Modelling of tidal hydrodynamics for a tropical ecosystem with implications for pollutant dispersion (Cohin Estuary, Southwest India)   总被引：1，自引：0，他引：1  

Kizhakkepat Kalathil Balachandran  Guddemmari Sidha Reddy  Chenicherry Revichandran  Kotamarpi Srinivas  Panachikkal Ramakrishnan Vijayan  Tony Joseph Thottam 《Ocean Dynamics》2008,58(3-4):259-273

Tidal circulation in the Cochin Estuary, a moderately polluted estuary along the southwest coast of India, was studied using a 2D hydrodynamic model. The predicted tides and currents showed very good agreement with measured tides. Particle trajectories and residual currents computed from the model have been used to classify the study region into three zones: northern estuary, central estuary, and southern estuary. The central estuary is dynamic, whereas the other two zones are relatively weak. An amplification of measured tides in the south estuary during March indicates the presence of standing waves caused by the hydraulic barrier at Thanneermukkom. Model results suggest that the northern and southern zones are sensitive to environmental pollution. The present level of pollution in the northern estuary is due to the direct release of industrial effluents into the river Periyar, which can be minimized if they are brought down to central estuary for disposal. The concept of different zones in the estuary will be useful to planners in protecting the vulnerable regions of this productive ecosystem from human interventions.  相似文献   

Numerical simulation of tropical cyclone thane: role of boundary layer and surface drag parameterization schemes     

M. Sateesh  C. V. Srinivas  P. V. S. Raju 《Natural Hazards》2017,89(3):1255-1271

In the recent times, several advanced numerical models are utilized for the prediction of the intensity, track and landfall time of a cyclone. Still there are number of issues concerning their prediction and the limitation of numerical models in addressing those issues. The most pertinent question is how intensive a cyclone can become before it makes a landfall and where the cyclone moves under the ambient large-scale flow. In this paper, detailed study has been carried out using Weather Research Forecast model with two boundary schemes to address the above question by considering a recent tropical cyclone in Bay of Bengal region of North Indian Ocean. In addition, the impact of the surface drag effect on the low-level winds and the intensity of the cyclone are also studied. The result reveals that large differences are noted in the ocean surface fluxes between YSU and MYJ with MYJ producing relatively higher fluxes than YSU. It is found that the YSU scheme produced a better simulation for the THANE cyclone in terms of winds, pressure distribution and cloud fractions. Comparison with available observations indicated the characteristics of horizontal divergence, vorticity and vector track positions produced by YSU experiment are more realistic than with MYJ and other experiments. However, when the drag coefficient is changed as 0.5 or 2.0 from the default values, appreciable changes in the surface fluxes are not noticed. A maximum precipitation is reported in YSU as compared to the MYJ PBL scheme for the tropical cyclone THANE.  相似文献   

Easy to Use Empirical Correlations for Liquefaction and No Liquefaction Conditions     

Abhishek Kumar  B. Vivek Srinivas 《Geotechnical and Geological Engineering》2017,35(4):1383-1407

Considerable damages during an earthquake (EQ) are the consequence of in situ soil losing its shear strength which is popularly known as liquefaction. A number of methodologies are available to quantify the safety of a site against liquefaction occurrence. Widely accepted recent methodologies follow iterative process making it cumbersome for the field engineer. In the present work, empirical correlations are proposed in accordance with widely accepted methodology, analysing the effect of various parameters such as overburden pressure, fines content (FC), factor of safety (FOS) etc. These proposed correlations are easy to use for the designers and the field engineers to determine the liquefaction potential of a site. Considering data from 207 global sites, proposed correlations are validated by comparing with standard methodology. Three different graphical validations are presented supporting that the results based on the proposed correlations are closely matching with the standard methodology. In case a site is found susceptible to liquefaction, so far no correlations are available to determine the shear strength required to be achieved after ground improvement which will ensure no liquefaction during future EQ. Proposed correlations in this work can also be used easily to determine improved shear strength required for a known FOS, FC and EQ magnitude (M) from ground improvement. Two flowcharts explaining the use of proposed correlations to determine FOS of a site and improvement shear strength required for a liquefied site from ground improvement respectively are developed in this work. Based on the second flowchart, determination of shear strength required from ground improvement are done for 45 random sites out of 207 liquefied sites during worldwide EQ in this work.  相似文献   

