Computational method for simulating pipe erosion process based on large eddy simulation

Abstract

The application provides a calculation method for pipeline erosion process simulation based on large eddy simulation, which comprises the following steps: S1, meshing a geometric piece by using ICEM software; S2, setting boundary conditions and particle parameters; S3, setting a fluid calculation format; S4, setting a particle erosion model; S5, calculating by using OpenFOAM software and post-processing by using Paraview software. The application adopts large eddy simulation, and simultaneously considers the calculation cost and accuracy, especially for a bent pipe, and can better capture the secondary flow phenomenon. Moreover, the calculation method can obtain the erosion condition in advance by using the simulation method, and the actual process can be adjusted accordingly, so that the experimental cost is greatly saved.

Description

Technical Field

[0001] This invention relates to the field of aero-engines, and in particular to a calculation method for simulating pipeline erosion processes based on large eddy simulation. Background Technology

[0002] In the field of aero-engines, with the increasing demand for high performance, high reliability, and lightweight precision components such as oil pipelines, there are also higher requirements for the smoothness of the pipeline inner wall. Two-phase flow (referring to the hybrid dynamics problem that considers the existence of two phases of matter simultaneously and has the ability to distinguish the contact surface between the two phases) polishing technology has become one of the important means of pipeline finishing, hence the urgent need for scientific, efficient, and accurate simulation prediction methods.

[0003] Traditional simulation prediction methods include direct numerical simulation (DNS) and the Reynolds-averaged method. Among these, DNS is a method in fluid mechanics for studying turbulence. It obtains accurate information about the turbulent field by directly solving the Navier-Stokes equations numerically, without the need to build a turbulence model. Theoretically, this method has the advantage of acquiring information at all scales of turbulence and is an effective means of studying turbulence mechanisms.

[0004] Here, turbulence refers to a fluid flow state where, when the flow velocity increases to a certain level, the streamlines of the fluid are no longer clearly distinguishable, many small vortices appear in the flow field, laminar flow is disrupted, and there is not only sliding but also mixing between adjacent flow layers, thus forming turbulence.

[0005] However, its implementation faces significant challenges and limitations. Since turbulence is an irregular flow at multiple scales, obtaining flow information at all scales requires extremely high spatial and temporal resolution, which results in large computational loads, long processing times, and strong dependence on computer memory.

[0006] Due to limitations in computational resources, DNS (Direct Numerical Simulation) currently struggles to predict complex turbulent motions, primarily being limited to simple turbulent motions with low Reynolds numbers, and its application in practical engineering is difficult. The high computational cost also restricts the application of DNS in practical engineering, leading it to be used more extensively in basic research.

[0007] The Reynolds-averaged method (RANS) is an important approach in fluid mechanics. Based on time-averaging theory, it treats unsteady turbulent motion as a mean flow field and a Reynolds stress field, thus greatly saving computational resources. This method, while preserving the large-scale flow characteristics, uses a modeling approach to calculate the Reynolds stress field, making it an effective means of solving engineering problems.

[0008] However, the RANS method also has some drawbacks. Turbulence models are based on a series of assumptions that may not apply to all situations, limiting the model's applicability and accuracy. In mean motion, the influence of turbulent fluctuations, i.e., Reynolds stress, is unknown and requires a turbulence model to describe, increasing the model's complexity and uncertainty. The Reynolds-averaged model lacks universality, meaning that different models or parameters may need to be adjusted for different flow conditions, increasing the difficulty and complexity of its application.

[0009] In view of this, the present invention provides a calculation method for simulating pipeline erosion process based on large eddy simulation, in order to overcome the above-mentioned technical problems. Summary of the Invention

[0010] The technical problem to be solved by this invention is to overcome the shortcomings of existing simulation prediction methods, which are difficult and complex to apply and lack universality, and to provide a calculation method for pipeline erosion process simulation based on large eddy simulation.

[0011] The present invention solves the above-mentioned technical problems through the following technical solution:

[0012] A calculation method for simulating pipeline erosion processes based on large eddy simulation is characterized by the following steps:

[0013] S1. Mesh the geometry using ICEM software;

[0014] S2. Set boundary conditions and particle parameters;

[0015] S3. Set the fluid calculation format;

[0016] S4. Set up the particle erosion model;

[0017] S5. Calculations are performed using OpenFOAM software, and post-processing is done using Paraview software.

[0018] According to an embodiment of the present invention, step S1 includes: meshing the geometry to be calculated and drawing the corresponding boundary layer according to the Reynolds number, wherein the boundary layer scale y+ is 1.

