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CN-122021215-A - Calculation and analysis method for particle coalescence growth process in turbulence of square channel

CN122021215ACN 122021215 ACN122021215 ACN 122021215ACN-122021215-A

Abstract

The invention discloses a calculation and analysis method for particle coalescence growth process in square channel turbulence, which relates to the technical field of fluid mechanics, and comprises the following specific steps of establishing a turbulence mathematical model and solving to obtain square channel turbulence field data; the invention provides a calculation method for a particle aggregation growth process in a square channel turbulence field, which can accurately reflect aggregation and rupture behavior states and particle size evolution rules of particles in the square channel turbulence field in real time through direct numerical simulation and simultaneously realize accurate calculation of the square channel turbulence field under a particle motion feedback effect.

Inventors

  • WANG YANZHI
  • LIU YUNXIN
  • MA WENLI
  • WANG SHUAI
  • ZHANG LIMING

Assignees

  • 延安大学

Dates

Publication Date
20260512
Application Date
20260114

Claims (10)

  1. 1. The method for calculating and analyzing the particle coalescence growth process in the turbulence of the square channel is characterized by comprising the following specific steps: determining a geometric model of a square channel based on a fluid flow space, dividing the geometric model into grid units, and setting boundary types on the geometric model after grid division to obtain the grid model of the square channel turbulent flow; Establishing a turbulent flow mathematical model and solving a flow field, namely establishing a mathematical model of fluid flow in a square channel based on a Navier-Stokes equation, introducing a grid model, setting fluid physical parameters, boundary condition types and flow state parameters, and solving the Navier-Stokes equation on corresponding nodes in a grid unit by a spectrum unit method to obtain turbulent flow field data such as the speed, the pressure and the secondary flow distribution of the fluid in the square channel; The particle motion equation is constructed by acquiring physical attribute parameters of particles, and establishing the motion equation of the particles by considering various hydrodynamic forces and field forces of the particles in turbulence of a square channel based on a Lagrange particle tracking method; Inputting turbulence flow field speed data into the particle motion equation, solving the motion equation of the particles by adopting a fourth-order Dragon lattice tower method, and simultaneously calculating the space position, speed and particle stress distribution of different particles by considering the collision effect among the particles based on a hard sphere model; The method comprises the steps of constructing a collision-aggregation and collision-fracture action model among particles, namely acquiring adhesive property parameters such as Hamek constant, yield pressure, minimum contact distance, collision recovery coefficient and the like of the particles, and constructing a viscous particle collision-aggregation and collision-fracture action model by considering Van der Waals force among the particles according to a particle collision energy dissipation theory and a DLVO theory; And (3) calculating and acquiring original particle information of aggregation and rupture behaviors, namely inputting the speed distribution data of the particles into a collision-aggregation and collision-rupture model formula, and analyzing, judging and determining the speed, the position and the particle size data of the particles with aggregation and rupture behaviors before aggregation or rupture behaviors. The method comprises the steps of calculating and obtaining particle mass information after aggregation and rupture, namely obtaining a derivative formula describing the particle aggregation process based on a momentum conservation principle, importing original particle speed, position and particle size data of aggregation or rupture into the formula, calculating and recording the position, speed and particle size of the particle mass after aggregation and rupture, calculating and analyzing to obtain turbulent flow field speed distribution at the position of the particle mass, and accurately describing the aggregation and growth process of viscous particles in a turbulent flow field of a square channel. And analyzing and recording particle size distribution rules of particles in the turbulence field of the square channel at the current moment, namely counting and recording the number distribution rules of all particle aggregation and rupture events occurring in the turbulence field of the square channel at the current moment, analyzing to obtain particle size distribution rules of particle aggregates with different sizes, comparing the particle size distribution rules with the particle size probability distribution rules recorded at the last moment, and judging whether the particle size distribution rules are the same or not. On the premise of changing particle size distribution rules, taking the adverse effect of all particles and particle aggregate movements on a turbulent flow field into consideration, establishing a fluid-particle movement inter-phase coupling action model, correcting Navier-Stokes equations, solving again to obtain the speed, pressure and secondary flow distribution of a square channel turbulent flow field, updating turbulent flow field data, realizing the coupling calculation of a particle aggregation and growth dynamics process and the turbulent flow field in the subsequent stage until particle aggregation and rupture behaviors in the turbulent flow field reach a dynamic balance state, and the particle size distribution rules of the particles are not changed.
