The propagation of water waves is altered when interacting with curved surfaces. Here, we consider the problem of capillary waves interacting with a 3D meniscus. We show that when capillary waves scatter off an object surrounded by a meniscus, the resulting wavefield can be drastically altered and lensing phenomena is observed. Our results are not only an important step in surface tension dominated wave interactions, but may have implications in the biological communication of surface dwelling animals.
Scaling laws for turbulent thermomagnetic convection of a high-Pr fluid in a square cavity are obtained through direct numerical simulations and formulated via theoretical arguments informed by the numerical data. A regime consistent with an ultimate-like scaling $Nu \sim Ra_m^{1/2} and Re \sim Ra_m^{1/2} emerges after the laminar-to-turbulent transition and persists for more than an order of magnitude. Evidence is provided that this heretofore unseen behavior stems from the ability of the magnetic force to facilitate the ejection and advection of thermal plumes across the fluid bulk.
The well-known paradox of linear stability for the some bounded shear flows is not solved up to now and is bypassed on the basis of the non-linear mechanisms consideration. We prove that it is arising only due to an idealized assumption of an exact space periodicity for the small hydrodynamic perturbations. When finite non-zero viscosity is taken into account only quasi-periodic boundary conditions must be used. The conditions of linear instability to the Hagen-Poiseuille flow and to the plane Couette flow are obtained.
Equations governing the flow of a polar fluid, with pressure-dependent Newtonian viscosity, through a variable-porosity medium are developed. Averaged equations are obtained using intrinsic volume averaging. A drag function is introduced to account for the interactions of the fluid with the porous matrix. Darcy and Forchheimer generalized terms are included in the model equations for both granular and consolidated media to account for the effects of the porous microstructure.
Anagha Madhusudanan, Simon J. Illingworth, Rama Govindarajan
Streamwise elongated flow structures, or streaks, dominate wall-bounded flows. We show that the renowned lift-up mechanism, that generates streaks, is significantly altered by viscosity stratification. We additionally identify a novel pathway for streak generation: the viscosity-stratified lift-up mechanism. The competition and cooperation of the streaks generated by these mechanisms provides an explanation for trends in viscosity-stratified Poiseuille flows, and remarkably, the opposing trends in Couette flows as well. Our theoretical observations are substantiated by numerical experiments.
We develop a quantum representation for Newtonian viscous fluid flows by establishing a mapping between the Navier-Stokes equation (NSE) and the Schrödinger-Pauli equation (SPE). The proposed nonlinear SPE incorporates the two-component wave function and the imaginary diffusion. Consequently, classical fluid flow can be interpreted as a non-Hermitian quantum spin system. Using the SPE-based numerical simulation of viscous flows, we demonstrate the quantum/wave-like behavior in flow dynamics. Furthermore, the SPE equivalent to the NSE can facilitate the quantum simulation of fluid dynamics.
We combine the theory of slow spectral closure for linearized Boltzmann equations with Maxwell's kinetic boundary conditions to derive non-local hydrodynamics with arbitrary accommodation. Focusing on shear-mode dynamics, we obtain explicit steady state solutions in terms of Fourier integrals and closed-form expressions for the mean flow and the stress. We demonstrate that the exact non-local fluid model correctly predicts several rarefaction effects with accommodation, including the Couette flow and thermal creep in a plane channel.
Oscillatory instability of buoyancy convection in a laterally heated cube with perfectly thermally conducting horizontal boundaries is studied. The effect of the spanwise boundaries on the oscillatory instability onset is studied. The problem is treated by Krylov-subspace-iteration based Newton and Arnoldi methods. The Krylov basis vectors are calculated by a novel approach that involves the SIMPLE iteration and a projection onto a space of functions satisfying all linearized and homogeneous boundary conditions. The finite volume grid is gradually refined from 1003 to 2563 finite volumes. A self-sustaining oscillatory process responsible for the instability onset is revealed, visualized and explained.
Daniel Floryan, Tyler Van Buren, Alexander J. Smits
The structure of swimmers' wakes is often assumed to be an indicator of swimming performance, that is, how momentum is produced and energy is consumed. Here, we discuss three cases where this assumption fails. In general, great care should be taken in deriving any conclusions about swimming performance from the wake flow pattern.
We derive an expression for the velocity profile of a pressure-driven yield-stress Bingham fluid flowing around a 2D concentric annulus. The formula requires the numerical solution of a nonlinear equation for the positions of the yield surfaces. The results allow the prediction of the effects of channel curvature on the pressure gradient required to initiate flow for given yield stress, and for the width of the plug region and the flux through the channel at different curvatures.
This paper considers membranes of globular structure in the framework of the cell model technique. Coupled micropolar and Brinkman-type equations are used to model the flow of micropolar fluid through a spherical cell, consisting of solid core, porous layer and liquid envelope. The solution is obtained in analytical form. Boundary value problems with different conditions on hypothetical cell surface are considered and compared. The hydrodynamic permeability of a membrane is investigated as a function of micropolar and porous medium characteristics.
Studi ini bertujuan untuk membuat ekstrak air daun selasih untuk penyembuhan flu dan demam. Metode yang digunakan adalah eksperimen dan uji aktivitas katalik secara langsung. Tahapan pertama yang di lakukan adalah pembuatan ekstrak dari daun selasih. Uji aktivitas langsung dilakukan dengan variasi pemakaian setiap 15 menit sehari. Hasil eksperimen membuktikan bahwa remasan daun selasih dapat menyembuhkan flu dan hidung tersumbat. Kondisi optimum terhadap ekstrak daun selasih dapat dilihat 1 hari dengan berkali-berkali pemakaian. Penyembuhan ini di duga karena aktivitas/zat aktif yaitu asam fenolat yang memiliki aktivitas anti bakteri , anti inflamasi, anti kanker, dan anti virus.
Complete Hamiltonian formalism is suggested for inertial waves in rotating incompressible fluid. Resonance three-wave interaction processes -- decay instability and confluence of two waves -- are shown to play a key role in the weakly nonlinear dynamics and statistics of inertial waves in the rapid rotation case. Future applications of the Hamiltonian approach in inertial wave theory are investigated and discussed.
This paper makes a correction to the collision rates of small droplets in turbulent fluid derived by Saffman and Turner(1956). Not only the distortion but also the rotation of the fluid is taken into account between two close droplets. A rotation reference is fixed on one drop, and the fluxes of the other drops moving towards the fixed one are carried out based on this new reference. The behaviors of turbulent flow are analyzed within the smallest eddies under the rotation reference, and a correction is made to the collision rates by multiplying a factor sqrt(2).
We introduce and validate an algorithm to compute transient amplication factors for the Orr-Sommerfeld-Squire linear theory for parallel two-phase flow. We further introduce direct numerical simulation as a way of comparing the linear theory with early-stage wave growth in simulations. The simulation results are drawn from a strongly supercritical parameter case wherein the modal growth rates are strong. In this case, the modal growth dominates the transient growth
An ionocraft is a small instrument that generates net vertical force from electrostatic field. A model of ionization and flow is built to explain this force. The assumption of a threshold field density and the constant charge density is applied to simplify the flow model. With these assumptions, corresponding simulation results and comparison with experimental data, we have shown that this model is sufficient to explain the force on the ionocraft.