Physical simulations of natural phenomena usually boil down to solving an ordinary or partial differential equation system. Partial differential equation systems can be formulated either in differential form or in integral form. This dissertation explores integral methods for the simulation of magnetic fluids, so-called ferrofluids, and the surface of the vast ocean. The first two parts of this dissertation aim to contribute to the development of accurate and efficient methods for simulating ferrofluids on the macroscopic (in the order of millimeters) scale. The magnetic nature of these fluids imposes challenges for the simulation. The two most important challenges are to first model the influence of ferrofluids on surrounding magnetic fields and second the influence of magnetic forces on the fluids’ dynamics. To tackle these challenges, two Lagrangian simulation methods have been proposed. The first method discretizes the magnetic substance as clusters of particles carrying radial basis functions and applies magnetic forces between these particles. This is a mesh-free method suitable for particle-based fluid simulation frameworks such as smoothed-particle hydrodynamics. The second method follows another direction, only discretizing the fluid’s surface as triangles and vertices. A surface-based simulation for the fluid part is employed, and a boundary element method is utilized for the magnetic part. The magnetic forces are added as gradients of the magnetic energy defined on the fluid’s surface. The second approach has to solve significantly fewer unknowns in the underlying equations, and uses a more accurate surface tension model compared to the radial basis function approach. The proposed methods are able to reproduce a series of characteristic phenomena of magnetic fluids, both qualitatively and in some cases even quantitatively which leads to a better understanding of such kind of materials. The boundary element method employed in the second part shows advantages beyond ferrofluids. In the third part of this thesis, a boundary element method is coupled with a particle-based fluid simulator for ocean simulation. The wavy motion of the ocean is simulated using large triangle meshes, while water splashes are simulated using particles. This approach is much more efficient in terms of computation time and memory consumption.

Ferrofluids are stable colloidal homogeneous mixtures of nano-size single-domain ferromag¬netic particles covered by surfactant layer, and suspended in a carrier fluid compatible with the surfactant. Physical properties of ferrofluid allows one to control it externally using magnetic field without being in direct contact with it. The thesis presents a novel mechanism to pump ferrofluid based on the principle of variable reluctance, in an external magnetic field. The static and dynamic pressure behavior of ferrofluid in a switched DC magnetic field gives an insight into the variable reluctance behavior of ferrofluid. A ferrofluid pump based on the prin¬ciple of variable reluctance of ferrofluid subjected to an external magnetic field, is developed and hence the pump is named as Variable Reluctance Ferrofluid Pump (VRFP). Three configurations of VRFP are developed: • Single stage one-phase VRFP • Single stage two phase VRFP • Multi-stage VRFP A one-phase VRFP consisting of a check valve along with an electromagnet is designed. The valve is modeled and its transfer function is estimated using System Identification method. This model is then used in the simulation model of the pump. The pump is modeled based on the hydraulic-electric analogies. An electric circuit which represents the gross level equivalent of the pump is simulated and the results are compared with that of the experimental measurements. A two phase VRFP is implemented with two electromagnets on either side of the valve around the tube. Two types of magnetic actuation methods are introduced based on the switching sequences of the two electromagnets, namely Full Step Sequencing and Half Step Sequencing. Simulations and experiments were conducted for different pumping conditions. The one phase and two phase VRFPs are single stage structures. A multi-stage VRFP concept, in which the ferrofluid flow channel (tube) is looped through the electromagnets multiple times, is introduced. For the implementation purpose, a two-stage VRFP is discussed in this thesis. Simulations and experiments resulted in significant improvement in case of two-stage VRFP in the pump performance compared to that of single-stage VRFPs. The work presents a simple and novel design of a ferrofluid pump, which is capable of higher flow rates and pumping against higher back pressure compared to the ferrofluid pumps reported in literature. Keywords: Ferrofluid Pump, VRFP, Variable Reluctance, Multi Stage, Magnetic Fluid,

