scholarly journals RECONSTRUCTION OF THE NOVOTROITSK RESERVOIR IN STAVROPOL TERRITORY

2021 ◽  
Author(s):  
А. А. Тkachev ◽  
◽  
А. М. Аnokhin ◽  
Keyword(s):  
Steady Flow ◽  
Flow Rate ◽  
Water Discharge ◽  
Hydraulic Parameters ◽  
Effective Energy ◽  
Subsequent Change ◽  
Flow Energy ◽  
Structure Calculations

Purpose: checking the headrace canal to the fall no. 1 for diversion capacity in connection with a change in the canal discharge. Due to the increase in the estimated flow for irrigation and watering, it is planned to build a canal from the reservoir to the fall no. 1. The tasks of the hydraulic computation included the determining of the headrace canal parameters for the intended catastrophic water discharge of 375 cubic m/s, the computation was carried out taking into account the non-steady flow in canal. For effective energy extinction in the tail-race of the fall, it is required to make a constructive decision and carry out a justification taking into account the topographic conditions of the structure's operation. It is necessary to resolve the issue of energy extinction in tail-race of the structure. Calculations of the toothed overfall for energy extinction in the tail-race are presented. Materials and methods. A version of the dissipator with an indented wall which allows dissipate energy in the constraint environment effectively and obtain a favorable distribution of velocities in the flow in tail race of the structure was adopted for the computation. A step-by-step computation for determining the diversion capacity of the fall no. 1 was carried out: first, the diversion capacity of the headrace canal was determined at a catastrophic discharge Q = 375 cubic m/s with a subsequent change in its hydraulic parameters, then the computation for dissipating the flow energy in the downstream of the structure are given. Results: the calculations of the jagged sill for damping the energy in the tail-race are presented, the indented wall of the fall is designed and the corresponding depths in the tail-race are calculated. Conclusions: the performed computation of the headrace canal and fall no. 1 made it possible to ensure the passage of a catastrophic flow rate equal to 375 cubic m/s, under set conditions.

Investigation of the flow energy dissipation law in a centrifugal impeller in pump mode

2021 ◽  
pp. 095765092110349
Author(s):  
Ran Tao ◽  
Puxi Li ◽  
Zhifeng Yao ◽  
Ruofu Xiao
Keyword(s):  
Energy Dissipation ◽  
Flow Rate ◽  
Performance Estimation ◽  
Vortical Flow ◽  
Wall Friction ◽  
Negative Slope ◽  
Centrifugal Impeller ◽  
Pump Mode ◽  
Flow Energy ◽  
Flow Interaction

Centrifugal impeller is usually designed for water pumping. Fluid get energy from impeller but also lose energy when passing through it. To improve the efficiency and have a better operation stability, it is necessary to understand the flow energy dissipation in centrifugal impeller in pump mode. In this case, a thermodynamic analysis is conducted on a model centrifugal pump unit based on computational fluid dynamics (CFD) simulation. Typical performance curve is found with a positive-slope efficiency curve and a negative-slope head curve. With the decreasing of flow rate, both the impeller head and the flow energy dissipation (FED) will rise up. The FED is found related to the flow regime. The complex undesirable flow pattern induces high FED under off-design conditions especially at very small partial-load. Based on the visualization, FED is found with two main sources including the wall friction and the flow interaction. At over-load and design-load, the wall friction induced FED is dominant. With the decreasing of flow rate, flow interaction induced FED becomes dominant. The typical strong FED sites are found related to the striking, separation, merging and interaction of both smooth flow and vortical flow. The FED analysis will correlate the pump performance estimation and guide the design.

