Numerical, Experimental and Analytical Investigation of the Mass Outflow From a Pickling Tank

2004 ◽  
Author(s):  
Andreas Mehrle ◽  
Philipp Gittler ◽  
Mirko Javurek ◽  
Andreas Osterkorn
Keyword(s):  
Free Surface ◽  
Boundary Conditions ◽  
Scale Model ◽  
Small Scale ◽  
Intermediate Step ◽  
Order Of Growth ◽  
Cfd Simulations ◽  
Strip Surface ◽  
Vof Model ◽  
Mass Outflow

The process of pickling is an important intermediate step in the production line of steel processing. The strip surface is cleaned from grease and scales before further processing by immersion into an acid bath. Problems arising at higher process speeds with increasing inclination of the free surface are reduced strip immersion length and increased mass outflow. In this paper a differential equation is derived describing the influence of the bath depth on the local surface inclination for a simplified two-dimensional case. Since it can only be solved analytically for trivial boundary conditions a numerical solution has been computed giving an estimation for the order of growth of the bath inclination and mass outflow with the strip velocity. Further, a series of CFD simulations of the complete three-dimensional geometry at different strip velocities have been carried out calibrating the formulas of mass outflow. In the course of the CFD simulations the deformation of the free surface was calculated by a VOF model with explicit reconstruction of the interface. A standard κ–ε turbulence model was applied and special considerations have been made regarding the boundary conditions. Finally the resulting formula has been verified making use of data from a small scale model. It was found that the overflow at the far end of the tank is the dominant mass transfer mechanism at process velocities of the current generation of pickling tanks. Still, due to the superior order of growth, mass drag-out via the upper side of the strip becomes important for process velocities of 8 to 10 m/s. The good accordance of the analytical solution, CFD simulation and experiment indicate that the formula derived in the first part of the paper is a good estimation for the mass outflow from the pickling tank, hence making time and resource consuming CFD simulations obsolete for the design layout. Further the validity of geometrically non similar small scale models could be showed.

scholarly journals Numerical analysis on the performance of Dual Rotor wind turbine

2020 ◽  
Vol 8 (03) ◽  
pp. 352-368
Author(s):  
Hazem Ali Abdel Karim ◽  
Ahmed Reda El-Baz ◽  
Nabil Abdel Aziz Mahmoud ◽  
Ashraf Mostafa Hamed
Keyword(s):  
Wind Turbine ◽  
Rotational Speed ◽  
Pitch Angle ◽  
Numerical Study ◽  
Three Dimensional ◽  
Scale Model ◽  
Power Coefficient ◽  
Peak Performance ◽  
Small Scale ◽  
Cfd Simulations

This study investigates the aerodynamic performance of wind turbines aiming to maximize the power extracted from the wind. The study is focusing on the effect of introducing a second rotor to the main rotor of the wind turbine in what is called a dual rotor wind turbine (DRWT).  The numerical study took place on the performance of small-scale model of wind turbine of 0.9 m diameter using S826 airfoil. Both the Co-rotating and Counter rotating configurations were investigated at different tip speed ratios (TSR) and compared with the performance of the single rotor wind turbine (SRWT). Many parameters were studied for dual rotor turbines. These include the spacing between the two rotors, the pitch angle of the rear rotor and the rotational speed of ratio rear to front rotor. Three-dimensional simulations performed and employed using CFD simulations with Multi Reference Frame (MRF) technique. The Co Rotating Wind Turbine (CWT) and Counter Rotating Wind Turbine (CRWT) found to have better performance compared to that of the SRWT with an increase ranging from 12 to 14% in peak power coefficient. Moreover, the effect of changing the pitch angle of the rear rotor on the overall performance found to be of a negligible effect between angles 0⁰ until 2⁰ degrees tilting toward the front rotor. On the other hand, the ratio of rotational speed of the rear rotor to the front rotor found to cause a further increase in the peak performance of the CWT and CRWT ranging from 3 to 5%.

scholarly journals Decomposition technique for contributions to groundwater heads from inside and outside of an arbitrary boundary: Application to Guantao County, North China Plain

2019 ◽  
Author(s):  
Ning Li ◽  
Wolfgang Kinzelbach ◽  
Haitao Li ◽  
Wenpeng Li ◽  
Fei Chen
Keyword(s):  
Boundary Conditions ◽  
Numerical Models ◽  
Soil Column ◽  
Scale Model ◽  
Small Scale ◽  
Decomposition Technique ◽  
Arbitrary Boundary ◽  
Groundwater Head ◽  
Administrative Unit ◽  
Small Models

