A method for calibrating discrete element parameters of a residue-melon stalk-soil mixture by layering

Abstract

The application discloses a kind of residual film-cotton stalk-soil mixture discrete element parameter stratified calibration methods, belong to agricultural material discrete element simulation technical field.Three kinds of material characteristics and basic physical property parameters are obtained, and a differentiated discrete element model is established;Combined with physical test and simulation, local interface parameters, similar material parameters and residual film flexibility-pneumatic parameters are calibrated in turn, and key heterogeneous interface parameters are calibrated;Multiple-component parameter sets are formed by combination, input residual film scattering separation coupling model, and verified by separation index and material migration process.This method can reduce the mutual compensation caused by simultaneous calibration of multiple parameters, improve the physical consistency and parameter reliability of the model, and provide parameter basis for residual film scattering, screening and impurity removal, and pneumatic film conveying process simulation.

Description

Technical Field

[0001] This invention relates to the field of discrete element simulation and parameter calibration technology for agricultural materials, specifically to a method for hierarchical calibration of discrete element parameters for a mixture of residual film, cotton stalks, and soil. The method is applicable to obtaining discrete element simulation parameters of residual film, cotton stalks, and soil during mechanical dispersing, screening for impurities, and pneumatic film conveying processes. It can be used for material motion analysis, structural design, and operational parameter simulation of residual film separation equipment. Background Technology

[0002] Mulching with plastic film has functions such as warming, moisture retention, weed control, and promoting crop growth, and is widely used in cotton cultivation. After mechanical recycling, residual plastic film from farmland is usually mixed with cotton stalks and soil, forming a mixture of residual film, cotton stalks, and soil. This mixture needs to undergo mechanical dispersing, screening for impurities, and pneumatic conveying before it can proceed to subsequent cleaning and resource utilization stages. The Discrete Element Method (DEM) can be used to study the contact, collision, slippage, rolling, accumulation, and migration behavior of materials under the action of mechanical components, and can be combined with fluid simulation methods to analyze the impact of airflow on the movement of residual film, cotton stalks, and soil. The reliability of DEM simulation results is closely related to the material model form, basic physical properties, contact parameters of similar materials, contact parameters of dissimilar materials, and contact parameters between materials and equipment walls.

[0003] Existing discrete element method (DEM) parameter calibration methods mostly focus on single particulate materials or binary mixtures with relatively uniform morphology, making it difficult to simultaneously characterize the differentiated motion characteristics of flexible sheet-like residual films, short, fragmented cotton stalks, and fine-grained soil. Using a single angle of repose or a single hanging response to solve multiple parameters simultaneously can easily lead to mutual compensation between different parameters, resulting in similar macroscopic responses. Using only the hanging response to calibrate residual film parameters makes it difficult to ensure the model can simultaneously reflect the suspension and transport behavior of the residual film in the airflow. Calibrating only single-component parameters without calibrating the heterogeneous interface between the residual film and cotton stalks also fails to accurately describe the relative sliding and collision behavior between the two during mechanical dispersal. Existing methods largely remain at the level of localized experiments such as inclined plane sliding, drop collisions, natural accumulation, or hanging, lacking a process of combining parameters at various levels and inputting them into an actual residual film dispersal and separation model for systematic verification. Therefore, a parameter calibration method is needed that takes into account the morphological differences of the three types of materials, local interface responses, group responses of similar materials, residual film flexibility and aerodynamic responses, heterogeneous interface responses, and overall machine separation responses. Summary of the Invention

[0004] This invention addresses the problems of insufficient material model adaptability, mutual compensation between different types of parameters, difficulty in balancing flexible and aerodynamic responses, and lack of systematic verification of multi-component parameter sets in existing discrete element parameter calibration methods for residual film mixtures. It proposes a layered calibration method for discrete element parameters of residual film-cotton stalk-soil mixtures.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solutions, which are consistent with the content of the claims.

[0006] 1. A method for stratified calibration of discrete element parameters in a mixture of residual film, cotton stalks, and soil, characterized by comprising the following steps:

[0007] S1. Obtain the material characteristics and basic physical property parameters of residual film, cotton stalks and soil, and establish differentiated discrete element models corresponding to the morphological characteristics of the three types of materials;

[0008] S2. Combining physical experiments and discrete element simulation, the single-component parameters are calibrated in the hierarchical order of local interface response, group response of similar materials, and flexible-aerodynamic response of residual film, and the parameters obtained in the previous level are used as fixed inputs for the calibration of the next level.

[0009] S3. Combine physical experiments and discrete element simulation to calibrate key heterogeneous interface contact parameters;

[0010] S4. Combine the basic physical property parameters, single-component parameters and heterogeneous interface contact parameters to form a multi-component parameter set, and input it into the residual film disintegration and separation coupling simulation model;

[0011] S5. The multi-component parameter set is verified by comparing the results of physical experiments on residual membrane dispersion and separation with the results of coupled simulation.

[0012] 2. The discrete element parameter layer calibration method for residual film-cotton stalk-soil mixture according to claim 1, characterized in that, in step S1, a flexible shell unit model is established based on the flexible sheet morphology of the residual film, a rod-shaped non-spherical particle model is established based on the short, fragmented rod-like morphology of the cotton stalk, and a spherical particle model is established based on the fine granular morphology of the soil; the flexible shell unit model is discretely formed by multiple interconnected shell units, the rod-shaped non-spherical particle model includes a rod-shaped main body and arc-shaped ends located at both ends of the rod-shaped main body, and the spherical particle model uses the actual particle size or equivalent particle size to characterize soil particles.

[0013] 3. The discrete element parameter stratification method for a mixture of residual film, cotton stalk, and soil according to claim 1, characterized in that, in step S1, the residual film and cotton stalk are divided into multiple representative particle sizes according to the area distribution of the residual film and the volume distribution of the cotton stalk, respectively. The number of each representative particle size generated in the simulation model is determined according to the mass fraction of the corresponding particle size, and the mixture is generated according to the measured total mass ratio of the residual film, cotton stalk, and soil. In the discrete element model, the normal contact between materials adopts a hysteretic linear spring contact model, the tangential contact between materials adopts a linear spring contact model with a Coulomb limit, and the rolling resistance adopts a rolling resistance model. For soil particles that would significantly increase the computational load if modeled according to the actual particle size, coarse-grained modeling is performed using an equivalent particle size while maintaining the soil accumulation response and the residual film disintegration and separation response.

