Experimental and Numerical Flow Simulation over Weirs     

Hriday Mani Kalita  Das  Rajdeep  Hajong  Atul  Kumar  Neeraj  Kharnaior  Donly  Dkhar  Heart Casingh 《Water Resources》2019,46(6):934-943

Water Resources - This paper reports a series of experimental studies done to simulate the flow behavior over crump and ogee type of weirs. The transition of subcritical to supercritical flow, as...  相似文献   

Stable carbon isotope geochemistry of adsorbed alkane gases in near-surface soils of the Saurashtra Basin,India     

Devleena Mani  D.J. Patil  A.M. Dayal 《Chemical Geology》2011,280(1-2):144-153

The stable carbon isotopic compositions of light hydrocarbon gases adsorbed in near-surface soil and sediments from the Saurashtra basin were characterized for their origin and maturity. Saurashtra is considered geologically prospective for oil and gas reserves; however, a major part of the basin is covered by the Deccan Traps, hindering the exploration of Mesozoic hydrocarbon targets. Surface geochemical prospecting, based on micro-seepage of hydrocarbons from subsurface accumulations, could be advantageous in such areas. In light of this, 150 soil samples were collected from the northwestern part of Saurashtra, around the Jamnagar area, where a thick sedimentary sequence of about 2–3 km exists under 1–1.5 km of Deccan basalt. The concentration of acid desorbed alkane gases from soil samples was found to vary (in ppb) as: methane (C₁) = 3–518; ethane (C₂) = 0–430; propane (C₃) = 0–331; i-butane (iC₄) = 0–297; n-butane (nC₄) = 2–116; i-pentane (iC₅) = 0–31 and n-pentane (nC₅) = 0–23, respectively.Fifteen samples with high concentrations of alkane gases were measured for their δ¹³C₁; δ¹³C₂ and δ¹³C₃ compositions using gas chromatography–combustion-isotope ratio mass spectrometry (GC–C-IRMS). The values for methane varied from ? 27 to ? 45.4‰, ethane from ? 20.9 to ? 27.6‰, and propane from ? 20.4 to ? 29.1‰ versus the Vienna PeeDee Belemnite (VPDB). The carbon isotope ratio distribution pattern represents isotopic characteristics pertaining to hydrocarbon gases derived from thermogenic sources. Comparisons of carbon isotopic signatures and compositional variations with the standard carbon isotopic models suggest that hydrocarbon gases found in the shallow depths of the study area are not of bacterial origin but are formed thermally from deeply buried organic matter, likely to be mainly a terrestrial source rock with a partial contribution from a marine source. These gases may have migrated to the near-surface environment, where they represent an admixture of thermally generated hydrocarbon gases from mixed sources and maturity. The maturity scale (δ¹³C versus Log Ro %) applied to the surface sediment samples of the Jamnagar area indicated the source material to be capable of generating oil and gas. The detection of thermogenic alkane gases in near-surface sediments offers the possibility of hydrocarbons at depth in Saurashtra.  相似文献   

Soil Iodine Determination in Deccan Syneclise,India: Implications for Near Surface Geochemical Hydrocarbon Prospecting     

Devleena Mani  T. Satish Kumar  M. A. Rasheed  D. J. Patil  A. M. Dayal  T. Gnaneshwar Rao  V. Balaram 《Natural Resources Research》2011,20(1):75-88

