4.3.2. Input Files

The user configures the aerodynamic model parameters via a primary KiteAeroDyn input file, as well as separate input files for airfoil and rotor performance data. When used in standalone mode, an additional driver input file is required. This driver file specifies initialization inputs normally provided to KiteAeroDyn through KiteFAST, as well as the per-time-step inputs to KiteAeroDyn.

As an example, the driver.dvr file is the main driver, the input.dat is the primary input file, the rotor.dat file contains the rotor performance data, and the airfoil.dat file contains the airfoil angle of attack, lift, drag, and moment coefficients. Example input files are included in Section 4.3.5.

No lines should be added or removed from the input files, except in tables where the number of rows is specified, lines to specify requested output channel names, and comment lines in the airfoil data files.

4.3.2.1. Units

KiteAeroDyn uses the SI system (kg, m, s, N), except for angles. Angles are assumed to be in degrees unless otherwise specified.

Additionally, the user-created KiteFAST controller determines the Ctrl (control signal, e.g. flap angle) units in the airfoil input file.

The driver input file is only needed for the standalone version of KiteAeroDyn and contains inputs normally defined by the calling program (KiteFAST), and necessary to control the aerodynamic simulation for uncoupled models. A sample KiteAeroDyn driver input file is given in Section 4.3.5.

Set the Echo flag in this file to TRUE if you wish to have the KiteAeroDyn_Driver executable echo the contents of the driver input file (useful for debugging errors in the driver file). The echo file has the naming convention of KAD_DvrFile.ech, where KAD_DvrFile is name of the KiteAeroDyn driver input file. DTAero is the time interval (time step) for the aerodynamic calculations, in seconds. KAD_InFile is the filename of the primary KiteAeroDyn input file. This name should be in quotations and can contain an absolute path or a relative path.

The ENERGY KITE REFERENCE CONFIGURATION section defines the KiteAeroDyn-required geometry for the kite, see Figure 1. NumFlaps specifies the number of control flaps per wing-side (starboard/port). NumPylons specifies the number of pylons per wing side (starboard/port). NumFlaps and NumPylons must each be greater than zero. Each kite component is defined relative to its reference point. These reference points are specified in the kite coordinate system. The table consists of three numbers (separated by spaces) on a single line to represent the x, y, and z coordinates of that component’s reference point. There must be a line for each pylon reference point (starting inboard and moving outboard) and a line for each rotor (top, bottom) on each pylon. For example, if NumPylons equals 2, then there will be 4 lines corresponding to the various pylon reference points (2 for the starboard wing, 2 for the port wing) and 8 lines corresponding to the top and bottom rotors on each pylon. The Fuselage must have its reference point located at (0,0,0) and therefore does not show up in the table.

The I/O SETTINGS section controls the creation of the results file. If OutFileRoot is specified, the results file will have the filename OutFileRoot.out. If an empty string is provided for OutFileRoot, then the driver file’s root name will be used instead. If TabDel is TRUE, a TAB character is used between columns in the output file; if FALSE, fixed-width is used otherwise. OutFmt is any valid Fortran numeric format string, which is used for text output, excluding the time channel. The resulting field should be 10 characters, but KiteAeroDyn does not check OutFmt for validity. If you want a sound generated on program exit, set Beep to true.

4.3.2.1.1. KiteAeroDyn Driver Kite Geometry

The WIND AND ENERGY KITE TIME-HISTORY MOTION section allows you to execute a simulation for the given kite specified in the ENERGY KITE REFERENCE CONFIGURATION section and its corresponding KAD_InFile based on a set of inputs which drive the motions of the kite.

The local undisturbed wind speed at any elevation above the ground is determined using,

\[ \begin{align}\begin{aligned}:label: windspeed\\U(Z) = \mathrm{HWindSpd} \times \left( \frac{Z}{\mathrm{RefHt}} \right)^\mathrm{PLexp}\end{aligned}\end{align} \]

where \(\mathrm{HWindSpd}\) is the steady wind speed located at elevation \(\mathrm{RefHt}\), \(Z\) is the instantaneous elevation of an analysis node above the ground (or above the MSL for offshore kites, and \(\mathrm{PLexp}\) is the power-law shear exponent. This wind propagates in the direction of \(\mathrm{HWindDir}\) (in degrees), which follows meteorological convention (clockwise when looking downward), with 0 aligned with global X and positive rotation towards global -Y.

