Turbulent Shear Flows 4 pp 124-140 | Cite as

# Statistical Characteristics of the Turbulent Wake Behind an Intersecting Cruciform Circular Cylinder

## Abstract

In order to clarify the periodic structure in the near field and the turbulent eddy structure in the far field of the intersecting cruciform circular cylinder wake, the detailed measurements have been performed on the statistical characteristics such as one-point and two-point time correlations, power spectra, triple velocity correlations and probability density profiles.

The experimental results are summarized as follows: The quasi-periodicity of the fluctuating velocity appears to different degrees at the different locations in the cross section of the near wake field, and is not found at the wake center. The turbulent large eddy structure conjectured from the contours of the space-time correlation is markedly different at each location in the cross section, and its decay rate is also slower at the center of the quasi-two-dimensional region than at the wake center. The magnitude of triple velocity correlation profiles on the bisector has the same order as that of the two-dimensional wake, but some of the shapes are significantly different.

### Keywords

Vortex Posit Cross Correlation### Nomenclature

*x*Distance in the streamwise direction from the origin of the cruciform circular cylinder, Fig. 1

*y*,*z*Distances along two cylinder axes from the origin respectively, Fig. 1

*y*′,*z*′Distances along the bisector of

*y*=*z*and normal to the bisector from the origin respectively, Fig. 1*r*_{x},*r*_{y},*r*_{z}Distances between the fixed probe position and the moved probe position in

*x*,*y*and*z*directions respectively*d*Diameter of circular cylinder, Fig. 1

*b*_{y′}Half width for the bisector, Fig. 1

*L*_{u}Integral length scale

*λ*Taylor’s micro scale

*l*_{ε}Kolmogorov’s dissipative scale

*t*Arbitrary time

*τ*Time delay

*U*Mean velocity in

*x*direction, Fig. 1*U*Free stream velocity, Fig. 1

*U*_{d}Mean velocity defect (

*U*_{ d }=*U*_{1}-*U*), Fig. 1*U*_{d}_{o}Mean velocity defect at the wake center

*u*,*υ*,*w*Fluctuating velocity components in

*x*,*y*and*z*directions respectively*υ*′,*w*′Fluctuating velocity components in

*y*′ and*z*′ directions respectively- \(\left( {1/2} \right)\overline {{q^2}}\)
Turbulent kinetic energy \(\left( {\overline {{q^2}} = \overline {{u^2}} + \overline {{\upsilon ^2}} + \overline {{w^2}} } \right)\)

*R*_{uu},*R*_{υυ},*R*_{ww}*R*_{υ′ υ′},*R*_{w′ w′}One-point auto-correlation coefficients of

*u*-,*υ*-,*w*-,*υ*′- and*w*′-fluctuating velocities respectively*R*_{u υ′},*R*_{u υ′}One-point cross correlation coefficients between

*u*- and*υ*-fluctuating velocities and between*u*- and*υ*′-fluctuating velocities respectively*E*Power spectra of fluctuating velocity components

*S*Skewness factors of fluctuating velocity components

*F*Flatness factors of fluctuating velocity components

*v*Kinematic viscosity of air

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