Average Momentum Research Articles

Simulating unsteady flows on a superconducting quantum processor

Recent advancements of quantum technologies have triggered tremendous interest in exploring practical quantum advantage. The simulation of fluid dynamics, a highly challenging problem in classical physics but vital for practical applications, emerges as a potential direction. Here, we report an experiment on the digital simulation of unsteady flows with a superconducting quantum processor. The quantum algorithm is based on the Hamiltonian simulation using the hydrodynamic formulation of the Schrödinger equation. With the median fidelities of 99.97% and 99.67% for parallel single- and two-qubit gates respectively, we simulate the dynamics of a two-dimensional (2D) compressible diverging flow and a 2D decaying vortex with ten qubits. Note that the former case is an inviscid potential flow, and the latter one is an artificial vortical flow with an external body force. The experimental results well capture the temporal evolution of averaged density and momentum profiles, and qualitatively reproduce spatial flow fields with moderate noises. This work demonstrates the potential of quantum computing in simulating more complex flows, such as turbulence, for practical applications.

Darcy's law survival from no-slip to perfect-slip flow in porous media

A macroscopic model for perfect-slip flow in porous media is derived in this work, starting from the pore-scale flow problem and making use of an upscaling technique based on the adjoint method and Green's formula. It is shown that the averaged momentum equation has a Darcy form in which the permeability tensor, $\boldsymbol{\mathsf{K}}_{ps}$ , is obtained from an associated adjoint (closure) problem that is to be solved on a (periodic) unit cell representative of the structure. Similarly to the classical permeability tensor, $\boldsymbol{\mathsf{K}}$ , in the no-slip regime, $\boldsymbol{\mathsf{K}}_{ps}$ is intrinsic to the porous medium under consideration and is shown to be symmetric and positive. Integral relationships between $\boldsymbol{\mathsf{K}}_{ps}$ , the partial-slip flow permeability tensor, $\boldsymbol{\mathsf{K}}_{s}$ , and $\boldsymbol{\mathsf{K}}$ are derived. Numerical simulations carried out on two-dimensional model porous structures, together with an approximate analytical solution and an empirical correlation for a particular configuration, confirm the validity of the macroscopic model and the relationship between $\boldsymbol{\mathsf{K}}_{ps}$ and $\boldsymbol{\mathsf{K}}$ .

Numerical and geometric investigation of pool boiling heat transfer in cavities with isothermal rectangular corrugations

This numerical work presents a geometrical investigation of a corrugated isothermal surface placed in a two-dimensional cavity subjected to unsteady, turbulent pool boiling flows. The main purposes are maximizing the heat transfer rate between the isothermal surface and the surrounding water flow, and the volume of vapor generated into the cavity. The geometric investigation followed the constructal design method, being the ratio Hi/Li (i = 1, 2 or 3) of the corrugations varied for three different numbers of corrugations: N = 1, 2, and 3, keeping constant the corrugations area. The volume of fluid (VOF) and Lee's evaporation-condensation models are used to estimate the volume fractions of water vapor/liquid and interfacial mass transfer. The unsteady Reynolds Averaged Navier Stokes (URANS) continuity, momentum and conservation of energy equations, and volume fraction transport equation, are solved using the finite volume method (FVM) available in software Ansys FLUENT. For closure of turbulence, the k - ɛ model is adopted. For validation of the model, the heat flux and convection heat transfer coefficient obtained for a pool boiling bared surface case are compared with Rohsenow's correlations, and differences lower than 7.0 % are reached. Results indicated a strong influence of the ratio Hi/Li and number of corrugations (N) in the heat transfer rate per unit depth (qs) and dimensionless volume of vapor (Vdim) generated into the cavity. The highest intrusion of the corrugations led to the generation of few large and many small scales, benefiting the thermal performance, regardless of the performance indicator employed. The optimal configuration, N = 3 and H3/L3 = 2.0 improved 49 % and 188 % the Vdim and qs compared with the worst corrugated case, showing the importance of the geometry of the corrugation in this problem.