There will be one row in the subsequent table for each of the time steps specified, NumTimes, (plus two table header lines). The information within each row of the table fully specifies the necessary inputs to KiteAeroDyn for a given time step. Each row contains the following columns (in the given order) [Note: the presence of some columns depends on the values of NumPylons and NumFlaps]: Time: timestamp in seconds for the row of input data KitePxi, KitePyi, KitePzi: X, Y, and Z location of the kite’s fuselage reference (0,0,0) point in the inertial, global reference system, (m) KiteRoll, KitePitch, KiteYaw: orientation of the kite, specified via a 1-2-3 Euler sequence (degrees) KiteTVxi, KiteTVyi, KiteTVzi: translational velocities of the kite’s fuselage reference (0,0,0) point in the inertial, global reference system, (m/s) KiteRVxi, KiteRVyi, KiteRVzi: rotational velocities about the kite’s coordinate system in the inertial, global reference system, (degrees/s) SP1TRtSpd, SP1BRtSpd, SP2TRtSpd, SP2BRtSpd: Starboard wing rotor speeds starting inboard and moving outboard and alternating top and then bottom on each pylon [number of columns must match NumPylons times two] (radians/s) PP1TRtSpd, PP1BRtSpd, PP2TRtSpd, PP2BRtSpd: Port wing rotor speeds starting inboard and moving outboard and alternating top and then bottom on each pylon [number of columns must match NumPylons times two] (radians/s) SP1TPitch, SP1BPitch, SP2TPitch, SP2BPitch: Starboard wing collective blade pitch angles starting inboard and moving outboard and alternating top and then bottom on each pylon [number of columns must match NumPylons times two] (degrees) PP1TPitch, PP1BPitch, PP2TPitch, PP2BPitch: Port wing collective blade pitch angles starting inboard and moving outboard and alternating top and then bottom on each pylon [number of columns must match NumPylons times two] (degrees) SFlp1Ctrl, SFlp2Ctrl, SFlp3Ctrl: Starboard wing flap control angle settings [number of columns must match NumFlaps] (units must match airfoil tables Ctrl units) PFlp1Ctrl, PFlp2Ctrl, PFlp3Ctrl: Port wing flap control angle settings [number of columns must match NumFlaps] (units must match airfoil tables Ctrl units) Rudr1Ctrl, Rudr2Ctrl: Control angle settings for the vertical stabilizer surface (units must match airfoil tables Ctrl units) SElv1Ctrl SElv2Ctrl: Control angle settings for the starboard horizontal stabilizer surface (units must match airfoil tables Ctrl units) PElv1Ctrl PElv2Ctrl: Control angle settings for the port horizontal stabilizer surface (units must match airfoil tables Ctrl units)

The first row of the TIME-HISTORY MOTION table must have a time stamp of 0.0 seconds. The Time values must then be monotonically increasing for the remaining rows. The rows do not need to be spaced DTAero seconds apart, even though the time marching increments on DTAero. The driver code will linearly interpolate data in the motion table to generate appropriate inputs for the nth DTAero increment. The simulation will end at the timestamp which is an integer multiple of DTAero but is less than or equal to the last timestamp in the motion table.

4.3.2.2. KiteAeroDyn Primary Input File

The primary KiteAeroDyn input file defines modeling options, environmental conditions (except freestream flow), airfoils, aerodynamic nodal discretization and properties, rotor properties, as well as output file specifications.

The file is organized into several functional sections. Each section corresponds to an aspect of the aerodynamics model. A sample KiteAeroDyn primary input file is given in Section 4.3.5.

The input file begins with two lines of header information which is for your use, but is not used by the software.

4.3.2.2.1. Simulation Control

Set the Echo flag to TRUE if you wish to have KiteAeroDyn echo the contents of the KiteAeroDyn primary input file (useful for debugging errors). The echo file has the naming convention of BaseFilename.KAD.ech. BaseFilename is the filename of the primary KiteAeroDyn input file.

