Natural gas transportation pipeline drag reduction structure, optimization method and system

Abstract

The invention discloses a natural gas transportation pipeline drag reduction structure, an optimization method and a system, and relates to the field of pipeline structures. The problems that groove drag reduction in the field of natural gas pipeline transportation aims at small-diameter pipelines, most grooves are in a traditional v shape, and the drag reduction effect is not remarkable enough are solved. The resistance reduction structure comprises a plurality of semicircular groove structures with alternate widths and widths; wherein the width of the wide groove is twice that of the narrow groove. The optimization method comprises the following steps: establishing a smooth pipeline and a model with a wide-narrow alternate semicircular groove on the wall surface; carrying out structured grid division on the smooth pipeline and the wall surface with the wide and narrow alternate semicircular grooves; numerical simulation is conducted through Fluent fluid simulation software, and a turbulent flow structure in the pipeline is obtained; and the drag reduction rate is calculated, and the final natural gas transportation pipeline drag reduction structure is determined according to the drag reduction rate. By reducing the resistance, the amount of conveyed gas can be increased under the same energy consumption, or the energy consumption is reduced under the condition of keeping the same flow, so that the overall conveying efficiency is improved.

Description

Technical Field

[0001] The invention relates to the field of pipeline structures, and in particular to a drag reduction structure for a natural gas transportation pipeline. Background Art

[0002] Take sharks as an example. The scales on their bodies are shaped like tiny grooves, which have been proven to have a drag reduction effect. Currently, micro-groove drag reduction technology has been applied to the surfaces of fast transportation vehicles such as aircraft and submarines, but it is rarely used in the field of pipeline transportation of natural gas. At the same time, most of the research on groove drag reduction is experimental, and its drag reduction mechanism has not yet been fully clarified.

[0003] Most of the early research on grooves was concentrated in the experimental field, such as the experiment of Walsh et al. at NASA Research Center on the downstream micro grooves in the shark skin structure: by adjusting the grooves of different forms and sizes, the best drag reduction effect was found. Neumann D et al. conducted experimental research on the rotating bodies with different groove structures in axial water flow. The research results showed that compared with smooth surfaces, the grooved structure can reduce drag by 9%, and even achieve 13% drag reduction effect in turbulent areas; Li Yubin et al. conducted experiments on the surface of aircraft models with drag reduction films in wind tunnels, and concluded that the flow ribs have a drag reduction effect of 5%-8%. Enyutin et al. conducted turbulent air flow experiments on grooves of different shapes in circular tubes, achieving a drag reduction effect of 5% to 6%.

[0004] In terms of numerical simulation, Choi et al. simulated the turbulent field on the rib surface with the help of DNS algorithm, calculated the turbulent statistics on the rib surface, and compared them with the statistics on the flat plate to explore the principle and mechanism of drag reduction; Xu C and his team used the RNG k-ε model to simulate the newly designed micro-groove structure and deeply analyzed the drag reduction principle of this structure; Tang Shaomeng found that the symmetrical V-groove gas pipeline has a drag reduction effect at different flow rates in the drag reduction study of gas pipelines, and the optimal drag reduction effect is 6.5%; Wang Weiqiang et al. used the RNG enhanced wall function model to simulate a 50mm diameter gas pipeline and obtained that when s + When =22, the V-shaped micro-groove has a drag reduction effect of 2.6%; Wang Jing et al. used the LES algorithm to calculate the small-diameter gas pipeline with traditional V-shaped micro-grooves and obtained a drag reduction effect of 14%.

[0005] At present, there are few experiments and numerical simulations on groove drag reduction in the field of pipeline natural gas transportation. Most numerical simulations are mainly aimed at small-diameter pipelines, where the groove shapes are mostly traditional V-shaped, and the drag reduction effect is not significant enough. Summary of the invention

[0006] Aiming at the problem that groove drag reduction in the field of pipeline natural gas transportation is aimed at small-diameter pipelines, and the groove shape is mostly traditional V-shaped, and the drag reduction effect is not significant enough, the present invention proposes a natural gas transportation pipeline drag reduction structure, the drag reduction structure comprising: a plurality of wide and narrow alternating semicircular groove structures; wherein the width of the wide groove is twice the width of the narrow groove.

