Strip Model Research Articles

Simulation Study of the Effect of Atmospheric Stratification on Aircraft Wake Vortex Encounter

The atmospheric environment is an important factor affecting aircraft wake vortex decay and wake separation. In this paper, numerical calculations and strip modeling are combined to complete an analysis of wake encounter under three atmospheric stratifications expressed in Brunt–Väisälä (BV) frequencies. The SST k-ω turbulence model was chosen for the numerical simulation to complete the evolution of the wake vortex field of the A330 aircraft. The A320 and ERJ190 were selected as the aircraft for wake encounter analysis. The dimensionless roll moment coefficient (RMC) was selected as the indicator to construct a three-dimensional hazard zone for wake encounters and then calculate the wake separation. The results show that the higher BV frequencies correspond to faster wake vortex decay and hazard zone dissipation, and a slower decrease in the height of the hazard zone. The risk level of the ERJ190 is higher than that of the A320 with the same wake intensity, and the wake separation of the A320 following the A330 is 5516 m, which is 25.5% less than the ICAO RECAT separation standard, while the wake separation of the A330 following the ERJ190 is 5803 m, which is 37.6% less than the ICAO RECAT separation standard.

Research on Strip Profile Control Characteristics of 1500 mm Quintic CVC Mill

Compared with cubic Continuously Variable Crown (CVC), quintic CVC presents integrated control capability of quadratic and quartic crown. In order to take full advantage of quintic CVC and have better comprehensive control of the edge wave, center wave, high order wave and complex wave in practical application, it is necessary to further clarify the complicated profile control characteristics of quintic CVC. In this paper, quintic CVC technology in a 1500 mm continuous hot rolling mill production line has been taken as the research object and use finite element method to study its profile control characteristics. Through finite element simulation, an integrated model of rolls and strip was established to analyze the influence of the shifting, bending force and rolling force on strip profile with different strip widths. Both crown adjustment area and transverse stiffness are gained to study the control capability of quintic CVC. The simulation results show that the positive shifting and positive bending of CVC work roll reduce the quadratic crown and increase the quartic crown, and the controlling effect of shifting on both quadratic and quartic crown is more remarkable than that of bending. The control capability of the crown increases with the increase of strip width. That is, wider strip has a larger crown adjustment area. Meanwhile, there is a strong coupling relationship that the increase of quadratic crown can lead to the decrease of the quartic crown, which is not good for the flexible control of strip profile. With the increase of rolling force, the quadratic crown of strip increases significantly, while the quartic crown does not change obviously. Additionally, the increase of strip width significantly increases the transverse stiffness of mill.

Wave propagation in thin pretwisted composite strips with an embedded delamination

In this work, a thin pretwisted and delaminated composite strip is modeled using the variational asymptotic method (VAM). The original 3D problem is reduced to a 2D cross-sectional analysis and a 1D problem along the length of the strip. Damage, in the form of an embedded delamination, is accounted in the strip by following a sublaminate approach. The 1D governing elastodynamic equations of the strip model is solved using the spectral finite element (SFE) method, wherein the structure is modeled as a wave guide. In SFE method, the governing elastodynamic equations are solved in transformed frequency domain to obtain the dynamic stiffness matrix. The guided wave response of the delaminated composite structure for different loads and boundary conditions are subsequently computed. Modal and wave response from SFE using the reduced 1D model are validated by comparing results with those reported in the literature and in some cases with the results obtained from a 3D model using a direct finite element (FE) package. Modal and wave propagation analysis is performed for various dimensions of delamination and composite layup. The analysis provides insight into the dynamic characteristic of partially delaminated strip. The usage of SFE is expected to yield a faster result and lesser computation time than the conventional direct FE method for analyzing and monitoring the delaminated strip exposed to high frequency excitations. Additionally, the capability of the model to investigate the inverse problem of damage detection is demonstrated.

