Hydrodynamic Solution Research Articles

Hydrodynamic Attractor in Ultracold Atoms.

The hydrodynamic attractor is a concept that describes universal equilibration behavior in which systems lose microscopic details before hydrodynamics becomes applicable. We propose a setup to observe hydrodynamic attractors in ultracold atomic gases, taking advantage of the fact that driving the two-body s-wave scattering length causes phenomena equivalent to isotropic fluid expansions. We specifically consider two-component fermions with contact interactions in three dimensions and discuss their dynamics under a power-law drive of the scattering length in a uniform system. By explicit computation, we derive a hydrodynamic relaxation model. We analytically solve their dynamics and find the hydrodynamic attractor solution. Our proposed method using the scattering length drive is applicable to a wide range of ultracold atomic systems, and our results establish these as a new platform for exploring hydrodynamic attractors.

Hydrodynamics of a discrete conservation law

AbstractThe Riemann problem for the discrete conservation law is classified using Whitham modulation theory, a quasi‐continuum approximation, and numerical simulations. A surprisingly elaborate set of solutions to this simple discrete regularization of the inviscid Burgers' equation is obtained. In addition to discrete analogs of well‐known dispersive hydrodynamic solutions—rarefaction waves (RWs) and dispersive shock waves (DSWs)—additional unsteady solution families and finite‐time blowup are observed. Two solution types exhibit no known conservative continuum correlates: (i) a counterpropagating DSW and RW solution separated by a symmetric, stationary shock and (ii) an unsteady shock emitting two counterpropagating periodic wavetrains with the same frequency connected to a partial DSW or an RW. Another class of solutions called traveling DSWs, (iii), consists of a partial DSW connected to a traveling wave comprised of a periodic wavetrain with a rapid transition to a constant. Portions of solutions (ii) and (iii) are interpreted as shock solutions of the Whitham modulation equations.

Estimation of Physical Stellar Parameters from Spectral Models Using Deep Learning Techniques

This article presents a new algorithm that uses techniques from the field of artificial intelligence to automatically estimate the physical parameters of massive stars from a grid of stellar spectral models. This is the first grid to consider hydrodynamic solutions for stellar winds and radiative transport, containing more than 573 thousand synthetic spectra. The methodology involves grouping spectral models using deep learning and clustering techniques. The goal is to delineate the search regions and differentiate the “species” of spectra based on the shapes of the spectral line profiles. Synthetic spectra close to an observed stellar spectrum are selected using deep learning and unsupervised clustering algorithms. As a result, for each spectrum, we found the effective temperature, surface gravity, micro-turbulence velocity, and abundance of elements, such as helium and silicon. In addition, the values of the line force parameters were obtained. The developed algorithm was tested with 40 observed spectra, achieving 85% of the expected results according to the scientific literature. The execution time ranged from 6 to 13 min per spectrum, which represents less than 5% of the total time required for a one-to-one comparison search under the same conditions.

Analytical insights into the interplay of momentum, multiplicity, and the speed of sound in heavy-ion collisions

We introduce a minimal model of ultracentral heavy-ion collisions to study the relation between the speed of sound of the produced plasma and the final particles' energy and multiplicity. We discuss how the particles' multiplicity Ntot and average energy Etot/Ntot is related to the speed of sound cs by cs2=dln(Etot/Ntot)/dlnNtot if the fluid is inviscid, its speed of sound is constant and all final particles can be measured. We show that finite rapidity cuts on the particles' multiplicity N and energy E introduce corrections between cs2 and dln(E/N)/dlnN that depend on the system's lifetime. We study analytically these deviations with the Gubser hydrodynamic solution, finding that, for ultrarelativistic bosons, they scale as the ratio of the freeze-out temperature TFO over the maximum initial temperature of the fluid T0; the nonthermodynamic aspect of these corrections is highlighted through their dependence on the system's initial conditions. Published by the American Physical Society 2024

Residual and Unmodeled Ocean Tide Signal From 20+ Years of GRACE and GRACE‐FO Global Gravity Field Models

