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).

Since this facility anticipates the comparison of existing blades (in addition to blades designed in XROTOR), the new IMPO command imports blade geometries from text files, which can be more efficient than terminal input (ARBI) when measuring physical blades.

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). ESLOFTX is a very useful tool for anyone wanting to build, model or mesh rotor blade designs originating in XROTOR.

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

CRotor755es10b.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 Unix/Linux/OSX with X11 support and C and Fortran compilers. Building on Windows can be done but has not been tested and may require work. (A gfortran binary with installer for Mac OSX can be downloaded here.)

CROTOR 755-ES1.0b is a full featured beta version. Please report bugs.

Download CRotor755es10b.tar.gz (1.2MB)

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

Versions

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

Sample Plots