XROTOR on Steroids

Download CROTOR
Sample Plot Output
Join the DFDC/XROTOR eGroup

Previously a commercial code, the venerable aero/hydrodynamic rotor design & analysis application XROTOR was released under the GPL in early 2011. Kudos to Prof. Mark Drela and Hal Youngren for this eminently useful code, and to all whose decision it was to release it to the community.

XROTOR has been an essential part of my design toolbox since the mid 1990s. Over the years I've written various codes to address specific needs in XROTOR and these have gradually developed into useful facilities. With the XROTOR code now open source, these facilities have been integrated into the GPL release (v7.55) along with a couple of features ported from DFDC 070-ES2. With the source directory growing by some 70 percent (including some XFOIL code) the package is dubbed CROTOR to distinguish it from its parent.

CROTOR v755-ES1 is all of XROTOR 7.55 plus the following:

Counter-Rotation Facility

If you have ever tried converging a counter-rotation case in XROTOR you will know how clumsy and tedious the process can be. Subroutine CROTOR automates this procedure while providing an effective user interface and reporting. The result is a flexible and robust counter-rotation design/analysis facility. Anyone working with counter-rotating rotors will want to check out this code.

Multi-Axis Parametric Analysis

Subroutine ESPARA is one half of a parametric analysis system originally developed for a propeller company using third party blades in their electric constant speed hubs. Their problem was: what blades should they use for a particular engine/airframe? ESPARA makes multi-axis parameter sweeps and stores data in a multi-rotor database to be displayed and plotted with great flexibility in a standalone utility called ESPROP. This facility is intended for practical applications in the field, selecting propellers for real world applications by directly comparing them over any operating range within the database bounds. Currently only variable pitch props are supported (though support for fixed pitch is planned by calculating on the same database).

Blade Lofting Facility

You have your rotor design completed in XROTOR - then what? You have three lists of numbers representing the geometry of the blade (radius, chord, blade angle), which somehow have to be translated into a 3D shape, a process not as simple as it might seem. Subroutine ESLOFTX is a port and further development of ESLOFT for DFDC, allowing rotor designs to be explicitly defined in three dimensions and exported into CAD for 3D modeling, meshing or manufacture. Support has been added for round tips, along with splined thickness or thickness/chord distributions (in addition to linear and parabolic distributions). Version ES1.1 adds circular root blends, important for windmills and constant speed propellers. ESLOFTX is a very useful tool for anyone wanting to build, model or mesh rotor blade designs originating in X/CROTOR.

Multi-Re Plotting in AERO

If setting the REexp parameter in AERO has sometimes seemed like guesswork, it is no more. In addition to polar plots at multiple Mach numbers, AERO now supports plotting at multiple Reynolds, providing precise feedback on the effects of REexp.

Download CROTOR v755es1.1

Available under the terms of the General Public Licence. By downloading the software you agree to abide by the GPL conditions.


CRotor755es11.tar.gz includes the complete XROTOR 7.55 package along with additional source modules, sample cases, airfoil files and documentation. ESPROP 0.8 is included in the build. Requires X11 support and C and Fortran compilers.

Download CRotor755es11.tar.gz (1.1 MB)


This archive contains CRotor755es11 and:
- 32 bit binaries for Windows
- modified plotlib
- makefiles for Mingw Gcc4.52
- workspace and projects to edit files with Visual Studio

Thanks to JP Balza for this build.

Download CRotor755es11_win32.7z (1.5 MB)

Documentation (text format, included in package)
CROTOR User Guide
ESLOFTX User Guide
ESPARA User Guide
ESPROP User Guide


4 April 2014

Windows package CRotor755es11_win32.7z posted.

18 January 2014

CROTOR version 755-ES1.1 posted. Following very quickly after v1.0, one new feature in vES1.1 is too useful to keep all to myself. If you need to blend blade geometries to circular root sections, ESLOFTX now does this with quality and ease (see image below).

6 January 2014

CROTOR version 755-ES1.0 posted. Along with a variety of bug fixes, this version introduces automatic inversion of windmill airfoils in ESLOFT.

22 October 2011

CROTOR version 755-ES1.0b and this page posted.

Sample Output

Click for larger images...

Circular root blend in SolidWorks out of ESLOFTX
Counter-rotating system
Average induced velocities
Round tip loft in ESLOFTX Round tip panel refinement

Multiple Re plotting in AERO Round tip transformed sections

DFDC (& XROTOR) eGroup

Despite their different architectures XROTOR and DFDC have much in common and even share some code. Consequently this forum embraces both XROTOR and DFDC and their derivatives.

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© Copyright 2014 Philip Carter