Guidelines_v604_en.pdf

(1286 KB) Pobierz
Analysis of foils and wings
operating at low Reynolds numbers
28/02/2013
1
XFLR5 v6.02 Guidelines
Contents
1 Purpose
2 Introduction
2.1 Code limitations and domain of validity
.
2.2 XFLR5’s development history
. . . . . .
2.3 Changes introduced in XFLR5 v6
. . . .
2.3.1 Problem size
. . . . . . . . . . . .
2.3.2 Stability and control analysis
. .
2.3.3 Batch calculations
. . . . . . . .
2.3.4 3D panel method
. . . . . . . . .
2.3.5 Inertia estimations
. . . . . . . .
2.4 Code structure
. . . . . . . . . . . . . .
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3 Foil Analysis and Design Modes
3.1 General
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3.2 Direct Analysis [Oper]
. . . . . . . . . . . . . . . . . . . . . .
3.2.1 Foil object
. . . . . . . . . . . . . . . . . . . . . . . . .
3.2.2 Foil Modification
. . . . . . . . . . . . . . . . . . . . .
3.2.3 Analysis/Polar object
. . . . . . . . . . . . . . . . . . .
3.2.4 Operating Point (OpPoint) object
. . . . . . . . . . . .
3.2.5 XFoil analysis
. . . . . . . . . . . . . . . . . . . . . . .
3.2.6 XFoil errors
. . . . . . . . . . . . . . . . . . . . . . . .
3.2.7 Session example Direct Analysis
. . . . . . . . . . . . .
3.3 Full Inverse Design [MDES] and Mixed Inverse Design [QDES]
3.3.1 General
. . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.2 Session example – Full Inverse Design
. . . . . . . . . .
3.3.3 Session example – Mixed Inverse Design
. . . . . . . .
3.4 Foil Direct Design
. . . . . . . . . . . . . . . . . . . . . . . . .
3.4.1 General
. . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.2 B-splines main features
. . . . . . . . . . . . . . . . . .
3.4.3 Spline Points main features
. . . . . . . . . . . . . . .
3.4.4 Leading and trailing edge
. . . . . . . . . . . . . . . .
3.4.5 Output precision
. . . . . . . . . . . . . . . . . . . . .
3.4.6 Digitalization
. . . . . . . . . . . . . . . . . . . . . . .
4 3D Analysis
4.1 Wind and body axis, sign conventions
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4.2 Object Definition
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4.2.1 Wing Definition
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4.2.2 Reference area for aerodynamic coefficients
4.2.3 Flaps
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4.2.4 Body Design
. . . . . . . . . . . . . . . . .
4.2.5 Plane Definition
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4.2.6 Inertia estimations
. . . . . . . . . . . . .
4.2.7 Mesh
. . . . . . . . . . . . . . . . . . . . .
4.2.8 Symmetry
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4.3 Performance analysis
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2
April 1, 2013
4.3.1 Theory - General
. . . . . . . . . . . . . . . . . . .
4.3.2 Viscous and inviscid calculations
. . . . . . . . . .
4.3.3 Lifting Line Theory (LLT) - Non Linear
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4.3.4 Vortex Lattice Method (VLM) - Linear
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4.3.5 3D Panel Method - Linear
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4.3.6 Analysis considerations
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4.3.7 Moments
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4.3.8 Neutral point, Center of pressure, Static Margin
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4.3.9 Efficiency factor
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4.3.10 Wing Operating Points and Wing Polars
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4.3.11 Control analysis – Polar Type 5 and Type 6
. . . .
4.3.12 Interpolation of the XFoil-generated Polar Mesh
. .
4.3.13 Streamlines
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4.3.14 Comparison to experimental results
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4.3.15 Comparison to wind tunnel data
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4.3.16 Comparison to Miarex and AVL results
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4.3.17 Session example – Wing Analysis
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4.3.18 Non convergences
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4.4 Stability and control anaysis
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4.4.1 Method
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4.4.2 Theory
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4.4.3 Frames of reference
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4.4.4 Coordinates, position, velocity, and rotation vector
4.4.5 Flight constraints
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4.4.6 State description
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4.4.7 Analysis procedure
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4.4.8 Input
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4.4.9 Output
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4.4.10 Session example – Stability analysis
. . . . . . . . .
5 Code Specifics
5.1 XFoil, AVL and XFLR5
.
5.2 Files and Registry
. . . . .
5.3 Shortcuts
. . . . . . . . .
5.4 Mouse input
. . . . . . . .
5.5 Memory
. . . . . . . . . .
