scholarly journals SAND RIPPLE GEOMETRY AND SAND TRANSPORT MECHANISM DUE TO IRREGULAR OSCILLATORY FLOWS

1988 ◽  
Vol 1 (21) ◽  
pp. 129 ◽  
Author(s):  
Shinji Sato ◽  
Kiyoshi Horikawa
Keyword(s):  
Transport Mechanism ◽  
Field Data ◽  
Sand Transport ◽  
Laboratory Measurements ◽  
Oscillatory Flows ◽  
Sand Ripples ◽  
Irregular Wave ◽  
Sand Ripple ◽  
Empirical Relations ◽  
Flow Transport

This paper describes characteristics of sand ripples and sand transport mechanism in regular and irregular oscillatory flows on the basis of detailed laboratory measurements. A set of empirical relations were proposed to evaluate the sand ripple geometry as well as the onset of the sheet flow transport. The applicability of the proposed relationships to the irregular wave conditions with prototype scales was confirmed with existing field data.

Wave-induced sand ripples

1982 ◽  
Vol 9 (2) ◽  
pp. 285-295 ◽  
Author(s):  
Michael C. Quick
Keyword(s):  
Velocity Field ◽  
Fluid Velocity ◽  
Sand Transport ◽  
Sediment Characteristics ◽  
Sand Ripples ◽  
Sand Ripple ◽  
Wave Orbital Velocity ◽  
Wave Induced ◽  
Flat Sand

Development of sand ripples from a flat sand bed subjected to shallow water wave action is explained in terms of the unsteady kinematics of the sand particles that form the sand ripple. The steady kinematic requirements for a fully developed sand ripple are also specified, and are shown to be consistent with an idealized solution of the fluid velocity field near the sand bed. This idealized velocity field is a result of the interaction between the surface wave velocity field and the sand ripple shape. The velocity field is related to the sand transport rate by using an adaptation of Bagnold's transport equation for steady flow. Expressions are derived that define the maximum ripple height and wavelength in terms of the wave orbital velocity and sediment characteristics. Theoretical estimates are made of the vortex strength shed from the ripple crest and the role of this crest vortex is considered. Keywords: Sedimentation, sediment transport, waves, ripples, coastal engineering, hydrodynamics.

scholarly journals LABORATORY STUDY ON TWO-DIMENSIONAL BEACH TRANSFORMATION DUE TO IRREGULAR WAVES

1986 ◽  
Vol 1 (20) ◽  
pp. 102 ◽  
Author(s):  
Nubuo Mimura ◽  
Yukinori Otsuka ◽  
Akira Watanabe
Keyword(s):  
Wave Train ◽  
Irregular Waves ◽  
Two Dimensional ◽  
Beach Profile ◽  
Irregular Wave ◽  
Sand Ripple ◽  
Ripple Formation ◽  
Sand Movement ◽  
Incident Waves ◽  
Profile Change

In the present study, effects of irregular waves on two-dimensional beach transformation and related phenomena were investigated through a series of laboratory experiments. Attempts were made to determine a representative wave of irregular wave trains which controlled individual phenomenon related to the two-dimensional beach profile change. It was found that the representative wave is different for each phenomenon. For the macroscopic beach profile change, it is the mean wave which represents whole incident waves. On the other hand, some of microscopic phenomena, such as initiation of sand movement and sand ripple formation, are controlled by larger waves in the wave train selectively, of which representative wave is the significant wave.

scholarly journals ENVIRONMENTAL CONTROLS ON LITTORAL SAND TRANSPORT

1988 ◽  
Vol 1 (21) ◽  
pp. 92 ◽  
Author(s):  
Paul D. Komar
Keyword(s):  
Environmental Factors ◽  
Field Data ◽  
Measurement Techniques ◽  
Breaking Waves ◽  
Total Power ◽  
Sand Transport ◽  
Longshore Current ◽  
Data Set ◽  
Environmental Controls ◽  
Gravel Beaches

Quantities of sand transported along beaches are generally related to the "longshore component of wave power", F^, through the proportionality is = KF£ where l8 is the immersed-weight sand transport rate and K is a dimensionless proportionality factor. A more-generally applicable relationship is that of Bagnold, ls = K'(ECn)bvL/um where (ECn)b is the energy flux or total power of the breaking waves, y^ is the longshore current, um is the mean orbital velocity under the waves, and K' is another dimensionless coefficient. It is apparent that sediment transport rates on beaches should depend on environmental factors such as the grain diameter or settling velocity, and possibly on factors such as the beach slope or wave steepness. However, examinations of such dependencies for K and K' within the field data are hampered by problems with large random scatter within any one data set, and by systematic differences between separate studies which have employed diverse measurement techniques. Examinations of the field data for K and K' variations indicate that meaningful dependencies on sediment grain diameters and other factors cannot be established with confidence in the sand-size range. Limited data available from gravel beaches support the expected decreases in K and K' with increasing grain sizes. These data are too few in numbers to establish firm trends, but do suggest that future investigations to establish dependencies on environmental factors would be most profitably undertaken on gravel beaches. The measurements collected in recent years from sand beaches suggest revisions in average K and K' coefficients to be used in transport evaluations, but such revisions must be coordinated such that K/K' = 2.7 so as to maintain agreement with the longshore current data.

scholarly journals Effects of three-dimensional electric field on saltation during dust storms: An observational and numerical study

2019 ◽  
Author(s):  
Huan Zhang ◽  
You-He Zhou
Keyword(s):  
Electric Field ◽  
Field Data ◽  
Numerical Study ◽  
Three Dimensional ◽  
Vertical Component ◽  
Dust Storms ◽  
Dust Particles ◽  
Sand Transport ◽  
Dust Transport ◽  
Dust Events

