scholarly journals FLOW DYNAMICS OF WAVES PROPAGATING OVER DIFFERENT PERMEABLE BEDS

2017 ◽  
pp. 35
Author(s):  
Sara Corvaro ◽  
Alessandro Mancinelli ◽  
Maurizio Brocchini
Keyword(s):  
Shear Stress ◽  
Flow Resistance ◽  
Single Layer ◽  
Coastal Engineering ◽  
Flow Dynamics ◽  
Bottom Shear Stress ◽  
Natural Stones ◽  
Wave Height Attenuation ◽  
Rough Beds ◽  
Good Agreement

The analysis of the hydrodynamics over porous media is of interest for many coastal engineering applications as the wave propagation over permeable structures or gravel beaches. The study of a boundary layer evolving over permeable beds is important to a better understanding of the interactions between the flow over and inside the porous medium. An experimental study has been performed to analyze the dynamics produced when waves propagate over two kinds of permeable beds: spheres (regular permeability) and natural stones. For comparative purposes the same analysis has been extended to two rough beds made, respectively, by a single layer of spheres and natural stones. We here focus on the correlation between the wave energy reduction induced by a porous bed and the flow resistance. An experimental law for the prediction of the friction factor is found by using the log-fit method in analogy to that reported in Dixen et al. (2008) for rough beds. Moreover, inspection of the turbulent velocity components allows one to evaluate the bottom shear stress. The latter analysis has been performed for different permeable beds (regular and irregular beds). A good agreement between the bottom shear stress behavior and the wave height attenuation over rough and permeable beds (Corvaro et al. 2010 and Corvaro et al. 2014a) has been observed.

scholarly journals SUBGRID MODELLING IN DEPTH INTEGRATED FLOWS

1988 ◽  
Vol 1 (21) ◽  
pp. 35 ◽  
Author(s):  
P.A. Madsen ◽  
M. Rugbjerg ◽  
I.R. Warren
Keyword(s):  
Shear Stress ◽  
Large Scale ◽  
Eddy Viscosity ◽  
Grid Size ◽  
Coastal Engineering ◽  
Shear Stresses ◽  
Two Dimensional ◽  
Bottom Shear Stress ◽  
Hydrodynamic Simulations ◽  
Engineering Studies

Hydrodynamic simulations in coastal engineering studies are still most commonly carried out using two-dimensional vertically integrated mathematical models. As yet, threedimensional models are too expensive to be put into general use. However, the tendency with 2-D models is to use finer and finer resolution so that it becomes necessary to include approximations to some 3-D phenomena. It has been shown by many authors that simulations of large scale eddies can be quite realistic in 2-D models (c.f. Abbott et al. 1985). Basically there exists two different mechanisms of circulation generation. The first one is based on a balance between horizontally and grid-resolved momentum transfers and the bed resistance - i.e. a balance between the convective momentum terms and the bottom shear stress. The second one is due to momentum transfers that are not resolved at the grid scale but appears instead as horizontally distributed shear stresses. In many practical situations the circulations will be governed by the first mechanism. This is the case if the diameter of the circulation and the grid size is much larger than the water depth. In this situation the eddies are friction dominated so that the effect of sub-grid eddy viscosity is limited. In this case 2-D models are known to produce very realistic results and several comparisons with measurements have been reported in the literature.

scholarly journals Millisecond lattice gasification for high-density CO2- and O2-sieving nanopores in single-layer graphene

2021 ◽  
Vol 7 (9) ◽  
pp. eabf0116
Author(s):  
Shiqi Huang ◽  
Shaoxian Li ◽  
Luis Francisco Villalobos ◽  
Mostapha Dakhchoune ◽  
Marina Micari ◽  
...  
Keyword(s):  
Single Layer ◽  
High Density ◽  
Single Layer Graphene ◽  
Pore Density ◽  
Vacancy Defects ◽  
Carbon Gasification ◽  
Layer Graphene ◽  
Gas Molecules ◽  
Good Agreement

