Patent ID: 6516652
Filing Date: 2003-02-11
Classification: B63B,B64C,F15D,Y02T

Abstract:
A method for estimating the reduction in friction drag of a body with a viscoelastic coating as compared to the friction drag of a rigid surface of identical size and shape as said body, during turbulent flow at a specified freestream velocity, said method comprising the following steps, performed in the order indicated:(I) using boundary conditions for a rigid surface, determining characteristics of a turbulent boundary layer at the specified freestream velocity, said characteristics including the boundary layer thickness, phase speed and frequency corresponding to maximum-energy-carrying disturbances, mean velocity profiles, Reynolds stress distributions, wall shear stress distribution, and friction drag, (II) selecting a density, complex shear modulus, and thickness of a viscoelastic coating which corresponds to minimum oscillation amplitudes and maximum flux of energy into the viscoelastic coating during excitation by a forcing function substantially identical to the excitation produced by the turbulent boundary layer as determined in step I, and (III) using oscillation amplitudes and energy flux corresponding to the viscoelastic coating of selected density, complex shear modulus and thickness as determined in step II, determining characteristics of the turbulent boundary layer at the specified freestream velocity, including mean velocity profiles, Reynolds stress distributions, wall shear stress distribution, and friction drag, and (IV) determining a percentage reduction in friction drag as the ratio of i) the friction drag as determined in step I minus the friction drag as determined in step III, divided by ii) the friction drag as determined in step I.