AbstractWe analyze remaining ocean tide signal in K/Ka‐band range‐rate (RR) postfit residuals, obtained after estimation of monthly gravity field solutions from 21.5 years of Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow‐On sensor data. Low‐pass filtered and numerically differentiated residuals are assigned to grids and a spectral analysis is performed using Lomb‐Scargle periodograms. We identified enhanced amplitudes at over 30 ocean tide periods. Spectral replicas revealed several tides from sub‐semidiurnal bands. Increased ocean tide amplitudes are located in expected regions, that is, in high‐latitude, coastal and shallow water regions, although some tides also show distinct patterns over the open ocean. While most identified tides are considered during processing, and therefore the amplitudes represent residual signal w.r.t. the ocean tide model, several unmodeled tides were found, including astronomical degree‐3 tides , , , , and radiational and/or compound tides , , , and . The astronomical degree‐3 tides were observed on a global level for the first time a few years ago in altimeter data. We are unaware of any global data‐constrained solutions for the other tides. The amplitude patterns of these tides exhibit similarities to purely hydrodynamic solutions, and altimeter observations (astronomical degree‐3 only). The sensitivity of the satellites to these rather small tidal effects demands their inclusion into the gravity field recovery processing to reduce orbit modeling errors and a possible aliasing. The conducted study shows enormous potential of RR postfit residuals analysis for validating ocean tide models and improving gravity field recovery processing strategies.

Offsetting Dense Particle Sedimentation in Microfluidic Systems.

Sedimentation is an undesirable phenomenon that complicates the design of microsystems that exploit dense microparticles as delivery tools, especially in biotechnological applications. It often informs the integration of continuous mixing modules, consequently impacting the system footprint, cost, and complexity. The impact of sedimentation is significantly worse in systems designed with the intent of particle metering or binary encapsulation in droplets. Circumventing this problem involves the unsatisfactory adoption of gel microparticles as an alternative. This paper presents two solutions-a hydrodynamic solution that changes the particle sedimentation trajectory relative to a flow-rate dependent resultant force, and induced hindered settling (i-HS), which exploits Richardson-Zaki (RZ) corrections of Stokes' law. The hydrodynamic solution was validated using a multi-well fluidic multiplexing and particle metering manifold. Computational image analysis of multiplex metering efficiency using this method showed an average reduction in well-to-well variation in particle concentration from 45% (Q = 1 mL/min, n = 32 total wells) to 17% (Q = 10 mL/min, n = 48 total wells). By exploiting a physical property (cloud point) of surfactants in the bead suspension in vials, the i-HS achieved a 58% reduction in the sedimentation rate. This effect results from the surfactant phase change, which increases the turbidity (transient increase in particle concentration), thereby exploiting the RZ theories. Both methods can be used independently or synergistically to eliminate bead settling in microsystems or to minimize particle sedimentation.

A Revisited Equilibrium Solution of the Fishbone and Moncrief Torus for Extended General Relativistic Magnetohydrodynamic Simulations

Accretion physics has become more important recently due to the detection of the first horizon-scale images of the supermassive black holes of M 87* and Sgr A* by the Event Horizon Telescope. General relativistic magnetohydrodynamic (GRMHD) simulations of magnetized accretion flows onto a Kerr black hole have been used to interpret them. However, further testing the theory of gravity by using horizon-scale images requires performing consistent GRMHD simulations in non-Kerr spacetime. In this paper, we revisited the hydrodynamical equilibrium solution of the Fishbone and Moncrief (FM) torus that can be used to study any stationary, axisymmetric, vacuum, or nonvacuum spacetime. Further, we check the stability of the FM torus in non-Kerr spacetime by general relativistic hydrodynamic simulations. We find that FM torus in non-Kerr spacetime is indeed stable under long-term evolution. We conclude that the generalized FM torus solution would be very useful for creating new GRMHD libraries in extended Kerr black holes.

Hydroacoustic analysis of a full-scale marine vessel: Prediction of the cavitation-induced underwater radiated noise using large eddy simulations

This numerical study provides insight into the mechanism of noise generation by a cavitating flow in the wake of a marine propeller under realistic operating conditions, which poses a significant threat to marine ecosystems. We examined a full-scale vessel with an entire hull and an isolated model-scale marine propeller (INSEAN E779A) with a maneuverable rudder under various highly turbulent inflow conditions that strongly affect the spectral characteristics of the radiated noise. Insight into the acoustic behavior was gained by employing a combination of the large eddy simulation (LES) treatment of turbulence and the Schnerr–Sauer volume of fluid cavitation model. The hydrodynamic solution was coupled with the Ffowcs Williams-Hawkings (FW-H) strategy for noise and vibration identification. We focused on the interactions between the characteristic cavitation patterns of marine propellers (sheet, tip, and hub cavities) and the dominant structures of the turbulent wake (tip, root, trailing edge, and hub vortices, as well as the distributed small-scale vorticity). The small-scale topological structures in the swirling wake of a propeller directly manifest in the radiated sound level and affect the intensity of multiple frequency ranges. Quantitative analysis of thrust, pressure fluctuations, and sound pressure levels (SPLs) demonstrates significant effects of blade loading, wake distribution, and cavitation development. The peak and average SPL distributions obtained through LES show lower dominant and higher average frequencies compared to those obtained by the FW-H method. The overall SPL obtained by LES were higher than those calculated using the FW-H acoustic analogy at all microphone locations. The overall noise was dominated by the low-frequency broadband noise, attributed to energetic helical vortices, and narrow-band peaks in the medium-high frequency range that originated from other sources, like cavitation structures.

