scholarly journals Experimental study on flow over arced-plan porous weirs

2021 ◽  
Author(s):  
M. Pirzad ◽  
M. H. Pourmohammadi ◽  
H. Ghorbanizadeh Kharazi ◽  
M. Solimani Babarsad ◽  
E. Derikvand
Keyword(s):  
Discharge Coefficient ◽  
Gene Expression Programming ◽  
Reduction Factor ◽  
Effective Length ◽  
Filling Material ◽  
Aquatic Life ◽  
Geometric Conditions ◽  
Wide Range ◽  
Free Discharge ◽  
Submerged Discharge

Abstract Unlike conventional impermeable weirs, porous weirs without clogging the flow and passage of aquatic life with increased aeration and aerobic reactions with minimal negative effects on the environment are known as environmentally friendly structures. This study experimentally investigates the hydraulic performance of Arced-Plan Porous Weirs (APPWs) in different hydraulic and geometric conditions. For this purpose, four different porous and two solid weirs were examined. Experiments were conducted in a horizontal laboratory flume with length, width, and height of 20, 0.6, and 0.5 m, respectively, for a wide range of flow rates, particle sizes, and three arc lengths. Results showed that increasing filling material sizes increases the free discharge coefficient and reduces the submerged Discharge Reduction Factor (DRF). It was also concluded that the weirs’ effective length significantly impacts the free discharge coefficient and has no significant effect on the threshold submergence index and submerged DRF. Unlike solid weirs, the threshold submergence of porous weirs occurs at a downstream depth lower than the weir's height. Finally, according to the dimensional analysis and Gene-Expression Programming (GEP) approach, three relations were extracted to calculate the free discharge coefficient, threshold submergence index, and submerged discharge reduction factor for APPWs.

Spool Valve Hydraulic Measurement Flow Pattern Error Based on Variable Discharge Coefficient

2015 ◽  
Vol 667 ◽  
pp. 444-448
Author(s):  
Zhuo Lin
Keyword(s):  
Flow Pattern ◽  
Discharge Coefficient ◽  
Compensation Method ◽  
Measuring Process ◽  
Important Method ◽  
Flow Pattern Transition ◽  
Spool Valves ◽  
Spool Valve ◽  
Submerged Discharge

Spool valves are the main elements in electro-hydro servo valves. Hydraulic measurement is an important method for spool valve’s null cutting measuring process. Because of the flow pattern transition, the discharge coefficient is a variable. This phenomenon causes errors if we assume the discharge coefficient is a constant as we always do. In this paper, the variable discharge coefficient is considered to the submerged discharge equation, and the flow pattern error is defined. For improving the precision of overlap values measurements, a compensation method of flow pattern error is presented in this paper.

Hot-Pressed Barium Sulphate Ceramic Waste Forms for Direct Immobilisation of Medium Level Magnox Waste

1981 ◽  
Vol 6 ◽  
Author(s):  
A. Briggs ◽  
D.V.C. Jones ◽  
G.B. Cole
Keyword(s):  
Hot Pressing ◽  
Open Porosity ◽  
Matrix Material ◽  
Direct Conversion ◽  
Barium Sulphate ◽  
Reduction Factor ◽  
Waste Form ◽  
Internal Surfaces ◽  
Wide Range ◽  
Leaching Behaviour

ABSTRACTA possible method of treatment for Magnox cladding waste is by dissolution in nitric acid and precipitation of barium sulphate-based floc with which radioactive ions are co-precipitated. The floc could then be immobilised in a matrix material such as cement or bitumen to give the waste form, or alternatively can be converted directly into a waste form by hot pressing.This paper describes the direct conversion of barium sulphate floc, containing simulated radwaste, into a synthetic, ceramic version of the natural mineral barite by a hot-pressing route. By variation of the parameters pressure, temperature and time, optimum conditions for consolidation of the floc to > 90% theoretical density on a laboratory scale are found to be 22.5 MPa, 900°C for 10 minutes. Using a pressure of 15 MPa, at 900°C for 30 min., hot-pressed billets of BaSO4 have been made on a 5 kg scale. In going from the Magnox waste to the hot-pressed barium sulphate a volume reduction factor ∼ 18 is achieved. The principal phases in the product are found to be BaSO4 , MgO and Fe3O4, and the degree of consolidation achieved depends on the MgO content.The leaching behaviour of the hot-pressed materials in 100°C, 3 day Soxhlet tests also depends on the MgO content, and on the consequent level of open porosity. If there is porosity accessible to the leach water, MgO at the internal surfaces is converted to Mg(OH)2, which deposits within the pores, and a weight gain is registered in the Soxhlet test. If, however, there is no open porosity, a weight loss occurs, and leach rates ∼ 4 × 10−7 kg/m2/sec are found. In contrast, pure BaSO4, hot-pressed to similar densities, shows no variation in leaching behaviour over a wide range of o en porosities, and gives Soxhlet leach rates ∼ 8 × 10−8 kg/m2/sec.

