scholarly journals Approach and Development of Effective Models for Simulation of Thermal Stratification and Mixing Induced by Steam Injection into a Large Pool of Water

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Hua Li ◽  
Walter Villanueva ◽  
Pavel Kudinov
Keyword(s):  
Thermal Stratification ◽  
Large Scale ◽  
Steam Injection ◽  
Small Time ◽  
Small Scale ◽  
Computationally Efficient ◽  
Thermal Mixing ◽  
Large Pool ◽  
Effective Models ◽  
Contact Condensation

Steam venting and condensation in a large pool of water can lead to either thermal stratification or thermal mixing. In a pressure suppression pool (PSP) of a boiling water reactor (BWR), consistent thermal mixing maximizes the capacity of the pool while the development of thermal stratification can reduce the steam condensation capacity of the pool which in turn can lead to pressure increase in the containment and thereafter the consequences can be severe. Advanced modeling and simulation of direct contact condensation in large systems remain a challenge as evident in commercial and research codes mainly due to small time-steps necessary to resolve contact condensation in long transients. In this work, effective models, namely, the effective heat source (EHS) and effective momentum source (EMS) models, are proposed to model and simulate thermal stratification and mixing during a steam injection into a large pool of water. Specifically, the EHS/EMS models are developed for steam injection through a single vertical pipe submerged in a pool under two condensation regimes: complete condensation inside the pipe and chugging. These models are computationally efficient since small scale behaviors are not resolved but their integral effect on the large scale flow structure in the pool is taken into account.

scholarly journals Validation of Effective Models for Simulation of Thermal Stratification and Mixing Induced by Steam Injection into a Large Pool of Water

2014 ◽  
Vol 2014 ◽  
pp. 1-18 ◽  
Author(s):  
Hua Li ◽  
Walter Villanueva ◽  
Markku Puustinen ◽  
Jani Laine ◽  
Pavel Kudinov
Keyword(s):  
Temperature Distribution ◽  
Heat Source ◽  
Water Level ◽  
Thermal Stratification ◽  
Steam Injection ◽  
Vertical Temperature ◽  
Large Pool ◽  
Order Scheme ◽  
Effective Models ◽  
Vertical Temperature Distribution

The Effective Heat Source (EHS) and Effective Momentum Source (EMS) models have been proposed to predict the development of thermal stratification and mixing during a steam injection into a large pool of water. These effective models are implemented in GOTHIC software and validated against the POOLEX STB-20 and STB-21 tests and the PPOOLEX MIX-01 test. First, the EHS model is validated against STB-20 test which shows the development of thermal stratification. Different numerical schemes and grid resolutions have been tested. A48×114grid with second order scheme is sufficient to capture the vertical temperature distribution in the pool. Next, the EHS and EMS models are validated against STB-21 test. Effective momentum is estimated based on the water level oscillations in the blowdown pipe. An effective momentum selected within the experimental measurement uncertainty can reproduce the mixing details. Finally, the EHS-EMS models are validated against MIX-01 test which has improved space and time resolution of temperature measurements inside the blowdown pipe. Excellent agreement in averaged pool temperature and water level in the pool between the experiment and simulation has been achieved. The development of thermal stratification in the pool is also well captured in the simulation as well as the thermal behavior of the pool during the mixing phase.

scholarly journals A Multidimensional and Multiscale Model for Pressure Analysis in a Reservoir-Pipe-Valve System

2018 ◽  
Author(s):  
Feng Jie Zheng ◽  
Fu Zheng Qu ◽  
Xue Guan Song
Keyword(s):  
Pressure Fluctuation ◽  
Large Scale ◽  
Three Dimensional ◽  
Industrial Process ◽  
Multiscale Model ◽  
Computational Time ◽  
Small Scale ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Proposed Model

