Order your copy of Public Domain Computer Programs for the Aeronautical Engineer. Last updated: 30 September 2002 by Ralph Carmichael ralph@pdas.com
Public Domain Aeronautical Software
P.O. Box 1438 Santa Cruz CA 95061 USA
The input file for PanAir is error-prone and unforgiving. This program accepts a free-form file and creates a properly formatted input file for PanAir.
The program referred to as A502 is a pilot version of the production computer code known as PANAIR. Both PANAIR and A502 were developed by the Boeing Company under contract to the NASA Ames Research Center. The contract was funded by several agencies of the Department of Defence along with NASA Ames and Langley Research Centers.
These programs solve for the fluid flow about an arbitrary configuration at subsonic or supersonic speeds, using linearized potential flow theory. The A502 code was never intended for wide distribution and only modest efforts were made to document the input file format and explain the usage of the program. Recent developments have led to the more widespread use of A502 and the program must become available to a greater number of users. The purpose of this paper and the computer program it describes is to make the A502 version of PanAir accessable to a users in a simple fashion.
The input to A502 is described in the user's manual which is found on the disc. The input data is organized in specific columns. Editing an input file is a rather error-prone process. The PANIN program was written to enable a user to select the flow properties and all other program options by editing a short free-format file called an auxiliary file. One entry in the auxiliary file is the name of a file that contains the geometrical information. The format of this file is that of the NASA standard for wireframe geometry as described in reference 2. This file is usually referred to as a WGS file, standing for Wireframe Geometry Standard. The program reads the various items of control information from the auxiliary file and combines this information with the panel geometry in the WGS file to produce a combined file that is a properly formatted input file for PanAir.
The first and most difficult part of preparing a case for PANAIR or any panel code is the definition of the surface geometry as a set of quadrilateral panels. A variety of techniques exist for the creation of this data. A program call MAKEWGS in this collection is available for definition of simple geometries. Those familiar with the geometry programs in use at Langley may find it preferable to use QUICK or GEMPAK to produce inputs. The ultimate solution lies in the use of a Computer-Aided-Design (CAD) system that has a wireframe output option. There is a program A502WGS that will convert A502 input decks to WGS.
All input to PanAir other than the geometry definition or off-body xyz-points is contained in the auxiliary file. **** REWRITE THAT **** Each records in the auxiliary file starts with a key word. The key word may be upper or lower case and may be preceeded by blanks. The key word is usually followed on the same record with a numeric value which is the value of the variable described by the key word. For some key words, a series of numerical values follows while for others no values are required. Comments may be added to a record after the necessary data. Comments may be added after the numeric value for most of the keywords.
Currently the keywords are:
ABUTPR
ALPC compressibility angle of attack, degrees
ALPHA list of angles of attack (degrees) (max of 4)
AVERAGE if any networks are modelled as thin surfaces they are
listed on this record
BETA list of angles of sideslip (degrees) (max of 4)
BETC compressibility angle of sideslip
BOUN the boundary conditions to be applied to each network.
This will be a list of KT values, one for each network.
However, if any network has KT=30, the number 30 must be followed
by 4 additional boundary condition inputs. A value of -18 is used for
the special case of fuselage base wake, or wakes that abut other wakes.
BWAKE followed by 3 numbers to define a body edge wake network.
This is also used for wakes attached to upstream wakes.
The first is the network to which the wake is attached; the second is the
edge number to which it is attached; third is the x-coor of downstream edge.
CBAR length of the reference chord
CHECK =0 for a full run; =1 to stop after computing abutments.
CUTS name of a file that has a list of plane definitions
each record has 6 numbers, 3 for point, 3 for normal
EAT abutment tolerance
FORCE list of networks to be used for calculation of configuration
force and moment summary. If this record is not present, the
default is to use all thnetworks that have kt=1 boundary conditions.
GRID definition of an off-body grid. There must be 9 numbers
following the keyword GRID and they must be on the same record.
The nine items are (xorigin, yorigin, zorigin), (dx,dy,dz), and
(nx,ny,nz).
HMIN min step size for streamlines
HMAX max step size for streamlines
ISINGS =1 to print singularity data; =0 to suppress
IGEOIN =0 to print network geometry before liberalized abutment mods
=-1 to suppress this printout
IGEOUT =0 to NOT print network geometry after liberalized abutment mods
=1 to print this information
IGEOMP =1 to print geometry diagnostic data; =0 to suppress
ISINGP =1 to print singularity spline data; =0 to suppress
ICONTP =1 to print control point loc, normals; =0 to suppress
=2 to print upper surface normal only
IBCONP =1 to print boundary condition diagnostic data; =0 to suppress
IEDGEP =1 to print edge-matching diagnostic data; =0 to suppress
IPRAIC =1 to print control point sequence number; =0 to suppress
IOUTPR =-1 to omit flow parameter output
=0 to output 48 flow parameters
=1 to output 12 flow parameters
IFMCPR =-1 to omit network force and moment output
=0 to output network force,moment summary per col, per net, accum
=1 to output network force,moment summary per net and accumulation
IGNORE if any networks are not to be included in the force and moment
calculations, they are listed on this record.