The association of iodine with organic matter in sedimentary basins is well documented. High iodine concentration in soils overlying oil and gas fields and areas with hydrocarbon microseepage has been observed and used as a geochemical exploratory tool for hydrocarbons in a few studies. In this study, we measure iodine concentration in soil samples collected from parts of Deccan Syneclise in the west central India to investigate its potential application as a geochemical indicator for hydrocarbons. The Deccan Syneclise consists of rifted depositional sites with Gondwana–Mesozoic sediments up to 3.5 km concealed under the Deccan Traps and is considered prospective for hydrocarbons. The concentration of iodine in soil samples is determined using ICP-MS and the values range between 1.1 and 19.3 ppm. High iodine values are characteristic of the northern part of the sampled region. The total organic carbon (TOC) content of the soil samples range between 0.1 and 1.3%. The TOC correlates poorly with the soil iodine (r ² < 1), indicating a lack of association of iodine with the surficial organic matter and the possibility of interaction between the seeping hydrocarbons and soil iodine. Further, the distribution pattern of iodine compares well with two surface geochemical indicators: the adsorbed light gaseous hydrocarbons (methane through butane) and the propane-oxidizing bacterial populations in the soil. The integration of geochemical observations show the occurrence of elevated values in the northern part of the study area, which is also coincident with the presence of exposed dyke swarms that probably serve as conduits for hydrocarbon microseepage. The corroboration of iodine with existing geological, geophysical, and geochemical data suggests its efficacy as one of the potential tool in surface geochemical exploration of hydrocarbons. Our study supports Deccan Syneclise to be promising in terms of its hydrocarbon prospects.  相似文献   

Estimation of Snow Cover Area,Snow Physical Properties and Glacier Classification in Parts of Western Himalayas Using C-Band SAR Data     

Praveen K. Thakur  S. P. Aggarwal  G. Arun  Sahil Sood  A. Senthil Kumar  Sneh Mani  D. P. Dobhal 《Journal of the Indian Society of Remote Sensing》2017,45(3):525-539

Snow physical properties, snow cover and glacier facies are important parameters which are used to quantify snowpack characteristics, glacier mass balance and seasonal snow and glacier melt. This study has been done using C-band synthetic aperture radar (SAR) data of Indian radar imaging satellite, radar imaging satellite-1 (RISAT)-1, to estimate the seasonal snow cover and retrieve snow physical properties (snow wetness and snow density), and glacier radar zones or facies classification in parts of North West Himalaya (NWH), India. Additional SAR data used are of Radarsat-2 (RS-2) satellite, which was used for glacier facies classification of Smudra Tapu glacier in Himachal Pradesh. RISAT-1 based snow cover area (SCA) mapping, snow wetness and snow density retrieval and glacier facies classification have been done for the first time in NWH region. SAR-based inversion models were used for finding out wet and dry snow dielectric constant, dry and wet SCA, snow wetness and snow density. RISAT-1 medium resolution scan-SAR mode (MRS) in HV polarization was used for first time in NWH for deriving time series of SCA maps in Beas and Bhagirathi river basins for years 2013–2014. The SAR-based inversion models were implemented separately for RISAT-1 quad pol. FRS2, for wet snow and dry snow permittivity retrieval. Masks for layover and shadow were considered in estimating final snow parameters. The overall accuracy in terms of R² value comes out to be 0.74 for snow wetness and 0.72 for snow density based on the limited ground truth data for subset area of Manali sub-basin of Beas River up to Manali for winter of 2014. Accuracy for SCA was estimated to be 95 % when compared with optical remote sensing based SCA maps with error of ±10 %. The time series data of RISAT-1 MRS and hybrid data in RH/RV mode based decompositions were also used for glacier radar zones classification for Gangotri and Samudra Tapu glaciers. The various glaciers radar zones or facies such as debris covered glacier ice, clean or bare glacier ice radar zone, percolation/refreeze radar zone and wet snow, ice wall etc., were identified. The accuracy of classified maps was estimated using ground truth data collected during 2013 and 2014 glacier field work to Samudra Tapu and Gangotri glaciers and overall accuracy was found to be in range of 82–90 %. This information of various glacier radar zones can be utilized in marking firn line of glaciers, which can be helpful for glacier mass balance studies.  相似文献   

Distribution function of comminution kinetics — Modelling and experimental study     

K. Viswanathan  B.P. Mani 《International Journal of Mineral Processing》1982,9(4):385-392

A mathematical model for distribution function is developed considering the distribution of the number of fractures that can occur in a particle. It is shown as a consequence of the model that selection and distribution functions are intimately related through a single parameter — expected number of fractures per unit original size. This parameter can be comparatively easily obtained from batch experiments and can later be used to simulate industrial-scale grinding mills. Predictions of the model are amply confirmed by preliminary experimental results and other published observations. A correlation is developed to predict the parameter of the model from known equipment and operating variables for the particles used in the present study.  相似文献   

Distribution of global and net radiation over the Indian Ocean and its environments     