[0019] According to an embodiment of the present invention, step S2 includes: setting boundary conditions and particle parameters, wherein the pipe wall adopts a no-slip boundary condition, the particle-wall condition is Reflect, and the normal and tangential rebound coefficients are set based on the Grant model, and the expressions are as follows:

[0020]

[0021] Among them, e m ,et Here are the restitution coefficients for the normal and tangential directions, α is the impact angle, and u is the restitution coefficient. p,n with u′ p,n Let u be the normal velocity of the particle before and after the collision. p,t with u′ p,t The tangential velocity is the velocity of the particle before and after the impact.

[0022] According to an embodiment of the present invention, step S3 includes: large eddy simulation has a smaller calculation error for pipe fluid; in the WALE model, the eddy viscosity coefficient V... sgs Expressed as:

[0023]

[0024] Among them, C w This is a model constant, 0.325; S ij For strain rate tensor; Let x be the velocity gradient tensor; Δ be the Laplace operator; x i Represents the component of the spatial coordinate in the i-direction; x j This represents the component of the spatial coordinate in the j-direction; This represents the velocity component of the fluid in the i-direction; δ represents the velocity component of the fluid in the j-direction; ij It represents Kroneck δ.

[0025] According to an embodiment of the present invention, step S4 uses the Finnie erosion model for calculation, and its expression is:

[0026]

[0027] Among them, E Q This represents the volume eroded away (m). 3 );m p P is the particle mass; P is the yield stress of the material; α is the impact angle; ψ is a constant representing the ratio of contact depth to cutting depth; K is a constant representing the ratio of vertical to horizontal force components on the particle. Let f(θ) be the particle velocity, f(θ) be the impact angle function, and θ be the particle impact angle.

[0028] According to one embodiment of the present invention, in step S4, ψ and K are empirical coefficients with a value of 2.

[0029] According to one embodiment of the present invention, step S5 includes: comparing the obtained particle velocity result with the most accurate DNS result.

[0030] The positive and progressive effects of this invention are as follows:

[0031] The calculation method for simulating pipeline erosion processes based on large eddy simulation in this invention has the following advantages:

[0032] First, large eddy simulation balances computational cost and accuracy, especially for curved pipes, where it can better capture secondary flow phenomena.

[0033] Second, the erosion situation can be obtained in advance through simulation, which can be used to adjust the actual process and greatly save experimental costs. Attached Figure Description

[0034] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, in which the same reference numerals always denote the same features, wherein:

[0035] Figure 1 This is a schematic diagram of the geometric model in the calculation method of pipeline erosion process simulation based on large eddy simulation of the present invention.

[0036] Figure 2 This is a schematic diagram of mesh generation in the calculation method for pipeline erosion process simulation based on large eddy simulation of the present invention.

[0037] Figure 3 This is a schematic diagram comparing the results of LES and DNS in the calculation method for pipeline erosion process simulation based on large eddy simulation of this invention. Figure 1 .

[0038] Figure 4 This is a schematic diagram comparing the results of LES and DNS in the calculation method for pipeline erosion process simulation based on large eddy simulation of this invention. Figure 2 . Detailed Implementation

[0039] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0040] Embodiments of the invention will now be described in detail with reference to the accompanying drawings. Preferred embodiments of the invention will now be described in detail, examples of which are shown in the drawings. Wherever possible, the same reference numerals will be used in all the drawings to denote the same or similar parts.

[0041] Furthermore, although the terminology used in this invention is selected from commonly known and used terms, some terms mentioned in this specification may have been selected by the applicant in his or her judgment, and their detailed meanings are explained in the relevant sections of the description herein.

[0042] Furthermore, the invention should be understood not only through the actual terminology used, but also through the meaning implied by each term.

[0043] like Figure 1 and Figure 2 As shown, this invention discloses a calculation method for simulating pipeline erosion process based on large eddy simulation. Large eddy simulation is a numerical method used to simulate turbulent flow in fluid dynamics. Based on the multi-scale characteristics of turbulence, it directly solves the motion equations of large-scale eddies, while using a model to simulate the influence of small-scale eddies on large-scale eddies.

[0044] The calculation method for simulating pipeline erosion based on large eddy simulation includes the following steps:

[0045] Step S1: Mesh the geometry using ICEM software.

[0046] Preferably, step S1 includes: meshing the geometry to be calculated and drawing the corresponding boundary layer according to the Reynolds number, with the boundary layer scale y+ being 1.

