Flow velocity profile reconstruction method and system based on time reversal

Abstract

The invention provides a flow velocity profile reconstruction method and system based on time reversal. The method comprises the following steps: S1, establishing a hydrodynamic model comprising an inlet boundary and a target boundary based on actual topographic features; s2, determining an original target physical quantity at the target boundary, applying excitation opposite to the target physical quantity, and measuring a response physical quantity at the entrance boundary; s3, applying reverse excitation of the response physical quantity at the entrance boundary, and obtaining an optimized target physical quantity at the target boundary; and S4, verifying whether the optimization target physical quantity is consistent with the original physical quantity or not, and if so, responding to reverse excitation of the physical quantity, namely, reconstructing the entrance boundary physical quantity required for generating the original target physical quantity at the target position. According to the method, the fluid velocity field reconstructed based on the time reversal principle is highly matched with the actual flow field, and meanwhile the technology has high adaptability to different fluid environments and flow states.

Description

Technical Field

[0001] This invention relates to the field of flow field control technology, specifically to a method and system for reconstructing flow velocity profiles based on time inversion. Background Technology

[0002] Controllable flow velocity profiles, as a core technology for hydrodynamic environmental regulation, have systematic significance for ecological engineering and scientific research practices in multiple fields. In aquaculture, feed feeding is affected by water flow; precise control of flow velocity profiles can significantly improve the uniformity of feed distribution and feeding efficiency, reducing feed waste and water pollution caused by improper flow velocities. For the ecological construction of artificial reef areas, customizing three-dimensional flow velocity gradients based on the flow-tending characteristics of target species can accurately reproduce the hydrodynamic characteristics of their natural habitats, providing suitable living space for fish and thus promoting their habitat and reproduction. At the level of fundamental fluid mechanics research, the generation technology of high-precision programmable flow velocity profiles breaks through the spatiotemporal resolution limitations of traditional shear flow simulations, which is crucial for improving the reliability and repeatability of experimental data, and promotes the output and application of related scientific research results.

[0003] Currently, the technology for generating uniform velocity profiles in terrain-free environments is relatively mature. However, the actual ocean topography plays a significant role, and the coupling effect between fluid and structure alters fluid motion, causing the actual velocity profile to deviate from the theoretically preset value. Furthermore, when the target value is a non-uniform velocity profile, such as shear flow, the complex mechanism of fluid-structure interaction makes it difficult to achieve the expected outlet velocity through inlet boundary control. To improve the control accuracy of the velocity profile, multiple iterations of the inlet velocity are often used to indirectly correct the velocity profile at the target location during the control process. However, this method not only reduces efficiency but is also limited by the linearization assumption in the iterative correction method, resulting in limited improvement in velocity profile accuracy. Summary of the Invention

[0004] This invention provides a velocity profile reconstruction technology based on time inversion, overcoming the shortcomings of existing technologies. It utilizes the time reversibility of the wave equation to obtain the initial conditions or driving force distribution at the velocity inlet boundary by reverse propagating signals and physical field states, thereby achieving active control of fluid motion at the outlet and ultimately reconstructing the desired target velocity profile at a predetermined location.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A velocity profile reconstruction method based on time inversion includes the following steps: Step S1. Establish an entrance boundary based on actual terrain features. BD 1 and target boundary BD 2. Hydrodynamic model; Step S2. At the target boundary BD At two points, an excitation opposite to the original target physical quantity is applied at the inlet boundary. BD 1. Measure the physical quantity of the response; Step S3. At the entrance boundary BD Apply the reverse excitation of the response physical quantity at point 1, at the target boundary. BD Obtain the target physical quantity from two locations.

[0006] Step S4. Verify whether the optimized target physical quantity is consistent with the original physical quantity. If so, the reverse excitation of the response physical quantity is the inlet boundary physical quantity required to reconstruct and generate the original target physical quantity at the target location.

[0007] Furthermore, the physical quantity is a vector field quantity, the excitation is applied through boundary conditions, and the reconstruction process satisfies the principle of time reversal symmetry.

[0008] Furthermore, in step S2, the target boundary BD Excitation applied at 2 points = -target physical quantity; Step S3 Inlet boundary BD The excitation applied at point 1 = -target physical quantity.

[0009] Furthermore, the target physical quantity in step S1 includes the target flow velocity. V target This includes the vertical distribution and size of the velocity profile, and the target location where the target flow velocity occurs is... x target and the inlet location used to control fluid input. x source .

