flow quality
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2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Ming Cai ◽  
Limin Gao ◽  
Haoxue Li ◽  
Yangbo Ou

Abstract To obtain reliable and accurate experimental data in cascade testing, the influencing factors and the improving method of the flow quality of a highly-loaded compressor cascade under high incidence were investigated through a series of numerical simulations and experiments. The numerical method was validated by experimental data and agreed well at both incidence angles of 0° and 6°. Under the original upper end wall, both experimental and numerical results indicated an unsatisfactory flow quality of the cascade with an obvious nonuniformity of inlet Mach number, and the incidence of the central blade is 3.6° larger than the theoretical value. Using a small curved upper wall can reduce the severe flow separation on the upper wall and achieve a maximum improvement in flow quality under the critical installation angle, where the incidence deviation of the central blade was reduced to 2.1°. Using the combination of adjustable tailboards and a small curved upper end wall can further improve the cascade flow quality. Under the optimal angle of the tailboards, both the inflow uniformity and the outflow periodicity of the three middle blade passages the test requirements, and the incidence deviation of the central blade is reduced to 0.2°.


Author(s):  
Apip Badarudin ◽  
Andriyanto Setyawan ◽  
Windy Hermawan Mitrakusuma

Void fraction and flow pattern play important roles in the performance of evaporator in an air conditioning system. In this paper, the behaviors of void fraction and flow pattern of refrigerant R-290 in a horizontal evaporator are discussed. To simplify the analysis, the evaporator was divided into 10 segments. The void fraction was calculated based on the refrigerant flow quality and the flow pattern was determined on the basis of superficial gas and liquid velocity plotted in the flow pattern map. The calculation was carried on air conditioning machines with nominal capacities of 2.64 kW, 3.62 kW, and 5.28 kW using the evaporator pipe diameters of 3/8 in and 5/16 in. Generally, the lower evaporating temperature results in the higher void fraction, higher gas superficial velocity, and lower liquid superficial velocity. For all ranges of evaporator diameter and cooling capacity, annular flow is found to be the dominant flow pattern. The wavy flow is only found in the lower cooling capacity and larger evaporator diameter. Meanwhile, the slug flow occupies 16.7% to 25.8% of evaporator segment.


Author(s):  
Camilo Aguilera Munoz ◽  
Jonathan Sosa ◽  
Evan W. Hyde ◽  
Gabriel B. Goodwin ◽  
David A. Kessler ◽  
...  

2021 ◽  
Author(s):  
Soheil Akbari ◽  
Seyed Mohammad Taghavi

Abstract Plug and abandonment (P&A) of oil and gas wells is receiving an increased attention. The P&A operation is performed by placing a barrier, such as a cement plug to avoid reservoir fluids migration toward aquifers. To fulfill these requirements, the desired cement plug should be placed in the wellbore with minimum mixing with the in-situ fluid. A rigless way for placing cement slurry in the wellbore is through the dump bailing method, in which a relatively small amount of cement slurry is injected on a mechanical barrier inside the well to replace the in-situ wellbore fluids (mostly fresh water). The dynamics of the fluid placement is governed by several parameters, such as the flow and geometry parameters, and the fluid properties. In this study, we analyze the fluid mechanics of the dump bailing method, via experimentally investigating the effects of the viscosity ratio between the replacing and replaced fluids in the process. The viscosities of the fluids involved have significant effects on the mixing and placement flow quality. In our experiments, the fluid placement is carried out in a near-vertical closed-end pipe (i.e. representative of the well casing) to replace an in-situ light fluid. The two fluids are considered to be miscible, and they have a fixed density difference. Our results show that the most efficient placement happens with the injection of the higher viscous fluid. The outcomes of this study can be used for improving the cementing processes in the dump-bailing method of P&A operations.


