167 research outputs found

    Lift and thrust generation by a butterfly-like flapping wing-body model: immersed boundary-lattice Boltzmann simulations

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    The flapping flight of tiny insects such as flies or larger insects such as butterflies is of fundamental interest not only in biology itself but also in its practical use for the development of micro air vehicles (MAVs). It is known that a butterfly flaps downward for generating the lift force and backward for generating the thrust force. In this study, we consider a simple butterfly-like flapping wing body model in which the body is a thin rod and the rectangular rigid wings flap in a simple motion. We investigate lift and thrust generation of the model by using the immersed boundary lattice Boltzmann method. First, we compute the lift and thrust forces when the body of the model is fixed for Reynolds numbers in the range of 50-1000. In addition, we estimate the supportable mass for each Reynolds number from the computed lift force. Second, we simulate free flights when the body can only move translationally. It is found that the expected supportable mass can be supported even in the free flight except when the mass of the body relative to the mass of the fluid is too small, and the wing body model with the mass of actual insects can go upward against the gravity. Finally, we simulate free flights when the body can move translationally and rotationally. It is found that the body has a large pitch motion and consequently gets off-balance. Then, we discuss a way to control the pitching angle by flexing the body of the wing body model.ArticleJOURNAL OF FLUID MECHANICS. 767:659-695 (2015)journal articl

    A Novel Propeller Design for Micro-Swimming robot

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    The applications of a micro-swimming robot such as minimally invasive surgery, liquid pipeline robot etc. are widespread in recent years. The potential application fields are so inspiring, and it is becoming more and more achievable with the development of microbiology and Micro-Electro-Mechanical Systems (MEMS). The aim of this study is to improve the performance of micro-swimming robot through redesign the structure. To achieve the aim, this study reviewed all of the modelling methods of low Reynolds number flow including Resistive-force Theory (RFT), Slender Body Theory (SBT), and Immersed Boundary Method (IBM) etc. The swimming model with these methods has been analysed. Various aspects e.g. hydrodynamic interaction, design, development, optimisation and numerical methods from the previous researches have been studied. Based on the previous design of helix propeller for micro-swimmer, this study has proposed a novel propeller design for a micro-swimming robot which can improve the velocity with simplified propulsion structure. This design has adapted the coaxial symmetric double helix to improve the performance of propulsion and to increase stability. The central lines of two helical tails overlap completely to form a double helix structure, and its tail radial force is balanced with the same direction and can produce a stable axial motion. The verification of this design is conducted using two case studies. The first one is a pipe inspection robot which is in mm scale and swims in high viscosity flow that satisfies the low Reynolds number flow condition. Both simulation and experiment analysis are conducted for this case study. A cross-development method is adopted for the simulation analysis and prototype development. The experiment conditions are set up based on the simulation conditions. The conclusion from the analysis of simulation results gives suggestions to improve design and fabrication for the prototype. Some five revisions of simulation and four revisions of the prototype have been completed. The second case study is the human blood vessel robot. For the limitations of fabrication technology, only simulation is conducted, and the result is compared with previous researches. The results show that the proposed propeller design can improve velocity performance significantly. The main outcomes of this study are the design of a micro-swimming robot with higher velocity performance and the validation from both simulation and experiment

