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Polar Exchange Format (PEF)

Contents

Purpose of PEF-Files

The Polar Exchange Format (PEF) has been designed as a means to exchange airfoil data between different applications. While it was not intended primarily as an efficient storage format, it can be used to store and access airfoil and aircraft polars from performance calculation and flight mechanics computer programs. The data is organized in polars, which contain values for a range of angle of attack values. A PEF file can contain several polars, e.g. for different Reynolds numbers, which may be grouped in data sets, e.g. from different sources like wind tunnel and calculation. One PEF file usually contains data for one airfoil geometry. (PEF files can be imported and exported e.g. by the commercial software WINPROF from Wiechers, Puchheim, Germany).

Structure of a PEF-File

A PEF file is written in a simple, but case dependent ASCII format. It contains several blocks of information, whose sequence is free. Each block is identified by a heading, which is enclosed in square brackets ([]). Inside each block several key-value pairs are specified by the key word, followed by an equal sign, followed by the value(s). The sequence of these key-value pairs is arbitrary, so that readers should seek from the start of a block to locate a key. Comment lines, with a ';' character in the first column, can be inserted.

Based on this block structure, a PEF reader can lookup any desired information from the file, when he has read the [Airfoil] block and the [Setn] blocks described below.

[Airfoil]
Description1=briefly identifies the airfoil or the geometry {MANDATORY}
NumberSets=the number of data sets to follow {MANDATORY}

[Setn] n: number of data set, counting from '1'
Origin=source of this data set
Description1=description of the data set
NumberPolars=number of polars in this data set {MANDATORY}

[Setn-Polarm] n: number of data set, m: number of polar, counting from '1'
ReynoldsNumber=the Reynolds number of the first polar
MachNumber=the Mach number of the first polar
Description1=may contain a description of this specific polar
NumberPoints=number of data points in this polar {MANDATORY}
Values=Alpha Cl Cd Cm xtu xtl (recommended default sequence of values)
Value01= the values for the first data point {MANDATORY}
Value02= the values for the second data point {MANDATORY}
Value03= the values for the third data point {MANDATORY}

Sample Readers and Tools


PEFParser
This PEFParser can be compiled with a C-compiler.
Download a sample C-source file (size: 5 kB), which parses a PEF file.

PEFParser
This PEFParser can be compiled with a FORTRAN-77-compiler.
Download a sample FORTRAN-source file (size: 12 kB), which parses a PEF file.

PEFBrowser
If you own an IBM-PC running MS-DOS/Windows 3.1, you can use the PEFbrowser application to check and display PEF files.
Download
a self extracting LZH archive (size: 11 kB), including Visual Basic 2.0 source. You will also need the Visual Basic runtime library VBRUN200.DLL, which is not included in this archive, but should be available somewhere near you on the internet:

DRGtoANY
This converter can be compiled with a C-compiler. It converts .drg polar files from the UIUC wind tunnel campaign to PEF files.
Download a self extracting LZH archive (size: 37 kB), including C source and an executeable for Microsoft Windows 3.1.

PEFview

V 2.0

This utility program for Windows 9x and Windows NT has been developed from PEFbrowser. It can read, display, print and convert various airfoil polar file formats. It reads PEF, POL and DRG files, writes PEF, POL and EPP files and can be used to sort and combine different polar sets. The program has been rewritten in VisualBasic 6.0, which makes the archives uncomfortably large, and you need Windws 95 or later. The program can now also handle UNIX style PEF files, with lines terminated by a line feed character (ASCII 10) only, not the DOS/Windows CR/LF (ASCII 10/13) pair.
Download the ZIP archives of pefview1.zip (1339 kB) and pefview2.zip (631 kB).

File Format

Description
PEF see this page
POL XFoil 5.4 polars
DRG UIUC and Princeton experiments
EPP Eppler input file (export only, to plot polars with Epplers airfoil program)

MWK

Modellwindkanal University of Stuttgart (of local interest only)

XML

Extensible Markup Language (maybe I should convert my files to this more general format)

Example of a PEF-File

[Airfoil]
Description1=MH 60
NumberSets=2

[Set1]
Origin=Calculation: X-Foil
Description1=Part of 'Profile für Nurflügelmodelle'
NumberPolars=2

[Set1-Polar1]
ReynoldsNumber=100000
Description1=Copyright © 1995-1996 Martin Hepperle
NumberPoints=31
Values=Alpha Cl Cd Cm xtu xtl
Value01= -3.50 -0.382 0.02217 -0.0036 0.8026 0.0534
Value02= -3.00 -0.312 0.01917 -0.0060 0.8001 0.2709
Value03= -1.50 0.118 0.01675 -0.0488 0.8040 0.8507
...
[Set1-Polar2]
...
[Set2]
Origin=Experiment, Stuttgart
Description1=Part of 'Profile für Nurflügelmodelle'
NumberPolars=3

[Set2-Polar1]
...
[Set2-Polar2]
...
[Set2-Polar3]
...

last modification of this page: 13.04.01

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