DTAero sets the time step for the aerodynamic calculations. The keyword DEFAULT for DTAero may be used to indicate that KiteAeroDyn should employ the time step prescribed by the driver code (KiteFAST or the standalone driver program).

Set LiftMod to 1 if you want to disable wake/induction Effects (resulting in a simple geometric angle of attack) or 2 to include these effects using the vortex-step model. When RotorMod is set to 0, no rotor power or loads are computed. Setting RotorMod to 1 causes KiteAeroDyn to compute loads and power via a simple actuator disk model.

The UseCM option is currently unimplemented, and defaults to TRUE, which means the InColCM, described in the Airfoil Information section, below, must be > 0.

4.3.2.2.2. Environmental Conditions

AirDens specifies the fluid density and must be a value greater than zero; a typical value is around 1.225 kg/m3 for air. KinVisc specifies the kinematic viscosity of the air (used in the Reynolds number calculation); a typical value is around 1.460E-5 m2/s for air. SpdSound is the speed of sound in air; a typical value is around 340.3 m/s.

4.3.2.2.3. Lifting Line Vortex-step Method Options

The input parameters in this section are not used when LiftMod = 1.

VSMMod determines the propagation direction for the wakes. Set VSMMod to 1 to use the local chord to determine the wake alignment. Set VSMMod to 2 to align the wakes with the kite-averaged free stream direction.

VSMToler sets the convergence threshold for the iterative nonlinear Newton solve of the vortex solution. VSMToler represents the tolerance of the residual equation, which has the units of circulation (m^2/s). When the keyword DEFAULT is used in place of a numerical value, VSMToler will be set to 1E-4.

VSMMaxIter determines the maximum number of Netwon iterations in the solve. When the keyword DEFAULT is used in place of a numerical value, VSMMaxIter will be set to 40. If the residual value of the solve is not less than or equal to VSMToler in VSMMaxIter iterations, KiteAeroDyn will exit the solver and return an error message.

VSMPerturb sets the perturbation size for computing the Jacobian in the Newton iterations. When the keyword DEFAULT is used in place of a numerical value, VSMPerturb will be set to 0.05, which has the units of circulation (m^2/s). We recommend using these defaults.

4.3.2.2.4. Airfoil Information

This section defines the airfoil data input file information. The airfoil data input files themselves (one for each airfoil) include tables containing coefficients of lift force, drag force, and optionally pitching moment versus AoA, as well as UA model parameters (currently unused by KiteAeroDyn), and are described in Section 4.3.2.2.14.

The AFTabMod setting determines the form of table lookup used in each airfoil data file. 1 corresponds to a 1D lookup on angle of attack. 2 provides a 2D lookup on angle of attack and Reynold’s number. 3 corresponds to a 2D lookup of angle of attack and a user-generated control value. The next 4 lines in the AIRFOIL INFORMATION section relate to the format of the tables of static airfoil coefficients within each of the airfoil input files. InCol_Alfa, InCol_Cl, InCol_Cd, and InCol_Cm are column numbers in the tables containing the AoA, lift-force coefficient, drag-force coefficient, and pitching-moment coefficient, respectively (normally these are 1, 2, 3, and 4, respectively).

Specify the number of airfoil data input files to be used using NumAFfiles, followed by NumAFfiles lines of filenames. The file names should be in quotations and can contain an absolute path or a relative path e.g., “C:\airfoils\S809_CLN_298.dat” or “airfoils\S809_CLN_298.dat”. If you use relative paths, it is relative to the location of the current working directory. The kite component sections (described next) will reference these airfoil data using their line identifier, where the first airfoil file is numbered 1 and the last airfoil file is numbered NumAFfiles.

4.3.2.2.5. Fuselage Properties

The fuselage is currently modeled as a drag-only body. Specify the number of aerodynamic nodes with the NumFusNds parameter, followed by NumFusNds lines of nodal data (plus two table header lines). FusX, FusY, and FusZ determine the location of a node within the kite coordinate system, and are relative to the fuselage reference point (0,0,0). These nodes can be ordered from either the front of the kite to the back (monotonically decreasing), or from the back to the front (monotonically increasing). Step changes in the fuselage geometry are specified with adjacent nodes having the same x-value but differing y or z values. The airfoil at each node is assumed to be in the y-z plane, and-along with the nodal locations-the positive aerodynamic FusTwist is specified about positive x, and the chordlength (FusChord) and airfoil table ID (FusAFID) are specified. A zero-degree twist means positive y points toward the trailing edge and negative z points toward the suction side of the airfoil.