Author(s):  
Shenghao Wu ◽  
Jiming Chen ◽  
Qin Chen ◽  
Haitao Pei

Experimental studies were carried out in the 0.6 m×0.6 m continuous transonic wind tunnel of CARDC in order to investigate the flow characteristics of the slotted test section. Experimental results show that the root-mean-square deviation of axial Mach number in the model area is above 0.01 when the test section Mach number is above 1.0.Numerical simulation under the same conditions to investigate the flow characteristics of the slotted section, together with the experimental studies indicate tow phenomena may directly cause the Mach number fluctuation. Firstly, a straight section was installed to connect the nozzle and the test section in the wind tunnel. Weak shock waves due to the curvature discontinuity at the joint of the test section and the straight section contribute to Mach number fluctuation. Secondly, the open-area ratio of both the upper and lower wall of test section, each with 8 slots, is of 10%. The larger porosity leads to stronger expansion waves in the acceleration zone located at the inlet of the test section. The flow was over accelerated because of the stronger expansion wave and thus fluctuate the flow field severely. Two measures were taken to improve the flow quality of the slotted test section based on the above-mentioned analysis: ①Flexible plate instead of solid straight plate was installed to bridge nozzle and test section to eliminate the curvature discontinuity; ②Decreasing the open-area ratio of the upper and lower test section wall to 6% and the number of slots to 6. Numerical and experimental results show that the Mach number fluctuation in the model area was suppressed to a satisfactory degree.


2021 ◽  
Author(s):  
Sabrina Ternier

Stormwater management has transformed throughout the decades with the purpose of maintaining the pre-development hydrological cycle to protect humans and the environment. Despite the progress, Ontario’s water bodies have continued to degrade. This research discusses and recommends three essential modifications to stormwater management to increase environmental and human protection. These include: 1) management based on the four seasons, 2) management based on regional conditions such as local climate and receiving water body characteristics, and 3) updating current stormwater management objectives to provide detailed direction. The Etobicoke Exfiltration System is used as a case study to demonstrate some aspects of the proposed stormwater management modifications and to show the benefits of addressing the five stormwater characteristics (volume, peak flow, quality, duration, frequency) throughout the year. Modelling its performance under 2 to 100 year Chicago storms and use of previous EES studies show the wide range of objectives it can achieve. Future stormwater designs should look to the EES as insight into how stormwater can be properly managed.


2021 ◽  
Author(s):  
Sabrina Ternier

Stormwater management has transformed throughout the decades with the purpose of maintaining the pre-development hydrological cycle to protect humans and the environment. Despite the progress, Ontario’s water bodies have continued to degrade. This research discusses and recommends three essential modifications to stormwater management to increase environmental and human protection. These include: 1) management based on the four seasons, 2) management based on regional conditions such as local climate and receiving water body characteristics, and 3) updating current stormwater management objectives to provide detailed direction. The Etobicoke Exfiltration System is used as a case study to demonstrate some aspects of the proposed stormwater management modifications and to show the benefits of addressing the five stormwater characteristics (volume, peak flow, quality, duration, frequency) throughout the year. Modelling its performance under 2 to 100 year Chicago storms and use of previous EES studies show the wide range of objectives it can achieve. Future stormwater designs should look to the EES as insight into how stormwater can be properly managed.


2021 ◽  
Vol 8 ◽  
Author(s):  
Elisa Damiani ◽  
Erika Casarotta ◽  
Fiorenza Orlando ◽  
Andrea Carsetti ◽  
Claudia Scorcella ◽  
...  