  2. 2. The method for calculating and analyzing particle agglomeration growth process in square channel turbulence according to claim 1, wherein in the step of constructing the grid model of square channel turbulence flow, the geometric dimension of the square channel is determined based on the space area occupied by the turbulence fluid, the geometric model is obtained, the geometric model is divided into a plurality of hexahedral grid cell subregions, and the number of grid cell regions close to the boundary region is increased. According to the flow direction and boundary conditions of the fluid, determining that the flow inlet and outlet are periodic boundaries, the wall surface boundary is a non-slip boundary, and setting corresponding boundary types on the geometric model after grid division to obtain a grid model of square channel turbulent flow.
  3. 3. The method for calculating and analyzing the particle aggregation growth process in the turbulence of the square channel according to claim 1, wherein in the steps of establishing a turbulence mathematical model and solving a flow field, a mathematical model of the turbulence flow of the square channel is established based on a Navier-Stokes equation, the Reynolds number and the flow state parameter at the initial moment of the turbulence are determined by determining parameters such as the density, the viscosity and the average flow velocity of the turbulence fluid of the square channel, the boundary condition of the mathematical model is set according to the boundary type corresponding to the boundary of the grid model, the Reynolds number and the flow parameter at the initial moment are input into the mathematical model, the mathematical model is discretely solved by adopting a spectral unit method, wherein the position of a space discrete point can be determined by a Galerkin estimation method, the velocity can be represented by a Lagrange polynomial interpolation of N order, the velocity of a polynomial related to the pressure is lower by two orders, and the velocity and pressure distribution data of the turbulence secondary flow of the square channel is obtained by statistical analysis; In the step of establishing a fluid mathematical model and solving a flow field, the specific form of a mass equation and a momentum conservation equation contained in a Navier-Stokes equation can be written as follows: Wherein, the Is the velocity of the turbulent fluid in a square channel, The time is represented by the time period of the day, Is the instantaneous pressure of the fluid and, Representing the reynolds number of the turbulent flow, Is the viscous stress tensor of the fluid, Is an additional source item that is to be added, Indicating the reaction force exerted by the particles on the fluid.
  4. 4. The method for calculating and analyzing the particle coalescence growth process in the turbulence of the square channel according to claim 1, wherein in the step of constructing the particle motion equation, physical attribute parameters of the particles are obtained, specifically including the density, the initial particle size and the collision recovery coefficient between the particles, and the motion equation of the particles is constructed by combining various hydrodynamic forces applied to the particles in the turbulence of the square channel, wherein the various hydrodynamic forces include fluid drag force, saffman lift force, additional mass force, pressure gradient force, gravity and buoyancy force; in the step of constructing the particle motion equation, the motion equation of the particle is established by considering various hydrodynamic forces born by the particle in the turbulence of the square channel, and the specific form of the motion equation can be written as: Wherein, the Is the velocity of the particles and, Is the position of the particles and, Is the density of the fluid which is to be measured, Is the density of the particles and, Is the particle size of the particles, Is the slip speed between the phases of the vehicle, Is the degree of rotation of the fluid, Is the acceleration of gravity and, And The drag and lift correction coefficients, respectively.
  5. 5. The method for calculating and analyzing the particle coalescence growth process in the turbulence of the square channel according to claim 1, wherein in the step of obtaining motion information by solving the particle motion equation, the obtained turbulence flow field speed data is input into the constructed particle motion equation, the four-order Longku tower method is adopted to carry out numerical solution on the motion equation of the particles, in the solving process, the hard sphere model is adopted to describe the collision effect among the particles, the complete elastic collision model is adopted to describe the collision effect among the particles and the wall surface, and the spatial position coordinates, the speed vector and the stress distribution condition of the particles in the square channel are obtained through numerical solution.
