Tunnel Simulation Research Articles

Statistical device simulations of III-V nanowire resonant tunneling diodes as physical unclonable functions source

In this paper, utilising the non-equilibrium Green’s function (NEGF) formalism within the new device simulator NESS (Nano-Electronic Software Simulator) developed at the University of Glasgow’s Device Modelling Group, we present quantum mechanical simulations of current flow in double-barrier III-V GaAs-AlGaAs nanowire resonant tunneling diodes (RTDs). NESS is a fast and modular Technology Computer Aided Design (TCAD) tool with flexible architecture which can take into account various sources of statistical variability in nanodevices. The aim of this work is to show that, in the RTD devices with nano-scale dimensions, there is a direct correlation between the position and the numbers of random dopants and the key device parameters, e.g., position of the resonant-peak (VR) variations as well as the shape and number of peaks in the output current–voltage (I-V) characteristics. Such VR variability can be used as a quantum fingerprint which can provide robust security and hence can be used to deliver Physical Unclonable Functions (PUFs).

Analysis of Thermal and Roughness Effects on the Turbulent Characteristics of Experimentally Simulated Boundary Layers in a Wind Tunnel.

The aim of this paper is to analyse the thermal effects in a wind tunnel experiment to simulate the planetary boundary layer (PBL). Experiments were performed in the wind tunnel of the Laboratory of Constructions Aerodynamics at the Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul State, Brazil. This wind tunnel is a closed return low-speed wind tunnel specifically designed for dynamic and static studies on civil construction models. As a novelty, one of the experimental sections of the wind tunnel was equipped with a metal sheet with Peltier elements coupled to it. In other words, thermal effects generating new flow patterns become feasible and open pathways to compare wind tunnel simulations to those in the PBL. Furthermore, measurements obtained with the smooth floor of the wind tunnel were repeated under the same conditions with the addition of the roughness in the floor, and the mechanical turbulence generated by the surface roughness significantly amplified the exchange of momentum and heat between the regions located in vertical direction of the wind tunnel boundary layer. In the presence of turbulent heat flux near the surface, thermal effects contribute to the increase of the turbulence intensity. Turbulent energy spectra for flow velocities and different heights were obtained using the Hilbert–Huang transform method, and the observed convective turbulence energy spectra behavior reproduced those measured in an unstable surface PBL.

Fluid–Structure Interaction Modeling of Flowfields Within Kevlar-Walled Wind Tunnels

A detailed three-dimensional (3D) two-way coupled fluid–structure interaction simulation of a hybrid anechoic wind tunnel (HAWT) test section is presented with modeling all important effects, namely, turbulence, Kevlar wall porosity, and deflection. The complete 3D flowfield around a 3-ft chord NACA0012 placed into a HAWT test section is assessed. The Kevlar deflections are captured using finite element analysis, whereas 3D Reynolds-averaged Navier–Stokes computational fluid dynamics simulations are used to resolve the flowfield. Source terms are used to model the transpiration flow across the pores of the Kevlar fabric. Results are validated against an extensive experimental dataset. Aerodynamic properties of the airfoil are validated using airfoil pressure coefficients, airfoil wake pressure coefficients, and lift and drag coefficients. Boundary effects are validated against Kevlar wall pressure coefficients, Kevlar displacement, and transpiration velocity through the Kevlar fabric. Overall, a good agreement has been found among all comparisons presented. While some minor discrepancies were observed, these primarily stem from geometrical irregularities of the model and wind tunnel unresolved in the computational fluid dynamics. Overall, the fluid–structure interaction model now enables a detailed assessment of HAWTs to enhance their performance and can support experimental testing.