Exploring freeze-out and flow using exact solutions of conformal hydrodynamics

Exploring freeze-out and flow using exact solutions of conformal hydrodynamics

Theoretical modeling of a bottom-raised oscillating surge wave energy converter structural loadings and power performances

This study presents theoretical formulations to evaluate the fundamental parameters and performance characteristics of a bottom-raised oscillating surge wave energy converter (OSWEC) device. Employing a flat plate assumption and potential flow formulation in elliptical coordinates, closed-form equations for the added mass, radiation damping, and excitation forces/torques in the relevant pitch-pitch and surge-pitch directions of motion are developed and used to calculate the system's response amplitude operator and the forces and moments acting on the foundation. The model is benchmarked against numerical simulations using WAMIT and WEC-Sim, showcasing excellent agreement. The sensitivity of plate thickness on the analytical hydrodynamic solutions is investigated over several thickness-to-width ratios ranging from 1:80 to 1:10. The results show that as the thickness of the benchmark OSWEC increases, the deviation of the analytical hydrodynamic coefficients from the numerical solutions grows from 3 % to 25 %. Differences in the excitation forces and torques, however, are contained within 12 %. While the flat plate assumption is a limitation of the proposed analytical model, the error is within a reasonable margin for use in the design space exploration phase before a higher-fidelity (and thus more computationally expensive) model is employed. A parametric study demonstrates the ability of the analytical model to quickly sweep over a domain of OSWEC dimensions, illustrating the analytical model's utility in the early phases of design.

Vibration response analysis of rotor system coupled with a novel 4-DOF SFD hydrodynamic model considering the influence of rotational displacement

As a damping structure, squeeze film dampers (SFDs) are commonly employed in turbomachinery. Aiming at the problem of hydrodynamic modeling and solution, this paper presents a four-degree-of-freedom (4-DOF) hydrodynamics model of SFD, which not only considers the influence of radial displacement on oil film clearance but also the influence of rotational displacement. The Reynolds equation of the SFD is solved utilizing the finite difference method (FDM). The oil film gap distribution and static properties of the SFD under different rotational displacements and journal eccentricity are analyzed. Then, the hydrodynamic model of the 4-DOF SFD is coupled with the rotor system, and the vibration characteristics of the SFD-rotor system are analyzed. Finally, the experimental verification is carried out. The analysis results reveal that the rotational displacement has little influence on the vibration response of the SFD-rotor system at the non-critical speed. However, near the critical speed, the occurrence of rotational displacement of the SFD is more beneficial to the vibration reduction effect. Moreover, the analysis results of the hydrodynamic characteristics of the SFD show that when the eccentricity is less than 0.4, the rotational displacement has little effect on the oil film gap distribution, load moment, and oil film reaction force. When the eccentricity exceeds 0.4, the rotational displacement has a great influence on the gap distribution, load moment, and oil film reaction force of SFD.

Incompressible smoothed particle hydrodynamics solutions of double diffusion of nanoparticle-enhanced phase change materials in vertical mounted circular cylinders

The scheme of incompressible smoothed particle hydrodynamics (ISPH) method is developed to solve the time-conformable systems that control the double diffusion of nanoparticle-enhanced phase change materials (NEPCM) inside two circular cylinders saturated by a porous medium. The use of the time-conformable operator in the ISPH approach for addressing the double diffusion of NEPCM in a new domain is what distinguishes this work. This investigation revealed a comprehensive rate of change that impacts the quickening and slowdown of the monotonicity for the nonlinear systems. The physical parameters are time-conformable operator α , time parameter τ , nanoparticles parameter ϕ , Hartmann number Ha , thermal radiation parameter Rd , Darcy parameter Da , Rayleigh number Ra , and fusion temperature θ f . The principal outcomes of the numerical simulations revealed that the nanofluid flow is slowing down by an augmentation in ϕ , Ha , and Rd . The Rayleigh number is working well in enhancing the nanofluid flow and thermosolutal convection within the two circular cylinders. As a result, variable values of Ra are affecting the phase change material. The fusion temperature parameter controls the position/intensity of the phase change material within the two circular cylinders. Besides, the numerical results indicate the significance of α on the transition process of reaching the steady state. The thermosolutal convection and nanofluid speed are varied with the changes on the time-conformable derivative.

