Critical-Layer Absorption in Stratified Flows
Abstract
LONG-TERM GOALS. The long-term goal of this research program is to study the fundamental mechanisms responsible for the formation and maintenance of oceanic microstructure and to develop parameterizations for the transport of heat, salt and momentum through oceanic layers that are rich in microstructure. SCIENTIFIC OBJECTIVES. The objective of this research program is to investigate the interaction of stratified shear layers with internal waves forced by ambient sources (such as bathymetry, turbulence and wind forcing) through various mechanisms, for example, the critical-layer absorption and degeneration due to enhanced local shear. APPROACH. The approach is mainly laboratory experimental, wherein internal waves are mechanically forced by using an oscillating flap or a corrugated topography. The waves are allowed to interact with the shear flow and break due to critical-layer absorption or another instability mechanism, thus dissipating energy and producing a turbulent patch. Two types of water channels are employed for the study, namely, either an Odell-Kavasznay type recirculating water channel or a counterflow type stratified water tunnel. In the former case, the stratified shear flow is driven over the topography by a disk pump whereas in the latter the internal waves are generated in the stratified shear layer by the oscillating flap. Laser-induced fluorescence, laser-Doppler velocimetry, hot-film anemometry, Particle-image velocimetry and vertically traversing (shooting) conductivity probes are used for flow diagnostics. The measurements include the buoyancy flux, dissipation of turbulent kinetic energy, local and bulk gradient Richardson numbers and the production of turbulent kinetic energy in the shear layer.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 1997
- Accession Number
- ADA634803
Entities
People
- Harindra Fernando
Organizations
- Arizona State University