    Fluid structure interaction in bioinspired locomotion problems

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    Mención Internacional en el título de doctorNature offers a vast amount of examples of efficient locomotion. Millions of years of evolution have allowed animals —such as fish, insects and birds—, and even plants —such as winged-seeds or dandelions— to achieve outstanding locomotive skills. Therefore, it is not a surprise that scientists and engineers have tried to replicate the flight and swimming capabilities of the former examples in order to develop efficient aerial and nautical robots. In fact, these efforts have led to the design and development of several successful bioinspired robots. However, their performance is still far below their living counterparts. One of the main reasons is that the understanding of the physics underlying biological locomotion is still limited. This is due to the complexity of the problem under consideration: the locomotion of a body through a fluid medium. This can be considered fluid structure interaction (FSI) problem where the dynamics of the specimens is the result from the hydrodynamic interaction with the surrounding fluid, which in turn is modified by the motion of the specimens. Consequently, the resulting problem is highly nonlinear and complex from a mathematical standpoint. This dissertation attempts to contribute to further understand the fluid structure interactions in bioinspired locomotion problems. To that end, direct numerical simulations of several examples of bioinspired FSI problems are performed. These examples include the auto-rotation of a winged-seed, the flow interactions between the wings of a dragonfly, and the schooling patterns that emerge between two fish. In the first part of this dissertation, the algorithm which has been developed to perform part of the aforementioned studies is presented. The proposed algorithm allows the study of the FSI of systems of connected rigid bodies —which serve as a model for the actual specimens— immersed in an incompressible fluid. It is built based on a preexisting flow solver, coupled with a robotic algorithm for the computation of the dynamic equations of the bodies. The use of robotic algorithms endows the proposed methodology with a great fiexibility, allowing to simulate a large variety of problems with different geometries and configurations. The second part of the thesis is devoted to the analysis of the aforementioned examples. In this regard, we first consider the flight of a winged-seed. This is a very interesting, yet complex, problem of fluid-dynamic interaction; in which the auto-rotative motion is the result of a subtle equilibrium between the aerodynamic forces and the inertia properties of the winged-seed. In our study, the dynamics and the flow surrounding the auto-rotating seed are characterized in a range of Reynolds numbers, Re. Specifically, we focus on the study of the leading edge vortex (LEV) that is developed on the upper surface of the seed's wing as it auto-rotates. Our findings suggest that, in the explored range Re = [80 — 240], LEV's stability is not driven by vorticity transport along the spanwise direction nor viscous effects, as reported in the literature of rotating wings. Instead, fictitious accelerations (i.e., Coriolis and centrifugal accelerations) are the most suitable candidates to stabilize the LEV over the seed's wing. In the second example, we study the effect of the three-dimensional (3D) interactions in the performance of two tandem wings, resembling those of a dragonfly. To that end, the wings undergo a two-dimensional (2D) optimum kinematics which is a combination of heaving and pitching. We first analyze the effect of wings' aspect ratio, AR, by comparing the 3D and 2D simulations. The results show that 3D vertical interactions are detrimental for the thrust production of the hindwing, but they do not significantly affect the propulsive efficiency of the tandem arrangement. Next, a more realistic flapping kinematics of the 3D is considered and compared to the previous heaving kinematics. We find a decrease in the propulsive efficiency of the flapping wings compared to their heaving counterparts, which has been linked to a non-desired shedding of vorticity on the inboard region of the wings. The last bioinspired example corresponds to the collective motion of two self-propelled three-dimensional bodies. These bodies are idealized as rectangular, flat plates with flexibility along their chordwise direction, and that self-propels thanks to a prescribed vertical motion of their leading edges. We observe that tandem configurations emerge where both plates swim at a constant mean horizontal velocity and with a mean equilibrium horizontal distance. These configurations can be classified, attending to the resulting flow interactions, into compact and regular configurations. In the former, the performance of the upstream flapper is modified due to the close interaction with the downstream flapper. However, in the regular configurations, the performance of the upstream flapper is similar to that of an isolated flapper. Conversely, the performance of the downstream flapper is affected in both configurations by the interaction with the wake of the upstream flapper. We are able to link the changes in the downstream flapper's performance to its interaction with the vertical jet induced by vortex rings of the upstream flapper's wake. Finally, we propose a model to qualitatively predict the performance of a hypothetical downstream flapper based on the flow field of and isolated flapper, showing good agreement with the actual simulations.La naturaleza ofrece una gran cantidad de ejemplos de locomoción eficiente. Millones de años de evolución han permitido a animales —tales como peces, insectos o pájaros— e incluso plantas —como sainaras o dientes de león— lograr unas habilidades de lomoción excepcionales. Por lo tanto, no es una sorpresa que científicos e ingenieros hayan intentado replicar la capacidades de vuelo y nado de los anteriores ejemplos, con el objetivo de desarrollar robots aéreos y nadadores más eficientes. De hecho, estos esfuerzos han dado lugar al diseño y desarrollo exitoso de varios robots bioinsipirados. Sin embargo, el