Mass, momentum, and energy flux conservation for nonlinear wave-wave interaction
A fullynonlinearsolution for bi-chromatic progressivewaves inwater of finite depth in the framework of the homotopy analysis method (HAM) is derived. The bi-chromaticwave field is assumed to be obtained by thenonlinearinteraction of two monochromaticwave trains that propagate independently in the same direction before encountering. The equations for the mass, momentum, andenergy fluxes based on the accurate high-order homotopy seriessolutions are obtained using a discrete integration and a Fourier series-based fitting. The conservation equations for the mean rates of the mass, momentum, andenergy fluxes before and after th...
Source: Physics of Fluids - December 8, 2016 Category: Physics Authors: Zhen Liu, Zhiliang Lin and Longbin Tao Source Type: research
Interaction dynamics of gap flow with vortex-induced vibration in side-by-side cylinder arrangement
A numerical investigation of the vortex-induced vibration (VIV) in a side-by-side circular cylinder arrangement has been performed in a two-dimensionallaminar flow environment. One of the cylinders is elastically mounted and only vibrates in the transverse direction, while its counterpart remains stationary in a uniformflow stream. When the gap ratio is sufficiently small, the flip-flopping phenomenon of the gapflow can be an additional time-dependent interference to theflow field. This phenomenon was reported in the experimental work of Bearman and Wadcock [ “The interaction between a pair of circular cylinders normal t...
Source: Physics of Fluids - December 8, 2016 Category: Physics Authors: Bin Liu and Rajeev K. Jaiman Source Type: research
Non-isothermal extrudate swell
The non-isothermalextrudate swell of a high molecular weight high-density polyethylene (HDPE) in long capillary and slit dies is studied numerically (ANSYS POLYFLOW®) using an integral K-BKZ constitutivemodel includingcrystallization kinetics, determined experimentally. The Nakamuramodel is used forcrystallization of the HDPE, where thecrystallization rate parameter is evaluated by using the well-known Ziabickiequation. This non-isothermalextrudate swell phenomenon is simulated using the pseudo-time integral K-BKZmodel with the Wagner damping function along with the differential form of the Nakamuramodel to account for th...
Source: Physics of Fluids - December 8, 2016 Category: Physics Authors: Vinod Kumar Konaganti, Maziar Derakhshandeh, Marzieh Ebrahimi, Evan Mitsoulis and Savvas G. Hatzikiriakos Source Type: research
Chaotic sedimentation of particle pairs in a vertical channel at low Reynolds number: Multiple states and routes to chaos
Thesedimentation of a pair of rigid circular particles in a two-dimensional vertical channel containing a Newtonian fluid is investigated numerically, for terminal particleReynolds numbers (ReT) ranging from 1 to 10, and for a confinement ratio equal to 4. While it is widely admitted that sufficiently inertial pairs should sediment by performing a regular DKT oscillation (Drafting-Kissing-Tumbling), the present analysis shows in contrast that a chaotic regime can also exist for such particles, leading to a much slowersedimentation velocity. It consists of a nearly horizontal pair, corresponding to a maximum effective block...
Source: Physics of Fluids - December 7, 2016 Category: Physics Authors: Romuald Verjus, Sylvain Guillou, Alexander Ezersky and Jean-R égis Angilella Source Type: research
Characterization of the secondary flow in hexagonal ducts
In this work we report the results of DNSs and LESs of the turbulentflow through hexagonal ducts atfrictionReynolds numbers based on centerplane wall shear and duct half-heightReτ,c≃ 180, 360, and 550. The evolution of the Fanningfriction factorf withRe is in very good agreement with experimental measurements. A significant disagreement between the DNS and previousRANS simulations was found in the prediction of the in-plane velocity, and is explained through the inability of theRANSmodel to properly reproduce the secondaryflow present in the hexagon. The kinetic energy of the secondaryflow integrated over the cross-sect...