In traditional Permanent Magnet Machines, such as electric motors and generators, power is transmitted by magnetic flux passing through an air gap, which has a very low magnetic permeability, limiting performance. However, reducing the air gap through traditional means carries risks in manufacturing, with tight tolerances and associated costs, and reliability, with thermal and dynamic effects requiring adequate clearance. Using a magnetically permeable, high dielectric strength material has the potential to improve magnetic performance, while at the same time offering performance advantages in heat transfer. Ferrofluids were studied as a method for improved permeability in the rotor / stator gap with a combined experimental and computational approach. Results show promise for the ferrofluid technique. An off-the-shelf motor system showed improved performance with ferrofluids vs. fluids of equivalent viscosity, and improved performance vs. an air gap at low RPM. New generator designs showed design dependent performance gains, although some potential for negative performance effects. A proof of concept generator was built and tested, with increased voltage vs. RPM predicted through virtual prototyping, and validated through experimentation, showing ~10% improvement on voltage vs. RPM at the <600 RPM range. More repeatable engineering tests demonstrated a ~30% increase in the voltage / RPM relationship for designs with an isolated stator chamber and a large stator - rotor gap. However, the effects were negative for a similar system with a small stator-rotor gap due to leakage flux effects. New contributions to the body of knowledge in this area include: • Application of the ferrofluid technique to axial flux designs. • Development of a virtual prototype, including variations in the fluid viscosity due to ferrohydrodynamic effects. • Consideration of negative effects of ferrofluid immersion, such as shear losses and increases in leakage flux. • Optimization of the design to eliminate increased viscous losses. The improved design has been designed, built, and tested, featuring isolation of the ferrofluid from the rotating region. This offers all of the performance gain of improved magnetic permeability, while minimizing the offsetting losses from increased shear effects.

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Apresentamos um novo cristal liquido liotrópico, onde o álcool (utilizado nas misturas liotrópicas com fases nemáticas biaxial e uniaxiais), é substituído por um detergente. Essa nova mistura é composta por laurato de potássio, cloreto de decilamônia e água e apresenta fases nemáticas uniaxiais, calamitica e discótica, e biaxial. É apresentada uma superfície do diagrama de fases dessa mistura e são determinados alguns parâmetros microscópicos. Nesse estudo são utilizadas as técnicas de microscopia óptica de luz polarizada, conoscopia e difração de raios x. É feito um estudo comparativo da estabilidade química desse sistema, em relação à mistura com álcool. É feito um estudo sistemático das propriedades de ancoramento de cristais líquidos liotrópicos em superfícies de vidro (lisas e com ranhuras), utilizando a técnica de microscopia óptica de luz polarizada. Um novo fenômeno é observado, o deslizamento do diretor na superfície de contorno. Um modelo qualitativo, é proposto, baseado na existência de urna bicamada anfifílica, com defeitos, na interface. São determinados os tempo de orientação e tempo de relaxação para as amostras e os resultados são comparados às previsões do modelo proposto. Também é apresentado um método de tratamento de superfícies de vidro para orientação de cristais líquidos liotrópicos. / We present a new lyotropic liquid crystal, where the alcohol (used in lyotropic mixtures that present biaxial and uniaxial nematic phases) is substituted by a detergent. This new mixture is composed by potassium laurate, ammonium decylchloride and water and presents uniaxial and biaxial nematic phases. A surface of the phase diagram os this mixture is presented and some microscopical parameters are determined. In this investigation the techniques of polarised optical microscopy, conoscopy and X ray- diffraction are used. The chemical stability of this mixture is compared to the mixture with alcohol. The anchoring properties of lyotropic liquid crystals on glass surfaces (smooth and with grooves) are also investigated, using optical polarising microscopy. A new phenomen is observed, the gliding of the director at the boundary surfaces. A qualitative model is proposed, based on the existence of an anphiphilic bilayer with defects, at the interface. The orientation and relaxation times are determined and compared to the ones predicted by the model. It is also presented, a method for treating glass surfaces with ferrofluid that is applied to orient lyotropic liquid crystal samples.

