### Abstract

Predictions of the flow over a wall-mounted hump are obtained using solutions of the Reynolds-averaged Navier-Stokes (RANS) equations and detached-eddy simulation (DES). The upstream solution is characterized by a two-dimensional turbulent boundary layer with a thickness approximately half of the maximum hump thickness measured at a location about two chord lengths upstream of the leading edge. The Reynolds number based on the hump chord length is 9.75 × 10 ^{5}. A slot at approximately 65% chord C is used for flow control via a spatially uniform (with respect to the spanwise coordinate) steady suction and with alternating suction/blowing. Solutions of the two- and three-dimensional RANS equations are obtained using the Spalart-Allmaras (S-A) and shear-stress-transport (SST) turbulence models. DES is applied to a three-dimensional geometry corresponding to an extruded section of the hump. DES predictions of the baseline case exhibit a three-dimensional chaotic structure in the wake, with a mean reverse-flow region that is 20% shorter than predicted by the two-dimensional RANS computations and a mean reattachment length that is in good agreement with measurements. DES predictions of the pressure coefficient in the separated-flow region for the baseline case also exhibit good agreement with measurements and are more accurate than either the S-A or SST RANS results. The simulations also show that blockage effects in the experiments used to assess the predictions are important: three-dimensional RANS predictions more accurately predict the pressure distribution upstream and over the front portion of the hump. Predictions of the steady suction case show a reduction in the length of the reverse-flow region, though are less accurate compared to the baseline configuration. Unsteady two-dimensional RANS predictions of the sinusoidal suction/blowing case are used to investigate impedance affects associated with increases in the driving velocity. The simulations show that a factor of four increase in the cavity driving velocity increases the average velocity through the slot by only a factor of 2.7.

Original language | English (US) |
---|---|

Pages (from-to) | 252-262 |

Number of pages | 11 |

Journal | AIAA Journal |

Volume | 44 |

Issue number | 2 |

DOIs | |

State | Published - Feb 2006 |

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### ASJC Scopus subject areas

- Aerospace Engineering

### Cite this

*AIAA Journal*,

*44*(2), 252-262. https://doi.org/10.2514/1.13174

**Prediction of separated flow characteristics over a hump.** / Krishnan, Vivek; Squires, Kyle; Forsythe, James R.

Research output: Contribution to journal › Article

*AIAA Journal*, vol. 44, no. 2, pp. 252-262. https://doi.org/10.2514/1.13174

}

TY - JOUR

T1 - Prediction of separated flow characteristics over a hump

AU - Krishnan, Vivek

AU - Squires, Kyle

AU - Forsythe, James R.

PY - 2006/2

Y1 - 2006/2

N2 - Predictions of the flow over a wall-mounted hump are obtained using solutions of the Reynolds-averaged Navier-Stokes (RANS) equations and detached-eddy simulation (DES). The upstream solution is characterized by a two-dimensional turbulent boundary layer with a thickness approximately half of the maximum hump thickness measured at a location about two chord lengths upstream of the leading edge. The Reynolds number based on the hump chord length is 9.75 × 10 5. A slot at approximately 65% chord C is used for flow control via a spatially uniform (with respect to the spanwise coordinate) steady suction and with alternating suction/blowing. Solutions of the two- and three-dimensional RANS equations are obtained using the Spalart-Allmaras (S-A) and shear-stress-transport (SST) turbulence models. DES is applied to a three-dimensional geometry corresponding to an extruded section of the hump. DES predictions of the baseline case exhibit a three-dimensional chaotic structure in the wake, with a mean reverse-flow region that is 20% shorter than predicted by the two-dimensional RANS computations and a mean reattachment length that is in good agreement with measurements. DES predictions of the pressure coefficient in the separated-flow region for the baseline case also exhibit good agreement with measurements and are more accurate than either the S-A or SST RANS results. The simulations also show that blockage effects in the experiments used to assess the predictions are important: three-dimensional RANS predictions more accurately predict the pressure distribution upstream and over the front portion of the hump. Predictions of the steady suction case show a reduction in the length of the reverse-flow region, though are less accurate compared to the baseline configuration. Unsteady two-dimensional RANS predictions of the sinusoidal suction/blowing case are used to investigate impedance affects associated with increases in the driving velocity. The simulations show that a factor of four increase in the cavity driving velocity increases the average velocity through the slot by only a factor of 2.7.

AB - Predictions of the flow over a wall-mounted hump are obtained using solutions of the Reynolds-averaged Navier-Stokes (RANS) equations and detached-eddy simulation (DES). The upstream solution is characterized by a two-dimensional turbulent boundary layer with a thickness approximately half of the maximum hump thickness measured at a location about two chord lengths upstream of the leading edge. The Reynolds number based on the hump chord length is 9.75 × 10 5. A slot at approximately 65% chord C is used for flow control via a spatially uniform (with respect to the spanwise coordinate) steady suction and with alternating suction/blowing. Solutions of the two- and three-dimensional RANS equations are obtained using the Spalart-Allmaras (S-A) and shear-stress-transport (SST) turbulence models. DES is applied to a three-dimensional geometry corresponding to an extruded section of the hump. DES predictions of the baseline case exhibit a three-dimensional chaotic structure in the wake, with a mean reverse-flow region that is 20% shorter than predicted by the two-dimensional RANS computations and a mean reattachment length that is in good agreement with measurements. DES predictions of the pressure coefficient in the separated-flow region for the baseline case also exhibit good agreement with measurements and are more accurate than either the S-A or SST RANS results. The simulations also show that blockage effects in the experiments used to assess the predictions are important: three-dimensional RANS predictions more accurately predict the pressure distribution upstream and over the front portion of the hump. Predictions of the steady suction case show a reduction in the length of the reverse-flow region, though are less accurate compared to the baseline configuration. Unsteady two-dimensional RANS predictions of the sinusoidal suction/blowing case are used to investigate impedance affects associated with increases in the driving velocity. The simulations show that a factor of four increase in the cavity driving velocity increases the average velocity through the slot by only a factor of 2.7.

UR - http://www.scopus.com/inward/record.url?scp=33645165554&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33645165554&partnerID=8YFLogxK

U2 - 10.2514/1.13174

DO - 10.2514/1.13174

M3 - Article

AN - SCOPUS:33645165554

VL - 44

SP - 252

EP - 262

JO - AIAA Journal

JF - AIAA Journal

SN - 0001-1452

IS - 2

ER -