An integrated UAV photogrammetry-discrete element investigation of jointed Triassic sandstone near Sydney, Australia

Over the last decade, UAV Structure-from-Motion photogrammetry and digital rock mass mapping tools have been rapidly adopted into geotechnical engineering practice. As computing power has increased, numerical models and remote sensing methods have become more sophisticated, and much research has been applied to the development of digital rock mass classification and data collection methods. This investigation presents a case study of UAV photogrammetry mapping, discrete fracture network analysis and discrete element method modelling of jointed sandstone exposed in coastal cliffs and wave-cut platforms near Sydney, Australia. The aim of the study is to investigate a selection of digital mapping and numerical modelling approaches for rock mass geomechanical characterisation. A cohesive workflow is presented for UAV photogrammetry survey, discontinuity mapping, simulation of rock mass scale laboratory tests, and 3D DFN simulations of roof reinforcement in a large-span road tunnel.Digital discontinuity mapping is undertaken using two different software tools, and results are compared with historical conventional mapping. A novel GIS-based workflow is demonstrated to interrogate the mapping data, using a cellular grid approach to measure fracture intensity and fracture network connectivity. The discontinuity statistics are used as inputs to a series of 3D discrete element method numerical UCS, triaxial, and biaxial load tests that investigate the rock mass anisotropy and the impact of confining stress on rock mass shear strength, stiffness, and failure mechanisms. Next, the mapping data are applied to DFN simulations of a 31 m span tunnel, based on upcoming proposed road tunnels in Sydney. The tunnel simulations show how predicted displacements in the tunnel roof are proportional to fracture intensity.

Study on Progressive Failure of Hard Rock Tunnel After Excavation Under High Stress

The analysis and simulation of brittle failure of hard rock tunnels under high stress is essential for understanding and mastering the brittle failure characteristics of rock masses and for analyzing and regulating the stability of surrounding rocks in underground projects. The rupture and deformation of hard brittle basalt in the dam site area is one of the key problems faced by Baihetan Hydropower Station. In the paper, the spalling characteristics of the surrounding rock on the right bank of the exploratory tunnel are summarized. CDEM (continuum‐based discrete element method) is used to carry out the numerical simulation and the fracture energy model considering cohesive force weakening and friction angle strengthening is adopted. The indoor test simulations are conducted first to verify the effectiveness of the model. Then the simulation of the right bank exploratory tunnel is conducted to study the brittle failure of the surrounding rock. The results are compared with the field exposure, and the stress and displacement of characteristic points of the surrounding rock are analyzed. The numerical results are in good agreement with the damage situation in the field and reflect the brittle failure characteristics of basalt under high‐stress conditions, which helps to reasonably grasp the damage situation of the surrounding rock and take corresponding support measures, and also proves the superiority of CDEM method in solving hard rock fracture, providing a technical reference for similar hard rock brittle failure problems in engineering.

流れ場統合飛行制御の風洞実証のための動的支持装置の製作およびシミュレーション

The authors have been developed a flow-field integrated adaptive control system, which use in-flight surface pressure fields for real-time flight control. A simple mechanism for dynamic wind tunnel experiments is designed to run design and evaluation cycle for flow-field-integrated flight control. This system is not a tethered system using wires, but a yaw-rotatable seesaw system in which a lightweight aircraft model is supported from the lower fuselage at the center of gravity position. In this paper, we first explain the mechanism of the dynamic support system. The equations of motion of the model airplane on the support system are then derived, and the accuracy of the model is verified by comparing the motion quantities by simulation experiments and wind tunnel experiments. Once the validity of the simulation model is verified, the control law can be brushed up by repeating the design and verification cycle that goes back and forth between control law design by simulation and demonstration in the wind tunnel.

Experimental study on aerosol dry deposition characteristics in wind tunnel simulation

The radioactive aerosols are produced during the operation of nuclear power plants will cause certain harm to human body. Dry deposition is one of the important factors affecting the aerosols deposition to the ground, and radioactive aerosols and common aerosols have similar properties in terms of dry deposition. Based on the similarity theory, with the help of the newly built environmental wind tunnel of the China Institute for Radiation Protection, with a part of a nuclear power plant site as a research object, and the wind tunnel simulation experiment of aerosol dry deposition characteristics was carried out in groups. The particle dynamic analyzer (PDA) was used to measure and calculate the dry deposition velocity of aerosol particles, and the results are grouped, analyzed and discussed. The research results show that when the variables are controlled, when the underlying surfaces are the same, compared with aerosol particles with particle sizes of 0-2 μm and 2-5 μm, the dry deposition velocity of aerosol particles greater than 5 μm is more likely to change with the increase of wind speed.

