Numerical simulation of sharp-crested weir flows

2009 ◽  
Vol 36 (9) ◽  
pp. 1530-1534 ◽  
Author(s):  
J. Qu ◽  
A.S. Ramamurthy ◽  
R. Tadayon ◽  
Z. Chen
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Open Channel ◽  
Flow Characteristics ◽  
Pressure Head ◽  
Flow Parameters ◽  
Weir Flow ◽  
Wide Range ◽  
And Control ◽  
Measurement And Control

The sharp-crested weir in a rectangular open channel can be used as a simple and accurate device for flow measurement and control in open channels. However, in the past, the solution to this problem was found mainly on the basis of experimental data or through the development of simplified theoretical expressions. In the present study, k-ε turbulence model is applied to obtain the flow parameters such as pressure head distributions, velocity distributions, and water surface profiles. The predictions of the proposed numerical model are validated using existing experimental data. The k-ε turbulence model developed is used to predict the characteristics of a sharp-crested weir in a rectangular open channel. The volume of fluid (VOF) scheme is used to find the shape of the free surface. A properly validated model permits one to obtain the flow characteristics of the sharp-crested weir for a wide range of weir and hydraulic parameters without recourse to expensive and more time consuming experimental methods. Further, the model permits one to incorporate small changes in the geometric parameters involving small changes in inlet and outlet conditions and study their impact on the weir flow characteristics.

Volume of fluid model for an open channel flow problem

2005 ◽  
Vol 32 (5) ◽  
pp. 996-1001 ◽  
Author(s):  
A S Ramamurthy ◽  
Junying Qu ◽  
Diep Vo
Keyword(s):  
Experimental Data ◽  
Channel Flow ◽  
Turbulence Model ◽  
Open Channel ◽  
Fluid Model ◽  
Open Channel Flow ◽  
Pressure Head ◽  
Volume Of Fluid ◽  
Vof Model ◽  
Free Overfall

In the past, the solutions to open flow problems were generally found on the basis of experimental data or through the development of theoretical expressions using simplified assumptions. The volume of fluid (VOF) turbulence model can be applied to obtain the flow parameters such as pressure head distributions, velocity distributions, and water surface profiles for flow in open channels. The free overfall in a rectangular open channel that serves as a discharge measuring structure is selected to apply to the VOF model. The predictions of the proposed VOF model are validated using existing experimental data for both subcritical and supercritical flow approach conditions. Based on the path followed by a fluid particle leaving the brink section, the equations for the nappe profiles in supercritical flows are obtained in terms of the end depth. The VOF turbulence model developed is used to predict the characteristics of a free overfall in a rectangular open channel.Key words: turbulence model, VOF model, numerical simulation, overfall characteristics, open channel flow.

VISCOSITY OF NATURAL RUBBER SOLUTIONS AT VERY LOW RATES OF SHEAR

1957 ◽  
Vol 35 (4) ◽  
pp. 381-387 ◽  
Author(s):  
Morton A. Golub
Keyword(s):  
Experimental Data ◽  
Natural Rubber ◽  
Pressure Head ◽  
Viscosity Data ◽  
Theoretical Relation ◽  
Newtonian Flow ◽  
Shear Rates ◽  
Reduced Viscosity ◽  
Wide Range ◽  
Composite Data

The shear dependence of viscosity of benzene solutions of natural rubber was studied at rates of shear from about 500 down to less than 1 sec.−1. Measurements involved following the change of pressure head with time of the various solutions flowing in a capillary, U-tube viscometer. Curvature in the plots of the logarithm of pressure head versus time indicated non-Newtonian flow. From such curves, reduced viscosity data over the above-mentioned shear range were readily derived. As a check, data over the range 100–500 sec.−1 were also obtained with a five-bulb viscometer of the Krigbaum–Flory type, and these data overlapped those obtained with the U tube. The reduced viscosity increased very sharply with decrease in gradient, making extrapolation to the viscosity axis quite unreliable. However, a theoretical relation proposed by Bueche fitted the composite data rather well. This work furnished a nice technique for determining the zero shear reduced viscosity (ηap/c)0 without the necessity of performing an uncertain extrapolation: evaluate the parameters of the Bueche formula which best satisfies the experimental data over a fairly wide range of shear rates, and then calculate (ηap/c)0 directly.

