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Author(s):  
Hong-xiang Zheng ◽  
Yun Luo ◽  
Jing-Yu Zang ◽  
Qian Zhang

Abstract Water jet peening can effectively improve the fatigue strength of metal materials, and the outlet shape of nozzle greatly affects the effect of water jet peening. In this paper, the effects of nozzle outlet shape on water jet velocity and impact pressure is studied by numerical simulation, and the jet velocity and dynamic pressure for different standoff distances are also discussed. The results show that the water jets of square, circular and triangular nozzles are highly concentrated, and the water jet of elliptical nozzles is the most divergent. The axial velocity attenuation of the square nozzle along the axis is slower than that of the other three nozzles. The water axial velocity of the elliptical nozzle attenuates fastest and the length of the core segment of the water jet is the smallest. Within a certain axial distance, the dynamic pressure area in the central area of the elliptical water jet is obviously larger than that of the other three nozzles, and the effective treatment range is large, which is more suitable for the welding surface strengthening operation.


2022 ◽  
Vol 10 (1) ◽  
pp. 70
Author(s):  
Yibing Zhao ◽  
Canjun Yang ◽  
Yanhu Chen ◽  
Jia Li ◽  
Siyue Liu ◽  
...  

In order to adhere to the wall stably in an underwater environment, a vortex suction cup that injects high-pressure water inside via two axisymmetrically side-distributed inlets to create a negative pressure area in the center is the necessary component for the underwater climbing robot (UCR). However, the suction force of this vortex suction cup is reduced and periodically unstable due to unstable cavitation. The aim of this paper is to propose a cavitation reduction optimization method for vortex suction cups and to verify the effectiveness of the optimization. Analyses of this vortex flow, including streamlines, pressure, and cavitation number fluctuations, were carried out by the introduced computational fluid dynamics (CFD) simulating methods based on the multiphase RNG k−ε model to study the periodic fluctuations of the suction force of the original suction cup and the optimized ones. Force measurement and vortex observation experiments were conducted to compare the suction force of the original vortex suction cup and the optimized suction cup, as well as the cavitation and pressure fluctuation phenomenon. Results of simulation and experiments prove the existence of the effect of vortex cavitation on the suction performance and verify the rationality of optimization as well.


2021 ◽  
Author(s):  
jianjun SHI ◽  
Feng Jicheng ◽  
Peng Rui ◽  
Zhu Quanjie

Abstract The gob-side entry driving is driving in low pressure area, which bears less support pressure and is easy to maintain, so it is widely used. Taking the gob-side entry driving in thick coal seam of Dongtan Coal Mine as an example, the reasonable size of pillar and the section of roadway are numerically simulated by combining numerical with measurement, and the roadway support is designed. According to the distribution of lateral stress in working face, eight pillars of different sizes are designed. By simulating and comparing the stress distribution of surrounding rock and the development range and shape of plastic zone in different positions, the pillar size of gob-side entry driving is optimized to be 4.5m. According to the results of optimization of roadway section, the section of straight wall semi-circular arch roadway is adopted. According to the analysis, the roadway is supported by bolt + steel mesh + anchor cable. By observing the stability of roadway, it provides experience for the stability study of roadway the gob-side entry driving with small pillar in thick seam.


2021 ◽  
Vol 14 (1) ◽  
pp. 241
Author(s):  
Yang Wang ◽  
Xue Li ◽  
Jiyu Li ◽  
Jipeng Xu

Herein, a finite discrete element method was used to simulate the rockburst phenomenon of elliptical caverns with different axis ratios. Two situations were employed, namely when the disturbance direction is perpendicular and parallel to the ellipse. Based on the peak stress, maximum velocity, stress nephogram, and image fractal characteristics, the influence of axis ratio and direction of the disturbance on rockburst were analyzed. The results show that the samples with different axis ratios experienced the same process of quiet period, slab cracking period, and rockburst. The rockburst pit had V shape, and the failure modes of rockburst primarily included shear cracks, horizontal tension cracks, and vertical tension cracks. With the rise in axis ratio, the peak stress and maximum speed increased. Furthermore, the pressure area on the left and right sides of the sample cavern decreased when the disturbance direction was parallel to the short axis of the ellipse, while it increased for the sample with a disturbance direction perpendicular to the short axis. The fractal dimension value of the crack was gradually amplified with disturbance. The fractal dimension value of the sample whose disturbance direction was perpendicular to the minor axis of the ellipse was lower, and it was more difficult to damage.


MAUSAM ◽  
2021 ◽  
Vol 63 (2) ◽  
pp. 223-230
Author(s):  
B. PUTTANNA ◽  
GEETA AGNIHOTRI

Karnataka a State in south peninsular India receives 73% of its annual rainfall during southwestmonsoon season. Because of the complex physiographical features, the rainfall pattern over the State shows large spatialvariation from 50 to 350 cms. The coefficient of interannual variation of the monsoon rainfall is about 15% over coastalKarnataka (CK) and between 20-30% over interior Karnataka. The precipitation over this State is mainly dominated bysemi permanent systems like off shore trough running along the west coast, low pressure systems forming over the Bay ofBengal during the monsoon season. A well marked low pressure area during 28 September - 3 October 2009 over the Bayof Bengal caused widespread damage to life and property in north Karnataka. In this study, an attempt has been made toexamine the synoptic features of this system that caused heavy rainfall over many districts of the State leading towidespread destruction.


