CN110232222B - Sediment tube flow field analysis method and system - Google Patents

Sediment tube flow field analysis method and system Download PDF

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CN110232222B
CN110232222B CN201910437839.4A CN201910437839A CN110232222B CN 110232222 B CN110232222 B CN 110232222B CN 201910437839 A CN201910437839 A CN 201910437839A CN 110232222 B CN110232222 B CN 110232222B
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赵彦琳
姚军
刘敏
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China University of Petroleum Beijing
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Abstract

The invention provides a method and a system for analyzing a flow field of a deposition tube, wherein the method comprises the following steps: obtaining a geometric model of fluid in the deposition tube formed by a circular tube with a deposition layer; defining and determining a Reynolds number of the fluid; and carrying out numerical calculation and flow field analysis on the geometric model according to the Reynolds number, and analyzing the fluid flow state in the deposition tube by using numerical calculation and flow field analysis methods.

Description

Sediment tube flow field analysis method and system
Technical Field
The invention relates to the technical field of sediment tube fluid analysis, in particular to a sediment tube fluid field analysis method and system.
Background
Oil, gas and water transportation pipelines are commonly used in daily life and industrial production, and the flow cross section of the pipelines is mostly circular. The multiphase flow is an important component in the multiphase flow, and is widely applied to the fields of environmental protection, pharmacy, metallurgy, building materials, energy, chemical engineering, aerospace and the like. If solid phase particles are present in the pipe, such as gas-solid or liquid-solid two-phase flow, the solid phase particles may settle under the action of gravity.
During the transportation process of the pipeline, solid-phase particles in the fluid medium move downwards under the action of gravity and deposit on the wall surface of the pipeline to form a deposition layer in time, so that the cross-sectional area is reduced, and an angle is formed between the deposition layer and the arc-shaped wall surface. At present, no analysis technology for the fluid flow state in the deposition tube exists in the prior art.
Disclosure of Invention
An object of the present invention is to provide a deposition tube fluid field analysis method, which provides a geometric model of a deposition tube with a deposition layer and analyzes a fluid flow state in the deposition tube through a numerical calculation and a flow field analysis method. It is another object of the present invention to provide a deposition tube field analysis system. It is a further object of this invention to provide such a computer apparatus. It is a further object of this invention to provide such a readable medium.
In order to achieve the above objects, in one aspect, the present invention discloses a method for analyzing a field of a deposition tube, comprising:
obtaining a geometric model of fluid in the deposition tube formed by a circular tube with a deposition layer;
defining and determining a Reynolds number of the fluid;
and performing numerical calculation and flow field analysis on the geometric model according to the Reynolds number.
Preferably, the geometric model of the fluid is a horizontally arranged cylindrical body, the cross-sectional profile of the cylindrical body comprises an arc with an opening at the bottom end and horizontally arranged straight lines respectively connected with two ends of the opening, and the distance between the straight lines and the arc is determined according to the thickness of the deposition layer.
Preferably, the numerically calculating the geometric model according to the reynolds number specifically includes:
meshing the geometric model of the fluid;
setting a geometric model after meshing according to the Reynolds number to obtain an analysis model;
and carrying out numerical calculation on the analysis model.
Preferably, meshing the geometric model of the fluid specifically comprises:
selecting at least one grid type;
dividing the geometric model into a plurality of areas or carrying out mesh division on the geometric model by solving an elliptic differential equation method;
and carrying out encryption processing on the grids of the boundary layer area.
Preferably, the setting of the geometric model after meshing according to the reynolds number to obtain the analysis model specifically includes:
determining a fluid flow state parameter of the fluid according to the section size and Reynolds number of the geometric model of the fluid;
and setting the fluid flow state parameters and the constraint conditions on the geometric model to obtain the analysis model.
Preferably, the setting of constraints on the geometric model specifically comprises:
setting a boundary condition type;
arranging a fluid inlet, a fluid outlet and a flow direction of a fluid;
and setting a non-slip boundary condition.
Preferably, the flow field analysis includes an average flow field analysis and a transient flow field analysis.
The invention also discloses a sediment tube flow field analysis system, which comprises:
a geometric model unit for obtaining a geometric model of the fluid in the deposition tube formed by the circular tube in which the deposition layer exists;
a parameter determination unit for defining and determining the Reynolds number of the fluid;
and the solving and analyzing unit is used for carrying out numerical calculation and flow field analysis on the geometric model according to the Reynolds number.
The invention also discloses a computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor,
the processor, when executing the program, implements the method as described above.
The invention also discloses a computer-readable medium, having stored thereon a computer program,
which when executed by a processor implements the method as described above.