[0007] Based on the same inventive concept, the present invention also proposes a method for optimizing the drag reduction structure of a natural gas transmission pipeline, the optimization method comprising:

[0008] Step 1: Establish a model of a smooth pipe and a wall with wide and narrow alternating semicircular grooves;

[0009] Step 2: Divide the smooth pipe and the wall with wide and narrow alternating semicircular grooves into structured grids;

[0010] Step 3: Perform numerical simulation using Fluent fluid simulation software to obtain the turbulent flow structure in the pipeline;

[0011] Step 4: Calculate the drag reduction rate, and determine the final drag reduction structure of the natural gas transportation pipeline according to the drag reduction rate.

[0012] Furthermore, a preferred method is proposed, wherein step 1 comprises:

[0013] Determine the model parameters of the wide and narrow semicircular grooves on the pipe and wall, including: pipe length, normal height, span angle, wide groove width and narrow groove width;

[0014] The wide groove is concave inwards in the form of a semicircle, and the narrow groove is also concave inwards in the form of a semicircle;

[0015] The grooves are arranged alternately, and each wide groove is followed by a narrow groove, forming a wide and narrow alternating structure.

[0016] Furthermore, a preferred embodiment is proposed, in which the pipe length is 100 mm, the normal height is 60 mm, the span direction is 24°, the width s1 of the wide groove is 0.54072 mm, and the width s2 of the narrow groove is 0.27036 mm.

[0017] Furthermore, a preferred method is proposed, wherein step 2 comprises:

[0018] Set 120 evenly distributed nodes in the flow direction;

[0019] Set 100 nodes in the normal direction;

[0020] The height of the first layer of grid is set to 3.3e-5m at the wall;

[0021] Nodes are added layer by layer from the first layer outwards.

[0022] Furthermore, a preferred method is proposed, wherein step 3 comprises:

[0023] Methane is selected as the fluid in the tube;

[0024] Set boundary conditions, including:

[0025] The inlet and outlet of the pipeline model are set to translation periodic conditions, the left and right sides are set to rotation periodic conditions, the upper side is set to symmetric boundary conditions, and the wall is set to static no-slip boundary conditions;

[0026] The Large Eddy Simulation model is used in combination with the Wall-Adapting Local Eddy Viscosity model to capture the turbulent structure;

[0027] SIMPLE algorithm is used for pressure coupling;

[0028] The gradient term is selected based on the least squares unit; the pressure term is selected as the second order; the momentum term is selected as the bounded central difference format;

[0029] The time term discretization format selects second-order implicit.

[0030] Furthermore, a preferred method is proposed, wherein step 4 comprises:

[0031] Collect the weighted average values ​​of flow velocity and wall shear stress at multiple planes in smooth pipes and pipes with groove structures;

[0032] The drag reduction rate η is calculated based on the plane streamwise velocity and the weighted average of the wall shear stress;

[0033]

[0034] Among them, F smooth is the friction resistance of the smooth wall, F groove is the friction resistance of the wide and narrow groove wall.

[0035] Based on the same inventive concept, the present invention also proposes a natural gas pipeline drag reduction structure optimization system, the optimization system comprising:

[0036] Model building unit, used to build models of smooth pipes and walls with wide and narrow alternating semicircular grooves;

[0037] Meshing unit, used to divide the structured mesh of smooth pipes and walls with wide and narrow alternating semicircular grooves;

[0038] The simulation unit is used to perform numerical simulation using Fluent fluid simulation software to obtain the turbulent flow structure in the pipeline;

[0039] The drag reduction rate calculation unit is used to calculate the drag reduction rate and determine the final drag reduction structure of the natural gas transportation pipeline according to the drag reduction rate.