4.3.2.2.6. Starboard (Right) Wing Properties

Specify the number of aerodynamic nodes with the NumSWnNds parameter, followed by NumSWnNds lines of nodal data (plus two table header lines). SWnX, SWnY, and SWnZ determine the location of a node within the kite coordinate system, and are relative to the starboard wing’s reference point (also given in the kite coordinate system). In the stand-alone KiteAeroDyn driver case, this point is specified in the ENERGY KITE REFERENCE CONFIGURATION section of the driver input file. In a KiteFAST-coupled simulation, this point is defined in the preprocessor input file under the keypoints section and on the line labeled wing/starboard. The locations of the aerodynamic nodes along the aerodynamic reference line aerodynamic center) with y monotonically increasing. The airfoil at each node is assumed to be rotated from the x-z plane based on the dihedral angle (SWnDhdrl) about negative x resulting in an inclined x-z’ plane (with y’ normal), and—along with the nodal locations—the positive aerodynamic twist (SWnTwist) is specified about positive y’, and the chordlength (SWnChord), airfoil table ID (SWnAFID), and flap ID (SWnFlpID) are specified. A zero-degree twist means negative x points toward the trailing edge and negative z’ points toward the suction side of the airfoil. Calculations for the lifting line vortex method take place at the midpoints between these nodes; instead of interpolating airfoil data, the airfoil and flap IDs at each midpoint is taken to be the airfoil and flap IDs of the corresponding node with lower y.

4.3.2.2.7. Port (Left) Wing Properties

Specify the number of aerodynamic nodes with the NumPWnNds parameter, followed by NumPWnNds lines of nodal data (plus two table header lines). PWnX, PWnY, and PWnZ determine the location of a node within the kite coordinate system, and are relative to the port wing’s reference point (also given in the kite coordinate system). In the stand-alone KiteAeroDyn driver case, this point is specified in the ENERGY KITE REFERENCE CONFIGURATION section of the driver input file. In a KiteFAST-coupled simulation, this point is defined in the preprocessor input file under the keypoints section and on the line labeled wing/port. The locations of the aerodynamic nodes along the aerodynamic reference line (aerodynamic center) with y monotonically decreasing (negative values). The airfoil at each node is assumed to be rotated from the x-z plane based on the dihedral angle (PWnDhdrl) about positive x resulting in an inclined x-z’ plane (with y’ normal), and—along with the nodal locations—the positive aerodynamic twist (PWnTwist) is specified about positive y’, and the chordlength (PWnChord), airfoil table ID (PWnAFID), and flap ID (PWnFlpID) are specified. A zero-degree twist means negative x points toward the trailing edge and negative z’ points toward the suction side of the airfoil. Calculations for the lifting line vortex method take place at the midpoints between these nodes; instead of interpolating airfoil data, the airfoil and flap IDs at each midpoint is taken to be the airfoil and flap IDs of the corresponding node with higher (less negative) y.

4.3.2.2.8. Vertical Stabilizer Properties

Specify the number of aerodynamic nodes with the NumVSNds parameter, followed by NumVSNds lines of nodal data (plus two table header lines). VSX, VSY, and VSZ determine the location of a node within the kite coordinate system, and are relative to the vertical stabilizer’s reference point (also given in the kite coordinate system). In the stand-alone KiteAeroDyn driver case, this point is specified in the ENERGY KITE REFERENCE CONFIGURATION section of the driver input file. In a KiteFAST-coupled simulation, this point is defined in the preprocessor input file under the keypoints section and on the line labeled stabilizer/vertical. The locations of the aerodynamic nodes (black nodes in figure above) along the aerodynamic reference line (aerodynamic center) are specified in the body-fixed (x,y,z) coordinate system relative to its origin, with z monotonically increasing (from possible negative to positive values). The airfoil at each node is assumed to be in the x-y plane, and—along with the nodal locations—the positive aerodynamic twist (VSTwist) is specified about positive z, and the chordlength (VSChord), airfoil table ID (VSAFID), and rudder ID (VSRdrID) are specified. A zero-degree twist means negative x points toward the trailing edge and positive y points toward the suction side of the airfoil. Calculations for the lifting line vortex method take place at the midpoints between these nodes; instead of interpolating airfoil data, the airfoil and rudder IDs at each midpoint is taken to be the airfoil and rudder IDs of the corresponding node with lower z.