[0014] 4. The discrete element parameter layered calibration method for the residual film-cotton stalk-soil mixture according to claim 1, characterized in that, in step S2, the local interface response calibration includes conducting local physical tests between cotton stalk and rigid wall, residual film and rigid wall, and residual film and residual film, respectively, and establishing a discrete element simulation model corresponding to the local physical tests; obtaining the critical slip response by gradually increasing the tilt angle of the fixed contact surface, and adjusting the static friction coefficient in the simulation model to match the simulated critical slip response with the measured critical slip response; obtaining the first collision rebound response by allowing the test material to fall freely from a preset release height to a fixed collision surface, and adjusting the recovery factor in the simulation model to match the simulated first collision rebound response with the measured first collision rebound response.

[0015] 5. The method for stratified calibration of discrete element parameters of a residual film-cotton stalk-soil mixture according to claim 1, characterized in that, in step S2, the group response calibration of similar materials includes conducting physical tests on cotton stalk accumulation, physical tests on soil accumulation, and their corresponding discrete element simulation tests, so that cotton stalks and soil are released from the test container and naturally accumulate to form a pile, obtaining lateral images of the pile and determining the measured angle of accumulation; using the static friction coefficient and rolling friction coefficient of similar materials as the factors to be calibrated, establishing a response model between the factors to be calibrated and the simulated angle of accumulation through experimental design and response surface analysis, and obtaining the contact parameters between cotton stalk particles and the contact parameters between soil particles with the measured angle of accumulation as the target.

[0016] 6. The discrete element parameter layered calibration method for residual film-cotton stalk-soil mixture according to claim 1, characterized in that, in step S2, the residual film flexibility-aerodynamic response calibration includes placing the residual film sample on a support and allowing it to hang naturally under gravity; determining the suspension coefficient based on the initial area of ​​the residual film sample, the projected area of ​​the support, and the projected area of ​​the residual film after suspension; placing the residual film sample in an airflow channel and gradually increasing the airflow velocity; when the residual film sample reaches a stable suspension state, determining the stable suspension wind speed based on the airflow velocity, the residual film suspension position, and the geometric parameters of the airflow channel; using the shell element area, elastic ratio, equivalent density, and Young's modulus of the residual film model as calibration factors, establishing a first response model between the calibration factors and the suspension coefficient and a second response model between the calibration factors and the stable suspension wind speed, and performing multi-response solution with the measured suspension coefficient and the measured stable suspension wind speed as common objectives.

[0017] 7. The method for stratified calibration of discrete element parameters of a residual film-cotton stalk-soil mixture according to claim 1, characterized in that, in step S3, the key heterogeneous interface is the contact interface between the residual film and the cotton stalk; the residual film is fixed in the effective sliding area of ​​the inclined plane, and the cotton stalk is used as the sliding body; the static friction coefficient of the residual film-cotton stalk is calibrated according to the measured critical sliding response when the cotton stalk begins to slide continuously on the surface of the residual film; the residual film is flattened and fixed on a horizontal rigid support surface, and the cotton stalk is allowed to fall freely from a preset height to the surface of the residual film; the recovery factor of the residual film-cotton stalk is calibrated according to the measured rebound response after the first collision of the cotton stalk.

[0018] 8. The method for stratified calibration of discrete element parameters of residual film-cotton stalk-soil mixture according to claim 1, characterized in that, in step S4, the residual film disintegration and separation coupled simulation model adopts computational fluid dynamics and discrete element method coupled calculation, and makes the material composition and generation ratio, feeding conditions, airflow conditions, sieving structure and disintegration component motion conditions in the simulation model correspond to the physical test of residual film disintegration and separation.

[0019] 9. The discrete element parameter stratification method for residual film-cotton stalk-soil mixture according to claim 1, characterized in that, in step S5, the proportion of the residual film mass recovered at the target residual film outlet to the residual film mass entering the separation zone is taken as the residual film separation rate, and the proportion of the total mass of cotton stalks and soil in the material at the film outlet to the total mass of the material at the film outlet is taken as the impurity content at the film outlet; the deviations between the simulation results and the physical test results of the residual film separation rate and the impurity content at the film outlet are compared, and the main motion processes of cotton stalks and soil being discharged through the sieve surface and residual film migrating to the film outlet are compared between the simulation test and the physical test.

[0020] Through the above technical solution, this invention connects the establishment of three types of material differentiation models, the hierarchical calibration of single-component parameters, the calibration of key heterogeneous interfaces, the integration of multi-component parameter sets, and the verification of the residual film dispersion and separation process into a complete parameter acquisition process, so that the parameters at each level have corresponding physical experimental basis, and the applicability of the parameter combination is evaluated through system-level separation response.

[0021] As can be seen from the above technical solution, the beneficial technical effects of the present invention are as follows:

[0022] 1. Based on the morphological differences of residual film, cotton stalks and soil, this invention establishes flexible shell unit models, rod-shaped non-spherical particle models and spherical particle models respectively, and performs stratified calibration according to local interface response, group response of similar materials and flexible-aerodynamic response of residual film, so that different parameters are subject to response constraints corresponding to their physical effects, reducing mutual compensation caused by synchronous changes of multiple parameters.

[0023] 2. Under the condition that the contact parameters of the residual film interface are already determined, the present invention uses the sag coefficient and the stable suspension wind speed to jointly constrain the equivalent parameters of the residual film flexibility, and separately calibrates the key heterogeneous interface parameters between the residual film and the cotton stalk, so that the obtained model can simultaneously describe the gravity deformation of the residual film, airflow suspension, and the relative slippage and collision behavior between the residual film and the cotton stalk.

[0024] 3. This invention combines parameters at each level to form a multi-component parameter set, and verifies it using residual membrane separation rate, membrane outlet impurity rate, and main material migration process. This improves the applicability of the parameter set in the simulation of mechanical dispersing, screening and impurity removal, and pneumatic membrane conveying processes, and provides a parameter basis for the structural design and operation parameter optimization of residual membrane separation equipment. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the overall process of the discrete element parameter stratification method for the residual film-cotton stalk-soil mixture of the present invention.

