Effect of bed roughness on velocity profile and water entrainment in a sedimentary density current

2018 ◽  
Vol 45 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Seyed Mahmood Kashefipour ◽  
Mehdi Daryaee ◽  
Mehdi Ghomeshi
Keyword(s):  
Velocity Profile ◽  
Richardson Number ◽  
Density Current ◽  
Wall Region ◽  
Density Currents ◽  
Relative Roughness ◽  
Bed Roughness ◽  
Water Entrainment ◽  
Relationship Of ◽  
The Relationship

In this study, the effect of bed roughness on velocity profile and water entrainment in a sedimentary density current for Richardson numbers of 1.2–7 (subcritical flow conditions) was investigated. Experiments were carried out in a tilting flume with four different bed slopes, four roughness heights, and two fluid densities of sedimentary density currents. The results showed that bed roughness significantly affects the general shapes of velocity profiles, especially in the wall region. Two empirical equations were developed as the functions of the relative roughness for the wall and jet regions of velocity profile using the measured velocities of density currents. Water entrainment was also affected by bed roughness and an empirical equation was developed describing the relationship of this phenomenon with the Richardson number and relative roughness. Sensitivity analysis of this equation by using elasticity coefficient method showed that the effectiveness of the Richardson number is 3.9 times more than the effect of relative roughness on water entrainment.

Three‐dimensional velocity profile inversion from finite‐offset scattering data

Geophysics ◽  
1981 ◽  
Vol 46 (6) ◽  
pp. 837-842 ◽  
Author(s):  
S. Raz
Keyword(s):  
Velocity Profile ◽  
Three Dimensional ◽  
Scattering Data ◽  
One Dimensional ◽  
Velocity Variations ◽  
Profile Inversion ◽  
Relationship Of ◽  
The Relationship

The reconstruction of three‐dimensional (3-D) velocity variations from finite‐offset scattering data is formulated. Reduction to the limiting cases of zero and small offset distances as well as the case of one‐dimensional (1-D) stratification is given. An inherent increase in complexity is cited and interpreted. The relationship of the proposed inversion to the F-K migration is discussed.

scholarly journals The Relationship of Maximal Strength with the Force-Velocity Profile in Resistance Trained Women

2021 ◽  
Vol 18 (5) ◽  
pp. 173-185
Author(s):  
Gergely Pálinkás ◽  
Bettina Béres ◽  
Zsófia Tróznai ◽  
Katinka Utczás ◽  
Leonidas Petridis
Keyword(s):  
Velocity Profile ◽  
Maximal Strength ◽  
Force Velocity ◽  
Relationship Of ◽  
The Relationship

scholarly journals Experimental observation of saline underflows and turbidity currents, flowing over rough beds

2015 ◽  
Vol 42 (11) ◽  
pp. 834-844 ◽  
Author(s):  
Peyman Varjavand ◽  
Mehdi Ghomeshi ◽  
Ali Hosseinzadeh Dalir ◽  
Davood Farsadizadeh ◽  
Alireza Docheshmeh Gorgij
Keyword(s):  
Cross Sections ◽  
Turbidity Currents ◽  
Density Current ◽  
Normal Velocity ◽  
Density Currents ◽  
Transport Mechanisms ◽  
Maximum Value ◽  
Bed Roughness ◽  
Rough Beds ◽  
Peak Value

Density currents are formed when gravity acts upon a density difference between two different fluids, and the driving force is the buoyancy force. These currents are the most important transport mechanisms and deposition of noncohesive sediments in narrow and deep reservoirs. In this research, 126 experiments were performed to investigate the effects of artificial bed roughness on saline and sediment-laden density currents. Conic and cylindrical shapes of roughness were used with three different heights. Velocity and concentration profiles were measured in 4 and 3 cross-sections, respectively. Presence of roughness causes increasing density current body thickness, decreasing maximum value of velocity and increasing distance of peak value of velocity point from the bed in the normal velocity profile. Coefficient of entrainment in the rough beds was more than in smooth beds and increased for greater roughness heights. A special behavior, referred to as “lifting phenomenon”, was present in some of the tests and which had an effect on the velocity profiles.

The long-term circulation driven by density currents in a two-layer stratified basin

2007 ◽  
Vol 572 ◽  
pp. 37-58 ◽  
Author(s):  
M. G. WELLS ◽  
J. S. WETTLAUFER
Keyword(s):  
Richardson Number ◽  
Slope Angle ◽  
Impact Angle ◽  
Buoyancy Flux ◽  
The Arctic ◽  
Density Current ◽  
Entrainment Rate ◽  
Density Currents ◽  
Penetrative Convection

