Liquid shaking dynamics model verification method for surface tension storage tank in microgravity environment

Abstract

The invention relates to a liquid shake dynamic model verification method for a surface tension storage tank in a microgravity environment, which belongs to the field of aerospace engineering experiments and comprises the following steps: step 1, establishing a liquid shake proxy model of the surface tension storage tank in the microgravity environment, and performing liquid shake prediction; simulating a liquid shaking experiment by using a CFD modeling simulation tool and obtaining simulation data; 2, establishing an experimental device capable of simulating the liquid shaking dynamic characteristics of the surface tension storage tank; a liquid filling storage box module is arranged in the experimental device; step 3, carrying the experimental device on a freight spaceship; 4, after the freight spaceship is launched into an orbit, the experimental device collects and forms in-orbit experimental data; and 5, carrying out calibration and correction by using on-orbit experiment data.

Description

Technical Field

[0001] This invention relates to a method for verifying the dynamics of liquid sloshing in a surface tension tank under microgravity conditions, belonging to the field of aerospace engineering experiments. Background Technology

[0002] In microgravity environments, surface tension tanks subjected to irregular linear or angular accelerations may experience liquid sloshing, generating large disturbance forces and torques that affect the stability of attitude and trajectory control. Because existing surrogate models for liquid sloshing in surface tension tanks under microgravity are still incomplete, their accuracy and reliability require verification with experimental data. Experiments under terrestrial gravity conditions are insufficient to simulate the liquid sloshing characteristics of surface tension tanks in microgravity. In microgravity, liquid motion is highly unpredictable, often existing in a subequilibrium state with no frequency characteristics; even minor external stimuli can induce complex and extensive morphological changes. Therefore, on-orbit experimental verification of the model is necessary.

[0003] Existing in-orbit microgravity experiments on liquid sloshing are all conducted in non-surface tension tanks. Surface tension tanks differ significantly from traditional diaphragm and diaphragm-type tanks in that they lack anti-sloshing baffles. Therefore, even small external stimuli can induce large liquid sloshing. Under large-amplitude sloshing, the free liquid surface exhibits complex harmonic motions. Furthermore, the lateral motion of the tank no longer generates only lateral planar motion of the liquid; it also produces out-of-plane modal motions coupled with the lateral motion. This leads to single-period rotational motion, multi-period rotational motion, pseudo-periodic motion, and chaotic motion, accompanied by various bifurcation behaviors and even complex phenomena such as liquid surface separation. Further, by superimposing capillary forces on the liquid motion, even more complex nonlinear liquid motions can be observed. Therefore, establishing and validating liquid sloshing models in surface tension tanks under microgravity is far more complex than establishing and validating models in non-surface tension tanks. Summary of the Invention

[0004] The technical problem to be solved by this invention is to overcome the shortcomings of existing technologies that can only verify mathematical models and cannot obtain general modeling and simulation tools, in order to verify the model and obtain general modeling tools in a single on-orbit experiment.

[0005] The objective of this invention is achieved through the following technical solutions: A method for verifying the liquid sloshing dynamics of a surface tension tank under microgravity conditions includes: Step 1: Establish a proxy model for liquid sloshing in a surface tension tank under microgravity conditions and predict liquid sloshing; use CFD modeling and simulation tools to simulate the liquid sloshing experiment and obtain simulation data; Step 2: Establish an experimental setup to simulate the dynamic characteristics of liquid sloshing in a surface tension tank. The setup includes a liquid-filled tank module and a camera to record the evolution of liquid sloshing in the tank module. An accelerometer and an attitude gyroscope are also included to measure the liquid sloshing excitation and response data.

[0006] Step 3: Mount the experimental device on the cargo spacecraft; Step 4: After the cargo spacecraft is launched into orbit, before the remote rendezvous and docking guidance begins, the experimental device is activated. During the rendezvous and docking process between the cargo spacecraft and the space station, the acceleration caused by the attitude control and orbit control engines excites the liquid sloshing of the liquid-filled tank module. The experimental device collects external excitation acceleration and angular acceleration of the liquid-filled tank module sloshing, liquid sloshing force and torque of the liquid-filled tank module, and image data of the morphological changes of the liquid in the liquid-filled tank module, forming on-orbit experimental data. Step 5: Use on-orbit experimental data for calibration and correction.

