Speed-up Effect Research Articles

A coupled smoothed particle hydrodynamics–peridynamics model for two-dimensional hydroelastic water entry

In this paper, a numerical model coupling the smoothed particle hydrodynamics (SPH) with peridynamics (PD) is developed to solve the problem of the hydroelastic water entry. By combining the geometric nonlinear peridynamics with the weakly compressible SPH, the proposed model can efficiently simulate the nonlinear deformation of the structure and the deformation of a fluid free surface. The transmission of information between the fluid and solid phases is implemented by a dummy particle boundary treatment method. By simulating benchmark tests, the ability of the proposed model to solve nonlinear fluid–structure coupling problems is verified. In order to improve the computational efficiency, the graphics processing unit parallel acceleration scheme is applied to the SPH-PD model. Compared with the serial scheme, the speedup effect of the parallel scheme in large-scale computation is verified. As an application of the numerical model, the water entry of the flexible panel at a constant entry velocity is studied. The mechanism of hydroelastic effect is explained by analyzing the variations in the fluid pressure field, slamming force, and panel deformation during water entry. In addition, the influences of plate rigidity, impact velocity, and deadrise angle on the hydroelastic effect are investigated.

Quantum speedup and non-Markovianity of an atom in structured reservoirs: pseudomodes as a good description of environmental memory

Following the recent paper (Teittinen et al 2019 New J. Phys. 21 123041), one can see that in general there is no simple relation between non-Markovianity and quantum speed limit. Here, we investigate the connection between quantum speed limit time and non-Markovianity of an atom in structured environments (reservoirs) whose dynamics is governed by an exact pseudomode master equation (Garraway 1997 Phys. Rev. A 55 2290). In particular, we find an inverse relation between them, which means that the non-Markovian feature of the quantum process leads to speedup of evolution. Thus, there is a link between quantum speedup and memory effects for specific cases of dynamical evolution. Our results might shed light on the relationship between the speedup of quantum evolution and the backflow of information from the environment to the system.

Mathematical Analysis of the Wind Field Characteristics at a Towering Peak Protruding out of a Steep Mountainside

Wind field characteristics in a complex topography are significantly influenced by the nature of the surrounding terrains. This study employs onsite measurements to investigate the wind field characteristics at a towering peak protruding out of a steep mountainside, where butterfly−lookalike landscape platform will be constructed; the impact of the surrounding topography on the wind flow is highlighted. The results showed that the blocking effect of the mountains in the mountainous side of the valley caused a significant drop in the mean wind speed from that direction. The stationary test (reverse arrangement test) indicated that the wind speed had a strong nonstationary characteristic, necessitating the employment of a steady and nonstationary wind speed model to assess the wind turbulence characteristics. The three directions’ wind turbulence integral scales were critically influenced by the occurrence of the wind speedup effect, unexpectedly resulting in the vertical turbulence integral scale being the greatest of the three. Furthermore, the measured wind turbulence properties under both wind speed models showed certain variations from the recommended specifications. Consequently, the impact of the local terrain and the speedup effect on the wind characteristics must be thoroughly evaluated to ensure the structural stability of structures installed at a similar topography.

Judgment criteria for significant wind speed-up regions in natural complex terrain

Flashover incidents due to wind-induced motion of overhead power line components are a not uncommon phenomenon during very strong winds, e.g. typhoons, and an important contributing factor is the speed-up effect caused by small-scale topographic features. In this study, wind speed-up ratios and significant speed-up regions in natural complex terrain are comprehensively analyzed from three perspectives: analysis of landform characteristics of flashover locations, Computational Fluid Dynamics (CFD) simulation, and wind tunnel experiments. Through the analysis of flashover locations, judgment criteria based on the elevation coefficient of variation are proposed to attempt to identify significant speed-up regions in natural complex terrain. Wind tunnel experiments and CFD simulations are conducted to analyze the wind speed-up ratios in 12 wind directions for both a small isolated mountainous area and a large continuous mountainous area. The significant speed-up regions are determined by consolidating the speed-up ratios from all 12 wind directions. The reliability of the judgment criteria is then validated. The results confirm that significant speed-up ratios are predominantly concentrated at the edges of mountainous areas, particularly at peaks and high ridges around areas with larger elevation coefficient of variation. These regions largely coincide with the locations where flashover incidents mainly occurred and the results from wind tunnel experiments and CFD simulations. In summary, the clearly identified significant speed-up regions include (1) small isolated mountainous areas; (2) peaks and high ridges around areas with larger elevation coefficient of variation within large continuous mountainous areas, and the higher crests within these regions. Based on these findings, the study suggests that wind speed-up ratios in design standards should be amplified in the vicinity of these regions to enhance safety measures.

