Premium
Experimental observations of the splitting of a gravity current at a density step in a stratified water body
Author(s) -
Cortés A.,
Rueda F. J.,
Wells M. G.
Publication year - 2014
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2013jc009304
Subject(s) - gravity current , froude number , interflow , buoyancy , stratified flow , neutral buoyancy , stratification (seeds) , current (fluid) , stratified flows , geology , density contrast , boundary current , mechanics , richardson number , current density , physics , geophysics , flow (mathematics) , internal wave , ocean current , oceanography , geotechnical engineering , turbulence , groundwater , biology , germination , quantum mechanics , seed dormancy , botany , astronomy , dormancy
When a gravity current reaches the level of neutral buoyancy in a stratified water body it can separate from the sloping boundary as an intrusion. If there is a density gradient within the gravity current, then multiple intrusions can form in the stratified water body. Using a series of laboratory experiments in a two‐layered ambient stratification, we document how a gravity current splits in two upon reaching the sharp density step. Our laboratory observations stress the significance of the densimetric Froude number of the gravity current ( Fr ), as well as a measure of the ambient stratification (density Richardson number, Ri ρ ), on determining how a gravity current intrudes into a two‐layered stratified ambient water. Gravity currents are more likely to detrain into two parts at a density step when they have a diffuse density interface ( Fr > 1). However, gravity currents tend to intrude as a single intrusion when they have a sharp, more step‐like density profile ( Fr < 1). Using details of the internal structure of the gravity current, we develop a theory to predict the partition of the buoyancy flux into the interflow and underflow when the gravity current splits at the density step. Our predictions of buoyancy portions are in agreement with our experimental observations. We discuss when the application of our equations will be relevant for river intrusions into reservoirs, and for gravity currents in the stratified ocean.