rendimiento de éstos es todavía muy inferior al de sus referentes biológicos. Una de las principales razones es que la comprensión de la física subyacente de la lomococión de sistemas biológicos es aún limitada. Esto es debido a la complejidad del problema, a saber, el movimiento de un cuerpo a través de un medio fluido. Este se puede considerar como un problema de interacción fluido estructura (FSI) donde la dinámica del espécimen es el resultado de la interacción fluidodinámica con el fluido de alrededor, el cual es a su vez modificado por el movimiento del cuerpo. Consecuentemente, el problema resultante es altamente no lineal y complejo desde un punto de vista matemático. Con esta disertación se pretende contribuir a una mayor comprensión de la interacción fluido estructura en problemas de locomoción bioninspirados. Con tal propósito, se han realizado simulaciones numéricas directas de varios ejemplos bioinspirados de interacción fluido estructura. Estos ejemplos incluyen la autorrotación de una sámara, las interaccionés fluidas entre las alas de una libélula y los patrones de nado que surgen entre dos peces. Durante la primera parte de esta disertación, se describe el algoritmo que ha sido desarrollado con el propósito de simular alguno de los problemas anteriormente citados. El algoritmo propuesto permite el estudio de la interacción fluido estructura de sistemas de cuerpos rígidos conectados —los cuales sirven como modelo de los especímenes reales— que están sumergidos en un fluido incompresible. Está construido sobre un solver fluido pre-existente, acoplado a un algoritmo robótico que se encarga de calcular las ecuaciones dinámicas de los cuerpos. El uso de algoritmos robóticos proporciona a la metodología propuesta una gran flexibilidad, permitiendo simular una gran variedad de problemas con diversas geometrías y configuraciones. La segunda parte de esta tesis está dedicada al análisis de los ejemplos mencionados anteriormente. En este respecto, consideramos primero el vuelo de una sámara, el cual es un problema muy interesante, aunque complejo, de interacción fluido dinámica en el cual el movimiento autorrotativo es el resultado de un sutil equilibrio entre las fuerzas aerodinámicas y las propiedades inerciales de la semilla. En nuestro estudio, caracterizamos la dinámica y el flujo alrededor de la semilla autorrotante en un rango de números de Reynolds, Re. En concreto, nos centramos en el estudio del vórtice del borde de ataque (LEV) que se forma en la parte superior del ala de la sámara cuando ésta autorrota. Nuestros hallazgos sugieren que, en el rango explorado de Re = [80 — 240], la estabilidad del LEV no se debe a un transporte de vorticidad a lo largo de la dirección de la envergadura del ala, ni a efectos viscosos —como se ha mencionado en la literatura de alas rotativas—, sino que las aceleraciones ficticias (es decir, las aceleraciones centrífugas y de Coriolis), son las candidatas más probables responsables de la estabilización del LEV. En el segundo ejemplo, se estudia el efecto de las interacciones tridimensionales (3D) en el rendimiento de dos alas en configuración tándem, basadas en las de una libélula. Para ello, se prescribe que el movimiento de las alas sea una combinación de cabeceo y oscilación vertical que es óptimo en 2 dimensiones (2D). Primero analizamos el efecto de la relación de aspecto de las alas, A% comparando los resultados de las simulaciones en 3D y en 2D. Los resultados revelan que las interacciones vorticales en 3D son perjudiciales para la generación de empuje del ala trasera, pero estas interacciones no afectan de forma significativa a la eficiencia propulsiva del conjunto. Posteriormente, se considera un movimiento de batimiento más realista de las alas, y se compara su eficiencia con la obtenida previamente para las alas en movimiento oscilatorio vertical. Se observa una menor eficiencia de las alas en batimiento en comparación con las mismas alas en movimiento oscilatorio vertical. Este deterioro es asociado a un desprendimiento de estructuras vorticales cerca de los bordes marginales de las alas en batimiento. El último ejemplo bioinspirado es el del movimiento colectivo de dos cuerpos tridimiensionales que se auto propulsan. Estos cuerpos se idealizan como placas planas rectangulares, siendo flexibles a lo largo de su cuerda, y que se auto propulsan gracias a un movimiento vertical impuesto de sus bordes de ataque. Los resultados muestran la aparición de configuraciones tándem donde sendas placas nadan con una velocidad inedia constante y separadas a una distancia de equilibrio que es también constante. Estas configuraciones son clasificadas —atendiendo a las interacciones fluidas— entre compactas y regulares. En las primeras, el rendimiento de la placa que nada aguas arriba (a la que llamaremos líder) se ve afectado por las interacciones cercanas con el cuerpo que nada aguas abajo (al que denominaremos seguidor). En cambio, en las configuraciones regulares el redimiento del líder es el mismo que el de una placa similar nadando de forma aislada. Por el contrario, el rendimiento del seguidor se ve afectado en ambas configuraciones debido a las interacciones con la estela del líder. Se ha podido relacionar estos cambios en la eficiencia del seguidor con la interacción con el chorro inducido por los anillos vorticales de la estela del líder. Finalmente, hemos propuesto un modelo que permite predecir, de forma cualitativa, el rendimiento de un seguidor hipotético basándonos en el campo fluido de una placa aislada. El modelo muestra una buena correlación con los datos obtenidos de las simulaciones numéricas.This thesis has been carried out in the Bioengineering and Aerospace Engineering Department at Universidad Carlos III de Madrid. The financial support has been provided by the Spanish Ministry of Economy and Competitiveness through grant DPI2016-76151-C2-2-R (AEI/FEDER, UE).Programa de Doctorado en Mecánica de Fluidos por la Universidad Carlos III de Madrid; la Universidad de Jaén; la Universidad de Zaragoza; la Universidad Nacional de Educación a Distancia; la Universidad Politécnica de Madrid y la Universidad Rovira i VirgiliPresidente: Francisco Javier Huera-Huarte.- Secretario: Javier Rodríguez Rodríguez.- Vocal: Ignazio María Viol