Abstract. Particle tribo-electrification being ubiquitous in nature and industry, potentially plays a key role in dust events, including the lifting and transport of sand and dust particles. However, the properties of electric field (E-field) and its influences on saltation during dust storms remain obscure as the high complexity of dust storms and the existing numerical studies mainly limited to one-dimensional (1-D) E-field. Here, we quantify the effects of real three-dimensional (3-D) E-field on saltation, through a combination of field observations and numerical modelling. The 3-D E-fields in the sub-meter layer from 0.05 to 0.7 m above the ground during a dust storm are measured at Qingtu Lake Observation Array site. The measured results show that each component of the 3-D E-field data nearly collapses on a single 3-order polynomial curve when normalized. Interestingly, the vertical component of the 3-D E-field increases with increasing height in the saltation layer during dust storms. Such 3-D E-field data close to the ground within a few centimeters has never been reported and formulated before. Using the discrete element method, we then develop a comprehensive saltation model, in which the tribo-electrification between particle-particle midair collisions is explicitly accounted for, allowing us to evaluate the tribo-electrification in saltation properly. By combining the results of measurements and modelling, we find that although the vertical component of the E-field (i.e. 1-D E-field) inhibits sand transport, 3-D E-field enhances sand transport substantially. Furthermore, the model predicts that 3-D E-field enhances the total mass flux by up to 63 %. This suggests that a truly 3-D E-field consideration is necessary if one is to explain precisely how the E-field affects saltation during dust storms. These results will further improve our understanding of particle tribo-electrification in saltation and help to provide more accurate characterizations of sand and dust transport during dust storms.

APPLICATION OF CONTINUOUS VELOCITY LOGS TO DETERMINATION OF FLUID SATURATION OF RESERVOIR ROCKS

Geophysics ◽  
1956 ◽  
Vol 21 (3) ◽  
pp. 739-754 ◽  
Author(s):  
Warren G. Hicks ◽  
James E. Berry
Keyword(s):  
Field Data ◽  
Acoustic Velocity ◽  
Gas Oil ◽  
Laboratory Measurements ◽  
Reservoir Rocks ◽  
Fluid Saturation ◽  
Saturated Sands ◽  
Similar Character ◽  
Water Saturated

Recent studies of continuous acoustic velocity logs indicate that these logs may provide important assistance in differentiating gas, oil, and water saturations in reservoir rocks. In general, velocities are appreciably lower in sands carrying oil or gas than in water‐saturated sands of otherwise similar character. Specific examples from field logs illustrate this application. Laboratory measurements have been made of acoustic velocity of synthetic and natural rocks. Published studies, both empirical and theoretical, of other workers concerned with the transmission of sound in porous media have been considered. All of these at least qualitatively confirm the conclusions drawn from field data.

THE USE OF ACOUSTIC LOGS IN THE EVALUATION OF SANDSTONE RESERVOIRS

Geophysics ◽  
1960 ◽  
Vol 25 (1) ◽  
pp. 250-274 ◽  
Author(s):  
G. R. Pickett
Keyword(s):  
Acoustic Velocity ◽  
Pressure Differential ◽  
Well Bore ◽  
Laboratory Measurements ◽  
Theoretical Relation ◽  
Hexagonal Packing ◽  
Empirical Relations ◽  
Borehole Logs ◽  
Acoustic Velocities ◽  
Self Potential

It is shown that acoustic velocities in sandstones are primarily dependent on porosity, shaliness, and pressure differential between overburden and fluid pressures. Although there are undoubtedly other variables which have some effect on acoustic velocities in sandstones, usable porosity predictions can be made from acoustic borehole logs if measured velocities are corrected for effects of pressure differential and shaliness. A theoretical relation between acoustic velocity and pressure differential in a hexagonal packing of spheres has been empirically extended by correlation of laboratory measurements on cores with actual well‐bore measurements. A system of empirical relations among acoustic velocity, porosity, and self potential of sandstones is developed. Further, it appears that the resistivity of water in permeable rocks can be estimated from the velocity and resistivity of adjoining shales. When this is possible, the SP log can then be used to estimate the shaliness of a sandstone in order to correct velocities for porosity estimates.

Relationship Between Sand Ripple Moving Speed and Wind Speed under Local Wind Tunnel Experiment by Using Natural Sand in Taklimakan Desert

2008 ◽  
Vol 33-37 ◽  
pp. 1049-1054
Author(s):  
Jurat Matruzi ◽  
Mamtimin Gheni ◽  
Ilham Abdureyim ◽  
Xamxinur Abdikerem
Keyword(s):  
Wind Speed ◽  
Flat Surface ◽  
Taklimakan Desert ◽  
Local Wind ◽  
Natural Sand ◽  
Sand Ripples ◽  
Sand Ripple ◽  
Testing Region ◽  
Moving Process ◽  
Moving Speed

In this study, the directionally fixed air tunnel testing equipment are used for obtain nearly close natural uniform wind and provide more stable wind speed for tunnel test. The changes of sand ripple moving speed in different location are observed under given wind speed condition. The sand ripple lines formation and moving process are tested on flat surface of sand, in Taklimakan desert. The results shown that the sand ripple forming rapidly from non ripple surface to ripple surface and moving along the wind direction. Though the sand ripples in the testing region have some difference about its moving speed, the sand ripple moving speed appear linearity relationship between sand moving displacement and the moving time. This phenomenon indicate that the sand ripple almost occurs and moving at the same time in the uniform wind stream field.

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