scholarly journals Rheological Parameter Analysis in Generalized Bulk Mixture Mass Flow Model

2020 ◽  
Vol 37 (1-2) ◽  
pp. 71-79
Author(s):  
Puskar R Pokhrel ◽  
Parameshwari Kattel ◽  
Khim B Khattri ◽  
Jeevan Kafle
Keyword(s):  
Mass Flow ◽  
Rheological Behavior ◽  
Flow Model ◽  
Parameter Analysis ◽  
Physical Parameters ◽  
Rheological Parameter ◽  
Two Phase ◽  
Rate Dependent ◽  
Mixture Pressure ◽  
Model Equations

Pokhrel et al. recently developed a generalized quasi two-phase bulk mixture model for mass flow. This model has been constructed by employing full dimensional two-phase mass flow model equations. The model is a set of coupled partial differential equations which is characterized by some new mechanical and dynamical aspects of generalized bulk and shear viscosities, pressure, velocities and effective friction for the mixture where all these are evolving as functions of several dynamical variables, physical parameters, inertial and dynamical coefficients and drift factors. They formulated pressure and rate-dependent Coulumbviscoplastic rheology of the mixture mass flow to describe the model equation. Rheological behavior of the flow dynamics affects the whole dynamics of mixture mass flow. So, in this paper, the relations of mixture pressure and viscosity with respect to pressure drifts and solid volume fractions are studied to describe the rheological behavior of the generalized bulk mixture mass flow model. Moreover, the behaviour of mixture viscosities with respect to isotrophic drifts are also analyzed. We also present the simulation result for the time evolution of the drift induced full dynamical mixture pressure of the material exited from a silo gate that moves down slope along a channel.

Evaluation of Two-Phase Frictional Pressure Drop Correlations Against Experimental Data

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Wei Li ◽  
Kunrong Shen ◽  
Boren Zheng ◽  
Xiang Ma ◽  
S. A. Sherif ◽  
...  
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Mass Flow ◽  
Flow Model ◽  
Saturation Temperature ◽  
Separated Flow ◽  
Outer Diameter ◽  
Two Phase ◽  
Homogeneous Flow ◽  
Frictional Pressure Drop

Abstract Results are presented here from an experimental investigation on tube side two-phase characteristics that took place in four tested tubes—the 1EHT-1, 1EHT-2, 4LB, and smooth tubes. The equivalent outer diameter of the tube was 9.52 mm and the inner diameter was 8.32 mm. Condensation tests were conducted using refrigerant R410A at a saturation temperature of 318 K, over a mass flow range of 150–450 kg m−2 s−1, with inlet and outlet vapor qualities of 0.8 and 0.2, respectively. Evaporation tests were performed at a saturation temperature of 279 K, over a mass flow range of 150–380 kg m−2 s−1, with inlet and outlet vapor qualities of 0.2 and 0.8, respectively. Pressure drop data of the four tested tubes were collected to evaluate five identified prediction correlations based on the separated flow model and the homogeneous flow model. The separated flow approaches presented predictions with average MAEs of 24.9% and 16.4% for condensation and evaporation data, respectively, while the average MAEs of the homogeneous flow model were 31.6% and 43.4%, respectively. Almost all the identified correlations underestimated the frictional pressure drop of the 4LB tube with MAEs exceeding 30%. An earlier transition of different flow patterns was expected to occur in the EHT tubes while developing a new diabatic flow pattern map is needed for the 4LB tube. A new correlation was presented based on the two-phase multiplier Φ and the Martinelli parameter Xtt, which exhibited excellent predictive results for the experimental data.

scholarly journals Discontinuous Galerkin method for solving incompressible two-phase shallow granular flow model

2019 ◽  
Vol 11 (9) ◽  
pp. 168781401987490
Author(s):  
Muhammad Rehan Saleem ◽  
Ubaid Ahmed Nisar ◽  
Shamsul Qamar
Keyword(s):  
Galerkin Method ◽  
Discontinuous Galerkin ◽  
Discontinuous Galerkin Method ◽  
Numerical Scheme ◽  
Flow Model ◽  
Numerical Study ◽  
Momentum Exchange ◽  
Two Phase ◽  
Runge Kutta ◽  
Model Equations

This article deals with the numerical study of two-phase shallow flow model describing the mixture of fluid and solid granular particles. The model under investigation consists of coupled mass and momentum equations for solid granular material and fluid particles through non-conservative momentum exchange terms. The non-conservativity of model equations poses major challenges for any numerical scheme, such as well balancing, positivity preservation, accurate approximation of non-conservative terms, and achievement of steady-state conditions. Thus, in order to approximate the present model an accurate, well-balanced, robust, and efficient numerical scheme is required. For this purpose, in this article, Runge–Kutta discontinuous Galerkin method is applied successfully for the first time to solve the model equations. Several test problems are also carried out to check the performance and accuracy of our proposed numerical method. To compare the results, the same model is solved by staggered central Nessyahu–Tadmor scheme. A good comparison is found between two schemes, but the results obtained by Runge–Kutta discontinuous Galerkin scheme are found superior over the central Nessyahu–Tadmor scheme.

