Mixing by stirring: Optimizing shapes and strategies

Eggl, Maximilian F.; Schmid, Peter J.

doi:10.1103/physrevfluids.7.073904

Cited by 9 publications

(4 citation statements)

References 38 publications

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“…Minimization of the mixnorm was further explored in the work of Eggl and Schmid [51,52], who proposed the use of a gradient-based nonlinear optimization scheme to improve the mixing efficiency of binary fluids by moving stirrers. Two cylindrical stirrers moving on concentric circular paths were used with an iterative direct-adjoint algorithm to enhance mixing.…”

Section: Literature Reviewmentioning

confidence: 99%

“…In the work of Eggl and Schmid [51], the stirrers' shapes were held constant and not subjected to optimization for enhanced mixing. To address this additional optimization parameter, the work of Eggl and Schmid [52] investigated the optimal cross-sectional shape of the stirrers in addition to the mixing strategy to further enhance scalar mixing. The authors studied four cases in their study: (i) a base configuration that was used to compare all subsequent optimizations, (ii) optimization of the cross-sectional shape of the stirrers, (iii) optimization of the velocities of the stirrers, and (iv) combined optimization of the cross-sectional shape and velocities of the stirrers.…”

Section: Literature Reviewmentioning

confidence: 99%

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Dependence of scalar mixing on initial conditions in turbulent channel flow

Singh,

Germaine,

Mydlarski

et al. 2023

Phys. Rev. Fluids

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Turbulent scalar mixing occurs within a wide variety of natural and engineering flows. Predicting and controlling the scalar concentration(s) within these flows can yield immediate benefits to numerous applications across many fields. To that end, a better understanding of the effects of scalar-field initial conditions on the evolution(s) of scalar fields is required to either promote or delay the rate at which mixing occurs. Direct numerical simulations are employed herein to simulate the evolution in time of the hydrodynamic and (passive) scalar fields within a fully developed turbulent channel flow. The effects of the scalar field initial conditions are studied by analyzing the evolution of the scalar field subject to three different initial conditions with interfaces oriented normal to the streamwise, wall-normal, and transverse directions. Particular emphasis is placed on the scalar variance and dissipation rate budgets, including the evolutions of their constituent terms. The fastest mixing occurs for the initial condition in which the interface is aligned normal to the mean velocity vector. The rapid mixing in this case is associated with higher rates of production and destruction of the scalar dissipation, as well as strong advection and stretching of the interface by the mean flow. In addition to better mixing arising from the stronger turbulence near the wall, enhanced mixing is correlated with having the edge of an interface along a channel wall, such that a large distortion of the initial interface arises from the combined effects of the no-slip condition at the channel walls with the advection of the interface by the mean flow in the region between the walls. To maximize this effect, it is recommended that scalar interfaces be aligned normal to the mean velocity vector to promote mixing within internal flows.

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Section: Literature Reviewmentioning

confidence: 99%

Section: Literature Reviewmentioning

confidence: 99%

Dependence of scalar mixing on initial conditions in turbulent channel flow

Singh,

Germaine,

Mydlarski

et al. 2023

Phys. Rev. Fluids

View full text Add to dashboard Cite

show abstract

“…Similarly, Kumar et al [ 58 ] engineered a self-sustained chaotic actuator based on LCE films doped with azobenzene and showcased the optically responsive behavior that drives the film motion under continuous illumination. Further research on self-sustained chaotic motion is essential as it contributes to the development of various fields, such as heart beating simulation and bionics [ 59 ], heart and brain chaos analysis [ 60 , 61 ], cardiovascular disease prevention [ 62 ], encrypted images [ 63 ], autonomous separation and stirrer [ 64 , 65 ], etc.…”

Section: Introductionmentioning

confidence: 99%

Self-Sustained Chaotic Jumping of Liquid Crystal Elastomer Balloon under Steady Illumination

Sun,

Dai,

et al. 2023

Polymers

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Self-sustained chaotic jumping systems composed of active materials are characterized by their ability to maintain motion through drawing energy from the steady external environment, holding significant promise in actuators, medical devices, biomimetic robots, and other fields. In this paper, an innovative light-powered self-sustained chaotic jumping system is proposed, which comprises a liquid crystal elastomer (LCE) balloon and an elastic substrate. The corresponding theoretical model is developed by combining the dynamic constitutive model of an LCE with Hertz contact theory. Under steady illumination, the stationary LCE balloon experiences contraction and expansion, and through the work of contact expansion between LCE balloon and elastic substrate, it ultimately jumps up from the elastic substrate, achieving self-sustained jumping. Numerical calculations reveal that the LCE balloon exhibits periodic jumping and chaotic jumping under steady illumination. Moreover, we reveal the mechanism underlying self-sustained periodic jumping of the balloon in which the damping dissipation is compensated through balloon contact with the elastic substrate, as well as the mechanism involved behind self-sustained chaotic jumping. Furthermore, we provide insights into the effects of system parameters on the self-sustained jumping behaviors. The emphasis in this study is on the self-sustained chaotic jumping system, and the variation of the balloon jumping modes with parameters is illustrated through bifurcation diagrams. This work deepens the understanding of chaotic motion, contributes to the research of motion behavior control of smart materials, and provides ideas for the bionic design of chaotic vibrators and chaotic jumping robots.

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“…While Schmid and Eggl recognize that most industries wouldn't implement such irregular stirrer shapes or stirring methods, they hope that their findings might shift how people think Video 4: When the velocity jiggles, stirrers with rounded edges work better for mixing two fluids. Credit: M. F. Eggl and P. J. Schmid [1] about the mixing of fluids.…”

mentioning

confidence: 99%