Summary
Unsteady boundary layer separation is one of the essential phenomena in fluid mechanics which is still not fully understood. The well known Moore-Rott-Sears criterion (MRS) states that the onset of separation is reached if in a coordinate system moving with the separation point both the velocity parallel to the wall and its normal derivative vanish at one point simultaneously. This is a good approach to identify an upstream moving separation. It can be refined by considering three distinguished points in order to specify the separation. Those are (1) the MRS point, (2) the Onset of Reverse Flow of the separation region (ORF) and (3) the Stagnation point (STG) within the boundary layer. For a downstream moving separation point, however, the up-to-now published streamline pictures seem to be incorrect. A new separation flow pattern for that case as well as a new criterion to describe it will be suggested.
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Abbreviations
- a,b:
-
constants
- L :
-
characteristic length
- p:
-
static pressure
- pe :
-
external flow static pressure
- Re:
-
Reynolds number (
$$\frac{{{U}_{0}}L}{v}$$)
- t:
-
time
- u, v:
-
flow components in x- and y-direction
- Ue :
-
external flow velocity
- Uo :
-
reference velocity
- U1 :
-
velocity at the downstream boundary of the computational area
- Uw, Vw :
-
wall velocities in x- and y-direction
- x, y:
-
wall fixed coordinate system
- X1 :
-
x-coordinate at the downstream boundary of the computational area
- XI :
-
x-coordinate at a specified point of the computational area
- δ:
-
boundary layer thickness
- v:
-
kinematic viscosity
- MRS:
-
Moore-Rott-Sears
- ORF:
-
Onset of Reverse Flow of the separated region
- STG:
-
Stagnation
- WJ:
-
Williams-Johnson
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© 1997 Friedr. Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig/Wiesbaden
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Ranke, H., Henkner, J. (1997). Refined Streamline Patterns for Unsteady Boundary Layer Separation. In: Körner, H., Hilbig, R. (eds) New Results in Numerical and Experimental Fluid Mechanics. Notes on Numerical Fluid Mechanics (NNFM), vol 60. Vieweg+Teubner Verlag, Wiesbaden. https://doi.org/10.1007/978-3-322-86573-1_33
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DOI: https://doi.org/10.1007/978-3-322-86573-1_33
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