Identification and mitigation of T-S waves using localized dynamic surface modification

Amitay, Michael; Tuna, Burak A.; Dell'Orso, Haley

doi:10.1063/1.4953844

“…These scenarios allow for substantial savings in fuel expenditure for air, sea, land vehicles, wind and water turbines, long-range gas and liquid pipelines, and other similar applications. Flow control by active means has been extensively investigated over the past few decades [2,3,4,5,6,7]. Passive techniques, on the other hand, are desirable because of their simplicity and low cost, i.e., no active control devices, wires, ducts, slots, etc., are needed and no electric power is required to drive the control process.…”

Section: Introductionmentioning

confidence: 99%

Phononic-subsurface flow stabilization by subwavelength locally resonant metamaterials

Kianfar¹,

Hussein²

2023

Preprint

0

View full text Add to dashboard Cite

The interactions between a solid surface and a fluid flow underlie dynamical processes relevant to air, sea, and land vehicle performance and numerous other technologies. Key among these processes are unstable flow disturbances that contribute to fundamental transformations in the flow field. Precise control of these disturbances is possible by introducing a phononic subsurface (PSub). This comprises locally attaching a finite phononic structure perpendicular to an elastic surface exposed to the flowing fluid. This structure experiences ongoing excitation by an unstable flow mode, or more than one mode, traveling in conjunction with the mean flow. The excitation generates small deformations at the surface that trigger elastic wave propagation within the structure, traveling away from the flow and reflecting at the end of the structure to return to the fluid-structure interface and back into the flow. By targeted tuning of the unit-cell and finite-structure characteristics of the PSub, the returning waves may be devised to resonate and reenter the flow out of phase, leading to significant destructive interference of the continuously incoming flow waves near the surface and subsequently to their attenuation over the spatial extent of the control region. This entire mechanism is passive, responsive, and engineered offline without needing coupled fluid-structure simulations; only the flow instability's frequency, wavelength, and overall modal characteristics must be known. Disturbance stabilization in a wall-bounded transitional flow leads to delay in laminar-to-turbulent transition and reduction in skin-friction drag. Destabilization is also possible by alternatively designing the PSub to induce constructive interference, which is beneficial for delaying flow separation and enhancing chemical mixing and combustion. In this paper, we present a PSub in the form of a locally resonant elastic metamaterial, designed to operate in the elastic subwavelength regime and hence being significantly shorter in length compared to a phononic-crystal-based PSub. This is enabled by utilizing a sub-hybridization resonance. Using direct numerical simulations (DNS) of channel flows, both types of PSubs are investigated, and their controlled spatial and energetic influence on the wall-bounded flow behavior is demonstrated and analyzed. We show

show abstract

“…These scenarios allow for substantial savings in fuel expenditure for air, sea, land vehicles, wind and water turbines, long-range gas and liquid pipelines, and other similar applications. Flow control by active means has been extensively investigated over the past few decades [2][3][4][5][6][7]. Passive techniques, on the other hand, are desirable because of their simplicity and low cost, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…These two scenarios are manifestations of a contiguous solid-fluid flow antiresonance or resonance phenomenon, respectively. Furthermore, a PSub takes the form of a finite, relatively stiff elastic structure oriented in a manner that enables only small elastic motion perpendicular 6 to the fluid-structure interface to be admitted and transferred into the flow. Ensuring small vibrations at the surface allows the PSub to modulate mostly (to the extent allowed in practice) a single-velocity component of the instability field (the wall-normal component), as opposed to simultaneously influencing multiple components at once.…”

Section: Introductionmentioning

confidence: 99%

Phononic-subsurface flow stabilization by subwavelength locally resonant metamaterials

Kianfar

¹

,

Hussein

²

2023

New J. Phys.