[0026] Figure 2 This is a schematic diagram of the three materials—residual film, cotton stalks, and soil—and their differentiated discrete element models according to the present invention. Figure 2 'a' represents the physical residue of the film. Figure 2 b is a physical cotton stalk. Figure 2 c represents the actual soil sample. Figure 2 d represents the discrete element model of the residual film with different sizes. Figure 2 e represents a model of non-spherical cotton stalk particles of different specifications. Figure 2 f represents the soil spherical particle model. Figure 2 g is a schematic diagram of a partial structure of the residual membrane flexible shell unit.

[0027] Figure 3 This is a schematic diagram of the computational fluid dynamics and discrete element coupled simulation model of the residual film dispersion and separation test bench of the present invention. Detailed Implementation

[0028] To make the technical objectives, implementation process, and beneficial effects of the present invention clearer, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples. The embodiments are used to explain the technical concept and possible implementation methods of the present invention and are not intended to limit the scope of protection of the present invention. Experimental operations, image processing, experimental design, and simulation solution methods not specifically described can be completed using conventional methods in the art.

[0029] The implementation process of this invention includes three stages. The first stage establishes a differentiated discrete element model of the residual film, cotton stalks, and soil, and performs stratified calibration of the single-component parameters of the cotton stalks, soil, and residual film. The second stage calibrates the key heterogeneous interface contact parameters between the residual film and cotton stalks. The third stage combines the parameters at each level to form a multi-component parameter set, and verifies it using a residual film disintegration and separation test bench and a coupled simulation model. The three stages are illustrated through Examples 1, 2, and 3, respectively.

[0030] Example 1: Establishment of three types of material models and stratified calibration of single-component parameters

[0031] This embodiment is used to establish a differentiated discrete element model adapted to the morphological characteristics of residual film, cotton stalks, and soil, and to perform single-component parameter calibration in the order of local interface response, group response of similar materials, and flexible-aerodynamic response of residual film. During implementation, the morphology, size, mass ratio, and basic physical properties of the three types of materials are first determined, and then the local interface parameters are calibrated. Once the local interface parameters are determined, they are kept fixed, and the parameters between cotton stalks and soil particles, as well as the equivalent parameters of residual film flexibility, are further calibrated.

[0032] a. Establishment of cotton stalk model and hierarchical calibration of parameters

[0033] This section first obtains the size distribution and basic physical property parameters of the three types of materials and establishes the corresponding discrete element model. Then, the cotton stalk-steel interface parameters are calibrated by the slippage and collision response of the cotton stalk and the steel wall. Under the condition of fixing the interface parameters, the static friction coefficient and rolling friction coefficient between cotton stalk particles are calibrated by the cotton stalk repose angle.

[0034] Specifically, in this embodiment, a mixture of residual film, cotton stalks, and soil after machine harvesting is obtained and manually grouped into three categories: residual film, cotton stalks, and soil. The mass of each category is then weighed. The average mass ratio of residual film, cotton stalks, and soil is approximately 4:5:1.

[0035] The length and width of the residual film were measured using a steel ruler, and the thickness was measured using a digital micrometer; the length of the cotton stalks was measured using a steel ruler, and the diameter was measured using a digital vernier caliper; the soil particle size distribution was measured using a sieve analysis method; and the mass of the three types of materials was measured using an electronic balance. Each indicator was measured three times and the average value was taken.

[0036] Based on the residual film area distribution range, the residual film was divided into five representative particle sizes. The lengths and widths of each representative particle size were 61.2 mm × 35.4 mm, 103.6 mm × 81.2 mm, 181.3 mm × 109.8 mm, 199.1 mm × 131.5 mm, and 252.6 mm × 133.8 mm, respectively, corresponding to mass fractions of 1.55%, 5.17%, 24.09%, 43.23%, and 25.96%.

[0037] Based on the volume distribution range of cotton stalks, the cotton stalks were divided into five representative particle sizes. The lengths and diameters of each representative particle size were 48.1 mm × 2.63 mm, 63.0 mm × 3.94 mm, 86.7 mm × 5.40 mm, 103.4 mm × 7.56 mm, and 90.1 mm × 13.96 mm, respectively, corresponding to mass fractions of 1.74%, 7.30%, 18.88%, 21.60%, and 50.48%.

[0038] The number of representative particle sizes generated in the simulation model is calculated according to their corresponding mass fractions, and the total amount of each type of material generated is constrained by the overall mass ratio of residual film, cotton stalks and soil, so that the component ratio and size distribution of the simulated mixture correspond to the measured materials.

[0039] The residual film adopts a flexible shell unit model in the form of Custom Shell, which is formed by multiple interconnected shell units discretely; the cotton stalk adopts a rod-shaped non-spherical particle model in the form of Sphero-Cylinder, which includes a rod-shaped main body and arc-shaped parts at both ends; the soil adopts a Sphere spherical particle model.

[0040] The actual soil particle size is mainly distributed in the range of 0.8–1.2 mm. Generating all soil particles according to the actual particle size would significantly increase the number of particles and the amount of computation. Therefore, while maintaining the soil density, packing response and residual film disintegration and separation response, the equivalent soil particle size is set to 5 mm.

[0041] The residual film thickness is 0.01 mm, and the measured density of the residual film material is 1320.0 kg / m³. 3 The Poisson's ratio is 0.29; the cotton stalk density is 1080.0 kg / m³. 3 The Poisson's ratio is 0.35, the Young's modulus is 1790 MPa, and the soil density is 1480.0 kg / m³. 3 The Poisson's ratio is 0.37, and the Young's modulus is 13 MPa. The baffles, screen surfaces, guide shells, and inner walls of the air ducts, which are in primary contact with the mixture, are all treated with 45 steel.

[0042] In the discrete element model, the normal contact between materials adopts the Hysteretic Linear Spring contact model, the tangential contact adopts the Linear Spring Coulomb Limit contact model, and the rolling resistance adopts the Type C rolling resistance model. The sliding friction coefficient is determined according to the corresponding static friction coefficient according to a preset ratio; in this embodiment, it is taken as 0.85 times the corresponding static friction coefficient.

[0043] The cotton stalk parameters were calibrated in two levels: local interface parameter calibration between cotton stalk and steel and collective response calibration among cotton stalk particles.

[0044] The static friction coefficient between cotton stalks and steel was determined using an inclined plane slip test. Five short, fragmented cotton stalks of roughly the same length and shape were selected and arranged side-by-side to form a sliding body, with the axial direction of the cotton stalks aligned with the sliding direction. A 300 mm × 200 mm 45 steel plate was used as the fixed contact surface, and the inclination angle of the steel plate was slowly increased. The critical slip angle was recorded when the cotton stalk sliding body began to slide continuously relative to the steel plate.

