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Deformation of viscoelastic coating in a turbulent flow

Deformation of viscoelastic coating in a turbulent flow Abstract The rate and amplitude of compliant coating deformation by turbulent pressure pulsations were calculated. Complex compliance determined by a 2D model has two components: along and across the coating. Dependence of the components of dimensionless compliance on the wavelength — coating thickness ratio was determined for 0.3 < λ/H < 30 and dependence of these components on the ratio of flow velocity to velocity of wave propagation was determined for 0.1 < V/C < 10. Deformation amplitude and rate of surface displacement for the hard compliant coatings which can be used in practice were calculated within the range of 5–55 m/s for the water and air turbulent flow. The effects of the loss tangent and Poisson’s ratio of the coating material were also studied. It is shown that the mean-square displacement of their surface does not exceed the thickness of a viscous sublayer. However, the velocity of surface motion is comparable with velocity pulsations in a boundary layer near a wall. This can be a reason for drag reduction on a compliant wall. The calculated value of ratio between energy absorbed by the wall and energy dissipated within the flow because of drag was 10−4 for water and 10−6 for air. This estimate does not confirm the hypothesis explaining drag reduction by energy takeoff from the flow. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Thermophysics and Aeromechanics Springer Journals

Deformation of viscoelastic coating in a turbulent flow

Thermophysics and Aeromechanics , Volume 16 (1): 13 – Mar 1, 2009

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Publisher
Springer Journals
Copyright
2009 Pleiades Publishing, Ltd.
ISSN
0869-8643
eISSN
1531-8699
DOI
10.1007/s11510-009-0004-z
Publisher site
See Article on Publisher Site

Abstract

Abstract The rate and amplitude of compliant coating deformation by turbulent pressure pulsations were calculated. Complex compliance determined by a 2D model has two components: along and across the coating. Dependence of the components of dimensionless compliance on the wavelength — coating thickness ratio was determined for 0.3 < λ/H < 30 and dependence of these components on the ratio of flow velocity to velocity of wave propagation was determined for 0.1 < V/C < 10. Deformation amplitude and rate of surface displacement for the hard compliant coatings which can be used in practice were calculated within the range of 5–55 m/s for the water and air turbulent flow. The effects of the loss tangent and Poisson’s ratio of the coating material were also studied. It is shown that the mean-square displacement of their surface does not exceed the thickness of a viscous sublayer. However, the velocity of surface motion is comparable with velocity pulsations in a boundary layer near a wall. This can be a reason for drag reduction on a compliant wall. The calculated value of ratio between energy absorbed by the wall and energy dissipated within the flow because of drag was 10−4 for water and 10−6 for air. This estimate does not confirm the hypothesis explaining drag reduction by energy takeoff from the flow.

Journal

Thermophysics and AeromechanicsSpringer Journals

Published: Mar 1, 2009

References