Volume of Fluid Simulations of Copper Droplet Splat and Sensitivity to Modeling Methods

2021 ◽  
Author(s):  
Laurie A. Florio
Keyword(s):  
Computational Modeling ◽  
Volume Fraction ◽  
Liquid Droplet ◽  
Copper Substrate ◽  
Volume Of Fluid ◽  
Modeling Method ◽  
Courant Number ◽  
Geometric Conditions ◽  
Study Results ◽  
Wide Range

Abstract Liquid droplet interactions with solid surfaces are fundamental to a wide range of phenomena from novel manufacturing processes, ice accretion on surfaces, to ablation and fouling build-up when droplets are carried with fluid flow along a flow path. Computational fluid-dynamics based simulations offer a controlled environment in which to explore the details of the droplet motion, deformation, or break-up and solidification and melting as droplet impingement on a surface occurs. The operating, material, or geometric conditions can be altered and the resulting changes in the droplet related phenomena can be used to gain the information needed to control the droplet related processes for an intended purpose. The present work investigates the sensitivity of the predicted splat development as a single copper droplet impact upon a cool copper substrate to variations in a volume of fluid based computational modeling method. One liquid copper droplet is assigned an initial velocity and temperature and is set to impact a cold solid copper surface. The splat profile, as time progresses, is compared to the results in the literature. Among the computational modeling method changes investigated are the surface tension treatment, the solution method for the volume fraction equation, the volume fraction time sub-step calculation method, the volume fraction cut-off value and Courant number, the frequency of the volume fraction updates, the volume fraction discretization method, the mushy zone parameter, and mesh refinement. The study results can be used to provide information to aid in the generation of the models that can more accurately interrogate droplet-surface interactions.

scholarly journals Numerical Research of Flows into Gullies with Different Outlet Locations

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 794 ◽  
Author(s):  
Rita F. Carvalho ◽  
Pedro Lopes ◽  
Jorge Leandro ◽  
Luis M. David
Keyword(s):  
Surface Runoff ◽  
Discharge Coefficient ◽  
Drainage System ◽  
Flow Conditions ◽  
Hydraulic Behavior ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Flow Features ◽  
Numerical Research ◽  
Estimation Of Uncertainty

Gullies are sewer inlets placed in pavements usually covered by bar grates. They are the most common linking-element used to drain a wide range of flows from surface runoff into the buried drainage system. Their hydraulic behavior and their overall hydraulic performance is dependent on the flow conditions, the gully dimension, geometry, and location of the outlet device. Herein a numerical research based on Volume Of Fluid ( V O F ) to detect the interface, and on the Shear Stress Transport S S T k - ω turbulence model was conducted to study the importance of the outlet location and characterize flows through them in drainage conditions. Results provided detailed information about flow features, discharge coefficients, and efficiencies for different outlet locations. The authors identified three different regimes, R 1 , R 2 , and R 3 , and concluded that the outlet location influences the velocity field along the gully, the discharge coefficient, and the drainage efficiency. This allows for the estimation of uncertainty and its variation for different outlet positions.

scholarly journals Are there viable chemical and non-chemical alternatives to the use of conventional insecticides for the protection of young trees from damage by the large pine weevil Hylobius abietis L. in UK forestry?

2020 ◽  
Vol 93 (5) ◽  
pp. 694-712
Author(s):  
Ian H Willoughby ◽  
Roger Moore ◽  
Andrew J Moffat ◽  
Jack Forster ◽  
Imam Sayyed ◽  
...  
Keyword(s):  
Natural Product ◽  
Control Agent ◽  
Picea Sitchensis ◽  
Hylobius Abietis ◽  
Physical Barrier ◽  
Aquatic Life ◽  
Pyrethroid Insecticides ◽  
Pine Weevil ◽  
Wide Range ◽  
The Uk

