Non-linear wave loads on large circular cylinders: a perturbation technique     

M. Rahman 《Advances in water resources》1981,4(1):9-19

The forces and overturning moments exerted by second order waves on large vertical circular cylinders are analysed. The mathematical equations governing the physical system are the three-dimensional Laplace's equation satisfied by the velocity potential ?(x,y,z,t) and the boundary conditions, namely the dynamic boundary condition which is obtained from the Bernoulli's equation, kinematic boundary condition, radiation condition, bottom boundary condition and the zero radial velocity condition on the surface of the cylinder. The non-linearity of the mathematical problem is evidenced in the free surface boundary conditions viz. dynamic and kinematic boundary conditions. Analytical solutions are obtained using the perturbation technique. These solutions are compared with various experimental data. The comparison shows favourable agreement between the theory and the experimental results.  相似文献   

Second international Islamic geography conference     

Mushtaqur Rahman 《GeoJournal》1982,6(6):571-571

  相似文献   

Numerical solutions of ideal two-fluid equations very closed to the event horizon of Schwarzschild black hole     

M. Atiqur Rahman 《Astrophysics and Space Science》2012,342(2):333-350

The 3+1 formalism of Thorne, Price and MacDonald has been used to derive the linear two-fluid equations describing transverse and longitudinal waves propagating in the two-fluid ideal collisionless plasmas surrounding a Schwarzschild black hole. The plasma is assumed to be falling in radial direction toward the event horizon. The relativistic two-fluid equations have been reformulate, in analogy with the special relativistic formulation as explained in an earlier paper, to take account of relativistic effects due to the event horizon. Here a WKB approximation is used to derive the local dispersion relation for these waves and solved numerically for the wave number k.  相似文献   

Shock waves in a dusty plasma with dust of opposite polarities     

Armina Rahman  A. A. Mamun  S. M. Khurshed Alam 《Astrophysics and Space Science》2008,315(1-4):243-247

A four-component dusty plasma consisting of electrons, ions, and negative as well as positive dust particles has been considered. The basic features of shock waves that may exist in such a four-component dusty plasma have been theoretically investigated by the reductive perturbation method. The implications of our results in different regions of space (viz. cometary tails, mesosphere, Jupiter’s magnetosphere, etc.) are briefly discussed.  相似文献   

High resolution facies architecture and digital outcrop modeling of the Sandakan formation sandstone reservoir,Borneo:Implications for reservoir characterization and flow simulation     

Numair A.Siddiqui  Mu.Ramkumar  Abdul Hadi A.Rahman  Manoj J.Mathew  M.Santosh  Chow W.Sum  David Menier 《地学前缘(英文版)》2019,10(3):957-971

Advances in photogrammetry have eased the acquisition of high-resolution digital information from outcrops, enabling faster, non-destructive data capturing and improved reservoir modeling. Geocellular models for flow dynamics with in the virtual outcrop in siliciclastic deposits at different sets of sandstone facies architecture remain, however, a challenge. Digital maps of bedding, lithological contrast, spatial-temporal variations of bedding and permeability characteristics make it more easy to understand flow tortuosity in a particular architecture. An ability to precisely model these properties can improve reservoir characterization and flow modeling at different scales. Here we demonstrate the construction of realistic 2 D sandstone facies based models for a pragmatic simulation of flow dynamics using a combination of digital point clouds dataset acquired from LiDAR and field investigation of the Sandakan Formation, Sabah, Borneo.Additionally, we present methods for enhancing the accuracy of outcrop digital datasets for producing high resolution flow simulation. A well-exposed outcrop from the Sandakan Formation, Sabah, northwest Borneo having a lateral extent of 750 m was chosen in order to implement our research approach. Sandstone facies and its connectivity are well constrained by outcrop observations, data from air-permeability measurements, bilinear interpolation of permeability, grid construction and water vector analysis for flow dynamics.These proportions were then enumerated in terms of static digital outcrop model(DOM) and facies model based on sandstone facies bedding characteristics. Flow simulation of water vector analysis through each of the four sandstone facies types show persistent spatial correlation of permeability that align with either cross-bedded orientation or straight with more dispersion high quality sandstone(porosity 21.25%-41.2%and permeability 1265.20-5986.25 mD) and moderate quality sandstone(porosity 10.44%-28.75% and permeability 21.44-1023.33 mD). Whereas, in more heterolithic sandstone(wavy-to flaser-bedded and bioturbated sandstone), lateral variations in permeability show spatially non-correlated patterns over centimeters to tens of meters with mostly of low quality sandstone(porosity 3.4%-12.31% and permeability < 1 mD to 3.21 mD). These variations reflect the lateral juxtaposition in flow dynamics. It has also been resulted that the vertical connectivity and heterogeneities in terms of flow are mostly pragmatic due to the interconnected sandstone rather than the quality of sandstone.  相似文献   