    A numerical study of fin and jet propulsions involving fluid-structure interactions

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    Fish swimming is elegant and efficient, which inspires humans to learn from them to design high-performance artificial underwater vehicles. Research on aquatic locomotion has made extensive progress towards a better understanding of how aquatic animals control their flexible body and fin for propulsion. Although the structural flexibility and deformation of the body and fin are believed to be important features to achieve optimal swimming performance, studies on high-fidelity deformable body and fin with complex material behavior, such as non-uniform stiffness distributions, are rare. In this thesis, a fully coupled three-dimensional high-fidelity fluid-structure interaction (FSI) solver is developed to investigate the flow field evolution and propulsion performance of caudal fin and jet propulsion involving body and/or fin deformation. Within this FSI solver, the fluid is resolved by solving unsteady and viscous Navier-Stokes equations based on the finite volume method with a multi-block grid system. The solid dynamics are solved by a nonlinear finite element method. The coupling between the two solvers is achieved in a partitioned approach in which convergence check and sub-iteration are implemented to ensure numerical stability and accuracy. Validations are conducted by comparing the simulation results of classical benchmarks with previous data in the literature, and good agreements between them are obtained. The developed FSI solver is then applied to study the bio-inspired fin and jet propulsion involving body deformation. Specifically, the effect of non-uniform stiffness distributions of fish body and/or fin, key features of fish swimming which have been excluded in most previous studies, on the propulsive performance is first investigated. Simulation results of a sunfish-like caudal fin model and a tuna-inspired swimmer model both show that larger thrust and propulsion efficiency can be achieved by a non-uniform stiffness distribution (e.g., increased by 11.2% and 9.9%, respectively, for the sunfish-like model) compared with a uniform stiffness profile. Despite the improved propulsive e performance, a bionic variable fish body stiffness does not yield fish-like midline kinematics observed in real fish, suggesting that fish movement involves significant active control that cannot be replicated purely by passive deformations. Subsequent studies focus on the jet propulsion inspired by squid locomotion using the developed numerical solver. Simulation results of a two-dimensional inflation-deflation jet propulsion system, whose inflation is actuated by an added external force that mimics the muscle constriction of the mantle and deflation is caused by the release of elastic energy of the structure, suggest larger mean thrust production and higher efficiency in high Reynolds number scenarios compared with the cases in laminar flow. A unique symmetry-breaking instability in turbulent flow is found to stem from irregular internal body vortices, which cause symmetry breaking in the wake. Besides, a three-dimensional squid-like jet propulsion system in the presence of background flow is studied by prescribing the body deformation and jet velocity profiles. The effect of the background flow on the leading vortex ring formation and jet propulsion is investigated, and the thrust sources of the overall pulsed jet are revealed as well. Finally, FSI analysis on motion control of a self-propelled flexible swimmer in front of a cylinder utilizing proportional-derivative (PD) control is conducted. The amplitude of the actuation force, which is applied to the swimmer to bend it to produce thrust, is dynamically tuned by a feedback PD controller to instruct the swimmer to swim the desired distance from an initial position to a target location and then hold the station there. Despite the same swimming distance, a swimmer whose departure location is closer to the cylinder requires less energy consumption to reach the target and hold the position there.Fish swimming is elegant and efficient, which inspires humans to learn from them to design high-performance artificial underwater vehicles. Research on aquatic locomotion has made extensive progress towards a better understanding of how aquatic animals control their flexible body and fin for propulsion. Although the structural flexibility and deformation of the body and fin are believed to be important features to achieve optimal swimming performance, studies on high-fidelity deformable body and fin with complex material behavior, such as non-uniform stiffness distributions, are rare. In this thesis, a fully coupled three-dimensional high-fidelity fluid-structure interaction (FSI) solver is developed to investigate the flow field evolution and propulsion performance of caudal fin and jet propulsion