Reservoir-pipe-valve (RPV) systems are widely used in many industrial process. The pressure in an RPV system plays an important role in the safe operation of the system, especially during the sudden operation such as rapid valve opening/closing. To investigate the pressure especially the pressure fluctuation in an RPV system, a multidimensional and multiscale model combining the method of characteristics (MOC) and computational fluid dynamics (CFD) method is proposed. In the model, the reservoir is modeled by a zero-dimensional virtual point, the pipe is modeled by a one-dimensional MOC, and the valve is modeled by a three-dimensional CFD model. An interface model is used to connect the multidimensional and multiscale model. Based on the model, a transient simulation of the turbulent flow in an RPV system is conducted, in which not only the pressure fluctuation in the pipe but also the detailed pressure distribution in the valve are obtained. The results show that the proposed model is in good agreement with the full CFD model in both large-scale and small-scale spaces. Moreover, the proposed model is more computationally efficient than the CFD model, which provides a feasibility in the analysis of complex RPV system within an affordable computational time.

scholarly journals A Multidimensional and Multiscale Model for Pressure Analysis in a Reservoir-Pipe-Valve System

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Feng Jie Zheng ◽  
Chao Yong Zong ◽  
William Dempster ◽  
Fu Zheng Qu ◽  
Xue Guan Song
Keyword(s):  
Large Scale ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Multiscale Model ◽  
Computational Time ◽  
Small Scale ◽  
Dimensional System ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Proposed Model

Reservoir-pipe-valve (RPV) systems are widely used in many industrial processes. The pressure in an RPV system plays an important role in the safe operation of the system, especially during the sudden operations such as rapid valve opening or closing. To investigate the pressure response, with particular interest in the pressure fluctuations in an RPV system, a multidimensional and multiscale model combining the method of characteristics (MOC) and computational fluid dynamics (CFD) method is proposed. In the model, the reservoir is modeled as a zero-dimensional virtual point, the pipe is modeled as a one-dimensional system using the MOC, and the valve is modeled using a three-dimensional CFD model. An interface model is used to connect the multidimensional and multiscale model. Based on the model, a transient simulation of the turbulent flow in an RPV system is conducted in which not only the pressure fluctuation in the pipe but also the detailed pressure distribution in the valve is obtained. The results show that the proposed model is in good agreement when compared with a high fidelity CFD model used to represent both large-scale and small-scale spaces. As expected, the proposed model is significantly more computationally efficient than the CFD model. This demonstrates the feasibility of analyzing complex RPV systems within an affordable computational time.

scholarly journals Filtering the Stochastic Skeleton Model for the Madden–Julian Oscillation

2016 ◽  
Vol 144 (2) ◽  
pp. 501-527 ◽  
Author(s):  
Nan Chen ◽  
Andrew J. Majda
Keyword(s):  
Large Scale ◽  
Warm Pool ◽  
Model Error ◽  
Small Scale ◽  
Fast Wave ◽  
Madden Julian Oscillation ◽  
Computationally Efficient ◽  
Skeleton Model ◽  
Spatially Extended ◽  
Novel Strategy

Abstract The filtering and prediction of the Madden–Julian oscillation (MJO) and relevant tropical waves is a contemporary issue with significant implications for extended range forecasting. This paper examines the process of filtering the stochastic skeleton model for the MJO with noisy partial observations. A nonlinear filter, which captures the inherent nonlinearity of the system, is developed and judicious model error is included. Despite its nonlinearity, the special structure of this filter allows closed analytical formulas for updating the posterior states and is thus computationally efficient. A novel strategy for adding nonlinear observational noise to the envelope of convective activity is designed to guarantee its nonnegative property. Systematic calibration based on a cheap single-column version of the stochastic skeleton model provides a practical guideline for choosing the parameters in the full spatially extended system. With these column-tuned parameters, the full filter has a high overall filtering skill for Rossby waves but fails to recover the small-scale fast-oscillating Kelvin and moisture modes. An effectively balanced reduced filter involving a simple fast-wave averaging strategy is then developed, which greatly improves the skill of filtering the moisture modes and other fast-oscillating modes and enhances the total computational efficiency. Both the full and the reduced filters succeed in filtering the MJO and other large-scale features with both homogeneous and warm pool cooling/moistening backgrounds. The large bias in filtering the solutions by running the perfect model with noisy forcing is due to the noise accumulation, which indicates the importance of including judicious model error in designing filters.

scholarly journals Non-local dispersion and the reassessment of Richardson's t3-scaling law