A novel explicit fully-discrete momentum-preserving scheme of damped nonlinear stochastic wave equation influenced by multiplicative space-time noise

In this paper, the evolution laws of global momentum and averaged global momentum for the damped nonlinear stochastic wave equation (DNSWE) influenced by multiplicative space-time noise are derived. We innovatively combine the second-order central finite difference method and discrete gradient method in space, and integrate the splitting method and Störmer-Verlet type method in time. Both the novel spatial semi-discrete scheme and fully-discrete scheme constructed in this way can successfully preserve the corresponding evolution laws for discrete global momentum and discrete averaged global momentum. Numerical experiments on DNSWE with cubic nonlinearity validate the theoretical results.

Hidden vortices and Feynman rule in Bose-Einstein condensates with density-dependent gauge potential.

In this paper, we numerically investigate the vortex nucleation in a Bose-Einstein condensate (BEC) trapped in a double-well potential and subjected to a density-dependent gauge potential. A rotating Bose-Einstein condensate, when confined in a double-well potential, not only gives rise to visible vortices but also produces hidden vortices. We have empirically developed Feynman's rule for the number of vortices versus angular momentum in Bose-Einstein condensates in the presence of density-dependent gauge potentials. The variation of the average angular momentum with the number of vortices is also sensitive to the nature of the nonlinear rotation due to the density-dependent gauge potentials. The empirical result agrees well with the numerical simulations and the connection is verified by means of curve-fitting analysis. The modified Feynman rule is further confirmed for the BECs confined in harmonic and toroidal traps. In addition, we show the nucleation of vortices in double-well and toroidally confined Bose-Einstein condensates solely through nonlinear rotations (without any trap rotation) arising through the density-dependent gauge potential.

Quantisation across bubble walls and friction

We quantise from first principles field theories living on the background of a bubble wall in the planar limit with particular focus on the case of spontaneous breaking of gauge symmetry. Using these tools, we compute the average momentum transfer from transition radiation: the soft emission of radiation by an energetic particle passing across the wall, with a particular focus on the longitudinal polarisation of vectors. We find these to be comparable to transverse polarisations in symmetry-breaking transitions with mild super-cooling, and dominant in broken to broken transitions with thin wall. Our results have phenomenological applications for the expansion of bubbles during first order phase transitions. Our general framework allows for the robust calculation of any particle processes of interest in such translation breaking backgrounds.

Revealing the Close Connection Between Tennis Match Momentum and Victory Through Machine Learning Methods

In competitive sports, especially in tennis matches, momentum is considered a key factor influencing the outcome. However, there is widespread controversy surrounding the definition of momentum, its quantification methods, and its impact on match results. We compared different models (LightGBM, SVM, XGBoost, MLP, logistic regression) using five-fold cross-validation to predict changes in momentum in tennis matches based on a given dataset. The results showed that LightGBM performed best with an accuracy of 77.6%. We selected LightGBM to predict the momentum score for each point of player 1 in the final match. It was found that the average momentum scores in the second, third, and fifth sets were greater than 0.5, which aligned with the actual outcomes. Furthermore, through Pearson correlation analysis and OLS validation of the relationship between momentum changes and match results, we obtained a p-value below 0.05, a Pearson correlation coefficient of 0.59, and an F-statistic of 376.6 in the OLS model, indicating a strong positive correlation between the two.

Electromagnetic and gravitational local spatial densities for hadrons

The novel definition of electromagnetic and gravitational local spatial densities of hadrons in zero average momentum frame are considered. The connection of these densities with the densities in infinite-momentum frame and the comparison with densities in the static approximation (Breit-frame densities) are discussed.

Optimization of low-energy slow extraction efficiency of XiPAF

Xi’an Proton Application Facility (XiPAF) synchrotron provides 10∼200MeV proton beam for the experimental simulation of the space radiation environment. Due to the space charge effect, the slow extraction of 10 MeV proton beam is a work full of challenges. In a past experiment, the total extraction efficiency was over 65% with 4.5 ∽ 6.5×1010 protons stored before extraction but decreased to 52% with 9×1010 protons stored. In order to study the beam loss caused by a strong space charge effect, based on experimental parameters, the beam loss fractions at different positions of XiPAF synchrotron are obtained through the simulation. According to the beam loss analysis, optimized parameters are found for reference in subsequent experiments. It is also noted that negative beam average momentum spread before extraction is beneficial to the improvement of extraction efficiency.