According to the invention, a geometric model for analyzing the fluid flow field is constructed according to the structural characteristics of the deposition tube, the flow state numerical value of the fluid in the deposition tube is obtained through numerical calculation, and the flow field analysis is further carried out on the flow state numerical value distribution of the fluid in the deposition tube, so that the flow characteristics of the fluid in the deposition tube with different deposition layer thicknesses, such as secondary flow in the flow field and the influence of the secondary flow on the flow field, can be theoretically analyzed, and the problems of particle deposition and the like of pipeline transportation in engineering can be further researched.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 shows one of the flow charts of one embodiment of a method of analyzing a deposition tube field of the present invention;
FIG. 2 illustrates a second flow diagram of an embodiment of a method for analyzing a deposition tube field according to the present invention;
FIG. 3 is a schematic representation of a geometric model of one embodiment of a method of analyzing a deposition tube field of the present invention;
FIG. 4 is a schematic diagram illustrating the design of a geometric model according to an embodiment of the deposition tube fluid field analysis method of the present invention;
FIG. 5 is a third flow chart of an embodiment of a method of analyzing a deposition tube field of the present invention;
FIG. 6 is a fourth flowchart of an embodiment of a method of analyzing a deposition tube field of the present invention;
FIG. 7 shows a fifth flowchart of an embodiment of a method of analyzing a deposition tube field of the present invention;
FIG. 8 shows a sixth flowchart of an embodiment of a method of analyzing a deposition tube field of the present invention;
FIG. 9 shows a seventh flowchart of an embodiment of a method of analyzing a deposition tube field of the present invention;
FIG. 10 is a schematic diagram illustrating geometric model meshing in one embodiment of a method for sediment tube fluid field analysis of the present invention;
FIG. 11a is a schematic view showing a cross-sectional flow line in the result of numerical calculation of a specific example of a method of analyzing a deposition tube fluid according to the present invention;
FIG. 11b is a second schematic view of cross-sectional flow lines in the numerical calculation results of a specific example of the method for analyzing a deposition tube fluid field according to the present invention;
FIG. 11c is a schematic third drawing showing a cross-sectional streamline in the numerical calculation result of a specific example of the method for analyzing a deposition tube fluid field according to the present invention;
FIG. 12a is a schematic view showing a flow velocity cloud in the result of numerical calculation of a specific example of a deposition tube fluid field analysis method according to the present invention;
FIG. 12b is a second schematic view of a cloud of flow velocities from the numerical calculations of a specific example of a deposition tube fluid field analysis method according to the present invention;
FIG. 12c is a third schematic view of a cloud of flow velocities obtained from numerical calculations for a particular example of a deposition tube fluid field analysis method according to the present invention;
FIG. 13a is a schematic view of a secondary flow cloud in the numerical calculation results of a specific example of a deposition tube fluid field analysis method according to the present invention;
FIG. 13b is a second schematic diagram of a second cloud of secondary flows in the numerical calculation results of a specific example of a deposition tube fluid field analysis method according to the present invention;
FIG. 13c is a third schematic diagram of a second cloud in the numerical calculation of a specific example of a deposition tube fluid field analysis method according to the present invention;
FIG. 14 is a block diagram of one embodiment of a deposition tube flow field analysis system according to the present invention;
FIG. 15 shows a schematic block diagram of a computer device suitable for use in implementing embodiments of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In accordance with one aspect of the present invention, a method for analyzing a deposition tube field is disclosed. As shown in fig. 1, in this embodiment, the flow field analysis method includes:
s100: a geometric model of the fluid in the deposition tube is obtained from a circular tube in which the deposition layer is present.
S200: the reynolds number of the fluid is defined and determined.
S300: and performing numerical calculation and flow field analysis on the geometric model according to the Reynolds number.
According to the invention, a geometric model for analyzing the fluid flow field is constructed according to the structural characteristics of the deposition tube, the flow state numerical value of the fluid in the deposition tube is obtained through numerical calculation, and the flow field analysis is further carried out on the flow state numerical value distribution of the fluid in the deposition tube, so that the flow characteristics of the fluid in the deposition tube with different deposition layer thicknesses, such as secondary flow in the flow field and the influence of the secondary flow on the flow field, can be theoretically analyzed, and the problems of particle deposition and the like of pipeline transportation in engineering can be further researched.
In a preferred embodiment, as shown in fig. 2, the method further comprises:
s000: and constructing a geometric model of the fluid in the deposition pipe formed by the circular pipe with the deposition layer.
In the process of constructing the geometric model of the fluid, the fluid flow in the deposition tube with the deposition layer can be simplified according to a certain rule to obtain the geometric model of the fluid in the deposition tube under the condition of not obviously developing the result of the flow-dependent field analysis, and the specific simplification rule can comprise the following items:
(1) neglecting the attachment of particles on the arc-shaped wall surface of the deposition tube and the complex behavior of precipitates in the medium in the pipeline.
(2) It is assumed that the deposited layer forms a straight interface under the flushing of the fluid.
(3) It is assumed that the deposited layer does not change in thickness, shape and position with the fluid flow.
Therefore, when the geometric model is constructed, a circle representing the deposition tube and a straight line representing the interface of the deposition layer and the fluid can be drawn firstly, the straight line is intersected with the circle, the area representing the portion of the deposition layer formed by the intersection of the straight line and the circle is cut off to obtain the cross section of the geometric model, and the rest portion is stretched along the axial direction of the deposition tube, namely, the stretching along the direction vertical to the cross section to form the geometric model of the required fluid.