2021 ◽  
Vol 932 ◽  
Author(s):  
G.E. Elsinga ◽  
T. Ishihara ◽  
J.C.R. Hunt
Keyword(s):  
Large Scale ◽  
Scaling Law ◽  
Taylor Dispersion ◽  
Small Time ◽  
Inertial Range ◽  
Small Scale ◽  
Mean Square ◽  
Dispersion Regime ◽  
Non Local ◽  
Scale Properties

The Richardson-scaling law states that the mean square separation of a fluid particle pair grows according to t3 within the inertial range and at intermediate times. The theories predicting this scaling regime assume that the pair separation is within the inertial range and that the dispersion is local, which means that only eddies at the scale of the separation contribute. These assumptions ignore the structural organization of the turbulent flow into large-scale shear layers, where the intense small-scale motions are bounded by the large-scale energetic motions. Therefore, the large scales contribute to the velocity difference across the small-scale structures. It is shown that, indeed, the pair dispersion inside these layers is highly non-local and approaches Taylor dispersion in a way that is fundamentally different from the Richardson-scaling law. Also, the layer's contribution to the overall mean square separation remains significant as the Reynolds number increases. This calls into question the validity of the theoretical assumptions. Moreover, a literature survey reveals that, so far, t3 scaling is not observed for initial separations within the inertial range. We propose that the intermediate pair dispersion regime is a transition region that connects the initial Batchelor- with the final Taylor-dispersion regime. Such a simple interpretation is shown to be consistent with observations and is able to explain why t3 scaling is found only for one specific initial separation outside the inertial range. Moreover, the model incorporates the observed non-local contribution to the dispersion, because it requires only small-time-scale properties and large-scale properties.

scholarly journals Levee Breaching: A New Extension to the LISFLOOD-FP Model

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 942
Author(s):  
Iuliia Shustikova ◽  
Jeffrey C. Neal ◽  
Alessio Domeneghetti ◽  
Paul D. Bates ◽  
Sergiy Vorogushyn ◽  
...  
Keyword(s):  
Large Scale ◽  
Extreme Event ◽  
Flood Hazard ◽  
Maximum Flow ◽  
Small Scale ◽  
Economic Damage ◽  
Computationally Efficient ◽  
Po River ◽  
Efficient Manner ◽  
Critical Success

Levee failures due to floods often cause considerable economic damage and life losses in inundated dike-protected areas, and significantly change flood hazard upstream and downstream the breach location during the event. We present a new extension for the LISFLOOD-FP hydrodynamic model which allows levee breaching along embankments in fully two-dimensional (2D) mode. Our extension allows for breach simulations in 2D structured grid hydrodynamic models at different scales and for different hydraulic loads in a computationally efficient manner. A series of tests performed on synthetic and historic events of different scale and magnitude show that the breaching module is numerically stable and reliable. We simulated breaches on synthetic terrain using unsteady flow as an upstream boundary condition and compared the outcomes with an identical setup of a full-momentum 2D solver. The synthetic tests showed that differences in the maximum flow through the breach between the two models were less than 1%, while for a small-scale flood event on the Secchia River (Italy), it was underestimated by 7% compared to a reference study. A large scale extreme event simulation on the Po River (Italy) resulted in 83% accuracy (critical success index).

Steam Jet Condensation in a Pool: From Fundamental Understanding to Engineering Scale Analysis

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Chul-Hwa Song ◽  
Seok Cho ◽  
Hyung-Seok Kang
Keyword(s):  
Thermal Stratification ◽  
Hot Spot ◽  
Global Analysis ◽  
Turbulent Jet ◽  
Local Behavior ◽  
Dynamic Features ◽  
Water Pool ◽  
Thermal Mixing ◽  
Fundamental Understanding ◽  
Contact Condensation

The phenomena of direct contact condensation (DCC) of a steam jet submerged in a water pool occur because of the actuation of steam discharging devices in many industrial processes. There are practically two kinds of technical concerns to consider. The first is the thermal mixing in the water pool, and the other is the thermo-hydraulically induced mechanical loads acting on the structures of relevant systems. The two concerns are inter-related and can be well described only if the local behavior of the condensing steam jets and the resultant turbulent jet in a pool are well understood. In this paper, the DCC-related thermofluid dynamic features are discussed focusing on these two concerns. The fundamental characteristics of condensing steam jets are discussed, including the local behavior of condensing jets and the resultant turbulent jet, both of which importantly affect the macroscopic circulation in a pool. Then, a global analysis of thermal mixing in a pool from the viewpoints of the local hot spot and the thermal stratification are discussed with practical application to engineering design in mind.