Smart Temperature Sensors

2019 ◽  
pp. 223-250
Author(s):  
Ashraf A. Zaher
Keyword(s):  
Weather Forecast ◽  
Temperature Sensors ◽  
Consumer Electronics ◽  
Data Logging ◽  
Industrial Processing ◽  
Wide Range ◽  
Scada Systems ◽  
New Generation ◽  
And Control ◽  
Measurement And Control

Many real-world applications depend on temperature sensing and/or control. This includes a wide range of industrial processes, chemical reactors, and SCADA systems, in addition to other physical, mechanical, and biological systems. With the advancement of technology, it became possible to produce a new generation of smart and compact temperature sensors, which are capable of providing digital outputs that are more accurate, robust, and easily interfaced and integrated into measurement and control systems. This chapter first surveys traditional analog temperature sensors, such as RTDs and thermocouples, to provide a strong motivation for the need to adopt better and smarter techniques that mainly rely on digital technology (e.g., CMOS designs). Different interfacing techniques that do not need ADCs are introduced, including the programmable Arduino microcontrollers. Different applications will be explored that include automotive accessories, weather forecast, healthcare, industrial processing, firefighting, and consumer electronics. Both wired and wireless technologies, including the IoT, will be investigated as means for transmitting the sensed data for further processing and data logging. A special case study to provide information redundancy in industrial SCADA systems will be analyzed to illustrate the advantages and limitations of smart temperature sensors. The chapter concludes with a summary of the design effort, accuracy, performance, and cost effectiveness of smart temperature sensors while highlighting future trends in this field for different applications.

Phenomenon of Fog Formation and Flow Characteristics of Droplet-Vapor-Gas Mixture in a Cooler-Condenser

2019 ◽  
Author(s):  
Hongfang Gu ◽  
Qiwei Guo ◽  
Changsong Li ◽  
Qing Zhou
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
High Speed ◽  
Flow Characteristics ◽  
Saturation Temperature ◽  
Bulk Temperature ◽  
Dropwise Condensation ◽  
Operation Conditions ◽  
Droplet Transport ◽  
Wide Range

Abstract Fog formation occurs in the process of condensation in the presence of non-condensable gas if the bulk temperature is lower than its saturation temperature (supersaturated). The phenomena of fogging is the formation of small condensate particles mixing with the vapor/gas stream, which creates potential problems of the vapor/gas/condensate separation and environmental pollution. Therefore, understanding of fogging mechanism and prevention of fog droplet entrainment are one of technical concerns for design and operation of cooler-condensers in the process industry. This paper presents the experimental study and numerical simulation of shell-side condensation with fog formation using a mixture of steam/non-condensable gas. The experimental data were collected on the two tube bundles (modified plastic tubes and stainless steel tubes). Using a high-speed photograph technique, the phenomenon of fog formation and flow characteristics of vapor/droplet transport were recorded over a wide range of test conditions. The numerical analysis of film and dropwise condensation, fog formation and droplet particle transport were simulated using different tube geometry and material, and flow velocity of air/droplet mixture. Based on simulation results, a new droplet trapping parameter is proposed to assess the optimal parameters of heat exchanger structural and operation conditions. Comparisons show that the numerical analysis results have a good agreement with experimental data and observations. These findings provide fundamental approach to account for the effect of fog formation, film and dropwise condensation, and droplet transport crossflow in cooler-condensers.

Study of Flow Characteristics and Control Circuit on High-Speed Solenoid Valve

2012 ◽  
Vol 619 ◽  
pp. 107-110 ◽  
Author(s):  
Wen Hua Li ◽  
Wen Lin Shao
Keyword(s):  
High Speed ◽  
Flow Characteristics ◽  
Pulse Signal ◽  
Solenoid Valve ◽  
Control Circuit ◽  
Duty Ratio ◽  
Time Sharing ◽  
Small Current ◽  
Wide Range ◽  
And Control