[0047] Step S2: Set boundary conditions and particle parameters, such as velocity inlet conditions.

[0048] Preferably, step S2 includes: setting boundary conditions and particle parameters, for example, studying particle motion in a 90° bend.

[0049] This example is set up as follows: the inlet of the bend uses a velocity inlet boundary condition with a velocity of 0.585 m / s, and the outlet uses a pressure boundary condition to prevent backflow. The particulate phase is set to escape at both the inlet and outlet.

[0050] The pipe wall adopts a no-slip boundary condition, and the particle-wall condition is Reflect (representing elastic collision). The normal and tangential rebound coefficients are set based on the Grant model, and the expressions are as follows:

[0051]

[0052] Among them, e n ,e t Here are the restitution coefficients for the normal and tangential directions, α is the impact angle, and u is the restitution coefficient. p,n with u′ p,n Let u be the normal velocity of the particle before and after the collision. p,t with u′ p,t The tangential velocity is the velocity of the particle before and after the impact.

[0053] The specific parameters of the particles are shown in Table 1 below:

[0054]

[0055] Table 1: Specific parameters of the particles

[0056] Step S3: Set the fluid calculation format.

[0057] Preferably, step S3 includes: Large eddy simulation (WALE model) has a smaller calculation error for the pipe fluid; in the WALE model, the eddy viscosity coefficient V... sgs Expressed as:

[0058]

[0059] Among them, C w This is a model constant, 0.325; S ij For strain rate tensor; Let x be the velocity gradient tensor; Δ be the Laplace operator; x i Represents the component of the spatial coordinate in the i-direction; x j This represents the component of the spatial coordinate in the j-direction; This represents the velocity component of the fluid in the i-direction; This represents the velocity component of the fluid in the j-direction;

[0060] δ ij It represents Kroneck δ.

[0061] x k With x l Then, depending on the values ​​of k and 1, the values ​​are 1 and 2; when k (or l) = 2, it represents the component of the spatial coordinate in the j direction.

[0062] and Then, depending on the values ​​of k and 1, the values ​​are 1 and 2; when k (or l) = 2, it represents the velocity component of the fluid in the j direction.

[0063] δ ij For Kroneck δ, specifically: when i = j, δ ij =1; when i≠j, δ ij =0.

[0064] Step S4: Set up the particle erosion model.

[0065] Preferably, the Finnie erosion model is used for calculation in step S4, and its expression is:

[0066]

[0067] Among them, E Q This represents the volume eroded away (m). 3 );m p P is the particle mass; P is the yield stress of the material; α is the impact angle; ψ is a constant representing the ratio of contact depth to cutting depth; K is a constant representing the ratio of vertical to horizontal force components on the particle. Let f(θ) be the particle velocity, f(θ) be the impact angle function, and θ be the particle impact angle.

[0068] Specifically, in step S4, ψ and K are empirical coefficients, which are generally taken as 2.

[0069] Step S5: Perform calculations using OpenFOAM software and post-process using Paraview software.

[0070] Preferably, step S5 includes: comparing the obtained particle velocity results with the most accurate DNS (Direct Numerical Simulation) results.

[0071] like Figure 3 and Figure 4 As shown, the results of LES (Large Eddy Simulation) and DNS (Direct Numerical Simulation) are in very good agreement, with a maximum error of less than 2%.

[0072] However, DNS requires hundreds of millions of grid cells to achieve such accuracy, while LES only requires less than ten million grid cells. The results obtained are very close to those of DNS, and the amount of computation required is less than ten times that of DNS.

[0073] This invention presents a calculation method for pipeline erosion simulation based on large eddy simulation. For the first time, it combines two-phase flow erosion simulation with the WALE model in large eddy simulation, establishes a specific and feasible calculation process, and selects a better WALE model constant, set to 0.325. Under this constant, the accuracy of the flow field and particles is relatively good.

[0074] Meanwhile, the WALE model relates eddy viscosity to rotation rate, so for any surface, since the rotation rate tends to 0, the eddy viscosity also tends to 0, making this model easier to implement and more stable.

[0075] To balance computational cost and accuracy, this invention presents a computational method for simulating pipe erosion processes based on Large Eddy Simulation (LES), falling between Direct Numerical Simulation (DNS) and Reynolds-Averaged Flow (RANS). LES has the advantage of resolving large-scale turbulence, making it particularly suitable for situations with high separation and transitional flows. This method directly simulates large-scale turbulent motion while simultaneously using a subgrid model to simulate the influence of small-scale turbulent motion on large-scale turbulent motion, thus capturing large-scale effects and pseudo-order structures that RANS methods cannot capture. Compared to DNS, it significantly reduces computational cost. At the same time, compared to RANS, it significantly improves computational accuracy.

