Drag-Reduction Mechanisms of Suction-and-Oscillatory-Blowing Flow Control

Schatzman, David; Wilson, Jacob; Arad, Eran; Seifert, Avi; Shtendel, Tom

doi:10.2514/1.j052903

Cited by 28 publications

(13 citation statements)

References 18 publications

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“…In [265], the application of pulsating jets reduced the root mean-square (RMS) of the fluctuating load of wind turbine blades by up to 12%. Moreover, load alleviation induced by a suction or pulsed-blowing coupled mechanism [266] is attributable to boundarylayer extraction (suction) and energizing (blowing), unsteady shear-layer excitation, thrust generation and streamwise vortices. Adaptive blowing (regulated steady blowing) was also credited with load-excursion elimination, by controlling boundary-layer separation using jet-momentum flux [267], with a successful demonstration of the eradication of dynamic-stall vortex using jet momentum under deep stall conditions.…”

Section: Blowing-suction Controlmentioning

confidence: 99%

Review of Flow-Control Devices for Wind-Turbine Performance Enhancement

Akhter

Omar

2021

Energies

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It is projected that, in the following years, the wind‐energy industry will maintain its rapid growth over the last few decades. Such growth in the industry has been accompanied by the desirability and demand for larger wind turbines aimed at harnessing more power. However, the fact that massive turbine blades inherently experience increased fatigue and ultimate loads is no secret, which compromise their structural lifecycle. Accordingly, this demands higher overhaul‐and‐maintenance (O&M) costs, leading to higher cost of energy (COE). Introduction of flow‐control devices on the wind turbine is a plausible solution to this issue. Flow‐control mechanisms feature the ability to effectively enhance/suppress turbulence, advance/delay flow transition, and prevent/promote separation, leading to enhancement in aerodynamic and aeroacoustics performance, load alleviation and fluctuation suppression, and eventually wind turbine power augmentation. These flow‐control devices are operated primarily under two schemes: passive and active control. Development and optimization of flow‐control devices present the potential for reduction in the COE, which is a major challenge against traditional power sources. This review performs a comprehensive and up‐to‐date literature survey of selected flow‐control devices, from their time of development up to the present. It contains a discussion on the current prospects and challenges faced by these devices, along with a comparative analysis centered on their aerodynamic controllability. General considerations and conclusive remarks are presented after the discussion.

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Section: Blowing-suction Controlmentioning

confidence: 99%

Review of Flow-Control Devices for Wind-Turbine Performance Enhancement

Akhter

Omar

2021

Energies

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“…Figure 4 shows the geometry of the suction holes, actuator nozzle, and oscillatory blowing slots. This geometry is similar to the configuration used in previous experiments and simulations on an axisymmetric bluff body 6,7 .…”

Section: Turbulent Boundary Layer Setupmentioning

confidence: 91%

Suction and Oscillatory Blowing Interaction with Boundary Layers

Schatzman

Wilson

Marom

et al. 2015

53rd AIAA Aerospace Sciences Meeting

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This work presents ongoing experiments toward developing fundamental understanding of suction and oscillatory blowing (SaOB) flow control mechanisms along with development of accurate and practical CFD simulation methodologies for complex unsteady active flow control systems. Experimental and computational studies were conducted on SaOB actuators' internal flow and external interaction with two zero pressure gradient boundary layers. The experimental work incorporates detailed multi component hot-wire measurements of both laminar and turbulent boundary layers with steady suction and pulsed blowing for a single actuator and an array configuration. Large eddy simulation was employed for the computational model. Simulations were carried out on the actuator internal flow, and the resulting oscillatory blowing jet exit velocity profiles are characterized and fit with a functional form, in order to create simplified boundary conditions for future flow control simulations. Both experimental and computational results show that the suction hole geometry and configuration is an important factor in determining the structure and stability of the downstream laminar as well as turbulent boundary layer flow-fields. Measurements of oscillatory blowing jets interacting with a turbulent boundary layer demonstrate this flow control produces unsteady spanwise and streamwise vorticity components that can be interpreted as counter-rotating streamwise vortex patterns. NomenclatureA = area of suction holes A i = phase-locked coefficients C i = coefficients for functional fit jet velocity C f = skin friction coefficient d = suction hole diameter f = actuator oscillation frequency H = boundary layer shape factor 2 L FB = length of feedback tube L n = nozzle width P in = air supply pressure at actuator inlet P suc = static pressure in suction chamber Q = volume flow rate of suction Re x = Reynolds number based on streamwise distance Re L = Reynolds number based on nozzle width S ij = strain rate tensor s = suction hole spanwise spacing U e = local external velocity U j = jet velocity U r = reference supply jet velocity at converging nozzle U s = suction velocity U ∞ = freestream velocity u',v',w' = turbulent velocity fluctuations w , ṽ , ũ = coherent velocity fluctuations x, y, z = coordinates distance in turbulent boundary layer X, Y, Z = coordinates distance in laminar boundary layer  = linear phase-lock function δ = boundary layer thickness δ * = boundary layer displacement thickness  = non-dimensional spanwise nozzle coordinate θ = boundary layer momentum thickness λ 2 = second negative eigenvalue of the matrix S ij S ij + Ω ij Ω ij  = suction loss factor ρ = air density ν = kinematic viscosity  = phase angle ω x = streamwise vorticity component ω z = spanwise vorticity component Ω ij = vorticity tensor = denotes phase-averaging

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“…Pastoor et al (2008) achieved a drag reduction of 15 % on a two-dimensional bluff body when applying open-and closed-loop control with zero-net-mass-flux actuators located at the base edges. Schatzman et al (2014) investigated in detail the related effects of steady suction-and-oscillatory-blowing actuators on the flow of an axisymmetric bluff body achieving a drag reduction of about 15 % when accounting for the power consumption. Barros et al (2014) examined the effect of pulsed jets located around the base perimeter of an Ahmed model without a slanted rear end.…”

Section: Introductionmentioning

confidence: 99%