Studies on the Application of Steady State Assumption in 1DV Model for the Estimation of Settling Velocity of Suspended Sediments in a Shallow Estuary     

K. L. Priya 《Ocean Science Journal》2018,53(3):449-459

Settling velocity is one of the important parameters in sediment transport modeling of estuaries. The methods adopted for its determination vary from theoretical equations to experimental methods. The theoretical equation generally adopted in the 1DV model include assumptions in order to simplify the solution. It is generally assumed that either the condition is steady or the vertical diffusion is negligible. This study evaluated the relative importance of the two assumptions made for the estimation of settling velocity. Two approaches were adopted: unsteady and negligible vertical diffusion (NS-NVD) and steady with vertical diffusion (S-VD) to estimate the settling velocity. The Muthupet Estuary in the Coromandal coast of India was selected for the study. The S-VD approach estimated settling velocity fairly well at the two locations with appreciable vertical diffusion. The NS-NVD approach was observed to be superior for estimating settling velocity at shallow reaches of the estuary having low flow velocity. The calculated settling velocity was further applied in 1DV model to predict the suspended sediment concentration. The S-VD approach predicted suspended sediment concentration at those locations with appreciable vertical diffusion with an R² value of 0.82 against 0.67 for the NS-NVD approach. At the other shallow reach of the estuary with low flow velocity, the NS-NVD approach gave an R² value of 0.822 against 0.71 for the S-VD approach. The vertical diffusion was observed to play a secondary role at those locations which are shallow with a water depth of 0.6 m and with a low flow velocity of the order of 0.01 m/s. The study demonstrated that localized hydrodynamic conditions influence the method adopted for the estimation of settling velocity.  相似文献   

Influence of gas production induced volumetric strain on permeability of coal   总被引：10，自引：0，他引：10  

Satya Harpalani  Guoliang Chen 《Geotechnical and Geological Engineering》1997,15(4):303-325

Summary The gas permeability of a coalbed, unlike that of conventional gas reservoirs, is influenced during gas production not only by the simultaneous changes in effective stress and gas slippage, but also by the volumetric strain of the coal matrix that is associated with gas desorption. A technique for conducting laboratory experiments to separate these effects and estimate their individual contribution is presented in this paper. The results show that for a pressure decrease from 6.2 to 0.7 MPa, the total permeability of the coal sample increased by more than 17 times. A factor of 12 is due to the volumetric strain effect, and a factor of 5 due to the gas slippage effect. Changes in permeability and porosity with gas depletion were also estimated using the measured volumetric strain and the matchstick reservoir model geometry for flow of gas in coalbeds. The resulting variations were compared with results obtained experimentally. Furthermore, the results show that when gas pressure is above 1.7 MPa, the effect of volumetric strain due to matrix shrinkage dominates. As gas pressure falls below 1.7 MPa, both the gas slippage and matrix shrinkage effects play important roles in influencing the permeability. Finally, the change in permeability associated with matrix shrinkage was found to be linearly proportional to the volumetric strain. Since volumetric strain is linearly proportional to the amount of gas desorbed, the change in permeability is a linear function of the amount of desorbing gas.  相似文献   

Assessment of Kalpana-1 Rainfall Product over Indian Meteorological Sub-Divisions During the Summer Monsoon Season     

M. T. Bushair  Satya Prakash  Shashikant Patel  R. M. Gairola 《Journal of the Indian Society of Remote Sensing》2016,44(1):67-76

In this paper, Kalpana-1 derived INSAT Multispectral Rainfall Algorithm (IMSRA) rainfall estimates are compared with two multisatellite rainfall products namely, TRMM Multisatellite Precipitation Analysis (TMPA)-3B42 and Global Satellite Mapping of Precipitation (GSMaP), and India Meteorological Department (IMD) surface rain gauge (SRG)-based rainfall at meteorological sub-divisional scale over India. The performance of the summer monsoon rainfall of 2013 over Indian meteorological sub-divisions is assessed at different temporal scales. Comparison of daily accumulated rainfall over India from IMSRA shows a linear correlation of 0.72 with TMPA-3B42 and 0.70 with GSMaP estimates. IMSRA is capable to pick up daily rainfall variability over the monsoon trough region as compared to TMPA-3B42 and GSMaP products, but underestimates moderate to heavy rainfall events. Satellite-derived rainfall maps at meteorological sub-divisional scales are in reasonably good agreement with IMD-SRG based rainfall maps with some exceptions. However, IMSRA performs better than GSMaP product at meteorological sub-divisional scale and comparable with TMPA data. All the satellite-derived rainfall products underestimate orographic rainfall along the west coast, the Himalayan foothills and over the northeast India and overestimate rainfall over the southeast peninsular India. Overall results suggest that IMSRA estimates have potential for monsoon rainfall monitoring over the Indian meteorological sub-divisions and can be used for various hydro-meteorological applications.  相似文献   

Hydrogeochemical characterization and quality assessment of groundwater in parts of Southern Gangetic Plain     

Satya N. Sethy  Tajdarul H. Syed  Alok Kumar  Debanjan Sinha 《Environmental Earth Sciences》2016,75(3):232

  相似文献   

Spatio-temporal variations of respirable particles at residential areas located in the vicinity of opencast coal projects,India: a case study     