2021 ◽  
Vol 11 (3) ◽  
pp. 4-13
Author(s):  
Zulfat Sh. GALYAUTDINOV

Here is the description of fi nite elementmodels of joints between reinforced concrete slab and column, made in the SIMULIA ABAQUS software package. The variable parameters were the ratio of the sides of the column cmax/cmin and the ratio of the side of the column to the eff ective depth c/h0. The calculation is performed in a non-linear formulation. Finite elementmodels showed realistic behavior: a punching shear pyramid was detected. It was found a signifi cant unevenness in the distribution of tangential deformations, as well as the main compressive deformations of the concrete slab near the column. The nature of the formation and development of the punching shear pyramid depends on the value of the ratio of the sides of the column cmax/cmin and the ratio of the side of the column to the eff ective depth slab c/h0.


Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1679
Author(s):  
Tomasz Wolski ◽  
Bernard Wiśniewski

Understanding the characteristics of storm surges is especially important in the context of ongoing climate changes, which often lead to catastrophic events in the coastal zones of seas and oceans. For this reason, this paper presents the characteristics of the Baltic Sea storm surges and trends in their occurrences through the past 60 years. The study material was based on hourly sea level readings, spanning the years 1961–2020, retrieved from 45 Baltic Sea tide gauges, as well as air pressure and wind field data. Owing to the analysis and visualization of storm situations, two main types of storm surges were identified and characterized: a surge driven by wind and a surge driven by subpressure associated with an active low pressure area. This paper also discusses a third, mixed type of storm surge. Further analyses have indicated that through the past 60 years in the Baltic Sea, the duration of high sea level has increased by 1/3, the average number of storm surges has increased from 3.1 to 5.5 per year, and the maximum annual sea levels have increased—with a trend value of 0.28 cm/year. These processes, also observed in other marine basins, provide strong evidence for contemporary climate change.


MAUSAM ◽  
2021 ◽  
Vol 68 (4) ◽  
pp. 597-606
Author(s):  
B. P. YADAV ◽  
NARESH KUMAR ◽  
SONUM LOTUS

A diagnostic study has been carried out to analyse and understand the causes of unusual rainfall activity over Jammu & Kashmir (J&K) State during 2nd to 5th September, 2014. The careful examination of available historical rainfall data of India Meteorological Department (IMD) network reveals that many stations in the region received ever-highest 24, 48 & 72 hours cumulative rainfall during first week of September in 2014, breaking all previous records. In result, there was flooding in most parts of the State, which has caused loss of human lives and huge loss of property. The synoptic interpretation of this unusual event carried out in the study confirms very favourable meteorological conditions, as there was a western disturbance (WD) in form of cyclonic circulation/trough in mid-tropospheric level, which remained practically stationary over north Pakistan and adjoining Jammu & Kashmir from 2nd to 5th September, 2014 and its interaction with a monsoon Low-Pressure Area (LPA) over northwest & adjoining central India during the same period.  In addition, jet maxima of the order 60-80 knots and high moisture advection from the Bay of Bengal as well as from Arabian Sea over the region were also responsible for this unusual rainfall.


2021 ◽  
Vol 2137 (1) ◽  
pp. 012006
Author(s):  
Bin Li ◽  
Guyang Li ◽  
Wangyang Wu ◽  
Xue Zhang ◽  
Song Guo ◽  
...  

Abstract In this paper, the electro-hydraulic control valve commonly used in ships is taken as the research object, the working principle of the valve is introduced, the model of the valve is established by AMESim software, the model parameters are set and the simulation analysis is carried out. By changing the relevant parameters of the valve, the response speed of the valve can be improved. The simulation results show that the pressure area of load sensitive cavity and the diameter of damping hole have obvious influence on the response speed of valve.


MAUSAM ◽  
2021 ◽  
Vol 60 (3) ◽  
pp. 317-324
Author(s):  
M. MOHAPATRA ◽  
NARESH KUMAR ◽  
B. K. BANDYOPADHYAY

The 26th July 2005 exceptionally heavy rainfall event over Mumbai has been mainly attributed to a mesoscale low/vortex off Konkan coast and urban heat island (UHI) effect as demonstrated by various research groups. However, these studies are limited on observational evidence regarding the existence of the mesoscale vortex and UHI prior to and during this heavy rainfall event. Hence, a study has been undertaken to examine the existence of the mesoscale low off Konkan coast, which might have triggered this exceptionally heavy rainfall over Mumbai and the possible role of UHI effect over Mumbai on this heavy rainfall event. For this purpose the additional synoptic data from Mumbai high region and daily maximum and minimum temperatures over Mumbai region have been analysed. The analysis confirms the existence of a mesoscale low pressure area and isallobaric low to the west of Dahanu during 25th - 26th July 2005. The analysis of daily maximum and minimum temperatures over Mumbai region confirms the UHI effect during 25th -26th July, 2005.


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