A criterion for flow mechanisms through vertical sharp-edged orifice and model for the orifice discharge coefficient

According to the experimental data of the orifice discharge coefficient for the flow through a vertical sharp-edged orifice obtained in the previous study of this work,a theoretical criterion for flow mechanisms of small orifice（viz.thick-walled orifice and nozzle） and large orifice（viz.thin-walled orifice） was proposed based on the ratio of orifice diameter to plate thickness.It can help explain the dissipation of the mechanical energy loss in the flow process for the two flow mechanisms under different operating regimes.The main parameters such as orifice diameter,plate thickness and liquid head were correlated,and a semi-empirical model for orifice coefficient and an empirical model with high precision at the stable region were developed.

Three industries and wastewater and COD discharge of Beijing

With the swift development of economy, the water quality of Beijing is becoming worse day by day and hampers the sustainable development obviously. In this paper, the current conditions of the municipal wastewater structure in the industrial sectors are analysed and discussed in terms of the indicators, such as direct wastewater\|discharge coefficient, complete wastewater\|discharge coefficient, direct discharge coefficient of COD and complete discharge coefficient of COD, by taking a year of 1990s as the base year. Some countermeasures are studied and the corresponding recommendations are put forward in order to improve the water environment in Beijing. This provides a scientific ground for coordinating the relationship between the aquatic environment and economic growth in this city.

Generation and Discharge of Pollutants in Closed Aquaculture

[Objectives]To gain an in-depth understanding of pollutant generation and discharge from closed aquaculture.[Methods]In 2018,the pollutant generation and discharge coefficients of 7 farming modes in 16 farming bases were calculated and analyzed.[Results]A total of 28 pollutant generation coefficients and 28 pollutant discharge coefficients were obtained,and the generation and discharge of pollutants in closed aquaculture were grasped preliminarily.Compared with the data of the first census of pollutions sources published by the state in 2008,7 kinds of pollution generation coefficients increased,while 14 kinds decreased;and 4 kinds of pollutant discharge coefficients increased,while 17 kinds decreased.[Conclusions]In recent years,the pollutant generation and discharge coefficients of aquaculture show a decreasing trend.

Experimental Investigation of Discharge Capacity of Labyrinth Weirs with and without Nappe Breakers

Labyrinth weirs provide higher discharge capacity than conventional weirs, with the ability to pass large flows at comparatively low heads. Labyrinth weirs are primarily used as spillways for dams where the spillway width is restricted. In recent years, many research investigations have considered the hydraulic performance of labyrinth weirs, particularly as dependent on the geometric features. The previous work has improved the design basis for such weirs. However, their design still requires experimentally derived and generalized performance curves. It is especially important to observe the behavior of the weir nappe to ensure the design provides hydraulic optimization and to account for pressure fluctuations, possible vibrations, resonance effect, noise and flow surging. In the present study, discharge coefficients were experimentally determined for both circular labyrinth weirs and sharp crested trapezoidal labyrinth weirs of varying side wall angle (α). Additional studies were completed with nappe breakers included to reduce the impact of vibration on the labyrinth weirs. In general, the test data indicated that nappe breakers placed on the trapezoidal labyrinth weirs and circular labyrinth weirs reduced the discharge coefficient by up to 4% of the un-amended weir.

Experimental Investigation on Flow and Heat Transfer of Jet Impingement inside a Semi-Confined Smooth Channel

Experimental investigation is conducted to investigate the flow and heat transfer performances of jet impingement cooling inside a semi-confined smooth channel.Effects of jet Reynolds number(varied from 10 000to 45000),orifice-to-target spacing(zn=1d—4d)and jet-to-jet pitches(xn=3d—5d,yn=3d—5d)on the convective heat transfer coefficient and discharge coefficient are revealed.For a single-row jets normal impingement,the impingement heat transfer is enhanced with the increase of impingement Reynolds number or the decrease of spanwise jet-to-jet pitch.The highest local heat transfer is achieved when zn/dis 2.For the double-row jets normal impingement,the laterally-averaged Nusselt number distributions in the vicinity of the first row jets impinging stagnation do not fit well with the single-row case.The highest local heat transfer is obtained when zn/dis 1.A smaller jetto-jet pitch generally results in a lower discharge coefficient.The discharge coefficient in the double-row case is decreased relative to the single-row case at the same impingement Reynolds number.

A swirling jet from a nozzle with tangential inlets and its characteristics in breaking-up rocks

In order to apply a swirling jet to a PDC drill bit, the nozzle performance influenced by nozzle inlet geometric parameters and rock breaking tests under submerged conditions were studied. Numerical simulation was used to study the influence of the nozzle structure on the swirling intensity and nozzle discharge coefficient. Simulation results indicate that spreading angle of the swirling jet is greater than that of＂ the non-swirling jet, and the swirling intensity of the jet is strongly influenced by the length of the nozzle body but weakly by the number of tangential inlets. Rock breaking tests were conducted to evaluate the performance of the swirling jet. It is found that the swirling jet shows a lower threshold pressure to break the rock samples and could break rock more efficiently compared with the non-swirling jet.