Specifically, as shown in fig. 3 and 4, the geometric model of the fluid is a horizontally arranged cylindrical body, the cross-sectional profile of the cylindrical body includes an arc with an opening at the bottom end and horizontally arranged straight lines respectively connected with two ends of the opening, and the distance between the straight lines and the arc is determined according to the thickness of the deposition layer. The upper part of the section is an arc boundary, the lower side of the section is a linear boundary, the arc boundary and the lower side of the section form an angle, and the length of the upper boundary and the lower boundary, the angle formed by the linear boundary and the arc boundary, the section area, the section perimeter, the section hydraulic diameter and the like are correspondingly changed along with the up-down movement of the lower boundary. According to different thicknesses of the deposition layers, geometric models with different sections can be formed, the influence of the deposition layers in the deposition pipe on the fluid flow is fully considered by the geometric models in the embodiment, and therefore the accuracy of flow field analysis results is guaranteed.
In a preferred embodiment, as shown in fig. 5, the S300 may include:
s310: meshing the geometric model of the fluid.
S320: and setting a geometric model after meshing according to the Reynolds number to obtain an analysis model.
S330: and carrying out numerical calculation on the analysis model.
In a preferred embodiment, as shown in fig. 6, the S310 may specifically include:
s311: at least one mesh type is selected. For example, since the geometric model in the deposition tube includes an arc boundary, the geometric model may be gridded using an O-mesh to fit the arc boundary, resulting in a high quality mesh. Because the lower part of the arc is a straight line boundary and the position of the straight line boundary is not fixed, the grid is processed differently below the circle center, for example, hexahedron and tetrahedron grids can be adopted, the grid quality is improved, and the accuracy of a data simulation result is improved.
S312: the geometric model is divided into a plurality of regions or is meshed by solving an elliptic differential equation method. The geometric model of the deposition tube comprises an arc boundary and a straight line boundary, the geometric model can be divided into a plurality of areas, and different meshes are selected for division according to the geometric structure characteristics of different areas.
S313: and carrying out encryption processing on the grids of the boundary layer area. It is understood that in fluid mechanics, a boundary layer is an artificially divided area in which a fluid flows near a wall surface, and a boundary layer range is selected near the wall surface in a calculation process to perform grid encryption processing on the boundary layer, and preferably, the boundary layer can be encrypted in an exponential form.
In a preferred embodiment, as shown in fig. 7, the S320 may specifically include:
s321: and determining the fluid flow state parameters of the fluid according to the section size and Reynolds number of the geometric model of the fluid.
S322: and setting the fluid flow state parameters and the constraint conditions on the geometric model to obtain the analysis model.
Wherein the fluid flow state parameter may comprise an average velocity of the fluid flow direction. Reynolds numbers are defined from the average velocity of the fluid flow and the cross-section of the geometric model and can be used to indicate flow conditions. The reynolds number is defined as the ratio of the average velocity of the flow direction multiplied by the hydraulic diameter of the conduit to the kinematic viscosity of the fluid as it flows along the conduit. The Reynolds number is less than the critical Reynolds number, and the flow field is laminar flow; the Reynolds number is larger than the critical Reynolds number, and the flow field is turbulent. When the Reynolds number is in an excessive interval, the flow field is in a critical state. When the fluid in the deposition tube is subjected to turbulent flow field analysis, the Reynolds number of the fluid forming turbulent flow is determined, and the value of the average flowing speed of the fluid can be obtained according to the relation between the Reynolds number and the average flowing speed of the fluid and is used as the flowing state parameter of the fluid.
In a preferred embodiment, as shown in fig. 8, the setting of the constraint condition on the geometric model in S322 may include:
s3221: the boundary condition type is set. Periodic boundary conditions or aperiodic boundary conditions may be employed. In order to prevent insufficient fluid development from affecting the results of the calculations, periodic boundary conditions are preferably employed.
S3222: fluid inlets, outlets and flow directions of the fluids are provided. Specifically, the geometric model is provided with the flow rate, the speed, the pressure and the like of the fluid inlet and the fluid outlet, and the flow direction is set as the pipeline direction.
S3223: and setting a non-slip boundary condition. Namely, the boundary of the geometric model along the extension direction of the deposition tube adopts a non-slip boundary condition.
In a preferred embodiment, as shown in fig. 9, the S330 may specifically include:
s331: and obtaining a pressure correction model by adopting a numerical simulation model according to the velocity distribution and the pressure distribution of the fluid. To improve accuracy, the numerical simulation model must exhibit the anisotropy of reynolds stress. Preferably, the Navier-Stokes (NS) equation can be solved, when the turbulent flow field is analyzed, a turbulent flow model can be used for solving an average flow field, a sub-lattice stress model can be used for solving a large-scale vortex, and a full-scale direct numerical solution can be also used. When the Navier-Stokes equation is solved, a Reynolds stress transport model and a dissipation rate model can be selected for sealing. Wherein an initial velocity profile and pressure profile can be assumed in advance.
S332: and correcting the pressure and the speed of the fluid according to the pressure correction model. And calculating a discrete equation constant term in the numerical simulation model and further solving a pressure correction equation according to the assumed initial velocity distribution and pressure distribution so as to correct the velocity distribution and the pressure distribution, and further solving other discretization equations in the data simulation model according to the corrected velocity distribution and pressure distribution.