Easy-to-use formulas for predicting ultimate shear resistance and tension field distribution of semi-supported steel plate shear walls

Semi-supported steel plate shear wall (SPSW) is one type of highly effective lateral load-resisting member. However, the current researches on evaluation of ultimate resistance for semi-supported SPSWs are limited. In this paper, a general finite element (FE) model for the two-side connected, semi-supported and four-side connected SPSWs is developed and verified by existing experimental results. The FE results demonstrate that the mechanical behavior of the SPSW is controlled by the in-plane moments of inertia of the vertical boundary elements (VBEs). The hysteretic behavior of the semi-supported SPSW is between the two-side and the four-side connected SPSWs. The minimum initial lateral stiffness, shear resistance and energy dissipation ability of the semi-supported SPSW are 0.43, 0.24 and 0.29 times of the four-side connected SPSW, respectively. Meanwhile, the equations for determining the inclination angle and the span of the tension field in the two-side connected and semi-supported SPSWs are recommend. Furthermore, an easy-to-use formulas are developed for predicting ultimate shear resistance and tension field distribution of SPSWs with various wall-to-frame connections and validated by the experimental and numerical results. The formula analysis results show that the inclination angle and the span of the tension field in two-side connected SPSW vary from 13.3° to 35.8° and 0.53 to 0.76 times the span of the steel plate. The inclination angle and the span of the tension field in the semi-supported SPSW increase rapidly with the rise in in-plane moments of inertia of the VBEs and the height-to-thickness ratio of the steel plate, and then increase gradually to 45° and the span of the steel plate, respectively. Finally, a unified tension strip model for two-side connected, semi-supported, and four-side connected SPSWs is suggested.

Numerical investigation of vortex-induced vibrational responses to a flexible tensioned riser with symmetric grooves in uniform currents

The vortex-induced vibration (VIV) responses to a flexible tensioned cylindrical riser, which the cross section is fixed with two symmetric grooves, is numerically researched by the inhouse viv3D-FOAM-SJTU solver developed based on the OpenFOAM and thick strip model. The Reynolds-averaged Navier-Stokes (RANS) method and Euler-Bernoulli bending beam model are coupled to obtain the hydrodynamics forces and displacements in the vibration process of riser exposed to uniform current. The configurations of riser are designed to spanwise grooves with three different angles (45°,90°, 135°) to the incoming flow, and the three different groove depths and four flow velocities are selected for further investigation. Results show that the flow is broken in the groove, forming the internal small vortices, when the groove degree is 45°, the complex VIV responses are generated due to the change of flow separation point and the interference of internal small vortices on the development of large-scale vortices on the surface of the riser. As the groove degree reaches to 90°, the interference of internal small vortices leads to VIV suppression, and the internal small vortices is released directly into the wake field to enhance VIV with the groove degree = 135°. As the depth of the groove increases, the effect on the flow field is also enhanced, and the vortex structure along the span of the flow field is affected by the position and depth of the groove. Therefore, the geometries of the groove degree = 90° and depths = 0.12D, 0.16D (D is the riser diameter) present the best VIV suppression effect, and the configurations of two other groove degrees are failed to suppress the VIV well.

Residual stress control of hot-rolled strips during run-out table cooling

The strips with good flatness after finish rolling will have flatness defects such as edge wave after run-out table cooling. These defects are caused by the residual stress due to inhomogeneous thermal and microstructural behaviors during the cooling stage. The traditional residual stress control methods rely too much on experience, resulting in poor control effect and poor universality. Therefore, this study proposed two residual stress control methods based on model calculation: water flow central crown and center wave compensation control. The former is mainly based on controlling the uniformity of strip transverse temperature and microstructure. The latter is mainly controlled by mutual compensation of internal stresses. In this paper, the mathematical models of water flow central crown cooling and critical center wave compensation stress were established, respectively. Meanwhile, a post-buckling model of hot-rolled strip was established to calculate the aim flatness value at exit of finishing mill under critical compensation stress. Furthermore, a fully coupled finite element model based on temperature, phase transitions, and stress was developed and it was verified using experimental data. Finally, the above two residual stress control methods were realized in the finite element model. The results showed that the two methods can reduce the residual stress and improve the flatness, and the application of center wave compensation control is more effective.

ЖЕСТКОСТЬ ЖЕЛЕЗОБЕТОННЫХ КОНСТРУКЦИЙ ПРИ ИЗГИБЕ С УЧЁТОМ ПОПЕРЕЧНОЙ И ПРОДОЛЬНОЙ СИЛ (ЧАСТЬ 1)

