Influence of Diurnal Heating on a Stratified Open Channel Flow
Abstract
This study employs direct numerical simulation (DNS) to investigate stably stratified open channel flows that are subjected to a time-varying surface radiative forcing whose function is approximated by a diel solar heating cycle. This paper follows from the earlier work of a statistically steady state open channel flow with a constant heat source. The simulations have a Prandtl number Pr of 1 and a friction Reynolds number Reτ of 400. It's bulk buoyancy parameter λ of 1, defined by the ratio of the channel depth δ and a bulk Obukhov length scale L , corresponds to strongly stratified conditions and the diurnal timescales, normalised by the wall friction velocity uτ over δ, cover the range between t* = 6 - 12 . Results demonstrate strong mixing and re-stratification during the ``night and day'' heating cycle. Numerical results have been found to be in agreement with existing parameterisation and scaling relations for the irreversible flux Richardson number Rif* and turbulent Froude number Fr and eddy diffusivity kh and local buoyancy Reynolds number Reb at certain positions along the water column.
- Publication:
-
APS Division of Fluid Dynamics Meeting Abstracts
- Pub Date:
- 2020
- Bibcode:
- 2020APS..DFDP17004N