An efficient online successive reanalysis method for dynamic topology optimization

In this study, an efficient reanalysis strategy for dynamic topology optimization is proposed. Compared with other related studies, an online successive dynamic reanalysis method and a Proper Orthogonal Decomposition (POD)-based approximate dynamic displacement strategy are integrated. In the dynamic reanalysis, the storage of the stiffness matrix decomposition can be avoided, and the reduced basis vectors should be successively updated according to the structural state in each iteration. Thus, the bottleneck of the combined approximation method for large-scale dynamic topology optimization can be overcome. Sequentially, POD is applied to obtain the approximate dynamic displacement, in which the Proper Orthogonal Mode (POM) of the displacement field is applied to obtain the approximate equivalent static loads of the Equivalent Static Load (ESL) method. Compared to the exact equivalent static loads at all the time intervals, the number of equivalent static loads is significantly reduced. Finally, the 2D and 3D test results indicate that the proposed method has remarkable speed-up effect under the premise of small relative error, support the strength of the proposed strategy.

Multimodality integrated microresonators using the Moiré speedup effect.

High-Q microresonators are indispensable components of photonic integrated circuits and offer several useful operational modes. However, these modes cannot be reconfigured after fabrication because they are fixed by the resonator's physical geometry. In this work, we propose a Moiré speedup dispersion tuning method that enables a microresonator device to operate in any of three modes. Electrical tuning of Vernier coupled rings switches operating modality to Brillouin laser, bright microcomb, and dark microcomb operation on demand using the same hybrid-integrated device. Brillouin phase matching and microcomb operation across the telecom C-band is demonstrated. Likewise, by using a single-pump wavelength, the operating mode can be switched. As a result, one universal design can be applied across a range of applications. The device brings flexible mixed-mode operation to integrated photonic circuits.

Numerical Investigation of Wind Flow and Speedup Effect at a Towering Peak Extending out of a Steep Mountainside: Implications for Landscape Platforms

Wind flow over complex terrain is strongly influenced by the topographical features of the region, resulting in unpredictable local wind characteristics. This paper employs numerical simulation to study the wind flow at a towering peak extending out of a steep mountainside and the wind-induced effect on onsite landscape platforms. First, the wind flow from seven different directions is explored via 3D numerical simulations, and the wind load distribution on the platforms is highlighted. Second, a 2D numerical simulation is conducted to evaluate the wind speedup effect at the side peak, examining the influence of the side peak height and the mountainside steepness on the wind speedup factor. The numerical simulations presented in this research were validated by replicating a published numerical and experimental study. The results illustrate the amplifying and blocking effects of the surrounding topography, yielding unpredictable and nonuniform wind pressure distribution on the platforms. The presence of the side peak leads to a significant increase in the speedup factor, and the side peak height and the mountainside steepness have a moderate influence on the value of the speedup factor. Additionally, the speedup factor obtained from this study varies significantly, especially near the surface, from the recommendations of several wind load standards. Consequently, the impact of the local terrain and the wind speedup effect must be thoroughly assessed to ensure the structural integrity of structures installed at a similar topography.

