4-digit designation. It is extruded in Z direction by 1. There is no taping. This airfoil is intended for 2D analysis.

[[File:Property_airfoil.png|250px]]

User can change the four numerical numbers to create different NACA airfoils. The mesh density refers to the number of segments along the airfoil circumference. A large number would generate a dense mesh. Hit "Apply" to make the changes effective.

The matrix on the bottom half of the "Properties" panel is the transformation matrix. It can be seen for other objects.

=Amplitude=

Amplitude is mulit-linear x y relation that is used for specifying time-history of some boundary conditions. It can be created as a geometry object so that users can see the polylines that represent the amplitude. User can set the view to 2D in -Z direction.

The "+" and "-" buttons in the "Properties" panel are for adding and deleting points. User can manually enter the X Y values of each point. User can also drag the little sphere in the view to modify the polyline, as seen in the figure below.

[[File:Setup_amplitude.png|600px]]

The actual X (time) Y (amplitude) values used by the solver are scaled by the X Y factors respectively.

Always hit "Apply" in the "Properties" panel to save all changes.

=Axis=

Axis is an object that can be created and placed at specific locations. For example when users want to define a reference frame, the rotational axis must be given. An axis can be created and placed at the center of rotation for this purpose.

An axis is defined by the origin and direction. The third entry "Length" is for display purpose. Unless otherwise stated Polaris CFD solver does not use the length of the axis.

=Box=

A box is a useful geometry in Polaris CFD. It can be used to represent the simulation domain, a VR domain or a solid object.

A box is defined by X Y Z lengths and its center.

=Cone=

To create a cone, users shall specify its radius, height, center and direction. The resolution refers the number of segments along the circumference. If "Capping" is unchecked the cone's bottom cap will not be created.

[[File:Setup cone.png|600px]]

=Cylinder=

Cylinders can be created similar to cones. However cylinders are created in Y direction. User can use the transformation matrix in the "Display" panel to transform the cylinder after it's created.

=Line=

A line is created by specifying two points. User can either manually enter the coordinates or drag the points in the view. To create a line along one of the coordinate axes, simply click on the axis button in the "Properties" panel.

[[File:Setup line.png|600px]]

=Point=

Points can be used as probes to collect data at certain points. They can be used for other purposes as well. To create a point, simply enter three coordinates or drag the point to desired location. For 2D analysis the z coordinate is not used by the solver.

=Sphere=

A sphere is defined by the center and radius. User can specify the mesh density by entering "Theta Resolution" and "Phi Resolution". Theta and Phi refer to the spherical coordinates.

[[File:Setup sphere.png|600px]]

User can also specify the range of Theta and Phi if a partial spherical surface is desired.

=Text=

Text is usually created for display purpose. It is more commonly used in postprocessing.

=Triad Axes=

A triad axes is a set of three orthogonal axes. User shall specify the location and X Z axes. The Y axis is computed internally. A triad axes is useful for defining the local reference coordinates for an object.

All triad axes show X axis in red, Y in yellow and Z in green. No text label is displayed.

[[Category:Geometries]]

Case Definitions

2015-07-24T15:32:24Z

Altadyna: /* Inlet/Outlet */

Polaris CFD adopts SI units in setting up a simulation. All quantities, such as velocity, density and temperature etc are in their corresponding SI unites.

=Vector=
Clicking on menu "Setup->Definitions" will bring up the "Vector Definition" dialog as shown below.

[[File:Setup_vector.png|500px]]

A vector is defined by a name, magnitude and direction in x, y, z. Vector's name must be unique. User can add or delete a vector by right-clicking the table. To edit an existing vector, click on the vector in the table and edit it above. Then click on "Apply" to accept the changes.

=Reference Frame=
A reference frame is a technique to model continuous rotation against a fixed axis. Users define a reference frame by giving a name, rotational speed (rpm) and axis. Then assign it to a geometry such as a fan or a rotor. Polaris CFD solver will create an internal axisymmetric region to encompass the geometry. The internal geometry will be larger than the volume of swept by the rotational geometry. The "Offset" value dictates how much bigger it will be. The internal geometry can also be "Cylinder" or "Fit" in shape.