[0045] The coefficient of static friction between the cotton stalk and the steel wall is calculated using the following formula:

[0046] (1)

[0047] In the formula, μ is the static friction coefficient of the contact interface to be measured; α is the critical slip angle at which the material to be measured begins to slide continuously relative to the fixed contact surface, in degrees.

[0048] The experiment was repeated three times, and the average value was taken. The measured critical slip angle of the cotton stalk-steel line was 20.32°. A slope model with the same steel plate size, number of cotton stalks, arrangement, and tilting process as the physical experiment was established in a discrete element method (DEM) simulation platform. The static friction coefficient of the cotton stalk-steel line was adjusted based on the measured critical slip angle. After calibration, the static friction coefficient of the cotton stalk-steel line was 0.38, corresponding to a simulated critical slip angle of 20.63°.

[0049] The cotton stalk-steel recovery factor was determined using a drop impact test. A 45 steel plate was placed horizontally, and individual cotton stalk samples were released freely from a height of 300 mm above the steel plate. The rebound height of the cotton stalk after the first collision with the steel plate was recorded using a high-speed camera.

[0050] The factor of recovery between the cotton stalk and the steel wall is calculated using the following formula:

[0051] (2)

[0052] In the formula, e is the recovery factor; h0 is the release height of the material to be tested; h1 is the rebound height of the material to be tested after the first collision with the fixed collision surface, and h0 and h1 use the same unit of length.

[0053] The experiment was repeated three times and the average value was taken. The measured initial rebound height was 75.4 mm. A drop collision simulation model with the same release height and impact surface was established, and the cotton stalk-steel recovery factor was adjusted with the measured initial rebound height as the target. After calibration, the cotton stalk-steel recovery factor was 0.49, corresponding to a simulated initial rebound height of 76.1 mm.

[0054] After completing the calibration of the cotton stalk-steel interface parameters, the static friction coefficient and recovery factor of the cotton stalk-steel interface are fixed and used for the stacking response calibration of the contact parameters between cotton stalk particles.

[0055] Cotton stalk samples were placed into a cylinder with an inner diameter of 300 mm and a height of 600 mm. The cylinder was then lifted vertically at a speed of 0.02 m / s, allowing the cotton stalks to fall naturally under gravity and form a pile. Images were acquired from the side of the pile, and the images were binarized and bounded to fit the boundaries. The inclination angles of the two sides of the pile were extracted, and the average of the inclination angles of the two sides was taken as the cotton stalk repose angle. The experiment was repeated three times, and the measured cotton stalk repose angle was 27.54°.

[0056] Under the condition of fixed cotton stalk-steel interface parameters and other non-calibrated parameters, a cylindrical lifting simulation model under the same conditions was established. Using the cotton stalk-to-cotton stalk static friction coefficient and the cotton stalk-to-cotton stalk rolling friction coefficient as the calibration factors, a central composite experimental design was adopted to arrange multiple parameter combinations, and a quadratic response model was established using the simulated angle of repose as the response value.

[0057] The response model has a coefficient of determination of 0.967 and an adjusted coefficient of determination of 0.943, which can describe the response relationship between the contact parameters between cotton stalk particles and the angle of repose. Using the measured angle of repose of the cotton stalk (27.54°) as the target value, the coefficient of static friction between cotton stalks is found to be 0.43, and the coefficient of rolling friction between cotton stalks is 0.06.

[0058] Inputting the above parameters into the cotton stalk stacking simulation model yielded a simulated stacking angle of 27.71°. The surface profile, surface undulations, and bottom spreading range of the simulated stockpile basically correspond to those of the physical experiment, indicating that the cotton stalk parameters obtained through local interface calibration and stacking response calibration can characterize the wall slippage, collision rebound, and mass stacking behavior of cotton stalks.

[0059] b. Soil interparticle parameter calibration

[0060] This section uses the collective response formed during the natural accumulation of soil as the basis for parameter calibration. Under the conditions of fixed basic soil physical parameters, equivalent particle size and non-calibrated contact parameters, the response relationship between the static friction coefficient and rolling friction coefficient between soil particles and the soil angle of accumulation is established.

[0061] Soil samples were placed into a cylinder with an inner diameter of 70 mm and a height of 150 mm. The cylinder was then lifted vertically at a speed of 0.01 m / s, allowing the soil particles to fall naturally under gravity and form a pile.

[0062] Lateral images of the soil pile were acquired, binarized, and boundary fitted to obtain the surface inclination angles on both sides of the pile. The average of the surface inclination angles on both sides was used as the soil angle of accumulation. The experiment was repeated three times, and the measured soil angle of accumulation was 36.34°.

[0063] A cylindrical lifting model corresponding to the physical test conditions was established in the discrete element simulation platform, and the soil density, equivalent particle size, restitution factor, and non-calibrated parameters between the soil and the cylinder wall were fixed.

[0064] Using soil-soil static friction coefficient and soil-soil rolling friction coefficient as calibration factors, multiple parameter combinations were obtained through a central composite experimental design, and soil accumulation simulations were conducted. Based on the simulation results, a quadratic response model was established between the two calibration parameters and the simulated soil accumulation angle.

[0065] The soil angle of accumulation response model has a determination coefficient of 0.963 and an adjusted determination coefficient of 0.936, which can describe the response relationship between soil particle contact parameters and soil angle of accumulation.

[0066] Using the measured soil angle of accumulation of 36.34° as the target, the soil-soil static friction coefficient was found to be 0.62, and the soil-soil rolling friction coefficient was found to be 0.19.

[0067] Inputting the above parameters into the soil accumulation simulation model yielded a simulated accumulation angle of 36.76°. The contour, height, and bottom spreading range of the simulated pile basically correspond to those of the physical experiment, indicating that the obtained parameters can characterize the natural accumulation and mass flow behavior of soil particles.

[0068] c. Calibration of residual film interface parameters and flexible-pneumatic dual response

[0069] This section first uses the inclined plane sliding and drop collision response to calibrate the local interface contact parameters of the residual membrane-steel and residual membrane-residual membrane. Then, the interface parameters are fixed, and the residual membrane sag coefficient and stable suspension wind speed are used as dual response indicators to jointly calibrate the residual membrane shell unit area, elastic ratio, equivalent density and Young's modulus, so that the same set of model parameters simultaneously satisfies the gravity deformation response and airflow suspension response.