A comparative study on the speed-up dynamics of drop spreading on floating and glass-supported polystyrene thin films

The enhanced spreading of a 2D drop on a stiff and free-standing elastic thin film theoretically investigated by Shanahan (Rev. Phys. Appl. 1988, 23, 1031–1037) has not been studied and verified experimentally. To shed a light on this interesting problem, herein, we perform comparison studies on the spreading behavior of a silicone oil drop on stiff polystyrene thin films supported by two different substrates: glass vs. water. Scaling analysis on the time evolution of the contact radius for the drop spreading on the films of varied thickness (∼40 nm to ∼600 nm) reveals the difference on the dynamics for the drop spreading on glass-supported and floating films. Upon fitting the spreading data by using the spreading model developed by de Ruijter et al. (Langmuir 1999, 15, 2209–2216), we are able to identify the speed-up effect for the drop spreading on water supported floating films, which progressively decreases with film thickness and diminishes when the thickness is greater than ∼200 nm. The elastic driving force that is responsible for the speed-up of the drop spreading on the floating film is evaluated empirically, which is found to decay exponentially with contact radius of the drop. The pre-factor and the decay length of the decay function are determined by film thickness and drop volume, resepctively. Our findings expect to facilitate developing new theories with practical relevance on the spreading dynamics of a liquid drop on elastic films.

New method for the transient simulation of natural gas pipeline networks based on the fracture-dimension-reduction algorithm

The transient simulation technology of natural gas pipeline networks plays an increasingly prominent role in the scheduling management of natural gas pipeline network system. The increasingly large and complex natural gas pipeline network requires more strictly on the calculation efficiency of transient simulation. To this end, this paper proposes a new method for the transient simulation of natural gas pipeline networks based on fracture-dimension-reduction algorithm. Firstly, a pipeline network model is abstracted into a station model, inter-station pipeline network model and connection node model. Secondly, the pressure at the connection node connecting the station and the inter-station pipeline network is used as the basic variable to solve the general solution of the flow rate at the connection node, reconstruct the simulation model of the inter-station pipeline network, and reduce the equation set dimension of the inter-station pipeline network model. Thirdly, the transient simulation model of the natural gas pipeline network system is constructed based on the reconstructed simulation model of the inter-station pipeline network. Finally, the calculation accuracy and efficiency of the proposed algorithm are compared and analyzed for the two working conditions of slow change of compressor speed and rapid shutdown of the compressor. And the following research results are obtained. First, the fracture-dimension-reduction algorithm has a high calculation accuracy, and the relative error of compressor outlet pressure and user pressure is less than 0.1%. Second, the calculation efficiency of the new fracture-dimension-reduction algorithm is high, and compared with the nonlinear equations solving method, the speed-up ratios under the two conditions are high up to 17.3 and 12.2 respectively. Third, the speed-up ratio of the fracture-dimension-reduction algorithm is linearly related to the equation set dimension of the transient simulation model of the pipeline network system. The larger the equation set dimension, the higher the speed-up ratio, which means the more complex the pipeline network model, the more remarkable the calculation speed-up effect. In conclusion, this new method improves the calculation speed while keeping the calculation accuracy, which is of great theoretical value and reference significance for improving the calculation efficiency of the transient simulation of complex natural gas pipeline network systems.

Investigation of hilly terrain wind characteristics considering the interference effect

Wind characteristics at complex mountainous areas are of great practical importance, which, however, has not been fully understood. The main objective of this study is to present a comprehensive assessment of hilly terrain wind characteristics using both Computational Fluid Dynamics (CFD) method and wind tunnel test. The results indicate that hilly-terrain wind characteristics exhibit pronounced site-to-site variability. The speed-up effect at mountain top and the passing terrain can be somewhat weakened by the existence of front mountain, whereas the wind speed reduction near the mountain foots is enhanced due to the shielding effect. The effect of inflow wind direction on the hilly terrain wind characteristics is also found to be evident.

