Comparison of the results of numerical simulation of flow around the helicopter rotor in a variety of software

Design, construction and manufacturing of flying vehicles


Аuthors

Vershkov V. A.1*, Kritsky B. S.1**, Makhnev M. S.1***, Mirgazov R. M.1****, Trebunskikh T. V.2*****

1. Central Aerohydrodynamic Institute named after N.E. Zhukovsky, TsAGI, 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia
2. Mentor Garphics Development Services Ltd, 10, Shabolovka Street, room 2, Moscow, 119049, Russia

*e-mail: vershkov.va@gmail.com
**e-mail: boris.kritsky@tsagi.ru
***e-mail: spintest@tsagi.ru
****e-mail: ruslan.mirgazov@tsagi
*****e-mail: Tatiana_Trebunskikh@mentor.com

Abstract

The results of numerical flow simulation around the helicopter rotor have been obtained in commercial programs FloEFD, Ansys Fluent, RC-VTOL are presented in article. The program RC-VTOL was developed in TsAGI.

The main aim of the article is to compare the program’s features and requirements. The conclusions are made about the software usability to solve problems concerning the helicopter rotor.

The main features of the program FloEFD are the automatic grid generator, which build a Cartesian grid adapted to the body, and the turbulence model using a «Two-Scale wall functions.» RC-VTOL is based on the nonlinear vortex blade theory. The blade is modeled as infinitely thin surface. Vortices are trailed from the sharp trailing edges of each rotor blade. Therefore, for the calculation it is not necessary to build a three-dimensional grid, which may cause a numerical error.

The validation of the program FloEFD was made at the first stage of calculations. For its validation the Caradonna and Tung benchmark for rigid two-blade rotor are used. The hover mode with the rotation frequency n = 2500 RPM was considered. The numerical data were compared with the results obtained in the program NUMECA FINE/Turbo. The comparison shows satisfactory agreement between calculations in commercial programs and experiment.

The horizontal flight regime (V∞ = 11.5 m/s) was discussed at the second stage. The experiment was made by L.S. Pavlov in a wind tunnel TsAGI T-105. The rigid one- and four-bladed rotor with a frequency n = 348.5 RPM was considered as the object of experiment.

Calculations were made in three different software packages: FloEFD, ANSYS Fluent and RC-VTOL. Analysis of the results, based on the calculation of the speed and accuracy of the results, shows the advantages and disadvantages of each program. The RC-VTOL program required 10 minutes for creating a numerical model of the rotor and the numerical grid and 20 minutes for the calculation of each case. The calculation in ANSYS Fluent took about 48 hours to simulate each case and about seven days to set up the project and the calculation mesh. Setting up the model and generating the mesh size of about 2.7 million cells in the program FloEFD took about 35 minutes and about 36 hours for the calculation.

The results show satisfactory and in some modes good agreement with the experimental data in all software its mean about their suitability for the calculation of the helicopter main rotor.

Keywords:

main rotor, aerodynamic characteristics, numerical methods, CFD software

References

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