[0007] The CFD modeling and simulation tool was modified based on on-orbit experimental data to obtain the modified CFD modeling and simulation tool. Simulation data for off-orbit experimental conditions is generated using the modified CFD modeling and simulation tools. Based on the on-orbit experimental data and the simulation data for off-orbit experimental conditions, the current liquid sloshing proxy model is adopted if the error does not exceed the limit when compared with the predicted data of the liquid sloshing proxy model. If the error exceeds the limit, the liquid sloshing proxy model is modified to obtain the modified liquid sloshing proxy model.

[0008] Compared with the prior art, the present invention has the following advantages: (1) This invention proposes an on-orbit experimental verification method for a surface tension tank liquid sloshing model; (2) The present invention is based on the rendezvous and docking process of cargo spacecraft, which can realistically simulate the external acceleration excitation of actual spacecraft, ensuring the authenticity of on-orbit experimental data and the accuracy of the model; (3) This invention can not only verify the mathematical model of liquid sloshing dynamics in surface tension tanks under microgravity, but also obtain a general CFD simulation tool during the verification process. The CFD simulation tool can be used for image simulation of the evolution process of liquid sloshing under microgravity.

[0009] (4) This invention is based on the liquid sloshing characteristics of surface tension tanks under microgravity environment revealed by CFD simulation tools, which promotes the development of liquid sloshing modeling theory. Attached Figure Description

[0010] Figure 1 This is a diagram of the system composition of the liquid sloshing experiment apparatus.

[0011] Figure 2 This is a test procedure for the dynamics of liquid sloshing in a surface tension tank under microgravity conditions. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0013] A method for verifying the liquid sloshing dynamics of a surface tension tank under microgravity conditions, such as... Figure 2 As shown, it includes: Step 1: Establish a proxy model for liquid sloshing in a surface tension tank under microgravity conditions and predict liquid sloshing; use CFD modeling and simulation tools to simulate the liquid sloshing experiment and obtain simulation data; Step 2: Establish an experimental setup to simulate the dynamic characteristics of liquid sloshing in a surface tension tank; the experimental setup includes a liquid-filled tank module; Step 3: Mount the experimental device on the cargo spacecraft; Step 4: The experimental device is launched into orbit with the cargo spacecraft; before the cargo spacecraft begins remote rendezvous and docking guidance with the space station, the experimental device is turned on and put into operation; the external excitation linear acceleration and angular acceleration, sloshing force and torque, and images of the morphological changes of the liquid in the liquid-filled tank module during the rendezvous and docking process are collected and stored to form on-orbit experimental data. Step 5: Use on-orbit experimental data for calibration and correction.

[0014] The CFD modeling and simulation tool was modified based on on-orbit experimental data to obtain the modified CFD modeling and simulation tool. Simulation data for off-orbit experimental conditions is generated using the modified CFD modeling and simulation tools. Based on the on-orbit experimental data and the simulation data for off-orbit experimental conditions, the current liquid sloshing proxy model is adopted if the error does not exceed the limit when compared with the predicted data of the liquid sloshing proxy model. If the error exceeds the limit, the liquid sloshing proxy model is modified to obtain the modified liquid sloshing proxy model.

[0015] The modifications to the CFD modeling and simulation tools include: (1) Initial modeling of CFD modeling and simulation Geometric modeling: A 1:1 three-dimensional model was built based on the dimensions of the liquid-filled tank module, the fluid domain was extracted and a structured mesh was generated.

[0016] (2) CFD modeling and simulation parameter settings Fluid properties: Set density, viscosity, and surface tension coefficient (e.g., σ=0.072N / m) according to the actual working fluid (water).

[0017] Boundary conditions: The wall uses a no-slip boundary to track the gas-liquid interface, with an adaptive time step.