Numerical Simulation of Explosion in Twin Tunnel System     

A. K. Verma  Manish Kumar Jha  Srinivas Mantrala  T. G. Sitharam 《Geotechnical and Geological Engineering》2017,35(5):1953-1966

Rapid growth of urban population in Indian cities have led traffic congestion leading to demand for scientific utilization of underground space. Immediate underground level and deep level underground below the major arterial roads are the sustainable spaces available for meeting the demand of the future traffic/transport. Due to recent increased transit activities it has become one of the soft targets by terrorists or prone to catastrophic accidents in recent years which have increased the importance of rock structures study under explosive loading. In this paper, the response of a underground metro tunnel subjected dynamic loads have been investigated including explosive capacity (30 kg TNT), ground characteristics, liner thickness and blast pressure characteristics. Blast pressure representing CONWEP air blast loading model with positive over pressure phase was applied to lining of tunnel. A three dimensional explicit finite element method was used to analyze dynamic response and damage in twin tunnels of underground metro. It is found that liner of thickness 28 cm will start deforming at the explosive loading of more than 65 kg TNT.  相似文献   

Use of multidate Landsat data in evaluating the Surface water availability as an indicator of drought condition     

P. Srinivas 《Journal of the Indian Society of Remote Sensing》1989,17(1):17-22

An attempt has been made to monitor the Seasonal Variations of Surface water by relating the Satellite derived waterspread information to the weekly rainfall data in the monsoon periods of 1984 in the chittor district of Andhra Pradesh. Further the study has indicated that there is a significant deficit in the area of Crops Irrigated by tanks on account of deficit in surface water availability, thereby indicating the general drought situation in the year 1984.  相似文献   

Analysis of the Deformation of Homogeneous Electrical Fields Over Some Two-Dimensional Structures     

M. Srinivas  N. Sundararajan 《Ground water》1996,34(4):588-592

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Studies on the behaviour of axially loaded tapered piles by the finite element method     

Nainan P. Kurian  Moola S. Srinivas 《国际地质力学数值与分析法杂志》1995,19(12):869-888

Tapered piles represent a more equitable distribution of the pile material in several respects. In order to study their efficiency over piles of uniform section with the same material input, a three-dimensional finite element analysis is developed. The numerical procedure accounts for the non-linear elastic behaviour of both the soil and the pile-soil interface. In order to include the latter, which involves relative slip and debonding, zero/non-zero thickness interface elements are used. Three shapes of cross-section, viz. circular, square and triangular, have been attempted for the piles. The load-settlement behaviour under axial load predicted by the analysis is compared with laboratory test results obtained on instrumented model piles, installed as ‘replacement’ piles, and the fit obtained is found to be reasonably good. Also examined are interface shear and axial force in the pile, displacement and stress fields in the medium and the progression of failure in the latter.  相似文献   

A numerical study of sea breeze circulation observed at a tropical site Kalpakkam on the east coast of India, under different synoptic flow situations     