Etching single-layer graphene to incorporate a high pore density with sub-angstrom precision in molecular differentiation is critical to realize the promising high-flux separation of similar-sized gas molecules, e.g., CO2 from N2. However, rapid etching kinetics needed to achieve the high pore density is challenging to control for such precision. Here, we report a millisecond carbon gasification chemistry incorporating high density (>1012 cm−2) of functional oxygen clusters that then evolve in CO2-sieving vacancy defects under controlled and predictable gasification conditions. A statistical distribution of nanopore lattice isomers is observed, in good agreement with the theoretical solution to the isomer cataloging problem. The gasification technique is scalable, and a centimeter-scale membrane is demonstrated. Last, molecular cutoff could be adjusted by 0.1 Å by in situ expansion of the vacancy defects in an O2 atmosphere. Large CO2 and O2 permeances (>10,000 and 1000 GPU, respectively) are demonstrated accompanying attractive CO2/N2 and O2/N2 selectivities.

scholarly journals RELATIONSHIP BETWEEN BOTTOM SHEAR STRESS AND TURBIDITY IN ESTUARIES

2011 ◽  
Vol 67 (4) ◽  
pp. I_1591-I_1596
Author(s):  
Jun-ichi SAKAMOTO ◽  
Haruhiko MATSUMOTO ◽  
Kesayoshi HADANO ◽  
Takuzo AMANO ◽  
Kiyonobu MITSUNOBU
Keyword(s):  
Shear Stress ◽  
Bottom Shear Stress

Effects of magnetic field on blood flow with suspended copper nanoparticles through an artery with overlapping stenosis

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
C. Umadevi ◽  
G. Harpriya ◽  
M. Dhange ◽  
G. Nageswari
Keyword(s):  
Magnetic Field ◽  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Copper Nanoparticles ◽  
Analytical Solutions ◽  
Biomedical Applications ◽  
Flow Resistance ◽  
Cardiac Diseases ◽  
Stenosed Artery

The flow of blood mixed with copper nanoparticles in an overlapping stenosed artery is reported in the presence of a magnetic field. The presence of stenosis is known to impede blood flow and to be the cause of different cardiac diseases. The governing nonlinear equations are rendered dimensionless and attempted under the conditions of mild stenosis. The analytical solutions for velocity, resistance to the flow, wall shear stress, temperature, and streamlines are obtained and analyzed through graphs. The obtained outcomes show that the temperature variation in copper nanoparticles concentrated blood is more and flow resistance is less when compared to pure blood. The investigations reveal that copper nanoparticles are effective to reduce the hemodynamics of stenosis and could be helpful in biomedical applications.

TEK KATLI DUVAR DEFORMASYONUNUN GÖRÜNTÜ İŞLEME TEKNİKLERİ KULLANILARAK BELİRLENMESİ

2021 ◽  
Vol 8 (17) ◽  
pp. 21-29
Author(s):  
Abdulkerim İLGÜN ◽  
Ahmad Javid ZIA ◽  
Vahdettin DEMİR ◽  
Abdullah MÜSEVİTOĞLU ◽  
Sadrettin SANCIOĞLU
Keyword(s):  
Image Processing ◽  
Single Layer ◽  
Numerical Data ◽  
Processing Technique ◽  
Image Processing Technique ◽  
Initial State ◽  
Image Digitization ◽  
Sliding Test ◽  
Natural Stones ◽  
Experimental Values

Image processing technique has been used frequently in the solution of engineering problems recently. In engineering studies, photographs are taken at certain intervals between the initial state of the material and the state after the change, and changes during the study are observed with the Image processing technique. Based on these photos, the change is transferred to numerical data and the change of the material is observed thanks to these data. Package program systems are used in Image processing technique applications. But these systems are quite expensive systems. In this study, a simpler and feasible system has been developed. The initial sliding test was carried out on 9 single-layer wall systems with natural stones in 20 * 30 * 10 cm dimensions. The displacement values formed on the walls under load during the experiments were measured with the help of potentiometric linear rulers. At the same time, photographs were taken at certain intervals from the baseline to the conclusion of the experiment. The photographs were digitized in the ArcGIS program and the changes on the wall were converted into numerical data. Experimental data and data obtained by photographs were compared. As a result of this comparison, 84% similarity is observed between experimental values and analytical values. It is observed that the image digitization application performed as a result of the study yielded very successful results. In this context, it is believed that the use of this system will be both fast and economically beneficial in larger scale experiments and the number of data.