5

0

View full text Add to dashboard Cite

The interactions between a solid surface and a fluid flow underlie dynamical processes relevant to air, sea, and land vehicle performance and numerous other technologies. Key among these processes are unstable flow disturbances that contribute to fundamental transformations in the flow field. Precise control of these disturbances is possible by introducing a phononic subsurface (PSub). This comprises locally attaching a finite phononic structure perpendicular to an elastic surface exposed to the flowing fluid. This structure experiences ongoing excitation by an unstable flow mode, or more than one mode, traveling in conjunction with the mean flow. The excitation generates small deformations at the surface that trigger elastic wave propagation within the structure, traveling away from the flow and reflecting at the end of the structure to return to the fluid-structure interface and back into the flow. By targeted tuning of the unit-cell and finite-structure characteristics of the PSub, the returning waves may be devised to resonate and reenter the flow out of phase, leading to significant destructive interference of the continuously incoming flow waves near the surface and subsequently to their attenuation over the spatial extent of the control region. This entire mechanism is passive, responsive, and engineered offline without needing coupled fluid-structure simulations; only the flow instability's frequency, wavelength, and overall modal characteristics must be known. Disturbance stabilization in a wall-bounded transitional flow leads to delay in laminar-to-turbulent transition and reduction in skin-friction drag. Destabilization is also possible by alternatively designing the PSub to induce constructive interference, which is beneficial for delaying flow separation and enhancing chemical mixing and combustion. In this paper, we present a PSub in the form of a locally resonant elastic metamaterial, designed to operate in the elastic subwavelength regime and hence being significantly shorter in length compared to a phononic-crystal-based PSub. This is enabled by utilizing a sub-hybridization resonance. Using direct numerical simulations (DNS) of channel flows, both types of PSubs are investigated, and their controlled spatial and energetic influence on the wall-bounded flow behavior is demonstrated and analyzed. We show that the PSub's effect is spatially localized as intended, with a rapidly diminishing streamwise influence away from its location in the subsurface.

show abstract

“…Surface temperature 14,15,46,47 , plasma actuators [48][49][50] and surface compliance 51,52 are just some of the methods that have been utilised as a means of controlling transition in boundary layers. Dynamic wall modification was utilised experimentally by Amitay et al 53 to excite and control TS disturbances on a flat plate. Wall modulation was implemented using piezoelectrically driven oscillating surface actuators, while the wave superposition principle was employed to attenuate disturbances.…”

Section: Introductionmentioning

confidence: 99%

Optimizing control of stationary cross-flow vortices excited by surface roughness

Thomas

¹

,

Mughal

²

2022

Physics of Fluids

2

0

View full text Add to dashboard Cite

Stationary cross-flow vortices are excited within the swept Hiemenz boundary layer via surface roughness and actively controlled using an optimally configured control device. Control is modelled using localised wall motion, but in practice the optimisation strategy could be applied to other laminar flow control technologies. A sensor-control iterative procedure, based on solutions of the forward and adjoint linearised Navier--Stokes equations, is applied to both feedforward and feedback loop systems. The former strategy only allows the control settings to be configured once, while the latter approach permits the repeated reoptimisation of the control device. Surface roughness establishes a stationary cross-flow disturbance with a pre-defined set of flow conditions, but an unknown amplitude and phase. A sensor measures the local amplitude of the perturbation and relays the information to the control mechanism. Solutions of the adjoint linearised Navier--Stokes equations are coupled with the sensor measurements to configure and optimise the control mechanism, and establish an anti-phase wave that brings about destructive wave interference. The amplitude of the stationary cross-flow instability is reduced by an order $10^3$ for the feedforward system, while amplitude reductions of the order $10^3$ per iteration and $10^8$ overall are realisable for the feedback modelling approach. Similar levels of flow control are realisable for a multiple controller configuration. However, stationary cross-flow disturbances could not be eliminated indefinitely. Inevitably, the cross-flow instability started to grow again, albeit at a considerably lower magnitude. The analysis is extended to include the effects of systematic error in the sensors measuring capability.

show abstract

Identification and mitigation of T-S waves using localized dynamic surface modification

Cited by 26 publications

References 21 publications

Phononic-subsurface flow stabilization by subwavelength locally resonant metamaterials

Phononic-subsurface flow stabilization by subwavelength locally resonant metamaterials

Phononic-subsurface flow stabilization by subwavelength locally resonant metamaterials

Optimizing control of stationary cross-flow vortices excited by surface roughness

Contact Info

Product

Resources

About