[[File:Setup_rf.png|500px]]

A "Fit" shaped reference frame is illustrated in the figure above. An axis of rotation must be defined prior to defining the reference frame. Users can define multiple reference frames by right-clicking the table. It may be noted that when there are other geometries near the rotation geometry, the offset value must be carefully chosen so that the reference frame does not intersect the other geometries.

=Motion=

Polaris CFD supports two kinds of motions, prescribed motion and 6-DOF motion. A motion can be either prescribed or 6-DOF, but it cannot be both at the same time. Polaris CFD solver will handle all movements by rediscretization. A continuous rotation against a fixed axis can be defined as a motion as well. Reference frame will not be created.

[[File:Setup_movement.png|500px]]

"Prescribed motion" can have a translation velocity and a time history profile. Such a profile must be defined prior to defining the motion. Same applies for rotations.

"6-DOF motion" is defined by its starting and ending times. Mass and moments of inertia must be defined as well.

After defining a motion users can assign it to appropriate geometries/regions.

=Global Parameters=
This page contains some of the most important parameters for setting up a simulation. Most of the parameter names are self-explanatory and are common in most CFD software. Users shall make sure all these parameters are correctly selected/entered.

[[File:Setup_global.png|500px]]

User can choose one of four different analysis types, i.e. direct numerical simulation (DNS) and three turbulence models. When the flow speed is very low, e.g. less than Mach 0.05, users can set "Matching Mach number" to "No". Then input "Max expected velocity" to be 3 or 5 times the characteristic velocity, depending on the actual situation. This will accelerate the simulation significantly.

The "Comment" text box is for users to enter some text for self reference. This text will be printed when the Polaris Solver runs.

=Variable Resolution=

The "Refinement" tab defines the variable resolution (VR) used for simulation. Users define finer grids at interested locations to achieve better accuracy without significant penalty of computational cost.

The first entry is "Simd length unit". Users can choose one of the commonly used units: millimeter, meter, inch, foot, etc. This tells Polaris CFD that all geometries that user imported and created are in this length unit. Users do not need to manually scale each geometry unless several imported geometries are in different units.

The "Finest voxel size" is defined in the chosen length unit as well. The "Finest level" is an integer to define the finest level. Polaris CFD's variable resolution starts at level 0, the coarsest level. Coarsest voxel size = Finest voxel size x 2^(Finest level). For example, if finest voxel size is 0.03mm and the finest level is 5, the coarsest voxel size at level 0 is 0.03 x 2^5 = 0.96 mm.

[[File:Setup_vr.png|500px]]

Adaptive mesh refinement (AMR) is a favorable feature to activate the module in Polaris CFD solver to dynamically refine the simulation grid based on certain criteria. For example users can use AMR to refine the grid along a shock wave after it's formed during simulation.

AMR process itself costs time and slows down the simulation. Users can specify when to start AMR and how often to perform AMR. "Flow gradient" is a parameter to control the sensitivity of AMR regridding. Smaller value will trigger more cells/voxels, i.e. larger regions to be refined.

"Fast seeding level" is a feature to run a simulation with the coarse levels, up to the seeding level first. Finer levels will be added when AMR kicks in. This feature will run simulation fast initially to damp out all the initial effects.

"Surface normal" is a way to control refinement along edges and sharp corners. A smaller value indicates a sharper edge.

=Materials=

Users can define different materials, such as gas, fluid and solid, for simulation. Each material must have a unique name and a set of properties.

[[File:Setup_material.png|500px]]

=Initial Conditions=

Initial condition is a set of the initial values assigned to a region of fluid or solid. In Polaris v3.60 only fluid regions are assigned with initial conditions. Users can define multiple initial conditions and assign them to different fluids.

[[File:Setup_ic.png|500px]]

It is possible to create an initial condition according to the atmosphere at different elevations. To do that simply enter the elevation and click on "Create IC IO". The corresponding initial condition (pressure and temperature) will be created. User just needs to assign a velocity vector.