Source: Physics of Fluids - December 6, 2016 Category: Physics Authors: O. Marin, R. Vinuesa, A. V. Obabko and P. Schlatter Source Type: research
Spontaneous rotation of an ice disk while melting on a solid plate
Ice disks were released at the surface of a thermalisedaluminium plate. The fusion of theice creates alubricationfilm between theice disk and the plate. The situation is similar to the Leidenfrost effect reported for aliquiddroplet evaporating at the surface of a plate which temperature is above the boiling temperature of theliquid. An analogy is depicted between the Leidenfrost phenomenon and the rapid fusion of a solid at the contact of a hot plate. Similarly to Leidenfrostdroplet, we observe that, while theice disks weremelting, the disks were very mobile: translation and rotation. A hole was drilled in the plate and al...
Source: Physics of Fluids - December 6, 2016 Category: Physics Authors: S. Dorbolo, N. Vandewalle and B. Darbois Texier Source Type: research
Phenomenology of break-up modes in contact free externally heated nanoparticle laden fuel droplets
We study thermally induced atomization modes in contact free (acoustically levitated)nanoparticle laden fuel droplets. The initial droplet size, external heat supplied, and suspended particle concentration (wt. %) in droplets govern the stability criterion which ultimately determines the dominant mode of atomization. Pure fuel droplets exhibit two dominant modes of breakup namely primary and secondary. Primary modes are rather sporadic and normally do not involve shape oscillations. Secondary atomization however leads to severe shape deformations and catastrophic intense breakup of the droplets. The dominance of these mode...
Source: Physics of Fluids - December 6, 2016 Category: Physics Authors: Binita Pathak and Saptarshi Basu Source Type: research
Transparent, immiscible, surrogate liquids with matchable refractive indexes: Increased range of density and viscosity ratios
By replacing the “heavy” siliconeoil used in theoil phase of Saksena, Christensen, and Pearlstein [ “Surrogate immiscibleliquid pairs withrefractive indexes matchable over a wide range of density andviscosity ratios, ” Phys. Fluids27, 087103 (2015)] by one with a twentyfold higherviscosity, and replacing the “light” siliconeoil in that work by one with aviscosity fivefold lower and a density about 10% lower, we have greatly extended the range ofviscosity ratio accessible by index-matching the adjustable-compositionoil phase to an adjustable-composition 1,2-propanediol + CsBr + H2O aqueous phase and have also ex...
Source: Physics of Fluids - December 5, 2016 Category: Physics Authors: J érémy Cadillon, Rajat Saksena and Arne J. Pearlstein Source Type: research
Wave excited motion of a body floating on water confined between two semi-infinite ice sheets
The wave excited motion of a body floating on water confined between two semi-infinite ice sheets is investigated. The ice sheet is treated as an elastic thin plate and water is treated as an ideal and incompressible fluid. The linearized velocity potential theory is adopted in the frequency domain and problems are solved by the method of matched eigenfunctions expansion. The fluid domain is divided into sub-regions and in each sub-region the velocity potential is expanded into a series of eigenfunctions satisfying the governing equation and the boundary conditions on horizontal planes including the free surface and ice sh...
Source: Physics of Fluids - December 2, 2016 Category: Physics Authors: K. Ren, G. X. Wu and G. A. Thomas Source Type: research
Vortex generation and control in a microfluidic chamber with actuations
In this paper, we present a novel method forvortex generation and control in a resonator-shaped microfluidic chamber with actuations. By varying the actuation conditions, including the working transducers, frequency, and voltage, two regimes ofvortices, clockwisevortex (CWvortex) and counter-clockwisevortex (CCWvortex), are generated in the chamber. We show that the direction of thevortex can be conveniently shifted from clockwise to counterclockwise by switching the working transducers without interrupting theflow, and the intensity of thevortex can be regulated by the actuation frequency and voltage. It is proposed that ...
