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June 29, 2015: A new tutorial is under construction and will be updated to include the operation with OpenVSP 3.x.x. A tutorial video introducing the use of VSPAERO through the OpenVSP GUI can be found in this VSPAERO Tutorial video. Information related to the older VSPAERO v.1.0 is displayed below the heading “VSPAERO 1.X”.

VSPAERO is a fast, linear, vortex lattice solver which integrates actuator disks that can be accurately and easily described for aero-propulsive analysis. Discrete vortices are applied to each panel generated in the OpenVSP degenerate geometry file and then evaluated over the entire surface to obtain a pressure distribution, and thus force. This information can be used to find lift, drag, slip, and (x,y,z) forces and moments. The flow over a section of panels behind a propeller can be analyzed by implementing actuator disks into the solver, which modifies the local freestream to account for increased speed and vorticity induced by the propeller. The actuator disks may be left inactive (empty) if the freestream/glide condition is to be analyzed. VSPAERO also has the ability to calculate the skin friction drag of each component in a model by applying a simple flat-plate drag model to each panel.

VSPAERO also comes with an attached Viewer application which displays wakes and Delta-CP gradients (pressure coefficient change). This application is particularly useful in locating problem areas in a model or visualizing trailing vortex formation - see below. Some theory behind the Vortex Lattice Method (VLM) can be found here.

VSP Viewer example of a modeled Tecnam P2006T with actuator discs and side-slip.

VSPAERO was developed by David Kinney, Ph.D. at NASA Ames Research Center.

Once you have an appropriately defined model that you would like to analyze (see Modeling for VSPAERO), you will need to generate a degenerate geometry file if running the vortex lattice method or a Cart3D surface triangulation file if running the panel method. You will then need to generate a setup file and define any additional parameters to be considered.

The degenerate geometry file is required if running VSPAERO's vortex lattice solver. Degenerate geometry files are representations of three dimensional models in progressively simple frames. For example, a three dimensional model is represented in its entirety, followed by a flat-plate representation, followed by a stick representation. More detail on degenerate geometry can be found here in the 2013 OpenVSP workshop presentation by Rob McDonald of CalPoly. These files can be used in several different physical applications such as Euler-Bernoulli beam theory and vortex lattice solvers.

It is important to note that DegenGeom will write ALL of the components in a model unless you specify a geometry set! The degenerate geometry files for your selected set of components are written from OpenVSP either by choosing DegenGeom under the Analysis menu or by opening the VSPAERO GUI and clicking Launch Solver. This will write a comma separated value (.CSV) file and a MATLAB (.M) file. VSPAERO is primarily concerned with the CSV file. If you choose, you can open these files in a code viewer (in the case of the CSV you may use Excel or similar) and see all of the points that describe a component. A free, open-source code editor that is commonly used is Notepad ++. In addition, the Preview VLM Geometry button on the Overview tab of the GUI is available.

In order to execute VSPAERO's panel method solver, the geometry set must be described in the Cart3D *.tri surface triangulation format. In the VSPAERO GUI, this is done automatically if the Panel Method toggle is selected under “Case Setup” on the Overview tab. On the Advanced tab, the file name and directory of the *.tri will be listed next to the Panel label under “Advanced Case Setup”. Clicking Launch Solver will generate a Cart3D mesh of the geometry set. However, if a MeshGeom has already been created through the OpenVSP GUI, it will be deleted before a new one is generated.

If running VSPAERO's panel solver through the command line, additional methods are available to generate a *.tri file. An intersected Cart3D mesh can also be output from the CFD Mesh GUI. Generating the *.tri file through the CFD Mesh GUI allows for more advanced mesh control, for which more information can be found on the OpenVSP CFD Meshing Guide. An unintersected Cart3D mesh can be generated by opening the Export GUI from the File drop-down, indicating the desired export set, and clicking Cart3D (.tri). For a more in-depth guide to Cart3D file generation in OpenVSP, see VSP Mesh Generation for Cart3D Guide.

You MUST have a DegenGeom or Cart3D file written to perform this step in OpenVSP!

Now that your model has an associated DegenGeom/Cart3D file, you can begin writing your setup file. VSPAERO recognizes this file by the name modelname_DegenGeom.vspaero if running the vortex lattice method and modelname.vspaero if running the panel method. This can be done several ways, some of which are faster and more accurate than others. The Setup file must be in the same directory as the DegenGeom/Cart3D file for VSPAERO to successfully launch. Note that the following descriptions use the VSP coordinate system.

If you are using VSPAERO from the Command Prompt window, you are able to write some of the setup information into a file associated with your model. This process is covered in the VSPAERO from Command Prompt Window section.

