Towards In-Flight Measurements of Helicopter Blade Tip Vortices

Flow field around a marine propeller was measured by means of PIV technique in a large cavitation tunnel of the Naval Systems Research Center, TRDI/Ministry of Defense, Japan. Test section of the tunnel is 2m(W) × 2m(H) × 10m(L) and it contains 2000m3 of water. 2-dimensional PIV (2-D PIV) and stereo PIV (SPIV) measurements were made for a five-bladed highly skewed marine propeller. In the case of 2-D PIV measurements, high spatial resolution measurements were possible by seeding relatively small amount of tracer particles. Phase-averaged flow fields showed details on evolution of tip vortices. In the case of SPIV measurements, much larger amounts of tracer particles were required, and it was difficult to perform high resolution measurements. Phase averaged velocity profiles from SPIV measurements showed good agreement with 2-D PIV-measured results. PIV-measured results were compared with results of LDV measurements. Although PIV-measured velocity profiles showed fairly good agreements with LDV-measured results, some discrepancies were found at the blade tip region.

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Tracking Blade Tip Vortices for Numerical Flow Simulations of Hovering Rotorcraft

2018 AIAA Aerospace Sciences Meeting ◽

10.2514/6.2018-1175 ◽

2018 ◽

Author(s):

David L. Kao ◽

Katherine L. Smith ◽

Zhanping Liu

Keyword(s):

Tip Vortices ◽

Flow Simulations ◽

Blade Tip

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Turbulence Measurements inside Blade Tip Vortices Using Dual-Plane Particle Image Velocimetry

Journal of the American Helicopter Society ◽

10.4050/jahs.55.042007 ◽

2010 ◽

Vol 55 (4) ◽

pp. 042007

Author(s):

Bradley Johnson ◽

Manikandan Ramasamy ◽

J. Gordon Leishman

Keyword(s):

Particle Image Velocimetry ◽

Particle Image ◽

Tip Vortices ◽

Turbulence Measurements ◽

Dual Plane ◽

Image Velocimetry ◽

Blade Tip

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Tip Running Clearances Effects on Tip Vortices Induced Axial Compressor Rotor Flutter

Volume 6: Structures and Dynamics, Parts A and B ◽

10.1115/gt2011-45504 ◽

2011 ◽

Cited By ~ 1

Author(s):

Caetano Peng

Keyword(s):

Steady State ◽

Leading Edge ◽

Steady State Solution ◽

Tip Vortices ◽

Flutter Instability ◽

Compressor Rotor ◽

Stator Vane ◽

Blade Tip ◽

Variable Stator ◽

Large Rotor

The present study aimed at investigating numerically the effects of large blade tip running clearances on flutter stability of axial core multi-stage compressor rotor. During this study, the influences of aerodynamic boundary conditions, variable stator vane incidence and tip running clearances of upstream and downstream rotors on aerodynamic compressor flow and rotor flutter stability are thoroughly investigated. The simulations were carried out using an in-house 3-D aeroelasticity code. The steady-state-solution computations are performed on single-blade-passage-one-bladerow, stage-blocks and whole compressor models. These analyses included rotor blade models with nominal tip running clearances and artificially large tip clearances. Moreover, the effects of the variable stator vane incidences are assessed by performing steady-state-solution computations for nominal vane schedules and extreme vane malschedule. The first four flap and torsion vibration modes from finite element analyses are included in the unsteady flow computations and assessed for flutter stability. The results from the numerical investigations showed that the compressors with large rotor tip running clearances are susceptible to rotor tip flow induced flutter instability. The aerodynamic losses on the rotor with large tip clearances increase with other rotors having also large tip gaps. For the aerodynamic boundary conditions considered here, the simulations predicted flutter instability for the first flap vibration mode. The flutter instability predicted on the rotors with large tip clearances is driven by oscillating tip vortices on blade suction surface close to the blade tip leading edge. The flow in the rotor tip gap is mostly stalled and tip vortices oscillations are close to blade tip leading edge. The strength of these oscillating vortices appears to increase with increase in variable stator vane malschedule or negative incidence. Small changes in aerodynamic conditions can offset these instabilities. These studies indicate that the main ingredients for the occurrence of these phenomena are likely to be excessively large rotor tip running clearances combined with significant changes in flow incidence.