=Boundary Conditions=

Boundary conditions are assigned to faces (geometry surfaces). Polaris CFD supports three types of boundary conditions, "Specified temperature", "Specified heat flux" and "Specified velocity". "Specified temperature" and "Specified heat flux" are only effective when heat transfer is activated in the "Global" tab. Only one of them can be enabled at a time.

"Specified velocity" means moving wall boundary condition.

[[File:Setup_bc.png|500px]]

=Inlet/Outlet=

Polaris CFD supports a variety of inlet and outlet (IO) definitions. When a user defines an IO, the following steps shall be considered
# Specify the IO type, i.e. pick “Inlet” or “Outlet”.
# Pick a category, candidates are “Static pressure”, “Total pressure”, “Total temperature”, “Fixed velocity”, “Fixed mass flux” and “Floating”.
# Specify the combination of variables accordingly. Depending on the IO type and category, as well as which turbulence model is selected, some variables may not be activated for input.

Note that once FT_FIXED_SOURCE is defined at inlet, FT_FLOATING usually is set at outlet. Otherwise the case might be over specified.

[[File:Setup_io.png|500px]]

=Simulation Domain=

The simulation domain (simd) in Polaris CFD is typically a box with six faces. The box is aligned to the coordinate axes and the computational grid.

[[File:Setup_simd.png|500px]]

Simd faces can be defined as inlet/outlet, wall or symmetry plane. When a face is defined as a wall, a boundary condition can be assigned. A simd face can also be defined as periodical.

[[ Category:Case Setup ]]

Viewer Menu

2015-07-21T14:48:51Z

Altadyna: /* Tools */

This page describes the menu of Polaris Viewer. Each section corresponds to an item in the main menu.

=File=

{| border="1" | style="margin: 0 auto;"
|+ File menu
! scope="col" | Menu item
! scope="col" | Action/effect
|-
| New Project || Clear all existing settings and start a fresh empty project
|-
| Open Project || Open an existing project file
|-
| Recent Project || Shows four recently created or modified projects, click to open one
|-
| Save || Save the current project
|-
| Save As || Save the current project to a different project name
|-
| Save Data || Save the current data object itself to disk
|-
| Save Screenshot || Save the snapshot of the current view into an image file
|-
| Save Animation || Save the current view into a time-series images or a video file
|-
| Clear All || Delete all data objects in the "Pipeline Browser". Doesn't affect files on disk.
|-
| New Window || Fires another Polaris Viewer window.
|-
| License || View or change license settings and information
|-
| Exit || Quit Polaris Viewer
|}

=Setup=

{| border="1" | style="margin: 0 auto;"
|+ Setup menu
! scope="col" | Menu item
! scope="col" | Action/effect
|-
| Definitions || Dialog to define vectors and movements for subsequent references/uses
|-
| Case Setup || Dialog to define most of the parameters for Polaris CFD simulation
|-
| Create || Create a geometry or text object directly
|-
| Derived || Create a geometry from a existing geometry object
|-
| Import Geometry || Import a geometry object from a file
|-
| Import Recent || Show four recently imported geometries and import one
|-
| Create a Job || Create a simulation job
|-
| Monitor a Job || Submit and monitor a job
|}

=PostProcessing=
{| border="1" | style="margin: 0 auto;"
|+ PostProcessing menu
! scope="col" | Menu item
! scope="col" | Action/effect
|-
| Load Results || Open a result file
|-
| Load Recent || Shows four recently loaded result files and load one
|-
| Save State || Save the current postprocessing state into a file
|-
| Load State || Open a previously saved state file
|-
| Reload State || Clear window and reopen the current postprocessing state to reload all data files
|-
| Export Data || Saves the current spreadsheet into a .csv file
|-
| Data Analysis || Several functions to analysis the data, details elsewhere.
|}

=Edit=

{| border="1" | style="margin: 0 auto;"
|+ Edit menu
! scope="col" | Menu item
! scope="col" | Action/effect
|-
| Undo || Undo previous operation
|-
| Redo || Redo previous operation
|-
| Settings || Adjust default settings of the Polaris Viewer
|-
| View Settings || Adjust view settings
|}

=View=
Set the visibility of several dockable panels and toolbars.