C. V. Srinivas  R. Venkatesan  K. M. Somayaji  A. Bagavath Singh 《Journal of Earth System Science》2006,115(5):557-574

A simulation study of the sea breeze circulation and thermal internal boundary layer (TIBL) characteristics has been carried out at the tropical site Kalpakkam on the east coast of India, for operational atmospheric dispersion prediction. The community based PSU/NCAR MM5 Meso-scale meteorological model is used for the study. Three cases on typical days in summer (24 May 2003), southwest (SW) monsoon (1 July 2001) winter season (2 February 2003) with different large-scale flow pattern are studied. The MM5 model is used with 3 nested domains with horizontal grid resolutions 18 km, 6 km and 2 km and 26 vertical levels. The model is integrated for 24 hours in the above cases with initial and boundary conditions taken from NCEP-FNL analyses data. Observations of 10 meteorological stations and coastal boundary layer experiments conducted at Kalpakkam are used for comparison and validation of the simulation. The characteristics of simulated sea breeze and TIBL at Kalpakkam are seen to vary in the above cases according to the prevailing large-scale winds and surface fluxes. The sea breeze circulation is seen to develop early with larger strength and inland propagation in the summer case under the influence of moderate synoptic wind and strong heating conditions than in the SW monsoon and winter cases. The horizontal and vertical extents of TIBL are found to be larger in the summer case than in other cases. Although model parameters agree in general with observations, all the fine features are not clearly captured and some slowness in model sea breeze development is also seen. The results indicate the need to improve i) the initial conditions by assimilation of available surface/upper air observations to reduce model bias and ii) surface net radiation parameterisation. The model could predict the essential features of the local circulation and further improvement is expected with better initial condition data and incorporation of more realistic surface data.  相似文献   

Delineation of Fractures through Acoustic Televiewer Log     

K. N. S. S. S. Srinivas  M. Srihari Rao  P. Pavan Kishore  D. Gopinadh  Haris Raza  Kusumita Arora  H. V. S. Satyanarayana 《Journal of the Geological Society of India》2018,91(5):569-574

Boreholes are the only sources for direct measurements of geological and geophysical characteristics of the shallow subsurface of the earth. Borehole imaging tool “Acoustic Televiewer (ATV)” is an advanced probe, which records 3D image of the bore hole wall and is used to obtain oriented images of bore hole and provides substantial information regarding lithology, structural information, detection of fractures and casing of the borehole. The images are highly sensitive to the presence of fractures, the delineation of which becomes accurate and reliable based on these acoustic images. Features identified on log-derived images can be correlated with core samples or can be used as substitute in the poor core recovery zones. In the present study, ATV log from a deep borehole drilled at Khadi Kolavan in Koyna-Warna region of Ratnagiri district, Maharashtra located west of the Western Ghat escarpment in the Deccan Volcanic province, India, is used for interpretation of structural characteristics of the formation. The same was correlated with other conventional logging methods such as resistivity and full waveform sonic (FWS) as well as core logging and rock quality designations (RQD) which generated new understanding of the basement and basalt cover in this region.  相似文献   

Tropospheric biennial oscillation and south Asian summer monsoon rainfall in a coupled model     

Gopinadh Konda  J S Chowdary  G Srinivas  C Gnanaseelan  Anant Parekh  Raju Attada  S S V S Rama Krishna 《Journal of Earth System Science》2018,127(4):46

In this study Tropospheric Biennial Oscillation (TBO) and south Asian summer monsoon rainfall are examined in the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFSv2) hindcast. High correlation between the observations and model TBO index suggests that the model is able to capture most of the TBO years. Spatial patterns of rainfall anomalies associated with positive TBO over the south Asian region are better represented in the model as in the observations. However, the model predicted rainfall anomaly patterns associated with negative TBO years are improper and magnitudes are underestimated compared to the observations. It is noted that positive (negative) TBO is associated with La Niña (El Niño) like Sea surface temperature (SST) anomalies in the model. This leads to the fact that model TBO is El Niño-Southern Oscillation (ENSO) driven, while in the observations Indian Ocean Dipole (IOD) also plays a role in the negative TBO phase. Detailed analysis suggests that the negative TBO rainfall anomaly pattern in the model is highly influenced by improper teleconnections allied to IOD. Unlike in the observations, rainfall anomalies over the south Asian region are anti-correlated with IOD index in CFSv2. Further, summer monsoon rainfall over south Asian region is highly correlated with IOD western pole than eastern pole in CFSv2 in contrast to the observations. Altogether, the present study highlights the importance of improving Indian Ocean SST teleconnections to south Asian summer rainfall in the model by enhancing the predictability of TBO. This in turn would improve monsoon rainfall prediction skill of the model.  相似文献