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Experiments in Fluids

, Volume 34, Issue 2, pp 220–226 | Cite as

Plane mixing layers from parallel and non-parallel merging of two streams

  • M. Abdul AzimEmail author
  • A. K. M. Sadrul Islam
Article

Abstract

Two types of mixing layers produced from two streams merging at 0° and 18° have been investigated. Each type of mixing layer was produced with velocity ratios 0.7, 0.8 and 0.9 and measurements were taken at six streamwise locations. The boundary layers were untripped and initially turbulent in all cases. Both types of mixing layers were found to attain a self-similar state for velocity ratios 0.7 and 0.8 but failed for 0.9 within the measurement domain. It appears that the mixing layer flow becomes self-similar earlier when merging at 18° than at 0°. With increasing velocity ratio, the development distance was increased and the splitter wake played a dominant role in the development of the mixing layers. The mixing layers from non-parallel merging streams (18°) were found to have higher growth in the near-field than those from parallel merging streams (0°). Both types of mixing layers were found to decrease in growth with increasing velocity ratio, though they spread more at the high-speed side.

Keywords

Reynolds Stress Velocity Ratio Free Shear Layer Streamwise Pressure Gradient Streamwise Velocity Profile 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

α

angle of merging

δ

mixing layer thickness (=y 0.1y 0.9)

η

similarity variable [=(yy 0.5)/δ]

λ

modified velocity ratio [=(1−r)/(1+r)]

r

velocity ratio (=u 2/u 1)

Reθ

Reynolds number based on θ (=u o θ/ν)

θ

momentum thickness of the mixing layer

u,v

mean velocities in x and y directions, respectively

u′(t)

fluctuating component of the streamwise velocity

u

non-dimensional velocity [=(uu 2)/(u 1u 2)]

uc

mixing layer convection velocity [=(u 1+u 2)/2]

ue

free-stream velocity (at 470 mm upstream)

uo

shear velocity (=u 1u 2)

u1,u2

mean velocities of high and low speed streams, respectively

\(\overline {u'^2 } \)

Reynolds streamwise normal stress

\(\overline {v'^2 } \)

Reynolds cross-stream normal stress

\(\overline {w'^2 } \)

Reynolds spanwise normal stress

\(\overline {u'v'} \)

Reynolds primary shear stress

x, y

streamwise and cross-stream directions, respectively

xo

virtual origin of the mixing layer

y0.1

isovel for u =0.1; similarly for y 0.05, y 0.5, y 0.9 and y 0.95

()max

max maximum value at given x location

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References

  1. Bell JH, Mehta RD (1990) Development of a two-stream mixing layer with tripped and untripped boundary layers. AIAA J 28:2034–2042CrossRefGoogle Scholar
  2. Bradshaw P (1966) The effect of initial conditions on the development of a free shear layer. J Fluid Mech 26:225–236CrossRefGoogle Scholar
  3. Browand FK, Latigo BO (1979) Growth of the two-dimensional mixing layer from a turbulent and non-turbulent boundary layer. Phys Fluids 22:1011–1019CrossRefGoogle Scholar
  4. Chandrsuda C, Mehta RD, Weir AD, Bradshaw P (1978) Effect of free stream turbulence on large structure in turbulent mixing layer. J Fluid Mech 85:693–704CrossRefGoogle Scholar
  5. Dziomba B, Fiedler HE (1985) Effect of the initial conditions on two-dimensional free shear layer. J Fluid Mech 152:419–442CrossRefGoogle Scholar
  6. Fiedler H, Thies H (1978) Some observations in a large two-dimensional shear layer. In: Fiedler H (ed) Proceedings of the Symposium on Turbulence I. Springer, pp 108–117Google Scholar
  7. Ho CM, Huerre P (1984) Perturbed free shear layer. Ann Rev Fluid Mech 16:365–424CrossRefGoogle Scholar
  8. Hussain AKMF, Zedan MF (1978a) Effect of the initial condition on the axisymmetric free shear layer: Effects of the initial momentum thickness. Phys Fluids 21:1100–1112CrossRefGoogle Scholar
  9. Hussain AKMF, Zedan MF (1978b) Effect of the initial condition on the axisymmetric free shear layer: Effects of the initial fluctuation level. Phys Fluids 21:1475–1481CrossRefGoogle Scholar
  10. Mehta RD (1991) Effects of velocity ratio on plane mixing layer development: Influence of the splitter plate wake. Exp Fluids 10 (4):194–204CrossRefGoogle Scholar
  11. Mehta RD, Westphal RV (1986) Near-field turbulence properties of single-and two-stream plane mixing layers. Exp Fluids 4:257–266CrossRefGoogle Scholar
  12. Oster D, Wygnanski IJ (1982) The forced mixing layer between parallel streams. J Fluid Mech 123:91–130CrossRefGoogle Scholar
  13. Pui NK, Gartshore IS (1979) Measurements of the growth rate and structure in plane turbulent mixing layers. J Fluid Mech 91:111–130CrossRefGoogle Scholar
  14. Townsend AA (1976) Structure of turbulent shear flow. Cambridge University PressGoogle Scholar
  15. Wood DH, Bradshaw P (1984) A turbulent mixing layer constrained by a solid surface, part 2. Measurements in the wall-bounded flow. J Fluid Mech 139:347–361CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringBangladesh University of Engineering and TechnologyDhakaBangladesh

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