Objectives: Excessive oxygen (O2) administration may have a negative impact on tissue perfusion by inducing vasoconstriction and oxidative stress. We aimed to evaluate the effects of different inhaled oxygen fractions (FiO2) on macro-hemodynamics and microvascular perfusion in a rat model.Methods: Isoflurane-anesthetised spontaneously breathing male Wistar rats were equipped with arterial (carotid artery) and venous (jugular vein) catheters and tracheotomy, and randomized into three groups: normoxia (FiO2 21%, n = 6), hyperoxia (FiO2 100%, n = 6) and mild hypoxia (FiO2 15%, n = 6). Euvolemia was maintained by infusing Lactate Ringer solution at 10 ml/kg/h. At hourly intervals for 4 h we collected measurements of: mean arterial pressure (MAP); stroke volume index (SVI), heart rate (HR), respiratory rate (by means of echocardiography); arterial and venous blood gases; microvascular density, and flow quality (by means of sidestream dark field videomicroscopy on the hindlimb skeletal muscle).Results: MAP and systemic vascular resistance index increased with hyperoxia and decreased with mild hypoxia (p < 0.001 in both cases, two-way analysis of variance). Hyperoxia induced a reduction in SVI, while this was increased in mild hypoxia (p = 0.002). The HR increased under hyperoxia (p < 0.05 vs. normoxia at 3 h). Cardiax index, as well as systemic O2 delivery, did not significantly vary in the three groups (p = 0.546 and p = 0.691, respectively). At 4 h, microvascular vessel surface (i.e., the percentage of tissue surface occupied by vessels) decreased by 29 ± 4% in the hyperoxia group and increased by 19 ± 7 % in mild hypoxia group (p < 0.001). Total vessel density and perfused vessel density showed similar tendencies (p = 0.003 and p = 0.005, respectively). Parameters of flow quality (microvascular flow index, percentage of perfused vessels, and flow heterogeneity index) remained stable and similar in the three groups.Conclusions: Hyperoxia induces vasoconstriction and reduction in skeletal muscle microvascular density, while mild hypoxia has an opposite effect.


Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1203
Author(s):  
André St-Hilaire ◽  
Habiba Ferchichi ◽  
Laureline Berthot ◽  
Daniel Caissie

Environmental flows (eflows) refer to the amount of water required to sustain aquatic ecosystems. In its formal definition, three flow characteristics need to be minimally maintained: quantity, timing and quality. This overview paper highlights the challenges of some of the current methods used for eflow determination in the context of an evolving climate. As hydrological methods remain popular, they are first analyzed by describing some of the potential caveats associated with their usage when flow time series are non-stationarity. The timing of low-flow events will likely change within a season but will also likely shift in seasonality in some regions. Flow quality is a multi-faceted concept. It is proposed that a first simple step to partly incorporate flow quality in future analyses is to include the water temperature as a covariate. Finally, holistic approaches are also critically revisited, and simple modifications to the Ecological Limits of Flow Alteration (ELOHA) framework are proposed.


Author(s):  
Saroj Kumar Patra ◽  
Manmatha K. Roul ◽  
Prashant Kumar Satpathy ◽  
Ashok Kumar Barik

Abstract The aim of the present study is to investigate fluid dynamics and pressure drop across sudden contractions in a two-dimensional, axisymmetric pipe carrying a two-phase mixture of air (secondary phase) and water (primary phase), using the Eulerian-Eulerian model of the multi-phase flow physics to solve the mass, momentum, volume fraction and turbulent quantities with relevant boundary conditions in a finite volume framework. The realizable per-phase k-e and Reynolds stress models have been used as the closure for turbulent quantities along with enhanced wall function for the near-wall treatment. The effects of various parameters such as mass flux, mass flow quality, area ratio (0.056-0.619), flow directions (horizontal/vertical), and system pressure on the two-phase pressure drops due to a contraction in the pipe have been quantified. For both the single and two-phase flows, it has been observed that the pressure drop decreases with area ratio, and increases with mass flux and mass flow quality of two-phase flow. The vena contracta for a single-phase flow was found. But for two-phase flow, neither the vena contracta nor the recirculation zone has been observed, as the mass quality exceeds above 50%. A higher pressure drop has been observed for vertical pipes as compared to the horizontal pipes. The present numerical results have also been validated with published experimental results, believed to be one of the alternatives to the costly experimental methods for predicting the flow dynamics and pressure drop.


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