scholarly journals Parameter optimization of anti-crystallization flocking drainage pipe based on macro force and displacement characteristics of villus

2021 ◽  
Vol 25 (6 Part A) ◽  
pp. 4127-4135
Author(s):  
Shiyang Liu ◽  
Xuefu Zhang ◽  
Feng Gao ◽  
Yun Li ◽  
Dulaimic Al
Keyword(s):  
Flow Rate ◽  
Drainage System ◽  
Low Flow ◽  
Normal Operation ◽  
Maintenance Cost ◽  
Principal Stresses ◽  
Lining Structure ◽  
Order Of Magnitude ◽  
Drainage Pipe ◽  
Safety And Stability

The crystal blockage of tunnel drainage pipe seriously affects the smoothness of the whole drainage system. Therefore, it is very important to effectively prevent crystal plugging in tunnel drainage system to ensure the safety and stability of lining structure during tunnel operation. Based on the macro force and displacement characteristics of villus, the optimization of villus diameter and villus length of flocked drainage pipe at low flow rate was studied by numerical simulation. The results show that: there is a difference of 1-2 orders of magnitude between the 3-D displacements of the bottom villus and one order of magnitude between the 3-D displacements of the side villus of the flocked drainage pipe; with the increase of villus length, the 3-D displacement of villus increased parabola and with the increase of villus diameter, the 3-D displacement of villus decreased gradually; the results show that the first and third principal stresses of the bottom villus increase linearly with the increase of villus length, while the first and third principal stresses of the side villus increase parabola with the increase of villus length; when the flow rate is 2 cm/s, the diameter of villus is 0.6 mm and the length of villus is 20 mm. Flocking drainage pipe anti crystal plugging technology fills the blank of tunnel drainage pipe anti crystal plugging research. This technology can reduce the maintenance cost of tunnel drainage system during operation, and ensure the safe and normal operation of the tunnel.

scholarly journals Crystallization law of karst water in tunnel drainage system based on DBL theory

Open Physics ◽  
2021 ◽  
Vol 19 (1) ◽  
pp. 241-255
Author(s):  
YongDong Wang ◽  
Yang Liu ◽  
ChuFan Qi ◽  
TianYue Zhou ◽  
Ming Ye ◽  
...  
Keyword(s):  
Flow Rate ◽  
Pipe Wall ◽  
Functional Model ◽  
Drainage System ◽  
Crystallization Rate ◽  
Normal Operation ◽  
Karst Area ◽  
Karst Water ◽  
Flow State ◽  
Drainage Pipe

Abstract When a tunnel is constructed in a karst area, crystallization of the drainage pipe caused by karst water often threatens the normal operation of the tunnel. This work contributes to this field of research by proposing a functional model based on the diffusion boundary layer (DBL) theory proposed by Dreybrodt in the 1990s. The model is formed by determining the flow rate distribution of the drainage pipe in a laminar flow state and turbulent state, and then by applying Fick’s diffusion law and Skelland’s approximate formula. Then, to further verify the applicability of the functional model, a model test was carried out in the laboratory and the test results are compared to the theoretical results. The results show that the crystallization rate of karst water is mainly affected by the roughness of the pipe wall, followed by the slope of pipes. The slope can affect flow state by controlling the flow rate, which in turn affects the crystallization rate of karst water. When the slope of the drainage pipe is 3, 4, and 5%, the error between the experimental results and the theoretical calculation results is 24.7, 8.07, and 27.9%, respectively, and when the liquid level in the pipe is 7.2, 10.2, and 13.3 mm, the error is 27.9, 9.82, and 2.07%, respectively. Considering that the flow will take away the crystalline deposits on the pipe wall in the experiment, although some results have certain errors, they do not affect the overall regularity.

scholarly journals Optimization Study of Fluffy Materials Flocking Drainage Pipes to Resist Blockage Based on MD Binding Energy

Coatings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 853
Author(s):  
Shiyang Liu ◽  
Xuefu Zhang ◽  
Yuanfu Zhou ◽  
Feng Gao
Keyword(s):  
Aqueous Solution ◽  
Calcium Carbonate ◽  
Binding Energy ◽  
Drainage System ◽  
Normal Operation ◽  
Maintenance Cost ◽  
External Energy ◽  
Adsorption Effect ◽  
Effective Prevention ◽  
Drainage Pipe