On the development of a generalized atmospheric boundary layer velocity profile for offshore engineering applications considering wind–wave interaction

Within industrial standards, effects due to wind–wave interaction on the marine atmospheric boundary layer (ABL) may be included via the Charnock sea-surface roughness parameter for open-sea and near-coastal waters. This roughness parameter does not accommodate the wide variety of wave states possible, nor does it modify the ABL to include speed-up effects resulting from an undulating wave profile. In an attempt to provide an updated definition of the general ABL profile for offshore wind engineering applications, an experimental and numerical study is performed to assess the interaction of the ABL on a fixed wave geometry. By extracting the mean velocity field during the wind–wave interaction, bespoke values of the velocity profile power exponent and wind risk factor can be obtained. A range of wave heights and wave lengths are considered from which a Kriging surrogate model is trained to supply the relevant wind profile parameters depending on the wave state. These newly garnered parameters enable the practitioner to define a reference wind velocity, and then adjust the velocity profile characteristics to contain the influence of the wave. This approach provides a new inlet velocity condition that can be used within computational wind engineering investigations without the need to explicitly model the wave surface, as well as flexibility in specifying the underlying wave conditions. Application of the re-calibrated velocity profile shows that wind forces are significantly greater throughout an offshore wind turbine (OWT) swept blade area when large (H= 15 m) and small (H= 1.5 m) wave heights are compared.

Effect of low-level laser therapy on orthodontic dental alignment: a systematic review and meta-analysis.

The aim of this study is to systematically summarize the available evidence regarding low-level laser therapy (LLLT) speed-up effect on dental alignment in comprehensive orthodontic treatment. An extensive electronic search was conducted in PubMed, ScienceDirect, Cochrane, Web of Science, and Scopus up to February 20, 2023. The Cochrane risk of bias tool and the Newcastle-Ottawa Quality Assessment Form were used by two authors independently to assess the risk of bias (RoB). Statistical analysis was performed by Review Manager 5.3. The eight eligible trials were reviewed and included in qualitative synthesis. Four studies reported the overall time of leveling and alignment (OLAT, days), enabling a synthesizing of the data. The meta-analysis results showed that LLLT significantly reduced the overall time of leveling and alignment compared to control group (MD=-30.36, 95% CI range -41.50 to -19.22, P<0.0001), with moderate heterogeneity (χ2=4.10, P=0.25, I2=27%). Based on the data available, statistically significant evidence with moderate risk of bias suggests that LLLT may have a positive effect on accelerating dental alignment. However, due to the differences in intervention strategy and evaluating method, the conclusions should be interpreted with caution.

Effect of three-dimensional geometric structure and surface wettability on two-phase flow behavior in a proton exchange membrane fuel cell gas flow channel: modeling and simulation

Improving water management capability is crucial for enhancing the performance and extending the lifespan of a proton exchange membrane fuel cell (PEMFC). To achieve this goal, this study investigates the coupling effects of geometric features induced by actual gas flow channel (GFC) manufacturing processes and the surface wettability on the dynamic droplet change by simulating 32 cases using the volume of fluid (VOF) method. In addition, the simulated dynamic characteristics of the droplets, such as the centroid position and droplet height, have been verified by comparing them with experimental observations. The reliable results of the simulation show that varied draft angles contribute to different local vortices in the flow channels, arousing two drainage mechanisms—spontaneous and overflow drainage. Besides, the compared results of velocity contours suggest that the curvature effect along the water movement direction could strengthen the speed-up effect around a water droplet, thereby facilitating its detachment. By contrast, a cross-section with filleted corners could cause velocity loss and poor drainage efficiency. A geometric structure with a draft angle of 30° and a bend radius of 1 mm of wavy GFC is beneficial to shorten the water removal time and minimize gas diffusion layer (GDL) water coverage. The hydrophobic treatment of the GDL and channel wall meets both criteria of rapidly reducing liquid water coverage on both the GDL surface and the entire channel. This study's findings are expected to guide the target of both geometric manufacturing and surface treatment processes.