Apresentamos um novo cristal liquido liotrópico, onde o álcool (utilizado nas misturas liotrópicas com fases nemáticas biaxial e uniaxiais), é substituído por um detergente. Essa nova mistura é composta por laurato de potássio, cloreto de decilamônia e água e apresenta fases nemáticas uniaxiais, calamitica e discótica, e biaxial. É apresentada uma superfície do diagrama de fases dessa mistura e são determinados alguns parâmetros microscópicos. Nesse estudo são utilizadas as técnicas de microscopia óptica de luz polarizada, conoscopia e difração de raios x. É feito um estudo comparativo da estabilidade química desse sistema, em relação à mistura com álcool. É feito um estudo sistemático das propriedades de ancoramento de cristais líquidos liotrópicos em superfícies de vidro (lisas e com ranhuras), utilizando a técnica de microscopia óptica de luz polarizada. Um novo fenômeno é observado, o deslizamento do diretor na superfície de contorno. Um modelo qualitativo, é proposto, baseado na existência de urna bicamada anfifílica, com defeitos, na interface. São determinados os tempo de orientação e tempo de relaxação para as amostras e os resultados são comparados às previsões do modelo proposto. Também é apresentado um método de tratamento de superfícies de vidro para orientação de cristais líquidos liotrópicos. / We present a new lyotropic liquid crystal, where the alcohol (used in lyotropic mixtures that present biaxial and uniaxial nematic phases) is substituted by a detergent. This new mixture is composed by potassium laurate, ammonium decylchloride and water and presents uniaxial and biaxial nematic phases. A surface of the phase diagram os this mixture is presented and some microscopical parameters are determined. In this investigation the techniques of polarised optical microscopy, conoscopy and X ray- diffraction are used. The chemical stability of this mixture is compared to the mixture with alcohol. The anchoring properties of lyotropic liquid crystals on glass surfaces (smooth and with grooves) are also investigated, using optical polarising microscopy. A new phenomen is observed, the gliding of the director at the boundary surfaces. A qualitative model is proposed, based on the existence of an anphiphilic bilayer with defects, at the interface. The orientation and relaxation times are determined and compared to the ones predicted by the model. It is also presented, a method for treating glass surfaces with ferrofluid that is applied to orient lyotropic liquid crystal samples.

Interfaces have long been explored in Human-Computer Interaction and Interaction Design as the human-machine shared boundaries to exchange information. In the last years, we have seen increased interest in innovative materials that respond to their environment to design new types of interfaces. This study focuses on unconventional interfaces and aims to contribute to the interaction design practice by exploring the aesthetics qualities of interaction that ferrofluid can offer to the area. To fulfil this aim, a material exploration with ferrofluids is conducted guided by the four concepts of pliability, rhythm, dramaturgical structure, and fluency to discover the expressive potential of ferrofluid as a design material. The design processes are expected to conclude with a ferrofluid interface prototype according to the definition proposed by the research.

Oscillating heat pipes (OHPs) have been actively investigated since their inception due to their ability to manage high heat/heat fluxes. The OHP is a passive, wickless, two-phase heat transfer device that relies on pressure driven fluid oscillations within a hermetically-sealed serpentine channel structure. The cyclic phase-change heat transfer drives additional sensible heat transfer, and this combination causes OHPs to have high effective thermal conductivities. Many strides have been made, through both experimentation and modeling, to refine the design and implementation of OHPs. However, the main objective in OHP research has been to better understand the thermodynamic and fluid mechanic phenomena so as to enhance OHPs' thermal performance. The current work presents methods for using OHP in thermal-to-electric energy harvesting, which would allow for ‘dual-purpose’ OHP applications in which thermal management can be combined with work output. Energy harvesting occurred when a portion of the thermally-driven fluidic motion was used to generate a voltage either by electromagnetic induction or by a piezoelectric transducer imbedded in an OHP tube. For the induction approach, two methods were used to create the time-varying magnetic field required for induction. In the first, a ferrofluid was used as the OHP working fluid. Because the magnetic dipoles of the nanoparticles are randomly aligned naturally, two static, external ‘bias’ magnets were required to create a uniform magnetic field to align the particle dipoles for a non-zero magnetic flux change through a coaxial solenoid. The second method used a small rare-earth magnet confined inside a set length of an OHP channel that had a coaxial solenoid. As the OHP working fluid moved inside the harvesting channel, a portion of the fluid's momentum was transferred to the magnet, causing it to oscillate. For the piezoelectric approach, a narrow piezoelectric transducer was placed in a bow-shaped configuration along the inside of an OHP channel. Passing fluid would deflect the piezo creating a potential difference across its leads, which protruded out of the channel walls. All three of these methods successfully produced a voltage while retaining the excellent thermal performance synonymous with OHPs.

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