Development of Effective Momentum Model for Steam Injection Through Multi-Hole Spargers: Unit Cell Model

2021 ◽  
Author(s):  
Xicheng Wang ◽  
Dmitry Grishchenko ◽  
Pavel Kudinov
Keyword(s):  
Boundary Conditions ◽  
Thermal Stratification ◽  
Cell Model ◽  
Steam Injection ◽  
Unit Cell ◽  
Water Interface ◽  
Unit Cell Model ◽  
Source Terms ◽  
Steam Condensation ◽  
Large Pool

Abstract The Steam injection through multi-hole spargers into the pressure suppression pool (PSP) is used in light water reactors to prevent containment over-pressure. The development of thermal stratification in the PSP can reduce its cooling capacity and results in higher containment pressures compared to completely mixed pool conditions. Explicit modelling of direct contact condensation (DCC) of steam at the steam-water interface is a challenge for contemporary codes. Effective Heat Source (EHS) and Effective Momentum Source (EMS) models have been proposed to enable the prediction of thermal stratification and mixing transients induced by steam condensation in a large pool. The general idea of the EHS/EMS is to resolve the effect of the DCC phenomena on a large pool, instead of explicit modelling of the small-scale phenomena at steam-water interface. The EHS/EMS models can be implemented using (i) respective boundary conditions at the boundary of the Steam Condensation Region (SCR) or (ii) using source terms in the heat and momentum transport equations. In previous work, EHS/EMS models were implemented using the second approach and validated against data from PPOOLEX and PANDA tests. It was found that results are sensitive to the spatial distribution of the source terms. Since the current data are not sufficient to provide a reasonable distribution, a preliminary study of the first method was done in this paper. The goal of this work is to develop a ‘Unit Cell’ model by using respective boundary conditions for steam injection through multi-hole sparger. The condensed turbulent jet is resolved by introducing the liquid jet with the same effective momentum and heat as the injected steam. A uniform velocity profile solved by EMS model and the temperature boundary solved by EHS model is provided on each injection hole of the sparger wall. Validation is conducted against sparger test in PANDA facilities.

Thermal Field of Twin Variably Elevated Tandem Jets in Crossflow

2014 ◽  
Vol 348 ◽  
pp. 155-161 ◽  
Author(s):  
Amina Radhouane ◽  
Nejla Mahjoub Said ◽  
Hatem Mhiri ◽  
Georges Le Palec ◽  
Philippe Bournot
Keyword(s):  
Power Plants ◽  
Large Scale ◽  
Electronic Devices ◽  
Reynolds Stress Model ◽  
Joint Effect ◽  
Uniform Grid ◽  
Small Scale ◽  
Thermal Mixing ◽  
Turbulent Closure ◽  
Volume Method

Consideration is given to twin inline elliptical fume jets issuing within an oncoming cooler environmental crossflow. Jets are emitted from similar nozzles, characterized by a variable injection height. Such a configuration is found at large scale, in the industrial urban zones, and more particularly in multiple chimney power plants. It is found at small scale as well like in cooling in electronic devices. The present study is carried out numerically by means of the finite volume method together with the Reynolds Stress Model (RSM) second order turbulent closure model and non uniform grid system particularly refined around the emitting nozzles. Emphasis is put on the temperature distribution around the emitting nozzles in order to highlight the joint effect of the jets elevation and temperature. It was mainly found that both parameters are complementary and help straitening the discharged jets, leading their thermal mixing away from the injection ground. Nomenclature

Small-Scale Science to Large-Scale Profession

2000 ◽  
Vol 45 (4) ◽  
pp. 396-398
Author(s):  
Roger Smith
Keyword(s):  
Large Scale ◽  
Small Scale
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