Drainage pipe blockage resulting from crystals is one of the causes for cracking and leakage of tunnel lining. Therefore, effective prevention from drainage pipe blockage caused by crystals is crucial to ensure the safety and stability of lining structures during the operation of tunnel drainage system. Based on a large number of indoor model tests and numerical simulation analyses, binding energy between four materials and the calcium carbonate aqueous solution (“solid + liquid” system) and that between the four materials and the two typical growth crystals of calcium carbonate (“solid + solid” system) were studied. The research results indicated that: (1) The four materials all had an adsorption effect on the calcium carbonate aqueous solution system, and the PA6 had the greatest adsorption effect while the PP had the smallest adsorption effect; (2) There was spontaneous adsorption between the PVC or PA6 and the two typical growth crystals of calcium carbonate and no adsorption between the PP or SiC and the two typical growth crystals of calcium carbonate unless external energy was in place; (3) The PP and SiC can be used as the materials for drainage pipe flocking, but it shall be ensured that the fluffy material has a good geometrical property. The prevention technology for crystallization that causes drainage pipe blockage fills the gap in the research of drainage pipe blockage caused by crystals, which can reduce the maintenance cost for the operation of the tunnel drainage system and ensure safe and normal operation of the tunnel.

scholarly journals Anti-Blocking Mechanism of Flocking Drainage Pipes in Tunnels Based on Mathematical Modeling Theory

Coatings ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 961
Author(s):  
Shiyang Liu ◽  
Xuefu Zhang ◽  
Feng Gao
Keyword(s):  
Mathematical Modeling ◽  
Flow Velocity ◽  
Dynamic Balance ◽  
Water Pressure ◽  
Normal Operation ◽  
Maintenance Cost ◽  
Effective Prevention ◽  
Drainage Systems ◽  
Drainage Pipe ◽  
Blocking Mechanism

Crystalline pipe plugging in tunnel drainage systems is one of the causes of tunnel lining cracking and water leakage. Therefore, effective prevention of crystalline pipe blockage in tunnel drainage systems is very important to ensure the safety and stability of the lining structure during tunnel operation. Combined with the theories of fluid mechanics, structural mechanics and basic physics, the flocking and anti-blocking mechanism of drainage pipe was comprehensively analyzed by using the method of mathematical modeling, including: (1) the calculation expression of average velocity of the flocked section of a flocked drainage pipe v = Q/(C1 − C2(r + r′)) and the calculation formula of flowing water pressure under the action of groundwater Fw =  KAγQ2/(2g(C1 − C2(r + r′))2); (2) the flow velocity v0 in the flocked drainage pipe shall meet v2 < 4gπrlτ1/γKA, crystals will be attached to the fluff and the crystals will maintain dynamic balance; (3) the flow velocity v0 in the flocked drainage pipe shall meet v2 ≥ 4gπrlτ1/γKA, crystals will not adhere to the fluff and the flocked drainage pipe will remain unobstructed. The research on the mechanism of preventing blockage of flocking drainage pipes fills the gap in research theory in this regard, contributes to the popularization and application of blocking prevention technology of flocking drainage pipes, reduces the maintenance cost during operation of tunnel drainage systems and ensures the safe and normal operation of tunnels.

scholarly journals Ecological problems of the river Novaya (St. Petersburg) and ways to solve them

2020 ◽  
pp. 94-110
Author(s):  
S.A. Kondratyev ◽  
A.Yu. Bruchanov ◽  
N.V. Ignatyeva ◽  
A.E. Lapenkov ◽  
A.M. Rasulova ◽  
...  
Keyword(s):  
Flow Rate ◽  
Catchment Area ◽  
Drainage System ◽  
Aquatic System ◽  
Low Flow ◽  
Geochemical Data ◽  
Chemical Pollution ◽  
Agricultural Activity ◽  
Organic Substances ◽  
Calculated Concentration