4.3.2.2.9. Starboard (Right) Stabilizer Properties

Specify the number of aerodynamic nodes with the NumSHSNds parameter, followed by NumSHSNds lines of nodal data (plus two table header lines). SHSX, SHSY, and SHSZ determine the location of a node within the kite coordinate system, and are relative to the starboard horizontal stabilizer’s reference point (also given in the kite coordinate system). In the stand-alone KiteAeroDyn driver case, this point is specified in the ENERGY KITE REFERENCE CONFIGURATION section of the driver input file. In a KiteFAST-coupled simulation, this point is defined in the preprocessor input file under the keypoints section and on the line labeled stabilizer/horizontal/starboard. The locations of the aerodynamic nodes (black nodes in figure above) along the aerodynamic reference line (aerodynamic center) are specified in the body-fixed (x,y,z) coordinate system relative to its origin, with y monotonically increasing. The airfoil at each node is assumed to be in the x-z plane, and—along with the nodal locations—the positive aerodynamic twist (SHSTwist) is specified about positive y, and the chordlength (SHSChord), airfoil table ID (SHSAFID), and elevator ID (SHSElvID) are specified. A zero-degree twist means negative x points toward the trailing edge and negative z points toward the suction side of the airfoil. Calculations for the lifting line vortex method take place at the midpoints between these nodes; instead of interpolating airfoil data, the airfoil and elevator IDs at each midpoint is taken to be the airfoil and elevator IDs of the corresponding node with lower y.

4.3.2.2.10. Port (Left) Stabilizer Properties

Specify the number of aerodynamic nodes with the NumPHSNds parameter, followed by NumPHSNds lines of nodal data (plus two table header lines). PHSX, PHSY, and PHSZ determine the location of a node within the kite coordinate system, and are relative to the port horizontal stabilizer’s reference point (also given in the kite coordinate system). In the stand-alone KiteAeroDyn driver case, this point is specified in the ENERGY KITE REFERENCE CONFIGURATION section of the driver input file. In a KiteFAST-coupled simulation, this point is defined in the preprocessor input file under the keypoints section and on the line labeled stabilizer/horizontal/port. The locations of the aerodynamic nodes (black nodes in figure above) along the aerodynamic reference line (aerodynamic center) are specified in the body-fixed (x,y,z) coordinate system relative to its origin, with y monotonically decreasing (negative values). The airfoil at each node is assumed to be in the x-z plane, and—along with the nodal locations—the positive aerodynamic twist (PHSTwist) is specified about positive y, and the chordlength (PHSChord), airfoil table ID (PHSAFID), and elevator ID (PHSElvID) are specified. A zero-degree twist means negative x points toward the trailing edge and negative z points toward the suction side of the airfoil. Calculations for the lifting line vortex method take place at the midpoints between these nodes; instead of interpolating airfoil data, the airfoil and elevator IDs at each midpoint is taken to be the airfoil and elevator IDs of the corresponding node with higher (less negative) y.