Abstract. To assess the efficiency of groundwater management of an administrative unit, we propose to decompose the groundwater head changes within an administrative unit into inside and outside contributions by using numerical models. Guantao County of Hebei Province, China, serves as an example to demonstrate the decomposition technique. The groundwater flow model of Guantao was constructed using observed heads as prescribed head boundary conditions. The model was coupled with Hydrus 1D, to calculate the groundwater recharge distribution in time reflecting the delay and damping effects of the soil column on seepage at the surface. The model was calibrated by adjusting parameters such as hydraulic conductivities, recharge infiltration ratios and specific yields. The calibrated parameters are then used in a large model with a boundary at large distance from Guantao administrative boundary to determine the groundwater head changes due to inside drivers. The differences of the two models on the Guantao boundary serve as the specified head values on the boundary for a small scale model, which is used to calculate the groundwater head imposed by outside drivers. To eliminate inconsistencies caused by the different types of boundary conditions of large and small models, the groundwater head changes due to inside drivers must be updated. The results indicate that the groundwater head changes in the centre and south of Guantao County are influenced equally by both inside and outside contributions, while in the north outside contributions have the stronger impact. The sensitivity analysis shows that the groundwater head changes and their decomposition are much more sensitive to infiltration ratios than to the aquifer parameters. The parameters within Guantao have a certain influence on the net groundwater head changes while the parameters outside of Guantao have only an influence on the decomposition.

Dynamic Response Analysis of Harbor Caisson Structure Under Various Boundary Conditions

2009 ◽  
Author(s):  
Jeong-Tae Kim ◽  
So-Young Lee ◽  
Dong-Soo Hong ◽  
Jin-Hak Yi ◽  
Yoon-Koo Kang
Keyword(s):  
Boundary Conditions ◽  
Frequency Response ◽  
Experimental Tests ◽  
Element Model ◽  
Dynamic Responses ◽  
Scale Model ◽  
Small Scale ◽  
Response Analysis ◽  
Fundamental Study ◽  
Various Boundary Conditions

In this study, vibration responses of harbor caisson structures with various boundary conditions are experimentally examined as a fundamental study to develop a health assessment technique for harbor structures. To achieve the objective, four-step approach is implemented. Firstly, a target caisson structure is selected and a small-scale model of the caisson model is constructed in the laboratory. Secondly, a finite element model of the caisson model is generated to analyze dynamic responses of the structure. Thirdly, experimental tests are performed on the caisson model to obtain dynamic responses under various boundary conditions and impact locations. Four different boundary conditions, 1) ‘hanging by crane’, 2) ‘standing on styrofoam block’, 3) ‘standing on sand mat’, and 4) ‘standing on concrete floor’ are considered. Finally, variation of frequency response ratio assurance criterion and correlation coefficients of frequency response functions are analyzed.

Numerical Calculations on Countercurrent Air-Water Flow in Small-Scale Models of a PWR Hot Leg Using a VOF Model

2009 ◽  
Author(s):  
Michio Murase ◽  
Yoichi Utanohara ◽  
Ikuo Kinoshita ◽  
Noritoshi Minami ◽  
Akio Tomiyama
Keyword(s):  
Heat Removal ◽  
Numerical Calculations ◽  
Scale Model ◽  
Small Scale ◽  
Countercurrent Flow ◽  
Two Phase Flows ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Vof Model ◽  
Inclined Pipe

In the case of loss of the residual heat removal (RHR) systems under mid-loop operation during shutdown of a PWR plant, reflux cooling by a steam generator (SG) is expected, and the generated steam in a reactor core and the condensed water in the SG form a countercurrent flow in a hot leg, which consists of a horizontal pipe, an elbow and an inclined pipe. In order to improve a countercurrent flow model of a transient analysis code, countercurrent air-water tests were conducted using the 1/15th scale model of the PWR hot leg at Kobe University and the authors conducted numerical calculations of the 1/15th scale tests using the thermal-hydraulic analysis code FLUENT6.3.26 and an Euler-Euler model or a VOF model. In the tests and calculations, however, the expansion of the inclined pipe in the PWR hot leg was not simulated. In this study, using the VOF model, the authors conducted numerical calculations for a 1/15th scale model of the PWR hot leg with the expansion of the inclined pipe, which mitigates CCFL (countercurrent flow limitation) there. The calculated flow patterns in the hot leg using the VOF model were quite different with the data for the 1/15th tests without the expansion of the inclined pipe due to underestimation of CCFL characteristics at the upper end of the inclined pipe, but became similar with the observed results for the 1/15th scale model with the expansion of the inclined pipe due to the mitigation of CCFL at the inclined pipe. The results indicate that the VOF model could not correctly calculate air-water two-phase flows at the upper part of the inclined pipe but could calculate two-phase flows in the horizontal pipe.