You may also manually write the inputs by using your favorite text editor. This is useful if you already have a .vspaero file with the desired inputs and simply wish to paste the information to a new file. Be aware that the extension MUST be .vspaero! In Notepad, for example, you must choose “all file types” and type the extension after the file name for the file to save correctly. This method is also important if you are unable to use the VSPAERO GUI in OpenVSP for any reason. Shown below is an example of a Setup file. Feel free to copy this template into your own setup file as a guide. The descriptions shown in parentheses should be removed prior to running the solver.

Sref = 143.903061      (The wing planform reference area in square feet)
Cref = 3.918           (The mean geometric chord of the wing in feet)
Bref = 38.300000       (The projected span of the wing in feet)
X_cg = 10.183607       (The vehicle CG X distance in feet from the origin)
Y_cg = 0.000081        (The vehicle CG Y distance in feet from the origin)
Z_cg = -0.036126       (The vehicle CG Z distance in feet from the origin)
Mach = 0.27992         (Mach number)
AoA = 0.23023          (Angle of attack or alpha in degrees)
Beta = 0.000000        (Side-slip angle in degrees)
Vinf = 303.8058        (Freestream velocity in ft/sec)
Rho = 0.00186846       (Air density at the desired altitude in slug per cubic feet)
ReCref = 6.220E+06     (Reynolds number based on altitude, speed, and Cref)
ClMax = -1.000000      (Max sectional lift coefficient limit, -1 = No Limit)
Symmetry = no          (Defines a plane of symmetry.  No=no symmetry.  Y=symmetric across XZ plane. X=symmetric across YZ plane.  Z=symmetric across XY plane.)
FarDist = -1.000000    (Distance where wakes return to freestream, -1 = VSPAERO computes the distance)
NumWakeNodes = 0       (Defines the number of wake nodes.  0=free.)
WakeIters = 5          (Number of iterations to compute in the solver)
NumberOfRotors= 1      (Defines the number of actuator discs in the model)
PropElement_1          (Name of disc element)
1                      (Disc ID)
1.15 0 0               (Disc center location in X Y Z)
1.00  0.00 0.00        (Disc unit normal vector in X Y Z)
3.25                   (Disc radius in feet)
0.5                    (Disc hub radius in feet)
-2600                  (Disc RPM.  Positive indicates counter-clockwise as viewed from the pilot.)
0.057797173            (Thrust coefficient)
0.07248844             (Power coefficient)

Another way of generating a Setup file for your model is to use the VSAPERO GUI within OpenVSP. This may be the easiest way to generate a file from scratch for a new model.
In the Overview tab, you'll find several different sliders and inputs that will help you define a Setup file. More detail in the use of this console is covered in the "Introduction to VSPAERO" video. Once each value is defined for the flow conditions to be analyzed, click the Launch Solver button to automatically generate the Setup file and run VSPAERO.
If you view the *.vspaero file, you should see that most of the values have been written in. However if you want to conduct a more detailed analysis you must further specify the values in the file and run VSPAERO through the command line or an external script. Reynolds number, density, Vinf, among others are not written for you.

VSPAERO allows for trimming of the vehicle’s control surface deflections by defining control surface groups in the the VSPAERO setup file. This is facilitated by the Control Grouping tab of the VSPAERO GUI. The middle browser labeled “Available Control Surfaces” lists all rectangle and control surface sub-surfaces that can be added to a control surface group. They are named using the following convention: “GeomName_SurfaceName_Sub-SurfaceName”. If no control surface groups have been created, the middle browser will be empty. A control surface group is created by clicking the “Add” button under the left-most browser labeled “User Groups”. The group can then be renamed using the “Group Name” input. The desired control surfaces can be added to the group using the “Add Selected” or “Add All” buttons under the middle browser, moving them over to the right-most browser labeled “Grouped Control Surfaces”. A control surface can only be added to a group once, but a control surface can be added to multiple groups. When selected within a particular group, available control surfaces will be highlighted in red and those already added to the group will be highlighted in green. In addition, the button labeled “Auto Group Remaining Control Surfaces” will define control surface groups for all symmetric control surfaces still available.

When a control group is selected, each control surface in the group will appear under the “Deflection Gains per Surface” divider. Here, the gains can be adjusted to allow for mixing of control surfaces within a group. For example, asymmetric aileron deflection or symmetric flap deflection. Note, the default value for all gains is 1, which will cause an asymmetric load distribution for a symmetric control surface group. On the Overview tab of the GUI, all control groups will be listed under the “Control Group Angles” divider. Each control group will have a toggle next to its name that determines if the group should be included in the VSPAERO run. If the toggle is selected, the deflection angle for the entire control group can be specified.