Speed-up and suppression effect of side chain in quantum searching on a graph

Searching efficiency, which biologists and roboticists are ever concerned about, has become important in physics and information science nowadays. In classical probability-based searching problems, as stigmergy, the increase in graph complexity will decrease the searching efficiency. Here we study the searching efficiency based on the first-passage probability and find a counterintuitive phenomenon in quantum walk on a graph with floating vertices. Connecting one vertex in the floating layer to that in the base layer will speed up the searching rapidity, but such a speed-up effect will be suppressed at once if one more vertex is connected to the already connected vertex in the floating layer. This is a counterintuitive phenomenon in comparison to its classical counterpart, where additional vertices at the side chain will retard the searching rapidity. We also propose an ancillary model that bridges the measurement of the probability and the first-passage probability, which is expected to provide new ideas for quantum simulation by means of qubit chips.

The rock breaking mechanism of a combined high-voltage electric impulse-PDC bit drilling technology

Low rock breaking efficiency of drilling bit is one of the key factors restricting the large-scale development of oil gas in deep formations and geothermal energy resources in hot dry rock (HDR). The high-voltage electric impulse (HVEI) drilling technology has unique advantages in deep formation and HDR drilling. However, existing electrode bits form low-quality borehole walls and are not capable of performing directional drilling. To broaden the scope of engineering application of HVEI drilling, a new method combining HVEI drilling with mechanical drilling is proposed in this paper. Based on the structure of the existing electrode bits, a combined HVEI- Polycrystalline Diamond Compact (PDC) bit is designed, and the rock breaking mechanism of the bit is studied. A dynamic damage model (DDM) of rock containing an electrode bit is established on the basis of HVEI drilling's basic process. Furtherly, the HVEI-PDC rock fragmentation model is established by coupling the DDM with the heterogeneous granite model which is based on Voronoi subdivision. Through the analysis of granite fragmentation in HVEI-PDC drilling, relevant conclusions are obtained: Compared with conventional PDC bit, there is no significant difference in the torque variation of the combined bit during drilling. When the electrode spacing Le < 40mm, the energy consumption of the combined bit is higher than that of the conventional PDC bit at low rotating speed, and the efficiency is reduced. When Le≥40mm, the larger the Le, the more obvious the speed-up effect of the combined bit compared with that of the conventional PDC bit, and the lower the drilling cost. The conclusions of this paper are expected to provide a reference for promoting HVEI drilling to achieve wider industrial applications.

Semiempirical Models of Speedup Effect for Downburst Wind Field over 3-D Hills

Downbursts occur frequently in mountainous regions, such as the southwest of China, and causing extensive damage to engineering structures. While some researchers have developed semiempirical models for the speedup effect, most are based on the wind field in the boundary layer over the hill, and there is a lack of semiempirical models for the downburst wind field over the hill. This study employs three RANS (Reynolds Average Navier-Stokes) turbulence models to numerically simulate the downburst wind field over a quadratic curved hill. The realizable k-ε model is selected as the optimal model for the subsequent numerical simulations based on comparison with wind tunnel test results. Then, a semiempirical model of the speedup effect of the downburst wind field over the hill is constructed by numerically simulating the downburst wind field over the hill with different radial locations and different slopes. Finally, the constructed semiempirical model is validated and demonstrates good accuracy.

A new method to improve rock breaking efficiency by using automatic unloading of bottom hole central stress

The main reasons for slow drilling speed in deep formation are poor rock drill-ability, low cutting efficiency and short service life of rock breaking tools caused by high hardness and intensity of bottom hole rock and stress concentration of surrounding rock. In view of this, the concept of releasing rock stress in the bottom hole center to improve rock breaking efficiency and prolong the service life of rock breaking tools is put forward, the bit for automatic unloading of bottom hole central stress (AUOBHCS) is designed, and the testing experiment of rock breaking effect is carried out. The experimental results show that, firstly, the rock breaking efficiency can be improved by using automatic unloading of bottom hole central stress. When the rock breaking energy of the special bit is sufficient, the rock breaking efficiency in limestone and red sandstone can be increased by 1.59 and 4.36 times respectively, and the rock breaking effect still has a large room for improvement. Secondly, WOB and rotating speed are the key factors affecting the rock breaking effect of the bit used for automatically unloading bottom hole central stress, whose speed-up effect increases with the increase of rotating speed and WOB. Thirdly, the bit for automatic unloading of bottom hole central stress has the function of prolonging the service life of the cutter, and it should have some restraining effect on the “holing” of the bit. The above proposed idea of improving rock breaking efficiency and the laboratory test of rock breaking bit provide a new idea for the research and development of downhole rock breaking speed-up technology and tool, and open up a new direction for the drilling speed-up research in deep formation difficult to drill.

