Visualization and Measurement of Steady Streaming Induced in Oscillating Flow

2004 ◽  
Author(s):  
Hideyuki Nakayama ◽  
Haruhiko Mori ◽  
Jun Shimizu ◽  
Takahiro Ito ◽  
Hideo Nakamura ◽  
...  
Keyword(s):  
Excitation Frequency ◽  
Oscillating Flow ◽  
Stagnation Region ◽  
Piv Measurements ◽  
Steady Streaming ◽  
Driving Mechanisms ◽  
Interface Wave ◽  
Order Of Magnitude ◽  
Zero Time ◽  
Streaming Flow

Non-zero time averaged flows can be induced in fluctuating flows. Shimizu et al. found such time-averaged streaming to occur in stratified fluids excited in a vertical, stationary cylinder at a frequency close to the natural frequency of the axisymmetric interface wave [1]. PIV measurements have revealed intermittent formation of a stagnation region close the fluid-fluid interface that enables a jet-like flow departing from the center of the interface to be sustained over cycles. The jet-like flow induces a recirculating streaming flow that extends several diameters away from the interface. Difficulty still remains in quantifying experimentally the detailed flow structure and defining the driving mechanisms, since the streaming is more than one order of magnitude smaller than the forced oscillating flow. The present paper presents PIV data that show temporal evolution of the flow in each cycle, the effect of fluid viscosities and the excitation frequency and amplitude.

Wave-Induced Streaming in Vertically-Excited, Stratified Fluids

2004 ◽  
Author(s):  
Hideyuki Nakayama ◽  
Haruhiko Mori ◽  
Jun Shimizu ◽  
Takahiro Ito ◽  
Hideo Nakamura ◽  
...  
Keyword(s):  
Excitation Frequency ◽  
Stratified Fluids ◽  
Stagnation Region ◽  
Piv Measurements ◽  
Driving Mechanisms ◽  
Interface Wave ◽  
Order Of Magnitude ◽  
Wave Induced ◽  
Zero Time ◽  
Streaming Flow

Non-zero time averaged flows can be induced in fluctuating flows. Shimizu et al. found such time-averaged streaming to occur in stratified fluids excited in a vertical, stationary cylinder at a frequency close to the natural frequency of the axisymmetric interface wave [1]. PIV measurements have revealed intermittent formation of a stagnation region close the fluid-fluid interface that enables a jet-like flow departing from the center of the interface to be sustained over cycles. The jet-like flow induces a recirculating streaming flow that extends several diameters away from the interface. Difficulty still remains in quantifying experimentally the detailed flow structure and defining the driving mechanisms, since the streaming is more than one order of magnitude smaller than the forced oscillating flow. The present paper presents PIV data that show temporal evolution of the flow in each cycle, the effect of fluid viscosities and the excitation frequency and amplitude.

Steady streaming within a periodically rotating sphere

2008 ◽  
Vol 608 ◽  
pp. 71-80 ◽  
Author(s):  
RODOLFO REPETTO ◽  
JENNIFER H. SIGGERS ◽  
ALESSANDRO STOCCHINO
Keyword(s):  
Series Expansion ◽  
Oscillation Frequency ◽  
Small Amplitude ◽  
Quantitative Agreement ◽  
Torsional Oscillations ◽  
Rotating Sphere ◽  
Good Quantitative Agreement ◽  
Steady Streaming ◽  
Theory And Experiments ◽  
Streaming Flow

We consider the flow in a spherical chamber undergoing periodic torsional oscillations about an axis through its centre, and analyse it both theoretically and experimentally. We calculate the flow in the limit of small-amplitude oscillations in the form of a series expansion in powers of the amplitude, finding that at second order, a steady streaming flow develops consisting of two toroidal cells. This streaming behaviour is also observed in our experiments. We find good quantitative agreement between theory and experiments, and we discuss the dependence of the steady streaming behaviour as both the oscillation frequency and amplitude are varied.

The flow induced by the torsional oscillations of an elliptic cylinder

1995 ◽  
Vol 290 ◽  
pp. 279-298 ◽  
Author(s):  
N. Riley ◽  
M. F. Wybrow
Keyword(s):  
Small Amplitude ◽  
Fluid Motion ◽  
Fluid Flows ◽  
Elliptic Cylinder ◽  
Minor Axis ◽  
Oscillatory Motion ◽  
Torsional Oscillations ◽  
Steady Streaming ◽  
Axis Parallel ◽  
Streaming Flow

We consider the fluid motion induced when an elliptic cylinder performs small-amplitude torsional oscillations about an axis parallel to a generator which passes through either the centre or a point on the major or minor axis of the ellipse. In common with other fluid flows dominated by oscillatory motion, a time-independent, or steady streaming flow develops. This steady streaming exhibits several unusual and unexpected features, which are confirmed by experiment.

