A THREE‐DIMENSIONAL SEISMIC WAVE MODEL WITH BOTH ELECTRICAL AND VISUAL OBSERVATION OF WAVES

Geophysics ◽  
1954 ◽  
Vol 19 (2) ◽  
pp. 220-236 ◽  
Author(s):  
J. F. Evans ◽  
C. F. Hadley ◽  
J. D. Eisler ◽  
D. Silverman
Keyword(s):  
High Frequency ◽  
Three Dimensional ◽  
Wave Model ◽  
Short Wave ◽  
Visual Observation ◽  
Sound Waves ◽  
Transient Wave ◽  
Symmetric Wave ◽  
Theoretical Predictions ◽  
High Frequency Waves

The short wave lengths required in a seismic model to give wave‐front patterns geometrically similar to those in a large prototype (the earth) can only be obtained by using high frequency sound waves. As sources and detectors of such high frequency waves, piezoelectric crystals are used, primarily because under identical stimuli they are capable of almost perfect duplication. Such duplication is made use of in displaying on an oscilloscope stationary patterns which are characteristic of transient particle motion at a point in the model. Also, it has made possible the direct visual observation of transient wave fronts in transparent models, techniques for which are described, and sample photographs given. As an example of quantitative use of the described model techniques, the results are presented showing symmetric and anti‐symmetric wave propagation in a free elastic plate. Good agreement is found between many features of the experimental record and theoretical predictions.

The Interaction Between Steep Waves and a Vertical, Surface-Piercing Column

2005 ◽  
Vol 127 (1) ◽  
pp. 31-38 ◽  
Author(s):  
Rizwan Sheikh ◽  
Chris Swan
Keyword(s):  
High Frequency ◽  
Impact Damage ◽  
Wave Interaction ◽  
Scattered Wave ◽  
Short Wave ◽  
Vertical Surface ◽  
Wave Impact ◽  
Single Column ◽  
High Frequency Waves ◽  
Incident Waves

This paper describes new laboratory observations concerning the interaction between a series of steep incident waves and a vertical, surface-piercing, column. The motivation for the study arose as a result of wave impact damage sustained to the undersides of several concrete gravity-based structures in the northern North Sea. Earlier work, [Swan et al. Appl. Ocean. Res. 19, pp. 309–327 (1997)], demonstrated that in the case of multiple column structures, the individual diameters of which lie outside the typical (linear) diffraction regime, there exists a new and previously unexpected mechanism leading to the scattering of high-frequency waves. Although the implications of this effect was carefully documented, not least because it explained the occurrence of wave impacts in relatively moderate seas, its physical origins remained unclear. In particular, it was uncertain whether this type of scattering would be observed in the case of a single column, or whether it results from the transmission of wave modes trapped between the legs of a multiple column structure. In the case of a single column, if the diameter, D, is such that the flow lies within the drag-inertia regime, D/λ<0.2, where λ is the corresponding wavelength, linear diffraction theory suggests there will be little or no scattered wave energy. The present laboratory observations demonstrate that this is not, in fact, the case. If the incident waves are steep, a strong and apparently localized interaction is clearly observed at the water surface. This, in turn, leads to the scattering of high-frequency waves. Although these waves are relatively small in amplitude, their subsequent interaction with other steep incident waves takes the form of a classic long-wave short-wave interaction and can produce a significant increase in the maximum crest elevation relative to those recorded in the absence of the structure. The present paper will demonstrate that the scattering of these high-frequency waves, and their subsequent nonlinear interaction with other incident waves, has significant implications for the specification of an effective air-gap and hence for the setting of deck elevations.

The Interaction Between Steep Waves and a Vertical, Surface-Piercing Column

2003 ◽  
Author(s):  
Rizwan Sheikh ◽  
Chris Swan
Keyword(s):  
High Frequency ◽  
Impact Damage ◽  
Wave Interaction ◽  
Scattered Wave ◽  
Short Wave ◽  
Vertical Surface ◽  
Wave Impact ◽  
Single Column ◽  
High Frequency Waves ◽  
Incident Waves