4.3.2.2.11. Pylon Properties

Specify the number of aerodynamic nodes, per pylon, with the NumPylNds parameter, followed by NumPylNds times 2 (starboard, port) times NumPylons lines of nodal data (plus two table header lines). PylX, PlyY, and PlyZ determine the location of a node within the kite coordinate system, and are relative to the given pylon’s reference point (also given in the kite coordinate system). In the stand-alone KiteAeroDyn driver case, this point is specified in the ENERGY KITE REFERENCE CONFIGURATION section of the driver input file. In a KiteFAST-coupled simulation, this point is defined in the preprocessor input file under the keypoints section and on the line labeled pylon/starboard/PyID and pylon/port/PyID, where PyID varies from 1 to NumPylons. The node list must be structured such that all starboard pylon nodes appear first, starting with the inner-most pylon and ending with the outer-most pylon. Then the port pylon nodes are listed, again starting with the inner-most pylon and ending with the outer-most pylon. The locations of the aerodynamic nodes (black nodes in figure above) along the aerodynamic reference line (aerodynamic center) are specified in the body-fixed (x,y,z) coordinate system relative to its origin, with z monotonically increasing (from possibly negative to positive values). The airfoil at each node is assumed to be in the x-y plane, and—along with the nodal locations—the positive aerodynamic twist (PylTwist) is specified about positive z, and the chordlength (PylChord) and airfoil table ID (PylAFID) are specified. A zero-degree twist means negative x points toward the trailing edge and positive y points toward the suction side of the airfoil. Calculations for the lifting line vortex method take place at the midpoints between these nodes; instead of interpolating airfoil data, the airfoil ID at each midpoint is taken to be the airfoil ID of the corresponding node with lower z.

4.3.2.2.12. Rotor Properties

The rotor properties are defined by giving the rotor’s radius (RtrRad) in meters, and the filename for the rotor’s performance data (RtrInFile) as a quoted string. This data is provided in table form with one line for each rotor. The node list must be structured such that all starboard pylon rotors appear first, starting with the inner-most pylon and ending with the outer-most pylon. Then the port pylon rotors are listed, again starting with the inner-most pylon and ending with the outer-most pylon. Each pylon must contain a line for the top rotor followed by the bottom rotor. The table will contain a total of four times NumPylons lines.

4.3.2.2.13. Output Options

Specifying SumPrint to TRUE causes KiteAeroDyn to generate a summary file with name OutFileRoot**.KAD.sum*. ``OutFileRoot is either specified in the I/O SETTINGS section of the driver input file when running KiteAeroDyn standalone, or by the KiteFAST program when running a coupled simulation. If OutSwtch is set to 1, outputs related to the vortex step method (VSM) calculations are sent to a file with the name, OutFileRoot.VSM.out, and the user-requested output channels specified in the OutList, described below, are sent to a file with the name, OutFileRoot.KAD.out. If OutSwtch is set to 2, and the user is running an KiteFAST-driven simulation, the user-requested KiteAeroDyn outputs are sent to a single file with the name OutFileRoot.out which also contains outputs of other KiteFAST modules. If OutSwtch is set to 3, both file outputs occur, in the case of an KiteFAST-driven simulation. The OutFmt parameter controls the formatting for the output data. KiteAeroDyn currently does not check the validity of these format strings. They need to be valid Fortran format strings. An example valid format string is: "ES11.4".

KiteAeroDyn can output aerodynamic and kinematic quantities at up to nine nodes for each kite component. NFusOuts specifies the number of fuselage nodes that output is requested for (0 to 9) and FusOutNd on the next line is a list NFusOuts long of node numbers between 1 and NumFusNds (corresponding to a row number in the fuselage node table, separated by any combination of commas, semicolons, spaces, and/or tabs. NSWnOuts specifies the number of starboard wing nodes that output is requested for (0 to 9) and SWnOutNd on the next line is a list NSWnOuts long of node numbers between 1 and NumSWnNds (corresponding to a row number in the starboard wing node table, separated by any combination of commas, semicolons, spaces, and/or tabs. NPWnOuts specifies the number of port wing nodes that output is requested for (0 to 9) and PWnOutNd on the next line is a list NPWnOuts long of node numbers between 1 and NumPWnNds (corresponding to a row number in the port wing node table, separated by any combination of commas, semicolons, spaces, and/or tabs. NVSOuts specifies the number of vertical stabilizer nodes that output is requested for (0 to 9) and VSOutNd on the next line is a list NVSOuts long of node numbers between 1 and NumVSNds (corresponding to a row number in the vertical stabilizer node table, separated by any combination of commas, semicolons, spaces, and/or tabs. NSHSOuts specifies the number of starboard horizontal stabilizer nodes that output is requested for (0 to 9) and SHSOutNd on the next line is a list NSHSOuts long of node numbers between 1 and NumSHSNds (corresponding to a row number in the starboard horizontal stabilizer node table, separated by any combination of commas, semicolons, spaces, and/or tabs. NPHSOuts specifies the number of port horizontal stabilizer nodes that output is requested for (0 to 9) and PHSOutNd on the next line is a list NPHSOuts long of node numbers between 1 and NumPHSNds (corresponding to a row number in the port horizontal stabilizer node table, separated by any combination of commas, semicolons, spaces, and/or tabs. NPylOuts specifies the number of fuselage nodes that output is requested for (0 to 9) and PylOutNd on the next line is a list NPylOuts long of node numbers between 1 and NumPylNds (corresponding to a row number in the fuselage node table, separated by any combination of commas, semicolons, spaces, and/or tabs. Outputs for a given pylon use the same output node numbers listed via NPylOuts.