The paper provides a physical and computational model for determining the parameters of limit states of reinforced concrete structures under complex stress state such as bending with effect of axial and shear forces. The forward and backward transitions for determining the stiffness matrix coefficients of reinforced concrete bar structures with inclined and normal cracks have been constructed on the basis of the adopted cross-section discretization scheme and the duality theorem between force and deformation parameters by A.R. Rzhanitsyn. Determination of the stiffness of structures in the zone of inclined cracks was performed on the basis of the model of composite strips into which the zone with inclined cracks is divided. It is assumed a hypothesis about the character of deformation distribution in a complexly stressed reinforced concrete element with inclined cracks. For this model the effective shear modulus has been obtained. It allows to determine the average relative linear and angular strains of concrete and reinforcement at the point adjacent to the shear joint between inclined cracks. Using this model and the experimentally obtained value of the relative shear in the inclined crack, the dowel forces in the reinforcing bar crossed by the inclined crack were determined. The use of the obtained analytical dependences in the practice of designing reinforced concrete structures allows to clarify significantly the definition of displacements and width of opening of inclined and normal cracks, as well as to bring the calculation and physical model based on experimental data as close as possible.

Алгоритм для учёта потерь на гравитационное излучение при слиянии нейтронных звёзд

The stripping model of stripping in a pair of contact binary neutron stars is one of the promising explanations for short gamma-ray bursts. For correct modeling of the mass transfer stage, a self-consistent accounting for the loss of angular momentum due to the emission of gravitational waves is required. The paper presents a new algorithm for calculating the back-reaction force of gravitational radiation in a pair of binary neutron stars. The calculation is implemented by the smoothed-particle hydrodynamics method (SPH).

Numerical and Experimental Investigation on the Scaling Law of Strip Model Foundation on Cohesionless Soils

In this study, a revised scaling law for laboratory test models of strip foundations on cohesionless soils is proposed. The centrifuge model tests were conducted on a strip model foundation at four different gravity levels (1 g, 5 g, 7.5 g, and 10 g), and the test results were used to calibrate numerical simulations. A set of numerical models were created to simulate full-scale tests and laboratory-scale tests. From the numerical simulations, the behavior of a foundation in the centrifuge model test is similar to that of the full-scale test but is different from the behavior in the laboratory-scale test under the 1 g condition. A parametric study was performed by varying the key variables that are internal friction angle, foundation width, and gravitational acceleration. The stress scale ratio is approximate to the geometric scale ratio in the 1 g model test. However, the settlement conversion requires both the geometric scale ratio and the settlement scale ratio newly proposed. The settlement scale ratio increases with increasing the internal friction angle and geometric scale ratio; accordingly, an equation for calculating the settlement scale ratio is proposed.

Descemet Stripping Only Technique for Corneal Endothelial Damage in Mice.

Descemet stripping only is an emerging surgical technique used to remove central Descemet membrane and corneal endothelial cells in patients with corneal endothelial disease. Here, we describe a murine model of this procedure to help facilitate basic science investigation and evaluation of postoperative outcomes using this surgical technique. Slitlamp biomicroscopy, central corneal thickness assessment (by optical coherence tomography), and immunohistochemistry were used to assess the model through 7 weeks of follow-up. Complete removal of the endothelium and Descemet membrane was confirmed by slitlamp biomicroscopy and by histology. Central corneal thickness peaked at day 1 postinjury and then declined over the course of 2 weeks to a stable level of persistent edema. Seven weeks postinjury, immunohistochemical staining for ZO-1 showed the area of Descemet stripping was fully covered by enlarged and dysmorphic corneal endothelial cell. No significant ocular complications were appreciated through the end of the follow-up. We demonstrate the feasibility of and provide detailed instructions for a murine model of Descemet stripping only. This model provides a potential in vivo platform to investigate the mechanisms and biology of this emerging surgical procedure.

A hybrid model for modelling arbitrary cracks in isotropic plate structures

Damage modelling is essential in preliminary structural design and non-destructive damage detection. This paper investigates changes in natural frequencies of plates due to an arbitrarily aligned crack. A novel hybrid method couples an exact strip model for the intact part with a finite element model for the cracked part. The crack is modelled as a rotational spring with additional rotational freedoms being added to the finite element nodes. The method is validated against published results for through-the-depth cracks. Cracks with varying direction, location, depth and length are used to study the effects of changing the crack parameters.

