Velocity distribution in a turbulent flow near a rough wall

Velocity distribution in the zone of developed wall turbulence, regardless of the conditions on the wall, is described by the well-known Prandtl logarithmic profile. In this distribution, the constant, that determines the value of the velocity, is determined by the nature of the interaction of the f...

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Bibliographic Details
Published in:Journal of physics. Conference series 2017-11, Vol.891 (1), p.12065
Main Authors: Korsun, A S, Pisarevsky, M I, Fedoseev, V N, Kreps, M V
Format: Article
Language:English
Subjects:
Boundary conditions
Channels
Energy dissipation
Fluid dynamics
Fluid flow
Parameters
Physics
Roughness
Turbulence models
Turbulent flow
Velocity
Velocity distribution
Viscosity
Viscous sublayers
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Summary:Velocity distribution in the zone of developed wall turbulence, regardless of the conditions on the wall, is described by the well-known Prandtl logarithmic profile. In this distribution, the constant, that determines the value of the velocity, is determined by the nature of the interaction of the flow with the wall and depends on the viscosity of the fluid, the dynamic velocity, and the parameters of the wall roughness.In extreme cases depending on the ratio between the thickness of the viscous sublayer and the size of the roughness the constant takes on a value that does not depend on viscosity, or leads to a ratio for a smooth wall.It is essential that this logarithmic profile is the result not only of the Prandtl theory, but can be derived from general considerations of the theory of dimensions, and also follows from the condition of local equilibrium of generation and dissipation of turbulent energy in the wall area. This allows us to consider the profile as a universal law of velocity distribution in the wall area of a turbulent flow.The profile approximation up to the maximum speed line with subsequent integration makes possible to obtain the resistance law for channels of simple shape. For channels of complex shape with rough walls, the universal profile can be used to formulate the boundary condition when applied to the calculation of turbulence models.This paper presents an empirical model for determining the constant of the universal logarithmic profile. The zone of roughness is described by a set of parameters and is considered as a porous structure with variable porosity.
ISSN:1742-6588
1742-6596
DOI:10.1088/1742-6596/891/1/012065