Discovering hidden natural convective flows in tilted cavities

People

Principal investigator

Supervisor

External Member

Dr Yongling Zhao

Description

Anomalous or hidden convection are stable flow solutions predicted by theory which are difficult to obtain in the real world. Despite their recent scientific interest, to date there is no published flow visualisation of such hidden convection flows. Natural convection in a cubical cavity heated form below will be visualised in this project with the aim of experimentally evaluating the ranges of existence of such flows. The flow is driven by buoyancy caused by the temperature difference and damped by fluid viscosity. Particle image velocimetry (PIV) is applied to visualise the velocity field and phase shifting interferometry (PSI) is used to visualise the temperature field. An measured bifurcation diagram should first be obtained for laminar natural convection in a horizontal rectangular cavity. Then, when the cavity is slightly inclined, a leading stable branch should be observed with the flow rotation in the same direction as the inclination. Next, we should confirm experimentally via flow visualisation that the convection opposite to the inclination (i.e. hidden convection) exists only in a small inclination range. The range of existance for these hidden flows will be experimentally obtained while the flow structure is characterised.

Goals

We aim at discovering experimentally new hidden convective flows in cavities and answering the following research questions:

  1. What is the transient behaviour of the hidden flows while the buoyancy stength and direction are changed?
  2. Can simulation results be validated experimentally with direct visualisation?
  3. What factors not identified in simulation could affect the flow transition in realistic experimental setup?

Requirements

  • Interest in fluid mechanics and fundamental physics
  • Desire to learn new experimental methods
  • Basic programming skills
  • Good communication skills

Background Literature

Scientific papers by Torres et al.

  1. Optical method for simultaneous high-resolution measurement of heat and fluid flow: the case of Rayleigh-Bénard convection. Physical Review Applied 14, 054038 (2020)
  2. Transition from multiplicity to singularity of steady natural convection in a tilted cubical enclosure. Physical Review E 92, 023031 (2015)
  3. Bifurcation analysis of steady natural convection in a tilted cubical cavity with adiabatic sidewalls. Journal of Fluid Mechanics 756, 650–688 (2014)
  4. Three-dimensional continuation study of convection in a tilted rectangular enclosure. Physical Review E 88, 043015 (2013)

Keywords

convection; hidden flow; thermofluids; fluid mechanics; flow visualisation

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