scholarly journals Faraday Waves in a Square Cell Network: The Effects of Varying the Cell Size

Fluids ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 192
Author(s):  
Franklin Peña-Polo ◽  
Ignacio Carvajal-Mariscal ◽  
Carlos A. Vargas ◽  
Leonardo Di G. Sigalotti
Keyword(s):  
Surface Wave ◽  
Cell Size ◽  
High Speed ◽  
Energy Content ◽  
Pearson Correlation ◽  
Faraday Waves ◽  
Cell Behaviour ◽  
Cell Network ◽  
Wave Patterns ◽  
Square Cells

We have conducted experiments of the Faraday instability in a network of square cells filled with water for driving frequencies and amplitudes in the intervals 10≤F≤22 Hz and 0.1≤A≤3 mm, respectively. The experiments were aimed at studying the effects of varying the size of the cells on the surface wave patterns. Images of the surface wave patterns were recorded with a high-speed camera. The time series of photographs composing each video was Fourier analyzed, and information about the waveforms was obtained by using a Pearson correlation analysis. For small square cells of side length l=2.5 cm, adjacent cells collaborate synchronously to form regular patterns of liquid bumps over the entire grid, while ordered matrices of oscillons are formed at higher frequencies. As the size of the cells is increased to l=5 cm, collective cell behaviour at lower frequencies is no longer observed. As the frequency is increased, a transition from three triangularly arranged oscillons within each cell to three, or even four, irregularly arranged oscillons is observed. The wave patterns, the waveforms and the energy content necessary to excite Faraday waves are seen to depend on the cell size.

scholarly journals Cavity surface wave patterns and general appearance

1970 ◽  
Vol 44 (1) ◽  
pp. 33-49 ◽  
Author(s):  
Christopher Brennen
Keyword(s):  
Boundary Layer ◽  
Surface Wave ◽  
High Speed ◽  
Cavity Surface ◽  
High Speed Photography ◽  
Instability Analysis ◽  
Instability Waves ◽  
Spatial Growth ◽  
Wave Patterns ◽  
General Appearance

Observations were made of the appearance of hydrodynamic cavities behind a series of axisymmetric headforms. Among the phenomena investigated was the transition of the interfacial or separated boundary layer on the cavity surface. The first stage of this process, namely the spatial growth of instability waves could be distinguished by means of high-speed photography. Comparison is made with a theoretical instability analysis.

scholarly journals Spectral analysis of auroral geomagnetic activity during various solar cycles between 1960 and 2014

2016 ◽  
Vol 34 (12) ◽  
pp. 1159-1164 ◽  
Author(s):  
Pieter Benjamin Kotzé
Keyword(s):  
Spectral Analysis ◽  
Geomagnetic Activity ◽  
Solar Minimum ◽  
High Speed ◽  
Solar Rotation ◽  
Pearson Correlation ◽  
Coronal Holes ◽  
Rotation Period ◽  
Period Change ◽  
Solar Cycles

Abstract. In this paper we use wavelets and Lomb–Scargle spectral analysis techniques to investigate the changing pattern of the different harmonics of the 27-day solar rotation period of the AE (auroral electrojet) index during various phases of different solar cycles between 1960 and 2014. Previous investigations have revealed that the solar minimum of cycles 23–24 exhibited strong 13.5- and 9.0-day recurrence in geomagnetic data in comparison to the usual dominant 27.0-day synodic solar rotation period. Daily mean AE indices are utilized to show how several harmonics of the 27-day recurrent period change during every solar cycle subject to a 95 % confidence rule by performing a wavelet analysis of each individual year's AE indices. Results show that particularly during the solar minimum of 23–24 during 2008 the 27-day period is no longer detectable above the 95 % confidence level. During this interval geomagnetic activity is now dominated by the second (13.5-day) and third (9.0-day) harmonics. A Pearson correlation analysis between AE and various spherical harmonic coefficients describing the solar magnetic field during each Carrington rotation period confirms that the solar dynamo has been dominated by an unusual combination of sectorial harmonic structure during 23–24, which can be responsible for the observed anomalously low solar activity. These findings clearly show that, during the unusual low-activity interval of 2008, auroral geomagnetic activity was predominantly driven by high-speed solar wind streams originating from multiple low-latitude coronal holes distributed at regular solar longitude intervals.