[0040] Based on the same inventive concept, the present invention also proposes a computer device, including a memory and a processor, wherein the memory stores a computer program. When the processor runs the computer program stored in the memory, the processor executes a method for optimizing the drag reduction structure of a natural gas transmission pipeline according to any one of the above items.

[0041] Based on the same inventive concept, the present invention also proposes a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of a natural gas pipeline drag reduction structure optimization method as described in any one of the above are executed.

[0042] The present invention is beneficial in that:

[0043] A drag reduction structure for a natural gas transportation pipeline proposed in the present invention is composed of a plurality of wide grooves and narrow grooves arranged alternately, and the width of the wide grooves is twice that of the narrow grooves. This design can effectively change the flow characteristics of the fluid in the pipeline. The structure is composed of a plurality of wide grooves and narrow grooves arranged alternately, and the width of the wide grooves is twice that of the narrow grooves. This design can effectively change the flow characteristics of the fluid in the pipeline. The wide and narrow groove structure keeps the high disturbance area away from the pipeline wall and maintains a lower velocity disturbance near the groove wall. In this case, the turbulence near the wall can be weakened, the boundary layer can be kept stable, and the pulsation speed can be reduced. This is crucial to reducing flow resistance because an unstable boundary layer will lead to higher energy losses.

[0044] The drag reduction structure of a natural gas transportation pipeline proposed in the present invention has a significant drag reduction effect. Since the structure effectively suppresses the generation of vortices and reduces the turbulence intensity, it can significantly reduce the flow resistance of the gas in the pipeline and improve the transportation efficiency. And its drag reduction structure designed for small-diameter pipelines can effectively meet the special requirements for pipeline flow characteristics in natural gas transportation, especially under low flow conditions. Reducing resistance can increase the amount of gas transported under the same energy consumption, or reduce energy consumption while maintaining the same flow rate, thereby improving the overall transportation efficiency. By optimizing the flow state of the fluid in the pipeline, the unevenness in the flow can be reduced, the stability of the flow can be improved, and the service life of the pipeline and its ancillary equipment can be extended.

[0045] The drag reduction structure optimization method of a natural gas transportation pipeline proposed in the present invention can effectively reduce the turbulence intensity in the pipeline and reduce the flow resistance by establishing a model of a smooth pipeline and a semicircular groove with wide and narrow alternating grooves, thereby improving the transportation efficiency of natural gas. The numerical simulation using Fluent fluid simulation software can deeply analyze the turbulence structure and flow characteristics in the pipeline, provide accurate flow data, and facilitate the optimization design. By dividing the model into structured grids, the details of the fluid flow can be captured more accurately, the calculation accuracy can be improved, and the reliability of the simulation results can be guaranteed. Calculating the drag reduction rate can quantify the impact of different structural designs on flow resistance, help decision makers choose the optimal pipeline structure, and thus maximize economic benefits. The design of the semicircular groove with wide and narrow alternating grooves is flexible and can be adjusted according to different flow requirements and pipeline conditions, and has strong adaptability. This method combines the numerical simulation technology of modern fluid mechanics and promotes the innovation of natural gas transportation pipeline design. By improving the transportation efficiency and reducing energy consumption, the environmental impact during the natural gas transportation process is indirectly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic diagram of a drag reduction structure for a natural gas transportation pipeline according to Embodiment 1;

[0047] Figure 2 This is a schematic diagram of a single groove structure according to the fourth embodiment, wherein: Figure 2 (a) is a schematic diagram of a smooth pipe. Figure 2 (b) is a schematic diagram showing a wide and narrow alternating semicircular groove;

[0048] Figure 3 This is a schematic diagram of mesh division of the smooth wall model described in the fifth embodiment;

[0049] Figure 4 A schematic diagram of internal mesh division of the groove model according to the fifth embodiment;

[0050] Figure 5 Schematic diagram of the drag reduction rate in each working condition described in Implementation Mode 11;

[0051] Figure 6 This is a schematic diagram of the 10m / s average flow velocity distribution in the eleventh embodiment. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0053] Implementation method 1, see Figure 1The embodiment of the present invention is described as a drag reduction structure for a natural gas transportation pipeline, the drag reduction structure comprising: a plurality of wide and narrow alternating semicircular groove structures, wherein the width of the wide groove is twice the width of the narrow groove.