=Filters=
Various postprocessing functions that will be described elsewhere.

=Tools=

{| border="1" | style="margin: 0 auto;"
|+ Edit menu
! scope="col" | Tools item
! scope="col" | Action/effect
|-
| Python Shell || Bring up the python shell for entering commands
|-
| Start Trace || Start to record the operations
|-
| Stop Trace || Stop recording, save macros (python script) into a file
|}

=Macros=
Edit or execute a macro file

=About=
Shows the general legal information of Polaris CFD software.

[[Category:Viewer]]

Viewer

2015-07-20T10:42:36Z

Altadyna:

This page describe the Polaris Viewer's interface and major functions of the Viewer. It is intended to help new users familiarize with the Polaris Viewer. Details about how to use a particular function are provided in other pages.

[[File:Pviewer default v360.png|600px]]

Above image shows the default Polaris Viewer interface. Similar to other software the menu is on the top. Below the menu is the tool bars. The visibility of different toolbars can be controlled. Each toolbar can be dragged and placed at a preferred location.

Polaris Viewer is inherited from ParaView with some modifications. Most of the descriptions in ParaView User's Manual can be applied to Polaris Viewer.

The "Pipeline Browser" is named in the same way as in ParaView. All the data objects from geometry to results as well as data operations, e.g. slices, are listed in the "Pipeline Browser". When an object is created internally or loaded from a file, it is shown in the "Pipeline Browser".

[[File:Pviewer v360.png|600px]]

Below the "Pipeline Browser" is the "Properties Panel". This panel may have multiple tabs that shows detailed information of the data object. More details about this panel will be provided other pages.

On the right side is the layout of views. This is where the data is displayed. The layout can be split into several views by clicking the horizontal split or vertical split button. See the image below.

[[File:Pviewer_multiple.png|600px]]

A data object can be displayed in multiple views. Only one data object and one view is activated at a time.

[[Category:Viewer]]

Airfoil Analysis

2015-07-08T20:55:28Z

Altadyna: /* Definitions */

This tutorial works through the steps to create a 2d airfoil analysis.

=Airfoil geometry=
There are three ways to have an airfoil.
:Users can create an airfoil using CAD software and save it into an IGS or STL file. Then Polaris CFD can import this file just as it imports any other geometries.

:Polaris CFD can import 2d x y coordinates of an airfoil profile to generate an closed airfoil extruded in z direction. The profile is a text file with the extension .dat.

:Polaris CFD can also generate NACA 4-digit airfoils directly. In this case users can control the mesh density of the generated airfoil.

To begin this tutorial, create a folder and copy "sg6043.dat" to this folder. "sg6043.dat" is in UIUC Airfoil Coordinates Database [http://m-selig.ae.illinois.edu/ads/coord_database.html].

Run Polaris Viewer, import "sg6043.dat". Click and select "Surface with edges".

[[File:Pviewer_sg6043.png|SG6043 airfoil in Polaris Viewer|500px]]

Next click on menu "Setup->Derived->Bounding Box", a bounding box of the airfoil is created. Change the name of the box to "simd" by double clicking "Box1" in the "Pipeline Browser". Then set X length and Y length to 25 and 20 respectively. Set the center of the "simd" box to (2.5, 0, 0.5). Click on "Apply" button in the "Properties" panel.

Next click on "sg6043.dat" in the "Pipeline Browser", and then click on menu "Setup->Derived->Bounding Box", another bounding box of the airfoil is created. Rename this bounding box to "vr". Set X and Y lengths to 3 and 2.4 respectively and center it at (0.8, 0., 0.5).

Click on "Save Project" and give a name of the project.