[0070] A 60 mm × 60 mm residual film sample with no obvious wrinkles or damage was selected as the slip body. When conducting the residual film-steel interface test, a 300 mm × 200 mm 45 steel plate was used as the fixed contact surface; when conducting the residual film-residual film interface test, a layer of residual film was flattened and fixed in the effective slip area of ​​the inclined plane as the fixed contact surface.

[0071] Slowly increase the inclination angle of the inclined plane. When the residual film sample begins to slide continuously relative to the fixed contact surface, record the critical slip angle and determine the initial value of the corresponding static friction coefficient according to formula (1).

[0072] The experiment was repeated three times and the average value was taken. The measured critical slip angles at the residual film-steel interface and the residual film-residual film interface were 24.43° and 27.35°, respectively. Simulation models for slip on the residual film-steel and residual film-residual film inclined planes were established respectively, and the corresponding static friction coefficients were adjusted with the measured critical slip angles as the target.

[0073] After calibration, the static friction coefficient between the residual film and steel is 0.46, and the static friction coefficient between the residual film and the residual film is 0.57, corresponding to simulated critical slip angles of 23.92° and 26.84°, respectively.

[0074] The residual film-steel recovery factor was determined by drop impact test. A 45 steel plate was placed horizontally and the residual film sample was released freely from a height of 300 mm. The rebound height of the residual film after the first collision with the steel plate was recorded, and the initial value of the recovery factor was determined according to formula (2).

[0075] The experiment was repeated three times and the average value was taken. The measured initial rebound height was 14.5 mm. A drop impact simulation model under the same conditions was established, and the residual film-steel restitution factor was calibrated using the measured initial rebound height as the target. After calibration, the residual film-steel restitution factor was 0.23, corresponding to a simulated initial rebound height of 14.7 mm.

[0076] After completing the calibration of the local interface parameters of the residual film, the static friction coefficient between the residual film and steel, the static friction coefficient between the residual film and the residual film, and the recovery factor between the residual film and steel are fixed, and then the joint calibration of the flexible-aerodynamic dual response of the residual film is performed.

[0077] The residual film suspension test used a circular residual film specimen with a diameter of 240 mm and a thickness of 0.01 mm. The residual film specimen was placed on a support plate, allowing the edges of the residual film to hang naturally under gravity. After the suspension state stabilized, a top-view image was acquired, and the projected contour of the residual film after suspension was extracted.

[0078] The residual film sag coefficient is calculated according to the following formula:

[0079] (3)

[0080] In the formula, DC rf S is the residual film sag coefficient. pS is the projected area of ​​the residual membrane after it is suspended; c S0 is the projected area of ​​the support disk; S0 is the initial area of ​​the residual film sample, S0... p S c It uses the same area unit as S0.

[0081] The experiment was repeated three times, and the measured residual film sag coefficient was 0.41.

[0082] The residual film suspension test uses a conical airflow channel. The residual film sample is placed flat on the screen at the bottom of the conical tube, and the airflow velocity is gradually increased. When the residual film sample reaches a stable suspension state inside the conical tube, the wind speed at the bottom of the conical tube and the vertical height of the center of the residual film sample from the bottom of the conical tube are recorded.

[0083] The stable suspended wind speed at the location of the residual film is calculated according to the following formula:

[0084] (4)

[0085] In the formula, vsus,rf is the residual film stable suspension wind speed; v b d0 is the wind speed at the bottom of the conical tube; h is the vertical height of the residual film sample center from the bottom of the conical tube; β is the half-cone angle of the conical tube. d0 and h use the same unit of length.

[0086] In this embodiment, the semi-cone angle of the conical tube is 3.5°, and the measured stable suspension wind speed of the residual film is 2.33 m / s.

[0087] Separate simulation models for residual membrane sag and suspension were established, using shell element area, elastic ratio, equivalent density, and Young's modulus as calibration factors. Multiple parameter combinations were arranged using a central composite experimental design. Suspension and suspension simulations were conducted for each parameter combination, establishing a first response model between the four factors and the sag coefficient, and a second response model between the four factors and the stable suspension wind speed.

[0088] The coefficients of determination and adjusted coefficients of determination for the sag coefficient response model are 0.977 and 0.956, respectively, while the coefficients of determination and adjusted coefficients of determination for the stable suspended wind speed response model are 0.949 and 0.902, respectively. Both response models can describe the relationship between the equivalent parameters of the residual membrane flexibility and the sag and suspension responses.

[0089] Using the measured sag coefficient of 0.41 and the measured stable suspended wind speed of 2.33 m / s as common objectives, a multi-response synthesis solution was performed, yielding a residual membrane shell element area of ​​164.1 mm². 2 Its elastic ratio is 0.85, and its equivalent density is 230.6 kg / m³. 3 The Young's modulus is 5.59 MPa.

[0090] Inputting the above parameter combination into the corresponding simulation model yields a simulated sag coefficient of 0.42 and a simulated stable suspended wind speed of 2.36 m / s. The simulated sag morphology and stable suspension state of the residual membrane basically correspond to those of the physical experiment.

[0091] Among them, 230.6 kg / m 3 The model equivalent density, which simultaneously satisfies the flexible deformation and aerodynamic suspension response of the residual film, is not equivalent to the measured bulk density of the residual film material. The shell element area, elastic ratio, equivalent density, and Young's modulus constitute a set of equivalent parameters for the residual film flexibility, constrained by both the sag response and the stable suspension response.

[0092] This embodiment obtains local interface parameters and interparticle contact parameters of cotton stalks, interparticle contact parameters of soil, and interface contact parameters and flexibility equivalent parameters of residual film. Each parameter is constrained by the experimental response corresponding to its main physical action, and the determined parameters remain unchanged in the subsequent calibration stage, thus forming a single-component parameter set with a clear source.

[0093] Example 2: Calibration of parameters at the heterogeneous interface between residual film and cotton stalk

[0094] This embodiment is used to calibrate the key heterogeneous interface contact parameters between the residual film and the cotton stalk. Based on the model parameters of the residual film and the cotton stalk obtained in Embodiment 1, the static friction coefficient and recovery factor of the residual film-cotton stalk are calibrated using the inclined plane sliding response and the drop collision response, respectively, and the obtained parameters are fixedly input into the subsequent multi-component residual film disintegration and separation model.