5.6 Export Options
. . . . . .
5.7 Bugs
. . . . . . . . . . . .
5.8 Open Source Development
6 Credits
7 References
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3
XFLR5 v6.02 Guidelines
1
Purpose
This document is not intended as a formal help manual, but rather as an aid in using
XFLR5. Its purpose is to explain the methods used in the calculations, and to provide
assistance for the less intuitive aspects of the software.
2
2.1
Introduction
Code limitations and domain of validity
Like the original XFoil, this project has been developed and released in accordance with
the principles of the GPL. Among other things, one important point about GPL is that :
This program is distributed in the hope that it will be useful, but WITH-
OUT ANY WARRANTY; without even the implied warranty of MERCHANTABIL-
ITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
Public License for more details.
The code has been intended and written exclusively for the design of model sailplanes,
for which it gives reasonable and consistent results. The code’s use for all other purpose,
especially for the design of real size aircraft is strongly disapproved.
2.2
XFLR5’s development history
The primary purposes for the development of XFLR5 were to provide :
•
A user-friendly interface for XFoil
•
A translation of the original FORTRAN source code to the C/C++ language, for
all developers who might have a need for it
This was done in accordance with, and in the spirit of, Mark Drela’s and Harold Youn-
gren’s highly valuable work, which they have been kind enough to provide free of use
under the General Public License.
The resulting software is not intended as a professional product, and thus it does not offer
any guarantees of robustness, accuracy or product support. It is merely a personal use
application, developed as a hobby, and provided under GPL rules for use by all.
For this reason, it should be noted and understood that XFLR5 may not be default-free.
Some significant bugs affecting result precision have been reported in the beta releases
and corrected.
However, XFLR5 has been thoroughly tested against other software and published exper-
imental results, up to now with some success, and this permits a limited amount of trust
in the results it provides.
The algorithms for foil analysis implemented in XFLR5 are exactly the same as those
of the original XFoil code, except for the translation from FORTRAN to C. No changes
nor amendments have been made. The translation in itself could have caused new bugs.
However, the code has been thoroughly tested against numerous original XFoil analyses,
always with consistent results. It may be found, in some cases, that one of the two
programs may not converge where the other will, or that the path to convergence is
4
April 1, 2013
different from one to the other. This is due to the different manner in which floating
point numbers and calculations are processed by the two compilers. Having said this, the
converged results are always close, and any differences within the convergence criteria set
in the XFoil source code.
Hence, both XFoil and XFLR5 results of airfoil analysis will be referred to herein as
”XFoil results”.
Wing analysis capabilities have been added in version 2.00. Initially, this was done at the
suggestion of Matthieu Scherrer, who has experimented with his Mathlab ”Miarex” code
the application of the Non-linear Lifting Line Theory (herein referred to as ”LLT”) to the
design of wings operating at low Reynolds numbers.
Later on, the necessity arose to add the Vortex Lattice Method (herein referred to as
”VLM”) for the design and analysis of wings with geometries not consistent with the
limitations of the LLT.
Version v3.00 introduced Katz and Plotkin’s recommended VLM method based on quadri-
lateral rings, and the VLM calculation of planes with elevator and fin.
On March 31
st
, 2007, XFLR5 has become an Open Source Development Project hosted
by Sourceforge.net.
Version v4.00 introduces a 3D panel method for wings and planes, including modeling
options for fuselages.
Up to this last version, XFLR5 has been developed specifically for Windows, using Mi-
crosoft’s MFC libraries. This is a limitation of the product, making it non available for
Unix, Linux, and MAC systems. It has therefore been decided to re-write the code using
the cross-platform Qt4 libraries provided by Nokia. This version has been released as
XFLR5 v5. It does not offer any new functionality compared to the original code.
Released in a beta version in September 2010, XFLR5 v6 introduces the stability and
control analysis, and a modification of the 3D-panel method for the plane.
2.3
2.3.1
Changes introduced in XFLR5 v6
Problem size
The maximum acceptable size for mesh definitions has been increased from 2000 panels
to 5000 panels max.
Since the memory allocation increases as the square power of the problem size, this new
version will reserve more memory at the program launch, and may take longer to start
on those computer with low RAM.
2.3.2
Stability and control analysis
”Control polars” have been replaced by ”stability polars”, with evaluation of stability and
control derivatives.
2.3.3
Batch calculations
It is now possible to run a batch calculations for a list of airfoils.
2.3.4
3D panel method
The 3D panel method is now processed differently for single wings and for planes.
5

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