The OutList section controls output quantities generated by KiteAeroDyn. Enter one or more lines containing quoted strings that in turn contain one or more output parameter names. Separate output parameter names by any combination of commas, semicolons, spaces, and/or tabs. If you prefix a parameter name with a minus sign, “-”, underscore, “_”, or the characters “m” or “M”, KiteAeroDyn will multiply the value for that channel by –1 before writing the data. The parameters are written in the order they are listed in the input file. KiteAeroDyn allows you to use multiple lines so that you can break your list into meaningful groups and so the lines can be shorter. You may enter comments after the closing quote on any of the lines. Entering a line with the string “END” at the beginning of the line or at the beginning of a quoted string found at the beginning of the line will cause KiteAeroDyn to quit scanning for more lines of channel names. Node-related quantities are generated for the requested nodes identified through the various ***OutNds lists above. If KiteAeroDyn encounters an unknown/invalid channel name, it warns the users and will mark the units of the suspect channel as Invalid. Please refer to the Appendix for a complete list of possible output parameters.

4.3.2.2.14. Airfoil Data Input File

The airfoil data input files themselves (one for each airfoil) include tables containing coefficients of lift force, drag force, and pitching moment versus AoA, as well as unsteady airfoil aerodynamic model parameters. In these files, any line whose first non-blank character is an exclamation point (!) is ignored (for inserting comment lines). The non-comment lines should appear within the file in order, but comment lines may be intermixed as desired for reading clarity. A sample airfoil data input file is given Section 4.3.5.

InterpOrd is the order the static airfoil data is interpolated when KiteAeroDyn uses table look-up to find the lift-, drag-, and optional pitching-moment, and minimum pressure coefficients as a function of AoA. When InterpOrd is 1, linear interpolation is used; when InterpOrd is 3, the data will be interpolated with cubic splines; if the keyword DEFAULT is entered in place of a numerical value, InterpOrd is set to 3.

NonDimArea is the nondimensional airfoil area (normalized by the local BlChord squared), but is currently unused by KiteAeroDyn. NumCoords is the number of points to define the exterior shape of the airfoil, plus one point to define the aerodynamic center, and determines the number of rows in the subsequent table; NumCoords must be exactly zero or greater than or equal to three. For each point, the nondimensional X and Y coordinates are specified in the table, X_Coord and Y_Coord (normalized by the local BlChord). The first point must always locate the aerodynamic center (reference point for the airfoil lift and drag forces, likely not on the surface of the airfoil); the remaining points should define the exterior shape of the airfoil. The airfoil shape is currently unused by KiteAeroDyn, but when KiteAeroDyn is coupled to MBDyn, the airfoil shape will be used by MBDyn for blade surface visualization when enabled.

Specify the number of Reynolds number- or aerodynamic-control setting-dependent tables of data for the given airfoil via the NumTabs setting. The remaining parameters in the airfoil data input files are entered separately for each table.

Re and UserProp are the Reynolds number (in millions) and aerodynamic-control (or user property) setting for the included table. These values are used only when the AFTabMod parameter in the primary KiteAeroDyn input file is set to use 2D interpolation based on Re or UserProp. If 1D interpolation (based only on angle of attack) is used, only the first table in the file will be used.

Set InclUAdata to TRUE if you are including the 32 unsteady airfoil aerodynamics model parameters. Because unsteady airfoil aerodynamics are not accounted for in KiteAeroDyn, these parameters are not further discussed here. See the OpenFAST AeroDyn module documentation for more information (AeroDyn is distinct from KiteAeroDyn).

