### Abstract

Separation deteriorates airfoil performance and is generally undesirable. In this paper turbulent separation from two different airfoils is investigated. The first airfoil is a modified NACA 64_{3}-618 airfoil. At a chord based Reynolds number of Re=322,000 and for an angle of attack of α = 13.2deg a laminar separation bubble forms near the leading edge and the flow separates turbulent at about mid-chord. For these conditions "coarse" grid direct numerical simulations and unsteady hybrid simulations based on a one-equation renormalization group turbulence model and the filter-based Reynolds-averaged Navier- Stokes model were carried out. The direct simulation was found to suffer from insufficient grid resolution. Results obtained from the hybrid simulations provide an adequate match with the experimental reference data at much reduced computational cost. A procedure for "seeding" turbulence velocity fluctuations in areas where the grid resolution increases in the streamwise direction was found to have no effect on the mean flow data. The second airfoil is a generic laminar airfoil. For Re=2,630,000 and α = 23deg the flow separates near quarterchord. Unsteady Reynolds-averaged Navier-Stokes simulations show a curved separation line which is indicative of stall cells. Attempts to explain the spanwise wavelength of the unsteady and steady spanwise flow structures remained unsuccessful.

Original language | English (US) |
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Title of host publication | 41st AIAA Fluid Dynamics Conference and Exhibit |

State | Published - 2011 |

Event | 41st AIAA Fluid Dynamics Conference and Exhibit 2011 - Honolulu, HI, United States Duration: Jun 27 2011 → Jun 30 2011 |

### Other

Other | 41st AIAA Fluid Dynamics Conference and Exhibit 2011 |
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Country | United States |

City | Honolulu, HI |

Period | 6/27/11 → 6/30/11 |

### Fingerprint

### ASJC Scopus subject areas

- Fluid Flow and Transfer Processes
- Energy Engineering and Power Technology
- Aerospace Engineering
- Mechanical Engineering

### Cite this

*41st AIAA Fluid Dynamics Conference and Exhibit*

**Numerical investigation of separation for airfoils.** / Gross, A.; Fasel, Hermann F.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

*41st AIAA Fluid Dynamics Conference and Exhibit.*41st AIAA Fluid Dynamics Conference and Exhibit 2011, Honolulu, HI, United States, 6/27/11.

}

TY - GEN

T1 - Numerical investigation of separation for airfoils

AU - Gross, A.

AU - Fasel, Hermann F

PY - 2011

Y1 - 2011

N2 - Separation deteriorates airfoil performance and is generally undesirable. In this paper turbulent separation from two different airfoils is investigated. The first airfoil is a modified NACA 643-618 airfoil. At a chord based Reynolds number of Re=322,000 and for an angle of attack of α = 13.2deg a laminar separation bubble forms near the leading edge and the flow separates turbulent at about mid-chord. For these conditions "coarse" grid direct numerical simulations and unsteady hybrid simulations based on a one-equation renormalization group turbulence model and the filter-based Reynolds-averaged Navier- Stokes model were carried out. The direct simulation was found to suffer from insufficient grid resolution. Results obtained from the hybrid simulations provide an adequate match with the experimental reference data at much reduced computational cost. A procedure for "seeding" turbulence velocity fluctuations in areas where the grid resolution increases in the streamwise direction was found to have no effect on the mean flow data. The second airfoil is a generic laminar airfoil. For Re=2,630,000 and α = 23deg the flow separates near quarterchord. Unsteady Reynolds-averaged Navier-Stokes simulations show a curved separation line which is indicative of stall cells. Attempts to explain the spanwise wavelength of the unsteady and steady spanwise flow structures remained unsuccessful.

AB - Separation deteriorates airfoil performance and is generally undesirable. In this paper turbulent separation from two different airfoils is investigated. The first airfoil is a modified NACA 643-618 airfoil. At a chord based Reynolds number of Re=322,000 and for an angle of attack of α = 13.2deg a laminar separation bubble forms near the leading edge and the flow separates turbulent at about mid-chord. For these conditions "coarse" grid direct numerical simulations and unsteady hybrid simulations based on a one-equation renormalization group turbulence model and the filter-based Reynolds-averaged Navier- Stokes model were carried out. The direct simulation was found to suffer from insufficient grid resolution. Results obtained from the hybrid simulations provide an adequate match with the experimental reference data at much reduced computational cost. A procedure for "seeding" turbulence velocity fluctuations in areas where the grid resolution increases in the streamwise direction was found to have no effect on the mean flow data. The second airfoil is a generic laminar airfoil. For Re=2,630,000 and α = 23deg the flow separates near quarterchord. Unsteady Reynolds-averaged Navier-Stokes simulations show a curved separation line which is indicative of stall cells. Attempts to explain the spanwise wavelength of the unsteady and steady spanwise flow structures remained unsuccessful.

UR - http://www.scopus.com/inward/record.url?scp=84883700262&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84883700262&partnerID=8YFLogxK

M3 - Conference contribution

AN - SCOPUS:84883700262

SN - 9781600869471

BT - 41st AIAA Fluid Dynamics Conference and Exhibit

ER -