Secretion of K and fluid by rat submaxillary during sympathetic nerve stimulation

1975 ◽  
Vol 229 (4) ◽  
pp. 1056-1061 ◽  
Author(s):  
LH Schneyer
Keyword(s):  
Steady Flow ◽  
Flow Rate ◽  
Sympathetic Innervation ◽  
Stimulus Frequency ◽  
Submaxillary Gland ◽  
Pulse Frequency ◽  
Initial Flow ◽  
Saliva Secretion ◽  
High Concentrations ◽  
Two Phases

Stimulation of the sympathetic innervation to rat submaxillary gland is known to evoke saliva which contains high concentrations of potassium (130-160 meq/liter). Relationships were examined between salivary [K] and several parameters of the stimulation, including pulse frequency and duration of the stimulus train and rate of flow of the evoked saliva. Secretion of sympathetically evoked saliva was found to occur in two phases. After stimulation was started, flow rate was relatively high initially, and then decreased to a lower, relatively steady value. Initial and steady flow rates were maximal when stimulus frequency was 10 Hz. Salivary [K] was lowest initially, and, at that time, was inversely related to flow rate. At steady flow, [K] was flow independent. While salivary [K] was lower during initial than during steady secretion, the rate of K secretion was initially higher. During the initial phase, K decreased in the gland, and this decrease was sufficient to account for the increased amount of K secreted in initial saliva and for the increased initial flow.

Subcooled Flow Boiling Inception and Heat Transfer of Water in a Circular Tube Under Pulsatile Flow

2018 ◽  
Author(s):  
Hongsheng Yuan ◽  
Sichao Tan ◽  
Kun Cheng ◽  
Xiaoli Wu ◽  
Chao Guo ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Steady Flow ◽  
Flow Rate ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Nucleation Site ◽  
Subcooled Flow Boiling ◽  
Average Heat ◽  
Subcooled Flow

The flow rate can fluctuate in offshore nuclear power systems which are exposed to wind and waves, as well as in loops where flow instabilities occur, resulting in different thermal-hydraulic characteristics compared with that under steady flow. Among the thermal-hydraulic characteristics, onset of nucleate boiling (ONB) model determines whether the fluid is boiling, and boiling heat transfer is crucial to equipment performance and safety, both being key issues in subcooled flow boiling. Therefore, an experimental study was conducted to investigate how an imposed periodic flow oscillation affects the boiling inception and heat transfer of subcooled flow boiling of water in a vertical tube. The experiments were conducted under atmospheric pressure with the average flow rate ranging from 96kg/m2s to 287kg/m2s and heat flux ranging from 10kW/m2 to 197kW/m2. The relative pulsatile amplitude range is 0.1–0.3 and pulsatile period range is 10s-30s. Photographic images and thermal parameters such as temperatures and flow rate were recorded. The lack of nucleation site on the heated surface of the test section results in high wall superheat at ONB. The effects of pulsatile amplitude and period on superheat at boiling onset and average heat transfer were analyzed. The results show that the superheat at boiling inception is decreased when the average heat flux is lower than the heat flux at boiling inception of the corresponding steady flow, and the superheat at boiling onset is increased when the average heat flux is higher than the heat flux at boiling onset of the corresponding steady flow. The above effect of flow rate pulsation on superheat increases with increasing amplitude and decreasing period, and the mechanism can be explained by boiling nucleation theory. The lack of large active nucleation site also affects the boiling heat transfer. By comparing the contribution of nucleate boiling to heat transfer with the widely used Cooper’s pool boiling correlation, the subcooled flow boiling was found suppressed by convection. The average heat transfer of both the intermittent flow boiling and the single phase flow is influenced by flow oscillation.

scholarly journals Numerical Study on the Effects of Relative Diameters on the Performance of Small Modular Reactors Driven by Natural Circulation

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5881
Author(s):  
Young Jin Kim ◽  
Byung Jin Lee ◽  
Kunwoo Yi ◽  
Yoon Jae Choe ◽  
Min Chul Lee
Keyword(s):  
Temperature Distribution ◽  
Steam Generator ◽  
Flow Rate ◽  
Numerical Study ◽  
Natural Circulation ◽  
Hydraulic Parameters ◽  
Small Modular Reactors ◽  
Velocity Changes ◽  
Energy Equations ◽  
Tube Pitch

