### Abstract

The effect of the upstream conditions on propagation of gravity current over a slope is investigated using three-dimensional numerical simulations. The current produced by constant buoyancy flux, is simulated using a large eddy simulation solver. The dense saline solution used at the inlet is the driving force of the flow. Higher replenishment of the current is possible either by a high inflow discharge or high initial fractional density excess. In the simulations, it is observed that these two parameters affect the flow in different ways. Results show that the front speed of the descending current is proportional to the cube root of buoyancy flux, (g^{′}_{o}Q)^{1/3}, which agrees with the previous experimental and numerical observations. The height of the tail of the current grows linearly in the streamwise direction. Formation of a strong shear layer at the boundary of mixed upper layer and dense lower layer is observed within the body and the tail of the current. Over the tail of the current far enough from the inlet, the vertical velocity and density profiles are compared to the ones from an experimental study. Distance from the bed to the point of maximum velocity increases with an increase in inflow discharge, while it remains practically unchanged with increasing initial fractional excess density in the simulations. Even though the velocity profiles are in good agreement, some discrepancies are observed in fractional excess density profiles among experimental and numerical results. Possible reasons for these discrepancies are discussed. Generally, gravity current type of flows could be expressed in layer-integrated formulation of governing equations. However, layer integration introduces several constants, commonly known as shape factors, to the equations of motion. The values of these shape factors are calculated based on simulation results and compared to the values from experiments and to the favorably used 'top hat' assumption.

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

Pages (from-to) | 409-429 |

Number of pages | 21 |

Journal | Environmental Fluid Mechanics |

Volume | 14 |

Issue number | 2 |

DOIs | |

State | Published - Apr 2014 |

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### Keywords

- Constant buoyancy flux gravity currents
- Flow profiles
- Initial excess density
- Large eddy simulation

### ASJC Scopus subject areas

- Environmental Chemistry
- Water Science and Technology

### Cite this

**Effect of initial excess density and discharge on constant flux gravity currents propagating on a slope.** / Tokyay, Talia E.; Garcia, Marcelo Horacio.

Research output: Contribution to journal › Article

*Environmental Fluid Mechanics*, vol. 14, no. 2, pp. 409-429. https://doi.org/10.1007/s10652-013-9317-0

}

TY - JOUR

T1 - Effect of initial excess density and discharge on constant flux gravity currents propagating on a slope

AU - Tokyay, Talia E.

AU - Garcia, Marcelo Horacio

PY - 2014/4

Y1 - 2014/4

N2 - The effect of the upstream conditions on propagation of gravity current over a slope is investigated using three-dimensional numerical simulations. The current produced by constant buoyancy flux, is simulated using a large eddy simulation solver. The dense saline solution used at the inlet is the driving force of the flow. Higher replenishment of the current is possible either by a high inflow discharge or high initial fractional density excess. In the simulations, it is observed that these two parameters affect the flow in different ways. Results show that the front speed of the descending current is proportional to the cube root of buoyancy flux, (g′oQ)1/3, which agrees with the previous experimental and numerical observations. The height of the tail of the current grows linearly in the streamwise direction. Formation of a strong shear layer at the boundary of mixed upper layer and dense lower layer is observed within the body and the tail of the current. Over the tail of the current far enough from the inlet, the vertical velocity and density profiles are compared to the ones from an experimental study. Distance from the bed to the point of maximum velocity increases with an increase in inflow discharge, while it remains practically unchanged with increasing initial fractional excess density in the simulations. Even though the velocity profiles are in good agreement, some discrepancies are observed in fractional excess density profiles among experimental and numerical results. Possible reasons for these discrepancies are discussed. Generally, gravity current type of flows could be expressed in layer-integrated formulation of governing equations. However, layer integration introduces several constants, commonly known as shape factors, to the equations of motion. The values of these shape factors are calculated based on simulation results and compared to the values from experiments and to the favorably used 'top hat' assumption.

AB - The effect of the upstream conditions on propagation of gravity current over a slope is investigated using three-dimensional numerical simulations. The current produced by constant buoyancy flux, is simulated using a large eddy simulation solver. The dense saline solution used at the inlet is the driving force of the flow. Higher replenishment of the current is possible either by a high inflow discharge or high initial fractional density excess. In the simulations, it is observed that these two parameters affect the flow in different ways. Results show that the front speed of the descending current is proportional to the cube root of buoyancy flux, (g′oQ)1/3, which agrees with the previous experimental and numerical observations. The height of the tail of the current grows linearly in the streamwise direction. Formation of a strong shear layer at the boundary of mixed upper layer and dense lower layer is observed within the body and the tail of the current. Over the tail of the current far enough from the inlet, the vertical velocity and density profiles are compared to the ones from an experimental study. Distance from the bed to the point of maximum velocity increases with an increase in inflow discharge, while it remains practically unchanged with increasing initial fractional excess density in the simulations. Even though the velocity profiles are in good agreement, some discrepancies are observed in fractional excess density profiles among experimental and numerical results. Possible reasons for these discrepancies are discussed. Generally, gravity current type of flows could be expressed in layer-integrated formulation of governing equations. However, layer integration introduces several constants, commonly known as shape factors, to the equations of motion. The values of these shape factors are calculated based on simulation results and compared to the values from experiments and to the favorably used 'top hat' assumption.

KW - Constant buoyancy flux gravity currents

KW - Flow profiles

KW - Initial excess density

KW - Large eddy simulation

UR - http://www.scopus.com/inward/record.url?scp=84896053494&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84896053494&partnerID=8YFLogxK

U2 - 10.1007/s10652-013-9317-0

DO - 10.1007/s10652-013-9317-0

M3 - Article

AN - SCOPUS:84896053494

VL - 14

SP - 409

EP - 429

JO - Environmental Fluid Mechanics

JF - Environmental Fluid Mechanics

SN - 1567-7419

IS - 2

ER -