[0018] (3) CFD modeling and simulation correction Data-driven calibration: The liquid surface profile (such as wave crest position and breakage morphology) captured by the on-orbit experimental data is compared with the CFD simulation data. The parameters of the geometric modeling in step (1) are iteratively optimized, including surface tension model parameters, turbulence model parameters, and mesh adaptive strategy, so that the error range does not exceed the limit. The error range limit refers to: the peak error of the sloshing force (target ≤5%) and the phase delay (≤10ms).

[0019] The liquid sloshing proxy model correction includes: (1) Extraction of on-orbit experimental data The mass fraction involved in the sloshing (fem): This is calculated by inversely using the ratio of the sloshing force amplitude to the total liquid mass, and then optimized using the frequency response curve.

[0020] Friction coefficient (f): The damping characteristics are fitted using the torque decay curve.

[0021] The dynamic parameter of the pulsating sphere radius (r_max) is calculated based on the centroid displacement trajectory and the geometric relationship between the liquid-filled tank module.

[0022] (2) CFD simulation data extraction Flow field image feature extraction: The liquid velocity field distribution, pressure field distribution, and centroid trajectory are extracted from the simulation data of off-orbit experimental conditions generated by the corrected CFD modeling and simulation tool.

[0023] (3) Correction of liquid sloshing proxy model Based on the extracted on-orbit experimental data and CFD simulation data, the dynamic equations of the liquid sloshing surrogate model are substituted into the model parameters to correct the liquid sloshing surrogate model.

[0024] The model parameters are solved using an optimization algorithm (particle swarm optimization for example), with the objective function being to minimize the root mean square error of the swaying force / torque.

[0025] Liquid sloshing test apparatus, such as Figure 1 As shown, it includes: a) Liquid-filled storage tank module The liquid-filled tank module is a crucial part of the experimental setup. It comprises a transparent, simulated tank scaled proportionally to the actual tank's length, width, and height. The simulated tank is filled with deionized water to simulate propellant, and its filling ratio matches that of the actual tank. Furthermore, based on the principle of similarity, it has been demonstrated that the liquid-filled tank module and the actual tank exhibit similar liquid sloshing characteristics. To ensure clear images of the liquid surface sloshing are captured, the water in the transparent liquid-filled tank module is stained.

[0026] b) Camera module The camera module is responsible for acquiring images of the liquid surface distribution and morphological changes in the liquid-filled tank module, collecting video information of the real-time sloshing of the liquid inside the tank module, and providing visual data support. The experimental setup uses four cameras (i.e., the camera module) to capture 360° images of the liquid surface in the liquid-filled tank module.

[0027] c) Lighting module To ensure the camera module can capture stable and clear images in real time, a stable and controlled light source is essential, providing a uniform lighting environment. The lighting module of this experimental setup employs two sets of side-emitting lamps with light guide plates to provide a stable lighting environment.

[0028] d) Dark Box Module The purpose of the dark box is to provide a stable and controlled light environment for experiments. As the outermost layer of the experimental setup in contact with the outside world, the dark box must be airtight to ensure safety. The dark box module is hexahedral, with all six sides detachable for easy access to the internal hardware. The six sides are connected by interlocking fasteners and sealed with rubber rings.

[0029] e) Vibration measurement and acquisition unit The vibration measurement and acquisition unit primarily measures and acquires the mechanical and kinematic characteristics of the liquid sloshing and transmits this data to the storage and control unit. The unit uses accelerometers and angular velocity sensors to measure the motion parameters of the experimental setup, and a six-dimensional force sensor to acquire force and torque information for the six degrees of freedom of the liquid-filled tank module, measuring the total force and torque exerted by the liquid on the module in real time. Before launch, the accelerometer, angular velocity sensor, and six-dimensional force sensor are calibrated and adjusted.

[0030] f) Storage control unit The storage control unit contains a solid-state drive for storing images and experimental data measured by the camera module and vibration measurement acquisition unit.

[0031] The contents not described in detail in this specification are common knowledge to those skilled in the art.