Most of the small modular reactors (SMRs) under development worldwide present the same components: an integral reactor vessel with a low-positioned core as the heat source and a high-positioned steam generator as the heat sink. Moreover, some SMRs are being designed to be driven by natural circulation during normal power generation. This work focused on such designs and on their performance, considering the changes generated by the geometric and hydraulic parameters of the system. Numerical simulations using mass, momentum, and energy equations that considered buoyancy forces were performed to determine the effects of various geometric and hydraulic parameters, such as diameters and flow resistances, on the reactor’s performance. It was found that nonuniform diameters promote velocity changes that affect the natural circulation flow rate. Moreover, the reactor’s temperature distribution depends on the steam generator tube pitch. Therefore, the hydraulic diameters of the reactor’s coolant passages should be maintained as uniform as possible to obtain a more uniform temperature distribution and a larger mass flow rate in SMRs.

scholarly journals Cavitation in swirling flows of hydraulic spillways

2019 ◽  
Vol 91 ◽  
pp. 07022
Author(s):  
Genrikh Orekhov
Keyword(s):  
Flow Rate ◽  
Vortex Flow ◽  
Structural Elements ◽  
Flow Energy ◽  
Operating Modes ◽  
Swirl Angle ◽  
Energy Dissipators ◽  
High Head ◽  
The Impact

During operation of high-head hydraulic spillway systems, cavitation phenomena often occur, leading to destruction of structural elements of their flow conductor portions. The article is devoted to the study of erosion due to cavitation in the circulation flows of eddy hydraulic spillways, including those equipped with counter-vortex flow energy dissipators. Cavitation destructive effects depend on many factors: intensity consisting in the rate of decrease in the volume or mass of a cavitating body per unit of time, the stage of cavitation, geometric configuration of the streamlined body, the content of air in water, the flow rate, the type of material. The objective of the study consisted in determination of cavitation impacts in circulating (swirling) water flows. The studies were conducted by a method of physical modeling using high-head research installations. Distribution of amplitudes of pulses of shock cavitation impact is obtained according to the frequency of their occurrence depending on the flow velocity, the swirl angle, the height of the cavitating drop wall and the stage of cavitation. The impact energy depending on the stage of cavitation and the flow rate is given for different operating modes of the counter-vortex flow energy dissipators of a hydraulic spillway. In the conclusions, it is noted that cavitation impacts in the circulation flows occur mainly inside the flow, which is a fundamental difference from similar processes in axial flows.

The Effect of Trace Impurities on Condensed Electrode and Microwave Discharges through Nitrogen

1971 ◽  
Vol 49 (10) ◽  
pp. 1671-1676 ◽  
Author(s):  
R. R. Baker ◽  
A. Jacob ◽  
C. A. Winkler
Keyword(s):  
Electron Temperature ◽  
Steady Flow ◽  
Flow Rate ◽  
Trace Impurities ◽  
Nitrogen Gas ◽  
Electrode Discharge ◽  
Microwave Discharges

Traces of various gases have been added to a stream of purified nitrogen gas prior to entering either a microwave or a condensed electrode discharge, and the effect of the presence of these gases on the steady flow rate of nitrogen atoms obtained from the discharge has been measured. Suggestions for the effect of the impurity gases on the possible reactions occurring in the discharge have been put forward. It seems probable that an important feature of the presence of the impurities may be their effect on the electron temperature in the discharge.

scholarly journals Water Discharge Management Based on Open and Closed Cylinders in the Gravitation Water Vortex Power Plant

2021 ◽  
Vol 5 (1) ◽  
pp. 22-36
Author(s):  
Muhammad Hasan Basri ◽  
Ainun Nasuki
Keyword(s):  
Power Plant ◽  
Water Flow ◽  
Flow Rate ◽  
Water Pressure ◽  
Water Discharge ◽  
Water Flow Rate ◽  
Discharge Measurement ◽  
Closed Basin ◽  
Advantages And Disadvantages ◽  
Discharge Management