S333: and repeating the steps until a preset iteration condition is met to obtain a numerical calculation result of the fluid flow. And (3) continuously correcting the velocity distribution and the pressure distribution in the fluid flow by repeating the steps S410 and S420 until a preset iteration condition is met to obtain a numerical calculation result of the fluid flow, wherein the numerical calculation result comprises flow state parameters such as flow velocities of fluids at different positions in the geometric model, and the fluid state in the sedimentation tube can be obtained by analyzing according to the flow state parameters of each point in the fluid flow.
The invention is further illustrated below by means of a specific example. In a specific example, the flow field analysis method of the present embodiment is used to perform numerical simulation and theoretical analysis on the liquid-solid two-phase flow field in the circular tube. The fluid in the pipeline is liquid-solid two-phase flow, the solid phase deposition in the fluid in the pipeline enables the circular pipe to become a deposition pipe, and the deposition layer in the deposition pipe forms the generating condition of secondary flow. The secondary flow is the flow of the fluid on the flow cross section and is related to the existence of the flow direction vortex. The secondary flows are divided into two categories, the first being pressure driven secondary flows and the second being turbulently driven secondary flows. A first type of secondary flow, such as a bent-tube secondary flow, may be generated due to lateral vortex deflection caused by a bent tube; the second type of secondary flow is the square tube secondary flow, and the generation of the secondary flow is related to the Reynolds stress gradient generated by a complex section.
The generation of the secondary flow is influenced by the arc, the angle and the chord length, so that the complexity is high, and the prediction of the secondary flow is difficult. In addition, turbulent secondary flow can affect a flow field, and the cross section distribution of particles can be changed for liquid-solid and gas-solid multi-phase flow. Therefore, the research of the secondary flow is very challenging, and can provide a solution for the problem of pipeline particle deposition, so that the method has theoretical significance and practical value.
First, a geometric model of the turbulent flow of the deposition tube is constructed. The geometric model is a horizontally arranged cylindrical body, and the cross section profile of the cylindrical body comprises an arc with an opening at the bottom end and a horizontally arranged straight line respectively connected with the two ends of the opening. The radius of the arc representing the deposition tube is r, the diameter is D, the geometric model length L representing the tube length is 20D, and the deposition layer thickness is HbCan order Hb0.25r, 0.5r or r to form three geometric models with different deposition layer thicknesses, depending on the deposition layer HbThe thickness of (a) determines the distance d between the straight boundary of the deposit and the center of the arc, i.e. d-r-Hb。
And a three-dimensional coordinate system is arranged, x, y and z respectively correspond to the radial horizontal direction, radial vertical direction and axial direction of the deposition tube, the origin of coordinates is the center of a circular arc, a right-hand coordinate system is adopted, and the fluid positively flows along the z axis.
The geometric model of the turbulent flow is subjected to mesh division by using an O-shaped mesh to adapt to an arc boundary, and the meshes in the boundary layer region are subjected to encryption processing to obtain a high-quality mesh so as to ensure the accuracy of the calculation result, as shown in fig. 10.
And setting a boundary condition, and determining the fluid flow state parameters of the turbulent fluid according to the section size of the geometric model of the turbulent fluid and the Reynolds number corresponding to the turbulence. Wherein the Reynolds number Re is defined as:
Figure BDA0002071101490000081
Figure BDA0002071101490000082
wherein, UbTo average velocity of flow, DHIs the hydraulic diameter of the section, A is the area of the section, l is the perimeter of the section, and v is the kinematic viscosity of the fluid.
According to the above formula, the average speed of the turbulent flow direction can be obtained by calculating the selected Reynolds number Re 80000 for different deposition thicknesses.
Setting the type of the boundary condition as a periodic boundary condition, setting the fluid inlet, the fluid outlet and the flow direction of turbulent fluid and setting a non-slip boundary condition to obtain an analysis model.
In the embodiment, the calculation of the analysis model is based on a time-averaged NS equation, and the applied model is a Reynolds Stress Model (RSM) turbulence model to perform simulation analysis on the analysis model to respectively obtain numerical calculation results.
Specifically, this example was studied on a three-dimensional level. The incompressible in the deposition tube, based on the time-averaged Navier-Stokes equation, the mass and momentum conservation equation for fully developing turbulence can be written as:
Figure BDA0002071101490000083
Figure BDA0002071101490000084
wherein i is 1, 2 or 3, j is 1, 2 or3, wherein 1, 2 and 3 correspond to x, y, z directions, u, respectivelyiFor fluid velocity in i direction, ujFor fluid velocity in j direction, xiTo correspond to the position in the i direction, xjTo correspond to the position in the i direction, τijIn Reynolds stress, ρ is the fluid density, t is the time, giP is the pressure corresponding to the mass force in the i direction.
A Reynolds Stress Model (RSM) is adopted to carry out numerical simulation, isotropic vortex viscosity assumption is abandoned, and a Navier-Stokes equation of Reynolds average is closed by solving a transmission equation of Reynolds stress and an equation of dissipation rate.
