A mechanism for mitigation of blade–vortex interaction using leading edge blowing flow control

Weiland, Chris; Vlachos, Pavlos P.

doi:10.1007/s00348-009-0672-z

Cited by 6 publications

(5 citation statements)

References 31 publications

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“…Aluminium rods were embedded in the model to increase its strength and stiffness. The experiments were conducted in a closed-loop water tunnel at and flow uniformity at the test location better than 99% (Weiland and Vlachos, 2009). …”

Section: Experimental Model and Test Facilitymentioning

confidence: 99%

Aerodynamics of the flying snake Chrysopelea paradisi: how a bluff body cross-sectional shape contributes to gliding performance

Holden

Socha

Cardwell

et al. 2014

Journal of Experimental Biology

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A prominent feature of gliding flight in snakes of the genus Chrysopelea is the unique cross-sectional shape of the body, which acts as the lifting surface in the absence of wings. When gliding, the flying snake Chrysopelea paradisi morphs its circular cross-section into a triangular shape by splaying its ribs and flattening its body in the dorsoventral axis, forming a geometry with fore-aft symmetry and a thick profile. Here, we aimed to understand the aerodynamic properties of the snake's cross-sectional shape to determine its contribution to gliding at low Reynolds numbers. We used a straight physical model in a water tunnel to isolate the effects of 2D shape, analogously to studying the profile of an airfoil of a more typical flyer. Force measurements and time-resolved (TR) digital particle image velocimetry (DPIV) were used to determine lift and drag coefficients, wake dynamics and vortexshedding characteristics of the shape across a behaviorally relevant range of Reynolds numbers and angles of attack. The snake's crosssectional shape produced a maximum lift coefficient of 1.9 and maximum lift-to-drag ratio of 2.7, maintained increases in lift up to 35 deg, and exhibited two distinctly different vortex-shedding modes. Within the measured Reynolds number regime (Re=3000-15,000), this geometry generated significantly larger maximum lift coefficients than many other shapes including bluff bodies, thick airfoils, symmetric airfoils and circular arc airfoils. In addition, the snake's shape exhibited a gentle stall region that maintained relatively high lift production even up to the highest angle of attack tested (60 deg). Overall, the crosssectional geometry of the flying snake demonstrated robust aerodynamic behavior by maintaining significant lift production and near-maximum lift-to-drag ratios over a wide range of parameters. These aerodynamic characteristics help to explain how the snake can glide at steep angles and over a wide range of angles of attack, but more complex models that account for 3D effects and the dynamic movements of aerial undulation are required to fully understand the gliding performance of flying snakes.

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Section: Experimental Model and Test Facilitymentioning

confidence: 99%

Aerodynamics of the flying snake Chrysopelea paradisi: how a bluff body cross-sectional shape contributes to gliding performance

Holden

Socha

Cardwell

et al. 2014

Journal of Experimental Biology

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“…Body-vortex interaction (BVI) is classified according to the vortex orientation relative to the impacted body (A thorough review of the classifications is provided by Filippone & Afgan (2008)). The most relevant class of interaction is "parallel", meaning the cylinder's axis and the vortex's axis of rotation are parallel (Weiland & Vlachos, 2009).…”

Section: Introductionmentioning

confidence: 99%

The variation in the maximum loading of a circular cylinder impacted by a 2D vortex with time of impact

Strasser

Selvam

2015

Journal of Fluids and Structures

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Direct numerical simulation is used to study the loading of a rigid, circular cylinder impacted by a 2D vortex. The vortex travels within a stream of fluid characterized by Reynolds number of 150. Vortex impact occurs at twenty-five different times within one vortex shedding cycle. Substantial variation is observed in the maximum values of the drag and lift force coefficients. This variation is due to interaction between the impinging vortex and those attached to the cylinder. As the radius of the impinging vortex is increased from one to three times the cylinder's diameter, the variation in maximum force coefficients with time of impact decreases. The variation decreases because the larger vortex alters the flow field and vortex shedding cycleprior to impacting the cylinder. For structures impacted by a vortex similar in size, significant under-prediction of the maximum loading may occur if variation in loading with vortex impact time is not considered. * where δt * is the solution time step. Selvam (1997a) provides further information concerning the implementation of the balance tensor diffusion scheme.