The paper describes new laboratory observations concerning the interaction between a series of steep incident waves and a vertical, surface-piercing, column. The motivation for the study arose as a result of wave impact damage sustained to the undersides of several concrete gravity-based structures in the northern North Sea. Earlier work, Swan et al. [1], demonstrated that in the case of multiple column structures, the individual diameters of which lie outside the typical (linear) diffraction regime, there exists a new and previously unexpected mechanism leading to the scattering of high-frequency waves. Although the implications of this effect was carefully documented, not least because it explained the occurrence of wave impacts in relatively moderate seas, its physical origins remained unclear. In particular, it was uncertain whether this type of scattering would be observed in the case of a single column, or whether it results from the transmission of wave modes trapped between the legs of a multiple column structure. In the case of a single column, if the diameter, D, is such that the flow lies within the drag-inertia regime, D/λ &lt; 0.2, where λ is the corresponding wavelength, linear diffraction theory suggests there will be little or no scattered wave energy. The present laboratory observations demonstrate that this is not, in fact, the case. If the incident waves are steep, a strong and apparently localised interaction is clearly observed at the water surface. This, in turn, leads to the scattering of high-frequency waves. Although these waves are relatively small in amplitude, their subsequent interaction with other steep incident waves takes the form of a classic long-wave short-wave interaction and can produce a significant increase in the maximum crest elevation relative to those recorded in the absence of the structure. The present paper will demonstrate that the scattering of these high-frequency waves, and their subsequent nonlinear interaction with other incident waves, has significant implications for the specification of an effective air-gap and hence for the setting of deck elevations.

scholarly journals Experiments on the elliptic instability in vortex pairs with axial core flow

2011 ◽  
Vol 677 ◽  
pp. 383-416 ◽  
Author(s):  
CLÉMENT ROY ◽  
THOMAS LEWEKE ◽  
MARK C. THOMPSON ◽  
KERRY HOURIGAN
Keyword(s):  
Growth Rate ◽  
Axial Velocity ◽  
Water Channel ◽  
Three Dimensional ◽  
Axial Flow ◽  
Short Wave ◽  
Measured Velocity ◽  
Vortex Pairs ◽  
Theoretical Predictions ◽  
Good Agreement

Results are presented from an experimental study on the dynamics of pairs of vortices, in which the axial velocity within each core differs from that of the surrounding fluid. Co- and counter-rotating vortex pairs at moderate Reynolds numbers were generated in a water channel from the tips of two rectangular wings. Measurement of the three-dimensional velocity field was accomplished using stereoscopic particle image velocimetry, revealing significant axial velocity deficits in the cores. For counter-rotating pairs, the long-wavelength Crow instability, involving symmetric wavy displacements of the vortices, could be clearly observed using dye visualisation. Measurements of both the axial wavelength and the growth rate of the unstable perturbation field were found to be in good agreement with theoretical predictions based on the full experimentally measured velocity profile of the vortices, including the axial flow. The dye visualisations further revealed the existence of a short-wavelength core instability. Proper orthogonal decomposition of the time series of images from high-speed video recordings allowed a precise characterisation of the instability mode, which involves an interaction of waves with azimuthal wavenumbers m = 2 and m = 0. This combination of waves fulfils the resonance condition for the elliptic instability mechanism acting in strained vortical flows. A numerical three-dimensional stability analysis of the experimental vortex pair revealed the same unstable mode, and a comparison of the wavelength and growth rate with the values obtained experimentally from dye visualisations shows good agreement. Pairs of co-rotating vortices evolve in the form of a double helix in the water channel. For flow configurations that do not lead to merging of the two vortices over the length of the test section, the same type of short-wave perturbations were observed. As for the counter-rotating case, quantitative measurements of the wavelength and growth rate, and comparison with previous theoretical predictions, again identify the instability as due to the elliptic mechanism. Importantly, the spatial character of the short-wave instability for vortex pairs with axial flow is different from that previously found in pairs without axial flow, which exhibit an azimuthal variation with wavenumber m = 1.

scholarly journals Short-Wave Asymptotics for Gaussian Beams and Packets and Scalarization of Equations in Plasma Physics

Physics ◽  
2019 ◽  
Vol 1 (2) ◽  
pp. 301-320
Author(s):  
Anatoly Yu. Anikin ◽  
Sergey Yu. Dobrokhotov ◽  
Alexander I. Klevin ◽  
Brunello Tirozzi
Keyword(s):  
Wave Packet ◽  
High Frequency ◽  
Classical Mechanics ◽  
Short Wave ◽  
Lower Hybrid ◽  
Focal Points ◽  
Complex Germ ◽  
High Frequency Waves ◽  
Arbitrary Frequency ◽  
Main Ideas