Experimentation and theory are used to study the long-term dynamics of a two-dimensional density current flowing into a two-layer stratified basin. When the initial Richardson number, $\hbox{\it Ri}_{\rho}^{\hbox{\scriptsize\it in}}$, characterizing the ratio of the background stratification to the buoyancy flux of the density current, is less than the critical value of $\hbox{\it Ri}_{\rho}^{*} \,{=}\, 21-27$, it is found that the density current penetrates the stratified interface. This result is ostensibly independent of slope for angles between 30° and 90°. If the current does not initially penetrate the interface, then it slowly increases the density of the top layer until the interfacial density difference is reduced sufficiently to drive penetration. The time scale for this to occur, $t_{p} \,{=}\, (\hbox{\it Ri}^{\hbox{\scriptsize\it in}}_{\rho} - \hbox{\it Ri}_{\rho}^{*}) L/B^{1/3}$, is explicitly a function of the buoyancy flux B and the length of the basin L. The initial Richardson number, $\hbox{\it Ri}^{\hbox{\scriptsize\it in}}_{\rho}$, is a function of depth, the initial reduced gravity of the interface and a weak function of slope angle. In the absence of initial penetration for very steep slopes of 75° and 90°, we observe that penetrative convection at the interface leads to significant local entrainment. In consequence, the top layer thickens and the interfacial entrainment rate increases as the fifth power of the interfacial Froude number. In contrast, such a process is not observed at comparable interfacial Froude numbers on lower slopes of 30°, 45° and 60°, thereby demonstrating the important role of impact angle on penetrative convection. We attribute the increased interfacial entrainment by the steep density currents as the result of the transition from an undular bore to a turbulent hydraulic jump at the point where the density current intrudes. We discuss the applicability of the observed circulation to the stability of the Arctic halocline where we find $0.56\,{\lesssim}\, t_{p} \,{\lesssim}\,1.2$ years for a range of contemporary oceanographic conditions.

The relationship of the scleractinian corals to the rugose corals

Paleobiology ◽  
1980 ◽  
Vol 6 (02) ◽  
pp. 146-160 ◽  
Author(s):  
William A. Oliver
Keyword(s):  
Critical Points ◽  
Scleractinian Corals ◽  
Convincing Evidence ◽  
Early Triassic ◽  
Rugose Corals ◽  
History Of ◽  
The Subject ◽  
Relationship Of ◽  
The Relationship ◽  
Biologic Factors

The Mesozoic-Cenozoic coral Order Scleractinia has been suggested to have originated or evolved (1) by direct descent from the Paleozoic Order Rugosa or (2) by the development of a skeleton in members of one of the anemone groups that probably have existed throughout Phanerozoic time. In spite of much work on the subject, advocates of the direct descent hypothesis have failed to find convincing evidence of this relationship. Critical points are:(1) Rugosan septal insertion is serial; Scleractinian insertion is cyclic; no intermediate stages have been demonstrated. Apparent intermediates are Scleractinia having bilateral cyclic insertion or teratological Rugosa.(2) There is convincing evidence that the skeletons of many Rugosa were calcitic and none are known to be or to have been aragonitic. In contrast, the skeletons of all living Scleractinia are aragonitic and there is evidence that fossil Scleractinia were aragonitic also. The mineralogic difference is almost certainly due to intrinsic biologic factors.(3) No early Triassic corals of either group are known. This fact is not compelling (by itself) but is important in connection with points 1 and 2, because, given direct descent, both changes took place during this only stage in the history of the two groups in which there are no known corals.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

Studies on Leukemogenic and Sarcomagenic Viruses

1970 ◽  
Vol 28 ◽  
pp. 156-157
Author(s):  
Leon Dmochowski
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Morphological Properties ◽  
Mode Of Development ◽  
Relationship Of ◽  
The Relationship

Electron microscopy has proved to be an invaluable discipline in studies on the relationship of viruses to the origin of leukemia, sarcoma, and other types of tumors in animals and man. The successful cell-free transmission of leukemia and sarcoma in mice, rats, hamsters, and cats, interpreted as due to a virus or viruses, was proved to be due to a virus on the basis of electron microscope studies. These studies demonstrated that all the types of neoplasia in animals of the species examined are produced by a virus of certain characteristic morphological properties similar, if not identical, in the mode of development in all types of neoplasia in animals, as shown in Fig. 1.

The relationship of IGE receptor topography to signaling activity in RBL-2H3 mast cells

1991 ◽  
Vol 49 ◽  
pp. 236-237
Author(s):  
J.R. Pfeiffer ◽  
J.C. Seagrave ◽  
C. Wofsy ◽  
J.M. Oliver
Keyword(s):  
Mast Cells ◽  
Protein A ◽  
Scattered Electron ◽  
Ige Receptor ◽  
Receptor Complexes ◽  
Ige Binding ◽  
Electron Imaging ◽  
Small Clusters ◽  
Relationship Of ◽  
The Relationship

In RBL-2H3 rat leukemic mast cells, crosslinking IgE-receptor complexes with anti-IgE antibody leads to degranulation. Receptor crosslinking also stimulates the redistribution of receptors on the cell surface, a process that can be observed by labeling the anti-IgE with 15 nm protein A-gold particles as described in Stump et al. (1989), followed by back-scattered electron imaging (BEI) in the scanning electron microscope. We report that anti-IgE binding stimulates the redistribution of IgE-receptor complexes at 37“C from a dispersed topography (singlets and doublets; S/D) to distributions dominated sequentially by short chains, small clusters and large aggregates of crosslinked receptors. These patterns can be observed (Figure 1), quantified (Figure 2) and analyzed statistically. Cells incubated with 1 μg/ml anti-IgE, a concentration that stimulates maximum net secretion, redistribute receptors as far as chains and small clusters during a 15 min incubation period. At 3 and 10 μg/ml anti-IgE, net secretion is reduced and the majority of receptors redistribute rapidly into clusters and large aggregates.

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