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“…The other flow conditions of the unsteady blowing case are kept completely consistent with the nonblowing case and the steady blowing case, and simulations are carried out under the same solver settings and grid conditions. We have carried out detailed parametric studies on steady surface blowing in previous work [15], which discussed the effects of changes in parameters such as jet slot location, jet velocity, and jet slot area of steady blowing on the reduction of BVI noise. The BVI noise reduction results in this steady blowing research show that blowing near the trailing edge of the blade upper surface can effectively alter the tip vortex trajectory, increase the blade-vortex miss distance, and weaken the vortex strength, which is beneficial for reducing BVI noise.…”

Section: Unsteady Blowing Modelmentioning

confidence: 99%

“…The jet velocity is kept at 20% of the rotor tip speed, i.e., 45.2 m/s, the blowing direction is normal to the blade surface, and the air mass flow rate of the jet is 9:9 × 10 −3 kg/s. The detailed results of the nonblowing baseline case and the V jet = 0:2V tip steady blowing case were described in our previous work [15]. In the study of unsteady blowing, the defined slot location is the same as the jet slot location modeled in the steady blowing case.…”

Section: Unsteady Blowing Modelmentioning

confidence: 99%

“…As an active vortex control method, rotor tip air mass injection (TAMI) technology [13] works by arranging jet ducts at the rotor tip or on the blade surface to blow out compressed air, which can increase the diffusion, reduce the strength, or alter the trajectory of the tip vortex, thereby reducing BVI noise. This active control concept based on positive mass jet blowing on the blade surface has successfully demonstrated an excellent ability to control the tip vortex structure and trajectory in many experiments and numerical studies [14][15][16]. However, previous research results on blade surface blowing have illustrated that blowing will have an adverse effect on rotor aerodynamics and may cause a significant loss in the rotor thrust [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

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Numerical Investigation of an Unsteady Blade Surface Blowing Method to Reduce Rotor Blade-Vortex Interaction Noise

Sun

Shi

2022

International Journal of Aerospace Engineering

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This paper presents a numerical investigation of unsteady surface blowing using periodic variations of jet velocity with azimuthal angle to reduce helicopter rotor blade-vortex interaction (BVI) noise. The unsteady blowing is modeled as the mass flow outlet boundary condition of time-varying jet velocity on the blade surface grid using computational fluid dynamics. The same high-resolution overset grid system and flow/noise solver are used to perform a detailed flow field simulation and noise prediction for the nonblowing baseline case and the steady/unsteady blowing cases under the rotor BVI condition, and a grid convergence study for the steady and unsteady blowing cases is carried out. The BVI noise reduction and rotor thrust coefficient results of the unsteady blowing method and the previously published steady blowing with constant jet velocity are then compared. The noise reduction level of unsteady blowing is approximately equivalent to that of steady blowing (noise reduction is more than 3 dB). However, the loss in rotor thrust coefficient caused by unsteady blowing (3.3%) is only half of that by steady blowing (6.3%); the air mass cost by unsteady blowing is only 63.7% of that by steady blowing per rotation revolution. The results show that unsteady blowing can effectively reduce BVI noise with lower cost and less thrust loss.

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A mechanism for mitigation of blade–vortex interaction using leading edge blowing flow control

Cited by 6 publications

References 31 publications

Aerodynamics of the flying snake Chrysopelea paradisi: how a bluff body cross-sectional shape contributes to gliding performance

Aerodynamics of the flying snake Chrysopelea paradisi: how a bluff body cross-sectional shape contributes to gliding performance

The variation in the maximum loading of a circular cylinder impacted by a 2D vortex with time of impact

Numerical Investigation of an Unsteady Blade Surface Blowing Method to Reduce Rotor Blade-Vortex Interaction Noise

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