When running VSPAERO through the OpenVSP GUI, the program will automatically read and write the appropriate files in the directory that you are currently working. This is particularly useful for organizing the many files associated with the program. If you are running VSPAERO via the Command Prompt window, you generally need to have all of the DegenGeom and Setup files in the same directory where vspaero.exe is located. More information on running VSPAERO without the GUI is found in the VSPAERO from Command Prompt Window section.

You'll notice that the Advanced tab in the VSPAERO console has a Num CPU entry. This feature allows you to specify how many of your computer's processors you wish to use. If, for example, you are working on something else and don't want all of your resources taken by the solver, just set the number to 1 or 2 depending on your computer setup. This will make the solver run slower, but free up resources for you to perform other tasks. However, if you want the solver to run as fast as possible you should set the number to the full number of processors installed on your computer. If you set the number greater than the number of processors installed, it will use all installed processors. Keep in mind that VSPAERO has been optimized to run on fewer processors than previous versions. This means that the more processors you run in parallel, the faster it will run but with diminishing returns. Above around 10, the code itself becomes a limiting factor and not the processor power. It is strongly recommended that you conduct a performance test with some simple cases if you are able to run on more than 10 processors to determine the optimal number for your situation.

To run VSPAERO, simply click the Launch Solver button on the bottom left of the console. The buttons should fade and the Kill Solver button should activate. This is used to stop the solver should you find a mistake in the setup file or if the solver is not converging. In the display at the bottom of the GUI, visible on all tabs, you will see the printed text of VSPAERO running through iterations. The solver is done running when there is extra space at the bottom of the readout (you'll recognize it) and when the buttons on the bottom of the GUI are once again active. The appropriate output files will be placed in the working directory.

VSPAERO Launched Successfully	VSPAERO Finished

VSPAERO may be run from the Command Prompt if you wish to override some settings, cannot operate the GUI, or want to explore some of the other capabilities of the application.

1. You need to find Command Prompt on your computer. This can be done by clicking the Start or Window button on your desktop toolbar (or pressing the Window key on your keyboard) and searching for Command Prompt.
2. Once Command Prompt is running, you will change the directory to the location of vspaero.exe which is usually in the same folder as OpenVSP. Unless you are familiar with operating in Command Prompt, the easiest way to accomplish this is by:
   1. Opening the folder where VSPAERO is located
   2. Right-click the address bar and copy
   3. You will then return to the Command Prompt window and type CD
   4. Right-click inside the window and paste. The entry should look like this: Current Directory>CD NewDirectoryPath.
   5. Press enter. You should now see the address of the VSPAERO home folder displayed as the working directory.
3. Typing vspaero will display the usage for the vspaero command.
   1. The display should look like this:
      
   2. Above you will notice that the display shows the correct usage of the vspaero command. Suppose that you want to solve using 4 processors and you also want to calculate some of the stability derivatives for your model. An example of the command for this would be: vspaero -omp 4 -stab modelname_degengeom.
   3. You will also notice that there are several options listed that are not currently integrated into the VSPAERO GUI such as solving for stability derivatives and controlling the wake calculations. Running VSPAERO in Command Prompt is the ONLY way to perform these operations at this time.
   4. In order to analyze a model, the ModelName_DegenGeom.csv file should be in the directory where VSPAERO is housed along with the ModelName_DegenGeom.vspaero setup file. This minimizes the effort of writing a long string every time you wish to call a file from a different directory. When operating from Command Prompt, finish analyzing your models then move the associated files into a folder where you can safely store the results.
4. Run VSPAERO under the proper usage discussed above. You will see the solver running in the window. When VSAPERO is finished, you will see the appropriate output files in the working directory.
5. Repeat this process as needed for your analyses.

VSPAERO will write several files containing information important to analyzing models. A discussion of each file type and their associated values is shown below.

The History file contains the integrated values as computed by VSPAERO for each iteration. Here is where you will find much of the “big picture” data that you will need for baseline aerodynamic analyses such as the lift coefficient, induced drag, force and moment coefficients, etc…
Please scroll to see all values.

