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Time-averaged Turbulent Flow Characteristics over a Highly Spatially Heterogeneous Gravel-Bed

100%

Sarkar S.

tom Vol. 64, no. 5

1797--1824

The present study focuses on the time-averaged turbulence characteristics over a highly spatially-heterogeneous gravel-bed. The timeaveraged streamwise velocity, Reynolds shear and normal stresses, turbulent kinetic energy, higher-order moments of velocity fluctuations, length scales, and the turbulent bursting were measured over a gravel-bed with an array of larger gravels. It was observed that the turbulence characteristics do not vary significantly above the crest level of the array as compared to those below the array. The nondimensional streamwise velocity decreases considerably with a decrease in depth below the array. Below the array, the Reynolds shear stress (RSS) deviates from the gravity-law of RSS distributions. Turbulence intensities reduce below the crest level of the gravel-bed. The third-order moments of velocity fluctuations increase below the crest level of the gravel-bed and give a clear indication of sweeps as the predominating event which were further verified with the quadrant analysis plots. The turbulent length scales values change significantly below the crest level of the gravel-bed.

Estimating crop water requirements and assessing irrigation water distribution cost for rice production using a pipe network

63%

Gautam N. K. , Sarkar S.

nr 3

In this paper we attempted to estimate crop water requirement for rice production in an Indian state. We also assessed the cost of irrigation water distribution. The study area (phases I and II) belongs to a humid subtropical region with sandy clay loam soil. Here, farmers are presently using a partial border strip irrigation technique with supply pipe and riser. First, the Man Kendall test is performed on six years monthly rainfall data to check for the presence of a trend. We found that the data is random at a 5% significant level. Thereafter, the crop water requirement for rice production is calculated based on FAO guidelines and average monthly rainfall. The crop water requirement in the study area amounted to 7.22 lakh m³, of which Phase I is 6.12 lakh m³ and Phase II is 1.2 lakh m³. In order to fulfil this requirement, irrigation was conducted through a pipe network. Actual irrigation value is calculated based on four years of irrigation water distribution data. Finally, the average depth of water logging, time of pumping, and cost for surplus irrigated water are calculated. We found that at a rate of INR 5 per unit kWh, the cost of annual surplus irrigated water for rice is 4.32 lakhs for an irrigation area of 1.284 km² (phase I), and the same is INR 0.84 lakh for 0.252 km² (phase II). This loss can be minimized using proper scheduled regulation of irrigated water using the pipe distribution network.

Effects of Hall current on unsteady hydromagnetic free convection flow past an impulsively moving vertical plate with Newtonian heating

51%

Seth G. S. , Sarkar S. , Sharma R.

tom Vol. 21, no. 1

187--203

An investigation of unsteady hydromagnetic free convection flow of a viscous, incompressible and electrically conducting fluid past an impulsively moving vertical plate with Newtonian surface heating embedded in a porous medium taking into account the effects of Hall current is carried out. The governing partial differential equations are first subjected to the Laplace transformation and then inverted numerically using INVLAP routine of Matlab. The governing partial differential equations are also solved numerically by the Crank-Nicolson implicit finite difference scheme and a comparison has been provided between the two solutions. The numerical solutions for velocity and temperature are plotted graphically whereas the numerical results of skin friction and the Nusselt number are presented in tabular form for various parameters of interest. The present solution in special case is compared with a previously obtained solution and is found to be in excellent agreement.

Roles of thyroid, adrenal and pancreatic hormones on thyroid activity of the soft-shelled turtles Lissemys punctata punctata Bonnoterre

45%

Ray P. P. , Sarkar S. , Sengupta A. , Chaudhuri-Sengupta S. , Maiti B. R.

nr 3-4