LABORATORY SIMULATION OF TURBULENT-LIKE FLOWS

Most turbulence studies up to the present are based on statistical modeling, however, the spatio-temporal flow structure of the turbulence is still largely unexplored. Tur- bulence has been established to have a multi-scale instantaneous streamline structure which influences the energy spectrum and other properties such as dissipation and mixing. In an attempt to further understand the fundamental nature of turbulence and its consequences for efficient mixing, a new class of flows, so called “turbulent-like”, is in- troduced and its spatio-temporal structure of the flows characterised. These flows are generated in the laboratory using a shallow layer of brine and controlled by multi-scale electromagnetic forces resulting from a combination of electric current and a magnetic field created by a fractal permanent magnet distribution. These flows are laminar, yet turbulent-like, in that they have multi-scale streamline topology in the shape of “cat’s eyes” within “cat’s eyes” (or 8’s within 8’s) similar to the known schematic streamline structure of two-dimensional turbulence. Unsteadiness is introduced to the flows by means of time-dependent electrical current. Particle Tracking Velocimetry (PTV) measurements are performed. The technique developed provides highly resolved Eulerian velocity fields in space and time. The analysis focuses on the impact of the forcing frequency, mean intensity and amplitude on various Eulerian and Lagrangian properties of the flows e.g. energy spectrum and fluid element dispersion statistics. Other statistics such as the integral length and time scales are also extracted to characterise the unsteady multi-scale flows. The research outcome provides the analysis of laboratory generated unsteady multi- scale flows which are a tool for the controlled study of complex flow properties related to turbulence and mixing with potential applications as efficient mixers as well as in geophysical, environmental and industrial fields

Laboratory simulation of turbulent-like flows

Most turbulence studies up to the present are based on statistical modeling, however,the spatio-temporal flow structure of the turbulence is still largely unexplored. Tur-bulence has been established to have a multi-scale instantaneous streamline structurewhich influences the energy spectrum and other properties such as dissipation andmixing. In an attempt to further understand the fundamental nature of turbulence and itsconsequences for efficient mixing, a new class of flows, so called ?turbulent-like?, is in-troduced and its spatio-temporal structure of the flows characterised. These flows aregenerated in the laboratory using a shallow layer of brine and controlled by multi-scaleelectromagnetic forces resulting from a combination of electric current and a magneticfield created by a fractal permanent magnet distribution. These flows are laminar, yetturbulent-like, in that they have multi-scale streamline topology in the shape of ?cat?seyes? within ?cat?s eyes? (or 8?s within 8?s) similar to the known schematic streamlinestructure of two-dimensional turbulence. Unsteadiness is introduced to the flows bymeans of time-dependent electrical current. Particle Tracking Velocimetry (PTV) measurements are performed. The techniquedeveloped provides highly resolved Eulerian velocity fields in space and time. Theanalysis focuses on the impact of the forcing frequency, mean intensity and amplitudeon various Eulerian and Lagrangian properties of the flows e.g. energy spectrum andfluid element dispersion statistics. Other statistics such as the integral length and timescales are also extracted to characterise the unsteady multi-scale flows. The research outcome provides the analysis of laboratory generated unsteady multi-scale flows which are a tool for the controlled study of complex flow properties relatedto turbulence and mixing with potential applications as efficient mixers as well as ingeophysical, environmental and industrial fields.EThOS - Electronic Theses Online ServiceGBUnited Kingdo