Transient Analysis of Mixed Free-Surface-Pressurized Flows With Modified Slot Model: Part 1 — Computational Model and Experiment

2003 ◽  
Author(s):  
Kazutoshi Arai ◽  
Katsuhiro Yamamoto
Keyword(s):  
Free Surface ◽  
Computational Model ◽  
Drainage System ◽  
Scale Model ◽  
Small Scale ◽  
Horizontal Pipe ◽  
Pressurized Flows ◽  
Calculation Results ◽  
Gas Liquid Flow ◽  
Entrapped Air

A new computational model is developed here to analyze the influence of entrapped air on free-surface-pressurized flows in a drainage system. A virtual slot with ceiling on the top of the pipe is introduced to treat a separated gas-liquid flow. This model is a modified model of Preissmann’s and is applicable not only to open channel flow and closed conduit flow but also pressurized flow with entrapped air. Compared to experimental results using the model of 1/50 scale of actual drainage system, the calculation results show that the entrapped air in a horizontal pipe advances the time of pressure rising and makes the maximum value of pressure higher. The escape flow of entrapped air at a dropshaft is caused by long waves pushing the air in the horizontal pipe, and then the pipe slope affects the flow rate of air. The air compressibility has less effect on the transient separated air-water flow in the small-scale model.

Wave Run-Up Simulations With a Moving Large Volume Semi-Submersible Platform

2011 ◽  
Author(s):  
Rafael de Andrade Watai ◽  
Fabio Tadao Matsumoto ◽  
Joa˜o Vicente Sparano ◽  
Alexandre Nicolaos Simos ◽  
Marcos Donato A. S. Ferreira
Keyword(s):  
Free Surface ◽  
Large Volume ◽  
Stokes Equations ◽  
Scale Model ◽  
Uniform Grid ◽  
Small Scale ◽  
Regular Waves ◽  
Wave Basin ◽  
Free Surface Displacement ◽  
Run Up

Since July 2008, the Numerical Offshore Tank (TPN) of the University of Sa˜o Paulo and Petrobras have been working on a research project intended to improve knowledge and modeling of advanced hydrodynamics topics, such as the wave run-up phenomenon. Among other activities, wave basin tests were performed with small-scale model of a large volume semi-submersible designed to operate in Campos Basin. These tests evidenced significant run-up effects on its squared-section columns for the steepest waves in several design conditions. In order to evaluate the difficulties involved in modeling the wave run-up phenomenon, simplified tests were also carried out with the model fixed and moored in regular waves with varying steepness. Previous studies using a 2nd order BEM model and a VOF CFD code to predict free-surface elevations below the deck under regular waves were presented in Matsumoto et al. (2010). The studies illustrated considerable differences between the wave elevation results in fixed and moored model setup; however, by that time, the analysis of the moored model by a VOF CFD code was not yet complete. This paper, therefore, presents wave run-up estimations with a moving large volume semi-submersible platform performed with the CFD code ComFLOW, which solves the Navier-Stokes equations employing a local height function to the free surface displacement. The phenomenon is investigated by simulating the flow around the semi-submersible model under the influence of high steepness regular waves on a non-uniform grid. Platform motions, derived from a first order BEM code, are imposed and synchronized with the incoming wave. Aiming at avoiding numerical wave reflections, a damping zone is also applied and positioned downstream the platform model. Predicted results are compared to experimental data, measured by seven vertical wave probes located in different positions below the model deck. Although considerably time-consuming, it will be shown that simulations present very good agreement with the experimental results.

scholarly journals Decomposition technique for contributions to groundwater heads from inside and outside of an arbitrary boundary: application to Guantao County, North China Plain

2019 ◽  
Vol 23 (7) ◽  
pp. 2823-2840 ◽  
Author(s):  
Ning Li ◽  
Wolfgang Kinzelbach ◽  
Haitao Li ◽  
Wenpeng Li ◽  
Fei Chen
Keyword(s):  
Boundary Conditions ◽  
Numerical Models ◽  
Soil Column ◽  
Scale Model ◽  
Small Scale ◽  
Decomposition Technique ◽  
Arbitrary Boundary ◽  
Groundwater Head ◽  
Administrative Unit ◽  
Small Models