=Setup the case=
==Definitions==
Click on menu "Setup->Definitions". In the "Vectors and velocities" dialog click on vector "vx0" and set its magnitude to 60. This will be the incoming flow velocity. Hit "OK" to apply the change and close the dialog.

Click on menu "Setup->Case Setup". In the "Case Setup" dialog, there are multiple tabs. Set the following (accept all other default values):

{| border="1" | style="margin: 0 auto;"
|+ Case parameters
! scope="col" | Tab Page
! scope="col" | Parameter Name
! scope="col" | Enter or Select Value
|-
| Global || Model dimension || 2D
|-
| Global || Analysis type || Turbulence k-e model
|-
| Global || Characteristic velocity || 60
|-
| Global || Comments || tutorial to setup a 2d airfoil, Re=300,000
|-
| Refinement || Simd length unit || meter
|-
| Refinement || Finest voxel size || 0.005
|-
| Refinement || Finest level || 6
|-
| Materials/Air || Kinematic viscosity || 0.0002
|-
| Simulation domain || Bottom (-Y) || wall, frictionless
|-
| Simulation domain || Top (+Y) || wall, frictionless
|}

Click on the "Inlet/outlet" tab, then select "velo_in" to check the turbulence intensity. Use the default values if you do not wish to make a change.

Next click on "OK" to accept and close this dialog. The Reynolds number for this analysis is 300,000.

Save the project.

==Assigning BC==
Make sure that object "sg6043.dat" is highlighted in the "Pipeline Browser". In the BC panel, click "Solid" and then select "Regular Wall". Hit "Apply BC" on the top.

Click on "simd" in the "Pipeline Browser". In the BC panel, click on "Fluid" and then select the material "Air" and set the initial condition to "ic". Check "VR" and set it "0 coarsest". Click on "Apply BC".

Click on "vr" in the "Pipeline Browser". In the BC panel, check "VR" and set it "6 finest". Click on "Apply BC".

Save the project again.

==Attack Angle==

In Polaris CFD attack angle can be applied at the inlet by changing the velocity vector or at the airfoil by rotating the geometry. In this tutorial the attack angle is applied on the latter. Click on "sg6043.dat" in the "Pipeline Browser", in the "Properties" panel, enter -6 for the z component (third box from the left) of the "Orientation".



{| style="margin: 0 auto;"
| [[File:Sg6043_attack0.png|thumb|400px|attack angle = 0 degrees]]
| [[File:Sg6043_attack6.png|thumb|400px|attack angle = 6 degrees]]
|}

==Job==
Click on menu "Setup->Create a job". In the "Create/Edit Simulation" dialog, enter 0.2 for the "Courant number" and 10000 for "Total Steps". Then check these "Output variables": Fluid "Mach number", "Pressure coeff", Surface: "Pressure coeff". Click on "OK" to close this dialog.

Save the project.

=Run the simulation=
This simulation can be run on a desktop from a terminal or from the Polaris Viewer. It takes about 2 days using a desktop with 4 cores (i5, 3.0 GHz).

=Analyzing the results=
For airfoils, users are typically interested in the lift and drag. Open the force output file in Polaris Viewer or in a text editor, one can find the drag Fx=79.5 N/m, lift Fy=2881.1 N/m, the air density=1.293 kg/m^3 as reported by the solver, the characteristic velocity=60m/s, characteristic length=1m, one can compute Cd=0.034, Cl=1.235 which match the results in [http://m-selig.ae.illinois.edu/uiuc_lsat/Low-Speed-Airfoil-Data-V3.pdf Summary of Low-Speed Airfoil Data].


In Polaris Viewer, load surface result file and set the view mode to "Wireframe". Load the fluid result file and set the view mode to "Surface" and then pick "Mach number" as the display variable. Go to the last timestep. Zoom in to the airfoil and one can observe this plot.
[[File:Sg6043d_mach.png|400 px]]

One can plot isolines for 2d fluid results. First click on the fluid file in the "Pipeline Browser", then click on menu "Filters->Alphabetical->CellDataToPointData". Hit "Apply" in the "Properties" panel to convert fluid cell data to point data. Then click on the "Contour" button in the toolbar or in the "Filters" menu. Select "Cp" as the "Contour By" variable. Click on "New Range" in the "Properties" panel and set 21 intervals. Hit "Apply" in the "Properties" panel to see the isolines. The isolines initially are white. Users can color them by a variable.