involving body and/or fin deformation. Within this FSI solver, the fluid is resolved by solving unsteady and viscous Navier-Stokes equations based on the finite volume method with a multi-block grid system. The solid dynamics are solved by a nonlinear finite element method. The coupling between the two solvers is achieved in a partitioned approach in which convergence check and sub-iteration are implemented to ensure numerical stability and accuracy. Validations are conducted by comparing the simulation results of classical benchmarks with previous data in the literature, and good agreements between them are obtained. The developed FSI solver is then applied to study the bio-inspired fin and jet propulsion involving body deformation. Specifically, the effect of non-uniform stiffness distributions of fish body and/or fin, key features of fish swimming which have been excluded in most previous studies, on the propulsive performance is first investigated. Simulation results of a sunfish-like caudal fin model and a tuna-inspired swimmer model both show that larger thrust and propulsion efficiency can be achieved by a non-uniform stiffness distribution (e.g., increased by 11.2% and 9.9%, respectively, for the sunfish-like model) compared with a uniform stiffness profile. Despite the improved propulsive e performance, a bionic variable fish body stiffness does not yield fish-like midline kinematics observed in real fish, suggesting that fish movement involves significant active control that cannot be replicated purely by passive deformations. Subsequent studies focus on the jet propulsion inspired by squid locomotion using the developed numerical solver. Simulation results of a two-dimensional inflation-deflation jet propulsion system, whose inflation is actuated by an added external force that mimics the muscle constriction of the mantle and deflation is caused by the release of elastic energy of the structure, suggest larger mean thrust production and higher efficiency in high Reynolds number scenarios compared with the cases in laminar flow. A unique symmetry-breaking instability in turbulent flow is found to stem from irregular internal body vortices, which cause symmetry breaking in the wake. Besides, a three-dimensional squid-like jet propulsion system in the presence of background flow is studied by prescribing the body deformation and jet velocity profiles. The effect of the background flow on the leading vortex ring formation and jet propulsion is investigated, and the thrust sources of the overall pulsed jet are revealed as well. Finally, FSI analysis on motion control of a self-propelled flexible swimmer in front of a cylinder utilizing proportional-derivative (PD) control is conducted. The amplitude of the actuation force, which is applied to the swimmer to bend it to produce thrust, is dynamically tuned by a feedback PD controller to instruct the swimmer to swim the desired distance from an initial position to a target location and then hold the station there. Despite the same swimming distance, a swimmer whose departure location is closer to the cylinder requires less energy consumption to reach the target and hold the position there

    Nature-inspired soft robotics: On articial cilia and magnetic locomotion

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    Inspired by micro-organisms in nature, people imagined using micro-scale soft robots to work inside the human body for therapeutic drug delivery, minimally invasive surgery, or diagnostic biochemical sensing. To create these robots is challenging due to their small size, viscosity environment, and soft constituting materials. In addition, the mechanisms of operation are quite different from the conventional rigid macro-scale robots that we are familiar with. In this PhD project, we focused on the computational analysis and design of micro-scale soft robots. Working closely with experimental groups, we studied artificial cilia and micro-swimmers that can realize particle manipulation, fluid transport, fluid mixing, or magnetic locomotion. Various cilia systems are considered, including soft inflatable cilia which could be controlled individually and programmable magnetic cilia featuring phase shifts and collective metachronal patterns. We also analyze micro-swimmers that are soft and adaptive in confined spaces. Driven by different external magnetic fields, the swimmer's motion can be changed between undulation crawling, undulation swimming, and helical crawling. By using computational modeling, we analyze the transport mechanisms of the soft robots and study the effect of different parameters to provide guidelines for the design of the robots in specific applications. By studying the physical mechanisms of micro-organisms in nature, we are not only able to understand more clearly their functional behaviour, it also opens the possibility of biomimetic design of soft robotic cilia and micro-swimmers

