Methodical specifics of numerical simulation of a flow field near the rotor at a hover mode within the framework of computational grid methods with regard to vortex structure

Aerodynamics


Аuthors

Vershkov V. A.1*, Voronich I. V.2**, Vyshinsky V. V.2***

1. Central Aerohydrodynamic Institute named after N.E. Zhukovsky, TsAGI, 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia
2. Moscow Institute of Physics and Technology, 9, Institutskiy per., Dolgoprudny, Moscow region, 141701, Russia

*e-mail: vershkov.va@gmail.com
**e-mail: voronich.iv@mipt.ru
***e-mail: vyshinsky@falt.ru

Abstract

A numerical simulation technique of a flow over a lifting rotor in hover mode is considered within the framework of Numeca FINE/Turbo software. For its validation, the test experiments by Caradonna and Tung for rigid 2-blade rotor are used.

This work is aimed at systematization of the factors determining accuracy of numerical solution for flow over lifting rotor problem, and testing numerical technique, which has a potential to attain an industrial applicability.

The main conclusion based on the review of present-day works lies in the priority of adaptation of computational grid in the area of vortexes. Resolution of tip vortexes at the scope of one rotation is sufficient for getting reliable values for pressure distribution coefficients and integral characteristics at hover.

The system of Reynolds averaged Navier-Stokes equations closed with Spalart-Allmaras and SST turbulence models was used as model of gas motion. The entire computational domain containing rotor blade is considered in rotating coordinate system with the terms responsible for action of the centrifugal and Coriolis forces taken into account. The numerical method is built on the basis of central differences scheme with artificial viscosity and local time stepping technique. The multigrid technology was used for its acceleration. Calculations in non-stationary formulation were performed to verify the obtained results.

Structured multi-block grids of H-topology with O-layer around blades generated semi-automatically with adaptation to boundary layer and vortex system region were used for calculations. Resolution of boundary layer by grid was ensured at the level y+ < 1 throughout the whole blade span (on average y+~0.1).

For evaluation of industrial suitability of numerical techniques criterion we proposed the criterion based on accuracy of pressure coefficient surface distributions: |δCp|<0.05. It corresponds to the typical experimental data error and ensures reasonable accuracy of integral characteristics.

Obtained numerical results stay in satisfactory agreement with experimental data. The structure of streamlines is in agreement with theoretical considerations. Coordinates of tip vortex correspond to Kocurek-Tangler model up to angular size of γ @ 360°.

Keywords:

main rotor, aerodynamic characteristics, numerical methods, Numeca FINE/Turbo

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