Experimental and numerical analysis of flow over a rectangular full-width sharp-crested weir

Weirs are a type of hydraulic structure, used for water level adjustment, flow measurement, and diversion of water in irrigation systems. In this study, experiments were conducted on sharp-crested weirs under free-flow conditions and an optimization method was used to determine the best form of the discharge coefficient equation based on the coefficient of determination （R2） and root mean square error （RMSE）. The ability of the numerical method to simulate the flow over the weir was also investigated using Fluent software. Results showed that, with an increase of the ratio of the head over the weir crest to the weir height （h/P）, the discharge coefficient decreased nonlinearly and reached a constant value of 0.7 for hiP 〉 0.6. The best form of the discharge coefficient equation predicted the discharge coefficient well and percent errors were within a ±5% error limit. Numerical results of the discharge coefficient showed strong agreement with the experimental data. Variation of the discharge coefficient with Reynolds numbers showed that the discharge coefficient reached a constant value of 0.7 when hiP 〉 0.6 and Re 〉 20000.

Structure and Flow Characteristics of Flat Fan Nozzles with a Single Orifice Formed by a Rectangular Cut

The flat fan nozzle with a single orifice formed by a rectangular cut at the nozzle exit through a semi-ellipsoid blind end was developed. The flow rate characteristic of the nozzle was analyzed. Theoretical analysis shows that the discharge coefficient of the nozzle is a function of the ratio of the projected exit flow area to the cross sectional area of the nozzle input section. Water spraying experiment results show that the discharge coefficient increases with the increase of the ratio of the projected exit flow area to the cross sectional area of the nozzle input section when the rectangular cut depth doesn't exceed the distance from the center of the hemisphere to the nozzle end; conversely,the discharge coefficient decreases with the increase of the ratio; for a given nozzle,the discharge coefficient varies with Reynolds number.

Numerical Investigation of Flow and Heat Transfer in Vane Impingement/Effusion Cooling with Various Rib/Dimple Structure

By investigating heat transfer and flow structures of dimples,orthogonal ribs,and V-shaped ribs in the impingement/effusion cooling,the article is dedicated to selecting a best-performing internal cooling structure for a turbine vane.The overall cooling effectiveness and coolant consumption are adopted to evaluate the cooling performance.To analyze the influence of structural modification,the flow field is investigated on chordwise/spanwise sections and the target surface.The blockage effect on crossflow can protect jet flow,resulting in higher heat transfer performance of the target surface.Ribs own a stronger blockage effect than dimples.Compared with the blockage effect,the influence of the rib shape is negligible.By installing dimples between ribs,heat transfer is augmented further.The introduction of ribs/dimples leads to higher discharge coefficients of jet nozzles but lower discharge coefficients of film holes.Thus,the film cooling deteriorates.Meanwhile,the installation of the ribs and dimples decreases total coolant consumption.The effect of ribs/dimples on heat transfer and effusion condition of internal and external cooling is analyzed.The best-performing cooling structure is the target surface with dimples and orthogonal ribs,which decreases the wall temperature and coolant consumption by 14.57-28.03 K and 1.19%-1.81%respectively.This article concludes the flow mechanism for dimples and influence factors on the cooling performance,which may serve as guidance for the turbine vane design.

Investigation of Interacting Mechanism between Film Cooling and Internal Cooling Structures of Turbine Blade

This paper presents three-dimensional numerical simulations with the established realizable k-εmodel to clarify the underlying and interacting mechanisms between the film cooling and the internal cooling.On the one hand,the effects of three different internal cooling channels,i.e.,smooth channel,continuous ribbed channel,and truncated ribbed channel,on the film cooling effectiveness and the discharge coefficients are investigated.On the other hand,the influences of three different film cooling holes,i.e.,cylindrical hole,two elliptical holes and two circular-to-elliptical holes,on the heat transfer performances and pressure loss of the internal cooling channel are revealed.Especially,the suction effects of the film cooling holes are analyzed through setting up baselines with only internal cooling channels.Results show that the placement of ribs in the internal channel has different influences on the film cooling effectiveness with respect to different hole shapes depending on the blowing ratio.The discharge coefficient of the film hole can be improved by introducing ribs to the internal channel.Suction of film hole is helpful for enhancing the heat transfer performance and reducing the pressure loss of the internal channel.Besides,ribs instead of the suction effect of film hole play a major role to enhance the heat transfer performance in the internal cooling channel.

