Impact of flow-induced disturbances during synthesis on the photophysical properties of naphthalene diimide covalent organic frameworks

Flow-induced disturbances were applied during the synthesis of a naphthalene diimide covalent organic framework (NDI-COF), which resulted in different COF polymer networks. We discovered that a high intensity of stirring resulted in more aggregated structures on both the micro- and nano-length scale. Subsequently, these structures absorbed...

Turbulent shear flow over complex surfaces: An experimental study

This thesis describes the investigation of the dynamics of turbulent shear flows over non-smooth surfaces. The research was conducted in two parts, related to the experimental facility used in combination with the applied functional surface. The first part describes the experiments of a turbulent Taylor-Couette flow over a...

Particle-laden Taylor-Couette flows: Higher-order transitions and evidence for azimuthally localized wavy vortices

We extend upon the known flow transitions in neutrally buoyant particle-laden Taylor-Couette flows by accessing higher suspension Reynolds numbers in a geometry with radius ratio and aspect ratio. Flow transitions for several particle volume fractions () are investigated by means of flow visualization experiments, in a flow driven by a...

Large-scale structure transitions in turbulent Taylor–Couette flow

We report on the experimental investigation of the large-scale instantaneous flow structures in turbulent Taylor–Couette flow using tomographic particle image velocimetry. The results indicate three distinct regimes for counter-rotating flow within a shear Reynolds number range of 11000<ReS<47000 . Close to only inner cylinder rotation,...

Suspension Taylor-Couette flow: Investigation of particle loading effects on transitions between flow regimes

Taylor-Couette (TC) flow refers to the flow in the annulus between two coaxial, independently rotating cylinders. The TC system has been subject to multiple experiments spanning over decades due to the instability phenomena that occur in the flow. When the rotation rates of the cylinders are increased beyond a critical value, instabilities...

Experimental investigation of torque hysteresis behaviour of Taylor–Couette Flow

This paper describes the hysteresis in the torque for Taylor–Couette flow in the turbulent flow regime for different shear Reynolds numbers, aspect ratios and boundary conditions. The hysteresis increases with decreasing shear Reynolds number and becomes more pronounced as the aspect ratio is increased from 22 to 88. Measurements conducted in...

Turbulent Spot in Linearly Stable Taylor Couette Flow

The transition from the laminar to the turbulent regime in linearly stable shear flows, for example, pipe and plane Couette flows, occurs abruptly with no precursor. The evolution of turbulent spots has been studied to better understand the dynamics of this transition and the onset of turbulence. These studies have mostly focused on pipe flows...

Turbulent states in plane Couette flow with rotation

Shearing and rotational forces in fluids can significantly alter the transport of momentum. A numerical investigation was undertaken to study the role of these forces using plane Couette flow subject to rotation about an axis perpendicular to both wall-normal and streamwise directions. Using a set of progressively higher Reynolds numbers up to...

Coherent Structures in Taylor-Couette Flow: Experimental Investigation

Taylor-Couette flow is defined as the flow confined between two coaxial cylinders which can rotate independently. Several different flow states can be observed in the gap between the cylinders by changing the rotation speeds and the rotating directions of the cylinders. The aim of this thesis is to investigate the previously reported change of...

Breakup of polystyrene particles in turbulent Taylor-Couette flow: Vallidation of a DNS model for asphaltene agglomeration

The study of polystyrene particles in Talor-Couette flow for the vallidation of a DNS code for asphaltene agglomeration

Transition to turbulence in Taylor Couette flow

The most recent studies of intermittent state in linearly stable shear flows, like pipe, Plane Couette and Taylor Couette flow, have shown that turbulent structures, created by finite-amplitude perturbation, have an exponential distribution of the lifetimes. Here we experimentally examine the lifetime of turbulent spot in Taylor Couette flow ...

The magnetorotational instability in cylindrical Taylor-Couette flow

We consider the flow of an electrically conducting fluid between differentially rotating cylinders, in the presence of an externally imposed magnetic field. Several codes are presented to study this problem, consisting of linear eigenvalue and nonlinear time-stepping programs. Depending on whether the magnetic Reynolds number is small or large,...

Magnetohydrodynamics in a domain bounded by a spherical surface: A Fourier-spectral element approximation involving a Dirichlet to Neumann operator for the resolution of the exterior problem

We present a Fourier-spectral element approximation of electromagnetic induction (and magnetohydrodynamics) in a domain bounded by a spherical interface. The electromagnetic problem is cast in terms of electromagnetic potentials, the uniqueness of which is enforced by the choice of Coulomb's gauge. A PN - PN-2 approach ensures the solenoidal...