Method for shield tunnel cross-section curve reconstruction based on FBG sensors and neural network

To improve the accuracy of reconstructing morphology in shield tunnel monitoring by fiber-optic Bragg grating (FBG) sensors, a Transformer network-based optimized tunnel cross-sectional curve reconstruction method is proposed to solve the problem of low reconstruction accuracy due to the cumulative error of discrete curvature points. In this research, the optimization method uses all interpolation points as initial points to minimize the cumulative error in fitting the curve with discrete curvature points. Simulation model experiments of the shield tunnel were carried out to verify the accuracy of the optimization method in reconstructing the tunnel section curve. The results show that the shield tunnel simulation model experiments, more accurate tunnel section reconstruction curves were obtained using this optimization method, increasing reconstruction accuracy by 27.3424%.

Analyzing the Application of Void Decks on High-rise Affordable Housing in Jakarta, Indonesia, to Achieve Optimal Urban Ventilation

Economic growth in ASEAN countries encourages significant urbanized growth. In line with the growth of urbanization, large swathes of residential buildings have been constructed in urban areas, especially, in the case of Indonesia, through the government's 1000 rusun (high-rise affordable housing) development program in Jakarta. In order to reduce energy consumption and create a sustainable rusun, a passive strategy is needed in the form of natural air conditioning through optimized natural ventilation in these buildings. In this study, testing was conducted on Rusun Rorotan in Jakarta, from two wind source directions (north and northwest) with five void decks configuration samples each, in order to determine wind flow and wind speed patterns in the Rusun area. For this purpose, the wind tunnel simulation method using the Butterfly plugin in Grasshopper was employed. These results should provide a reference for future residential property developers, especially in the scope of other countries in ASEAN, which have similar climatic conditions to that of Indonesia.

Lifting of Tribocharged Grains by Martian Winds

Abstract It is a long-standing open question whether electrification of wind-blown sand due to tribocharging—the generation of electric charges on the surface of sand grains by particle–particle collisions—could affect rates of sand transport occurrence on Mars substantially. While previous wind tunnel experiments and numerical simulations addressed how particle trajectories may be affected by external electric fields, the effect of sand electrification remains uncertain. Here we show, by means of wind tunnel simulations under air pressure of 20 mbar, that the presence of electric charges on the particle surface can reduce the minimal threshold wind shear velocity for the initiation of sand transport, u *ft, significantly. In our experiments, we considered different samples, a model system of glass beads as well as a Martian soil analog, and different scenarios of triboelectrification. Furthermore, we present a model to explain the values of u *ft obtained in the wind tunnel that is based on inhomogeneously distributed surface charges. Our results imply that particle transport that subsides, once the wind shear velocity has fallen below the threshold for sustained transport, can more easily be restarted on Mars than previously thought.

Application of the Modified Mohr–Coulomb Yield Criterion in Seismic Numerical Simulation of Tunnels

To solve the classical problem that the Mohr–Coulomb yield criterion overestimates the tensile properties of geotechnical materials, a modified Mohr–Coulomb yield criterion that includes both maximum tensile stress theory and smooth processing was established herein. The modified Mohr–Coulomb constitutive model is developed using the user-defined material subroutine (UMAT) available in finite element software ABAQUS, and the modified Mohr–Coulomb yield criterion is applied to construct a numerical simulation of a shaking table model test. Compared with the measured data from the shaking table test, the accuracies of the classical Mohr–Coulomb yield criterion and the modified Mohr–Coulomb yield criterion are assessed. Compared to the shaking table test, the classical Mohr–Coulomb model has a relatively large average error (−6.98% in peak acceleration values, −8.47% in displacement values, −23.93% in axial forces), while the modified Mohr–Coulomb model has a smaller average error (+2.71% in peak accelerations value, +3.19% in displacements value, +7.56% in axial forces). The results of numerical simulation using the modified Mohr–Coulomb yield criterion are closer to the measured data.

Edge Cooling of a Fuel Cell during Aerial Missions by Ambient Air.