Drag prediction method of powered-on civil aircraft based on thrust drag bookkeeping

A drag prediction method based on thrust drag bookkeeping（TDB） is introduced for civil jet propulsion/airframe integration performance analysis.The method is derived from the control volume theory of a powered-on nacelle.Key problem of the TDB is identified to be accurate prediction of velocity coefficient of the powered-on nacelle.Accuracy of CFD solver is validated by test cases of the first AIAA Propulsion Aerodynamics Workshop.Then the TDB method is applied to thrust and drag decomposing of a realistic aircraft.A linear relation between the computations assumed free stream Mach number and the velocity coefficient result is revealed.The thrust losses caused by nozzle internal drag and pylon scrubbing are obtained by the isolated nacelle and mapped on to the in-flight whole configuration analysis.Effects of the powered-on condition are investigated by comparing through-flow configuration with powered-on configuration.The variance on aerodynamic coefficients and pressure distribution is numerically studied.

Experimental study on film cooling performance of imperfect holes

An experimental study is made to investigate the film cooling performance of imperfect holes due to in-hole blockage over a flat plate. A specifically pyramid-shaped element is used to simulate the in-hole blockage. Six in-hole blockage orientations（such as leading-inlet, leading-middle,leading-exit, trailing-inlet, trailing-middle and trailing-exit） and four blocking ratios（ranging from 0.1 to 0.4） are taken into considerations. Based on the experimental results, the influences of in-hole blockage on the film cooling effectiveness and discharge coefficient under typical blowing ratios are analyzed. It is confirmed that the in-hole blockage results in a reduction of discharge coefficient related to the perfect film cooling holes, especially for the leading-exit and trailing-inlet orientations with a big blocking ratio. However, in the view of film cooling effectiveness, the in-hole blockage shows complicated affecting roles. In general, except for the leading-exit orientation, the in-hole blockages produce detrimental influence on the film cooling effectiveness.

Computational fluid dynamic(CFD)simulation of pilot operated intermittent gas lift valve

To design an efficient intermittent gas-lift installation,reliable information is needed in the performance of all process components,from the outer boundary of the reservoir to the surface separators.The gas lift valve is the one critical component that affects the design of the whole system.In intermittent producing system,the pilot gas-lift valve is extremely used to control the point of compressed gas entry into the production tubing and acts as a pressure regulator.A novel approach using computational fluid dynamics simulation was performed in this study to develop a dynamic model for the gas passage performance of a 1-in.,Nitrogen-charged,pilot gas-lift valve.Dynamic performance curves were obtained by using Methane as an injection gas with flow rates reaching up to 4.5 MMscf/day.This study investigates the effect of internal pressure,velocity and temperature distribution within the pilot valve that cannot be predicted in the experiments and mathematical models during the flow-performance studies.A general equation of the nonconstant discharge coefficient has been developed for 1-inch pilot valve to be used for further calculation in the industry without using CFD model.The developed model significantly reduces the complexity of the data required to calculate the discharge coefficient.

Numerical simulation on a film-cooled rotating model with 30° injection holes

The flow and heat transfer characteristics were numerically investigated on a film cooling model under different rotating operating conditions.The computational model was originated from the mid-span section of a typical turbine rotor with two rows of 14 staggered injection holes angled 30° both on the suction surface and pressure surface,and the flow through the coolant plenum and all the hole-pipes were resolved as a part of the computational domain by specifying the coolant mass flux in the plenum.The computations primarily focus on under-standing the rotational effect on film cooling performance in mechanism research approach.In the present study,the Reynolds number(Re) based on mainstream velocity and injection hole diameter varied from 1835.5 to 5507.4,and the averaged blowing ratio(M) ranges of 0.5 to 1.5.Results show that the coolant will move on to the high-radius locations near the suction and pressure surfaces due to the strong centrifugal effect,which leads to the decrease in adiabatic effectiveness accordingly.The discharge coefficients(Cd),on the pressure surface,are much higher than that on the suction surface under a given operating condition.In addition,the critical values of angular speed which represent the equilibrium of centrifugal force and Coriolis force near the pressure surface are also presented.

Experimental and Numerical Investigation of Impingement Heat Transfer on Target Plate with Streamlined Roughness Element at Maximum Crossflow Condition

A combined experimental and numerical investigation of the heat transfer and flow characteristics of the roughened target plate has been conducted.All the data are compared with the flat plate.Three novel streamlined roughness elements are proposed:similar round protuberance,similar trapezoidal straight rib,and similar trapezoidal curved rib.The experiments are carried out in a perspex model using the transient thermochromic liquid crystal method.The effect of jet Reynolds number,rib height,and rib shape on the Nusselt number and flow discharge coefficient has been investigated.Higher ribs provide higher heat transfer enhancement.The curved ribs provide better heat transfer performance.Within the experimental scope,combined straight rib plate and combined curved rib plate increase the area averaged Nusselt number by 11.5%and 13.8%respectively.The experiment is complemented by a numerical part,which can provide flow field analysis and the Nusselt number on the surface of the small size roughness element.The numerical results show the protuberance can shorten the nozzle to plate distance and make the shifting point move forward.The ribs have a guidance effect on crossflow and reduce the transverse interference to the downstream jet.The transferred heat flux caused by the side surface of the roughness element is very obvious.The heat flux contributed by the side surface of the protuberance and ribs can reach 26%and 10%respectively.