[[File:Sg6043d_Cp_contour.png|400 px]]

To plot the Cp against chord position, first click on the surface result file in the "Pipeline Browser". Then click on menu "Filters->Alphabetical->CellDataToPointData". Hit "Apply" in the "Properties" panel to convert surface cell data to point data. Then click on menu "Filters->Alphabetical->ScatterPlot". Hit "Apply" in the "Properties" panel to convert surface cell data to point data. An x-y chart is shown in the main view. Activate the "Display" panel, set "X Axis Data" to "Use Data Array->Points (0)". In the "Line Series", uncheck all except "Cp". Click on "Cp" there and set "Line Style" to "None" and "Marker Style" to "Cross".

[[File:Sg6043d_scatter_plot.png|thumb|140 px]]

[[File:Sg6043d_Cp_scatter.png|500 px]]

[[Category:Tutorials]]

Creating Job

2015-05-21T01:49:15Z

Altadyna: /* Third party format */

To define a simulation, namely a job, click on the "Create" button to open the following dialog.

[[File:Create_Job_1.png|caption|400px]] [[File:Create_Job_2.png|caption|400px]]

=Job name=
Job name is automatically filled in or updated when a project is saved or renamed. However user can enter any text to name the job. All simulation result files will start with this "Job name". Due to differences in different operating systems, it is strongly advised that the job name does not contain space and special characters.

=Simulation parameters=
:Courant number
::Similar to most transient analysis software, Courant number is directly proportional to the timestep size. A small Courant number will improve stability, but would require more increments to reach a desired solution. Users shall experiment with Courant number for new simulations to find the optimal value for both stability and efficiency.

:Total steps
::This input controls the total number of increments the simulation will run, regardless of timestep size. Simulation completes after the total number of steps is reached. Set this input to 0 to disable it.

:Total time
::This input controls the total physical time for the simulation, regardless of total steps. Enter 0 to disable. When both "Total steps" and "Total time" are given, simulation completes when one of them is reached.

:Acoustic analysis
::Enter the starting step for acoustic analysis, 0 to disable acoustic analysis. Typically acoustic analysis starts after the simulation has reached a relatively stable state, i.e. all initial transient effects have been dissipated.

=Request output=
==Output folder==
Output folder by default has the same name as the project. Users are free to assign a name or pick an existing folder. It is desirable to keep the output folder inside the project folder.

==Output frequency==
:Output frequency
::This means write output every N steps. Here one step means level 0. This is the frequency the flow field is written to disk. Some other quantities, such as force and measurement/probe outputs are dumped at different frequencies.
:Output start step
::Sometimes users are not interested in the initial results. This input is designed as a convenient way to save disk spaces.

==Output variables==
Users can select some of the variables to output. These selectable variables are in two categories: Fluid and Surface. Turbulence related variables are in the "Advanced options" tab. They will not be written if the analysis is DNS.
It may be noted that certain variables, such as density, temperature and velocity, are always written for postprocessing.

=Restart simulation=
Restart is a nice feature when a simulation was terminated early due to various reasons. One common situation is after performing postprocessing user finds it's necessary to run the analysis for more steps. Some of the analysis parameters, such as the Courant number can be modified for restart.

The number of MPI processes must be the same in the restart run.

:Restart from step
::When it's non zero the simulation is in restart mode. The relevant information for the specified restart step must have been stored in previous analysis. In the output folder there should be a folder named restore.N, where N is the requested restart step. If that folder does not exist an error will be reported and the simulation will terminate.

:Restart file frequency
::This number specifies how frequent a restart point is written. By default the last two restart points are kept.