Bacterial Proliferation in Municipal Water Supplied in Mirpur Locality of Dhaka City,Bangladesh          下载免费PDF全文

Mrityunjoy Acharjee  Farjana Rahman  Fahmida Jahan  Rashed Noor 《洁净——土壤、空气、水》2014,42(4):434-441

  相似文献   

Probabilistic analysis for wave‐induced submarine landslides     

M. S. Rahman  F. M. Layas 《Marine Georesources & Geotechnology》2013,31(1):99-115

Abstract

When waves propagate over the ocean floor, they induce a change of hydrodynamic pressure, positive under the crest and negative under the trough. These pressure changes may cause shear failure in soft sediments and lead to submarine landslides. This paper presents a general analytical procedure for evaluating the probability of wave‐induced failure in offshore clay sediments. Both the wave and the un‐drained shear strength of clay sediments are considered random. Numerical results of some analyses are also presented.  相似文献   

Wave‐induced pore pressure in relation to ocean floor stability of cohesionless soils     

H. Bolton Seed  M. S. Rahman 《Marine Georesources & Geotechnology》2013,31(2):123-150

One of the important geotechnical considerations for many engineering installations, such as pipelines and anchors, in an oceanic environment involving sand deposits is that of potential ocean floor instability due to the development of high pore pressures caused by the direct action of waves. This article presents a procedure for evaluating the magnitude and distribution of wave‐induced pore pressures in ocean floor deposits. The method takes into account the distribution of wave‐induced pore pressures in ocean floor deposits. The method takes into account the distribution of cyclic shear stresses in the soil profile as well as the important factor of pore‐pressure dissipation. The variation of properties within the soil profile can also be easily incorporated into the analytical procedure. The analysis provides the complete time history of pore‐pressure response and shows clearly that failure to include the pore‐pressure dissipation effects would lead to radically conservative design. The results also provide a basis for designing remedial measures, if required, to avert the development of high pore pressures and their deleterious effects.  相似文献   

Upregulation of hypoxia-inducible factor (HIF)-1α and HIF-2α mRNA levels in dragonet Callionymus valenciennei exposed to environmental hypoxia in Tokyo Bay     

Kodama K  Rahman MS  Horiguchi T  Thomas P 《Marine pollution bulletin》2012,64(7):1339-1347

  相似文献   

Geospatial and geostatistical approach for groundwater potential zone delineation   总被引：1，自引：0，他引：1       下载免费PDF全文

Javed Mallick  Chander Kumar Singh  Hussein Al‐Wadi  Mohd Ahmed  Atiqur Rahman  Satyanarayan Shashtri  Saumitra Mukherjee 《水文研究》2015,29(3):395-418

Over the past few decades, groundwater has become an essential commodity owing to increased demand as a result of growing population, industrialization, urbanization and so on. The water supply situation is expected to become more severe in the future because of continued unsustainable water use and projected change in hydrometeorological parameters due to climate change. This study is based on the integrated approach of remote sensing, geographical information system and multicriteria decision‐making techniques to determine the most important contributing factors that affect the groundwater resources and to delineate the groundwater potential zones. Ten thematic layers, namely, geomorphology, geology, soil, topographic elevation (digital elevation model), land use/land cover, drainage density, lineament density, proximity of surface water bodies, surface temperature and post‐monsoon groundwater depth, were considered for the present study. These thematic layers were selected for groundwater prospecting based on the literature; discussion with the experts of the Central Ground Water Board, Government of India; field observations; geophysical investigation; and multivariate techniques. The thematic layers and their features were assigned suitable weights on Saaty's scale according to their relative significance for groundwater occurrence. The assigned weights of the layers and their features were normalized by using the analytic hierarchy process and eigenvector method. Finally, the selected thematic maps were integrated using a weighted linear combination method to create the final groundwater potential zone map. The final output map shows different zones of groundwater potential, namely, very good (16%), good (35%), moderate (28%) low (17%) and very low (2.1%). The groundwater potential zone map was finally validated using the discharge and groundwater depth data from 28 and 98 pumping wells, respectively, which showed good correlation. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献