Main sources of pollution of the river Novaya, one of the most ecologically unfavorable water bodies in St. Petersburg, have been revealed on the basis of hydrological, hydrochemical and geochemical data. The river lost natural water supply and its length decreased by 4 times after the runoff from the upper part of catchment was redirected to the river Dudergofka during the construction of the Pulkovo Airport several decades ago. Currently, the river is a drainage system of agricultural territory, supplying a system of six connected ponds at urban area. The main ecological problem of the aquatic system under study has been found to be nutrient and organic pollution. Main reason of pollution is intensive agricultural activity at the catchment area. As a result, a huge amount of phosphorus, nitrogen and organic substances enters the hydrographic network. Low flow rate of the water system makes worse the development of negative processes in the ecosystem. The main polluter is a livestock enterprise located in the upper part of the catchment area. It discharges wastewater into the drainage system in the catchment area and manures agricultural fields directly adjacent to the riverbed. In accordance with the evaluation criteria of the degree of surface waters chemical pollution, approved by the Ministry of Natural Resources of the Russian Federation, the situation is assessed as extreme in the aquatic system, and at some sites - as a zone of ecological disaster by a number of parameters. No contamination of water and bottom sediments, as well as soils in the catchment area with priority organic pollutants previously entering from the airport territory was detected. Nutrient loading on the aquatic system of the catchment area from the agricultural enterprise has been calculated. It has been assessed that the use of the best available technologies for agricultural activity could reduce the phosphorus load by 9 % and the nitrogen load by 28 %. Currently, the calculated concentration of total phosphorus in the drainage system in the catchment area is 4 times higher than the hyper eutrophic state limit. An improvement in the ecological situation can be achieved by optimizing agricultural activity in the catchment area, periodical removal of some nutrients and organic substances by mowing macrophytes in the swampy floodplain area, establishing a coastal protective zone and increasing the flow rate as a result of the return of runoff from the upper part of the river catchment to the former course

scholarly journals Effectiveness of a New Drainage System for Decreasing Erosion in Road Hillslopes

2021 ◽  
Vol 14 ◽  
pp. 117862212098872
Author(s):  
María Fernández-Raga ◽  
Iván García-Díez ◽  
Julian Campo ◽  
Julio Viejo ◽  
Covadonga Palencia
Keyword(s):  
Service Life ◽  
Drainage System ◽  
Economic Feasibility ◽  
Scale Model ◽  
Maintenance Cost ◽  
Road Maintenance ◽  
Experimental Conditions ◽  
Traditional System ◽  
Strategic Value ◽  
On The Road

Water is one of the most important erosive agents in roadside hillslopes. When these are built with ineffective drainage systems, erosion occurs, reducing road’s service life. However, these systems are not receiving the appropriate importance, given their strategic value. Therefore, a new drainage system called ‘branched’ is proposed in this study. Its technical and economic feasibility is compared with those of the traditional system, which consists of drainages with lines that follow maximum hillslope, to assess differences in relation to erosion, construction and maintenance costs, and service life. Different parameters were analysed, such as the average velocity of water (mm−1) running through the channels, its average specific energy (kJ), and its drag force (N). A scale model was constructed and used to test these factors before implementing it in natural terrain for testing it under field conditions. According to the theoretical and measured results, these factors were lower in the branched drainage than in the traditional one (from 24% to 34% in speed, from 37% to 60% in energy, and from 51% to 73% in force). The service life of hillslopes with a branched system of up to 0.5 m high and 1:2 grade is significantly longer than in those with a traditional drainage. Although the initial economic expense for the construction of the branched system is higher (€3534/m3 as opposed to €2930/m3 for the traditional one), its maintenance cost will be lower than the traditional one (€1230/m3 per year for the branched one as opposed to €1332/m3 per year for the traditional one). Consequently, under our experimental conditions, the proposed drainage will be profitable from the eighth year of construction, saving on the road maintenance in the following 15 years of service life.

scholarly journals Backflow effects on mass flow gain factor in a centrifugal pump

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042199886
Author(s):  
Wenzhe Kang ◽  
Lingjiu Zhou ◽  
Dianhai Liu ◽  
Zhengwei Wang
Keyword(s):  
Centrifugal Pump ◽  
Mass Flow ◽  
Flow Rate ◽  
Low Frequency ◽  
Gain Factor ◽  
Low Flow ◽  
Cavity Volume ◽  
Cavitating Flows ◽  
Inlet Tube ◽  
Low Flow Rate

