Relation of chemical and physical processes in two-phase detonations

Author(s):  
P.L. LU ◽  
N. SLAGG ◽  
B.D. FISHBURN ◽  
P.P. OSTROWSKI
Keyword(s):  
Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2511
Author(s):  
Jintao Liu ◽  
Di Xu ◽  
Shaohui Zhang ◽  
Meijian Bai

This paper investigates the physical processes involved in the water filling and air expelling process of a pipe with multiple air valves under water slow filling condition, and develops a fully coupledwater–air two-phase stratified numerical model for simulating the process. In this model, the Saint-Venant equations and the Vertical Average Navier–Stokes equations (VANS) are respectively applied to describe the water and air in pipe, and the air valve model is introduced into the VANS equations of air as the source term. The finite-volume method and implicit dual time-stepping method (IDTS) with two-order accuracy are simultaneously used to solve this numerical model to realize the full coupling between water and air movement. Then, the model is validated by using the experimental data of the pressure evolution in pipe and the air velocity evolution of air valves, which respectively characterize the water filling and air expelling process. The results show that the model performs well in capturing the physical processes, and a reasonable agreement is obtained between numerical and experimental results. This agreement demonstrates that the proposed model in this paper offers a practical method for simulating water filling and air expelling process in a pipe with multiple air valves under water slow filling condition.


Author(s):  
F. Peng ◽  
S. K. Aggarwal

The present paper reviews the methodologies for representing the droplet motion and vaporization history in two-phase flow computations. The focus is on the use of droplet models that are realistic in terms of their efficient implementation in comprehensive spray simulations, representation of important physical processes, and applicability under a broad range of conditions. The methodologies available at present to simulate droplet motion in complex two-phase flows may be broadly classified into two categories. First one is based on the modified BBO equation. This approach is more comprehensive, but requires modifications and/or correlations at higher droplet Reynolds number. Second approach aims at developing correlations, using detailed numerical simulations or laboratory experiments, for the effects of flow nonuniformity and droplet relative acceleration on the instantaneous drag and lift coefficients. Recent advances made in the droplet vaporization models are also discussed. The advanced vaporization models include the effects of transient liquid heating, gas-phase convection, and variable thermophysical properties. All of these models are discussed, and recommendations are made for their inclusion in comprehensive two-phase computations.


2021 ◽  
pp. 31-39
Author(s):  
Alexander V. KRIVILEV ◽  
◽  
Evgeniy A. DUNICH ◽  

The article describes a new approach to the consideration of physical processes in switched motors with two-section phase windings, in which the section is taken as an elementary analysis unit. A system of designations for sections and phases is proposed, which can be extended to an arbitrary number of phases in the motor and sections in the phase. The possible states of the phases and sections that characterize the participation of each of them in producing the electromagnetic torque are determined. For a two-phase switched motor, possible section connection diagrams, phase engagement methods corresponding to these diagrams, and sets of basic armature magnetic induction vectors are determined. An analytical description of the basic vectors in the form of sets, the elements of which contain information about the amplitude and phase shift, is performed. The sets of basic vectors in a two-phase motor with a two-section phase winding are compared with those in a three-phase motor with a single-section phase winding, which is currently most widely used. The obtained description of the basic vector sets can serve as a basis for analytically representing a digital device for controlling a two-phase switched motor, and also as a basis for implementing control methods based on vector pulse width modulation.


1995 ◽  
Vol 117 (3) ◽  
pp. 453-461 ◽  
Author(s):  
S. K. Aggarwal ◽  
F. Peng

The present paper reviews the methodologies for representing the droplet motion and vaporization history in two-phase flow computations. The focus is on the use of droplet models that are realistic in terms of their efficient implementation in comprehensive spray simulations, representation of important physical processes, and applicability under a broad range of conditions. The methodologies available at present to simulate droplet motion in complex two-phase flows may be broadly classified into two categories. First one is based on the modified BBO equation. This approach is more comprehensive, but requires modifications and/or correlations at higher droplet Reynolds number. The second approach aims at developing correlations, using detailed numerical simulations or laboratory experiments, for the effects of flow nonuniformity and droplet relative acceleration on the instantaneous drag and lift coefficients. Recent advances made in the droplet vaporization models are also discussed. The advanced vaporization models include the effects of transient liquid heating, gas-phase convection, and variable thermo physical properties. All of these models are discussed, and recommendations are made for their inclusion in comprehensive two-phase computations.