scholarly journals Simulating glacial lake outburst floods with a two-phase mass flow model

2016 ◽  
Vol 57 (71) ◽  
pp. 349-358 ◽  
Author(s):  
Parameshwari Kattel ◽  
Khim B. Khattri ◽  
Puskar R. Pokhrel ◽  
Jeevan Kafle ◽  
Bhadra Man Tuladhar ◽  
...  
Keyword(s):  
Mass Flow ◽  
Debris Flows ◽  
Flow Model ◽  
Glacial Lake ◽  
Mass Force ◽  
Two Phase ◽  
Outburst Floods ◽  
Glacial Lake Outburst Floods ◽  
Mass Flows ◽  
Fluid Phases

AbstractTo simulate a glacial lake outburst flood, we employ a comprehensive physically based general two-phase mass flow model (Pudasaini, 2012). This model accounts for a strong interaction between the solid and fluid phases and incorporates buoyancy and other dominant physical aspects of the mass flows such as enhanced non-Newtonian viscous stress, virtual mass force and generalized drag. Our real two-phase mass flow simulation describes explicit evolution of the solid and fluid phases and the debris bulk as a whole, akin to torrential debris flows or debris floods during glacial lake outburst floods (GLOFs). The emptying of a lake following rapid collapse of a restraining dam, the consequent downslope motion of a mixed solid–fluid mass, and the tendency of the mass to form extruding plumes are analyzed in detail for different flow configurations, volumes, conduit geometries and boundary conditions. The solid and fluid phases evolve completely differently and reveal fundamentally different dynamical behaviours. During the flow, the relatively long fluid tail follows the solid-rich dense frontal surge head. The bulk debris develops into a frontal and side levee as derived from the initial frontal moraine dam. Results show that our high-resolution, unified simulation strategies and the advanced model equations can be applied to study the flow dynamics of a wide range of geophysical mass flows such as snow and rock–ice avalanches, debris flows and flash floods as well as GLOFs. This may help substantially in forming a basis for appropriate mitigation measures against potential natural hazards in high mountain slopes and valleys.

A parameter analysis of a two-phase flow model for supersaturated total dissolved gas downstream spillways

2016 ◽  
Vol 28 (4) ◽  
pp. 648-657 ◽  
Author(s):  
Hui-xia Yang ◽  
Ran Li ◽  
Rui-feng Liang ◽  
Juan Wei ◽  
Qin Zhang
Keyword(s):  
Flow Model ◽  
Two Phase Flow ◽  
Parameter Analysis ◽  
Phase Flow ◽  
Dissolved Gas ◽  
Two Phase ◽  
Total Dissolved Gas

scholarly journals On analytical solutions of a two-phase mass flow model

2018 ◽  
Vol 41 ◽  
pp. 412-427 ◽  
Author(s):  
Sayonita Ghosh Hajra ◽  
Santosh Kandel ◽  
Shiva P. Pudasaini
Keyword(s):  
Mass Flow ◽  
Analytical Solutions ◽  
Flow Model ◽  
Two Phase

scholarly journals Simulations for Flow-Symmetry Through r.avaflow in the General Two-Phase Mass Flow Model

2019 ◽  
Vol 2 (2) ◽  
pp. 45-60
Author(s):  
Jeevan Kafle ◽  
Parameshwari Kattel
Keyword(s):  
Mass Flow ◽  
Laboratory Experiments ◽  
Flow Model ◽  
Rotational Symmetry ◽  
Flow Dynamics ◽  
Mass Wasting ◽  
Two Phase ◽  
Proper Understanding ◽  
Different Types ◽  
Flow Symmetry

Gravitational flows, e.g., landslide, debris flow and avalanches are hazardous mass wasting processes. The proper understanding of their dynamics is very important. As laboratory experiments can not perfectly model their initiation process and field assess of the live events are very difficult, numerical experiments have become the promising way for the study of their flow dynamics. Here we employ the enhanced version of two-phase mass flow model [33] through the open source computational code, r.avaflow to analyze the issue of symmetry in the flow. Two-phase debris mass are triggered from all the flanks of the three different pyramids (triangle-based, square-based and octagon-based) with different rotational symmetry and study the flow pattern along with maximum kinetic energy of the flow. Flow past two different types of obstacles (a tetrahedron and a square based pyramid) are also observed. The possible causes of asymmetry in the flow are also analyzed.

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