# Name                   Value      Units             
Sref_                  45.0000000 Lunit^2             
Cref_                   2.5000000 Lunit               
Bref_                  18.0000000 Lunit               
Xcg_                    2.9375800 Lunit               
Ycg_                    0.0000000 Lunit               
Zcg_                    0.0000000 Lunit               
Mach_                   0.3000000 no_unit             
AoA_                    1.0000000 deg                 
Beta_                   0.0000000 deg                 
Rho_                    0.0023770 Munit/Lunit^3       
Vinf_                 100.0000000 Lunit/Tunit         
Roll__Rate              0.0000000 rad/Tunit           
Pitch_Rate              0.0000000 rad/Tunit           
Yaw___Rate              0.0000000 rad/Tunit           



Solver Case: 1 

  Iter      Mach       AoA      Beta       CL         CDo       CDi      CDtot      CS        L/D        E        CFx       CFy       CFz       CMx       CMy       CMz       T/QS 
        1   0.30000   1.00000   0.00000   0.07467   0.00932   0.00019   0.00951   0.00000   7.85064   1.26492  -0.00111   0.00000   0.07466   0.00000   0.00375   0.00000   0.00000
        2   0.30000   1.00000   0.00000   0.07730   0.00932   0.00019   0.00951   0.00000   8.12857   1.36434  -0.00116   0.00000   0.07729   0.00000   0.00011   0.00000   0.00000
        3   0.30000   1.00000   0.00000   0.07774   0.00932   0.00020   0.00951   0.00000   8.17317   1.36651  -0.00116   0.00000   0.07773   0.00000  -0.00008   0.00000   0.00000
        4   0.30000   1.00000   0.00000   0.07774   0.00932   0.00020   0.00951   0.00000   8.17329   1.36656  -0.00116   0.00000   0.07773   0.00000  -0.00008   0.00000   0.00000
        5   0.30000   1.00000   0.00000   0.07774   0.00932   0.00020   0.00951   0.00000   8.17341   1.36658  -0.00116   0.00000   0.07773   0.00000  -0.00008   0.00000   0.00000



Skin Friction Drag Break Out:


Surface                                      CDo 

WingGeom                                    0.00466 
WingGeom                                    0.00466 

Note that the History file also breaks down the skin friction drag into the model's individual component contributions. Typically, full wings will have two contributions while body components, such as a fuselage, will have four contributions, one for each section of the flat plate cruciform.

The LOD file is a spanwise representation of the local lift, drag, and side force coefficients. It is useful for plotting the distribution of forces along a wing or body component to locate problem areas, drag sources, peak lifting sections, and slipstream effects. This file will also aid in the refinement of wing planforms if you are trying to find a particular wing loading curve.

LOD data plotted against ideal elliptical loading curve

Below is an example of a LOD file.

# Name                   Value      Units             
Sref_                  45.0000000 Lunit^2             
Cref_                   2.5000000 Lunit               
Bref_                  18.0000000 Lunit               
Xcg_                    2.9375800 Lunit               
Ycg_                    0.0000000 Lunit               
Zcg_                    0.0000000 Lunit               
Mach_                   0.3000000 no_unit             
AoA_                    1.0000000 deg                 
Beta_                   0.0000000 deg                 
Rho_                    0.0023770 Munit/Lunit^3       
Vinf_                 100.0000000 Lunit/Tunit         
Roll__Rate              0.0000000 rad/Tunit           
Pitch_Rate              0.0000000 rad/Tunit           
Yaw___Rate              0.0000000 rad/Tunit           

   Wing      Yavg     Chord     V/Vinf      Cl        Cd        Cs        Cx        Cy       Cz        Cmx       Cmy       Cmz 
        1   0.87568   3.70000   1.00000   0.06572   0.00021  -0.00038  -0.00094  -0.00038   0.06572   0.01599   0.02573   0.00018 
        1   2.67097   3.10000   1.00000   0.07442   0.00022   0.00063  -0.00108   0.00063   0.07441   0.06481   0.01497   0.00083 
        1   4.46400   2.50000   1.00000   0.08211   0.00022   0.00080  -0.00122   0.00080   0.08210   0.14778  -0.00840   0.00232 
        1   6.25263   1.90000   1.00000   0.08939   0.00018   0.00098  -0.00138   0.00098   0.08938   0.29636  -0.05409   0.00524 
        1   8.03077   1.30000   1.00000   0.09446   0.00008   0.00134  -0.00156   0.00134   0.09444   0.58847  -0.14850   0.01209 
        2  -0.87568   3.70000   1.00000   0.06572   0.00021   0.00038  -0.00094   0.00038   0.06572  -0.01599   0.02573  -0.00018 
        2  -2.67097   3.10000   1.00000   0.07442   0.00022  -0.00063  -0.00108  -0.00063   0.07441  -0.06481   0.01497  -0.00083 
        2  -4.46400   2.50000   1.00000   0.08211   0.00022  -0.00080  -0.00122  -0.00080   0.08210  -0.14778  -0.00840  -0.00232 
        2  -6.25263   1.90000   1.00000   0.08939   0.00018  -0.00098  -0.00138  -0.00098   0.08938  -0.29636  -0.05409  -0.00524 
        2  -8.03077   1.30000   1.00000   0.09446   0.00008  -0.00134  -0.00156  -0.00134   0.09444  -0.58847  -0.14850  -0.01209 