[0054] The drag reduction structure described in this embodiment is composed of a plurality of wide grooves and narrow grooves arranged alternately, and the width of the wide grooves is twice that of the narrow grooves. This design can effectively change the flow characteristics of the fluid in the pipeline. The structure is composed of a plurality of wide grooves and narrow grooves arranged alternately, and the width of the wide grooves is twice that of the narrow grooves. This design can effectively change the flow characteristics of the fluid in the pipeline. The wide and narrow groove structure keeps the high disturbance area away from the pipe wall and maintains a lower velocity disturbance near the groove wall. In this case, the turbulence near the wall can be weakened, the boundary layer can be kept stable, and the pulsation speed can be reduced. This is crucial to reducing flow resistance because an unstable boundary layer will lead to higher energy losses.

[0055] The drag reduction structure described in this embodiment has a significant drag reduction effect. Since the structure effectively suppresses the generation of eddies and reduces the turbulence intensity, it can significantly reduce the flow resistance of the gas in the pipeline and improve the transportation efficiency. And its drag reduction structure designed for small-diameter pipelines can effectively meet the special requirements for pipeline flow characteristics in natural gas transportation, especially under low flow conditions. Reducing resistance can increase the amount of gas transported under the same energy consumption, or reduce energy consumption while maintaining the same flow rate, thereby improving the overall transportation efficiency. By optimizing the flow state of the fluid in the pipeline, the unevenness in the flow can be reduced, the stability of the flow can be improved, and the service life of the pipeline and its ancillary equipment can be extended.

[0056] Furthermore, compared with the traditional drag reduction structure, the wide and narrow alternating groove design does not require a complex manufacturing process and is easy to promote and apply.

[0057] Embodiment 2: A method for optimizing a drag reduction structure of a natural gas transportation pipeline according to this embodiment, the optimization method comprises:

[0058] Step 1: Establish a model of a smooth pipe and a wall with wide and narrow alternating semicircular grooves;

[0059] Step 2: Divide the smooth pipe and the wall with wide and narrow alternating semicircular grooves into structured grids;

[0060] Step 3: Perform numerical simulation using Fluent fluid simulation software to obtain the turbulent flow structure in the pipeline;

[0061] Step 4: Calculate the drag reduction rate, and determine the final drag reduction structure of the natural gas transportation pipeline according to the drag reduction rate.

[0062] The drag reduction structure optimization method proposed in this embodiment can effectively reduce the turbulence intensity in the pipeline and reduce the flow resistance by establishing a model of a smooth pipeline and a semicircular groove with wide and narrow alternating grooves, thereby improving the transportation efficiency of natural gas. The numerical simulation using Fluent fluid simulation software can deeply analyze the turbulence structure and flow characteristics in the pipeline, provide accurate flow data, and facilitate the optimization design. By dividing the model into structured grids, the details of the fluid flow can be captured more accurately, the calculation accuracy can be improved, and the reliability of the simulation results can be ensured. Calculating the drag reduction rate can quantify the impact of different structural designs on flow resistance, helping decision makers to choose the optimal pipeline structure, thereby maximizing economic benefits. The design of the semicircular groove with wide and narrow alternating grooves is flexible and can be adjusted according to different flow requirements and pipeline conditions, and has strong adaptability. This method combines the numerical simulation technology of modern fluid mechanics, promotes the innovation of natural gas transportation pipeline design, and improves the overall technical level of the industry. By improving transportation efficiency and reducing energy consumption, the environmental impact of natural gas transportation is indirectly reduced, which is in line with the goal of sustainable development.

