# Asymmetric plane diffuser

*Authors: Buice, C.U. and Eaton, J.K.*
*Type: Experimental*

*Status*:

## Contents

Description
Flow Parameters

Reference Publications

Results

## Description

Flow in a plane asymmetric diffuser. The flow separates from the inclined surface. The flow is two-dimensional.

This flow includes three important features: First, the well defined inlet conditions. The inlet channel flow is turbulent and fully-developed with a Re=20,000 based on the centreline velocity and the channel height. Second, a smooth-wall separation due to an adverse pressure gradient is involved. The prediction of the separation point and the extent of the recirculation region is particularly challenging for computational models. Finally, this flow includes reattachment and redevelopment of the downstream boundary layer.

A sketch of the configuration and the corresponding dimensions can be seen in the figures below:

The geometrical parameters can be seen in table 1.

Parameter |
Value |

%$\alpha$% |
%$atan \frac{3.7}{21}$% |

%$x_1$% |
%$-Rtan(\alpha /2)$% |

%$x_2$% |
%$0$% |

%$x_3$% |
%$Rtan(\alpha /2) cos(\alpha)$% |

%$x_4$% |
%$21h-Rtan(\alpha /2) cos (\alpha)$% |

%$x_5$% |
%$21h$% |

%$x_6$% |
%$21h+Rtan(\alpha / 2)$% |

## Flow Parameters

The Reynolds number, based on the inlet height h and the bulk velocity %$U_b$% is Re=18000.
The experimental set up [1] included an inlet channel with a length of 110h which ensures fully developed turbulent conditions.

### Data available

The following data is available for comparison [1]:

- Pressure coefficient %$Cp = (p-px) / (0.5 \rho U_b^2)$% along the inclined bottom wall and straight top wall. Here, px=-1.7 means static pressure at x/H = -1.7.

- Skin friction coefficient %$cf = \tau_w / (0.5 \rho U_b^2)$% along the inclined bottom wall and the straight top wall.

- U-component of the mean velocity scaled by %$U_b$%.

- Reynolds stresses: uu, uv, and vv scaled by %$U_b^2$%.

## Reference Publications

[1] Buice, C.U. and Eaton, J.K., Experimental investigation of flow through an asymmetric plane diffuser. Technical Report TSD-107, Departement of mechanical engineering, Stanford University, 1997

[2] Obi, S., Aoki, K. and Masuda, S., Experimental and computational study of turbulent separating flow in a symmetric plane diffuser. In F. Durst, N. Kasagi, B.E. Launder, F.W. Schmidt, K. Suzuki and J.H. Whitelaw, editors, Proceedings 9th Symposium of turbulent shear flow, Kyoto, Japan, August, 1993

## Results

Simulation results available for this case:

Number of topics: 3

.

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