Broadband scattering from shear flows and the non-doppler remote sensing of velocity profiles

A large body of data now exists on the response of turbulent shear flows to sudden or step changes in surface roughness. Authors have used a variety of methods to reduce and present the data; thus a consistent description of these flows has not yet been presented. This paper presents all available data reduced in a uniform way. As there are extremely few Reynolds stress measurements within this large body of data, the analyses presented here are necessarily based on mean velocity profiles. It is shown that the growth rate of the new internal layer for all types of flow both with and without pressure gradient can be described in terms of a single length scale associated with the new wall condition. It is also shown that all mean velocity profiles after a step change in roughness display semi-logarithmic distributions. However, in the region immediately downstream of a step the constant of proportionality (the von Karman constant) has values different from the usual equilibrium value of 0.41. The differences appear to be large with values for the constant ranging between about 0.2 to 0.8.

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Stability of Quasi-two-dimensional Shear Flows with Arbitrary Velocity Profiles

Fundamentals of Geophysical Hydrodynamics - Encyclopaedia of Mathematical Sciences ◽

10.1007/978-3-642-31034-8_22 ◽

2013 ◽

pp. 195-204

Author(s):

Felix V. Dolzhansky

Keyword(s):

Shear Flows ◽

Velocity Profiles ◽

Two Dimensional ◽

Arbitrary Velocity

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Effects of Nonuniform Inlet Velocity Profiles on Flow Regimes and Performance in Two-Dimensional Diffusers

Journal of Basic Engineering ◽

10.1115/1.3571155 ◽

1969 ◽

Vol 91 (3) ◽

pp. 462-474 ◽

Cited By ~ 22

Author(s):

S. Wolf ◽

J. P. Johnston

Keyword(s):

Shear Flows ◽

Prediction Method ◽

Flow Regimes ◽

Velocity Profiles ◽

Two Dimensional ◽

Rotational Model ◽

Inlet Velocity ◽

The Core ◽

Uniform Shear ◽

And Performance

An analytical and experimental study on the effects of large distortions of inlet velocity profiles on flow regimes and performance in diffusers is reported. Experiments are restricted to flow in straight, two-dimensional diffusers with turbulent boundary layers. Systematic data are obtained for two general types of inlet flows: (1) simple, uniform shear flows in the core, and (2) severely nonuniform shear flows of the wake, jet, and step-shear type. For uniform shear flows a first order prediction method based on inviscid rotational flow and the boundary layer blockage concept is developed and verified for diffusers operating in the unstalled flow regime. For nonuniform shear flows the inviscid rotational model is shown to predict performance trends better than the irrotational model; however, the inviscid rotational model is inadequate as a precise prediction method because no account is taken of mixing in the core region. Geometry and performance correlations for peak pressure recovery (at constant N/W1) are also established.

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