We study Gaussian wave beam and wave packet types of solutions to the linearized cold plasma system in a toroidal domain (tokamak). Such solutions are constructed with help of Maslov’s complex germ theory (short-wave or semi-classical asymptotics with complex phases). The term “semi-classical” asymptotics is understood in a broad sense: asymptotic solutions of evolutionary and stationary partial differential equations from wave or quantum mechanics are expressed through solutions of the corresponding equations of classical mechanics. This, in particular, allows one to use useful geometric considerations. The small parameter of the expansion is h = λ / 2 π L where λ is the wavelength and L the dimension of the system. In order to apply the asymptotic algorithm, we need this parameter to be small, so we deal only with high-frequency waves, which are in the range of lower hybrid waves used to heat the plasma. The asymptotic solution appears to be a Gaussian wave packet divided by the square root of the determinant of an appropriate Jacobi matrix (“complex divergence”). When this determinant is zero, focal points appear. Our approach allows one to write out asymptotics near focal points. We also claim that this approach is very practical and leads to formulas that can be used for numerical simulations in software like Wolfram Mathematica, Maple, etc. For the particular case of high-frequency beams, we present a recipe for constructing beams and packets and show the results of their numerical implementation. We also propose ideas to treat the more difficult general case of arbitrary frequency. We also explain the main ideas of asymptotic theory used to obtain such formulas.

scholarly journals Musik Gamelan Bali Meningkatkan Pertumbuhan dan Produktivitas Tanaman Sawi Pakcoy (Brassica rafa L.)

2018 ◽  
Vol 6 (2) ◽  
pp. 73
Author(s):  
Dewa Putu Yoga Gautama ◽  
I Made Anom S. Wijaya ◽  
I Wayan Widia
Keyword(s):  
Plant Growth ◽  
Plant Height ◽  
High Frequency ◽  
Dry Weight ◽  
Sound Waves ◽  
High Frequency Sound ◽  
Frequency Sound ◽  
Green Leaves ◽  
Mustard Plant ◽  
Canopy Area

Pemberian gelombang suara dengan frekuensi tinggi dapat merangsang mulut daun  (stomata) tetap terbuka, akibatnya laju dan efisiensi penyerapan pupuk meningkat yang bermanfaat bagi tanaman. Hasil penggunaan sonic bloom pada tanaman adalah mampu menstimulir metabolisme sel-sel tanaman, sehingga terjadi peningkatan penyerapan nutrisi dan uap air lewat daun yang berpengaruh pada pertumbuhan dan produktivitas tanaman. Tujuan dari penelitian ini yaitu (1) untuk mengetahui pengaruh pemberian musik Gamelan Bali terhadap pertumbuhan dan produktivitas tanaman sawi pakcoy dan (2) untuk menentukan jenis musik Gamelan Bali yang memberikan pertumbuhan dan produktivitas sawi pakcoy yang terbaik. Penelitan ini menggunakan tanaman sawi pakcoy (Brassica Rafa L.).  Perlakuan yang diberikan  dalam penelitian adalah pemberian musik gamelan bali dengan nuansa musik yang berbeda. Perlakuan 1 menggunakan musik gamelan Angklung, Perlakuan 2 menggunakan musik gamelan Semarpagulingan dan Perlakuan 3 menggunakan musik gamelan Gong Kebyar. Data yang diperoleh dianalis ANOVA dengan program IBM SPSS 20. Variabel yang diamati yaitu tinggi tanaman, luas kanopi daun tanaman, tingkat kehijauan daun tanaman, dan berat kering. Hasil penelitian menunjukan bahwa pemberian musik gong kebyar menghasilkan nilai tertinggi pada variabel tinggi tanaman, luas kanopi daun, tingkat kehijauan daun, dan berat kering yang  masing menghasilkan nilai yaitu yaitu 29,98 cm, 1684 cm2, 186,79, dan 68,61 gr. Pemberian musik memberikan pengaruh yang positif dan berbeda nyata pada pertumbuhan tanaman sawi pakcoy. Semakin tinggi frekuensi musik yang diberikan maka semakin baik pertumbuhan tanaman sawi pakcoy yang dihasilkan.  High frequency sound waves can stimulate the mouth of leaf (stomata) remains opened.The stomata remains open leading to efficient absorption of fertilizer. The purposes of this research were (1) to find out the effect of Balinese instrument music on the growth and productivity of pakcoy mustard plant and (2) to determine the type of Balinese instrument music that gives the best growth and productivity of mustard pakcoy. The treatment of this research was the application of Balinese instrument music with different musical nuances for 3 hours. Treatment 1 was using Angklung instruments music, treatment 2 was using Semarpagulingan instrument music and treatment 3 using Gong Kebyar instrument music. The obtained data was analized by ANOVA with the IBM SPSS 20 program. The observed variables include plant height, canopy area of plant leaf, green leaves level and dry weight. The results showed that Gong Kebyar instrument music application produces the highest value of 29.98 on the height of the plant variables, the widest value of 1684 cm2  on the canopy area variables, the biggest value that is 68,61 gr on the dry weight variables and the largest value of 186.79 on the green leaves level variables. Balinese instrument music application effect to the growth of pakcoy mustard plant. The best plant growth was the plant with gong kebyar instrument music application from all observed variables.

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