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The Einstein Telescope will be a gravitational wave observatory comprising six nested detectors, three optimized to collect low-frequency signals, and three for high frequency. It will be built a few hundred meters under Earth’s surface to reduce direct seismic and Newtonian noise. A critical issue with the Einstein Telescope design are the three corner stations, each hosting at least one sensitive component of all six detectors in the same hall. Maintenance, commissioning, and upgrade activities on a detector will cause interruptions of the operation of the other five, in some cases for years, thus greatly reducing the Einstein Telescope observational duty cycle. This paper proposes a new topology that moves the recombination and input–output optics of the Michelson interferometers, the top stages of the seismic attenuation chains and noise-inducing equipment in separate excavations far from the tunnels where the test masses reside. This separation takes advantage of the shielding properties of the rock mass to allow continuing detection with most detectors even during maintenance and upgrade of others. This configuration drastically improves the observatory’s event detection efficiency. In addition, distributing the seismic attenuation chain components over multiple tunnel levels allows the use of effectively arbitrarily long seismic attenuation chains that relegate the seismic noise at frequencies farther from the present low-frequency noise budget, thus keeping the door open for future upgrades. Mechanical crowding around the test masses is eliminated allowing the use of smaller vacuum tanks and reduced cross section of excavations, which require less support measures.

Contemporary life streams, more often than ever, impose the necessity for construction of new underground structures in the vicinity of existing tunnels, with an aim to accommodate transportation systems and utility networks. A previously uninvestigated case, in which a newly-constructed tunnel opening is closely positioned behind an existing tunnel, referred to as the tunnel–cavity configuration, has been considered in this study. An exact analytical solution is derived considering a pair of parallel circular cylindrical structures of infinite length, with the horizontal alignment, embedded in a boundless homogeneous, isotropic, elastic medium and excited by time-harmonic plane SV-waves under the plane-strain conditions. The Helmholtz decomposition theorem, the wave functions expansion method, the translational addition theorem for bi-cylindrical coordinates, and the pertinent boundary conditions are jointly employed in order to develop a closed-form solution of the corresponding boundary value problem. The primary goal of the present study is to examine the increase in dynamic stresses at an existing tunnel structure due to the presence of a closely driven unlined cavity, as well as in a localized region around the tunnel (at the position of the cavity in close proximity), under incident SV-waves. A new quantity called dynamic stress alteration factor is introduced and the aspect of the minimum seismically safe distance between the two structures is particularly considered.

Taking inspiration from dragonfly tandem wing aerodynamics, this study explores a novel wind turbine design featuring tandem blades. A 1‐m diameter horizontal axis wind turbine is tested in a wind tunnel at wind speeds between 4 and 12 m/s. In addition, computational fluid dynamics simulations validated with the experimental data further investigated the bioinspired configuration, also with the aid of flow visualization, and compared it to two conventional turbines designed from each blade of the bioinspired tandem blade configuration ensuring an equal solidity ratio for the three rotors. The results showed significant advantages for the tandem configuration at low tip speed ratios (TSRs) with an increase of up to 31% in torque generation compared to the sum of the individual blades, with no penalties at high TSRs. This improvement is attributed to the fore‐blade/hind‐blade interaction, with flow visualization showing a significant aerodynamic performance change with respect to the performance of the isolated individual blades at all TSRs. The presence of the hind blade significantly augments the performance of the fore blade by lowering the flow stagnation point, thus increasing the flow curvature, and also promoting better attachment by sucking the flow downward. Although the hind blade itself suffers from the fore‐blade wake, the tandem configuration showcased an overall enhancement in performance.