    Computational Fluid Dynamics Simulations of Oscillating Wings and Comparison to Lifting-Line Theory

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    Computational fluid dynamics (CFD) analysis was performed in order to compare the solutions of oscillating wings with Prandtl’s lifting-line theory. Quasi-steady and steady-periodic simulations were completed using the CFD software Star-CCM+. The simulations were performed for a number of frequencies in a pure plunging setup. Additional simulations were then completed using a setup of combined pitching and plunging at multiple frequencies. Results from the CFD simulations were compared to the quasi-steady lifting-line solution in the form of the axial-force, normal-force, power, and thrust coefficients, as well as the efficiency obtained for each simulation. The mean values were evaluated for each simulation and compared to the quasi-steady lifting-line solution. It was found that as the frequency of oscillation increased, the quasi-steady lifting-line solution was decreasingly accurate in predicting solutions

    Proceedings of the International Micro Air Vehicles Conference and Flight Competition 2017 (IMAV 2017)

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    The IMAV 2017 conference has been held at ISAE-SUPAERO, Toulouse, France from Sept. 18 to Sept. 21, 2017. More than 250 participants coming from 30 different countries worldwide have presented their latest research activities in the field of drones. 38 papers have been presented during the conference including various topics such as Aerodynamics, Aeroacoustics, Propulsion, Autopilots, Sensors, Communication systems, Mission planning techniques, Artificial Intelligence, Human-machine cooperation as applied to drones

    Chiral active fluids: Odd viscosity, active turbulence, and directed flows of hydrodynamic microrotors

