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.

Performance Evaluation of Liquid Flow With PCM Particles in Microchannels

2005 ◽  
Vol 127 (8) ◽  
pp. 931-940 ◽  
Author(s):  
K. Q. Xing ◽  
Y.-X. Tao ◽  
Y. L. Hao
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Laminar Flow ◽  
Phase Change ◽  
Performance Index ◽  
Single Phase ◽  
Suspension Flow ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Two Phase

A two-phase, non thermal equilibrium-based model is applied to the numerical simulation of laminar flow and heat transfer characteristics of suspension with microsize phase-change material (PCM) particles in a microchannel. The model solves the conservation of mass, momentum, and thermal energy equations for liquid and particle phases separately. The study focuses on the parametric study of optimal conditions where heat transfer is enhanced with an increase in fluid power necessary for pumping the two-phase flow. The main contribution of PCM particles to the enhancement of heat transfer in a microsize tube is to increase the effective thermal capacity and utilize the latent heat effect under the laminar flow condition. An effectiveness factor εeff is defined to evaluate the heat transfer enhancement compared to the single-phase flow heat transfer and is calculated under different wall heat fluxes and different Reynolds numbers. The comparison is also made to evaluate the performance index, i.e., the ratio of total heat transfer rate to fluid flow power (pressure drop multiplied by volume flow rate) between PCM suspension flow and pure water single-phase flow. The results show that for a given Reynolds number, there exists an optimal heat flux under which the εeff value is the greatest. In general, the PCM suspension flow with phase change has a significantly higher performance index than the pure-fluid flow. The comparison of the model simulation with the limited experimental results for a MCPCM suspension flow in a 3mmdia tube reveals the sensitivity of wall temperature distribution to the PCM supply temperature and the importance of characterizing the phase change region for a given tube length.

scholarly journals An Explicit Analytical Solution for Transient Two-Phase Flow in Inclined Fluid Transmission Lines

Fluids ◽  
2021 ◽  
Vol 6 (9) ◽  
pp. 300
Author(s):  
Taoufik Wassar ◽  
Matthew A. Franchek ◽  
Hamdi Mnasri ◽  
Yingjie Tang
Keyword(s):  
Steady State ◽  
Analytical Model ◽  
Transmission Lines ◽  
Single Phase ◽  
Flow Model ◽  
Two Phase Flow ◽  
Mechanistic Model ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Two Phase

Due to the complex nonlinearity characteristics, analytical modeling of compressible flow in inclined transmission lines remains a challenge. This paper proposes an analytical model for one-dimensional flow of a two-phase gas-liquid fluid in inclined transmission lines. The proposed model is comprised of a steady-state two-phase flow mechanistic model in-series with a dynamic single-phase flow model. The two-phase mechanistic model captures the steady-state pressure drop and liquid holdup properties of the gas-liquid fluid. The developed dynamic single-phase flow model is an analytical model comprised of rational polynomial transfer functions that are explicitly functions of fluid properties, line geometry, and inclination angle. The accuracy of the fluid resonant frequencies predicted by the transient flow model is precise and not a function of transmission line spatial discretization. Therefore, model complexity is solely a function of the number of desired modes. The dynamic single-phase model is applicable for under-damped and over-damped systems, laminar, and turbulent flow conditions. The accuracy of the overall two-phase flow model is investigated using the commercial multiphase flow dynamic code OLGA. The mean absolute error between the two models in step response overshoot and settling time is less than 8% and 2 s, respectively.

An Experimental Study of Single-Phase and Two-Phase Fluid Flow in Horizontal Wells

1998 ◽  
Author(s):  
Liang-Biao Ouyang ◽  
Nicholas Petalas ◽  
Sepehr Arbabi ◽  
Donald E. Schroeder ◽  
Khalid Aziz
Keyword(s):  
Experimental Study ◽  
Fluid Flow ◽  
Single Phase ◽  
Horizontal Wells ◽  
Two Phase ◽  
Phase Fluid

A computationally efficient two-phase hydro-sediment-morphdynamic model and its preliminary field applications  

2021 ◽  
Author(s):  
Binghan Lyu ◽  
Peng Hu ◽  
Ji Li ◽  
Zhixian Cao ◽  
Wei Li ◽  
...  
Keyword(s):  
Yangtze River ◽  
Single Phase ◽  
Flow Model ◽  
Two Phase Flow ◽  
Measure Data ◽  
Special Focus ◽  
Phase Flow ◽  
Computationally Efficient ◽  
Single Phase Flow ◽  
Two Phase

<p>While fluvial flows carrying relatively coarse sediments involve strong two-phase interactions, existing numerical modeling in the field-scale is mostly based on quasi-single phase flow model. Here a computationally efficient two-phase hydro-sediment-morphodynamic model is developed with a special focus on field applications. The hybrid LTS/GMaTS method originally developed for quasi-single flow model is extended to the present two-phase flow model, of which the achieved reduction in the computational cost facilitates the present field applications in the Taipingkou Waterway, Middle Yangtze River. To overcome numerical instabilities arising from the relatively large spatial and time steps in field case that lead to an issue of stiff source term, the following numerical treatments are proposed: implementation of theoretically-derived lower and upper limits for the inter-phase interactive forces. Moreover, to improve the numerical accuracy, the HLLC approximate Riemann solver is used for the water phase, whereas the FORCE solver is used for the sediment phase. Both the present two-phase flow model and the existing quasi-single-phase flow model are applied to a series of typical cases, including refilling of a dredged trench, a full dam-break flow in an abruptly widening channel and reproduction of the Taipingkou waterway, Middle Yangtze River. Compared with the quasi-single-phase flow model, the two-phase flow model has better performance as compared to the measure data and has more profound physical significance.</p>

Performance Evaluation of Liquid Flow With NPCM in Microchannels

Volume 4 ◽  
2004 ◽  
Author(s):  
K. Q. Xing ◽  
Y.-X. Tao ◽  
Y. L. Hao
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Laminar Flow ◽  
Phase Change ◽  
Performance Index ◽  
Single Phase ◽  
Suspension Flow ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Two Phase

A two-phase, non-thermal-equilibrium based model is applied to the numerical simulation of laminar flow and heat-transfer characteristics of suspension with nano-size phase change material (NPCM) particles in a microchannel. The model solves the conservation of mass, momentum and thermal energy equations for liquid and particle phases separately. The study focuses on the parametric study of optimal conditions where heat transfer is enhanced with an increase in fluid power necessary for pumping the two-phase flow. The main contribution of NPCM particles to the enhancement of heat transfer in a micro-size tube is to increase the effective thermal capacity and utilize the latent heat effect under the laminar flow condition. An effectiveness factor εeff is defined to evaluate the heat transfer enhancement compared to the single phase flow heat transfer and is calculated under different wall heat fluxes and different Reynolds numbers. The comparison is also made to evaluate the performance index (PI); i.e., the ratio of total heat transfer rate to fluid flow power (pressure drop multiplied by volume flow rate) between NPCM suspension flow and pure water single-phase flow. The results show that for a given Reynolds number, there exists an optimal heat flux under which the εeff value is the greatest. In general, the NPCM suspension flow with phase change has a significantly higher performance index than the pure-fluid flow.

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