Satya Prakash Sahu  Manish Yadav  Dhruti Sundar Pradhan  Neha Rani  Arka Jyoti Das 《Arabian Journal of Geosciences》2018,11(10):241

The objective of the study is to investigate spatio-temporal variations of PM₁₀, PM_2.5, and PM₁ concentrations at seven residential sites, located in the vicinity of opencast coal projects, Basundhara Garjanbahal Area (BGA), India. Meteorological parameters such as wind speed, wind direction, relative humidity, and temperature were collected simultaneously with PM concentrations. Mean concentrations of PM₁₀ in the range 215 ± 169–526 ± 412 μg m^?3, PM_2.5 in the range of 91 ± 79–297 ± 107 μg m^?3, PM₁ in the range of 68 ± 60–247 ± 84 μg m^?3 were obtained. Coarse fractions (PM_2.5–10) varied from 27 to 58% whereas fine fractions (PM_1–2.5 and PM₁) varied in the range of 51–73%. PM_2.5 concentration was 41–74% of PM₁₀ concentration, PM₁ concentration was 31–62% of PM₁₀ concentration, and PM₁ concentration was 73–83% of PM_2.5 concentration. Role of meteorology on PM concentrations was assessed using correlation analysis. Linear relationships were established among PM concentrations using least square regression analysis. With the aid of principal component analysis, two components were drawn out of eight variables, which represent more than 75% of variance. The results indicated that major sources of air pollutants (PM₁₀, PM_2.5, PM₁, CO, CO₂) at the residential sites are road dust raised by vehicular movement, spillage of coal generated during transportation, spontaneous combustion of coal, and biomass burning in village area.  相似文献   

Morphologies of AGN host galaxies using HST/ACS in the CDFS-GOODS field     

Priya Hasan 《Astrophysics and Space Science》2007,312(1-2):63-77

Using HST/ACS images in four bands F435W, F606W, F775W and F850LP, we identify optical counterparts to the X-ray sources in the Chandra Deep Field South in the GOODS South field. A detailed study has been made of these sources to study their morphological types. We use methods like decomposition of galaxy luminosity profiles, color maps and visual inspection of 192 galaxies which are identified as possible optical counterparts of Chandra X-ray sources in the CDFS-GOODS field. We find that most moderate luminosity AGN hosts are bulge dominated in the redshift range (z≈0.4–1.3), but not merging/interacting galaxies. This implies probable fueling of the moderate luminosity AGN by mechanisms other than those merger driven.  相似文献   

Determination of the Effective Stress Law for Deformation in Coalbed Methane Reservoirs     

Shimin Liu  Satya Harpalani 《Rock Mechanics and Rock Engineering》2014,47(5):1809-1820

Effective stress laws and their application are not new, but are often overlooked or applied inappropriately. The complexity of using a proper effective stress law increases when analyzing stress variation in coal as a result of gas production or mining. In this paper, an effective stress law is derived analytically for coalbed methane reservoirs, combining the concepts of matrix shrinkage/swelling and external stress by including the effect of sorbing gas pressure on the elastic response of the reservoir. The proposed law reduces to that of Terzaghi when the compressibility of bulk material is sufficiently greater than the compressibility of the solid grain, and without the strain associated with matrix shrinkage/swelling effect. Moreover, it is shown that the Biot coefficient (α) can have a value larger than unity for self-swelling/dilation materials, such as coal. The proposed stress–strain relationship was validated using experimental results. Overall, the effective stress law for deformation was extended for sorptive materials, providing a new and unique technique to analyze the elastic behavior of coal by reducing three variables, namely, external stress, pore pressure and matrix shrinkage/swelling along with the associated stress, down to one variable, “effective stress”.  相似文献   

On structure formation in the universe     

A. Satya Narayanan 《Astrophysics and Space Science》1994,222(1-2):205-212

The formation of structures in the universe is one of the most challenging problems of cosmology. In this paper, an attempt to explain the formation of galaxies through the generation of vortices (with dissipation) in an uniformly expanding perfect fluid is made. The equation governing the mean square vorticity for a turbulent (isotropic and homogeneous) fluid is derived. It is shown that the mechanism of stretching vortices could enhance the mean square vorticity as a function of time. However, ultimately expansion and dissipation dominate and the solution for the mean square vorticity reaches the prediction by linear theory.  相似文献   

Effect of density discontinuity on Alfvén internal gravity waves     

A. Satya Narayanan 《Astrophysics and Space Science》1987,132(1):105-111

The stability characteristics of Alfvén Internal gravity waves for an inviscid, nondissipative, Boussinesq fluid undergoing shear in the presence of a density discontinuity with and without a rigid boundary is studied.  相似文献   

Note on the stability of parallel magnetic fields     

A. Satya Narayanan  K. Somasundaram 《Astrophysics and Space Science》1982,84(1):247-250

The stability characteristics of parallel magnetic fields when fluid motions are present along the lines of force is studied. The stability criterion for both symmetric (m=0) and asymmetric (m=1) modes are discussed and the results obtained by Trehan and Singh (1978) are amended in the present study. The results obtained for the cylindrical geometry are shown to play an important role forka<4, wherek is the wave number,a is the radius of the cylinder, compared to the results obtained by Geronicolas (1977) for the slab geometry.  相似文献