Previous researches has shown that inlet backflow may occur in a centrifugal pump when running at low-flow-rate conditions and have nonnegligible effects on cavitation behaviors (e.g. mass flow gain factor) and cavitation stability (e.g. cavitation surge). To analyze the influences of backflow in impeller inlet, comparative studies of cavitating flows are carried out for two typical centrifugal pumps. A series of computational fluid dynamics (CFD) simulations were carried out for the cavitating flows in two pumps, based on the RANS (Reynolds-Averaged Naiver-Stokes) solver with the turbulence model of k- ω shear stress transport and homogeneous multiphase model. The cavity volume in Pump A (with less reversed flow in impeller inlet) decreases with the decreasing of flow rate, while the cavity volume in Pump B (with obvious inlet backflow) reach the minimum values at δ = 0.1285 and then increase as the flow rate decreases. For Pump A, the mass flow gain factors are negative and the absolute values increase with the decrease of cavitation number for all calculation conditions. For Pump B, the mass flow gain factors are negative for most conditions but positive for some conditions with low flow rate coefficients and low cavitation numbers, reaching the minimum value at condition of σ = 0.151 for most cases. The development of backflow in impeller inlet is found to be the essential reason for the great differences. For Pump B, the strong shearing between backflow and main flow lead to the cavitation in inlet tube. The cavity volume in the impeller decreases while that in the inlet tube increases with the decreasing of flow rate, which make the total cavity volume reaches the minimum value at δ = 0.1285 and then the mass flow gain factor become positive. Through the transient calculations for cavitating flows in two pumps, low-frequency fluctuations of pressure and flow rate are found in Pump B at some off-designed conditions (e.g. δ = 0.107, σ = 0.195). The relations among inlet pressure, inlet flow rate, cavity volume, and backflow are analyzed in detail to understand the periodic evolution of low-frequency fluctuations. Backflow is found to be the main reason which cause the positive value of mass flow gain factor at low-flow-rate conditions. Through the transient simulations of cavitating flow, backflow is considered as an important aspect closely related to the hydraulic stability of cavitating pumping system.

Assessment of the Use of Humidified Nasal Cannulas for Oxygen Therapy in Patients with Epistaxis

ORL ◽  
2021 ◽  
pp. 1-5
Author(s):  
Jingjing Liu ◽  
Tengfang Chen ◽  
Zhenggang Lv ◽  
Dezhong Wu
Keyword(s):  
Flow Rate ◽  
Oxygen Therapy ◽  
Preliminary Investigation ◽  
Nasal Cannula ◽  
Low Flow ◽  
Antiplatelet Drugs ◽  
Flow Rates ◽  
The Past ◽  
Oxygen Inhalation ◽  
Significant Difference

<b><i>Introduction:</i></b> In China, nasal cannula oxygen therapy is typically humidified. However, it is difficult to decide whether to suspend nasal cannula oxygen inhalation after the nosebleed has temporarily stopped. Therefore, we conducted a preliminary investigation on whether the use of humidified nasal cannulas in our hospital increases the incidence of epistaxis. <b><i>Methods:</i></b> We conducted a survey of 176,058 inpatients in our hospital and other city branches of our hospital over the past 3 years and obtained information concerning their use of humidified nasal cannulas for oxygen inhalation, nonhumidified nasal cannulas, anticoagulant and antiplatelet drugs, and oxygen inhalation flow rates. This information was compared with the data collected at consultation for epistaxis during these 3 years. <b><i>Results:</i></b> No significant difference was found between inpatients with humidified nasal cannulas and those without nasal cannula oxygen therapy in the incidence of consultations due to epistaxis (χ<sup>2</sup> = 1.007, <i>p</i> &#x3e; 0.05). The same trend was observed among hospitalized patients using anticoagulant and antiplatelet drugs (χ<sup>2</sup> = 2.082, <i>p</i> &#x3e; 0.05). Among the patients with an inhaled oxygen flow rate ≥5 L/min, the incidence of ear-nose-throat (ENT) consultations due to epistaxis was 0. No statistically significant difference was found between inpatients with a humidified oxygen inhalation flow rate &#x3c;5 L/min and those without nasal cannula oxygen therapy in the incidence of ENT consultations due to epistaxis (χ<sup>2</sup> = 0.838, <i>p</i> &#x3e; 0.05). A statistically significant difference was observed in the incidence of ENT consultations due to epistaxis between the low-flow nonhumidified nasal cannula and nonnasal cannula oxygen inhalation groups (χ<sup>2</sup> = 18.428, <i>p</i> &#x3c; 0.001). The same trend was observed between the 2 groups of low-flow humidified and low-flow nonhumidified nasal cannula oxygen inhalation (χ<sup>2</sup> = 26.194, <i>p</i> &#x3c; 0.001). <b><i>Discussion/Conclusion:</i></b> Neither high-flow humidified nasal cannula oxygen inhalation nor low-flow humidified nasal cannula oxygen inhalation will increase the incidence of recurrent or serious epistaxis complications; the same trend was observed for patients who use anticoagulant and antiplatelet drugs. Humidification during low-flow nasal cannula oxygen inhalation can prevent severe and repeated epistaxis to a certain extent.