[0063] Embodiment 3: This embodiment further limits the method for optimizing the drag reduction structure of a natural gas transportation pipeline described in Embodiment 2, and the step 1 comprises:

[0064] Determine the model parameters of the wide and narrow semicircular grooves on the pipe and wall, including: pipe length, normal height, span angle, wide groove width and narrow groove width;

[0065] The wide groove is concave inwards in the form of a semicircle, and the narrow groove is also concave inwards in the form of a semicircle;

[0066] The grooves are arranged alternately, and each wide groove is followed by a narrow groove, forming a wide and narrow alternating structure.

[0067] In practical applications, Designmodeler software can be used to create models of smooth pipes and walls with alternating wide and narrow semicircular grooves.

[0068] In this embodiment, by setting wide and narrow semicircular grooves on the pipe wall, the turbulence of the fluid in the pipe can be effectively reduced and the flow resistance can be reduced. The design of the wide groove provides a larger flow channel, reduces the flow velocity, and reduces energy loss. The alternating arrangement of wide and narrow grooves can not only optimize the flow characteristics, but also improve the mechanical strength and stability of the pipeline. The shape design of the groove can effectively disperse the fluid pressure and reduce the risk of pipeline damage caused by pressure concentration. The wide and narrow structure makes the flow of the fluid in the pipeline more uniform, reducing dead corners and local retention. This helps to improve the gas delivery efficiency and ensure the uniform distribution of gas in the pipeline.

[0069] Implementation Method 4: Combination Figure 2 This embodiment further defines the method for optimizing the drag reduction structure of a natural gas transportation pipeline described in Embodiment 3, wherein the pipeline length is 100 mm, the normal height is 60 mm, the span is 24°, the width s1 of the wide groove is 0.54072 mm, and the width s2 of the narrow groove is 0.27036 mm.

[0070] The structure of smooth pipe is as follows Figure 2 As shown in (a), a circular tube with a diameter of 426 mm is used as the simulation object. In the actual modeling process, if the entire circular tube is drawn, the number of grid nodes is too large and the computing resources are consumed. Therefore, when using Designmodeler for modeling, the flow length is 100 mm, the normal height is 60 mm, and the span is 24°, that is, 1 / 15 arc is used to generate the local model of the circular tube. For the pipeline structure of wide and narrow alternating semicircular micro-grooves, the width s1 of the wide groove is 0.54072 mm, the width s2 of the narrow groove is 0.27036 mm, and the shape is as follows Figure 2 As shown in (b). Due to the large number of grooves and their small size, it is difficult to perform overall modeling and meshing. Therefore, we first draw a single wide and narrow alternating groove structure model, and then rotate the array to obtain a circular tube with longitudinal grooves all over the bottom.

[0071] Implementation Method 5: Combination Figure 3 and Figure 4 This embodiment further defines the method for optimizing the drag reduction structure of a natural gas transmission pipeline described in Embodiment 2, wherein step 2 includes:

[0072] Set 120 evenly distributed nodes in the flow direction;

[0073] Set 100 nodes in the normal direction;

[0074] The height of the first layer of grid is set to 3.3e-5m at the wall;

[0075] Nodes are added layer by layer from the first layer outwards.

[0076] In practical applications, Icem meshing software can be used to divide structured grids. To ensure the accuracy of data comparison, the flow direction of the smooth / groove model is uniformly set to 120 nodes, the number of normal grid nodes in the mainstream area is kept consistent at 100 nodes, and the height of the first layer of grid is 3.3e-5m from the wall.

[0077] In this embodiment, 120 evenly distributed nodes are set in the flow direction and 100 nodes are set in the normal direction, which can effectively capture the complex flow characteristics of the fluid in the pipeline, especially in the turbulent and boundary layer areas. This refined grid division ensures the high accuracy of the numerical simulation. At the same time, reasonable grid division helps to improve the stability of numerical calculations and reduce numerical errors. Especially in the fluid boundary layer area, the first layer of grid height is set to 3.3e-5m, which can effectively capture the interaction between the fluid and the pipeline wall and ensure the reliability of the simulation results.