[0010] Further, step S2 specifically includes: Target profile flow velocity V The target is reversed in the propagation direction to obtain the first reverse velocity for the forward process. V FWI = - V targe ; with target boundary BD 2. Apply the first reverse velocity to the velocity inlet. V FWI Simulated fluid from the target boundary BD 2 Towards the entrance boundary BD 1. Spread at the entrance boundary BD The flow velocity was measured at one location and recorded as the first measured flow velocity. V FWM .

[0011] Furthermore, step S3 specifically includes: Measure flow velocity V FWM The propagation direction is reversed to obtain a second reversal velocity for the reverse process. V BWI = - V FWM ; By entrance boundary BD 1. Apply a second reverse velocity to the velocity inlet. V BWI Simulated fluid from the inlet boundary BD 1. Towards the target boundary BD 2. Propagation, at the target boundary BD Flow velocity was measured at two locations, and this measurement is recorded as the second flow velocity. V BWM .

[0012] Further, step S4 specifically includes: Verification of the second flow rate measurement V BWM Flow velocity relative to target profile V If the target is consistent, then the second reversal speed... V BWI That is, at the predetermined location x target Reconstructing the target velocity profile V target The required inlet boundary velocity.

[0013] Furthermore, the actual terrain features in step S1 include the shape of the coastline, the slope of the seabed, and the outline of obstacles or underwater mountains.

[0014] Furthermore, in step S1, the original target physical quantity is determined based on historical data, on-site measurement data, or theoretical models.

[0015] On the other hand, the present invention provides a velocity profile reconstruction system based on time inversion, comprising: The hydrodynamic model building module is used to determine the original target physical quantities and establish a model including the inlet boundary based on actual terrain features. BD 1 and target boundary BD 2. Hydrodynamic model; Forward processing module. It is used at the target boundary. BD At two points, an excitation opposite to the original target physical quantity is applied at the inlet boundary. BD 1. Measure the physical quantity of the response; Reverse processing module. It is used at the entry boundary. BD Apply the reverse excitation of the response physical quantity at point 1, at the target boundary. BD Obtain the target physical quantity from 2 locations; The verification module is used to verify whether the optimized target physical quantity is consistent with the original physical quantity. If so, the reverse excitation of the response physical quantity is the entry boundary physical quantity required to reconstruct and generate the original target physical quantity at the target location.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. Simple method. Time reversal technology can easily reconstruct the fluid velocity field without analyzing complex fluid-structure interaction processes, greatly simplifying the operation process and lowering the technical threshold.

[0017] 2. High reconstruction efficiency. Unlike traditional methods that involve multiple iterative corrections, this method only requires two forward and reverse calculations or experimental processes to quickly reconstruct the preset velocity profile at the target location. This provides strong support for real-time or near-real-time fluid dynamics analysis and meets the need for rapid flow field reconstruction.

[0018] 3. Reliable and accurate results. The fluid velocity field reconstructed based on the time-reversal principle is in high agreement with the actual flow field with small errors. At the same time, this technology has strong adaptability to different fluid environments and flow states, and can provide high-quality velocity field data for many engineering applications and scientific research that rely on accurate flow velocity data. This helps to improve the research accuracy and the safety and effectiveness of engineering practices in related fields. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a flowchart of the velocity profile reconstruction based on the time inversion method of the present invention; Figure 2 This is a schematic diagram of a geometric scene in which the present invention is applied; Figure 3 The target flow velocity magnitude and distribution of this invention; Figure 4 This refers to the velocity distribution in the forward process simulation of this invention. Figure 5 The velocity distribution in the reverse process simulation of this invention; Figure 6 The velocity was measured at position BD2 during the reverse process of this invention. V BWM relative to target speed V targetThe comparison chart. Detailed Implementation

[0021] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below. Example 1 like Figure 1 As shown, this invention provides a velocity profile reconstruction method based on time inversion, comprising the following steps: A. Determination of the preset velocity profile and establishment of the hydrodynamic model Step 1: Based on the velocity profile obtained from historical data, field measurement data, or theoretical models, determine the target current velocity required for the actual project in the target marine environment. V target This includes the vertical distribution and magnitude of the velocity profile. Simultaneously, the location where the target velocity occurs is defined. x target and the inlet location used to control fluid input. x source .

[0022] Based on key topographic features of the target marine environment, such as the shape of the coastline, the slope of the seabed, seabed obstacles (such as reefs, shipwrecks, etc.), the outline of underwater mountains, and the location of fluid inlets. x source and target location x target In a physics lab or numerical simulation tank, a model scenario is created that allows motion to propagate through water. The model includes the inlet location... x source The boundary at the location is denoted as BD1, and the target location is... x target The boundary at that point is denoted as BD2.