[0095] a. Calibration of static friction coefficient between residual film and cotton stalk

[0096] This section uses the critical slip response when the cotton stalk begins to slide continuously on the surface of the residual film as the calibration target, so that the static friction parameters of the residual film-cotton stalk in the simulation model can characterize the relative slip behavior between the cotton stalk and the residual film during the mechanical dispersal process.

[0097] Specifically, in this embodiment, the residual film is flattened and fixed on the surface of a 300 mm × 200 mm 45 steel plate, ensuring that the residual film completely covers the effective sliding area, with cotton stalks as the sliding body.

[0098] Slowly increase the tilt angle of the steel plate. When the cotton stalk begins to slide continuously relative to the surface of the residual film, record the critical slip angle and determine the initial value of the static friction coefficient of the residual film-cotton stalk according to formula (1).

[0099] The experiment was repeated three times and the average value was taken. The measured critical slip angle of the residual film-cotton stalk was 27.02°.

[0100] A simulation model with the same residual film laying method, cotton stalk shape, initial position and inclined plane motion conditions as the physical experiment was established in the discrete element simulation platform. The static friction coefficient of the residual film-cotton stalk was adjusted with the measured critical slip angle as the calibration target.

[0101] After calibration, the static friction coefficient between the residual film and the cotton stalk is 0.52, corresponding to a simulated critical slip angle of 27.25°. The simulated critical slip response is close to that of the physical experiment, indicating that the obtained static friction coefficient can describe the continuous slip behavior of the cotton stalk on the residual film surface.

[0102] b. Calibration of residual film-cotton stalk recovery factor

[0103] This section uses the rebound response after the first collision between the cotton stalk and the surface of the residual film as the calibration target, so that the recovery factor can characterize the energy loss and rebound characteristics during the collision process.

[0104] The residual film is flattened and fixed on a horizontally placed rigid support surface, so that the surface of the residual film is free of obvious wrinkles or looseness.

[0105] The cotton stalk monomer sample is released freely from a preset height, causing the cotton stalk to collide with the surface of the residual film. The rebound height of the cotton stalk after the first collision is recorded by a high-speed camera device, and the initial value of the residual film-cotton stalk recovery factor is determined according to formula (2).

[0106] The experiment was repeated 3 times and the average value was taken. The measured height of the cotton stalk rebounding for the first time was 12.0 mm.

[0107] A drop collision model with the same release conditions, residual film fixing method, and collision contact surface was established in the discrete element simulation platform. The residual film-cotton stalk recovery factor was adjusted with the measured first rebound height as the target.

[0108] The calibrated residual film-cotton stalk recovery factor is 0.20, corresponding to a simulated initial rebound height of 12.3 mm. The simulated initial collision rebound response is close to that of the physical experiment, indicating that the obtained recovery factor can describe the rebound characteristics after the cotton stalk collides with the residual film.

[0109] c. Organizing and fixing input parameters for heterogeneous interfaces

[0110] This section organizes the parameters of the residual film-cotton stalk interface and clarifies their transmission method in the multi-component residual film disintegration and separation model, so as to avoid parameter compensation caused by adjusting key heterogeneous interface parameters and other contact parameters at the same time.

[0111] The static friction coefficient of the residual film-cotton stalk (0.52) and the recovery coefficient of the residual film-cotton stalk (0.20) obtained by calibration were used as the main heterogeneous interface parameters between the residual film and the cotton stalk. The residual film disintegration and separation model of Example 3 was fixed and no longer optimized as a whole with other parameters.

[0112] For contact interface parameters such as residual film-soil, cotton stalk-soil, and soil-steel that have not been calibrated through independent physical tests, they can be determined based on existing material test data and used as fixed inputs. These fixed input parameters are not the parameters actually calibrated through independent physical tests in this embodiment, nor are they involved in solving the response of the residual film-cotton stalk heterogeneous interface.

[0113] The static friction coefficient and recovery factor of the residual film-cotton stalk obtained in this embodiment correspond to the relative slip response and collision rebound response of the two, respectively, so that the key heterogeneous interface parameters have a clear physical experimental source and can be used to characterize the contact, slip and collision behavior between the residual film and the cotton stalk during the residual film dispersal process.

[0114] Example 3: Verification of Multi-component Parameter Set Integration and Residual Membrane Dispersion

[0115] This embodiment combines the single-component parameters obtained in Example 1 and the residual film-cotton stalk heterogeneous interface parameters obtained in Example 2 to form a multi-component parameter set, which is then input into the residual film dispersing and separation coupled simulation model. By comparing the residual film separation rate, the impurity content at the film outlet, and the main migration processes of the three types of materials, the applicability of the multi-component parameter set to the actual residual film dispersing, screening and impurity removal, and pneumatic film conveying processes is evaluated.

[0116] a. Establishment of the residual film dispersion and separation test bench and coupled simulation model

[0117] This section establishes a physical test bench for residual film dispersing and separation, and a coupled simulation model corresponding to its structure and operating conditions, ensuring that the material composition, feeding conditions, dispersing component movement conditions, and airflow conditions remain consistent between the physical test and the simulation test.

[0118] Specifically, in this embodiment, the residual film dispersing and separation test bench includes a frame, a feed inlet, a deflector screw shaft, a separation sieve, a waste removal screw shaft, a waste outlet, a film outlet cover, a film outlet pipe, a film discharge pipe, and a centrifugal fan.

[0119] When the test bench is in operation, a mixture of residual film, cotton stalks, and soil is continuously fed into the separation chamber through the feed inlet. The auger shaft drives the auger to rotate, and the auger continuously beats and turns the mixture, gradually separating the cotton stalks and soil that are attached to or wrapped around the surface of the residual film.

[0120] After separation, the cotton stalks and soil fall through the separating screen into the lower impurity removal device under the disturbance of the baffle plate and the action of gravity, and are discharged from the impurity outlet by the impurity removal spiral shaft. The centrifugal fan creates a negative pressure airflow in the separation chamber, and the light residual film floats up under the action of the airflow and migrates along the direction of the film outlet cover, film outlet pipe and film discharge pipe.

[0121] The three-dimensional model of the residual film disintegration and separation test bench was imported into the discrete element simulation platform and the fluid simulation platform respectively to establish a coupled simulation model of computational fluid dynamics and discrete element method.

