EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Reynolds stresses in gravity currents approaching an obstacle

Giovanni Di Lollo1, Claudia Adduce1,2, Moisés Brito3, Rui M.L. Ferreira4, and Ana Ricardo5
Giovanni Di Lollo et al.
  • 1Roma Tre, Department of Engineering, Rome, Italy (
  • 2CNR ISMAR,Institute of Marine Sciences, National Research Council, Rome, Italy
  • 3UNIDEMI, Faculdade de Ciências e Tecnologia Department of Mechanical and Industrial Engineering, Caparica, Portugal
  • 4CERIS, Istituto Superior Tecnico, Universidade de Lisboa, Lisbon, Portugal
  • 5CERIS, Lisbon, Portugal

ABSTRACT: Gravity currents are flows generated by density differences within two contacting fluids. In this work the interaction between lock-release gravity currents propagating over a horizontal rectangular channel and an emergent cylinder is analyzed through velocity measurements obtained through PIV. Two-dimensional instantaneous velocity fields are measured in a plane perpendicular to the bottom along the center axis of the channel upstream of the obstacle. The experiments were also conducted without the cylinder for comparison purposes and ten repetitions were carried out for each configuration. The analyses focus on the effects that the presence of an adverse pressure gradient has on both the mean velocity field and the turbulence of the leading part of the current, the head, before the impact. The mean velocity field is not affected by the presence of the obstacle and since no differences were found in the spatial distribution of the mean velocity components, the necessary cylinder-induced deceleration occurs uniformly. Turbulence is studied through the components of the Reynolds stress tensor and their fluxes within the head. In the configuration with the cylinder, there are no fluxes of Reynolds stresses in the inner part of the section. Consequently, the Reynolds stress intensity decreases inside the head compared to the configuration without the obstacle. In conclusion, the presence of an adverse pressure gradient stops the mechanism of Reynolds stress distribution from the main source of production, i.e. the front region, to the inner region of the flow. This leads to a decrease in Reynolds stresses in the inner part of the head and an increase in the frontal region.

Acknowledgements: This work was partially supported by Foundation for Science and Technology's through funding UIDB/04625/2020 (CERIS research unit).

Keywords: Gravity currents, lock release, Particle Image Velocimetry, adverse pressure gradient, Reynolds stress.

How to cite: Di Lollo, G., Adduce, C., Brito, M., Ferreira, R. M. L., and Ricardo, A.: Reynolds stresses in gravity currents approaching an obstacle, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15236,, 2023.