Use of breakdown coefficients in turbulent jets to determine the universal exponent μ

Second-order moments of the breakdown coefficients q _r,l of the squared velocity derivative in plane and circular jets indicate a value of the exponent which is larger than that obtained by other methods using the same data or that previously reported by other workers using the same method on atmospheric data. The difference may be due to a failure of the present data to satisfy the first condition of scale similarity, possibly because of the relatively small Reynolds numbers of the laboratory flows. The dependence of the variance of ln q _r,l on the length scale l appears to be independent of Reynolds number.     

Simulation of vortex-induced vibrations of a cylinder using ANSYS CFX

In this paper, vortex-induced vibrations of a cylinder are simulated by use of ANSYS CFX simulation code. The cylinder is treated as a rigid body and transverse displacements are obtained by use of a one degree of freedom spring damper system. 2-D as well as 3-D analysis is performed using air as the fluid. Reynolds number is varied from 40 to 16000 approx., covering the laminar and turbulent regimes of flow. The experimental results of （Khalak and Williamson, 1997） and other researchers are used for validation purposes. The results obtained are comparable.     

Ostracoda as an aid in identifying 2004 tsunami sediments: a report from SE coast of India

Four short core samples were collected from the creek, estuarine regions of southeast (SE) coast of India affected by the 2004 Asian Tsunami. The study is aimed to signify the importance of ostracoda species in identifying major natural events (e.g. Tsunamis) in the coastal regions. The presence of many marine ostracoda species in the beach areas and the comparative studies with earlier reports from SE coast indicate that these species were brought by the high-energy tsunami waves. The depositional feature of ostracoda species in the beach and estuarine region also infers on the nature and force of tsunami waves in a particular region. The results clearly support that microfossils can be used to identify the major natural events close to coastal regions.     

Recharge processes: piston flow vs preferential flow in semi-arid aquifers of India

Study of groundwater recharge processes is vital for quantification of total natural recharge to the aquifers. One of the recharge processes demonstrated earlier by tracer experiments in the unsaturated zone is that of piston flow movement of soil moisture. Based on this recharge process, environmental tritium, chloride and injected tritium studies have been carried out extensively in various geological environs of India. The purpose of this paper is to evaluate the validity of the piston flow concept in different geological environs viz. consolidated fractured and weathered granites, semi-consolidated sandstones and unconsolidated alluvial tracts, and quantify the contribution from this process as well as that from the preferential flow mechanism using different tracers. Analysis of tracer data demonstrates that the preferential flow recharge process contributes very significantly (an average of 75% of total recharge) in the case of fractured granites and is important (an average of 33% of total recharge) for semi-consolidated sandstones, whereas the preferential flow recharge component is minimal in unconsolidated alluvial tracts (piston flow model is applicable). These findings necessitate re-evaluation of the total natural recharge potential of the above mentioned geological environs in view of the significant preferential flow recharge that is evidenced and estimated. Electronic Publication     

Stable isotope dynamics of groundwater interactions with Ganges river

Groundwater depletion has been an emerging crisis in recent years, especially in highly urbanized areas as a result of unregulated exploitation, thus leaving behind an insufficient volume of usable freshwater. Presently Ganges river basin, the sixth largest prolific fluvial system and sustaining a huge population in South Asia, is witnessed to face (i) aquifer vulnerability through surface waterborne pollutant and (ii) groundwater stress due to summer drying of river as a result of indiscriminate groundwater abstraction. The present study focuses on a detailed sub-hourly to seasonally varying interaction study and flux quantification between river Ganges and groundwater in the Indian subcontinent which is one of the first documentations done on a drying perennial river system that feeds an enormous population. Contributing parameters to the total discharge of a river at its middle course on both temporal and spatial scale is estimated through three-component hydrograph separation and end-member mixing analysis using high-resolution water isotope (δ¹⁸O and δ²H) and electrical conductivity data. Results from this model report groundwater discharge in river to be the highest in pre-monsoon, that is, 30%, whereas, during post-monsoon the contribution lowers to 25%; on the contrary, during peak monsoon, the flow direction reverses thus recharging the groundwater which is also justified using annual piezometric hydrographs of both river water and groundwater. River water-groundwater interaction also shows quantitative variability depending on river morphometry. The current study also provides insight on aquifer vulnerability as a result of pollutant mixing through interaction and plausible attempts towards groundwater management. The present study is one of the first in South Asian countries that provides temporally and spatially variable detailed quantification of baseflow and estimates contributing parameters to the river for a drying mega fluvial system.     

The Use Of Environmental Isotopes And Chloride As Natural Tracers To Investigate The Effects Of Depressurisation Of A Coastal Aquifer For Lignite Mining,India

In order to mine lignite from the Neyveli opencast mines, about 200 km south of Madras, India, the Neyveli aquifer has been undergoing depressurisation continuously for almost three decades. To gain insight into the aquifer hydrodynamics, environmental-isotope and chloride measurements on selected groundwater samples were initiated two decades ago, and detailed studies were undertaken during 1985–91. This article demonstrates the effect of large-scale groundwater withdrawals on the hydrologic regime and the effects on environmental chloride and isotopic distributions. A feature common to both the radiocarbon and chloride data of 1991 is their marked variation in a small area between the recharge zone and the mine area where pumping is concentrated. Furthermore, an excellent correlation exists between the temporal increase in the apparent radiocarbon ages of groundwater sampled in 1991 and 1985 and the corresponding lowering of potentiometric levels. Isochlors based on 1991 and 1985 data also indicate a changed hydrologic regime. In certain areas, heavy withdrawals have resulted in increased groundwater salinity.     

Palaeomagnetism of the basalts of Wadi Abu Tereifiya, Mandisha and dioritic dykes of Wadi Abu Shihat, Egypt

Summary. One hundred and fifty oriented samples were collected from 12 sites from the Tertiary basalts of Wadi Abu Tereifiya (30.0°N, 32.1° E). After alternating field demagnetization the mean direction of the natural remanent magnetization is, D = 187.9°, I = -20.8° with α₉₅= 5.8°. This yields a palaeopole at 69.4°N, 188.3° E.
Also, 30 oriented samples were collected from two sites from Mandisha in Bahariya Oasis (28.4°N, 28.9° E). After cleaning, the mean direction of the NRM is D = 191.0°, I = 5.2° with α₉₅= 9.9°. This yields a palaeopole position at 58.2°N, 186.7° E.
Besides, the NRM of 70 oriented samples collected from seven dioritic dykes from Wadi Abu Shihat (26.3°N, 33.2° E) was found to have a mean direction, D = 142.0°, I = -0.3°, which leads to a palaeopole position at, 44.9°N, 273.0° E. This agrees with other Mesozoic pole positions from Africa.