During aerial missions of fuel-cell (FC) powered drones, the option of FC edge cooling may improve FC performance and durability. Here we describe an edge cooling approach for fixed-wing FC-powered drones by removing FC heat using the ambient air during flight. A set of experiments in a wind tunnel and numerical simulations were performed to examine the efficiency of FC edge cooling at various flight altitudes and cruise speeds. The experiments were used to validate the numerical model and prove the feasibility of the proposed method. The first simulation duplicated the geometry of the experimental setup and boundary conditions. The calculated temperatures of the stack were in good agreement with those of the experiments (within ±2 °C error). After validation, numerical models of a drone’s fuselage in ambient air with different radiator locations and at different flight speeds (10–30 m/s) and altitudes (up to 5 km) were examined. It was concluded that onboard FC edge cooling by ambient air may be applicable for velocities higher than 10 m/s. Despite the low pressure, density, and Cp of air at high altitudes, heat removal is significantly increased with altitude at all power and velocity conditions due to lower air temperature.

Extended Study of Full-Scale Wind Tunnel Test and Simulation Analysis Based on DrivAer Model

There is a great demand for car model series that can meet the needs of today’s research about vehicle aerodynamics due to the limitations of models used in the past. This paper focuses on the introduction of the extension of DrivAer model and discussions about the model’s experimental and simulation results. On the basis of DrivAer model, the upgrade and innovation of pickup styling back and concept of perception testing are added. Specifically, the SUV back and the Pickup back are redesigned in combination with Chinese aerodynamic design trend. The experiments were performed in a full-scale aero-acoustic wind tunnel with ground simulation system, consisting of boundary layer control system and five-belt system. Base on the wind tunnel experimental results, it can be found that the ground simulation has obviously influence on the drag coefficient, but has no influence on the distribution of surface pressure in upper body. The close state of the grilles, the absence of mirrors, and the fully enclosed of rims can significantly reduce the drag coefficient. Digital wind tunnel (DWT) simulation and open road (OR) simulation have been completed and verified with experimental results. It can be concluded that DWT simulation with the same geometry as the real wind tunnel performs better than the OR simulation. The maximum difference between the experimental results and the DWT simulation results does not exceed 2% and DWT simulation also performs well in the surface pressure simulation.

An Analysis of the Femoral Drilling Angle to Avoid Tunnel Collision during Double-Bundle Anterior Cruciate Ligament and Anterolateral Ligament Reconstruction on the Knee.

Concomitant anterior cruciate ligament (ACL) and anterolateral ligament (ALL) reconstruction has been reported as an effective technique for providing rotational control of the knee. However, the intraoperative risk of collision with an ACL tunnel during the drilling for the femoral ALL tunnel has been described. The purpose of this study was to investigate the various femoral drilling procedures to avoid tunnel collisions during combined double-bundle ACL and ALL reconstruction. Nine cadaveric knees were used in this study. ACL drilling was performed through the anteromedial portal to footprints of the posterolateral bundle at 120° (PL120) and 135° (PL135) knee flexion and the anteromedial bundle at 120° (AM120) and 135° (AM135) knee flexion. ALL drilling was performed at 0° (Cor0-ALL) and 30° (Cor30-ALL) coronal angles using a Kirschner wire (K-wire). The distance between the ALL footprint and ACL K-wire outlets, axial angles of ALL K-wires colliding with ACL K-wires, and distances from the ALL footprint to the collision point were measured. From these values, the safe zone, defined as the range of axial angles in which no collisions or penetrations occurred, was identified by simulation of tunnels utilized for reconstruction grafts in each drilling procedure. The point-to-point distance from the ALL footprint to the K-wire outlet was significantly greater in the AM120 than the AM135 (13.5 ± 3.1, 10.8 ± 3.2 mm; p = 0.048) and in the PL135 than the PL120 (18.3 ± 5.5, 16.1 ± 6.5 mm; p = 0.005) conditions, respectively. During an ACL drilling combination of PL135/AM120, a safe zone of > 45° in Cor30-ALL was identified. With a narrow safe zone during the PL135/AM120 combination only, the risk of femoral tunnel collisions in combined double-bundle ACL and ALL reconstruction is high. AM drilling at 120° and PL drilling at > 135° knee flexion, combined with ALL drilling at 30° coronal angle and > 45° axial angle, may reduce this risk.