Comp      Component-Name                             Mach       AoA      Beta       CL        CDi       CS       CFx       CFy       CFz       Cmx       Cmy       Cmz 
1         WingGeom                                   0.30000   1.00000   0.00000   0.03887   0.00010   0.00025  -0.00058   0.00025   0.03887   0.00851  -0.00004   0.00014 
2         WingGeom                                   0.30000   1.00000   0.00000   0.03887   0.00010  -0.00025  -0.00058  -0.00025   0.03887  -0.00851  -0.00004  -0.00014 

Information about ADB here.

Stability calculations can be performed in VSPAERO from the Command Prompt or through the GUI by clicking Stability Calculation on the Advanced tab and selecting the type from the drop-down menu (Stability, P Analysis, Q Analysis, or R Analysis). The stability derivatives are calculated by finding a “base” set of values specified from the input VSPAERO file then performing a further 6 solutions based on small step changes in 6 different parameters. This information is then used to find the slope between the calculated points. Note that these values are approximations!! As always, the accuracy of your results will depend highly on the fidelity and accuracy of your model.

An example of a stability file is shown below.

# Name                   Value      Units             
Sref_                  45.0000000 Lunit^2             
Cref_                   2.5000000 Lunit               
Bref_                  18.0000000 Lunit               
Xcg_                    2.9375800 Lunit               
Ycg_                    0.0000000 Lunit               
Zcg_                    0.0000000 Lunit               
Mach_                   0.3000000 no_unit             
AoA_                    1.0000000 deg                 
Beta_                   0.0000000 deg                 
Rho_                    0.0023770 Munit/Lunit^3       
Vinf_                 100.0000000 Lunit/Tunit         
Roll__Rate              0.0000000 rad/Tunit           
Pitch_Rate              0.0000000 rad/Tunit           
Yaw___Rate              0.0000000 rad/Tunit           

#
Case                   Delta    Units         CFx          CFy          CFz          CMx          CMy          CMz          CL           CD           CS           CMl          CMm          CMn
#
Base_Aero              +0.000 n/a         -0.0011613    0.0000000    0.0777333    0.0000000   -0.0000815    0.0000000    0.0777417    0.0001955    0.0000000   -0.0000000   -0.0000815   -0.0000000 
Alpha                  +1.000 deg         -0.0046641    0.0000000    0.1560652    0.0000000   -0.0000959    0.0000000    0.1561329    0.0007853    0.0000000   -0.0000000   -0.0000959   -0.0000000 
Beta                   +1.000 deg         -0.0011609   -0.0000058    0.0777056    0.0001929   -0.0000794   -0.0000007    0.0777140    0.0001955   -0.0000023   -0.0001929   -0.0000794    0.0000007 
Roll__Rate             +1.000 rad/Tunit   -0.0074586    0.0021147    0.0788075    0.0435664   -0.0004172    0.0016127    0.0789257   -0.0060821    0.0021147   -0.0435664   -0.0004172   -0.0016127 
Pitch_Rate             +1.000 rad/Tunit   -0.0024171    0.0000000    0.1393438    0.0000000   -0.0250240    0.0000000    0.1393647    0.0000151    0.0000000   -0.0000000   -0.0250240   -0.0000000 
Yaw___Rate             +1.000 rad/Tunit   -0.0011613   -0.0000001    0.0777341   -0.0010315   -0.0000819   -0.0000001    0.0777425    0.0001955   -0.0000001    0.0010315   -0.0000819    0.0000001 
Mach                   +0.100 no_unit     -0.0011905   -0.0000000    0.0800099   -0.0000000   -0.0001779   -0.0000000    0.0800185    0.0002060   -0.0000000    0.0000000   -0.0001779    0.0000000 
#
#
#             Base    Derivative:                                                                               
#             Aero         wrt          wrt          wrt          wrt          wrt          wrt          wrt    
Coef          Total        Alpha        Beta          p            q            r           Mach         U      
#              -           per          per          per          per          per          per          per    
#              -           rad          rad          rad          rad          rad          M            u      
#
CFx      -0.0011613   -0.2006972    0.0000234   -0.0699703   -0.1004660   -0.0000000   -0.0002923   -0.0000877 
CFy       0.0000000    0.0000000   -0.0003299    0.0234967    0.0000000   -0.0000013   -0.0000000   -0.0000000 
CFz       0.0777333    4.4880870   -0.0015853    0.0119362    4.9288407    0.0000091    0.0227662    0.0068299 
CMx       0.0000000    0.0000000    0.0110540    0.4840712    0.0000000   -0.0114610   -0.0000000   -0.0000000 
CMy      -0.0000815   -0.0008220    0.0001220   -0.0037299   -1.9953965   -0.0000039   -0.0009640   -0.0002892 
CMz       0.0000000    0.0000000   -0.0000418    0.0179187    0.0000000   -0.0000008   -0.0000000   -0.0000000 
CL        0.0777417    4.4914833   -0.0015855    0.0131555    4.9298434    0.0000091    0.0227679    0.0068304 
CD        0.0001955    0.0337931   -0.0000003   -0.0697513   -0.0144306    0.0000002    0.0001051    0.0000315 
CS        0.0000000    0.0000000   -0.0001344    0.0234967    0.0000000   -0.0000013   -0.0000000   -0.0000000 
CMl      -0.0000000   -0.0000000   -0.0110540   -0.4840712   -0.0000000    0.0114610    0.0000000    0.0000000 
CMm      -0.0000815   -0.0008220    0.0001220   -0.0037299   -1.9953965   -0.0000039   -0.0009640   -0.0002892 
CMn      -0.0000000   -0.0000000    0.0000418   -0.0179187   -0.0000000    0.0000008    0.0000000    0.0000000 
#
#
#