scholarly journals Effect of Air Injection on the Internal Flow Characteristics in the Draft Tube of a Francis Turbine Model

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1182
Author(s):  
Seung-Jun Kim ◽  
Yong Cho ◽  
Jin-Hyuk Kim
Keyword(s):  
Flow Rate ◽  
Draft Tube ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Air Injection ◽  
Low Flow ◽  
Francis Turbine ◽  
Navier Stokes ◽  
Vortex Rope

Under low flow-rate conditions, a Francis turbine exhibits precession of a vortex rope with pressure fluctuations in the draft tube. These undesirable flow phenomena can lead to deterioration of the turbine performance as manifested by torque and power output fluctuations. In order to suppress the rope with precession and a swirl component in the tube, the use of anti-swirl fins was investigated in a previous study. However, vortex rope generation still occurred near the cone of the tube. In this study, unsteady-state Reynolds-averaged Navier–Stokes analyses were conducted with a scale-adaptive simulation shear stress transport turbulence model. This model was used to observe the effects of the injection in the draft tube on the unsteady internal flow and pressure phenomena considering both active and passive suppression methods. The air injection affected the generation and suppression of the vortex rope and swirl component depending on the flow rate of the air. In addition, an injection level of 0.5%Q led to a reduction in the maximum unsteady pressure characteristics.

scholarly journals Hydraulic transmissivity inferred from ice-sheet relaxation following Greenland supraglacial lake drainages

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ching-Yao Lai ◽  
Laura A. Stevens ◽  
Danielle L. Chase ◽  
Timothy T. Creyts ◽  
Mark D. Behn ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Ice Sheet ◽  
Drainage System ◽  
Greenland Ice Sheet ◽  
Field Observations ◽  
Surface Uplift ◽  
Drainage Networks ◽  
Order Of Magnitude ◽  
Lake Drainage ◽  
Magnitude Increase

AbstractSurface meltwater reaching the base of the Greenland Ice Sheet transits through drainage networks, modulating the flow of the ice sheet. Dye and gas-tracing studies conducted in the western margin sector of the ice sheet have directly observed drainage efficiency to evolve seasonally along the drainage pathway. However, the local evolution of drainage systems further inland, where ice thicknesses exceed 1000 m, remains largely unknown. Here, we infer drainage system transmissivity based on surface uplift relaxation following rapid lake drainage events. Combining field observations of five lake drainage events with a mathematical model and laboratory experiments, we show that the surface uplift decreases exponentially with time, as the water in the blister formed beneath the drained lake permeates through the subglacial drainage system. This deflation obeys a universal relaxation law with a timescale that reveals hydraulic transmissivity and indicates a two-order-of-magnitude increase in subglacial transmissivity (from 0.8 ± 0.3 $${\rm{m}}{{\rm{m}}}^{3}$$ m m 3 to 215 ± 90.2 $${\rm{m}}{{\rm{m}}}^{3}$$ m m 3 ) as the melt season progresses, suggesting significant changes in basal hydrology beneath the lakes driven by seasonal meltwater input.

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