Single-nucleotide polymorphisms link gout with health-related lifestyle factors in Korean cohorts

Gout—a very painful inflammatory arthritis caused by the deposition of monosodium urate crystals in the joints—is influenced by several factors. We identified the association of single- nucleotide polymorphisms (SNPs) that link gout with health-related lifestyle factors using genomic data from the Korean Genome and Epidemiology Study. We conducted a genome-wide association study (GWAS) on 18,927 samples of 438 Korean patients with gout and 18,489 controls for the discovery stage. For the replication stage, another batch containing samples of 326 patients with gout and 2,737 controls were analyzed. Lastly, a meta-analysis was performed using these two cohorts. We analyzed the effects of health-related lifestyle factors, including eating habits, physical activity, drinking behavior, and smoking behavior, on gout. After identifying the association between GWAS-derived SNPs and health-related lifestyle factors, we confirmed the interaction between the polygenic risk score (PRS) and health-related lifestyle factors. We identified 15 SNPs related to gout, among which rs1481012 of ABCG2 located on chromosome 4 has been newly discovered (P = 2.46e-11). On examining the interaction between SNPs and health-related lifestyles, rs3109823—located in ABCG2—was found to be associated with smoking status. In addition, rs11936395—located in SLC2A9—was significantly associated with the average momentum of exercise per session, whereas rs11066325 located in PTPN11, showed a significant association with the number of exercise sessions per week, smoking status, drinking status, and amount of soju drink per session. rs9421589—located in FAM35A—was significantly associated with the duration of smoking. In addition, we verified that the association between PRS and duration of smoking affects gout. Thus, in this study, we identified novel SNPs that link gout with health-related lifestyle factors in the Korean population.

Turbulent flow modification in the atmospheric surface layer over a dense city

Winds in the atmospheric surface layer (ASL) over distinctive urban morphology are investigated by building-resolved large-eddy simulation (LES). The exponential law is applied to urban canopy layers (UCLs) unprecedentedly to parameterize vertical profiles of mean-wind-speed u¯z and examine the influence of morphological factors. The skewness of streamwise velocity Su is peaked at the zero-plane displacement d (drag center) where flows decelerate mostly. The dynamics and intermittency in roughness sublayers (RSLs) are further contrasted. It helps determine the critical strength of the organized structures (ejection, Q2 and sweep Q4) in their contributions to the average momentum transport (i.e., 3<u”w”> to 5<u”w”>). Two key factors of the local-scale dynamics are revealed - building heterogeneity and upstream giant wakes that could amplify turbulence kinetic energy (TKE) and energetic intermittent Q4 by different mechanisms. The former is conductive for large-eddy generation that promotes vertical fluctuating velocity w”, stimulating intermittent, energetic Q2 and Q4. The latter, whose footprints are identified by the two-point correlation of streamwise velocity Ruu with specific size and inclination, facilitates intermittent, fast streamwise fluctuating velocity u”, forming vigorous Q4. Nevertheless, excessive planar density λp (≈ 0.7) is detrimental to both transport processes. These findings contribute to the theoretical and empirical wall models of large-scale roughness that help urban planners and policymakers to improve air quality.

Study on combustion characteristics of sinusoidal hydrogen pulsed jet with different frequencies in supersonic flows

Pulsed jets can effectively improve mixing and combustion efficiencies, while sinusoidal pulsed jets have the advantages of good performance and simple setup. Therefore, the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations and Shear Stress Transfer k-omega model (SST) are utilized to study the combustion characteristics of sinusoidal pulsed jets with three different frequencies and steady jet in order to obtain an approach to improve the combustion performance in the supersonic flow. In the current study, the combustion performances of the steady jet and the pulsed jets with an equal average momentum flux ratio to the steady jet are compared and analyzed, and the instantaneous combustion characteristics of four different time points in one cycle of the pulsed jets are analyzed in detail. The obtained results show that the pulsed jet can obviously improve the combustion efficiency, although the total pressure loss is slightly larger than that of the steady jet. On the whole, the pulsed jets have a good impact on the combustion performance of the combustor, and the combustion performance of the f = 20 kHz pulsed jet case is the best in this study.