The FEM file outputs the aerodynamic forces and moments for each span wise station in a wing section. In addition, each section's leading edge location, trailing edge location, quarter chord location, chord, area, and deformations is identified. The number of span stations is determined by the section's U tessellation. The bottom of the file lists the total calculated forces and moments.

An example FEM file is shown below.

Wing Surface: 1 
SpanStations: 5 

   Wing    XLE_ORIG  YLE_ORIG  ZLE_ORIG  XTE_ORIG  YTE_ORIG  ZTE_ORIG  XQC_ORIG  YQC_ORIG  ZQC_ORIG  S_ORIG     Area     Chord     XLE_DEF   YLE_DEF   ZLE_DEF   XTE_DEF   YTE_DEF   ZTE_DEF   XQC_DEF   YQC_DEF   ZQC_DEF    S_DEF       Cl        Cd        Cs        Cx        Cy        Cz       Cmx       Cmy       Cmz 
        1   0.51962   0.90000   0.00000   4.21962   0.90000   0.00000   1.44462   0.90000   0.00000   0.00000   6.66000   3.70000   0.51962   0.90000   0.00000   4.21962   0.90000   0.00000   1.44462   0.90000   0.00000   0.00000   0.70547   0.02184  -0.03693  -0.10099  -0.03693   0.69855   0.00004  -0.00182  -0.02115 
        1   1.55885   2.70000   0.00000   4.65885   2.70000   0.00000   2.33385   2.70000   0.00000   0.25000   5.58000   3.10000   1.55885   2.70000   0.00000   4.65885   2.70000   0.00000   2.33385   2.70000   0.00000   0.25000   0.81272   0.02437   0.06810  -0.11712   0.06810   0.80461   0.00010   0.01521   0.00069 
        1   2.59808   4.50000   0.00000   5.09808   4.50000   0.00000   3.22308   4.50000   0.00000   0.50000   4.50000   2.50000   2.59808   4.50000   0.00000   5.09808   4.50000   0.00000   3.22308   4.50000   0.00000   0.50000   0.90770   0.02446   0.08714  -0.13354   0.08714   0.89816   0.00011   0.02333   0.00273 
        1   3.63731   6.30000   0.00000   5.53731   6.30000   0.00000   4.11231   6.30000   0.00000   0.75000   3.42000   1.90000   3.63731   6.30000   0.00000   5.53731   6.30000   0.00000   4.11231   6.30000   0.00000   0.75000   0.99773   0.02109   0.10648  -0.15249   0.10648   0.98624   0.00013   0.02803   0.00527 
        1   4.67654   8.10000   0.00000   5.97654   8.10000   0.00000   5.00154   8.10000   0.00000   1.00000   2.34000   1.30000   4.67654   8.10000   0.00000   5.97654   8.10000   0.00000   5.00154   8.10000   0.00000   1.00000   1.06220   0.01033   0.14587  -0.17428   0.14587   1.04785   0.00160   0.03181   0.01885 

   Planform:

   Root LE:   0.00000   0.00000   0.00000 
   Root TE:   4.00000   0.00000   0.00000 
   Root QC:   0.92500   0.00000   0.00000 

   Tip LE:    5.19615   9.00000   0.00000 
   Tip TE:    6.19615   9.00000   0.00000 
   Tip QC:    5.19615   9.00000   0.00000 
Wing Surface: 2 
SpanStations: 5 