Through the analysis of the flow characteristics of the high-speed solenoid valve, the conclusions that the PWM signal duty ratio is the main factor affecting the solenoid valve flow is obtained, a new available any PWM pulse signal and control circuit are proposed. Further, circuit schematic is simulated by means of SIMULINK tools in MATLAB environment and Verify its stability. A time-sharing drive circuit is design based on the PWM drive mode. The driver circuit have function which is high-current open, small current maintain. Open current and maintain current of Solenoid valve can be adjusted through this circuit. Therefore, the circuit can adapt to different parameters of the solenoid valve. A wide range of applications.

scholarly journals METHOD OF PROCESSING EXPERIMENTAL DATA BY LINEAR FUNCTIONS OF VARIABLE LENGTH

2018 ◽  
pp. 74-82
Author(s):  
А. V. Zatylkin ◽  
D. A. Goluschko ◽  
Y. A. Varenik ◽  
E. S. Dementeva ◽  
B. L. Svistunov
Keyword(s):  
Experimental Data ◽  
Least Squares Method ◽  
Variable Length ◽  
Linear Functions ◽  
Practical Significance ◽  
Automated Processing ◽  
And Control ◽  
Measurement And Control ◽  
The Given ◽  
Accuracy Of Approximation

The purpose of the research is to increase the effectiveness of information and measurement and control systems of vibration testing equipment by introducing automated processing of experimental data allowing to extract with the required accuracy resonant bursts in the investigated amplitude-frequency characteristic section of the developed sample of a technical tool. To achieve this goal, a new method for processing experimental data by linear functions of variable length has been developed. The proposed method is based on the elements of the classical least squares method used to construct single approximating linear functions. The proposed method for processing experimental data differs from the known ones in that the number of linear approximating functions and their lengths vary depending on the required accuracy of approximation. The authors developed a mechanism for the formation of a sequence of linear functions on the considered segment, taking into account the given accuracy of approximation. The proposed mechanism is implemented in the form of algorithms, the description of which is presented in the work. Practical significance of the application of the developed method consists in reducing the processing time of the experimental data and obtaining the information necessary for the development engineers to provide a given level of strength and stability to external vibrational influences of the developed technical tools.

Numerical study of the flow field characteristics over a backward facing step using k-kl-ω turbulence model: comparison with different models

2018 ◽  
Vol 15 (1) ◽  
pp. 173-180 ◽  
Author(s):  
Yasser M. Ahmed ◽  
A.H. Elbatran
Keyword(s):  
Experimental Data ◽  
Fluid Mechanics ◽  
Turbulence Model ◽  
Flow Separation ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Numerical Results ◽  
Backward Facing Step ◽  
Content Type ◽  
Case Comparison

Purpose This paper aims to investigate numerically the turbulent flow characteristics over a backward facing step. Different turbulence models with hybrid computational grid have been used to study the detached flow structure in this case. Comparison between the numerical results and the available experiment data is carried out in the present study. The results of the different turbulence models were in a good agreement with the experimental results. The numerical results also concluded that the k-kl-ω turbulence model gave favorable results compared with the experiment. Design/methodology/approach It is very important to study the flow characteristics of detached flows. Therefore, the current study investigates numerically the flow characteristics in backward facing step by using two-, three- and seven-equation turbulence models in the finite volume code ANSYS Fluent. In addition, hybrid grid has been used to improve the capability of the unstructured mesh elements for predicting the flow separation in this case. Comparison between the different turbulence models and the available experimental data was done to find the most suitable turbulence model for simulating such cases of detached flows. Findings The present numerical simulations with the different turbulence models predicted efficiently the flow characteristics over the backward facing step. The transition k-kl-ω gave the best acceptable results compared with experimental data. This is a good concluded remark in the fields of fluid mechanics and hydrodynamics because the phenomenon of flow separation is not easy to be predicted numerically and can affect greatly on the predicted drag of moving bodies in many engineering applications. Originality/value The CFD results of using different turbulence models have been validated with the experimental work, and the results of k-kl-ω proven acceptable with flow characteristics. The results of the current study conclude that the use of k-kl-ω turbulence model will contribute towards a more efficient utilization in the fields of fluid mechanics and hydrodynamics.