Source: Physics of Fluids - December 2, 2016 Category: Physics Authors: Xiaopeng Shang, Xiaoyang Huang and Chun Yang Source Type: research
Global and local skin friction diagnostics from TSP surface patterns on an underwater cylinder in crossflow
A systematical method is formulated for extracting skin-friction fields from Temperature Sensitive Paint (TSP) images in the sense of time-averaging and phase-averaging. The method is applied to an underwater cylinder in crossflow at two subcritical regimes (Re = 72 000 and 144 000). TSP maps are decomposed in a time-averaged, a phase-averaged, and a random component. The asymptotic form of the energy equation at the wall provides an Euler-Lagrange equation set that is solved numerically to gain the relative skinfriction time- and phase-averaged fields from the TSP surface temperature maps. The comparison of the time ...
Source: Physics of Fluids - December 1, 2016 Category: Physics Authors: Massimo Miozzi, Alessandro Capone, Fabio Di Felice, Christian Klein and Tianshu Liu Source Type: research
Phase diagram of crushed powders
Compression of monodispersepowder samples in quasistatic conditions is addressed in a pressure range such that particles fragmentation occurs while thesolid remains incompressible (typical pressure range of 1 –300 MPa for glasspowders). For a granular bed made of particles of given size, the existence of three stages is observed during compression and crush up. First, classical compression occurs and the pressure of the granular bed increases along a characteristic curve as the volume decreases. Then, a critical pressure is reached for which fragmentation begins. During the fragmentation process, the granular pressure st...
Source: Physics of Fluids - December 1, 2016 Category: Physics Authors: S ébastien Bodard, Olivier Jalbaud, Richard Saurel, Yves Burtschell and Emmanuel Lapebie Source Type: research
Comment on “Diffusion by a random velocity field” [Phys. Fluids 13, 22 (1970)]
This comment aims at addressing amass conservation issue in a paper published in the physics of fluids. The paper [R. H. Kraichnan, “Diffusion by a random velocity field,” Phys. Fluids13(1), 22 (1970)] introduces a novel method to generate syntheticisotropic turbulence for computational purposes. The method has been used in the literature to generate inletboundary conditions and tomodelaeroacousticnoise as well as for validation and verification purposes. However, the technique uses a continuous formulation to derive themass conservation constraint. In this comment, we argue that the continuous constraint is invalid on...
Source: Physics of Fluids - November 30, 2016 Category: Physics Authors: Tony Saad and James C. Sutherland Source Type: research
On the impact of adverse pressure gradient on the supersonic turbulent boundary layer
By employing the particle image velocimetry, the mean andturbulent characteristics of aMach 2.95turbulent boundary layer are experimentally investigated without the impact of curvature. The physical mechanism with which the streamwise adversepressure gradient affects the supersonic boundary layer is revealed. The data are compared to that of the concave boundary layer with similar streamwise distributions of wall staticpressure to clarify the separate impacts of the adversepressure gradient and the concave curvature. The logarithmic law is observed to be well preserved for both of the cases. The dip below the logarithmic l...
Source: Physics of Fluids - November 29, 2016 Category: Physics Authors: Qian-Cheng Wang, Zhen-Guo Wang and Yu-Xin Zhao Source Type: research
Internal flow in droplets within a concentrated emulsion flowing in a microchannel
Droplet microfluidics has enabled a wide variety of high-throughput biotechnical applications through the use of monodisperse micro-droplets as bioreactors. Previous fluid dynamics studies ofdroplet microfluidics have focused on singledroplets oremulsions at low volume fractions. The study of concentratedemulsions at high volume fractions is important for further increasing the throughput ofdroplet microfluidics, but the fluid dynamics of suchemulsions in confined microchannels is not well understood. This paper describes the use of microscopic particleimage velocimetry to quantify theflow inside individualdroplets within ...
Source: Physics of Fluids - November 29, 2016 Category: Physics Authors: Chia Min Leong, Ya Gai and Sindy K. Y. Tang Source Type: research