Influence of roll diameter configuration of 20 high mill on roll shifting control characteristics of wide titanium strip cold rolling

In the production of wide titanium strips cold rolled by 20 high mill, when the diameter of the 1st intermediate roll is reduced, the work roll with a large roll diameter will be used to match it, which is called non-standard roll diameter configuration in this study. In order to master the control characteristics of the 1st intermediate roll shifting under non-standard roll diameter configuration, the coupled static model of roll system and strip is established by FEM, and the model is verified by using the corresponding relationship between the change of load roll gap and the change of titanium strip residual stress after cold rolling. The simulation results show that under the same rolling force, the contact stress peaks of non-standard roll diameter configuration in flat area and cone area of the 1st intermediate roll are about 1.44 times and 1.51 times of standard roll diameter configuration respectively. Compared with the standard roll diameter configuration, when the roll shifting amount increases, the longitudinal plastic strain of non-standard roll diameter increases most significantly in the range of 0-300mm from the titanium strip edge. Under the non-standard roll diameter configuration, increasing the roll shifting amount is more prone to occur the high-order buckle problem.

Prairie strips reduce fecal indicator bacteria concentrations in simulated runoff

AbstractVegetative filter strips (VFS) have shown promising results in reducing the downstream transport of many agroecosystem contaminants. A recently developed type of VFS, prairie strips, has been shown to significantly reduce the impact of corn and soybean production systems on water quality in terms of sediment, nitrogen, and phosphorus losses. This study assessed potential additional benefits of prairie strips to include the reduction of pathogens. To assess the impact of prairie strips on manure‐laden agricultural runoff, we utilized a physical model of prairie strips in a laboratory flume to conduct highly controlled overland flow experiments. Escherichia coli and Enterococcus concentration reductions of up to 45% and 65% were observed for runoff and infiltration flows, respectively, while mass load reductions of up to 65% were observed for surficial runoff flows. The degree of concentration or mass load reductions was dependent on the residence time of the flow within the strip and the partitioning of overland flow running onto the strip to infiltration and runoff flows. Based on our results and a review of the literature, we developed a design method to provide guidance on the width of prairie strip buffer needed to achieve a user‐defined reduction of fecal bacteria concentration.

Pitch controls the flexibility of helical ribbons

Helical objects are often implemented in electronic or mechanical micro-systems, requiring a precise understanding of their mechanical properties. While helices formed by cylindrical filaments have been intensely investigated, little is known about the role of the cross-section of the filament at the basis of the helical shape. We study experimentally the force–extension response of micro-helices fabricated from ultra-thin PMMA ribbons. Leveraging newly achieved control on the helix geometry, the influence of the helical pitch is quantified and a significant stiffening of the helical ribbons with increasing pitch is highlighted. Two phenomena are identified: a mechanical transition from a regime dominated by twisting of the ribbon at small pitch to a bending-dominated regime at high pitch and a purely geometrical effect, specific to helical ribbons. Excellent agreement is found with a previously established analytical model of inextensible elastic strips.

Analysis of Rewetting Characteristics and Process Parameters in Tobacco Strip Redrying Stage

To study the rewetting characteristics of tobacco strips during the redrying stage, a conjugate heat and mass transfer model of tobacco strips was established based on their physical properties. The fundamental relationship between the multiphysical fields and humidity fields of tobacco strips and the key process parameters was considered in this model, and the feasibility of the model was verified via experiments. Based on this model, the transfer and variation laws of the moisture content, humidification rate, and temperature of tobacco strips under different relative humidity and temperature conditions were studied, and the rewetting process parameters of tobacco strips were determined using COMSOL Multiphysics. The results show that this model can be used to study the rewetting characteristics of tobacco strips during the redrying stage. The rewetting of tobacco strips can be divided into two stages, namely, the accelerated stage and approximate constant rate increase stage, where the former stage has a greater impact on the rewetting effect. The higher the relative humidity and temperature, the greater the change in the moisture content, humidification rate, and effective moisture diffusivity, and the faster the increase rate. The best rewetting effect was achieved when the relative humidity was 85% and the temperature was 55 °C. Under these conditions, the moisture content of the tobacco strips was 11% to 13%, the humidification rate was 0.03 %/s to 0.29 %/s, the highest effective moisture diffusivity was 7.8 × 10−10 m2/s, and the maximum activation energy was 37.86 kJ/mol. This study provides a theoretical basis and data support for analyzing the characteristics of the rewetting process and for optimizing the process parameters.