Abstract. To assess the efficiency of the groundwater management of an administrative unit, we propose decomposing the groundwater head changes within an administrative unit into inside and outside contributions by using numerical models. Guantao County of Hebei Province, China, serves as an example to demonstrate the decomposition technique. The groundwater flow model of Guantao was constructed using observed heads as prescribed head boundary conditions. The model was coupled with Hydrus 1-D to calculate the groundwater recharge distribution in time reflecting the delay and damping effects of the soil column on seepage at the surface. The model was calibrated by adjusting parameters such as hydraulic conductivities, recharge infiltration ratios and specific yields. The calibrated parameters are then used in a large model with a boundary at a large distance from Guantao administrative boundary to determine the groundwater head changes due to inside drivers. The differences of the two models on the Guantao boundary serve as the specified head values on the boundary for a small-scale model, which is used to calculate the groundwater head imposed by outside drivers. To eliminate inconsistencies caused by the different types of boundary conditions of large and small models, the groundwater head changes due to inside drivers must be updated. The results indicate that the groundwater head changes in the center and south of Guantao County are influenced equally by both inside and outside contributions, while in the north outside contributions have the stronger impact. On average, 48.5 % of groundwater head changes in the whole of Guantao County is influenced by inside contributions, while 51.5 % is due to outside contributions. The sensitivity analysis shows that the groundwater head changes and their decomposition are much more sensitive to infiltration ratios than to the aquifer parameters. The parameters within Guantao have a certain influence on the net groundwater head changes, while the parameters outside of Guantao only have an influence on the decomposition.

RANCANG BANGUN PERANGKAT EKSPERIMENTASI PROSES PIROLISIS BIOMASA GELOMBANG MIKRO

2013 ◽  
Vol 14 (2) ◽  
Author(s):  
Noor Fachrizal
Keyword(s):  
Large Scale ◽  
Continuous Model ◽  
Biomass Energy ◽  
Scale Model ◽  
Small Scale ◽  
Laboratory Apparatus ◽  
Liquid Form ◽  
Large Scale Model ◽  
Bio Oil ◽  
Pyrolysis Of Biomass

Biomass such as agriculture waste and urban waste are enormous potency as energy resources instead of enviromental problem. organic waste can be converted into energy in the form of liquid fuel, solid, and syngas by using of pyrolysis technique. Pyrolysis process can yield higher liquid form when the process can be drifted into fast and flash response. It can be solved by using microwave heating method. This research is started from developing an experimentation laboratory apparatus of microwave-assisted pyrolysis of biomass energy conversion system, and conducting preliminary experiments for gaining the proof that this method can be established for driving the process properly and safely. Modifying commercial oven into laboratory apparatus has been done, it works safely, and initial experiments have been carried out, process yields bio-oil and charcoal shortly, several parameters are achieved. Some further experiments are still needed for more detail parameters. Theresults may be used to design small-scale continuous model of productionsystem, which then can be developed into large-scale model that applicable for comercial use.

scholarly journals Experimental Study on the Behavior of Existing Reinforced Concrete Multi-Column Piers under Earthquake Loading

2021 ◽  
Vol 11 (6) ◽  
pp. 2652
Author(s):  
Jung Han Kim ◽  
Ick-Hyun Kim ◽  
Jin Ho Lee
Keyword(s):  
Seismic Performance ◽  
Seismic Design ◽  
Bridge Piers ◽  
Scale Model ◽  
Inertia Force ◽  
Small Scale ◽  
Lap Splice ◽  
Existing Structures ◽  
Seismic Design Code ◽  
Seismic Force

When a seismic force acts on bridges, the pier can be damaged by the horizontal inertia force of the superstructure. To prevent this failure, criteria for seismic reinforcement details have been developed in many design codes. However, in moderate seismicity regions, many existing bridges were constructed without considering seismic detail because the detailed seismic design code was only applied recently. These existing structures should be retrofitted by evaluating their seismic performance. Even if the seismic design criteria are not applied, it cannot be concluded that the structure does not have adequate seismic performance. In particular, the performance of a lap-spliced reinforcement bar at a construction joint applied by past practices cannot be easily evaluated analytically. Therefore, experimental tests on the bridge piers considering a non-seismic detail of existing structures need to be performed to evaluate the seismic performance. For this reason, six small scale specimens according to existing bridge piers were constructed and seismic performances were evaluated experimentally. The three types of reinforcement detail were adjusted, including a lap-splice for construction joints. Quasi-static loading tests were performed for three types of scale model with two-column piers in both the longitudinal and transverse directions. From the test results, the effect on the failure mechanism of the lap-splice and transverse reinforcement ratio were investigated. The difference in failure characteristics according to the loading direction was investigated by the location of plastic hinges. Finally, the seismic capacity related to the displacement ductility factor and the absorbed energy by hysteresis behavior for each test were obtained and discussed.

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