IVCORR =1 to apply the McLean velocity correction
=2 to apply the Boctor velocity correction
=0 to make no corrections
MACH free stream Mach Number
MAXSTREAM maximum number of points along any single streamline (default 100)
MNSWITCH (may also be spelled MNSWCH) any networks that should have rows
and columns interchanged are listed on this record
NEXDGN =1 to print edge control point data; =0 to suppress
NOF do not add trailing filaments for Trefftz plane drag analysis
OFFNETS list of networks used for calculation of off-body velocities or
streamlines. Default is to use all networks.
PEA [not implemented yet]
PRECISION number of decimals printed in all fields of the a502 input
file produced by this program.
RESTART if the job has been run previously with a SAVE and there are
files on the CSF archive, the job may be restarted without
recomputation of the aerodynamic matrix.
=1 if additional angles of attack or sideslip are to be done
=2 if the same angles are used
SPAN reference span
SREF reference area
STREAM name of a file that has a list of (x,y,z) (dx,dy,dz) triples
six numbers per record
SYMM =0 for asymmetric configuration; =1 for symmetric
TITLE1 a title that appears on the printed output
TITLE2 second line of the title
UPSTREAM streamlines go upstream instead of downstream.
WAKE followed by 3 numbers to define a trailing edge wake network.
The first is the network to which the wake is attached; the second is the
edge number to which it is attached; third is the x-coor of downstream edge.
WGS name of the WGS file
XREF x-coordinate of the moment reference point
XYZ name of a file which has a list of (x,y,z) triples, defining the
off-body points at which velocities are to be computed.
one triple per record.
YREF y-coordinate of the moment reference point
ZREF z-coordinate of the moment reference point
no changes in angles or Mach number, this commands a restart.
The principal use is for off-body points.
In order to make the creation of this auxiliary file as simple as possible, all of the keywords have preset defaults which are used if the user does not supply a value. For many of the items, the default value will be the desired value and the auxiliary file can be quite short. The following items all have default values of 0: MACH, XREF, YREF, ZREF, ALPC, BETC, ALPHA, BETA, ISINGS, IGEOMP, ISINGP, ICONTP, IBCONT, IEDGEP, IPRAIC, NEXDGN, IOUTPR, IFMCPR, IVCORR, IGEOIN, IGEOUT, CHECK. The quantities SREF, CBAR, SPAN, and SYMM have default values of 1.0 and MAXSTREAM has a default value of 100. HMIN defaults to 0.1 anf HMAX to 0.5. TIME has a default value of 100 and NAME is given the string "A502". The keywords MNSWITCH, FORCE, IGNORE, and AVERAGE refer to lists of network numbers. If any of these are not specified, the list is taken to have no members. If XYZ or STREAM is not included in the auxiliary file, then no off-body points or streamlines will be computed.
Once the WGS geometry file and the auxiliary file have been created and stored, the PanAir input file is created by invoking the program panin.
After the panin program has completed execution, two files have been produced. These files take their names from the data in the NAME record in the auxiliary file with extensions of .sh and .in. For example, if the record in the auxiliary file is NAME mycase, then the two files produced are mycase.in and mycase.sh. The .in file is the a502 input data.
The dataset shown here is a sample case
NAME owra45 TIME 550 WGS owra45b.wgs ( version with modified nose ) TITLE1 Oblique Wing Research Airplane Ames 86 concept (250 sq. ft) TITLE2 Sweep=45 CHECK 0 symm 0 ( no symmetry ) ioutpr -1 ( do not print surface pressures ) ifmcpr 1 ( short print ) cbar 5.34 span 50 sref 250 ( small wing; new one has 300 ) xref 37.292 mach 0.9 alpc 5 ( average value for alpha values ) alpha 4 5 6 eat 0.0001 ignore 7 8 9 10 average 23 24 25 26 27 31 32 BOUN 1 1 1 1 1 1 5 5 5 5 1 1 1 1 1 1 18 18 18 18 18 18 2 2 2 2 2 18 18 18 2 2 18 18 18 18 18 18 18 18
This job expects to find a file called owra45b.wgs in the current directory. The wgs file should contain 40 networks. Networks 7-10 are base nets and 17-22, 28-30, and 33-40 are trailing edge wake nets. Nets 23-27 and 31-32 are surfaces of zero thickness and their forces and moments are computed from the delta-Cp across the panel. Two files named owra45.sh and owra45.in will be produced in the current directory.
Although a considerable effort has been expended in making the program free of errors or ommisions, the user should inspect the input file and script carefully. There are many problems in forcing data to fit the fixed field format and inadvertent roundoff may result. The PRECISION keyword can be helpful, but there are many potential sources of error. The principal problem area is overflow of an output field when one is trying to keep the geometric accuracy high by printing many decimals. Two popular places for this error to occur are the x-coordinates of the trailing edges of wakes and the value of reference area. It is usually useful to scan the PanAir input file for asterisk characters.
There are many options in the PanAir input file and it would be virtually immpossible to incorporate all of them in this program. For example, in PanAir you can select different reference lengths for yawing momemt and rolling moment. PanIn simply asks for SPAN. And there are lots more.