[0078] The design of adding nodes layer by layer from the first layer outwards can achieve adaptive adjustment of the grid. This method can provide higher resolution in areas with large flow changes (such as near the grooves), and can reduce the amount of calculation and improve calculation efficiency in areas where the flow is relatively stable. The refined grid can better analyze the impact of wide and narrow alternating semicircular grooves on flow characteristics, capture the complex flow phenomena of the fluid inside the grooves and in their alternating areas, and help to further optimize the design. Although the grid density is high, a reasonable grid division method can reduce unnecessary calculations, improve the operating efficiency of the fluid simulation software, and thus speed up the optimization process.

[0079] Embodiment 6: This embodiment further limits the method for optimizing the drag reduction structure of a natural gas transportation pipeline described in Embodiment 2, and step 3 includes:

[0080] Methane is selected as the fluid in the tube;

[0081] Set boundary conditions, including:

[0082] The inlet and outlet of the pipeline model are set to translation periodic conditions, the left and right sides are set to rotation periodic conditions, the upper side is set to symmetric boundary conditions, and the wall is set to static no-slip boundary conditions;

[0083] The Large Eddy Simulation model (LES) is used in combination with the subgrid model Wall-Adapting Local Eddy Viscosity model to capture the turbulent structure.

[0084] The SIMPLE algorithm (semi-implicit algorithm for pressure coupling equations) is used for pressure coupling;

[0085] The gradient term (Gradient) is selected based on the least squares cell; the pressure term (Pressure) is selected as the second order; the momentum term (Momentum) is selected as the bounded central difference format Bounded Central Differencing;

[0086] For the time term discrete format (Trasient Formulation), select Second Order Implicit.

[0087] In this embodiment, methane is selected as the fluid in the pipe, which is in line with practical applications and can accurately reflect the flow characteristics in natural gas transportation. Combined with the Large Eddy Simulation (LES) model, large-scale turbulent structures can be effectively captured, thereby providing more realistic flow field information. Setting a variety of boundary conditions (such as translation periodicity, rotation periodicity and symmetric boundaries) ensures the comprehensiveness and accuracy of the simulation. The stationary no-slip wall condition simulates the physical properties of the real pipeline and enhances the calculation accuracy of the boundary layer. Combined with the Wall-Adapting Local Eddy Viscosity model, it can dynamically adapt to changes in the flow field and accurately capture the characteristics of turbulence. This method can effectively improve the understanding of complex phenomena such as flow separation and reattachment, and help optimize the design. The SIMPLE algorithm is used for pressure coupling to ensure good coupling between fluid momentum and pressure, improve the stability and convergence of numerical simulation, and reduce the numerical instability problems that may occur during the calculation process. In the discretization process of gradient, pressure and momentum terms, selecting an appropriate format (such as least squares unit, second order and bounded central difference format) can significantly improve the accuracy and reliability of the calculation. The second-order implicit time-term discretization format further enhances the stability of the simulation, especially when dealing with complex flows. Through high-precision turbulence simulation, the flow characteristics and turbulence structure in the pipeline can be intuitively observed. This provides important data support for subsequent performance evaluation and optimization design, and helps to understand the impact of design changes on flow characteristics. The simulation framework can be adjusted according to actual needs, such as modifying the fluid type, boundary conditions or turbulence model, which enhances the flexibility and applicability of the method.

[0088] Embodiment 7: This embodiment further limits the method for optimizing the drag reduction structure of a natural gas transportation pipeline described in Embodiment 2, and step 4 includes:

[0089] Collect the weighted average values ​​of flow velocity and wall shear stress at multiple planes in smooth pipes and pipes with groove structures;

[0090] The drag reduction rate η is calculated based on the plane streamwise velocity and the weighted average of the wall shear stress;

[0091]

[0092] Among them, F smooth is the friction resistance of the smooth wall, F groove is the friction resistance of the wide and narrow groove wall.