Expected Value of Helium Ion Electron Momentum in Momentum Space with Primary Quantum Numbers n≤3

The aim is the expected value of helium ions to determine its properties as a heat transmitter to reactors and chirogenic science. This research is non-experimental research using quantum mechanics literature study methods because there are many previous studies that are relevant to this research. Data on the expected value of electron momentum in helium ions is determined based on numerical calculations using the Matlab 2015a program to simplify calculations using ion expectation calculations in momentum. The results obtained are that the electron momentum value in the helium ion can provide an overview of the average momentum value of the helium ion electrons in momentum space. This research data also shows that in momentum space the expected value of electron momentum decreases as the principal quantum number (n) increases. This can be seen when n=1,l =0 then 3p0 = 1.3146, and when n=3,l =0 then 3p0 = 0.5098.

Epidemiology and Time-Loss Shoulder Injuries in Professional South African Rugby Players: A Prospective Study That Focuses on Real-Time Collision Data during a Tackle

Background: In rugby, the shoulder contributes to attack/defence during collisions, tackling, falling, scrummaging, and mauling. We investigated the frequency, tissue, and pathology type of shoulder injuries per player position among professional South African rugby players, and compared injury severity in the context of momentum, intensity, and collision variables. Methods: A prospective study collecting shoulder injury data of 80 male Super Rugby players (&gt;18 years) over 4 seasons (2018–2021). Players wore a Catapult Evo GPS unit during training and match-play, recording performance variables and collision forces during injury. We collected tissue and pathology types of injury from players’ medical files, clinical examinations, and special investigations. Results: Shoulder injuries contributed to 17% of all injuries, ranging from 2 to 34% per year. Forwards (63%) sustained most shoulder injuries, specifically locks (30%). Acromioclavicular (AC) joint (47%) was mostly involved, and ligament/joint capsule (65%) was the most common tissue type injured. Injuries with the highest average momentum resulted in players suffering minimal to mild severity injuries (1–7 days time-loss). Backs (631.15 kg·m/s) required less momentum than forwards (816.00 kg·m/s) to suffer injuries resulting in &gt;28 days time-loss (p = 0.008). Backs encountered higher match intensity (67.76 m/min, p = 0.031) and highest average collisions (0.28/min) without suffering more severe (&gt;28 days time-loss) injuries. Match intensity of &gt;60 m/min resulted in more than 55% of shoulder injuries. Conclusion: One in six injuries in this cohort was shoulder-related. Forwards, specifically locks, sustained most shoulder injuries. The AC joint was the tissue type that mainly contributed. Backline players were involved in higher velocity contact, game intensity, and collision frequency but suffered fewer injuries. However, they required less momentum to sustain more severe injuries.

Generation of discrete higher-order optical vortex lattice at focus.

Higher-order vortices (HOVs) extend the dimensions of optical vortex regulation, which is of great significance in optical communication and optical tweezers. Herein, we demonstrate an alternative scheme to produce a HOV in the focus plane using multiple Laguerre-Gaussian (LG) beam interference, termed a discrete higher-order optical vortex lattice (DHOVL). The modulation depth of the DHOVL exceeds 2π. In this case, the topological charge (TC) of the DHOVL is determined by the difference of the phase period between the innermost and the outermost interference beams. Compared with a conventional HOV (CHOV), the vortex exists in a form of multiple unit singularities sharing a dark core. In addition, the average orbital angular momentum per photon of the DHOVL increases with increasing TC, surpassing that of the CHOV. This work provides a novel, to the best of our knowledge, scheme to produce a HOV, which will facilitate several advanced applications, including optical micromanipulation, optical sensing and imaging, and optical fabrication.

Dynamic stall flow control with multistage dielectric-barrier discharge actuation under light stall conditions

This study employs a numerical simulation method that combines the plasma body force model based on electrostatics with the Navier–Stokes equations to investigate the coupling mechanism of flow fields induced by multistage dielectric-barrier discharge (MDBD) actuation. Compared to conventional single-stage alternating-current DBD (AC-DBD) actuation, MDBD actuation provides higher actuation intensity and larger flow control region, which are advantageous for improving the flow control effect of DBD actuation. Numerical simulations are conducted based on the established MDBD flow control technology to study the flow control of the dynamic stall of an airfoil. The mechanism by which MDBD actuation-induced vortices delay dynamic stall and accelerate flow reattachment under unsteady conditions is analyzed. A control effect comparison with single-stage AC-DBD actuation validates the technical advantages of MDBD actuation in improving the average aerodynamic force, delaying lift and momentum stall, reducing the hysteresis effect, suppressing negative aerodynamic damping, and accelerating flow reattachment.

