Experimental and Numerical Analyses of Tubular Electrohydraulic Forming Process

Electrohydraulic forming (EHF) is a kind of high speed forming process, which deforms the metal by shock wave through instantaneous discharge of high voltage in water. Compared with the traditional forming methods, this high speed forming process can greatly improve the formability of the materials. There are many processing factors that affect the forming efficiency and performance of the electrohydraulic forming process, one of which is the discharge voltage between the electrodes. In this paper, three electrohydraulic forming experiments with various die shapes were carried out under various discharge voltage conditions. And the bulge height and axial length of the aluminum alloy A6061 tubes under different conditions were compared. Besides, finite element numerical simulation was also performed to quantitatively investigate the deformation history of the tube.

Analysis of the Water Circulation Structure in the Paldang Reservoir, South Korea

In this study, results are presented for depth-specific hydraulic and water quality surveys, as well as meteorological observations, at key monitoring sites in the Paldang Reservoir, South Korea. These results were used to determine the water circulation characteristics that represent the main contributors to water quality changes. In the section before the confluence point of the two rivers, a different type of two-layer flow appeared for each. In the North Han River, backwater flowing backward in the upstream direction occurred in the surface layer, and was accompanied by two-layer flow, during the zero-discharge period of the Cheongpyeong Dam. On the other hand, in the South Han River, two-layer flow was observed in the upper layer in the downstream flow, and the thickness of upper and lower layers varied depending on the discharge rate of the Paldang Dam. Strong flow fluctuations were observed near the Paldang Dam (3 km upstream), and these were dependent on its instantaneous discharge rate. In particular, if the instantaneous discharge from the Paldang Dam remained below 400 m3/s for several days, the flow velocity in the lower layer decreased below 2 cm/s or no flow occurred. The comparison between flows during different periods associated with depth-specific water temperature variations showed that the average flow prevailed across all layers in the downstream direction at all monitoring sites during the vertical mixing period. In contrast, spatiotemporal variations in flow, such as two-layer flow and backwater, were observed during the stratification period in the South Han River and the North Han River. This led to increased residence times and vertical stability, thus creating favorable conditions for algal blooms.

What urban streamflow can tell us about changes in water storage and streamflow due to development

<p><span>The urbanization of a watershed radically impacts how watersheds store, transmit and discharge water. Although urbanization’s effects on floods, droughts, and water supply have been explored in recent decades through land-use modeling, hydrological modeling, remote sensing, and empirical approaches, clarification of these effects remains a challenge due to limited availability and accessibility of useful data. Streamflow records for three neighboring watersheds in Baltimore, an urbanized watershed, an urbanizing watershed and a natural watershed, provide a unique opportunity to study the influence of urbanization on watershed function.  The 5-minute instantaneous discharge records span an increase in residential development of the urbanizing watershed.  Coupling the streamflow and development records allows direct comparison of hydrologic changes with spatial patterns of land use change.  Recession analysis was used to evaluate altered hydrologic response, particularly relationships between watershed storage and streamflow that may occur during urbanization.  Recession approaches were applied using variable time steps to estimate the time derivative of streamflow (dQ/dt) to avoid known issues in parameter estimation driven by the time derivative of a noisy time series. Several hypotheses are tested, including comparisons to conceptual models of hydrologic change that would be expected in urbanizing watersheds.  Preliminary results suggest that hydrologic changes are notable during periods of intense development, with recession plot characteristics markedly variable in urbanizing and urban watersheds as compared to the natural watershed. Analysis of streamflow records during the process of urbanization reveals groundwater-surface water interactions driven by urban development previously only observed over relatively shorter time periods. These findings can inform implementation of sustainable design of storm water management and future development planning. </span></p>

Analysis of Water Availability in Omu Watershed

The availability of water in the Omu watershed becomes an important factor for residents in carrying out their activities, very it is important to know the available discharge and water requirements. This study aims to determine the amount of water availability in the Omu watershed based on the method FJ. MOCK, NRECA, and SMEC. This research uses average monthly rainfall data of Tuva station, average monthly climatology data of Bora station, data of catchment area, and land use. The result of the calculation of Omu watershed water availability by using the method of FJ. MOCK, NRECA, and SMEC; obtained the average discharge 2. 21 m3/sec, 2. 30 m3/sec, 2. 85 m3/sec, the maximum discharge happened in June 2. 36 m3/sec, in March 3. 63 m3/sec, in June 3. 58 m3/sec, and while the minimum discharge happened in July 1. 72 m3/sec, in January 0. 84 m3/sec, in February 2. 12 m3/sec. The result of instantaneous discharge measurement in the field is 2. 18 m3/sec. Based on the comparison of the results of the analysis of the water availability data on the Omu watershed, from the three methods closest to the instantaneous discharge value is the FJ. MOCK method.