[0093] Embodiment 8: A natural gas pipeline drag reduction structure optimization system according to this embodiment, the optimization system comprises:

[0094] Model building unit, used to build models of smooth pipes and walls with wide and narrow alternating semicircular grooves;

[0095] Meshing unit, used to divide the structured mesh of smooth pipes and walls with wide and narrow alternating semicircular grooves;

[0096] The simulation unit is used to perform numerical simulation using Fluent fluid simulation software to obtain the turbulent flow structure in the pipeline;

[0097] The drag reduction rate calculation unit is used to calculate the drag reduction rate and determine the final drag reduction structure of the natural gas transportation pipeline according to the drag reduction rate.

[0098] Embodiment 9. A computer device described in this embodiment includes a memory and a processor, wherein the memory stores a computer program. When the processor runs the computer program stored in the memory, the processor executes a method for optimizing the drag reduction structure of a natural gas transmission pipeline described in any one of embodiments 1 to 7.

[0099] Embodiment 10. A computer-readable storage medium described in this embodiment stores a computer program, and when the computer program is executed by a processor, the steps of a method for optimizing the drag reduction structure of a natural gas transmission pipeline as described in any one of embodiments 1 to 7 are executed.

[0100] Implementation Method XI: Combination Figure 5 and Figure 6 This embodiment provides a specific example of the method for optimizing the drag reduction structure of a natural gas transportation pipeline described in Embodiment 2, and is used to verify the effect of a drag reduction structure of a natural gas transportation pipeline, specifically:

[0101] In this embodiment, fluent is used for numerical simulation. Large eddy simulation (LES) is performed on a smooth wall pipe and a pipe with wide and narrow grooves. By monitoring the weighted average of the flow velocity and the wall shear stress, the resistance of the two pipe walls is calculated and compared. The results are shown in the following table, where Re is the Reynolds number, τ w is the wall shear stress, S 底 is the wall area, F is the resistance, η is the drag reduction rate, and the calculation formula is (If η is positive, the resistance is reduced, otherwise it is increased).

[0102] Table 1 Comparison of drag reduction effects between smooth and groove

[0103]

[0104] Continued

[0105]

[0106] From the comparison results in Table 1, it can be seen that the groove structure has a flow velocity of 5m / s-20m / s (Re = 1.30×10 5 ~5.20×10 5 ) shows drag reduction, and at Re = 3.30 × 10 5 When the speed is 25m / s, the drag reduction effect reaches a maximum value of 15.96%; however, when the incoming flow velocity is 25m / s, the drag increases. The overall drag reduction rate changes with speed as shown in the figure below: Figure 5 As shown in the figure, it can be seen that it has an excellent drag reduction effect. The average velocity distribution in the 10m / s flow direction is as follows Figure 6 As shown, where y + is the dimensionless height of the wall, u + is the dimensionless velocity. It can be seen that the results calculated by LES are in good agreement with the previous experimental data (dashed line), which proves the accuracy of the LES calculation results. At the same time, when the incoming flow velocity is 10 m / s, the theoretical value of the shear stress on the smooth pipe wall is 0.11698 (Pa), and the LES simulation value is 0.11721 (Pa), with an error of 0.196%, which is within an acceptable range.

[0107] Those skilled in the art will appreciate that the embodiments of the present disclosure may be provided as methods, systems or computer program products. Therefore, the present disclosure may take the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware. Moreover, the present disclosure may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0108] The present disclosure is described with reference to flowcharts and / or block diagrams of methods, devices (systems) and computer program products according to embodiments of the present disclosure. It should be understood that each process and / or block in the flowchart and / or block diagram and the combination of processes and / or blocks in the flowchart and / or block diagram can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including an instruction device, which implements the functions specified in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0109] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure rather than to limit its protection scope. Although the present disclosure has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading the present disclosure, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the invention, but these changes, modifications or equivalent substitutions are all within the protection scope of the disclosed claims to be approved.

Claims

1. A drag reduction structure for a natural gas transportation pipeline, characterized in that: The drag reduction structure comprises: a plurality of wide and narrow alternating semicircular groove structures; wherein the width of the wide groove is twice the width of the narrow groove.