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    While the number of publications on rotating active matter has rapidly increased in recent years, studies on purely hydrodynamically interacting rotors on the microscale are still rare, especially from the perspective of particle based hydrodynamic simulations. The work presented here targets to fill this gap. By means of high-performance computer simulations, performed in a highly parallelised fashion on graphics processing units, the dynamics of ensembles of up to 70,000 rotating colloids immersed in an explicit mesoscopic solvent consisting out of up to 30 million fluid particles, are investigated. Some of the results presented in this thesis have been worked out in collaboration with experimentalists, such that the theoretical considerations developed in this thesis are supported by experiments, and vice versa. The studied system, modelled in order to resemble the essential physics of the experimentally realisable system, consists out of rotating magnetic colloidal particles, i.e., (micro-)rotors, rotating in sync to an externally applied magnetic field, where the rotors solely interact via hydrodynamic and steric interactions. Overall, the agreement between simulations and experiments is very good, proving that hydrodynamic interactions play a key role in this and related systems. While already an isolated rotating colloid is driven out of equilibrium, only collections of two or more rotors have experimentally shown to be able to convert the rotational energy input into translational dynamics in an orbital rotating fashion. The rotating colloids inject circular flows into the fluid, such that detailed balance is broken, and it is not a priori known whether equilibrium properties of colloids can be extended to isolated rotating colloids. A joint theoretical and experimental analysis of isolated, pairs, and small groups of hydrodynamically interacting rotors is given in chapter 2. While the translational dynamics of isolated rotors effectively resemble the dynamics of non-rotating colloids, the orbital rotation of pairs of rotors can be described with leading order hydrodynamics and a two-dimensional analogy of Faxén’s law is derived. In chapter 3, a homogeneously distributed ensemble of rotors (bulk) as a realisation of a chiral active fluid is studied and it is explicitly shown computationally and experimentally that it carries odd viscosity. The mutual orbital translation of rotors and an increase of the effective solvent viscosity with rotor density lead to a non-monotonous behaviour of the average translational velocity. Meanwhile, the rotor suspension bears a finite osmotic compressibility resulting from the long-ranged nature of hydrody- namic interactions such that rotational and odd stresses are transmitted through the solvent also at small and intermediate rotor densities. Consequently, density inhomogeneities predicted for chiral active fluids with odd viscosity can be found and allow for an explicit measurement of odd viscosity in simulations and experiments. At intermediate densities, the collective dynamics shows the emergence of multi-scale vortices and chaotic motion which is identified as active turbulence with a self-similar power-law decay in the energy spectrum, showing that the injected energy on the rotor scale is transported to larger scales, similar to the inverse energy cascade of clas- sical two-dimensional turbulence. While either odd viscosity or active turbulence have been reported in chiral active matter previously, the system studied here shows that the emergence of both simultaneously is possible resulting from the osmotic compressibility and hydrodynamic mediation of odd and active stresses. The collective dynamics of colloids rotating out of phase, i.e., where a constant torque instead of a constant angular velocity is applied, is shown to be qualitatively very similar. However, at smaller densities, local density inhomogeneities imply position dependent angular velocities of the rotors resulting from inter-rotor friction. While the friction of a quasi-2D layer of active colloids with the substrate is often not easily modifiable in experiments, the incorporation of substrate friction into the simulation models typically implies a considerable increase in computational effort. In chapter 4, a very efficient way of incorporating the friction with a substrate into a two-dimensional multiparticle collision dynamics solvent is introduced, allowing for an explicit investigation of the influences of substrate on active dynamics. For the rotor fluid, it is explicitly shown that the influence of the substrate friction results in a cutoff of the hydrodynamic interaction length, such that the maximum size of the formed vortices is controlled by the substrate friction, also resulting in a cutoff in the energy spectrum, because energy is taken out of the system at the respective length. These findings are in agreement with the experiments. Since active particles in confinement are known to organise in states of collective dynamics, ensembles of rotationally actuated colloids are studied in circular confinement and in the presence of periodic obstacle lattices in chapters 5 and 6, respectively. The results show that the chaotic active turbulent transport of rotors in suspension can be enhanced and guided resulting from edge flows generated at the boundaries, as has recently been reported for a related chiral active system. The consequent collective rotor dynamics can be regarded as a superposition of active turbulent and imposed flows, leading to on average stationary flows. In contrast to the bulk dynamics, the imposed flows inject additional energy into the system on the long length scales, and the same scaling behaviour of the energy spectrum as in bulk is only obtained if the energy injection scales, due to the mutual generation of rotor translational dynamics throughout the system and the edge flows, are well separated. The combination of edge flow and entropic layering at the boundaries leads to oscillating hydrodynamic stresses and consequently to an oscillating vorticity profile. In the presence of odd viscosity, this consequently leads to non-trivial steady-state density modulations at the boundary, resulting from a balance of osmotic pressure and odd stresses. Relevant for the efficient dispersion and mixing of inert particles on the mesoscale by means of active turbulent mixing powered by rotors, a study of the dynamics of a binary mixture consisting out of rotors and passive particles is presented in chapter 7. Because the rotors are not self-propelled, but the translational dynamics is induced by the surrounding rotors, the passive particles, which do not inject further energy into the system, are transported according to the same mechanism as the rotors. The collective dynamics thus resembles the pure rotor bulk dynamics at the respective density of only rotors. However, since no odd stresses act between the passive particles, only mutual rotor interactions lead to odd stresses leading to the accumulation of rotors in the regions of positive vorticity. This density increase is associated with a pressure increase, which balances the odd stresses acting on the rotors. However, the passive particles are only subject to the accumulation induced pressure increase such that these particles are transported into the areas of low rotor concentration, i.e., the regions of negative vorticity. Under conditions of sustained vortex flow, this results in segregation of both particle types. Since local symmetry breaking can convert injected rotational into translational energy, microswimmers can be constructed out of rotor materials when a suitable breaking of symmetry is kept in the vicinity of a rotor. One hypothetical realisation, i.e., a coupled rotor pair consisting out of two rotors of opposite angular velocity and of fixed distance, termed a birotor, are studied in chapter 8. The birotor pumps the fluid into one direction and consequently translates into the opposite direction, and creates a flow field reminiscent of a source doublet, or sliplet flow field. Fixed in space the birotor might be an interesting realisation of a microfluidic pump. The trans- lational dynamics of a birotor can be mapped onto the active Brownian particle model for single swimmers. However, due to the hydrodynamic interactions among the rotors, the birotor ensemble dynamics do not show the emergence of stable motility induced clustering. The reason for this is the flow created by birotor in small aggregates which effectively pushes further arriving birotors away from small aggregates, which eventually are all dispersed by thermal fluctuations
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