[0122] The fluid simulation model sets inlet and outlet boundary conditions corresponding to the test bench, and the discrete element simulation model inputs the multi-component parameter sets obtained in Example 1 and Example 2.

[0123] The mass ratio of residual film, cotton stalks and soil, the representative particle size generation ratio, the feeding position and feeding amount, the separation screen structure, the moving conditions of the deflector and the airflow conditions in the simulation model are all consistent with those in the physical experiment.

[0124] This embodiment uses a representative working condition for verification: the feed rate of the mixture is 1500 kg / h, the rotation speed of the auger shaft is 400 r / min, and the air velocity at the membrane outlet is 8 m / s.

[0125] b. Separation performance evaluation indicators and calculation methods

[0126] This section evaluates the recovery effect of residual film and the purity of the material at the outlet by using the residual film separation rate and the impurity content at the outlet, respectively, while observing the main migration processes of residual film, cotton stalks and soil in the separation chamber.

[0127] The target residual film outlet material and the impurity outlet material from the physical test and simulation test were collected respectively, and the residual film, cotton stalks and soil were sorted and weighed.

[0128] The residual membrane separation rate is calculated according to the following formula:

[0129] (5)

[0130] In the formula, η f The residual membrane separation rate; m f1 The residual film quality recovered at the target residual film outlet; m f2 For the residual film quality entering the separation zone, m f1 and m f2 Use the same unit of mass.

[0131] The impurity content at the membrane outlet is calculated using the following formula:

[0132] (6)

[0133] In the formula, β out Impurity content at the membrane outlet; m o1 The total mass of cotton stalks and soil in the material exiting the film; m o2 m is the total mass of the material exiting the membrane outlet. o1 and m o2 Use the same unit of mass.

[0134] The physical experiment was repeated three times and the average value was taken. In addition to comparing the residual film separation rate and the impurity content at the film outlet, the process of the disintegration by the detonator, the process of cotton stalks and soil being discharged through the sieve surface, and the process of residual film migrating to the film outlet under the action of negative pressure airflow were also observed in the physical and simulation experiments.

[0135] c. Separation results and parameter set verification

[0136] This section determines whether a multi-component parameter set can characterize the movement and separation behavior of residual film, cotton stalks, and soil during mechanical dispersing, screening and impurity removal, and pneumatic film conveying based on separation performance indicators and material migration processes.

[0137] Under the aforementioned representative operating conditions, the physical test value of the residual membrane separation rate was 89.3%, while the simulated value was 92.8%, a difference of 3.5 percentage points; the physical test value of the impurity content at the membrane outlet was 12.6%, while the simulated value was 9.5%, a difference of 3.1 percentage points.

[0138] From the perspective of material migration process, after the mixture of residual film, cotton stalks and soil enters the separation chamber, the baffle continuously beats and turns the mixture to promote the separation of residual film from cotton stalks and soil.

[0139] Cotton stalks and soil are mainly discharged through the separation screen in the first half of the separation chamber, and their distribution in the separation chamber gradually decreases along the direction of material movement; the residual film mainly floats up under the action of negative pressure airflow and migrates along the direction of the film outlet cover and film outlet pipe.

[0140] The simulation model reproduces the main process of "dispersing and separating by the deflector, screening and discharging of cotton stalks and soil in the first stage, and conveying the residual film upwards." The material migration trend in the simulation is basically consistent with that in the physical experiment.

[0141] When the simulation results of residual film separation rate and impurity content at the film outlet are close to the physical test results, and the simulation model can reproduce the main process of cotton stalks and soil being discharged through the screen and residual film migrating to the film outlet, the multi-component parameter set is determined as the parameter set that meets the simulation requirements of the residual film dispersing and separation process.

[0142] The feed rate, rotary speed of the deflector screw shaft, and outlet air velocity in this embodiment are used to illustrate the verification process of the multi-component parameter set under a representative operating condition and do not constitute a necessary limitation of the method of this invention. For other residual film separation equipment, the feed rate, rotation speed of the dispersing component, screen structure, and airflow velocity can be adjusted according to the equipment structure and operating conditions, and corresponding physical tests and simulation verifications can be carried out.

[0143] This invention systematically elucidates a method for hierarchical calibration of discrete element parameters in a residual film-cotton stalk-soil mixture through three embodiments: establishing differentiated discrete element models for three types of materials and hierarchical calibration of single-component parameters; calibrating key heterogeneous interface parameters between residual film and cotton stalk; and integrating multi-component parameter sets and verifying residual film dispersion and separation. Parameters at each level are constrained by the experimental responses corresponding to their physical effects. Parameters obtained at previous levels remain fixed in subsequent levels, clarifying the source and transmission relationship of parameters and reducing mutual compensation caused by simultaneous changes in multiple parameters.

[0144] The results show that the differentiated discrete element model established in this invention can characterize the morphology and motion characteristics of flexible residual film, short cotton stalks, and fine-grained soil, respectively. The obtained parameter set can describe the sliding and collision behavior of cotton stalks with the steel wall, the mass accumulation behavior of cotton stalks and soil, the interfacial contact, flexible suspension, and airflow suspension behavior of the residual film, as well as the relative sliding and collision rebound behavior between the residual film and cotton stalks. After combining the parameters of each level, the simulation results of residual film separation rate and impurity content at the film outlet are close to the physical test results. The simulation model can reproduce the main migration behaviors of residual film, cotton stalks, and soil during the dispersing, screening, and pneumatic conveying processes.

[0145] This invention provides a multi-component material model and parameter acquisition method for simulation analysis of residual film dispersing, screening and impurity removal, and pneumatic film conveying processes. It can be used for structural design, operational parameter analysis, and scheme comparison of residual film separation equipment. For residual film mixtures with different sources, moisture contents, degrees of breakage, or component ratios, as well as other multi-component separation processes containing flexible sheet materials, rod-shaped materials, and granular materials, parameters can be obtained by referring to the stratified calibration method and verification process of this invention. The above embodiments are only for illustrating this invention. Any modifications, equivalent substitutions, or adaptive adjustments made based on the technical concept and essence of this invention should be included within the protection scope of this invention.