[0023] B. Forward Process Step 2: Target speed V target The propagation direction is reversed to obtain the reverse velocity used for the forward process. V FWI = - V target .

[0024] In numerical software or physical experiments, begin the simulation of the forward process, i.e., the fluid motion propagates from the BD2 boundary towards the BD1 boundary. Specifically, set BD2 as the velocity inlet boundary and select the reverse velocity as the boundary velocity. V FWI After running the test or numerical simulation, the flow velocity was measured at location BD1, and the measured flow velocity was recorded as follows: V FWM .

[0025] C. Reverse process Step 3: Measure the flow rate V FWM The propagation direction is reversed to obtain the reversal speed used for the reverse process. V BWI = - V FWM .

[0026] In numerical software or physical experiments, begin the simulation of the reverse process, i.e., the fluid motion propagates from the BD1 boundary towards the BD2 boundary. Specifically, set BD1 as the velocity inlet boundary and select the reverse velocity as the boundary velocity. V BWI After running the test or numerical simulation, the flow velocity was measured at location BD2, and the measured flow velocity was recorded as follows: V BWM .

[0027] D. Verification process Step 4: Ignoring experimental or numerical errors, measure the flow rate in the reverse process based on the time-reversal principle. V BWM Will be relative to the target speed V target Consistent. At the same time. V BWI That is, at the predetermined location x target Reconstructing the target velocity profile V target The required inlet boundary velocity.

[0028] This embodiment considers a small pond for aquaculture, such as... Figure 2 As shown, the pool is 1m deep. A water pump is installed at the boundary of the pool (BD1) to propel the water from right to left. Simultaneously, a terrain feature exists at the bottom of the pool at the boundary of BD1, consisting of a 0.3m horizontal section and a 0.2m sloping section, with a height of 0.1m. Feed is then introduced at a location 2m away from BD1. To ensure proper feed introduction, a shear flow with a bottom velocity of 0.2m / s and a top velocity of 0.5m / s is required at location BD2. xtarget Size and distribution as follows Figure 3 As shown.

[0029] To obtain the inlet velocity at BD1 that enables the flow velocity to reach the target value at BD2, the proposed method is implemented in the numerical model below. To reduce the computational load, the computational domain is... x The length in the direction is chosen as the distance from BD2 to BD1. The following is a simulation of the forward process, that is, first, according to the formula... V FWI = - V target The inversion value of the target flow velocity is calculated; then, this inversion value is used as a boundary parameter input to the BD2 boundary in the numerical model; subsequently, the water flow propagates from BD2 to BD1, and finally, the boundary velocity information is measured at the location of BD1. V FWM The simulated velocity field of the forward process is as follows: Figure 4 As shown.

[0030] Next, we will simulate the reverse process, which is... V FWM inverted value V BWI = - V FWM The boundary parameters are input to the BD1 boundary in the numerical model; then, the water flows to BD1 and propagates to BD2, and the boundary velocity information is measured at the BD2 location. V BWM The simulated velocity field of the reverse process is as follows: Figure 5 As shown. Measurement speed. V BWM relative to target speed V target For example Figure 6 As shown, the results demonstrate a high degree of fit between the two methods. This result strongly proves the feasibility of the time inversion method in fluid velocity field reconstruction, providing a reliable technical means for subsequent fluid dynamics research and engineering applications.

[0031] Example 2 This embodiment provides a velocity profile reconstruction system based on time inversion, including: The hydrodynamic model building module is used to determine the original target physical quantities and establish a model including the inlet boundary based on actual terrain features. BD 1 and target boundary BD 2. Hydrodynamic model; Forward processing module. It is used at the target boundary. BD At two points, an excitation opposite to the original target physical quantity is applied at the inlet boundary. BD 1. Measure the physical quantity of the response; Reverse processing module. It is used at the entry boundary. BD Apply the reverse excitation of the response physical quantity at point 1, at the target boundary. BD Obtain the target physical quantity from 2 locations; The verification module is used to verify whether the optimized target physical quantity is consistent with the original physical quantity. If so, the reverse excitation of the response physical quantity is the entry boundary physical quantity required to reconstruct and generate the original target physical quantity at the target location.

[0032] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

[0033] It should be understood that any parts not described in detail in this specification belong to the prior art.