When the fluid flows along the pipeline, different flow fields can be obtained by adjusting the thickness and Reynolds number of the deposition layer. When the thickness of the deposition layer is 0, the pipeline is a circular pipe and does not flow for the second time; when the Reynolds number is small, the flow field is laminar flow and has no secondary flow. When the deposition layer reaches a certain thickness, the Reynolds number is increased, the flow field reaches a critical state, and finally the flow field is converted into turbulent flow, and secondary flow is generated.
The flow field analysis includes an average flow field analysis and a flow field analysis. The distribution information of the velocity vector of the secondary flow in the section, such as the size, the direction, the position and the like, can be analyzed through a flow field analysis result obtained by numerical simulation, the distribution information of turbulence energy, Reynolds stress, wall shear stress in the section can be analyzed, the relation between the distribution information and the secondary flow can be analyzed, the generation and development mechanisms of the secondary flow can be analyzed and predicted, and the turbulence characteristic of the section can be clarified.
When H is presentbWhen the reynolds number Re is 0.5r and 80000, the secondary flow line obtained from the flow field analysis result is shown in fig. 11a, where DH is the cross-sectional hydraulic diameter. The secondary flows near the center are referred to as inner secondary flows (e.g., 1 and 2 in fig. 11 a-11 c), and the secondary flows on both sides are referred to as outer secondary flows (e.g., 3 and 4 in fig. 11 a-11 c). Secondary vortices are generated near the straight wall surface. No vortices of comparable size occur near the curved wall, and the bisector of the angle is only tangent to the inner and outer secondary flows at the closest corner. The outer side only produces a relatively small secondary flow closest to the corners. Inner secondary flow from center along angular bisectorThe outer side flows to the corner and returns to the center from the bisector of the straight wall surface. Thickness H of the deposition layerbThe cross-sectional flow diagrams of 0.75r and r are shown in fig. 11b and 11c, respectively. The outer secondary flow increases with increasing thickness of the deposited layer.
The distribution of the turbulent flow direction velocity on the cross section can be analyzed through the fluid flow obtained by the numerical simulation, and the influence of the secondary flow on the flow direction velocity can be observed. The secondary flow obtained from the flow field analysis results was plotted with a constant velocity profile of the flow direction velocity as shown in fig. 12 a-12 c. Near the wall surface of the deposition tube, the isovelocity line is parallel to the wall surface. Because the outer side does not generate larger vortex, the secondary flow is near the arc-shaped wall surface along the tangential direction of the wall surface, and the main flow velocity at the wall surface of the deposition tube does not obviously deform. On the contrary, the inner secondary flow transfers the high-speed fluid at the center to the corner formed by the arc and the straight line, and transfers the low-speed fluid close to the wall surface to the center at the bisector of the straight line wall surface, so that the main flow velocity line is convex downwards at the position close to the corner, and is convex upwards at the bisector of the straight line wall surface. As the deposited layer thickness Hb increases, the degree of curvature of the streamwise velocity contours in the cross-section decreases. The degree of curvature of the streamwise velocity contours is related to the secondary flow, which indicates where the secondary flow decreases with increasing thickness of the deposited layer.
Fig. 13 a-13 c are secondary flow size cloud charts using flow direction velocity non-dimensionalization. It can be seen that for different deposit thicknesses, the secondary flow is at a maximum at the deposit, at the bisector and at the camber. But when Hb is 0.5r and 0.75r, the secondary flow reaches a maximum at the bisector, which represents the superposition of the inboard vortex at the center; and when Hb is r, the secondary flow has a maximum value at the straight wall surface, indicating that the superposition of the secondary flow at the center is weakened. The maximum value of the secondary flow under different cross sections is about 2 percent, and is the same as that of the square tube. The magnitude of the outer secondary flow is always smaller than the inner secondary flow for different cross sections, further indicating the inhibiting effect of the arc on the secondary flow. The secondary flow reaches a maximum at the straight wall, and therefore the use of a wall function needs to be avoided. Because the outside secondary flow is restrained from developing, at the position far away from the corner, the inside vortex and the outside vortex are not symmetrical with each other by a diagonal line any more, the inside secondary flow obtains a larger development space, and the development of the inside secondary flow is promoted. The secondary flow on the diagonal increases as the deposited layer thickness increases. This is because the outer secondary flow gradually increases, the size of the adjacent vortex at the corner gradually approaches, the tangent line of the adjacent vortex gradually approaches the angular bisector, and finally a larger secondary flow from the center to the corner is formed at the diagonal line. The minima on either side of the symmetry line represent the vortex centre. The comparison of the secondary flows in the upper and lower sections of the cross-section reveals that the secondary flows are generated at the corners, mainly in the lower half, and very small at the top of the cross-section.