Hydrogeomorphic Characteristics of Urban Flood Triggers in Gombe Town, Nigeria as Monitored in 2014

Urban flooding has become a monumental yearly disaster in many of the world’s cities and Gombe town in particular. This paper focused on some hydro-geomorphological characteristics that influence flooding in Gombe town. Statistical methods and geographic information techniques were used for the assessment. The result revealed that the highest API of 166.62 mm occurred on the 5/9/2014. The rainfall amount was 92.5mm for a duration 48 minutes, average rainfall intensity was 115.63, stage height (1.42m), average flow velocity (0.98m/s), and instantaneous discharge of 9.47m3 /s. This corresponds with the flood disaster that occurred in Gombe town on the same date (5/9/2014). On the other hand, the least API of 18.12 mm occurred on the 18/6/2014. The rainfall amount was 1.2mm for 62 minutes, average rainfall intensity was 1.16, stage height (0.30m), average flow velocity (0.24m/s), and instantaneous discharge of 0.49m3 /s. findings also showed that very steep slope covered 2.4537km2 (1.78%), steep slope covered 3.60235km2 (2.61%), moderate slope (0.735574km2 or 0.53%), gentle slope (131.106km2 or 94.89%) and flat areas (0.259854km2 or 0.19%). The study recommended flood resilience technology, provision of adequate urban drainages and proper storm water management.Keywords: Drainage density, flow accumulation, rainfall, urban flooding

RECENT TRENDS Of RIVER RUNOff IN THE NORTH CAUCASUS

Based on observational data from 70 hydrological stations in the North Caucasus an evaluation of present values of mean annual runoff, minimum monthly winter and summer runoff was carried out. Series of maps was drawn. Significant changes in mean annual. minimum monthly and maximum runoff during last decades have been revealed in the North Caucasus. A rise in both amount of water availability and potential natural hazard is characteristic of the most of the North Caucasus that is considered to be caused by recent climate change. Mean annual runoff during 1978-2010 increased compared to 1945-1977 by 5-30 % in the foothills and by 30-70% in the plain area. An increase in winter minimum monthly runoff is as well most intensive in the plain part of study area (>100%). Within the foothills it amounts to 50-100%. In mountainous area long-term oscillation of winter minimum monthly discharge strongly depends on local factors, such as geological structure. The rate of the increase in summer minimum monthly discharge regularly grows from central foothill part of Northern Caucasus (30-50%) to the Western plain territory (70-100%). In Kuban river basin 30% of analyzed gauging stations show positive trend in maximum instantaneous discharge, while 9% negative. On the contrary, in the Eastern part – Terek river basin – negative trend in maximum instantaneous discharge is prevalent: 38% of gauging stations. Positive trend in Terek river basin is characteristic of 9.5% of analyzed gauging stations.

Ultrahigh energy storage density and instantaneous discharge power density in BaO–PbO–Na2O–Nb2O5–SiO2–Al2O3 glass-ceramics

An ultrahigh energy storage density Es of 20.7 J cm−3 and a maximum instantaneous power density of 78.2 MW cm−3 were obtained in BPNN-AS glass-ceramics.

A theoretical analysis of river bars stability under changing channel width

In this paper we propose a new theoretical model to investigate the influence of temporal changes in channel width on river bar stability. This is achieved by performing a nonlinear stability analysis, which includes temporal width variations as a small-amplitude perturbation of the basic flow. In order to quantify width variability, channel width is related with the instantaneous discharge using existing empirical formulae proposed for channels with cohesionless banks. Therefore, width can vary (increase and/or decrease) either because it adapts to the temporally varying discharge or, if discharge is constant, through a relaxation relation describing widening of an initially overnarrow channel towards the equilibrium width. Unsteadiness related with changes in channel width is found to directly affect the instantaneous bar growth rate, depending on the conditions under which the widening process occurs. The governing mathematical system is solved by means of a two-parameters (ε, δ) perturbation expansion, where ε is related to bar amplitude and δ to the temporal width variability. In general width unsteadiness is predicted to play a destabilizing role on free bar stability, namely during the peak stage of a flood event in a laterally unconfined channel and invariably for overnarrow channels fed with steady discharge. In this latter case, width unsteadiness tends to shorten the most unstable bar wavelength compared to the case with constant width, in qualitative agreement with existing experimental observations.

Development of a Power Supply for the Food Processing Device, Using High Pressure due to Evaporation of Aluminum Wire by Discharging High Current

We have developed the food processing device which uses underwater shock waves generated by gap discharging and electrical sparking. This method is dangerous due to the fact that it requires a very high voltage. Thus, we have focused on evaporation of aluminum wires occurred by the instantaneous high current and low voltage from a charged capacitor. When instantaneous high current flows through the aluminum wire is anchored between electrodes, a shock wave is generated by the evaporation of the aluminum wire. In this research, we have developed a power supply module for the food processing device using high pressure of shock wave due to evaporation of aluminum wire by instantaneous discharge of high current. In the present stage, the evaporation of aluminum wire can generate 70% of pressure compared to the gap discharge, and as for the electric power, it reached 22.5% of the gap discharge. It has been understood that the number of the aluminum wires are important to obtain a high pressure, when the charged capacitor discharged the charge. We found that evaporation of aluminum wire can generate high pressure with low voltage, which is more effective than the gap discharging in terms of safety.