Abstract In UK forestry, the synthetic pyrethroid insecticides alpha-cypermethrin and cypermethrin have been used for many years to provide protection for young trees planted on restock sites from damage by the large pine weevil, Hylobius abietis L. However, concerns over the toxicity of these insecticides to aquatic life if misused have led to a search for alternative forms of protection. This paper describes a detailed programme of efficacy experiments undertaken between 2009 and 2015 to find replacements for these products. Over 50 combinations of chemical and non-chemical approaches were tested on 16 different sites. Of the alternative synthetic insecticides tested, applications of 0.037 g a.i. stem−1 acetamiprid provided high levels of protection from Hylobius browsing damage on young Sitka spruce (Picea sitchensis (Bong.) Carrière) trees, without causing any phytotoxic symptoms, and gave comparable levels of protection to those achievable using alpha-cypermethrin or cypermethrin. Acetamiprid is less toxic to aquatic life than alpha-cypermethrin or cypermethrin and has not been linked to bee decline. Applications of 0.0129 g a.i. stem−1 chlorantraniliprole also showed promise, and this relatively low toxicity non-neonicotinoid insecticide merits further study. Although imidacloprid and thiacloprid also provided good levels of protection, their use in forests is not now permitted due to concerns over their potential impacts on bees and drinking water, respectively. Whilst the natural product insecticide spinosad, and the entomopathogenic fungal control agent Metarhizium anisopliae (Metschn.) Sorokin, gave only limited protection in our work, they may have some future potential if methods of deployment can be improved. Other chemical and non-chemical approaches tested, but found to be largely ineffective in UK conditions, included the natural product insecticides azadirachtin, maltodextrin and pyrethrins, the synthetic insecticides lambda-cyhalothrin and spirotetramat and a wide range of repellents, flexible stem coatings and physical barrier products. However, we conclude that physical barrier sleeves such as MultiPro® and BioSleeve® may have a limited role as a partial substitute for the use of insecticides in the UK in some circumstances, but only if on-site populations of Hylobius are predicted to be low.

Influential parameters on submerged discharge capacity of converging ogee spillways based on experimental study and machine learning-based modeling

2019 ◽  
Vol 21 (3) ◽  
pp. 474-492 ◽  
Author(s):  
Kiyoumars Roushangar ◽  
Ali Foroudi ◽  
Mojtaba Saneie
Keyword(s):  
Machine Learning ◽  
Discharge Capacity ◽  
Gene Expression Programming ◽  
Theoretical Concept ◽  
Visual Observation ◽  
Experimental Models ◽  
Machine Learning Techniques ◽  
Construction Operations ◽  
Effective Role ◽  
Submerged Discharge

Abstract Ogee spillways with converging training walls are applied to lower the hazard of accidental flooding in locations with limited construction operations due to their unique structure. Hence, this type of structure is proposed as an emergency spillway. The present study aimed at experimental and machine learning-based modeling of the submerged discharge capacity of the converging ogee spillway. Two experimental models of Germi-Chay dam spillway were utilized: one model having a curve axis which was made in 1:50 scale and the other with a straight axis in 1:75 scale. Using visual observation, it was found that the total upstream head, the submergence degree, the ogee-crest geometries and the convergence angle of training walls are the crucial factors which alter the submerged discharge capacity of the converging ogee spillway. Furthermore, two machine-learning techniques (e.g. artificial neural networks and gene expression programming) were applied for modeling the submerged discharge capacity applying experimental data. These models were compared with four well-known traditional relationships with respect to their basic theoretical concept. The obtained results indicated that the length ratio () had the most effective role in estimating the submerged discharge capacity.

Discharge coefficients for ogee weirs including the effects of a sloping upstream face

2020 ◽  
Vol 20 (4) ◽  
pp. 1493-1508 ◽  
Author(s):  
Farzin Salmasi ◽  
John Abraham
Keyword(s):  
Gene Expression ◽  
Experimental Data ◽  
Regression Analysis ◽  
Discharge Coefficient ◽  
Gene Expression Programming ◽  
Linear Interpolation ◽  
Performance Criteria ◽  
Upstream Face ◽  
Discharge Coefficients ◽  
Regression Techniques

Abstract Discharge coefficients (C0) for ogee weirs are essential factors for predicting the discharge-head relationship. The present study investigates three influences on the C0: effect of approach depth, weir upstream face slope, and the actual head, which may differ from the design head. This study uses experimental data with multiple non-linear regression techniques and Gene Expression Programming (GEP) models that are applied to introduce practical equations that can be used for design. Results show that the GEP method is superior to the regression analysis for predicting the discharge coefficient. Performance criteria for GEP are R2 = 0.995, RMSE = 0.021 and MAE = 0.015. Design examples are presented that show that the proposed GEP equation correlates well with the data and eliminates linear interpolation using existing graphs.

Experimental Studies of Pressure Drop and Flow Instability in Evaporative Micro-Channels

2008 ◽  
Author(s):  
Hee Joon Lee ◽  
Dongyao Liu ◽  
Shi-Chune Yao
Keyword(s):  
Pressure Drop ◽  
Flow Instability ◽  
Experimental Studies ◽  
Bond Number ◽  
Effective Length ◽  
Instability Criterion ◽  
Micro Channel ◽  
Micro Channels ◽  
Wide Range ◽  
Channel Systems

Experiments were conducted on evaporative micro-channel systems of water, containing 48 parallel channels of 353 μm hydraulic diameter. The general correlation of two-phase pressure drop for an initial design purpose of evaporative micro-channel systems reported in [1] has been validated. For the water boiling in micro-channels, flow instability was observed. The instability criterion, proposed by Kandlikar [2], is able to predict the water experimental results. However, further examination of his criterion revealed that it can not predict the results of Brutin and Tadrist’s data of n-pentane. This is because the Bond number of water is 0.01, but 0.33 for n-pentane. As a result, the growing bubble of n-pentane may not cover the whole length of the micro-channel. A general expression of the effective length of squeezed bubbles in micro-channel was established for fluids at a wide range of Bond number. Using this proposed effective length, the Brutin and Tadrist’s experimental instability data can also be predicted satisfactorily.