FLOOD HYDRAULICS DUE TO EMERGENT VEGETATION ALONG A RIPARIAN ZONE IN MEANDERING CHANNELS

2016 ◽  
Vol 78 (9-4) ◽  
Author(s):  
Zulkiflee Ibrahim ◽  
Zulhilmi Ismail ◽  
Sobri Harun ◽  
Koji Shiono ◽  
Nazirah Mohd. Zuki ◽  
...  
Keyword(s):  
Shear Stress ◽  
Flow Resistance ◽  
Riparian Zone ◽  
Streamwise Vorticity ◽  
Floodplain Vegetation ◽  
Meandering Channel ◽  
Meandering Channels ◽  
Boundary Shear ◽  
Residential Properties ◽  
Boundary Shear Stress

Frequent floods around the globe including recent events in several states in Malaysia have damaged the residential properties, infrastructures and crops or even deaths. Clearing vegetations or trees on the floodplain has been pointed out as a contributing factor to the damages. Thus, the influence of floodplain vegetation on the river hydraulics during flooding must be better understood. The hydraulics of flood flows in non-erodible vegetated meandering channel was experimented in the laboratory where two-lined steel rods were installed along a riparian zone to simulate as trees. The stage-discharge relationship, flow resistance, depth-averaged velocity, streamwise vorticity and boundary shear stress patterns during shallow and deep flood inundations were studied. The findings showed that floodplain vegetation had increased the channel flow depth by 32% and its flow resistance. The velocity in vegetated zone was lowered and the shear stress reduced by 86.5% to 91% along the river meander. In addition, the trees also limit flow interaction between main channel and floodplain

Dual Band Slot Antenna for 3.5 WiMAX and 5.8 WLAN

2014 ◽  
Vol 68 (1) ◽  
Author(s):  
Sahar Chagharvand ◽  
M. R. B. Hamid ◽  
M. R. Kamarudin ◽  
Mohsen Khalily
Keyword(s):  
Radiation Pattern ◽  
Coplanar Waveguide ◽  
Single Layer ◽  
Dual Band ◽  
Slot Antenna ◽  
Impedance Bandwidth ◽  
Antenna Gain ◽  
Dual Bandwidth ◽  
Electromagnetic Performance ◽  
Good Agreement

This paper presents a single layer planar slot antenna for dual band operation. The antenna is fed by a coplanar waveguide (CPW) with two inverted C-shaped resonators to achieve the dual band operation. The impedance bandwidth for ǀS11ǀ < -10dB is 14% in lower band and 7% in higher band. The antenna prototype’s electromagnetic performance, impedance bandwidth, radiation pattern, and antenna gain were measured. The proposed configuration offers a relatively compact, easy to fabricate and dual band performance providing gain between 2 and 4 dBi. The designed antenna has good dual bandwidth covering 3.5 WiMAX and 5.8 WLAN tasks. Experimental and numerical results also showed good agreement after comparison.

Quantitative evaluation of flow dynamics of erythrocytes in microvessels: influence of erythrocyte aggregation

1995 ◽  
Vol 268 (5) ◽  
pp. H1959-H1965 ◽  
Author(s):  
M. Soutani ◽  
Y. Suzuki ◽  
N. Tateishi ◽  
N. Maeda
Keyword(s):  
Flow Resistance ◽  
Circulatory System ◽  
Flow Dynamics ◽  
Erythrocyte Aggregation ◽  
Intensity Change ◽  
Image Analyzer ◽  
Free Layer ◽  
High Shear Rates ◽  
Suspension Viscosity ◽  
Cell Free Layer

Effects of erythrocyte aggregation on the flow dynamics of erythrocytes in microvessels were examined quantitatively by perfusing human erythrocytes suspended in isotonic medium containing various concentrations of dextran (70,400 avg mol wt, Dx-70) into a part of the microvascular bed isolated from rabbit mesentery. Thickness of the marginal cell-free layer was measured with an image analyzer, total flow resistance was determined on the basis of the perfusion pressure-volume flow relationship, and homogeneity of erythrocyte flow was evaluated by the power spectrum obtained by the fast Fourier transform of the light intensity change monitored on single microvessels. With increasing dextran concentration, suspension viscosity of erythrocytes at high shear rates increased linearly and thickness of the cell-free layer increased in a sigmoidal fashion. Flow resistance increased relatively little over the range of dextran concentrations in which the cell-free layer increased most rapidly. Furthermore, the flow pattern of erythrocytes in microvessels became inhomogeneous. In conclusion, the present study shows that Dx-70-induced erythrocyte aggregation results in increased flow resistance in the circulatory system, even through the widening of the cell-free layer tends to reduce the resistance and also results in inhomogeneous flow of erythrocytes in microvessels.

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