  6. 6. The method for calculating and analyzing particle agglomeration and growth process in square channel turbulence according to claim 1, wherein in the step of constructing the particle-particle collision-agglomeration and collision-rupture action model, parameters such as a Hamek constant, a yield pressure, a minimum contact distance, a collision recovery coefficient and the like of the particles are input, and according to a particle collision energy dissipation theory and a DLVO theory, van der Waals force among the particles is considered, and a viscous particle collision-agglomeration and collision-rupture action model is established to judge whether the particles are agglomerated or ruptured, wherein a specific formula for judging whether the particles are collided-agglomerated can be written as follows: Wherein, the Is a unit vector of the number of units, Is a hammock constant value that is set to a value, Is the maximum yield pressure of the material to be processed, Is the minimum contact distance that is required for the contact, Is the forward collision recovery coefficient, superscript—indicates the variable before collision, while tables 1 and 2 below indicate the labels of the two particles that collide. The particle collision-fracture action model is obtained by analyzing the relative magnitude of hydrodynamic stress to which the particle mass is subjected and the mechanical strength of the particle mass.
  7. 7. The method for calculating and analyzing particle aggregation growth process in square channel turbulence according to claim 1, wherein in the step of calculating and obtaining the original particle information of aggregation and rupture behavior, the particle velocity and position distribution data obtained by solving the particle motion equation are input into a collision-aggregation and collision-rupture model calculation formula, and the velocity, position and particle diameter data corresponding to the particles with aggregation and rupture behavior before aggregation or rupture behavior occurs are analyzed and judged.
  8. 8. The method for calculating and analyzing the particle agglomeration growth process in the turbulence of the square channel according to claim 1, wherein in the step of calculating and acquiring the particle mass information after the agglomeration and rupture actions, a derivative formula describing the particle agglomeration process based on a momentum conservation principle is acquired, the original particle velocity, position and particle diameter data of the agglomeration or rupture actions are imported into the formula, the particle mass position, velocity and particle diameter after the agglomeration and rupture actions are calculated, the turbulence field velocity distribution at the particle mass position is obtained through a Lagrange interpolation method, and the accurate description of the viscous particle agglomeration growth process in the turbulence field of the square channel is realized.
  9. 9. The method for calculating and analyzing particle agglomeration and growth process in square channel turbulence according to claim 8, wherein in the step of calculating and obtaining particle mass information after agglomeration and rupture, a derivative formula describing the particle agglomeration and growth process based on a principle of conservation of momentum is obtained, raw particle velocity, position and particle diameter data of agglomeration or rupture are imported into the formula, and the position, velocity and particle diameter of the particle mass after agglomeration and rupture are calculated, wherein the derivative formula of the principle of conservation of momentum is written as follows: Wherein, the In order to achieve a velocity of the particle agglomeration, In order to locate the particle agglomerates, Is the particle size of the particle agglomerate, Is the particle size of the particles, Is the time of the collision superposition, And The collision velocity and particle position of the particles before coalescence, respectively, are shown in tables 1 and 2 below.
  10. 10. The method for calculating and analyzing the particle aggregation growth process in the square channel turbulence according to claim 1, wherein in the step of constructing a fluid-particle inter-phase coupling action model and updating and solving a flow field, under the premise that the particle size distribution rule of particles changes, the stress distribution of particle aggregates after collision aggregation and collision rupture behavior is recalculated according to each acting force calculation formula of particles involved in a particle motion equation, the reaction influence of all particles and particle aggregate motion on a turbulence field is considered, a fluid-particle motion inter-phase coupling action model is established, a formula value corresponding to the model is used as a source term to be input into a Navier-Stokes equation, the initial Navier-Stokes equation is corrected, the speed, the pressure and the secondary flow distribution of the square channel turbulence field are obtained by re-solving, the update of the turbulence field and the coupling calculation of the subsequent particle aggregation growth dynamic process and the turbulence field are realized until the particle aggregation and rupture behavior in the turbulence field reaches a dynamic state, and the particle size distribution rule of the particles does not change any more; In the steps of constructing a fluid-particle inter-coupling action model and updating and solving a flow field, the fluid-particle motion inter-coupling action model is established, and a formula corresponding to the fluid-particle motion inter-coupling action model can be written as: Wherein, the Is the calculation of the volume of the grid cells, The number of particles contained in the grid cell is calculated and the subscript j is the number of particles in the calculated grid cell.