[0032] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for verifying the dynamics of liquid sloshing in a surface tension tank under microgravity conditions, characterized in that, include: Step 1: Establish a proxy model for liquid sloshing in a surface tension tank under microgravity conditions and predict liquid sloshing. The liquid sloshing experiment was simulated using CFD modeling and simulation tools, and simulation data was obtained. Step 2: Establish an experimental setup to simulate the dynamic characteristics of liquid sloshing in a surface tension tank; the experimental setup includes a liquid-filled tank module; Step 3: Mount the experimental device on the cargo spacecraft; Step 4: After the cargo spacecraft is launched into orbit, the experimental device collects external excitation acceleration and angular acceleration of the liquid tank module, liquid sloshing force and torque of the liquid tank module, and image data of the morphological changes of the liquid in the liquid tank module, forming on-orbit experimental data. Step 5: Based on the on-orbit experimental data, the CFD modeling and simulation tool is modified to obtain the modified CFD modeling and simulation tool; Simulation data for off-orbit experimental conditions were generated using the modified CFD modeling and simulation tools. Based on on-orbit experimental data and simulation data from off-orbit experimental conditions, and compared with the predicted data of the liquid sloshing proxy model, if the error does not exceed the limit, the current liquid sloshing proxy model is adopted; if the error exceeds the limit, the liquid sloshing proxy model is modified to obtain the modified liquid sloshing proxy model.

2. The liquid sloshing dynamics verification method according to claim 1, characterized in that, The experimental setup is equipped with a camera to record the evolution of liquid sloshing in the liquid-filled tank module, and also with an accelerometer and attitude gyroscope to measure the liquid sloshing excitation and sloshing response data.

3. The liquid sloshing dynamics verification method according to claim 1, characterized in that, The modifications to the CFD modeling and simulation tools include: (1) Initial geometric modeling of CFD modeling and simulation: A 1:1 three-dimensional model is established based on the size of the liquid-filled tank module, the fluid domain is extracted and a structured mesh is generated; (2) CFD modeling and simulation parameter settings: Fluid properties: Set density, viscosity, and surface tension coefficient according to the actual working fluid; Boundary conditions: The wall surface uses a no-slip boundary to track the gas-liquid interface, with an adaptive time step; (3) CFD modeling and simulation correction Data-driven calibration: The liquid surface profile captured by the on-orbit experimental data is compared with the CFD simulation data. The parameters of the geometric modeling in step (1) are optimized iteratively, including the surface tension model parameters, turbulence model parameters, and mesh adaptive strategy, so that the error range does not exceed the limit.

4. The liquid sloshing dynamics verification method according to claim 3, characterized in that, Water was used as the actual working fluid.

5. The liquid sloshing dynamics verification method according to claim 3, characterized in that, The liquid surface profile captured by the on-orbit experimental data includes the position of the wave crest and the shape of the breakage.

6. The liquid sloshing dynamics verification method according to claim 3, characterized in that, The error range limit refers to: peak error of the comparative swaying force ≤5%, phase delay ≤10ms.

7. The liquid sloshing dynamics verification method according to claim 1, characterized in that, The liquid sloshing proxy model correction includes: (1) Extraction of on-orbit experimental data The mass fraction involved in the sloshing is calculated by inversely using the ratio of the sloshing force amplitude to the total liquid mass, and then optimized using the frequency response curve. Friction coefficient: Damping characteristics are fitted using the torque decay curve; Dynamic parameters of the pulsating sphere radius: calculated based on the centroid displacement trajectory and the geometric relationship between the liquid-filled tank module; (2) CFD simulation data extraction Flow field image feature extraction: Extract liquid velocity field distribution, pressure field distribution, and centroid trajectory from the simulation data of off-orbit experimental conditions generated by the corrected CFD modeling and simulation tool; (3) Correction of liquid sloshing proxy model Based on the extracted on-orbit experimental data and CFD simulation data, the dynamic equations of the liquid sloshing surrogate model are substituted into the model parameters to correct the liquid sloshing surrogate model.

8. The liquid sloshing dynamics verification method according to claim 7, characterized in that, The model parameters are solved using an optimization algorithm, with the objective function being to minimize the root mean square error of the swaying force / torque.

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