In summary, turbulent flow in a straight pipe with sedimentary layers creates a second type of secondary flow in cross section. The secondary flow is generated and developed at the corners and causes variations in the cross section of the flow direction velocity and the like. The arc has an inhibiting effect on secondary flow, and the secondary flow speed near the arc wall surface is reduced; the smaller angle can promote the turbulent interaction, and is beneficial to the generation of secondary flow; the confining effect between the inner and outer secondary flows creates an effect that they cancel as the thickness of the deposited layer changes. The results show that there is a consistency of mechanism between the secondary flow of the deposition tube with the deposited layer and the secondary flow of other flow fields and a difference of the secondary flow caused by geometrical factors. The invention firstly provides a geometric model of the deposition tube, considers different characteristics of a flow field under different deposition thicknesses, and deeply analyzes the influence of geometric factors on secondary flow. Through the analysis to the secondary flow influence factor, can realize the control to the secondary flow, provide the solution for solving the relevant problem of granule deposit in the pipeline. The generated secondary flow can generate other influences on the flow field, and the original distribution of the physical quantity in the flow field is changed.
Due to the existence of the secondary flow, the method has higher application value in engineering application. This circular duct shape can be used to create when a secondary flow is required. By adjusting the deposition layer thickness and the flow rate, a certain velocity in the vertical upward direction can be obtained at the center, and this velocity can be obtained without the need for pipe bends or other conditions. The method provides a new solution for solving the problems of general pipeline deposition and blockage and other pipeline transportation problems.
Based on the same principle, the embodiment also discloses a sediment tube flow field analysis system. As shown in fig. 14, the sediment tube flow field analysis system includes a geometric model unit 11, a parameter determination unit 12, and a solution analysis unit 13.
The geometric model unit 11 is used to obtain a geometric model of the fluid in the deposition tube formed by a circular tube in which the deposition layer is present.
The parameter determination unit 12 is used to define and determine the reynolds number of the fluid.
The solving and analyzing unit 13 is configured to perform numerical calculation and flow field analysis on the geometric model according to the reynolds number. Wherein the flow field analysis comprises an average flow field analysis and a flow field analysis.
According to the invention, a geometric model for analyzing the fluid flow field is constructed according to the structural characteristics of the deposition tube, the flow state numerical value of the fluid in the deposition tube is obtained through numerical calculation, and the flow field analysis is further carried out on the flow state numerical value distribution of the fluid in the deposition tube, so that the flow characteristics of the fluid in the deposition tube with different deposition layer thicknesses, such as secondary flow in the flow field and the influence of the secondary flow on the flow field, can be theoretically analyzed, and the problems of particle deposition and the like of pipeline transportation in engineering can be further researched.
In a preferred embodiment, the geometric model unit 11 is further configured to construct a geometric model of the fluid in the deposition tube formed by the circular tube in which the deposition layer is present.
In the fluid geometric model building process, the geometric model unit 11 may simplify the fluid flow in the deposition tube with the deposition layer according to a certain rule without obviously influencing the flow field analysis result to obtain the geometric model of the fluid in the deposition tube, where the simplified rule may include the following items:
(1) neglecting the attachment of particles on the arc-shaped wall surface of the deposition tube and the complex behavior of precipitates in the medium in the pipeline.
(2) It is assumed that the deposited layer forms a straight interface under the flushing of the fluid.
(3) It is assumed that the deposited layer does not change in thickness, shape and position with the fluid flow.
Therefore, when the geometric model is constructed, a circle representing the deposition tube and a straight line representing the interface of the deposition layer and the fluid can be drawn firstly, the straight line is intersected with the circle, the area representing the portion of the deposition layer formed by the intersection of the straight line and the circle is cut off to obtain the cross section of the geometric model, and the rest portion is stretched along the axial direction of the deposition tube, namely, the stretching along the direction vertical to the cross section to form the geometric model of the required fluid.
Specifically, as shown in fig. 3 and 4, the geometric model of the fluid is a horizontally arranged cylindrical body, the cross-sectional profile of the cylindrical body includes an arc with an opening at the bottom end and horizontally arranged straight lines respectively connected with two ends of the opening, and the distance between the straight lines and the arc is determined according to the thickness of the deposition layer. The upper part of the section is an arc boundary, the lower side of the section is a linear boundary, the arc boundary and the lower side of the section form an angle, and the length of the upper boundary and the lower boundary, the angle formed by the linear boundary and the arc boundary, the section area, the section perimeter, the section hydraulic diameter and the like are correspondingly changed along with the up-down movement of the lower boundary. According to different thicknesses of the deposition layers, geometric models with different sections can be formed, the influence of the deposition layers in the deposition pipe on the fluid flow is fully considered by the geometric models in the embodiment, and therefore the accuracy of flow field analysis results is guaranteed.
In a preferred embodiment, the solution analysis unit 13 is specifically configured to perform meshing on the geometric model of the fluid, set the meshed geometric model according to the reynolds number to obtain an analysis model, and perform numerical calculation on the analysis model.
In a preferred embodiment, the solution analysis unit 13 is further configured to select at least one mesh type, divide the geometric model into a plurality of regions or perform mesh division on the geometric model by solving an elliptic differential equation method, and perform encryption processing on the meshes of the boundary layer region.
Wherein at least one mesh type is selected. For example, since the geometric model in the deposition tube includes an arc boundary, the geometric model may be gridded using an O-mesh to fit the arc boundary, resulting in a high quality mesh. Because the lower part of the arc is a straight line boundary and the position of the straight line boundary is not fixed, the grid is processed differently below the circle center, for example, hexahedron and tetrahedron grids can be adopted, the grid quality is improved, and the accuracy of a data simulation result is improved.
