Forces and torques in twodimensional turbulence and their applications
Download (9.88 MB)

Altmetric Citations
Description
Since the discovery of twodimensional (2D) turbulence in Faraday waves a decade ago, understanding of such phenomena has advanced greatly. The discovery of coherent bundles in such flows introduced a new way of exploiting 2D turbulence. This led to the development of devices capable of selfpropelling in turbulent flows and offered novel ways of extracting energy stored in the inertial range of turbulence. Forces and torques acting on solid objects in turbulence require better understanding to...[Show more]
dc.contributor.author  Davoodianidalik, Mahdi  

dc.date.accessioned  20220613T07:43:42Z  
dc.date.available  20220613T07:43:42Z  
dc.identifier.uri  http://hdl.handle.net/1885/267269  
dc.description.abstract  Since the discovery of twodimensional (2D) turbulence in Faraday waves a decade ago, understanding of such phenomena has advanced greatly. The discovery of coherent bundles in such flows introduced a new way of exploiting 2D turbulence. This led to the development of devices capable of selfpropelling in turbulent flows and offered novel ways of extracting energy stored in the inertial range of turbulence. Forces and torques acting on solid objects in turbulence require better understanding to optimise these methods for practical applications. Here I study the interaction forces acting between two solid objects, and torques acting on solid disks of different diameters in 2D turbulence. I demonstrate how the improved understanding of these interactions helps to control the growth of bacterial cellulose (BC) in the Faraday wavedriven turbulence. Understanding forces generated in nonequilibrium systems is a significant challenge in statistical and biological physics. The generation of forces between passive inclusions in nonequilibrium systems underpins many phenomena in nature. The most celebrated of these fluctuationinduced forces is the quantum Casimir force. The phenomenon of force generation observed in other systems, has not yet been studied in classical hydrodynamic turbulence. Here, we present evidence of the attractive force mediated via turbulent fluctuations by using two walls which locally confine 2D turbulence. An optical fibre is used as a force probe in these studies, which provides a simple, reliable and accurate method for measuring such forces. In such a strongly nonlinear system, dominated by the energy cascades and spatiotemporal chaos, we show that the longrange interaction is a function of the wall separation and the energy injection rate into the turbulent flow. The magnitude of the attractive force increases with the turbulence kinetic energy. As the wall spacing decreases, the confined flow becomes less energetic and more anisotropic in the bounded domain, producing stronger attraction. We propose a model to calculate the attraction force using turbulence parameters. The mechanism of force generation is rooted in a nontrivial fluidwall coupling where coherent flow structures are guided by the cavity in between the walls. For the narrowest cavities studied, a resonance phenomenon at the flow forcing scale leads to a complex shortrange interaction. Complementary to studying force acting on straight walls, we experimentally study the rotational dynamics of a circular disk in 2D turbulence. A stochastic process can describe the dynamics of the angular motion. The effect of the forcing scale on the measured rotational motion is studied. It is found that the meansquared angular displacement (MSAD) is diffusive at long times. We demonstrate how the rotational dynamics of a disk with a diameter smaller than the forcing scale of turbulence couples with coherent bundles. The rotational kinetic energy of the disk is determined, and the change of this parameter with the ratio of the disk size over the forcing scale in the 2D turbulence is demonstrated. The results highlight the importance of interactions between meandering bundles of fluid particles, recently found in such a turbulence. Based on the understanding obtained from studying the interacting forces of passive particles, we introduce living organisms to such flow condition. Bacterial cellulose (BC), a biopolymer synthesised by bacteria, has attracted much attention recently as a potential sustainable biomaterial. In this work, under the influence of surface wavedriven turbulent flow, the bacterial cellulose forms spherical beads whose diameter is determined by the characteristic scale of the flow. This ability, to alter the properties and the structure of the BC, will potentially broaden its industrial applications in, for example, tissue engineering, paper manufacturing, electronics, and filtration membranes.  
dc.language.iso  en_AU  
dc.title  Forces and torques in twodimensional turbulence and their applications  
dc.type  Thesis (PhD)  
local.contributor.supervisor  Xia, Hua  
local.contributor.supervisorcontact  u4032076@anu.edu.au  
dc.date.issued  2022  
local.contributor.affiliation  Research School of Physics, ANU College of Science, The Australian National University  
local.identifier.doi  10.25911/QM1KP657  
dc.provenance  The restriction of chapter 3/4 was approved for 12 months until 20230628  
local.identifier.proquest  Yes  
local.thesisANUonly.author  81acee9b1dcf40feb71ab2b8efbc6160  
local.thesisANUonly.title  000000016010_TC_1  
local.thesisANUonly.key  b43dc28069a205f6a21edf28283e3177  
local.mintdoi  mint  
Collections  Open Access Theses 
Download
File  Description  Size  Format  Image 

M.Davoodianidalik_2022_Open Access_Chapter 1 and 2 and 5.pdf  9.88 MB  Adobe PDF  
M.Davoodianidalik_2022_Restricted Chapter 3 and 4.pdf  8.25 MB  Adobe PDF  Request a copy 
Items in Open Research are protected by copyright, with all rights reserved, unless otherwise indicated.
Updated: 19 May 2020/ Responsible Officer: University Librarian/ Page Contact: Library Systems & Web Coordinator