cases:case053

# Backward-Facing Inclined Step

The case considered is of flow over an inclined backward-facing step, as shown in figure 1.

Fig. 1: Flow configuration

A number of cases have been considered, with step expansion angles of $\alpha=10^o$, $15^o$, $20^o$, $25^o$, $30^o$, $45^o$ and $90^o$, for channel expansion ratios $h_2/h_1=1.48$, $2$ and $3.27$, and Reynolds numbers $Re_H$ ranging from 5000 to 64000.

The closed-loop wind tunnel had a test section made of glass, to allow optical accessibility for a laser Doppler anemometry system. The inlet section was of sufficient length (over 100 step heights in the $ER=2$ case) to ensure fully developed flow conditions upstream of the step. The channel width of up to $40H$ ensured sufficient two-dimensionality of the flow on the central plane, where measurements were taken. To vary the step geometry, different shaped wedges were inserted into the test section.

The LDA measurements were carried out using a dual beam anemometer system including a 25mW HeNe laser. The LDA system was equipped with double Bragg cells and worked in the forward light scatter mode. A transient recorder (Iwatsu DM-901) in combination with a microcomputer was used to process the LDA signals. The data evaluation was performed by a software discrimination scheme based on the comparison of the cycle length within signal bursts.

The table below indicates all the parameter configurations investigated.

Reynolds Number
$ER$ $\alpha$ [o] 5000 8000 11000 15000 33000 47000 64000
1.48 90 X X X X X X
1.48 45 X X X
1.48 30 X X X X X
1.48 25 X X X X X X
1.48 20 X X X X X X
1.48 15 X X X X X X
1.48 10 X X X X X X
2.0 90 X X X X
2.0 45 X X X
2.0 30 X X X X
2.0 25 X X X
2.0 20 X X X
2.0 15 X X X
2.0 10 X X X
3.27 90 X X X X
3.27 25 X X X X
3.27 20 X X X X
3.27 15 X X X X

The following data are available for each case measured:

• Profiles across the channel of mean and rms streamwise velocity at selected $x$ locations
• Normalized streamfunction profiles across the channel at selected $x$ locations
• Reattachment length

Sample plots of selected quantities are available.

The data files can be downloaded as compressed archives from the links below, or as individual files from the table.

The file readme.txt outlines the file name convention, and data organisation within the files.

1. Makiola, B. (1992). Ph.D. Thesis, University of Karlsruhe.
2. Ruck, B., Makiola, B. (1993). Flow separation over the step with inclined walls. Near-Wall Turbulent Flows (Eds. R.M.C. So, C.G. Speziale, B.E. Launder), Elsevier.

Indexed data:

case053 (dbcase, confined_flow)
case053
titleBackward-facing inclined step
authorRuck, Makiola
year1992
typeEXP
flow_tag2d, separated, varying_cross_section