The geometric model is divided into a plurality of regions or is meshed by solving an elliptic differential equation method. The geometric model of the deposition tube comprises an arc boundary and a straight line boundary, the geometric model can be divided into a plurality of areas, and different meshes are selected for division according to the geometric structure characteristics of different areas.
And carrying out encryption processing on the grids of the boundary layer area. It is understood that in fluid mechanics, a boundary layer is an artificially divided area in which a fluid flows near a wall surface, and a boundary layer range is selected near the wall surface in a calculation process to perform grid encryption processing on the boundary layer, and preferably, the boundary layer can be encrypted in an exponential form.
In a preferred embodiment, the solution analysis unit 13 is specifically configured to determine the fluid flow state parameters of the fluid according to the cross-sectional dimension and the reynolds number of a geometric model of the fluid, and set the fluid flow state parameters and the constraint conditions on the geometric model to obtain the analysis model.
Wherein the fluid flow state parameter may comprise an average velocity of the fluid flow direction. Reynolds numbers are defined from the average velocity of the fluid flow and the cross-section of the geometric model and can be used to indicate flow conditions. The reynolds number is defined as the ratio of the average velocity of the flow direction multiplied by the hydraulic diameter of the conduit to the kinematic viscosity of the fluid as it flows along the conduit. The Reynolds number is less than the critical Reynolds number, and the flow field is laminar flow; the Reynolds number is larger than the critical Reynolds number, and the flow field is turbulent. When the Reynolds number is in an excessive interval, the flow field is in a critical state. When the fluid in the deposition tube is subjected to turbulent flow field analysis, the Reynolds number of the fluid forming turbulent flow is determined, and the value of the average flowing speed of the fluid can be obtained according to the relation between the Reynolds number and the average flowing speed of the fluid and is used as the flowing state parameter of the fluid.
In a preferred embodiment, the solution analysis unit 13 sets constraints on the geometric model, specifically, may be used to set boundary condition types, fluid inlets, fluid outlets, and fluid flow directions of the fluid, and a slip-free boundary condition.
Specifically, the boundary condition type may employ a periodic boundary condition or an aperiodic boundary condition. In order to prevent insufficient fluid development from affecting the results of the calculations, periodic boundary conditions are preferably employed.
The fluid inlet, the fluid outlet and the flow direction of the fluid are set, namely the flow rate, the speed, the pressure and the like of the fluid inlet and the fluid outlet can be set on the geometric model, and the flow direction is set to be the pipeline direction.
And setting a non-slip boundary condition, namely adopting the non-slip boundary condition on the boundary of the geometric model along the extension direction of the deposition tube.
In a preferred embodiment, the solution analysis unit 13 is specifically configured to obtain a pressure correction model by using a numerical simulation model according to the velocity distribution and the pressure distribution of the fluid, correct the pressure and the velocity of the fluid according to the pressure correction model, and repeatedly calculate the velocity publication and the pressure distribution until a preset iteration condition is met to obtain a numerical calculation result of the fluid flow.
And obtaining a pressure correction model by adopting a numerical simulation model according to the velocity distribution and the pressure distribution of the fluid. To improve accuracy, the numerical simulation model must exhibit the anisotropy of reynolds stress. Preferably, the Navier-Stokes (NS) equation can be solved, when the turbulent flow field is analyzed, a turbulent flow model can be used for solving an average flow field, a sub-lattice stress model can be used for solving a large-scale vortex, and a full-scale direct numerical solution can be also used. When the Navier-Stokes equation is solved, a Reynolds stress transport model and a dissipation rate model can be selected for sealing. Wherein an initial velocity profile and pressure profile can be assumed in advance.
And correcting the pressure and the speed of the fluid according to the pressure correction model. And calculating a discrete equation constant term in the numerical simulation model and further solving a pressure correction equation according to the assumed initial velocity distribution and pressure distribution so as to correct the velocity distribution and the pressure distribution, and further solving other discretization equations in the data simulation model according to the corrected velocity distribution and pressure distribution.
And repeating the calculation speed publication and the pressure distribution until a preset iteration condition is met to obtain a numerical calculation result of the fluid flow. And repeatedly correcting and calculating to continuously correct the velocity distribution and the pressure distribution in the fluid flow until a preset iteration condition is met to obtain a numerical calculation result of the fluid flow, wherein the numerical calculation result comprises flow state parameters such as flow velocities of fluids at different positions in the geometric model, and the fluid state in the sedimentation tube can be obtained through analysis according to the flow state parameters of each point in the fluid flow.
The systems, devices, modules or units illustrated in the above embodiments may be implemented by a computer chip or an entity, or by a product with certain functions. A typical implementation device is a computer device, which may be, for example, a personal computer, a laptop computer, a cellular telephone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.
In a typical example, the computer device specifically comprises a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the method performed by the client as described above when executing the program, or the processor implementing the method performed by the server as described above when executing the program.
Referring now to FIG. 15, shown is a schematic block diagram of a computer device 600 suitable for use in implementing embodiments of the present application.
