Imperial College London
Professor John Christos Vassilicos

ProfessorJohn ChristosVassilicos

Faculty of Engineering, Department of Aeronautics

Visiting Professor
 
 
 
//

Contact

 

+44 (0)20 7594 5137j.c.vassilicos

 
 
//

Assistant

 

Miss Jackie O'Neill +44 (0)20 7594 5079

 
//

Location

 

CAGB 314City and Guilds BuildingSouth Kensington Campus

//

Summary

 

Publications

Citation

BibTex format

@article{Zheng:2018:10.1017/jfm.2018.387,
author = {Zheng, S and Bruce, PJK and Graham, JMR and Vassilicos, JC},
doi = {10.1017/jfm.2018.387},
journal = {Journal of Fluid Mechanics},
pages = {788--820},
title = {Weakly sheared turbulent flows generated by multiscale inhomogeneous grids},
url = {http://dx.doi.org/10.1017/jfm.2018.387},
volume = {848},
year = {2018}
}
Download

RIS format (EndNote, RefMan)

TY  - JOUR
AB  - A group of three multiscale inhomogeneous grids have been tested to generate different types of turbulent shear flows with different mean shear rate and turbulence intensity profiles. Cross hot-wire measurements were taken in a wind tunnel with Reynolds number ReD of 6000–20 000, based on the width of the vertical bars of the grid and the incoming flow velocity. The effect of local drag coefficient CD on the mean velocity profile is discussed first, and then by modifying the vertical barsto obtain a uniform aspect ratio the mean velocity profile is shown to be predictable using the local blockage ratio profile. It is also shown that, at a streamwise location x = xm, the turbulence intensity profile along the vertical direction u0(y) scales with the wake interaction length x peak∗,n = 0.21g2n/(αCDwn) (α is a constant characterizing the incoming flow condition, and gn, wn are the gap and width of the vertical bars,respectively, at layer n) such that (u0/Un) 2β2 (CDwn/x peak ∗,n) −1 ∼ (xm/x peak ∗,n) b, where β is a constant determined by the free-stream turbulence level, Un is the local mean velocity and b is a dimensionless power law constant. A general framework of grid design method based on these scalings is proposed and discussed. From the evolutionof the shear stress coefficient ρ(x), integral length scale L(x) and the dissipation coefficient C  (x), a simple turbulent kinetic energy model is proposed that describes the evolution of our grid generated turbulence field using one centreline measurement and one vertical profile of u 0(y) at the beginning of the evolution. The results calculated from our model agree well with our measurements in the streamwiseextent up to x/H ≈ 2.5, where H is the height of the grid, suggesting that it might be possible to design some shear flows with desired mean velocity and turbulence intensity profiles by designing the geometry of a passive grid.
AU  - Zheng,S
AU  - Bruce,PJK
AU  - Graham,JMR
AU  - Vassilicos,JC
DO  - 10.1017/jfm.2018.387
EP  - 820
PY  - 2018///
SN  - 0022-1120
SP  - 788
TI  - Weakly sheared turbulent flows generated by multiscale inhomogeneous grids
T2  - Journal of Fluid Mechanics
UR  - http://dx.doi.org/10.1017/jfm.2018.387
UR  - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000442100900003&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
UR  - http://hdl.handle.net/10044/1/77639
VL  - 848
ER  -
Download