A Prediction of the Leakage Through Cracks for Leak Before Break

2014 ◽  
Author(s):  
Jing Zhang ◽  
Yingwei Wu ◽  
Lei Ding ◽  
Hongwei Qiao ◽  
Pengzhou Li ◽  
...  
Keyword(s):  
Flow Model ◽  
Crack Open Displacement ◽  
Two Phase ◽  
Crack Open ◽  
Naturally Occurring ◽  
Open Displacement ◽  
Leak Before Break ◽  
Phase Fluid ◽  
New Phase ◽  
Good Agreement

A code was developed in this study to predict the leakage of the leak before break (LBB). Various stagnation conditions were considered, including the subcooled water, the two-phase fluid and the overheated steam. Moreover, both the critical and noncritical flow was studied. The Henry-Fauske critical flow model was revised by a new phase transition point and the pressure drop due to friction and turns were modified. The code was verified by the comparison with the experimental data on the leakage of conventional pipes, artificial cracks and naturally occurring cracks, which shows a good agreement and this code has a higher precision than the existing codes. The influence of crack morphologies on LBB leakage was discussed, including the local roughness, the global roughness, the crack open displacement (COD) and the number of the corners. Besides, the dependence of the LBB leakage on stagnation enthalpy and back pressure was also investigated.

Numerical Prediction of Critical Cavitation Performance in Hydraulic Turbines

2003 ◽  
Author(s):  
Sadao Kurosawa ◽  
Kiyoshi Matsumoto
Keyword(s):  
Flow Model ◽  
Flow Analysis ◽  
Prediction Method ◽  
Hydraulic Turbine ◽  
Francis Turbine ◽  
Two Phase ◽  
Cavitation Performance ◽  
Hydraulic Turbines ◽  
Critical Cavitation ◽  
Good Agreement

In this paper, numerical method for predicting critical cavitation performance in a hydraulic turbine is presented. The prediction method is based on unsteady cavitation flow analysis to use bubble two-phase flow model. The prediction of the critical cavitation performance was carried out for the aixal hydraulic turbine and the francis turbine as a typical examples. Results compared to the experiment showed a good agreement for the volume of cavity and the performance drop off and it was recognized that this method could be used as an engineering tool of a hydraulic turbine development.

Predicting Two Phase Flow Pressure Drop With CFD and ANN

2010 ◽  
Author(s):  
I˙smail Teke ◽  
O¨zden Ag˘ra ◽  
Hakan Demir ◽  
S¸. O¨zgu¨r Atayılmaz
Keyword(s):  
Pressure Drop ◽  
Flow Model ◽  
Two Phase Flow ◽  
Saturation Temperature ◽  
Smooth Tube ◽  
Phase Flow ◽  
Two Phase ◽  
Analytical Formulas ◽  
Flow Pressure ◽  
Good Agreement

In this study, the several well known two-phase viscosity models were used for predicting two-phase flow pressure drop in a smooth tube using Computational Fluid Dynamics (CFD) software at homogenous flow conditions. Pressure drop for two different mass flux values (300 and 650 kg/m2s) for R134a with a saturation temperature of 45 °C in a smooth tube has been modeled according to the homogenous flow model and the results have been compared with the analytical formulas and experimental data from the literature. Three different average viscosity correlations were used. It is seen that the numerical results are in a good agreement with the homogenous flow model and fall in ± 30% band. Also, the results derived from the average viscosity expression are in a good agreement with the results calculated using separated two-phase flow correlations. In addition to this, Artificial Neural Networks (ANNs) were employed for predicting the pressure drop in a horizontal smooth pipe. The trained network gives the best values over the correlations with less than 1% mean relative error.

scholarly journals Numerical modeling of the 2013 meteorite entry in Chebarkul Lake, Russia

2017 ◽  
Author(s):  
Andrey Kozelkov ◽  
Andrey Kurkin ◽  
Efim Pelinovsky ◽  
Vadim Kurulin ◽  
Elena Tyatyushkina
Keyword(s):  
Numerical Modeling ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Tsunami Waves ◽  
Theoretical Predictions ◽  
Meteorite Fall ◽  
Phase Fluid ◽  
Good Agreement

Abstract. The results of the numerical simulation of possible hydrodynamic perturbations in Lake Chebarkul (Russia) as a consequence of the meteorite fall of 2013 (Feb. 15) are presented. The numerical modeling is based on the Navier-Stokes equations for a two-phase fluid. The results of the simulation of a meteorite entering the water at an angle of 20 degrees are given. Numerical experiments are carried out both when the lake is covered with ice and when it isn't. The estimation of size of the destructed ice cover is made. It is shown that the size of the observed ice-hole at the place of the meteorite fall is in good agreement with the theoretical predictions, as well as with other estimates. The heights of tsunami waves generated by a small meteorite entering the lake are small enough (a few centimeters) according to the estimations. However, the danger of a tsunami of meteorite or asteroid origin should not be underestimated.

scholarly journals Effects of coupled hydro-mechanical model considering two-phase fluid flow on potential for shallow landslides: a case study in Halmidang Mountain, Yongin, South Korea

2019 ◽  
Author(s):  
Sinhang Kang ◽  
Byungmin Kim
Keyword(s):  
Fluid Flow ◽  
Slope Stability ◽  
Single Phase ◽  
Flow Model ◽  
Coupled Model ◽  
Shallow Landslides ◽  
Single Phase Flow ◽  
Two Phase ◽  
Fully Coupled ◽  
Phase Fluid

