Correlations and forces in sheared fluids with or without quenching

Abstract

Spatial correlations play an important role in characterizing material properties related to non-local effects. Inter alia, they can give rise to fluctuation-induced forces. Equilibrium correlations in fluids provide an extensively studied paradigmatic case, in which their range is typically bounded by the correlation length. Out of equilibrium, conservation laws have been found to extend correlations beyond this length, leading, instead, to algebraic decays. In this context, here we present a systematic study of the correlations and forces in fluids driven out of equilibrium simultaneously by quenching and shearing, both for non-conserved as well as for conserved Langevin-type dynamics. We identify which aspects of the correlations are due to shear, due to quenching, and due to simultaneously applying both, and how these properties depend on the correlation length of the system and its compressibility. Both shearing and quenching lead to long-ranged correlations, which, however, differ in their nature as well as in their prefactors, and which are mixed up by applying both perturbations. These correlations are employed to compute non-equilibrium fluctuation-induced forces in the presence of shear, with or without quenching, thereby generalizing the framework set out by Dean and Gopinathan. These forces can be stronger or weaker compared to their counterparts in unsheared systems. In general, they do not point along the axis connecting the centers of the small inclusions considered to be embedded in the fluctuating medium. Since quenches or shearing appear to be realizable in a variety of systems with conserved particle number, including active matter, we expect these findings to be relevant for experimental investigations.instance, to uniaxial magnetic systems, model B describes binary alloys, spinodal dynamics of binary liquid mixtures, as well as single-component fluids [32,33]. These models have been applied extensively in describing various dynamical situations, e.g. the approach of the critical point from non-equilibrium initial conditions [34][35][36][37], the coarsening following a temperature quench [38,39], or for driven systems at criticality [40,41]. They have also been used to study shearing of near-critical fluids [42][43][44][45][46][47][48], leading to a large variety of phenomena.The use of such models provides generic scenarios, which we expect to be relevant for physical systems which allow for shearing and/or quenching. Shear is directly experimentally accessible [49]. Quenches can also be realized, for instance by using effective interactions of particles which can be changed suddenly, e.g. by swelling particles [50] or through external fields [51]. Another type of quench concerns a sudden change of temperature, which is a perturbation often employed in order to obtain supercooled liquids [52]. Such quenches of temperature (or of noise strength) may be achieved experimentally also in active fluids [53][54][55], which in many respects can be described by the use of effective temperatures [27,56...

Dynamics and steady states of a tracer particle in a confined critical fluid

“…V A 3), which could be utilized to address many-body critical Casimir interactions [59,[82][83][84][85][86]. Furthermore, while we assumed the OP to remain in equilibrium at all times, non-equilibrium scenarios such as OP quenches [31,46,87,88] appear to be a rewarding topic. It is also pertinent to extend the present work towards two and three spatial dimensions, which are the relevant cases for membranes [26-28, 89, 90], interfaces [91][92][93], and colloidal suspensions [5].…”

“…By contrast, in the far-distance limit, where the ratio between the particle radius and the distance is small, the CCF can be obtained from a "smallsphere expansion" of the Boltzmann weight [10,[13][14][15]. Recently, the non-equilibrium dynamics of colloidal particles in critical media has received increased attention [16], examples including studies of drag forces [16][17][18][19][20][21], aggregation [16,22], diffusion [23][24][25][26][27][28][29], shear flow [30,31], solvent coarsening [32][33][34], and interplay between criticality and activity [35,36].…”

Valorization of Lignocellulosic and Microalgae Biomass

“…The OCS attracts minimal capital, operating cost, and lesser energy for culture mixing. However, OCS require large land-mass for scale-up operations as they are prone to contamination and adverse weather conditions wherein they suffer evaporation and temperature fluctuations [47]. The CCS on the other hand, are operated at highly controlled conditions and are more efficient in terms of quality.…”

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