   Wing    XLE_ORIG  YLE_ORIG  ZLE_ORIG  XTE_ORIG  YTE_ORIG  ZTE_ORIG  XQC_ORIG  YQC_ORIG  ZQC_ORIG  S_ORIG     Area     Chord     XLE_DEF   YLE_DEF   ZLE_DEF   XTE_DEF   YTE_DEF   ZTE_DEF   XQC_DEF   YQC_DEF   ZQC_DEF    S_DEF       Cl        Cd        Cs        Cx        Cy        Cz       Cmx       Cmy       Cmz 
        2   0.51962  -0.90000   0.00000   4.21962  -0.90000   0.00000   1.44462  -0.90000   0.00000   0.00000   6.66000   3.70000   0.51962  -0.90000   0.00000   4.21962  -0.90000   0.00000   1.44462  -0.90000   0.00000   0.00000   0.70547   0.02184   0.03693  -0.10099   0.03693   0.69855  -0.00004  -0.00182   0.02115 
        2   1.55885  -2.70000   0.00000   4.65885  -2.70000   0.00000   2.33385  -2.70000   0.00000   0.25000   5.58000   3.10000   1.55885  -2.70000   0.00000   4.65885  -2.70000   0.00000   2.33385  -2.70000   0.00000   0.25000   0.81272   0.02437  -0.06810  -0.11712  -0.06810   0.80461  -0.00010   0.01521  -0.00069 
        2   2.59808  -4.50000   0.00000   5.09808  -4.50000   0.00000   3.22308  -4.50000   0.00000   0.50000   4.50000   2.50000   2.59808  -4.50000   0.00000   5.09808  -4.50000   0.00000   3.22308  -4.50000   0.00000   0.50000   0.90770   0.02446  -0.08714  -0.13354  -0.08714   0.89816  -0.00011   0.02333  -0.00273 
        2   3.63731  -6.30000   0.00000   5.53731  -6.30000   0.00000   4.11231  -6.30000   0.00000   0.75000   3.42000   1.90000   3.63731  -6.30000   0.00000   5.53731  -6.30000   0.00000   4.11231  -6.30000   0.00000   0.75000   0.99773   0.02109  -0.10648  -0.15249  -0.10648   0.98624  -0.00013   0.02803  -0.00527 
        2   4.67654  -8.10000   0.00000   5.97654  -8.10000   0.00000   5.00154  -8.10000   0.00000   1.00000   2.34000   1.30000   4.67654  -8.10000   0.00000   5.97654  -8.10000   0.00000   5.00154  -8.10000   0.00000   1.00000   1.06220   0.01033  -0.14587  -0.17428  -0.14587   1.04785  -0.00160   0.03181  -0.01885 

   Planform:

   Root LE:   0.00000   0.00000   0.00000 
   Root TE:   4.00000   0.00000   0.00000 
   Root QC:   0.92500   0.00000   0.00000 

   Tip LE:    5.19615  -9.00000   0.00000 
   Tip TE:    6.19615  -9.00000   0.00000 
   Tip QC:    5.19615  -9.00000   0.00000 


Total Forces and Moments 


Total CL:  0.854039 
Total CD:  0.021681 
Total CS:  -0.000000 
Total CFx: -0.126950 
Total CFy: -0.000000 
Total CFz: 0.844829 
Total CMx: 0.000000 
Total CMy: 0.004251 
Total CMz: 0.000000 

The information below this line is intended for use with VSPAERO v.1.0

A PDF document summarizing the use of the software needed to build a drag profile for an aircraft is available here. The Power Point version of the same is here.

VSPAERO requires degenerate geometry files generated using OpenVSP. It is helpful to remember that the software only uses lifting surfaces to determine lift induced drag and that the surfaces themselves are not required to be excessively smooth. The more detail that you can leave out of the model, the faster the software will run. You will, however, begin to lose information when the tessellation and number of interpolated sections become too low. The recommended tessellation for “simple” geometry wings is between 20 and 40 and the recommended cross section density is about 1 per foot (2 to 3 per meter).

As yet, the software will not recognize body components as generating lift. It is therefore recommended that, for preliminary analyses, you leave out the body objects (FUSE2 objects). This will not only reduce the possibility for computation error but will also greatly reduce processing times.

In order for VSPAERO to function properly, only MS_WING and FUSE2 components should be used in the simplified model to be analyzed. Under no circumstances will the software accept “open” components such as jet engine nacelles. If any component is not water tight, the DegenGeom function of OpenVSP will fail and VSP will crash. As always, save often.