The burgeoning development of railway construction in plateau regions of southwest China necessitates innovative and environmentally sustainable approaches, particularly in the realm of tunnel construction, where the transfer of muck poses significant operational and environmental challenges. This research, pivoting around the application and configuration of electric muck transfer equipment in plateau railway tunnels, seeks to dissect the potentialities and impediments of transitioning from conventional diesel-powered machinery to electric alternatives, with a spotlight on mitigating environmental impacts and enhancing operational efficiency. Through an analytical lens, the study employs a case study methodology, leveraging data and insights from existing electric equipment models and their applications, provided by major manufacturers in China, to weave a comprehensive narrative around the practicalities, specifications, and challenges embedded in the adoption of electric machinery in plateau environments. The findings unveil a nuanced landscape, where the environmental and operational advantages of electric equipment are juxtaposed against a backdrop of technological, financial, and infrastructural hurdles, thereby crafting a complex tapestry of opportunities and challenges. The research further extrapolates policy recommendations and practical guidelines, advocating for a harmonized amalgamation of governmental policies, technological advancements, and strategic planning to navigate through the identified challenges and optimize the integration of electric equipment in tunnel construction practices. Envisaging future research pathways, the study underscores the criticality of perpetuating technological innovations, policy adaptations, and interdisciplinary research to further refine and enhance the application of electric muck transfer equipment in plateau railway tunnel projects, thereby contributing to the broader narrative of sustainable construction practices in challenging terrains.

This paper presents an eight wire-driven parallel robot (WDPR-8) designed to serve as a suspension manipulator for aircraft models during wind tunnel testing. The precision of these tests is significantly influenced by the system’s stability and workspace, both of which are shaped by the geometric configuration of the structure and the tension in the wires. To acquire the efficiency principle of the suspension scheme design for the model, a kinematics model for a WDPR-8 was established. Based on the kinematics model, the stiffness of a WDPR-8 was theoretically studied, and the analytical expression of stiffness matrix of a WDPR was deduced. The stiffness matrix was composed of two terms, one of which is determined by the configuration of suspension system and the other term is determined by the wire tension. Based on the analysis result, a set of suspension scheme was discussed under the calculation of stiffness matrix and workspace analysis. In the discussion process, in addition to the stiffness-maximum calculation, another criterion as force closure is presented, which is useful for increasing the stiffness and workspace of the robot. Finally, a prototype was established according to the analysis result, and the workspace experiments are conducted. Test results indicate that the workspace meets the design requirements, validating the system suspension design method of a WDPR for aircraft model suspension in wind tunnel test considering of the systematic stiffness and workspace.

This paper analyses the multi-objective design requirements of UAV with high timeliness, high manoeuvrability and long-endurance long-range flight capability. Then put forward an aerodynamic configuration conception of wide flight envelope that can perform multi-tasks, such as fast approach, long endurance patrol and critical maneuvering. By means of wind tunnel test, the aerodynamic characteristics regularities of this configuration changed by shape parameters, component combination and spatial relationships are studied. Base on analysing the flow coupling efficiency of canard vortex and wing vortex, proposed the principle of relative position matching between canard and wing. The results show that when the canard was higher than the wing, the canard vortex provided additional vortex lift on the upper surface of the wing, which could provide a favorable influence in the cruise phase. Further more, using the trapped vortex of variable curvature lip on nose which was similar to the influence mechanism of canard vortex, a stable favorable interference vortex system in a wide envelope could be obtained, and the components and controlling complexity of this aircraft configuration would be simplified.

Vertical‐axis wind turbines (VAWTs) operate in the atmospheric boundary layer and are frequently subjected to turbulent flow. The objective of this study is to investigate the effect of free‐stream turbulence on the power performance and wake characteristics of a pair of counter‐rotating VAWTs. The research was conducted using wind tunnel experiments, which involved testing an isolated VAWT and two configurations of paired VAWTs with different rotational direction combinations. The experiments were conducted under two different turbulence intensities, 0.39% and 6.7%, with the latter being achieved by placing a passive wooden grid in the wind tunnel. The mechanical power output of the turbines was measured through torque and angular speed sensors, and the wake up to six rotor diameters downstream of paired VAWTs was characterised using constant temperature anemometry. The results show that when the turbulence intensity increases, the power coefficient of the isolated VAWT increases by 11%, while paired VAWTs experience an increase of up to 15%. Additionally, it is shown that the impact of increased free‐stream turbulence on the evolution and recovery of the wake is minimal, leading to only a slight reduction in the velocity deficit.