2. A method for optimizing the drag reduction structure of a natural gas transmission pipeline, characterized in that: The optimization method comprises: Step 1: Establish a model of a smooth pipe and a wall with wide and narrow alternating semicircular grooves; Step 2: Divide the smooth pipe and the wall with wide and narrow alternating semicircular grooves into structured grids; Step 3: Perform numerical simulation using Fluent fluid simulation software to obtain the turbulent flow structure in the pipeline; Step 4: Calculate the drag reduction rate, and determine the final drag reduction structure of the natural gas transportation pipeline according to the drag reduction rate.

3. A natural gas pipeline drag reduction structure optimization method according to claim 2, characterized in that: The step 1 comprises: Determine the model parameters of the wide and narrow semicircular grooves on the pipe and wall, including: pipe length, normal height, span angle, wide groove width and narrow groove width; The wide groove is concave inwards in the form of a semicircle, and the narrow groove is also concave inwards in the form of a semicircle; The grooves are arranged alternately, and each wide groove is followed by a narrow groove, forming a wide and narrow alternating structure.

4. A method for optimizing drag reduction structure of a natural gas transportation pipeline according to claim 3, characterized in that: The length of the pipe is 100 mm, the normal height is 60 mm, the span direction is 24°, the width s1 of the wide groove is 0.54072 mm, and the width s2 of the narrow groove is 0.27036 mm.

5. A natural gas transportation pipeline drag reduction structure optimization method according to claim 2, characterized in that: The step 2 comprises: Set 120 evenly distributed nodes in the flow direction; Set 100 nodes in the normal direction; The height of the first layer of grid is set to 3.3e-5m at the wall; Nodes are added layer by layer from the first layer outwards.

6. A natural gas pipeline drag reduction structure optimization method according to claim 2, characterized in that: The step 3 comprises: Methane is selected as the fluid in the tube; Set boundary conditions, including: The inlet and outlet of the pipeline model are set to translation periodic conditions, the left and right sides are set to rotation periodic conditions, the upper side is set to symmetric boundary conditions, and the wall is set to static no-slip boundary conditions; The Large Eddy Simulation model is used in combination with the Wall-Adapting Local Eddy Viscosity model to capture the turbulent structure; SIMPLE algorithm is used for pressure coupling; The gradient term is selected based on the least squares unit; the pressure term is selected as the second order; the momentum term is selected as the bounded central difference format; The time term discretization format selects second-order implicit.

7. A natural gas transportation pipeline drag reduction structure optimization method according to claim 2, characterized in that: The step 4 comprises: Collect the weighted average values ​​of flow velocity and wall shear stress at multiple planes in smooth pipes and pipes with groove structures; The drag reduction rate η is calculated based on the plane streamwise velocity and the weighted average of the wall shear stress; Among them, F smooth is the friction resistance of the smooth wall, F groove is the friction resistance of the wide and narrow groove wall.

8. A natural gas pipeline drag reduction structure optimization system, characterized in that: The optimization system comprises: Model building unit, used to build models of smooth pipes and walls with wide and narrow alternating semicircular grooves; Meshing unit, used to divide the structured mesh of smooth pipes and walls with wide and narrow alternating semicircular grooves; The simulation unit is used to perform numerical simulation using Fluent fluid simulation software to obtain the turbulent flow structure in the pipeline; The drag reduction rate calculation unit is used to calculate the drag reduction rate and determine the final drag reduction structure of the natural gas transportation pipeline according to the drag reduction rate.

9. A computer device, characterized in that: It comprises a memory and a processor, wherein the memory stores a computer program, and when the processor runs the computer program stored in the memory, the processor executes a method for optimizing a drag reduction structure of a natural gas transmission pipeline according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, which, when executed by a processor, executes the steps of a method for optimizing a drag reduction structure of a natural gas transmission pipeline as claimed in any one of claims 1 to 7.

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