Description

Calculation and analysis method for particle coalescence growth process in turbulence of square channel Technical Field The invention relates to the technical field of fluid mechanics, in particular to a calculation and analysis method for particle coalescence growth process in turbulence of a square channel. Background The two-phase turbulence phenomenon of square channel particles relates to a plurality of industrial fields such as petrochemical industry, environmental protection, nuclear industry and the like, for example, a pneumatic dust removal system such as desulfurization, denitration and the like in the petrochemical industry, dust-containing gas is connected to a dust remover through a square channel, dust particles in the dust remover need to be effectively separated and removed, a ventilation pipeline system in a large building, air containing pollutant particles is conveyed outdoors through the square channel, and nuclear waste treatment systems in the nuclear industry realize cyclic treatment of nuclear waste liquid containing solid-phase particles through various square channels. The particle materialization viscosity property difference in different industrial processes is larger, and the aggregation growth process of the viscous particles can greatly influence the distribution characteristics and migration rules of the particles in the processes, so that the conveying efficiency of related pipelines and the safe operation of equipment are directly influenced. Calculating and analyzing the aggregation growth process of viscous particles in turbulence of a square channel, accurately predicting the migration distribution characteristics of the particles in the related industrial process, and further having important engineering guidance significance for regulating and controlling the operation parameters of the corresponding pipelines, optimizing the design of industrial equipment and improving the safety of a process system. The current method for describing and analyzing the particle coalescence growth process in the square channel two-phase turbulence mainly comprises an experimental measurement method and a numerical simulation method, wherein the experimental measurement method mainly comprises the steps of constructing an experimental device and measuring the fluid speed, the particle position and the particle size based on experimental equipment such as a particle imaging velocimeter, a laser particle size analyzer and the like, but the method is high in experimental cost, long in experimental period, large in applicable scene limitation and difficult to apply to complex industrial scenes. For a square channel single-phase turbulent flow field, the typical characteristic of the square channel single-phase turbulent flow field, which is different from a circular straight pipe turbulent flow, is that secondary flow caused by turbulent flow anisotropic distribution is generated on the cross section of the channel, the size of the square channel single-phase turbulent flow field is only 1% -3% of the main flow speed, and the square channel single-phase turbulent flow field can have great influence on the average flow field, wall friction force, heat and mass transfer and particle movement behaviors in the square channel single-phase turbulent flow field. The secondary flow velocity value is smaller, the measurement accuracy and the measurement stability of the secondary flow velocity value are also greatly limited by the traditional experimental method, and the numerical simulation method commonly used in the existing engineering comprises a Reynolds average method and a large vortex simulation method. The numerical simulation method for the particle aggregation process in the conventional two-phase turbulent flow field mainly comprises a discrete element method based on a single-track particle model and a population balance model method based on a double-fluid model, wherein the discrete element method needs to solve the dynamic behaviors of single particles, is large in calculation amount, is difficult to adapt to a large-scale industrial system, is high in calculation accuracy due to the fact that the contact between particles and the parameter setting of the contact between particles are limited, the influence of particles on the flow field cannot be considered by the discrete element method alone, the solving accuracy is limited, the complexity of the population balance model method is high, the accuracy dependence on priori parameters such as aggregation kernels and breakage rate is high, tracking calculation and analysis on the aggregation growth process of the single particles cannot be carried out, and the diversified requirements of industrial application are difficult to meet. Currently, no calculation and analysis technology for particle coalescence growth process in square channel turbulence exists in the prior art. Disclosure of Invention The invention aims to provide a calcu