Unsteady viscous flow in a pipe of slowly varying cross-section

1974 ◽  
Vol 64 (2) ◽  
pp. 209-226 ◽  
Author(s):  
P. Hall
Keyword(s):  
Viscous Flow ◽  
Cross Section ◽  
Pressure Difference ◽  
Pipe Wall ◽  
Oscillatory Motion ◽  
Steady Streaming ◽  
First Order ◽  
Order Of Magnitude ◽  
Unsteady Viscous Flow ◽  
Oscillatory Pressure

The steady streaming generated in a pipe of slowly varying cross-section when a purely oscillatory pressure difference is maintained between its ends is considered. It is assumed that the perturbation of the pipe wall in the r, θ plane is small compared with the characteristic thickness of the Stokes layer associated with the oscillatory motion of the fluid. The first-order steady streaming is evaluated for the cases when this characteristic thickness is large and small compared with a typical radius of the pipe. In both these limits it is found that the geometry of the pipe is crucial in determining the nature of the induced steady streaming. If the ends of the pipe have the same mean radius it is found that the steady streaming consists of regions of recirculation between the nodes of the pipe. Otherwise the steady streaming is of a larger order of magnitude and has a component which represents a net flow towards the wider end of the pipe.

scholarly journals Acoustic streaming and the induced forces between two spheres

2016 ◽  
Vol 810 ◽  
pp. 378-391 ◽  
Author(s):  
D. Fabre ◽  
J. Jalal ◽  
J. S. Leontini ◽  
R. Manasseh
Keyword(s):  
Acoustic Streaming ◽  
Lateral Force ◽  
Oscillating Flow ◽  
Low Frequencies ◽  
High Frequencies ◽  
Steady Streaming ◽  
The Mean ◽  
Linear Problems ◽  
Parameter Measuring ◽  
Dimensional Domain

The ability of acoustic microstreaming to cause a pair of particles to attract or repel is investigated. Expanding the flow around two spheres in terms of a small-amplitude parameter measuring the amplitude of the forcing, the leading order is an oscillating flow field with zero mean representing the effect of the applied acoustic field, while the second-order correction contains a steady streaming component. A modal decomposition in the azimuthal direction reduces the problem to a few linear problems in a two-dimensional domain corresponding to the meridional ($r,z$) plane. The analysis computes both the intricate flow fields and the mean forces felt by both spheres. If the spheres are aligned obliquely with respect to the oscillating flow, they experience a lateral force which realigns them into a transverse configuration. In this transverse configuration, they experience an axial force which can be either attractive or repulsive. At high frequencies the force is always attractive. At low frequencies, it is repulsive. At intermediate frequencies, the force is attractive at large distances and repulsive at small distances, leading to the existence of a stable equilibrium configuration.

Quasi-steady vortical structures in vertically vibrating soap films

1998 ◽  
Vol 372 ◽  
pp. 213-230 ◽  
Author(s):  
JOSÉ M. VEGA ◽  
F. J. HIGUERA ◽  
P. D. WEIDMAN
Keyword(s):  
Numerical Simulations ◽  
Liquid Flow ◽  
Excitation Frequency ◽  
Soap Film ◽  
Soap Films ◽  
Vortical Structures ◽  
Steady Streaming ◽  
Streaming Motion

An analysis of the quasi-steady streaming of the liquid in a vertically vibrated horizontal soap film is reported. The air around the soap film is seen to play a variety of roles: it transmits normal and tangential oscillatory stresses to the film, damps out Marangoni waves, and forces non-oscillatory deflection of the film and tangential motion of the liquid. Non-oscillatory volume forcing originating inside the liquid is also analysed. This forcing dominates the quasi-steady streaming when the excitation frequency is close to the eigenfrequency of a Marangoni mode of the soap film, while both volume forcing in the liquid and surface forcing of the gas on the liquid are important when no Marangoni mode resonates. Different manners by which the combined forcings can induce quasi-steady streaming motion are discussed and some numerical simulations of the quasi-steady liquid flow are presented.

scholarly journals Transient birefringence of liquids induced by terahertz electric-field torque on permanent molecular dipoles

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Mohsen Sajadi ◽  
Martin Wolf ◽  
Tobias Kampfrath
Keyword(s):  
Dipole Moments ◽  
Excitation Frequency ◽  
Low Frequency ◽  
Optical Excitation ◽  
Thz Spectroscopy ◽  
Optical Pulses ◽  
Reorientational Motion ◽  
Translational Mode ◽  
Order Of Magnitude ◽  
Transient Birefringence