  A blended wing body (BWB) configuration is an unconventional aircraft design in which the wing and fuselage are blended to form an aircraft. This design concept has inherent higher aerodynamic efficiency, environmental benefits and capacities. These advantages make the BWB configuration a feasible concept for commercial transport aircraft. In the present work, a 3-D BWB model is designed in SolidWorks and fabricated using a 3D printer. The numerical and experimental analyses are carried out with this BWB geometry. Aerodynamic characteristics and flow features obtained from the open-source CFD software OpenFOAM have been studied, analyzed, and compared with the wind tunnel results. Experimental and computational data compare well and the present BWB can operate at a high angle of attack. The coefficient of lift (CL) increases with AoA up to 45º. The CL starts decreasing beyond this AoA, and the present BWB geometry stalls at around AoA = 45º. The coefficient of drag (CD) increases with the increase in AoA due to the spreading of the separated region over the geometry. Lift/Drag (L/D) variation with AoA is also studied to find the optimum flight configuration of the present BWB geometry. Sectional pressure distribution at different spanwise locations, velocity contours, pathlines, surface limiting streamlines and tuft flow visualization are also presented to investigate the flow. The studies investigate the aerodynamics, flow field and optimal flight configuration for cruising a BWB geometry.

Due to global warming concerns, the Aviation industry is trying to reduce its carbon footprint. Electric propulsion (EP) is one way of doing this, where the power is obtained from electrical sources. The concept of distributed electric propulsion (DEP) is in the focus now. NASA’s X-57 Maxwell, a high winged, all-electric experimental aircraft, uses this concept. The present work aims at developing a CFD model (ANSYS Fluent) to evaluate aerodynamic performance of two configurations of NASA’s X-57 aircraft wing; (i) wing and nacelle (clean wing) and (ii) wing, nacelle and one electric propeller under cruise condition; and compare it with the results of wind tunnel experiment performed by NASA/Armstrong X-57 research program. Parameters like lift, drag and pressure coefficients (CL, CD, CP) are compared for both cases. A good match is observed for CL, CD and CP, thus validating the model. The unsteady RANS solver is very efficient in capturing the effects of propeller slipstream on the wing. After validation, this model is further used to simulate aerodynamic performance of a wing with multi-propeller (DEP) configuration.

Perpendicularly magnetized synthetic antiferromagnets (SAF), possessing low net magnetization and high thermal stability as well as easy reading and writing characteristics, have been intensively explored to replace the ferromagnetic free layers of magnetic tunnel junctions as the kernel of spintronic devices. So far, utilizing spin-orbit torque (SOT) to realize deterministic switching of perpendicular SAF have been reported while a large external magnetic field is typically needed to break the symmetry, making it impractical for applications. Here, combining theoretic analysis and experimental results, we report that the effective modulation of Dzyaloshinskii-Moriya interaction by the interfacial crystallinity between ferromagnets and adjacent heavy metals plays an important role in domain wall configurations. By adjusting the domain wall configuration between Bloch type and Néel type, we successfully demonstrate the field-free SOT-induced magnetization switching in [Co/Pd]/Ru/[Co/Pd] SAF devices constructed with a simple wedged structure. Our work provides a practical route for utilization of perpendicularly SAF in SOT devices and paves the way for magnetic memory devices with high density, low stray field, and low power consumption. Synthetic antiferromagnets (SAF), formed out of alternating layers of a ferromagnet with neutral spacer combine technologically appealing properties of both antiferromagnets and ferromagnets. Here, Chen et al demonstrate controlled switching of an SAF, without the need for an applied magnetic field.