The DegenGeom function of OpenVSP can be found under the Geom menu tab. Execute the operation to generate the files needed from VSP.

The VSPAERO input file is where a lot of mistakes can be made. Incorrect entry of information into the file will result in data inaccuracies or software failure. When you write the files, it is important to minimize the number of unnecessary spaces and returns to reduce the possibility of read error by the software.

In Notepad (or similar text only editing) create a document that has the following format exactly (copy and paste):

Sref= ####
Cref= ####
Bref= ####
X_cg= 0
Y_cg= 0
Z_cg= 0
Mach= ####
AoA= ####
Beta= 0
Vinf= ####
Rho= 0.0023769
WakeIters= 3
NumberOfRotors= 2
PropElement_1
1
#### #### ####
1.0 0 0
####
0.00 
####
####
####
PropElement_2
1
#### #### ####
1.000000 0.000000 0.000000
####
0.00000
####
####
####

Example) Piper Seminole PA-44-180

Sref=183.794
Cref=4.904
Bref=38.6
X_cg=0
Y_cg=0
Z_cg=0
Mach=0.256595212
AoA=-5
Beta=0
Vinf=278.48865
Rho=0.00186846
WakeIters=1
NumberOfRotors=2
PropElement_1
1
4.950000 -6.350000 1.050000
1.000000 0.000000 0.000000
3.083333333
0.00000
2700.000000
0.048727959
0.048901562
PropElement_2
1
4.950000 6.350000 1.050000
1.000000 0.000000 0.000000
3.080000
0.00000
-2700.000000
0.048727959
0.048901562

This will greatly simplify your efforts in writing an input file. The entries in the above text follow this key:

The values in this file should be found using your OpenVSP model, the POH for the aircraft, and the Drag Buildup Workbook. In OpenVSP, the AeroRef tool will provide the values for the first three entries. The POH will have power settings and propeller dimensions. The Drag Buildup Workbook will provide Air Density, Free Stream Velocity, Mach Number, Thrust Coefficient and Power Coefficient from the Flight Conditions section.

Once the proper entries have been made, save the file under the EXACT same name as the DegenGeom files written by OpenVSP with the file extension .vspaero .
Example) modelname_degengeom.vspaero
Now you have the three files that VSPAERO needs to run the model. Copy or move all three files to the folder containing VSPAERO and Viewer (also holding the required .dll files to run) and you are ready to run VSPAERO from the command prompt.

VSPAERO is operated from the command prompt (Windows) or from the Unix shell. For this tutorial, it will be assumed that you are using Windows, however the commands are similar for Unix.

1. In the Command Prompt, change the directory to the folder that houses vspaero using the “cd” command.
   1. Ex) C:\Users\UserName>CD DOCUMENTS\VSPAERO_FILES
2. Once in the correct directory, you will need to execute VSPAero.
   1. Ex) C:\Users\UserName\Documents\VSPAERO_files>VSPAERO ModelName_DegenGeom
   2. If you know the number of processors that your computer has, you can force N number of processors to work on VSPAero using: >vspaero –omp N modelname_degengeom.
      1. Doing this WILL use close to 100% of the selected processor’s power. System performance may suffer if too many processors are used.
   3. Once VSPAero is running, the screen will show the program operating.
   4. Depending on the complexity of the model and the number of processors set to run, this can take seconds or hours just for ONE wake iteration. This is why the model must be sufficiently simple for the program to analyze.
3. If it appears that the process is extraordinarily slow, you may halt the process by typing “CTRL+C”.
4. When complete, the prompt will return to the command line and await the next command.
5. After the program is finished, there will be three files created in the same folder as VSPAERO.
   1. LOD: The component spanwise loading information
   2. HISTORY: The integrated values for the lift, drag, moment, and force coefficients.
   3. ADB: Information for Viewer.
6. The History file contains the information that you should want to copy into the Drag Buildup Workbook.
7. If you want to look for problem areas, use the Viewer application before proceeding with another data run. Initiating another run will overwrite the data in the History and Lod files.
   1. Call the Viewer app using: >viewer modelname_degengeom
   2. Under the Aero menu, select Delta-CP
   3. You will most likely need to change the range of Delta-CP using Options then Set Contour Levels. A normal range for viewer is -2 to 1.
8. At this point, enter the information for the next data run into the modelname_degengeom.vspaero file and save the document.
9. You are now ready to repeat the process and obtain another data set from VSPAERO.

Use of the data obtained from VSPAERO is discussed further in the Drag Buildup Workbook section and in the Drag Buildup Workbook User Manual.

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This page was created and edited by: — Brandon Litherland 2015/07/01 06:56