[0076] This invention presents a computational method for simulating pipeline erosion processes based on large eddy simulation (LES), addressing the simulation research problem of pipeline surface finishing technology. This invention uses LES to simulate turbulence in micro-pipelines, a method that effectively captures secondary flow phenomena in curved pipes while balancing computational complexity and accuracy.

[0077] In summary, the calculation method for pipeline erosion process simulation based on large eddy simulation of the present invention has the following advantages:

[0078] First, large eddy simulation balances computational cost and accuracy, especially for curved pipes, where it can better capture secondary flow phenomena.

[0079] Second, the erosion situation can be obtained in advance through simulation, which can be used to adjust the actual process and greatly save experimental costs.

[0080] For those skilled in the art, the above disclosure is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application and therefore remain within the spirit and scope of the exemplary embodiments of this application.

[0081] Furthermore, this application uses specific terms to describe embodiments of the application. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0082] Similarly, it should be noted that, in order to simplify the description of the embodiments disclosed in this application and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of the embodiments of this application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, this disclosure method does not imply that the subject matter of this application requires more features than those mentioned in the claims. In fact, the embodiments have fewer features than all the features of a single embodiment disclosed above. Some embodiments use numbers describing the number of components or attributes; it should be understood that such numbers used in the description of embodiments are modified in some examples by the terms "approximately," "about," or "generally."

[0083] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A calculation method for simulating pipeline erosion processes based on large eddy simulation, characterized in that, The calculation method includes the following steps: S1. Mesh the geometry using ICEM software; S2. Set boundary conditions and particle parameters; S3. Set the fluid calculation format; S4. Set up the particle erosion model; S5. Calculations are performed using OpenFOAM software, and post-processing is done using Paraview software.

2. The calculation method for simulating pipeline erosion process based on large eddy simulation as described in claim 1, characterized in that, Step S1 includes: meshing the geometry to be calculated and drawing the corresponding boundary layer according to the Reynolds number, with the boundary layer scale y+ being 1.

3. The calculation method for pipeline erosion process simulation based on large eddy simulation as described in claim 1, characterized in that, Step S2 includes: setting boundary conditions and particle parameters. The pipe wall adopts a no-slip boundary condition, the particle-wall condition is Reflect, and the normal and tangential rebound coefficients are set based on the Grant model, with the following expression: Among them, e n ,e t Here are the restitution coefficients for the normal and tangential directions, α is the impact angle, and u is the restitution coefficient. p,n with u′ p,n Let u be the normal velocity of the particle before and after the collision. p,t with u′ p,t The tangential velocity is the velocity of the particle before and after the impact.

4. The calculation method for pipeline erosion process simulation based on large eddy simulation as described in claim 2, characterized in that, Step S3 includes: Large eddy simulation has a smaller calculation error for pipe fluid; in the WALE model, the eddy viscosity coefficient V... sgs Expressed as: Among them, C w This is a model constant, 0.325; S ij For strain rate tensor; Let x be the velocity gradient tensor; Δ be the Laplace operator; x i Represents the component of the spatial coordinate in the i-direction; x j This represents the component of the spatial coordinate in the j-direction; This represents the velocity component of the fluid in the i-direction; δ represents the velocity component of the fluid in the j-direction; ij It represents Kroneck δ.

5. The calculation method for pipeline erosion process simulation based on large eddy simulation as described in claim 1, characterized in that, In step S4, the Finnie erosion model is used for calculation, and its expression is: Among them, E Q This represents the volume eroded away (m). 3 );m p P is the particle mass; P is the yield stress of the material; α is the impact angle; ψ is a constant representing the ratio of contact depth to cutting depth; K is a constant representing the ratio of vertical to horizontal force components on the particle. Let f(θ) be the particle velocity, f(θ) be the impact angle function, and θ be the particle impact angle.

6. The calculation method for pipeline erosion process simulation based on large eddy simulation as described in claim 1, characterized in that, In step S4, ψ and K are empirical coefficients with a value of 2.

7. The calculation method for pipeline erosion process simulation based on large eddy simulation as described in claim 1, characterized in that, Step S5 includes: comparing the obtained particle velocity result with the most accurate DNS result.

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