Effects of flow width in nominally two-dimensional turbulent separated flows
Abstract
Pulsed-wire measurements of mean and fluctuating wall shear stress have been measured beneath a nominally two-dimensional separated and reattaching flow, where the flow width has been varied by means of end plates. End effects are much larger near the surface than they are in the outer flow. Residual effects of the presence of the end walls on the mean wall shear stress are seen for a flow width as large as seven bubble lengths. It is inferred that the effects of the end-wall boundary layers extend to a substantially smaller distance. The influence of the end plates on the rms of the fluctuations is markedly less than that on the mean stress.
Keywords
Wall Shear Stress Separation Bubble Splitter Plate Reattachment Length Bubble LengthList of symbols
- Cf
Coefficient of mean (x-direction) wall shear stress
- Cf’
Coefficient of rms of fluctuating (x-direction) wall shear stress
- Cf(min)
Minimum of C f
- W
Lateral width of flow (between end plates or side walls)
- x
Streamwise distance from point of separation
- z
Lateral distance from centre-line
- X
x-distance to attachment
- Xref
Reference X
- X7
X at high aspect ratio
- U
Mean streamwise velocity
- u
Fluctuating streamwise velocity
- hf
Height of fence tip above splitter plate surface
- D
Half height of working section
- τw
Wall shear stress
Notes
Acknowledgements
The experimental work reported here was undertaken by F Ciampoli while at the University of Surrey, supported by the EU Socrates exchange programme, as part of studies in Aerospace Engineering at the University of Rome ‘La Sapienza’. We wish to thank Prof. G. P. Romano for his support.
References
- Castro IP, Fackrell JB (1978) A note on two-dimensional fence flows, with emphasis on wall constraint. J Ind Aerodynamics 3:1–20CrossRefGoogle Scholar
- Castro IP, Haque A (1987) (fig 2) The structure of a turbulent shear layer bounding a separation region. J Fluid Mech 179:439–468CrossRefGoogle Scholar
- Castro IP, Dianat M, Bradbury LJS (1987) The pulsed-wire skin friction measurement technique. Turbulent shear flows, vol 5. Springer, New York, Berlin, Heidelberg, pp 278–290Google Scholar
- Hancock PE (1999) Measurements of mean and fluctuating wall shear stress beneath spanwise-invariant separation bubbles. Expts Fluids 27:53–59CrossRefGoogle Scholar
- Hancock PE (2000) Low Reynolds number two-dimensional separated and reattaching turbulent shear flow. J Fluid Mech 410:101–122MATHCrossRefGoogle Scholar
- Hancock PE, Castro IP (1993) End effects in nominally two-dimensional separated flows. Appl Sci Res 51:173–178CrossRefGoogle Scholar
- Hardman JR, Hancock PE (2000) The near-wall layer beneath a moderately converging three-dimensional turbulent separated and reattaching flow. Eur J Mech B-Fluids 19(5):653–672MATHCrossRefGoogle Scholar
- Jaroch MP, Fernholz HH (1989) (fig 2) The three-dimensional character of a nominally two-dimensional separated turbulent shear flow. J Fluid Mech 205:523–552CrossRefGoogle Scholar
- McCluskey FM, Hancock PE, Castro IP (1991) Three-dimensional separated flows. In: 8th Turbulent Shear Flows Symposium, Munich, pp 9.5.1–9.5.6 September 1991Google Scholar
- Patel VC (1965) Calibration of the Preston tube and limitations on its use in pressure gradients. J Fluid Mech23:185–208CrossRefGoogle Scholar
- Ruderich R, Fernholz HH (1986) An experimental investigation of turbulent shear flow with separation, reverse flow and reattachment. J Fluid Mech 163: 283–322CrossRefMathSciNetGoogle Scholar
- Smits AJ (1982) Scaling parameters for a time-averaged separation bubble. Trans ASME: J Fluids Eng 104:178–184CrossRefGoogle Scholar