Classical interpretation for the influence of XUV pulse width on the streaking time delay and the oscillation amplitude of the momentum shift

We numerically investigate both the streaking time delay and the oscillation amplitude of the momentum shift of the photoelectron and justify them physically by developing a classical model based on the weak field approximation. The streaking time delay is insensitive to the extreme ultraviolet (XUV) pulse duration, while the oscillation amplitude obviously reduces as the XUV duration increases. This XUV duration dependence is attributed to the ionization probability of electron at initial times other than the peak of the XUV pulse. We propagate the classical electron trajectories originating at different initial times in the coupled Coulomb-laser (IR) potential and average the momentum shift for each trajectory over the width of the XUV pulse. By extracting the streaking time delay and the oscillation amplitude from this averaged momentum shift, the classical model results and the time-dependent Schrödinger equation results are found to be in good agreement. Both the insensitivity of the streaking time delay and the sensitivity of the oscillation amplitude on the XUV pulse width are well explained by our classical model considering initial ionization time average. Analytical estimation for the oscillation amplitude is obtained from the model of initial ionization time average.

Theoretical analysis of unsteady buoyant turbulent heat and mass transport from a vertical plate using LRN k-ϵ model

The contemporary analysis has been developed to investigate the transient natural convective combined heat and mass transport of a turbulent flow adjacent to the plate by utilizing the low Reynolds number (LRN) k-ϵ model. The research problem on turbulent flow is assumed to be two dimensional and viscous incompressible. The governing turbulent equations such as continuity, momentum, energy, concentration, turbulent kinetic energy (TKE) and dissipation rate of TKE are considered as per the flow geometry. Due to the non-availability of analytical or direct numerical techniques, the corresponding highly nonlinear PDE’s are solved by adopting the standard implicit type of finite difference method namely Crank–Nicolson scheme. Also, this scheme is unconditionally stable and helps to keep the governing turbulent flow equations in discretized form and are solved via tridiagonal matrix algorithm. The simulated results for several control parameters including turbulent Reynolds number are graphically displayed and also analyzed the flow profiles. To understand the physical phenomenon of turbulent flow, the authors shown the turbulent behavior of average momentum, energy and mass transfer rates. It has been noted that, the average temperature and concentration fields boosted with rising values of . Also, TKE and dissipation rate of TKE profiles increase with enhancing turbulent values. In addition, the simulated turbulent flow results from the LRN k-ϵ model are compared with usual laminar flows as a special case and found to be in respectable agreement.

Particle interferometry in a moat regime

Dense strongly interacting matter can exhibit regimes with spatial modulations, akin to crystalline phases. In this case particles can have a moat spectrum with minimal energy at nonzero momentum. We show that particle interferometry is a sensitive probe of such a regime in heavy-ion collisions. To this end, we develop a field-theoretical formalism that relates particle spectra to in-medium real-time correlation functions of quantum fields on curved hypersurfaces of spacetime. This is then applied to the study of Bose-Einstein correlations in a moat regime in heavy-ion collisions. The resulting two-particle spectra exhibit peaks at nonzero average pair momentum, in contrast to the two-particle spectra in a normal phase, which peak at zero momentum. These peaks lead to nontrivial structures in the ratio of two-particle correlation functions, which should be experimentally measurable if the resolution in the direction of average pair momentum is sufficiently large. We propose these structures in the correlation-function ratios as clear signature of a moat regime and spatially modulated phases in quantum chromodynamics (QCD).

Collapse Dynamics Are Diffusive.

Noninterferometric experiments have been successfully employed to constrain models of spontaneous wave function collapse, which predict a violation of the quantum superposition principle for large systems. These experiments are grounded on the fact that, according to these models, the dynamics is driven by noise that, besides collapsing the wave function in space, generates a diffusive motion with characteristic signatures, which, though small, can be tested. The noninterferometric approach might seem applicable only to those models that implement the collapse through noisy dynamics, not to any model, that collapses the wave function in space. Here, we show that this is not the case: under reasonable assumptions, any collapse dynamics (in space) is diffusive. Specifically, we prove that any space-translation covariant dynamics that complies with the no-signaling constraint, if collapsing the wave function in space, must change the average momentum of the system and/or its spread.