Founded in 1958, Physics of Fluids publishes leading work in traditional areas of fluid dynamics, including the dynamics of gases, liquids, complex liquids or multiphase fluids, as well as in novel and emerging areas.
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The dynamical system governing the motion of a curved rigid twodimensional circulararc fiber in simple shear is derived in analytical form. This is achieved by finding the solution for the associated lowReynoldsnumber flow around such a fiber using the methods of complex analysis. Solutions of the dynamical system display the “flipping” and “scooping” recently observed in computational studies of threedimensional fibers using linked rigid rod and beadshell models [J. Wang et al., “Flipping, scooping, and spinning: Drift of rigid curved nonchiral fibers in simple shear flows,” Phys. Fluids 24, 123304 (2012)]. To complete the Jefferytype equations for a curved fiber in a linear flow field we also derive its evolution equations in an extensional flow. It is expected that the equations derived here also govern the motion of slender, curved, threedimensional rigid fibers when they evolve purely in the plane of shear or strain.

Lockexchange gravity currents propagating up a slope are investigated by large eddy simulations, focusing on the entrainment and mixing processes occurring between the dense current and the ambient fluid. Relevant parameters, such as the aspect ratio of the initial volume of dense fluid in the lock R, the angle between the bottom boundary and the horizontal direction θ and the depth aspect ratio ϕ, are varied. The numerical results are compared with laboratory experiments and a good agreement is found. Entrainment and mixing in a lockrelease gravity current are studied using different entrainment parameters and an energy budget method. The entrainment is found to depend on both Froude, Fr, and Reynolds, Re, numbers. In addition, the dependence of both entrainment and mixing on the parameters varied is discussed. The entrainment decreases with increasing steepness of the bottom and R. Irreversible mixing is not affected by the varied parameters during the slumping phase, while during the successive phases of motion, it is found to decrease with the increase of θ and R. Low entrainment and mixing occur for ϕ < 1.

The tunnel noise in a Mach 5.9 Ludwieg tube is determined by two methods, a newly developed coneprobeDNS method and a reliable hotwirePitotprobe method. The new method combines pressure and heat flux measurements using a cone probe and direct numerical simulation (DNS). The modal analysis is based on transfer functions obtained by the DNS to link the measured quantities to the tunnel noise. The measurements are performed for several unitReynolds numbers in the range of 5 ⋅ 10^{6} ≤ Re/m ≤ 16 ⋅ 10^{6} and probe positions to identify the sensitivities of tunnel noise. The DNS solutions show similar response mechanisms of the cone probe to incident acoustic and entropywaves which leads to high condition numbers of the transfer matrix such that a unique relationship between response and source mechanism can be only determined by neglecting the contribution of the nonacoustic modes to the pressure and heat flux fluctuations. The results of the coneprobeDNS method are compared to a modal analysis based on the hotwirePitotprobe method which provides reliable results in the frequency range less than 50 kHz. In this low frequency range the findings of the two different mode analyses agree well. At higher frequencies, the newly developed coneprobeDNS method is still valid. The tunnel noise is dominated by the acoustic mode, since the entropy mode is lower by one order of magnitude and the vorticity mode can be neglected. The acoustic mode is approximately 0.5% at 30 kHz and the coneprobeDNS data illustrate the acoustic mode to decrease and to asymptotically approach 0.2%.

The objective of this investigation is to study the influence of superheat temperature and applied uniform electric field across the liquidvapor interface during film boiling using a coupled level set and volume of fluid algorithm. The hydrodynamics of bubble growth, detachment, and its morphological variation with electrohydrodynamic forces are studied considering the medium to be incompressible, viscous, and perfectly dielectric at near critical pressure. The transition in interfacial instability behavior occurs with increase in superheat, the bubble release being periodic both in space and time. Discrete bubble growth occurs at a smaller superheat whereas vapor columns form at the higher superheat values. Destabilization of interfacial motion due to applied electric field results in decrease in bubble separation distance and increase in bubble release rate culminating in enhanced heat transfer rate. A comparison of maximum bubble height owing to application of different intensities of electric field is performed at a smaller superheat. The change in dynamics of bubble growth due to increasing superheat at a high intensity of electric field is studied. The effect of increasing intensity of electric field on the heat transfer rate at different superheats is determined. The boiling characteristic is found to be influenced significantly only above a minimum critical intensity of the electric field.

In this work, we study the flow of a conducting fluid inside a twodimensional square domain. The problem is solved by using a variational multiscale finite element approach. The study focuses on a high magnetic interaction parameter range and high Reynolds number. Under the imposition of a high magnetic field, the flow gets regularized, but fast transient phenomena take place, which could lead to numerical errors. An expression to compute the maximum time step that guarantees convergence in explicit schemes is proposed and validated through numerical tests.