Experimental and Numerical Investigations on Basic Characteristics of High-Performance Abradable-Aero Hybrid Seal

2014 ◽  
Author(s):  
Yoshihiro Kuwamura ◽  
Kazuyuki Matsumoto ◽  
Hidekazu Uehara ◽  
Hiroharu Ooyama ◽  
Yoshinori Tanaka ◽  
...  
Keyword(s):  
Mass Flow ◽  
Vortex Structure ◽  
High Performance ◽  
Discharge Coefficient ◽  
Labyrinth Seal ◽  
Axial Position ◽  
Leakage Flow ◽  
Flow Measurements ◽  
Wide Range ◽  
Basic Characteristics

As key technologies to improve the performance of steam turbines, various types of high performance seal, such as active clearance control (ACC) seals and leaf seals [1], have been developed by Mitsubishi Heavy Industries, LTD (MHI). In recent years, a new seal concept using an aerodynamic approach called “aero seal” has also been developed, which remarkably reduces the leakage flow while maintaining fin clearances. Furthermore, more robust and higher performance sealing technology called “abradable-aero hybrid seal” which combines the aero seal concept with the abradable seal technology was proposed. The main concept of the aero seal is to control and utilize the vortex structure in the cavities of the labyrinth seal. In the cavities of the aero seal, the locally-controlled flow on the upstream side of the fin tip causes a strong contraction of the leakage flow and reduces the discharge coefficient significantly. This concept allows for a remarkably reduced leakage flow while maintaining fin clearances. Moreover, in order to achieve more robust and higher performance by minimizing the fin clearances, the abradable seal technology was applied to the aero seal concept. However, when the abradable seal is applied, the grooves may be formed on the wall surface of the abradable material due to rubbing of the fin into the abradable material. This situation leads to concern that the groove breaks the effective vortex structure of aero seal and causes negative effects on the seal performance. In this paper, the improved aero seal configuration consisting of slant fins was proposed and it was verified that the reduction in the discharge coefficient of improved aero seal is up to 40% compared to the conventional labyrinth seal. Furthermore, more robust and higher performance sealing technology called “abradable-aero hybrid seal” was proposed and basic characteristics such as the effects of the presence of grooves, the axial position of the fin and seal clearance on the leakage mass flow and the vortex structure were parametrically investigated both experimentally and numerically. In the experiments, not only leakage mass flow measurements but also PIV measurements were carried out in order to visualize the flow patterns in the cavity of the abradable-aero hybrid seal. From the results, it was confirmed that the effective vortex structures were formed even with grooves at various fin positions and the leakage flow can be stably reduced over 40% in a wide range of axial position and reduced by 50% at the optimum position.

Discharge Coefficients of Rotating Short Orifices With Radiused and Chamfered Inlets

2004 ◽  
Vol 126 (4) ◽  
pp. 803-808 ◽  
Author(s):  
M. Dittmann ◽  
K. Dullenkopf ◽  
S. Wittig
Keyword(s):  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Reynolds Numbers ◽  
Frame Of Reference ◽  
Efficient Operation ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Secondary Air ◽  
Cooling Air ◽  
Actual Geometry

The secondary air system of modern gas turbine engines consists of numerous stationary or rotating passages to transport the cooling air, taken from the compressor, to thermally high loaded components that need cooling. Thereby the cooling air has to be metered by orifices to control the mass flow rate. Especially the discharge behavior of rotating holes may vary in a wide range depending on the actual geometry and the operating point. The exact knowledge of the discharge coefficients of these orifices is essential during the design process in order to guarantee a well adapted distribution of the cooling air inside the engine. This is crucial not only for a safe and efficient operation but also fundamental to predict the component’s life and reliability. In this paper two different methods to correlate discharge coefficients of rotating orifices are described and compared, both in the stationary and rotating frame of reference. The benefits of defining the discharge coefficient in the relative frame of reference will be pointed out. Measurements were conducted for two different length-to-diameter ratios of the orifices with varying inlet geometries. The pressure ratio across the rotor was varied for rotational Reynolds numbers up to ReΦ=8.6×105. The results demonstrate the strong influence of rotation on the discharge coefficient. An analysis of the complete data shows significant optimizing capabilities depending on the orifice geometry.

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