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Blade Tip-Vortices of a Four-Bladed Rotor with Axial Inflow

Journal of the American Helicopter Society ◽

10.4050/jahs.65.042002 ◽

2020 ◽

Vol 65 (4) ◽

pp. 1-13

Author(s):

Andreas Goerttler ◽

Johannes N. Braukmann ◽

C. Christian Wolf ◽

Anthony D. Gardner ◽

Markus Raffel

Keyword(s):

Particle Image ◽

Test Facility ◽

Vortex System ◽

Tip Vortices ◽

Image Velocimetry ◽

Swirl Velocity ◽

Blade Tip ◽

Velocity Circulation ◽

Bladed Rotor ◽

German Aerospace

The vortex system of four rotating and pitching DSA-9A blades was examined numerically and experimentally. Numerical computations were performed using German Aerospace Center (DLR)'s finite-volume solver TAU and were validated against experimental data gathered using particle image velocimetry carried out at the rotor test facility (RTG) in Göttingen. Algorithms deriving the vortex position, swirl velocity, circulation, and core radius were implemented. Hover-like conditions with a fixed blade pitch were analyzed giving further physical insights of the static vortex system. These results are used to understand the vortex development for the unsteady pitching conditions, which can be described as a superpositioning of static vortex states. The use of a zonal detached-eddy simulations approach improved physical modeling of the vortex development by resolving finer scales than URANS. Trimmed cases agree well with differences less than 0.5% in the circulation and swirl velocity.

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CFD Analysis of Contrarotating Open Rotor Aerodynamic Interactions

International Journal of Aerospace Engineering ◽

10.1155/2018/9538787 ◽

2018 ◽

Vol 2018 ◽

pp. 1-13 ◽

Cited By ~ 1

Author(s):

Wenbo Shi ◽

Jie Li ◽

Zhao Yang ◽

Heng Zhang

Keyword(s):

Flow Field ◽

Detailed Analysis ◽

High Efficiency ◽

Numerical Results ◽

Operating Conditions ◽

Power Coefficient ◽

Complex Flow ◽

Tip Vortices ◽

Open Rotor ◽

Blade Tip

High efficiency and low fuel consumption make the contrarotating open rotor (CROR) system a viable economic and environmentally friendly powerplant for future aircraft. While the potential benefits are well accepted, concerns still exist with respect to the vibrations and noise caused by the aerodynamic interactions of CROR systems. In this paper, emphasis is placed on the detailed analysis of the aerodynamic interactions between the front and aft propellers of a puller CROR configuration. For the first step, unsteady Reynolds-averaged Navier-Stokes (URANS) simulations coupled with dynamic patched grid technology are implemented on the isolated single-rotating propeller (SRP) configuration in various operating conditions in order to test the accuracy and feasibility of the numerical approach. The numerical results are verified by a wind tunnel test, showing good agreements with the experimental data. Subsequently, the URANS approach is applied to the CROR configuration. The numerical results obtained through the URANS approach help to improve the understanding of the complex flow field generated by the CROR configuration, and the comparison of SRP flow field and CROR flow field allows for a detailed analysis of the aerodynamic interactions of the front propeller blade wakes and tip vortices with the aft propeller. The main reason of the aerodynamic interactions is the mutual effects of the blade tip vortices, and the aft propeller reduces the strength of the blade tip vortices of the front propeller. Aerodynamic interactions will lead to the periodic oscillations of the aerodynamic forces, and the frequency of the oscillations is linked to the blade numbers. In addition, a CROR has a larger thrust and power coefficient than that of the SRP configuration in the same operating conditions. The URANS approach coupled with a dynamic patched grid method is tested to be an efficient and accurate tool in the analysis of propeller aerodynamic interactions.

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