Abstract. More than 30 shallow landslides were caused by heavy rainfall that occurred on July 26 and 27, 2011, in Halmidang Mountain, Yongin-si, Gyeonggi Province, South Korea. To precisely analyze shallow landslides and to reflect the mechanism of fluid flow in void spaces of soils, we apply a fully coupled hydro-mechanical model considering two-phase fluid flow of water and air. The available GIS-based topographic data, geotechnical and hydrological properties, and historical rainfall data are used for infiltration and slope stability analyses. Changes in pore air and water pressures and saturations of air and water are obtained from the infiltration analysis, which were used to calculate the safety factor for slope stability assessment. By comparing the results from numerical models by applying a single-phase flow model and a fully coupled model, we investigate the effects of air flow and variations in hydraulic conductivity affected by stress–strain behavior of soil on slope stability. Our results suggest that air flow and hydro-mechanical coupling affects the rate of increase in pore water pressure, thus influencing the safety factor on slopes when ponding is more likely to occur during heavy rainfall. Finally, we conduct slope failure assessments using the fully coupled model, slightly more consistent with actual landslide events than the single-phase flow model.

scholarly journals Numerical modeling of the 2013 meteorite entry in Lake Chebarkul, Russia

2017 ◽  
Vol 17 (5) ◽  
pp. 671-683 ◽  
Author(s):  
Andrey Kozelkov ◽  
Andrey Kurkin ◽  
Efim Pelinovsky ◽  
Vadim Kurulin ◽  
Elena Tyatyushkina
Keyword(s):  
Numerical Modeling ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Tsunami Waves ◽  
Theoretical Predictions ◽  
Meteorite Fall ◽  
Phase Fluid ◽  
Good Agreement

Abstract. The results of the numerical simulation of possible hydrodynamic perturbations in Lake Chebarkul (Russia) as a consequence of the meteorite fall of 2013 (15 February) are presented. The numerical modeling is based on the Navier–Stokes equations for a two-phase fluid. The results of the simulation of a meteorite entering the water at an angle of 20° are given. Numerical experiments are carried out both when the lake is covered with ice and when it is not. The estimation of size of the destructed ice cover is made. It is shown that the size of the observed ice hole at the place of the meteorite fall is in good agreement with the theoretical predictions, as well as with other estimates. The heights of tsunami waves generated by a small meteorite entering the lake are small enough (a few centimeters) according to the estimations. However, the danger of a tsunami of meteorite or asteroid origin should not be underestimated.

scholarly journals Exploration of Constants Independent of Material and Layup in Transverse Matrix Cracking of Cross-ply Laminate

1993 ◽  
Vol 2 (1) ◽  
pp. 096369359300200
Author(s):  
L-Y Xu
Keyword(s):  
Matrix Cracking ◽  
Crack Open Displacement ◽  
Shear Lag ◽  
Crack Open ◽  
Shear Lag Model ◽  
Stiffness Reduction ◽  
Longitudinal Stiffness ◽  
Lag Model ◽  
Open Displacement ◽  
Lamination Theory

Stiffness reduction caused by matrix crack in cross–ply laminates of CFRP, GFRP, KFRP can be predicted well by a shear–lag model assuming a constant of the crack open displacement index. Due to the existence of the saturation crack state (CDS), stiffness reduction has a low boundary, the minimum normalized longitudinal stiffness of the cracked plies is 0.3 instead of 0 used in current lamination theory on the behaviour prediction after FPF.

Numerical Simulation of Two Phase Flows in a Bath With Top-Blowing Lance Injection

1999 ◽  
Author(s):  
J. L. Xia ◽  
T. Ahokainen ◽  
L. Holappa
Keyword(s):  
Numerical Simulation ◽  
Flow Model ◽  
Turbulent Dispersion ◽  
Dispersion Forces ◽  
Two Phase Flows ◽  
Two Phase ◽  
Operational Conditions ◽  
Plume Region ◽  
Insight Into ◽  
Good Agreement

Abstract Numerical simulation of two phase flows in a bath agitated by top blowing lance injection is carried out using the CFX code. An Eulerian-Eulerian two phase flow model is used. The drag, lift and turbulent dispersion forces are taken into account for the interface interactions. Calculations show that there exist different flow patterns with changing the operational conditions (Q, dn, and hn/H). The gas-liquid plume spreads radially, gradually in most of the plume region and extensively near the free surface. For the cases considered, bubbles in the central plume (r = 0.006 m) accelerate up to their terminal rising velocity, then move at this rising velocity, and thereafter decelerate when they approach the surface. A similar behaviour is demonstrated for the liquid rising velocity. Numerical results are compared with available experimental data, and a good agreement is achieved. Predictions provide insight into the flow behaviour and useful information for engineering design.

A Transient Two-Phase Fluid- and Heat-Flow Model for Gas-Lift-Assisted Waxy-Crude Wells With Periodical Electric Heating

2014 ◽  
Vol 53 (05) ◽  
pp. 304-314 ◽  
Author(s):  
Guoqing Han ◽  
He Zhang ◽  
Kegang Ling ◽  
Di Wu ◽  
Zuguo Zhang
Keyword(s):  
Heat Flow ◽  
Flow Model ◽  
Electric Heating ◽  
Two Phase ◽  
Waxy Crude ◽  
Heat Flow Model ◽  
Phase Fluid ◽  
Gas Lift
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