=Third party format=
Several other popular formats are supported in addition to the generic output format. Users can request formats such as TecPlot and Plot3D for fluid and surface results. Force history is a .csv text file that can be imported many postprocessing software.

[[Category:Jobs]]

Managing Job

2015-05-20T18:11:39Z

Altadyna:

A job in Polaris CFD is a simulation defined by the project file. Users can submit a job to start running on a cluster or local workstation.

=Submitting a job=
After a project has been setup, its simulation can be submitted from the viewer. Click on the "Job Monitor" button to open "Job Monitor" dialog.

[[File:Job_Monitor_0.png|caption|600px]]

==Specifying solver options==
A few job options can be specified at run time. Each of these options is special and can affect the simulation result in certain ways.

Options related to solver licenses (note that solver license is different from viewer license)
:-query_lic_server
::query license information, such as license expiration date and how many licenses are available
:-list_lic_usage
::shows the licenses been used by all running simulations
:-release_all_lics
::releases all the solver licenses held up by this client computer. This option is useful when previous job was terminated abnormally without releasing the licenses. Note that client compute cannot ask the license server to release solver licenses held up by other computers. License server's administrator can perform such a task.

Options related to MPI
:-np <N>
::run the simulation with N processes
:-hostfile <hostfile>
::specify a hostfile/machine file for MPI. A sample hostfile is provided in the "res" folder. Refer to MPI specification for explanations.

Options related to simulation
:-exact_resolution
::grid cell size will equal to the user defined value exactly. When this option is given discretization may be less robust. This option is useful for some validation cases.
:-no_shared_mem
::effective for linux only. Shared memory will be turned off. More memory consumption is expected. This option is useful when some linux OS or hardware causes simulation with shared memory to crash.
:-user_routine <lib>
::supply a shared lib with user subroutines to modify the simulation for user specific analysis. Please refer to "User Subroutine" for details about how to create user subroutines and shared libraries.
:-no_stepping
::run discretization only. Solver quits immediately after discretization without time stepping.
:-help
::how to run the solver

==From "Job Monitor" dialog==
User can enter solver options, if it's necessary, specify number of MPI processes and/or the hostfile, then click on "Submit Job". Screen output from the solver will be shown in the text area.

==From command line==
It is strongly advised that user enters the project folder first. Then issue the command below to start a simulation.
:command for linux
:: polaris_solver.sh [-np <N>] project.aries >& screen.out
:command for windows
:: polaris_solver.bat [-np <N>] project.aries > screen.out

A file "screen.out" will be generated immediately after the command is issued. User can use any text editor to check the status of the simulation.

=Monitoring job status=
For each simulation it is important to monitor the simulation for stability, efficiency, convergence and accuracy. It is sometimes necessary to kill a job after a few steps of simulation, to make adjustments to the geometry, VR or other parameters.

==Screen output==
Screen output first reports the solver version and license server information. Then it echos the project setup and definitions. Later it reports the summary of discretization. Time stepping follows. Messages related to adaptive mesh refinement and moving geometry will be reported when they occur.

==Monitoring force history==

[[File:Job_monitor.png|thumb|200px]]

Force history often is a good indication for convergence. When the job is running, from the "Job Monitor" dialog, click on "Show graph" and open the file "project_force.csv".

The graph will automatically update when data is available. The horizontal axis is "Time", the physical time simulation has reached. On the right side is a list of variables available for plot. "Time", "Force:X", "Force:Y" and "Torque:Z" are always in the force history file. Other components are available if they were requested and/or the simulation is a 3D analysis.

User can right click in the graph area and select "Set axis range" in the popup menu. The range of each axis can be specified. Default range is automatically computed to cover the min and max values.

=Killing a job=
If a simulation is submitted from the viewer, click on the "Kill Job" button. On any platform users may have to kill the solver process manually.

=Restarting a job=
Parameters related to restart are defined in the project setup. User just need to resubmit the job after setting restart parameters in project setup. It's an good idea to pipe screen output into a different file.

[[Category:Jobs]]