Dir. Anna Mani  O. Chacko  V. Krishnamurthy  V. Desikan 《Theoretical and Applied Climatology》1967,15(1-2):82-98

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Optimum method of calculation of product distribution from a distributed fracture model     

K. Viswanathan  B.P. Mani 《International Journal of Mineral Processing》1983,11(2):155-162

The general assumption that the breakage distribution function is independent of time is critically reviewed. Though this assumption is shown to be generally valid for tumbling mills, introduction of the concept of time-dependent distribution functions is shown to reduce the number of steps required for the calculation of product distribution drastically. It is shown that the optimum time equivalent of a stage of calculation for tumbling mills is the maximum time up to which the parameter C of the model is proportional to time. Then the parameter C evaluated at this time should be used to obtain the distribution function. For attrition it is shown that the time equivalent of a stage equals the whole time of operation and hence the parameter C should be evaluated at the time corresponding to the residence time of particles in the system. A few empirical forms of distribution functions are also given which may be useful where the theoretical expression is not valid.  相似文献   

Remote sensing based sedimentation study of maithon reservoir     

Pankaj Mani  Biswajit Chakravorty 《Journal of the Indian Society of Remote Sensing》2007,35(1):117-120

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Agricultural management impacts on groundwater: simulations of existing and alternative management options in Peninsular India          下载免费PDF全文

Daniel R. Dourte  Sanjay Shukla  Dorota Z. Haman  M. Devender Reddy  M. Uma Devi  Adusumilli Mani 《水文研究》2014,28(19):5021-5033

Understanding the principal causes and possible solutions for groundwater depletion in India is important for its water security, especially as it relates to agriculture. A study was conducted in an agricultural watershed in Andhra Pradesh, India to assess the impacts on groundwater of current and alternative agricultural management. Hydrological simulations were used as follows: (1) to evaluate the recharge benefits of water‐harvesting tillage through a modified Soil and Water Assessment Tool (SWAT) model and (2) to predict the groundwater response to changing extent and irrigation management of rice growing areas. The Green–Ampt infiltration routine was modified in SWAT was modified to represent water‐harvesting tillage using maximum depression storage parameter. Water‐harvesting tillage in rainfed croplands was shown to increase basin‐scale groundwater recharge by 3% and decrease run‐off by 43% compared with existing conventional tillage. The groundwater balance (recharge minus irrigation withdrawals), negative 11 mm/year under existing management changed to positive (18–45 mm/year) when rice growing areas or irrigation depths were reduced. Groundwater balance was sensitive to changes in rice cropland management, meaning even small changes in rice cropland management had large impacts on groundwater availability. The modified SWAT was capable of representing tillage management of varying maximum depression storage, and tillage for water‐harvesting was shown to be a potentially important strategy for producers to enhance infiltration and groundwater recharge, especially in semi‐arid regions where rainfall may be becoming increasingly variable. This enhanced SWAT could be used to evaluate the landscape‐scale impacts of alternative tillage management in other regions that are working to develop strategies for reducing groundwater depletion. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Estimating economic effects of changes in climate and water availability     

Brian Hurd  Mani Rouhi-Rad 《Climatic change》2013,117(3):575-584

Social, economic, and environmental systems can be vulnerable to disruptions in water supplies that are likely to accompany future climate changes. Coupled with the challenges of tightening environmental regulations, population growth, economic development and fiscal constraints water supply systems are being pushed beyond the limits of their design and capacity for maintenance. In this paper we briefly review key economic concepts, various economic measures and metrics, and methods to estimate the economic effects on water resources from water supply changes that could accompany climate change. We survey some of the recent empirical literature that focuses on estimates developed for U.S. watersheds at both national and regional scales. Reported estimates of potential damage and loss associated with climate and water supply changes that we observe are significant, though often the metrics vary and make valid and consistent direct cross-comparisons difficult. Whether in terms of changes in GDP or in terms of estimated changes in economic welfare based on associated changes in economic costs and benefits, both national and regional estimates suggest that governments and organizations incorporate prudent steps to assess vulnerabilities to plausible future water supply and demand scenarios and develop responsive adaptation strategies.  相似文献