[0034] It should be understood that the above description of the preferred embodiments is quite detailed, but it should not be considered as a limitation on the scope of protection of this invention. Those skilled in the art, under the guidance of this invention, can make substitutions or modifications without departing from the scope of protection of the claims of this invention, and all such substitutions or modifications fall within the scope of protection of this invention. The scope of protection of this invention should be determined by the appended claims.

Claims

1. A velocity profile reconstruction method based on time inversion, characterized in that, Includes the following steps: Step S1. Determine the original target physical quantities and establish an entry boundary based on the actual terrain features. BD 1 and target boundary BD 2. Hydrodynamic model; Step S2. At the target boundary BD Two excitations opposite to the target physical quantity are applied at the inlet boundary. BD 1. Measure the physical quantity of the response; Step S3. At the entrance boundary BD Apply the reverse excitation of the response physical quantity at point 1, at the target boundary. BD Obtain the target physical quantity from 2 locations; Step S4. Verify whether the optimized target physical quantity is consistent with the original physical quantity. If so, the reverse excitation of the response physical quantity is the inlet boundary physical quantity required to reconstruct and generate the original target physical quantity at the target location.

2. The velocity profile reconstruction method based on time inversion according to claim 1, characterized in that, The physical quantity is a vector field quantity, and the excitation is applied through boundary conditions. The reconstruction process satisfies the principle of time reversal symmetry.

3. The velocity profile reconstruction method based on time inversion according to claim 1, characterized in that, Target boundary in step S2 BD Excitation applied at 2 points = -target physical quantity; Step S3 Inlet boundary BD The excitation applied at point 1 = -target physical quantity.

4. The velocity profile reconstruction method based on time inversion according to claim 3, characterized in that, The target physical quantity in step S1 includes the target flow velocity. V target This includes the vertical distribution and size of the velocity profile, and the target location where the target flow velocity occurs is... x target and the inlet location used to control fluid input. x source .

5. The velocity profile reconstruction method based on time inversion according to claim 4, characterized in that, Step S2 specifically includes: Target profile flow velocity V The target is reversed in the propagation direction to obtain the first reverse velocity for the forward process. V FWI = - V targe ; with target boundary BD 2. Apply the first reverse velocity to the velocity inlet. V FWI Simulated fluid from the target boundary BD 2 Towards the entrance boundary BD 1. Spread at the entrance boundary BD The flow velocity was measured at one location and recorded as the first measured flow velocity. V FWM .

6. The velocity profile reconstruction method based on time inversion according to claim 5, characterized in that, Step S3 specifically includes: Measure flow velocity V FWM The propagation direction is reversed to obtain a second reversal velocity for the reverse process. V BWI =- V FWM ; By entrance boundary BD 1. Apply a second reverse velocity to the velocity inlet. V BWI Simulated fluid from the inlet boundary BD 1. Towards the target boundary BD 2. Propagation, at the target boundary BD Flow velocity was measured at two locations, and this measurement is recorded as the second flow velocity. V BWM .

7. The velocity profile reconstruction method based on time inversion according to claim 6, characterized in that, Step S4 specifically includes: Verification of the second flow rate measurement V BWM Flow velocity relative to target profile V If the target is consistent, then the second reversal speed... V BWI That is, at the predetermined location x target Reconstructing the target velocity profile V target The required inlet boundary velocity.

8. The velocity profile reconstruction method based on time inversion according to claim 1, characterized in that, The actual terrain features in step S1 include the shape of the coastline, the slope of the seabed, obstacles, or the outline of underwater mountains.

9. The velocity profile reconstruction method based on time inversion according to claim 1, characterized in that, In step S1, the original target physical quantity is determined based on historical data, on-site measurement data, or theoretical models.

10. A velocity profile reconstruction system based on time inversion, characterized in that, include: The hydrodynamic model building module is used to determine the original target physical quantities and establish a model including the inlet boundary based on actual terrain features. BD 1 and target boundary BD 2. Hydrodynamic model; Forward processing module. It is used at the target boundary. BD At two points, an excitation opposite to the original target physical quantity is applied at the inlet boundary. BD 1. Measure the physical quantity of the response; Reverse processing module. It is used at the entry boundary. BD Apply the reverse excitation of the response physical quantity at point 1, at the target boundary. BD Obtain the target physical quantity from 2 locations; Verification module. It is used to verify whether the optimized target physical quantity is consistent with the original physical quantity. If so, the reverse excitation of the response physical quantity is the inlet boundary physical quantity required to reconstruct and generate the original target physical quantity at the target location. The time-inversion-based velocity profile reconstruction system is used to perform the steps in the time-inversion-based velocity profile reconstruction method according to any one of claims 1-8.

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