Measurement of acoustic surface wave patterns by laser light

1967 ◽  
Vol 3 (6) ◽  
pp. 265-265 ◽  
Author(s):  
A. Korpel ◽  
L. Laub ◽  
H. Sievering
Keyword(s):  
Surface Wave ◽  
Laser Light ◽  
Acoustic Surface Wave ◽  
Wave Patterns

scholarly journals Observation of surface wave patterns modified by sub-surface shear currents

2019 ◽  
Vol 873 ◽  
pp. 508-530 ◽  
Author(s):  
Benjamin K. Smeltzer ◽  
Eirik Æsøy ◽  
Simen Å. Ellingsen
Keyword(s):  
Surface Wave ◽  
Empirical Support ◽  
Surface Flow ◽  
Recent Theory ◽  
Transient Effects ◽  
Surface Shear ◽  
Ship Waves ◽  
Shear Current ◽  
Wave Patterns ◽  
Good Agreement

We report experimental observations of two canonical surface wave patterns – ship waves and ring waves – skewed by sub-surface shear, thus confirming effects predicted by recent theory. Observed ring waves on a still surface with sub-surface shear current are strikingly asymmetric, an effect of strongly anisotropic wave dispersion. Ship waves for motion across a sub-surface current on a still surface exhibit striking asymmetry about the ship’s line of motion, and large differences in transverse wavelength for upstream versus downstream motion are demonstrated, all of which is in good agreement with theoretical predictions. Neither of these phenomena can occur on a depth-uniform current. A quantitative comparison of measured versus predicted average phase shift for a ring wave is grossly mispredicted by no-shear theory, but in good agreement with predictions for the measured shear current. A clear difference in wave frequency within the ring wave packet is observed in the upstream versus downstream direction for all shear flows, while wave dispersive behaviour is identical to that for quiescent water for propagation normal to the shear current, as expected. Peak values of the measured two-dimensional Fourier spectrum for ship waves are shown to agree well with the predicted criterion of stationary ship waves, with the exception of some cases where results are imperfect due to the limited wavenumber resolution, transient effects and/or experimental noise. Experiments were performed on controlled shear currents created in two different ways, with a curved mesh and beneath a blocked stagnant-surface flow. Velocity profiles were measured with particle image velocimetry, and surface waves with a synthetic schlieren method. Our observations lend strong empirical support to recent predictions that wave forces on vessels and structures can be greatly affected by shear in estuarine and tidal waters.

A Dislocation Dynamics Based Constitutive Model and Experimental Validations by 3D Microscale Laser Dynamic Forming of Metallic Thin Films

2010 ◽  
Author(s):  
Huang Gao ◽  
Gary J. Cheng
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Cell Size ◽  
High Speed ◽  
Dislocation Dynamics ◽  
Dynamic Responses ◽  
Strength Increase ◽  
Strain Rate Effects ◽  
Discrete Dislocation ◽  
Thickness Variations

Microscale Laser Dynamic Forming (μLDF) shows great potential in fabricating the robust and high-aspect-ratio metallic microcomponents by the high speed plasma shockwave. Experiments revealed that strain rate and sample size play important roles in determining the final results of μLDF. To further understand the deformation behavior, we develop a constitutive model integrating size effects and ultrahigh strain rate effects to predict the ultimate plastic deformations. To derive this model, 3-D Discrete Dislocation Dynamics (DDD) simulations are first set up to investigate the dislocation evolutions and the dynamic responses during shockwave propagation. It is observed that there exist three dynamic stages during deformation process, and the initial strain hardening rate in Stage II increases with strain rate. The simulation also reveals that stain softening occurs only for the smaller cell size due to two competing mechanisms. In addition, the simulation predicts that the flow stress and yield strength increase with the strain rate and decrease with cell size. The modified mechanical threshold stress (MTS) model integrating these effects is implemented in Abaqus/Explicit and predicts the deformation depth and thickness variations in good agreement with the experimental results.

Wind Tunnel Test of Honeycomb in Improving Flow Quality

2013 ◽  
Vol 774-776 ◽  
pp. 275-278
Author(s):  
Chun Guang Li ◽  
Yang Liu ◽  
John.C.K. Cheung
Keyword(s):  
Wind Tunnel ◽  
Cell Size ◽  
Turbulence Intensity ◽  
Wind Tunnel Test ◽  
Open Loop ◽  
Incoming Flow ◽  
Flow Quality ◽  
The Mean ◽  
Square Cells ◽  
Change Tendency

The function of honeycomb with different length and width in improving flow quality were studied in the course of building a new small section open loop wind tunnel. Instantaneous velocities of turbulent flow in the tunnel were measured by cobra probe. The focus of this study was put on the effect of the honeycomb in attenuating the total turbulence intensity including the free-turbulence carried by the incoming flow and the turbulence generated by the square cells themselves. The change tendency of the mean wind velocity and the total turbulence characteristics in the decay area have been studied by varying the length to cell size ratio L/D, and ratio of distance between the square cells and the measuring position to cell size X/D.

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