Numerical Simulation of Continuous Shield Tunneling based on a Dynamic Element-Deletion Technology

Currently, the finite-element (FE) simulation of tunnel excavation usually adopts the birth-to-death approach, which directly removes the soil element in the excavation region. This approach simplifies the dynamic process of continuous excavation to a transient process, which ignores the time-dependent response of soils in front of the excavation face as well as the soil– cutterhead interaction. This study presents a novel FE method to simulate the dynamic and continuous shield-tunneling process. In this method, the state variables are calculated based on either the stress or strain tensor of any arbitrary elements in which the elements that extrude into the excavation chamber can be identified and eliminated using the element-deletion technology. Therefore, the dynamic and continuous excavation process of a shield machine can be accurately simulated. Furthermore, the method can be used to analyze the influence of the cutterhead geometrical parameters as well as its rotary and propulsion speeds on the stability of the excavation face. By analyzing the key construction parameters such as shield-tunneling speed, cutterhead speed, and slurry pressure, the superiority of the dynamic simulation is demonstrated.

A new evaluation index of rockburst tendency considering tunnel excavation and fracture distribution

Rockburst risk and tendency analysis of fractured rock mass after excavation and unloading has been gaining importance. Within the framework of a constitutive model based on internal variable thermodynamics, the energy dissipation rate is proposed as a new evaluation index of rockburst tendency. Taking the numerical simulation of a traffic tunnel in western China as an example to carry out the rockburst tendency analysis, the models with parallel fractures of different dip angles were established in FLAC3D by Monte-Carlo method and MATLAB programming. Combined with the estimated in-situ stress of the deep-buried tunnel and the inversion results of constitutive parameters of rock mass, the influence of fracture dip angles on rockburst tendency of the surrounding rock is analyzed. The analysis results under different calculation conditions show that with the increase of fracture dip angle, the possible location of rockburst gradually transfers from the vault to the left arch waist. In addition, the comparison with the stress index verifies that the energy dissipation rate index can effectively evaluate the potential dangerous areas and rockburst positions after excavation and unloading of fractured rock mass, which has a reference value for the rockburst risk assessment in deep-buried tunnels.

Study on the mechanism of the vortex-induced vibration ofa bluff double-side box section

At present, researchers mainly focused on the vortex-induced vibration (VIV) of the double-side I-shaped girder, while there are only a few literatures focused on the VIV of the bluff double-side box girder, especially the study on the synchronous pressure- and vibration- measured test for the bluff double-side box girder has not been reported. Therefore, in this study, the vibration-measured test, the Numerical Wind Tunnel Simulation, and the synchronous pressure- and vibration- measured test were conducted to study the VIV mechanism of the bluff double-side box girder. Firstly, a section model of the bluff double-side box girder was designed, and the vibration-measured test was conducted to study the influence of mass ratio, damping ratio, and aerodynamic countermeasures on the VIV of the bluff double-side box girder. Secondly, the Numerical Wind Tunnel Simulation was conducted to simulate the vorticity evolution of the bluff double-side box girder, which was used to help analyze the results of the synchronous pressure- and vibration- measured test. Finally, the synchronous pressure- and vibration- measured test was conducted to investigate the wind pressure distribution and aerodynamic forces on the surface of the double-side box girder, which was then used to study the VIV mechanism of the bluff double-side box girder by combining the simulated vorticity evolutions. So, when the VIV of the double-side box girder occurs, it is found that: there is a significant difference in the mean and fluctuating wind pressure between the upper and lower surfaces; moreover, at the leading and trailing edges, the aerodynamic forces contribute greatly to the VIV, the correlation between the aerodynamic forces and the vortex-induced aerodynamic forces is positive, and with the increase of this coefficient, it will lead to the more significant VIV.