Analysis of horizontal cyclic bearing capacity of pile based on cyclic strain wedge finite element strip method

This paper proposes a cyclic strain wedge finite element strip model to analyze of the cyclic bearing characteristics of pile foundation. First, the strain wedge body is meshed by every soil element, which can assign the stress-strain relationship to each soil element of the wedge body. Then, the equivalent substitution stress‒strain relationship of each wedge layer can be obtained from the stress‒strain relationship of the soil element by the principle of the stress‒strain equivalent substitution method. It can truly reflect the stress-strain relationship of the soil to the stress-strain relationship of the wedge layer and the p-y curve. At the same time, the equivalent cyclic creep constitutive of soil is applied to the strain wedge finite element strip model for the cyclic bearing characteristics of the wedge layer and the cyclic p‒y curve. Finally, the cyclic strain wedge finite element strip model is verified by some tests. The results from the proposed method agree reasonably well with the measured results. It can provide a new method for analyzing the horizontal cyclic bearing characteristics of pile.

Discrete Heaped Model of Tobacco Strips Drying and Characteristics Analysis of Heat and Mass Transfer

To accurately study the drying characteristics of tobacco strips in the process of redrying, a discrete heaped physical model of tobacco strips is built. Based on this model, a convective drying multiphase porous media model of the heaped tobacco strips is established, which considers the binary diffusion and transport of vapor inside and outside the tobacco leaf. The model is solved using COMSOL Multiphysics, and the accuracy of the model is verified by experiments. The changes in hot air velocity, vapor and moisture content, and evaporation rate in heaped tobacco strips with different thicknesses are analyzed. The results show that: it is feasible to study the drying characteristics of tobacco strips in redrying using a discrete heaped model; there were significant differences in water content, evaporation rate, and temperature in different regions of heaped tobacco strips; the increase in heaping thickness will significantly reduce the uniformity of heat and mass transfer of tobacco strips in the process of convection drying. This model can provide a reference for the study of heat and mass transfer in porous media, such as tobacco strips in the heaping state.

Influence Factors of Inherent Characteristics of F5 Cold-Rolling Mill’s Main Drive System

This paper is focused on the inherent characteristics of the main drive system of the F5 cold-rolling mill in a steel plant. First, the main transmission mechanical structure was simplified to a five-inertia torsional vibration model. Secondly, the coupled torsional vibration model of strip and roll was established. The electromechanical coupling model of the motor control system and the motor rotor was established again. Finally, the AMESim software was used to calculate the natural frequency of the main drive system under various coupling conditions, and the influence mechanism of rolling parameters and motor control system parameters on the natural frequency of the main drive system was obtained, and an example of torsional vibration suppression is given by adjusting the control parameters. This study provides a profound theoretical basis for the on-site adjustment of process parameters and electrical control parameters to suppress torsional vibration.

AC Loss Characteristics of HTS Novel Twisted Cables Composed of Soldered-Stacked-Square (3S) Wires

Compared with traditional cables, superconducting multi-stage cables have the natural advantages of greater transmission power and less energy loss, which have gradually attracted attention. However, conventional multi-stage cables are based on low temperature superconducting (LTS) technology and there is considerable scope for improvement in their performance. In this paper, a novel structure of the multi-stage high temperature superconducting (HTS) twisted cable prepared by the soldered-stacked-square (3S) wire is proposed. The AC loss characteristics of the twisted cable are deeply studied by experiments and simulation. Through the experiment, the influence of the voltage-leads on the AC loss measurement accuracy is eliminated, and frequency dependent is shown in the AC loss of the twisted cable. Besides, the simulated value of AC loss is consistent with the experimental value, which verifies the accuracy of the simulation. The AC loss of twisted cable is only 20% of that of the thin strip model, which reveals its outstanding advantages in AC loss.

Centrifuge model and numerical studies of strip footing on reinforced transparent soils

This paper presents the results of centrifuge model tests to investigate the deformation behaviour of unreinforced and reinforced transparent soil foundations under strip loading. A digital image analysis technique was employed to obtain the soil displacement field and strain distribution of reinforcements. Two-dimensional (2D) numerical models were developed and verified using the test results. The soil was modelled as a linearly-elastic perfectly-plastic material with Mohr–Coulomb failure criterion. The reinforcement was characterised using a linearly-elastic model considering rupture behaviour. Moreover, a parametric study was conducted to investigate the load–settlement response of foundations, distribution of reinforcement tension and failure sequence of reinforcements. The experimental and numerical studies show that the results obtained from the numerical simulations are in good agreement with the results of the centrifuge model tests. The 2D finite difference model developed using the user-defined functions coded into the FLAC programme can better simulate the progressive failure of the reinforcement layers in the tests. The failure sequence of reinforcement layers is not affected by the modulus and internal friction angle of soil and the reinforcement length, but is closely related to the combined effect of spacing and number of reinforcement layers and the combined effect of reinforcement stiffness and strength.