As shown in fig. 15, the computer apparatus 600 includes a Central Processing Unit (CPU)601 which can perform various appropriate works and processes according to a program stored in a Read Only Memory (ROM)602 or a program loaded from a storage section 608 into a Random Access Memory (RAM)) 603. In the RAM603, various programs and data necessary for the operation of the system 600 are also stored. The CPU601, ROM602, and RAM603 are connected to each other via a bus 604. An input/output (I/O) interface 605 is also connected to bus 604.
The following components are connected to the I/O interface 605: an input portion 606 including a keyboard, a mouse, and the like; an output section 607 including a Cathode Ray Tube (CRT), a liquid crystal feedback (LCD), and the like, and a speaker and the like; a storage section 608 including a hard disk and the like; and a communication section 609 including a mesh interface card such as a LAN card, modem, or the like. The communication section 609 performs communication processing via a grid such as the internet. The driver 610 is also connected to the I/O interface 606 as needed. A removable medium 611 such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, or the like is mounted on the drive 610 as necessary, so that a computer program read out therefrom is mounted as necessary on the storage section 608.
In particular, according to an embodiment of the present invention, the processes described above with reference to the flowcharts may be implemented as computer software programs. For example, embodiments of the invention include a computer program product comprising a computer program tangibly embodied on a machine-readable medium, the computer program comprising program code for performing the method illustrated in the flow chart. In such an embodiment, the computer program may be downloaded and installed from the grid through the communication section 609, and/or installed from the removable medium 611.
Computer-readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), Digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device. As defined herein, a computer readable medium does not include a transitory computer readable medium such as a modulated data signal and a carrier wave.
For convenience of description, the above devices are described as being divided into various units by function, and are described separately. Of course, the functionality of the units may be implemented in one or more software and/or hardware when implementing the present application.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The application may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The application may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications grid. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the system embodiment, since it is substantially similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment.
The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims (8)

1. A method of analyzing a deposition tube field, comprising:
obtaining a geometric model of fluid in a deposition tube formed by a circular tube with a deposition layer, wherein the geometric model of the fluid is a horizontally arranged cylindrical body, the cross-sectional profile of the cylindrical body comprises an arc with an opening at the bottom end and horizontally arranged straight lines respectively connected with two ends of the opening, and the distance between the straight lines and the circle center of the arc is determined according to the thickness of the deposition layer;
defining and determining a Reynolds number of the fluid;
performing numerical calculation and flow field analysis on the geometric model according to the Reynolds number, wherein the flow field analysis comprises average flow field analysis and transient flow field analysis;
the Reynolds number Re is:
Figure FDA0002650774750000011
Figure FDA0002650774750000012
wherein, UbTo average velocity of flow, DHIs the hydraulic diameter of the section, A is the area of the section, l is the perimeter of the section, and v is the kinematic viscosity of the fluid.
2. The flow field analysis method of claim 1, wherein numerically calculating the geometric model according to the reynolds number specifically comprises:
meshing the geometric model of the fluid;
setting a geometric model after meshing according to the Reynolds number to obtain an analysis model;
and carrying out numerical calculation on the analysis model.
3. The flow field analysis method of claim 2, wherein meshing the geometric model of the fluid specifically comprises:
selecting at least one grid type;
dividing the geometric model into a plurality of areas or carrying out mesh division on the geometric model by solving an elliptic differential equation method;
and carrying out encryption processing on the grids of the boundary layer area.
4. The flow field analysis method according to claim 1, wherein the setting of the geometric model after meshing according to the reynolds number to obtain the analysis model specifically comprises:
determining a fluid flow state parameter of the fluid according to the section size and Reynolds number of the geometric model of the fluid;
and setting the fluid flow state parameters and the constraint conditions on the geometric model to obtain the analysis model.
5. The flow field analysis method according to claim 2, wherein setting constraints on the geometric model specifically comprises:
setting a boundary condition type;
arranging a fluid inlet, a fluid outlet and a flow direction of a fluid;
and setting a non-slip boundary condition.
6. A deposition tube field analysis system, comprising:
the geometric model unit is used for obtaining a geometric model of fluid in a deposition tube formed by a circular tube with a deposition layer, the geometric model of the fluid is a horizontally arranged cylindrical body, the cross section profile of the cylindrical body comprises a circular arc with an opening at the bottom end and horizontally arranged straight lines respectively connected with two ends of the opening, and the distance between the straight lines and the circle center of the circular arc is determined according to the thickness of the deposition layer;
a parameter determination unit for defining and determining the Reynolds number of the fluid;
the solving and analyzing unit is used for carrying out numerical calculation and flow field analysis on the geometric model according to the Reynolds number, and the flow field analysis comprises average flow field analysis and transient flow field analysis;
the Reynolds number Re is:
Figure FDA0002650774750000021
Figure FDA0002650774750000022
wherein, UbTo average velocity of flow, DHIs the hydraulic diameter of the section, A is the area of the section, l is the perimeter of the section, and v is the kinematic viscosity of the fluid.
7. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor,
the processor, when executing the program, implements the method of any of claims 1-5.
8. A computer-readable medium, having stored thereon a computer program,
the program when executed by a processor implementing the method according to any one of claims 1-5.
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