NumAlf is the number of distinct AoA entries and determines the number of rows in the subsequent table of static airfoil coefficients; NumAlf must be greater than or equal to one (NumAlf = 1 implies constant coefficients, regardless of the AoA).

KiteAeroDyn will interpolate on AoA using the data provided via linear interpolation or via cubic splines, depending on the setting of input InterpOrd above. If AFTabMod is set to 1, only the first airfoil table in each file will be used. If AFTabMod is set to 2, KiteAeroDyn will find the airfoil table that bounds the computed Reynolds number, and linearly interpolate between the tables, using the logarithm of the Reynolds numbers. If AFTabMod is set to 3, KiteAeroDyn will find the airfoil table that bounds the computed control setting, and linearly interpolate between the tables, using the control settings.

For each AoA, you must set the AoA (in degrees), alpha, the lift-force coefficient, Coefs(:,1), the drag-force coefficient, Coefs(:,2), and optionally the pitching-moment coefficient, Coefs(:,3), but the column order depends on the settings of InCol_Alfa, InCol_Cl, InCol_Cd, and InCol_Cm in the AIRFOIL INFORMATION section of the KiteAeroDyn primary input file. AoA must be entered in monotonically increasing order—from lowest to highest AoA—and the first row should be for AoA = –180 and the last should be for AoA = +180 (unless NumAlf = 1, in which case AoA is unused).

4.3.2.2.15. Rotor Data Input File

The rotor data input file contains the rotor performance coefficient data as a function of rotor speed, inflow velocity, inflow skew angle, and collective-rotor blade pitch. Separate files are used for each unique rotor. A sample rotor data input file and the local rotor coordinate system is given in Section 4.3.5. The actuator disk is defined with local x normal to the disk (pointed forward, in the primary direction of flight) and positive rotation (Omega) about positive local x. The Vrel vector is always in the local x-y plane, and unless Skew is 0˚ or 180˚, the Vrel vector has a component along negative local y. Local z follows the right-hand rule. (That is, the local coordinate system rotates with the Vrel vector.)

The input file begins with two lines of header information which is for your use, but is not used by the software.

NumOmega specifies the number of rotor rotational speeds, NumVrel specifies the number of relative inflow velocities, NumSkew specifies the number of skew angles, and NumPitch - specifies the number of pitch angles. Therefore, the data table will contain NumOmega X NumVrel X NumSkew X NumPitch lines (plus two table header lines). Each of these values must be >= 2. The rotor table data contains 11 columns (in the following order, from left to right):

  • Omega specifies the rotor rotational velocity (rad/s);

  • Vrel specifies the inflow wind speed (m/s);

  • Skew specifies the skew angle (angle between local x and VRel vector, positive angle about positive local z, in degrees and should be between 0 and 180 degrees (inclusive));

  • Pitch specifies the collective-rotor blade pitch angle (in degrees);

  • C_Fx specifies the thrust (x) force coefficient for the given operating conditions, with normalization factor, :math: rho D^4 (omega/(2 pi))^2;

  • C_Fy specifies the transverse (y) force coefficient for the given operating conditions, with normalization factor, :math: rho D^4 (omega/(2 pi))^2;

  • C_Fz specifies the transverse (z) force coefficient for the given operating conditions, with normalization factor, :math: rho D^4 (omega/(2 pi))^2;

  • C_Mx specifies the torque (x) coefficient for the given operating conditions, with normalization factor, :math: rho D^5 (omega/(2 pi))^2;

  • C_My specifies the transverse (y) moment coefficient for the given operating conditions, with normalization factor, :math: rho D^5 (omega/(2 pi))^2;

  • C_Mz specifies the transverse (z) moment coefficient for the given operating conditions, with normalization factor, :math: rho D^5 (omega/(2 pi))^2 ;

  • C_P specifies the power coefficient for the given operating conditions, with normalization factor, :math: rho D^5 (omega/(2 pi))^3;

The table must be constructed such that the Omega dependent variable varies most frequently, followed by Vrel, and so forth, through the Pitch dependent variable which varies the least frequently.