Tension vector and structure matrix associated force sensitivity of a 6-DOF cable-driven parallel robot

This paper investigates the force sensitivity of 6-DOF cable-driven parallel robots (CDPRs) in order to propose a better force measurement device. Kinematics and dynamics for a CDPR of n-DOF are deduced and formulated, and algorithms for calculating the cable tension are developed. Then, by defining geometrical parameters related to the dimensions and configurations of the CDPRs, optimal methods for determining force sensitivity with respect to the structure matrix and twist vector of the 6-DOF CDPRs with two different moving platforms (i.e. a cubic-shaped, and a flat moving platform) are proposed. By using numerical examples integrated with external twists obtained from wind tunnel tests, simulations and analysis for the two type of 6-DOF CDPRs are carried out. The simulation results help identify the optimal dimensions that can be used to design 6-DOF-CDPR-based force measuring devices with high force sensitivity. Experiment validation is also conducted to verify the method proposed in this paper.

Structural Dynamic Response of a Shield Tunnel under Aircraft Taxiing Load

Dynamic load is an important factor affecting the safety and stability of subway tunnel structures. To obtain the variation law of shield tunnel structure dynamic response under aircraft taxiing load, a three-dimensional numerical simulation of such tunnel under the action of aircraft taxiing load is performed on the basis of a project involving a shield tunnel orthogonal underpass taxiway. The effects of sliding speed and tunnel depth on the structure of the shield tunnel are also analyzed. The results show that the transverse displacement and acceleration response of tunnel segment exhibit evident time-space effect under the action of aircraft taxiing load. The transverse displacement and arch waist acceleration of the shield segment increase first and then decrease. The transverse displacement of the arch waist reaches its maximum when the aircraft taxis directly above the tunnel. The sliding speed exhibits an evident influence on the dynamic response of shield tunnel structure. The vertical and convergence displacements of tunnel segments increase with the increase in sliding speed. The dynamic response of tunnel structure is significantly affected by the factors of tunnel buried depth. The vertical and convergence displacements of tunnel segments decrease with the increase in tunnel buried depth. Therefore, the safety of the shield tunnel structure can be ensured by controlling the taxiing speed when the aircraft taxis directly above the tunnel. The measures of increasing the buried depth of the tunnel or strengthening the tunnel structure need to be considered when the taxiing speed is large.

A research on dust suppression mechanism and application technology in mining and loading process of burnt rock open pit coal mines

ABSTRACT In order to solve the serious dust pollution problem in mining and loading process of burnt rock open-pit coal mines, a dust suppression technology was proposed to investigate the compound dust suppressant with four functions of wetting, coagulation, moisture absorption, and moisture retention, and improve the hydrophilicity and dust suppression efficiency of burnt rock. Through single-factor experiments, four functional reagents were selected. Determined the best mass concentration ratio by orthogonal test, and the optimum dilution ratio was determined through the contact angle verification test. Fourier infrared spectroscopy (FTIR) analysis of the functional group of the compound dust suppressant showed that the hydrophilic functional group was increased. The scanning electron microscopy (SEM) revealed that the dust surface formed a dense film after spraying the dust suppressant, and the effect of fine dust coagulation was obvious. The results of the wind tunnel simulation test revealed that the inhibitory efficiency of the compound dust suppressant on total dust and respirable dust could reach up to 81.90% and 87.06%, respectively, under a wind speed of 4.00 m/s. The field test data for mining and loading spray dust suppression in open-pit coal mines revealed that the dust suppression efficiency of whole dust and respirable dust was greater than 85.70%, which indicates that the compound dust suppressant can effectively suppress the dust of burnt rock, and effectively improve the working environment quality of mining and loading in open-pit coal mines. Implications: Open-pit coal mines located in arid areas will produce a large amount of dust during the mining and loading process, which will cause serious air pollution. In particular, the burnt rock is highly hydrophobic, and it is difficult to achieve effective removal by water spraying. The open-pit coal mine face advances faster and has strong mobility, There are few researches on dust reduction in this link. Therefore, in this study, in order to improve the dust suppression efficiency in the mining and loading process, a compound dust suppressant to improve the hydrophilicity of the burnt rock was developed through single-factor experiments and orthogonal experiments. Microscopic analysis using FTIR and SEM confirmed the wetting and coagulation effect of the dust suppressant. Then designed a spray dust suppression program for the mining and loading process and achieved good results.