Claims

1. A method for stratified calibration of discrete element parameters in a mixture of residual film, cotton stalks, and soil, characterized in that, Includes the following steps: S1. Obtain the material characteristics and basic physical property parameters of residual film, cotton stalks and soil, and establish differentiated discrete element models corresponding to the morphological characteristics of the three types of materials; S2. Combining physical experiments and discrete element simulation, the single-component parameters are calibrated in the hierarchical order of local interface response, group response of similar materials, and flexible-aerodynamic response of residual film, and the parameters obtained in the previous level are used as fixed inputs for the calibration of the next level. S3. Combine physical experiments and discrete element simulation to calibrate key heterogeneous interface contact parameters; S4. Combine the basic physical property parameters, single-component parameters and heterogeneous interface contact parameters to form a multi-component parameter set, and input it into the residual film disintegration and separation coupling simulation model; S5. The multi-component parameter set is verified by comparing the results of physical experiments on residual membrane dispersion and separation with the results of coupled simulation.

2. The method for stratified calibration of discrete element parameters for residual film-cotton stalk-soil mixture according to claim 1, characterized in that, In step S1, a flexible shell unit model is established based on the flexible sheet morphology of the residual film, a rod-shaped non-spherical particle model is established based on the short, fragmented rod-like morphology of the cotton stalk, and a spherical particle model is established based on the fine-grained granular morphology of the soil. The flexible shell unit model is formed by discretely connecting multiple shell units. The rod-shaped non-spherical particle model includes a rod-shaped main body and arc-shaped ends located at both ends of the rod-shaped main body. The spherical particle model uses the actual particle size or equivalent particle size to characterize soil particles.

3. The method for stratified calibration of discrete element parameters for a mixture of residual film, cotton stalks, and soil according to claim 1, characterized in that, In step S1, the residual film and cotton stalks are divided into multiple representative particle sizes based on the residual film area distribution and cotton stalk volume distribution, respectively. The number of each representative particle size generated in the simulation model is determined according to the mass fraction of the corresponding particle size, and a mixture is generated according to the measured total mass ratio of residual film, cotton stalks and soil. In the discrete element model, the normal contact between materials adopts the hysteretic linear spring contact model, the tangential contact between materials adopts the linear spring contact model with Coulomb limit, and the rolling resistance adopts the rolling resistance model. For soil particles that would significantly increase the computational load if modeled according to the actual particle size, coarse-grained modeling is performed using the equivalent particle size while maintaining the soil accumulation response and residual film disintegration and separation response.

4. The method for stratified calibration of discrete element parameters for a mixture of residual film, cotton stalks, and soil according to claim 1, characterized in that, In step S2, the local interface response calibration includes conducting local physical tests between cotton stalks and rigid walls, residual film and rigid walls, and residual film and residual film, and establishing discrete element simulation models corresponding to the local physical tests; obtaining the critical slip response by gradually increasing the tilt angle of the fixed contact surface, and adjusting the static friction coefficient in the simulation model to match the simulated critical slip response with the measured critical slip response; obtaining the first collision rebound response by allowing the test material to fall freely from a preset release height to a fixed collision surface, and adjusting the recovery factor in the simulation model to match the simulated first collision rebound response with the measured first collision rebound response.

5. The method for stratified calibration of discrete element parameters for a mixture of residual film, cotton stalks, and soil according to claim 1, characterized in that, In step S2, the group response calibration of similar materials includes conducting physical tests of cotton stalk accumulation, physical tests of soil accumulation, and their corresponding discrete element simulation tests, so that cotton stalks and soil are released from the test container and naturally accumulate to form a material pile, obtaining lateral images of the material pile and determining the measured accumulation angle; Using the static friction coefficient and rolling friction coefficient of similar materials as the calibration factors, a response model between the calibration factors and the simulated angle of repose was established through experimental design and response surface analysis. The contact parameters between cotton stalk particles and soil particles were obtained with the measured angle of repose as the target.

6. The method for stratified calibration of discrete element parameters for a mixture of residual film, cotton stalks, and soil according to claim 1, characterized in that, In step S2, the residual film flexibility-aerodynamic response calibration includes placing the residual film sample on a support and allowing it to hang naturally under gravity, determining the suspension coefficient based on the initial area of ​​the residual film sample, the projected area of ​​the support, and the projected area of ​​the residual film after suspension; placing the residual film sample in an airflow channel and gradually increasing the airflow velocity, and determining the stable suspension wind speed based on the airflow velocity, the residual film suspension position, and the geometric parameters of the airflow channel when the residual film sample reaches a stable suspension state. Using the shell element area, elastic ratio, equivalent density, and Young's modulus of the residual membrane model as calibration factors, a first response model between the calibration factors and the sag coefficient and a second response model between the calibration factors and the stable suspended wind speed are established respectively. The multi-response solution is performed with the measured sag coefficient and the measured stable suspended wind speed as common objectives.

7. The method for stratified calibration of discrete element parameters for a mixture of residual film, cotton stalks, and soil according to claim 1, characterized in that, In step S3, the key heterogeneous interface is the contact interface between the residual film and the cotton stalk; the residual film is fixed in the effective sliding area of ​​the inclined plane, and the cotton stalk is used as the sliding body. The static friction coefficient of the residual film-cotton stalk is calibrated according to the measured critical sliding response when the cotton stalk begins to slide continuously on the surface of the residual film; the residual film is flattened and fixed on a horizontal rigid support surface, and the cotton stalk is allowed to fall freely from a preset height to the surface of the residual film. The recovery factor of the residual film-cotton stalk is calibrated according to the measured rebound response after the first collision of the cotton stalk.

8. The method for stratified calibration of discrete element parameters for a mixture of residual film, cotton stalks, and soil according to claim 1, characterized in that, In step S4, the residual film disintegration and separation coupled simulation model is calculated using computational fluid dynamics and discrete element method, and the material composition and generation ratio, feeding conditions, airflow conditions, sieving structure and disintegration component motion conditions in the simulation model correspond to the physical test of residual film disintegration and separation.

9. The method for stratified calibration of discrete element parameters for a mixture of residual film, cotton stalks, and soil according to claim 1, characterized in that, In step S5, the residual film separation rate is defined as the ratio of the mass of residual film recovered at the target residual film outlet to the mass of residual film entering the separation zone, and the impurity content at the film outlet is defined as the ratio of the total mass of cotton stalks and soil in the material at the film outlet to the total mass of the material at the film outlet. The deviations between the simulation results and the physical test results of the residual film separation rate and the impurity content at the film outlet are compared, and the main motion processes of cotton stalks and soil being discharged through the screen and residual film migrating to the film outlet are compared between the simulation test and the physical test.

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