### Abstract

Language | English |
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Publication status | Unpublished - Jun 2005 |

Event | 4th AIAA Theoretical Fluid Mechanics Meeting - Toronto, Canada Duration: 6 Jun 2005 → 9 Jun 2005 |

### Conference

Conference | 4th AIAA Theoretical Fluid Mechanics Meeting |
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Country | Canada |

City | Toronto |

Period | 6/06/05 → 9/06/05 |

### Fingerprint

### Keywords

- velocity profiles
- fluid mechanics
- kinetics

### Cite this

*Slip length and problem of anomalous velocity profiles*. Paper presented at 4th AIAA Theoretical Fluid Mechanics Meeting , Toronto, Canada.

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**Slip length and problem of anomalous velocity profiles.** / Dadzie, K.; Meolans, J.G.

Research output: Contribution to conference › Paper

TY - CONF

T1 - Slip length and problem of anomalous velocity profiles

AU - Dadzie, K.

AU - Meolans, J.G.

PY - 2005/6

Y1 - 2005/6

N2 - The most used expression for the slip length in the slip flow regime where slip conditions are needed for flow prediction comes from a Maxwell description of kinetic boundary conditions and depends on one coe dient only. Even if generally associated to the tangential accommodation coe dient, this coe dient equals any kind of kinetic property accommodation coe dients. The slip length so predicted by Maxwell increases strongly for the small values of the Maxwell accommodation coe dient whereas it seems, according to experiments that the slip length keeps a finite value and remains of the mean free path magnitude order. In addition, this enhancement of the Maxwell slip length for the small values of the Maxwell accommodation coe dient leads to some anomalous behaviors in theoretical flow predictions such as the so called inverted velocity profile in the cylindrical Couette flow of rarefied gas. In this work, we consider the calculation of the slip velocity based on another modelling of the gaz/surface interaction which involves distinguishable accommodation co-e dients for the normal and the tangential momentum components. The result shows that the slip length remains in the magnitude order of the mean free path when the values of the various momentum accommodation coe dients are varying. Then, the flow anomalous behaviors exhibited in flow fields where the boundary effects become important should be due to the unsuitable application of the Maxwell diffuse-specular boundary conditions for small values of the Maxwell accommodation coe dient. These anomalous behaviors should disappear when more accurate description of the boundary conditions was used.

AB - The most used expression for the slip length in the slip flow regime where slip conditions are needed for flow prediction comes from a Maxwell description of kinetic boundary conditions and depends on one coe dient only. Even if generally associated to the tangential accommodation coe dient, this coe dient equals any kind of kinetic property accommodation coe dients. The slip length so predicted by Maxwell increases strongly for the small values of the Maxwell accommodation coe dient whereas it seems, according to experiments that the slip length keeps a finite value and remains of the mean free path magnitude order. In addition, this enhancement of the Maxwell slip length for the small values of the Maxwell accommodation coe dient leads to some anomalous behaviors in theoretical flow predictions such as the so called inverted velocity profile in the cylindrical Couette flow of rarefied gas. In this work, we consider the calculation of the slip velocity based on another modelling of the gaz/surface interaction which involves distinguishable accommodation co-e dients for the normal and the tangential momentum components. The result shows that the slip length remains in the magnitude order of the mean free path when the values of the various momentum accommodation coe dients are varying. Then, the flow anomalous behaviors exhibited in flow fields where the boundary effects become important should be due to the unsuitable application of the Maxwell diffuse-specular boundary conditions for small values of the Maxwell accommodation coe dient. These anomalous behaviors should disappear when more accurate description of the boundary conditions was used.

KW - velocity profiles

KW - fluid mechanics

KW - kinetics

UR - http://multiscaleflows.mecheng.strath.ac.uk/kokou.html

M3 - Paper

ER -