A Gravitation Water Vortex Power Plant (GWVPP) tool has been made to determine how much water flow is needed to generate electricity. This research was conducted by changing the flow rate and water pressure to determine the effect on the performance of a vortex power plant, and in previous studies, no one has made changes to the discharge and water pressure. The type of basin position used in this study is an open basin position and a closed basin position. Based on the advantages and disadvantages of each type of blade used, a study was carried out using the type of turbine blade model L by changing the water flow rate and water pressure at a predetermined position to determine the effect of water discharge and pressure on the turbine rotational speed. From the results of testing the water discharge measurement in a closed basin which is carried out on the addition of each flow of water discharge at the angle of the faucet 0o to 90o with a volume (V) 98 L and time (t) 1.11 minutes to 2.5 minutes, it can be seen that the average discharge value (Q) the resulting 81.08 l / s. and from the results of testing the water discharge measurement in the open basin which is carried out to the addition of each flow of water discharge at the angle of the faucet 0o to 90o with a volume (V) 98 L and time (t) 1.28 minutes to 4.1 minutes it can be seen that the average discharge value (Q ) resulting in 65.21 l / s.

scholarly journals OPERATIONAL PERFORMANCE OF VERTICAL UPFLOW ROUGHING FILTER FOR PRE-TREATMENT OF LEACHATE USING LIMESTONE FILTER MEDIA

2013 ◽  
pp. 117-125
Author(s):  
Augustine Chioma Affam
Keyword(s):  
Steady Flow ◽  
Removal Efficiency ◽  
Flow Rate ◽  
Operational Performance ◽  
Main Experiment ◽  
Filter Media ◽  
Filtration Process ◽  
Optimum Treatment ◽  
Pre Treatment ◽  
Filtration Technique

This study was conducted to investigate the removal of COD, BOD, turbidity and colour from leachate using vertical upflow filtration technique. Limestone media with a density of 2554kg/m3 was crushed and graded in sizes of 4-8 mm, 8-12 mm and 12-18 mm. Trial runs were done before the main experiment at an interval of 24 h analysis. Leachate was between pH 7.94 to 8.12 before experiments but increased to pH 8.42 after the filtration process. Maximum headloss at steady flow rate 20mL/min was 0.5 cm. The optimum treatment was achieved with 4 – 8 mm, 8 – 12 mm & 12 – 18 mm media size in combination and removal efficiency was 22 to 81 %, 22 to 75 %, 32 to 86 %, and 36 to 62 % for BOD, COD, turbidity and colour respectively. Vertical upflow roughing filter can be used for pre-treatment of leachate before further treatment.

Wall Shear Stress in Development Process of Aneurysm Around Anterior Communicating Artery

2004 ◽  
Author(s):  
Kenichi Umezawa ◽  
Akihiro Torisu ◽  
Susumu Kudo ◽  
Ryuhei Yamaguchi
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Steady Flow ◽  
Flow Rate ◽  
Development Process ◽  
Anterior Cerebral Artery ◽  
High Flow ◽  
Anterior Communicating Artery ◽  
Wall Shear ◽  
Small Aneurysm

In the present paper, the distribution of the wall shear stress around the apex of the anterior communicating artery (ACoA) in the development process of aneurysm has been studied in laminar steady flow. The anterior communicating artery composing the circle of Willis is one of the predilection sites where the cerebral aneurysm occurs frequently. Once the small aneurysm initiates around the apex in one anterior cerebral artery (ACA) with high flow rate, the distribution of the wall shear stress abruptly changes around the initial aneurysm. With the development of the aneurysm, the wall shear stress distinctly changes along the concaved surface of the aneurysm. The distribution of the wall shear stress in the development process of the aneurysm is physiologically discussed from the viewpoint of hemodynamics.

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