Abstract Collective low-frequency molecular motions have large impact on chemical reactions and structural relaxation in liquids. So far, these modes have mostly been accessed indirectly by off-resonant optical pulses. Here, we provide evidence that intense terahertz (THz) pulses can resonantly excite reorientational-librational modes of aprotic and strongly polar liquids through coupling to the permanent molecular dipole moments. We observe a significantly enhanced response because the transient optical birefringence is up to an order of magnitude higher than obtained with optical excitation. Frequency-dependent measurements and a simple analytical model indicate that the enhancement arises from resonantly driven librations and their coupling to reorientational motion, assisted by the pump field and/or a cage translational mode. Our results open up the path to applications such as efficient molecular alignment, enhanced transient Kerr signals and systematic resonant nonlinear THz spectroscopy of the coupling between intermolecular modes in liquids.

Oscillating and streaming flow identification in a thermoacoustic resonator, from undersampled PIV measurements

2014 ◽  
Vol 25 (2) ◽  
pp. 025005 ◽  
Author(s):  
P Debesse ◽  
D Baltean Carlès ◽  
F Lusseyran ◽  
M-X François
Keyword(s):  
Piv Measurements ◽  
Streaming Flow

scholarly journals Recent acceleration in coastal cliff retreat rates on the south coast of Great Britain

2016 ◽  
Vol 113 (47) ◽  
pp. 13336-13341 ◽  
Author(s):  
Martin D. Hurst ◽  
Dylan H. Rood ◽  
Michael A. Ellis ◽  
Robert S. Anderson ◽  
Uwe Dornbusch
Keyword(s):  
Great Britain ◽  
South Coast ◽  
Coastal Change ◽  
The South ◽  
Coastal System ◽  
Sea Levels ◽  
Driving Mechanisms ◽  
Order Of Magnitude ◽  
Rising Sea Levels ◽  
Cliff Retreat

Rising sea levels and increased storminess are expected to accelerate the erosion of soft-cliff coastlines, threatening coastal infrastructure and livelihoods. To develop predictive models of future coastal change we need fundamentally to know how rapidly coasts have been eroding in the past, and to understand the driving mechanisms of coastal change. Direct observations of cliff retreat rarely extend beyond 150 y, during which humans have significantly modified the coastal system. Cliff retreat rates are unknown in prior centuries and millennia. In this study, we derived retreat rates of chalk cliffs on the south coast of Great Britain over millennial time scales by coupling high-precision cosmogenic radionuclide geochronology and rigorous numerical modeling. Measured 10Be concentrations on rocky coastal platforms were compared with simulations of coastal evolution using a Monte Carlo approach to determine the most likely history of cliff retreat. The 10Be concentrations are consistent with retreat rates of chalk cliffs that were relatively slow (2–6 cm⋅y−1) until a few hundred years ago. Historical observations reveal that retreat rates have subsequently accelerated by an order of magnitude (22–32 cm⋅y−1). We suggest that acceleration is the result of thinning of cliff-front beaches, exacerbated by regional storminess and anthropogenic modification of the coast.

Streaming flow induced by an oscillating cascade of circular cylinders

1993 ◽  
Vol 252 ◽  
pp. 147-171 ◽  
Author(s):  
B. Yan ◽  
D. B. Ingham ◽  
B. R. Morton
Keyword(s):  
Numerical Solutions ◽  
Stokes Equations ◽  
Circular Cylinders ◽  
Navier Stokes ◽  
Grid System ◽  
Leading Order ◽  
Rectangular Grid ◽  
Navier Stokes Equations ◽  
Steady Streaming ◽  
Streaming Flow

The fluid flow induced by a cascade of circular cylinders which oscillates harmonically in an unbounded, incompressible, viscous fluid which is otherwise at rest is investigated both numerically and experimentally. Attention in this paper is mainly concentrated on the induced steady streaming flow which occurs when the ratio of the amplitude of the oscillation of the cascade to the size of the cylinder, ε, is very small. The leading-order flow is then governed by the steady Navier-Stokes equations. In order to solve these equations numerically we first generate numerically a grid system using the boundary element method and then use a finite-difference scheme on the newly generated rectangular grid system. Numerical results show that for small values of the streaming Reynolds number Rs there are four recirculating flows of equal strength around each circular cylinder of the cascade. At large values of Rs symmetry breaks down and numerical solutions are found for asymmetrical flows. Numerically, a critical value of Rs, Rso say, is identified such that the flow is symmetrical when Rs < Rso and asymmetrical when Rs > Rso and these results are in reasonable agreement with experimental results, which are also presented in this paper.

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