Modeling of a Dry Dual Clutch Utilizing a Lever-Based Electromechanical Actuator

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Joško Deur ◽  
Milan Milutinović ◽  
Vladimir Ivanović ◽  
H. Eric Tseng
Keyword(s):  
Experimental Data ◽  
Computational Efficiency ◽  
Experimental Validation ◽  
Operating Parameters ◽  
Electromechanical Actuator ◽  
Model Parameterization ◽  
Clutch System ◽  
Wide Range ◽  
Modeling Accuracy ◽  
And Control

The paper proposes a dynamic model of an automotive dry dual clutch system, which comprises submodels of a lever-based electromechanical actuator and a dual clutch assembly. The model is developed by using the bond graph approach, and it can be used for clutch design, analysis, and control tasks. Special attention is devoted to modeling of friction, compliance, and lever geometry effects, as they are the ones that predominantly determine the accuracy of clutch static curve description and computational efficiency of the model. Several custom-designed test rigs are utilized for the purpose of collecting the experimental data needed for model parameterization and validation. Experimental validation demonstrates a good modeling accuracy for a wide range of operating parameters.

Laminar flow in rotating curved pipes

1996 ◽  
Vol 329 ◽  
pp. 373-388 ◽  
Author(s):  
Hiroshi Ishigaki
Keyword(s):  
Experimental Data ◽  
Laminar Flow ◽  
Friction Factor ◽  
Flow Structure ◽  
Flow Characteristics ◽  
Laminar Flows ◽  
Dean Number ◽  
Governing Parameter ◽  
Curved Pipes ◽  
Wide Range

When a curved pipe rotates about the centre of curvature, the fluid flowing in it is subjected to both Coriolis and centrifugal forces. Based on the analogy between laminar flows in stationary curved pipes and in orthogonally rotating pipes, the flow characteristics of fully developed laminar flow in rotating curved pipes are made clear and definite by similarity arguments, computational studies and using experimental data. Similarity arguments clarify that the flow characteristics in loosely coiled rotating pipes are governed by three parameters: the Dean number KLC, a body force ratio F and the Rossby number Ro. As the effect of Ro is negligible when Ro is large, computational results are presented for this case first, and then the effect of Ro is studied. Flow structure and friction factor are studied in detail. Variations of flow structure show secondary flow reversal at F ≈ −1, where the two body forces are of the same order but in opposite directions. It is also shown how the Taylor–Proudman effect dominates the flow structure when Ro is small. Computed curves of the friction factor for constant Dean number have their minimum at F ≈ −1. A composite parameter KL is introduced as a convenient governing parameter and used to correlate the characteristics. By applying KL to the analogy formula previously derived for two limiting flows, a semi-empirical formula for the friction factor is presented, which shows good agreement with the experimental data for a wide range of the parameters.

Numerical Evaluation of Novel Shaped Holes for Enhancing Film Cooling Performance

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Xing Yang ◽  
Zhao Liu ◽  
Zhenping Feng
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Film Cooling ◽  
Density Ratio ◽  
Cylindrical Hole ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Wide Range

The overall film cooling performance of three novel film cooling holes has been numerically investigated in this paper, including adiabatic film cooling effectiveness, heat transfer coefficients as well as discharge coefficients. The novel holes were proposed to help cooling injection spread laterally on a cooled endwall surface. Three-dimensional Reynolds-averaged Navier–Stokes (RANS) equations with shear stress transport (SST) k-ω turbulence model were solved to perform the simulation based on turbulence model validation by using the relevant experimental data. Additionally, the grid independent test was also carried out. With a mainstream Mach number of 0.3, flow conditions applied in the simulation vary in a wide range of blowing ratio from 0.5 to 2.5. The coolant-to-mainstream density ratio (DR) is fixed at 1.75, which can be more approximate to real typical gas turbine applications. The numerical results for the cylindrical hole are in good agreement with the experimental data. It is found that the flow structures and temperature distributions downstream of the cooling injection are significantly changed by shaping the cooling hole exit. For a low blowing ratio of 0.5, the three novel shaped cooling holes present similar film cooling performances with the traditional cylindrical hole, while with the blowing ratio increasing, all the three novel cooling holes perform better, of which the bean-shaped hole is considered to be the best one in terms of the overall film cooling performance.

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