Parallel Assembly of Arbitrary Defect-Free Atom Arrays with a Multitweezer Algorithm

Defect-free atom arrays are a precursor for quantum information processing and quantum simulation with neutral atoms. Yet, large-scale defect-free atom arrays can be challenging to realize, due to the losses encountered when rearranging stochastically loaded atoms to achieve a desired target array. Here, we demonstrate a parallel rearrangement algorithm that uses multiple mobile tweezers to independently sort and compress atom arrays in a way that naturally avoids atom collisions. With a high degree of parallelism, our algorithm offers a reduced move complexity compared to both single-tweezer algorithms and existing multitweezer algorithms. We further determine the optimal degree of parallelism to be a balance between an algorithmic speedup and multitweezer inhomogeneity effects. The defect-free probability for a 225-atom array is demonstrated to be as high as 33(1)% in a room-temperature setup after multiple cycles of rearrangement. The algorithm presented here can be implemented for any target array geometry with an underlying periodic structure.Received 13 September 2022Revised 15 December 2022Accepted 19 January 2023DOI:https://doi.org/10.1103/PhysRevApplied.19.034048Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCooling & trappingQuantum algorithmsQuantum information with atoms & lightQuantum simulationPhysical SystemsLatticesNanotechnologyTechniquesOptical tweezersAtomic, Molecular & OpticalQuantum InformationCondensed Matter, Materials & Applied Physics

Implications of steep hilly terrain for modeling wind-turbine wakes

Wind energy is crucial to the transition to a carbon-free world. However, new wind farms are increasingly sited on complex terrain, whose influence on turbine performance is still not well understood. Here large-eddy simulations are performed on the flow around a wind turbine sited on three different terrain types: a flat ground, a 2-D hill, and a 3-D hill. We find that hilly terrain can increase the power generated via the speed-up effect, but that it can also increase the wake deficit and deflect the wake center, potentially affecting any turbines downstream. We interpret this deflection as being caused by the topography-induced vertical velocity component, which we model with a passive tracer method. By combining this passive tracer method with engineering-focused wake models, we obtain improved predictions of the velocity deficit and wake deflection. Such a hybrid strategy is fast and accurate, facilitating the design of wind farms sited on steep hilly terrain, which often experience flow separation at the backslope.

Investigation into wind turbine wake effect on complex terrain

In complex-terrain wind fields, the wind speed-up phenomenon is pronounced on highlands, which has huge impact on wake development. This paper comprehensively investigates the wind speed-up and the wake effect in complex terrains. The objective is to develop an advanced process to reveal the complex wake characteristics. Both theoretical and experimental methods are used to the study. First, the wind speed-up characteristics caused by topography are discussed, and the wind speed-up over escarpments with different shapes is numerically studied. Based on the results, the impact of wind speed-up on average wind speed of wind turbine is investigated. Next, a three-dimensional wake model for complex terrains is developed, and the model is applicable for the terrain with slope of less than 0.3. Then, a wind field experiment is conducted on a two-dimensional hill, and the wake model is validated and further improved for application to escarpments. From this research, both large aspect ratio and small rotor diameter have significant influence on the average wind speed. Even in the wake area, the wind speed on highland is stronger than that on flat terrain, and the wind speed increment is the largest at the height of 0.25D. In complex-terrain wind fields, the wind speed-up effect must be carefully considered at least within the 5D downwind distance.