2021 ◽  
Vol 2131 (2) ◽  
pp. 022001
Author(s):  
Yu O Bobreneva ◽  
P I Rahimly ◽  
Yu A Poveshchenko ◽  
V O Podryga ◽  
L V Enikeeva

Abstract A method of numerical modeling based on splitting by physical processes of two-phase fluid transfer in a formation with fractured-porous reservoirs is described. Reservoirs of this type have a natural fracture system and are described by the dual porosity model. A four-block mathematical model of the fluid redistribution between a pore-type matrix and a natural fracturing pattern is proposed and studied. The resulting system is complex and entails a number of difficulties associated with a large number of variables and the absence of important properties of a linearized system of equations, such as self-adjointness and symmetry, which are present in the description of piezoconductive processes. The complete splitting by physical processes is carried out to solve this problem. The resulting split model is differentially equivalent to the discrete initial balance equations of the system (conservation of the mass components of the fluids and the total energy of the system), written in divergent form. This approach is associated with a nonlinear approximation of the grid functions in time, which depends on the fraction of the volume occupied by the fluids in the pores, and is easy to implement.


1979 ◽  
Vol 6 (7-8) ◽  
pp. 815-826 ◽  
Author(s):  
P.L. Lu ◽  
N. Slagg ◽  
B.D. Fishburn ◽  
P.P. Ostrowski
Keyword(s):  

2006 ◽  
Vol 11 (3) ◽  
pp. 295-314 ◽  
Author(s):  
A. Narimanyan ◽  
A. Muntean

This note emphasizes the application of the moving‐boundary methodology in the modelling of two processes of particular industrial relevance. The first model explains the application of the Stefan and Signorini type boundary conditions in the modelling of the thermal cutting of metals by a plasma beam, while the second model shows how interface kinetic conditions, employed within the framework of a two‐phase Stefan‐like model, can describe the dynamics of an aggressive reaction front in concrete‐based materials. Our formulations provide a conceptually new approach towards the understanding of the involved physical processes. The connection between the two models is discussed as well. It relies on the presence of non‐equilibrium conditions driving the moving interface.


2021 ◽  
pp. 1-20
Author(s):  
Yulia Olegovna Bobreneva ◽  
Parvin Ilgar gizi Rahimly ◽  
Victoria Olegovna Podryga ◽  
Svetlana Sergeevna Bazhitova ◽  
Ahmed Elsaid Ezeldin Bakeer Ali Bakeer ◽  
...  

In this work, the authors propose an algorithm for solving the problem of the process of mass transfer of a two-phase fluid in a fractured-porous reservoir in a one-dimensional formulation. The presence of natural fractures in such reservoirs impedes various types of exploration during field development. Fractured porous reservoirs are characterized by intense exchange fluid flow between fractures and porous blocks. Each system under consideration has its own individual set of filtration-capacity parameters that complicates the problem. To study the mass transfer of a two-phase liquid in a medium with double porosity, a four-block mathematical model with splitting by physical processes is proposed. The model is described by a system of partial differential equations. The method of splitting by physical processes forms two functional blocks: by water saturation and piezoconductivity. For the numerical solution of this system, an absolutely stable implicit finite-difference scheme is made in the spatially one-dimensional case. On the basis of the proposed difference scheme, pressures and saturations in the matrix and fracture system are calculated.


Author(s):  
Paul S. Hutcheson ◽  
John W. Chew ◽  
Rex B. Thorpe ◽  
Colin Young

For many gas turbine architectures a failure modes and effects analysis identifies a potential mode in which failure of an oil transfer pipe could result in oil leakage into the secondary air system. Such an event would result in a complex two-phase interacting flow. The atomisation and transport of the oil within the air system is of interest, but is difficult to predict. Available data for the droplet size resulting from jet breakup in crossflow are limited. A dimensional analysis shows jet breakup in a crossflow to involve many factors. The atomisation process has been shown experimentally to include many physical processes and is still not completely understood. Currently, the most practical method of modelling these breakup processes in sprays is by using a CFD package with a set of sub-models within an Euler-Lagrangian (discrete-droplet) approach. The strengths and weaknesses of each of these sub-models cannot reasonably be tested when used in combination with other approximations to model a spray in crossflow. The purpose of this study was to assess various submodels for liquid breakup with a series of simple test cases.


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