Describing the thermal radiation in Au+Au collisions at sNN=200 GeV by an analytic solution of relativistic hydrodynamics

In high-energy heavy-ion collisions, a nearly perfect fluid, the so-called strongly coupled quark–gluon plasma (QGP), forms. After the short period of thermalization, the evolution of this medium can be described by the laws of relativistic hydrodynamics. The time evolution of the QGP can be understood through direct photon spectra measurements, which are sensitive to the entire period between the thermalization and the freeze-out of the medium. I present a new analytic formula that describes the thermal photon radiation and it is derived from an exact and finite solution of relativistic hydrodynamics with accelerating velocity field. Then I compare my calculations to the most recent nonprompt spectrum of direct photons for [Formula: see text] at [Formula: see text][Formula: see text]GeV collisions. I have found a convincing agreement between the model and the data, which allows to give an estimate of the initial temperature in the center of the fireball. My results predict hydrodynamic scaling behavior for the thermal photon spectra of high-energy heavy-ion collisions.

Analysis of the hydrodynamic causes of thrombosis and hemolysis in the centrifugal pump of the artificial blood supply system

The article is devoted to the analysis of the hydrodynamic causes of complications of the use of centrifugal pumps in artificial circulation systems. In the treatment of cardiovascular diseases, rotary pumps began to be used: centrifugal, axial and disk. Of the three types of rotary pumps, centrifugal pumps have the highest power density due to the use of centrifugal force. Statistics show that the greatest blood damage in the form of thrombosis and hemolysis is observed in these pumps. The article concludes that the main hydrodynamic cause of thrombosis and hemolysis is the force field formed by the centrifugal force of inertia, which generates vortex and separation zones. When passing through these zones, red blood cells experience intense hydrodynamic effects in the form of local accelerations and impacts against the walls of the channels, which leads to their deformation, and then to the destruction of some red blood cells. On the one hand, thanks to this force, the intensity of energy conversion in a centrifugal pump becomes higher compared to other types of pumps. On the other hand, a large unevenness of speed and pressure occurs in the channels, which has a traumatic effect on red blood cells. Hydrodynamic solutions to weaken the force field that injures red blood cells will inevitably be accompanied by a decrease in the intensity of energy conversion and the benefits of using this type of pump.

Numerical Framework for the Coupled Analysis of Floating Offshore Multi-Wind Turbines

Floating offshore multi-wind turbines (FOMWTs) are an interesting alternative to the up-scaling of wind turbines. Since this is a novel concept, there are few numerical tools for its coupled dynamic assessment at the present time. In this work, a numerical framework is implemented for the simulation of multi-rotor systems under environmental excitations. It is capable of analyzing a platform using leaning towers that handle wind turbines with their own features and control systems. This tool is obtained by coupling the seakeeping hydrodynamics solver SeaFEM with the single wind turbine simulation tool OpenFAST. The coupling of SeaFEM provides a higher fidelity hydrodynamic solution, allowing the simulation of any structural design using the finite element method (FEM). Additionally, a methodology is proposed for the extension of the single wind solver, allowing for the analysis of multi-rotor configurations. To do so, the solutions of the wind turbines are computed independently using several OpenFAST instances, performing its dynamic interaction through the floater. This method is applied to the single turbine Hywind concept and the twin-turbine W2Power floating platform, supporting NREL 5-MW wind turbines. The rigid-body response amplitude operators (RAOs) are computed and compared with other numerical tools. The results showed consistency in the developed framework. An agreement was also obtained in simulations with aerodynamic loads. This resulting tool is a complete time-domain aero–hydro–servo–elastic solver that is able to compute the combined response and power generation performance of multi-rotor systems.

Correction: Exact hydrodynamic solution of a double domain wall melting in the spin-1/2 XXZ model

Correction: Exact hydrodynamic solution of a double domain wall melting in the spin-1/2 XXZ model

Synergistic mixture of Capsicum annuum fruit extract/KI as an efficient inhibitor for the corrosion of P110 steel in 15 % HCl solution under hydrodynamic condition

Abstract The primary goal of this study is to discover a sustainable, renewable, and ecologically friendly anticorrosive inhibitor. Anticorrosion analysis of Capsicum annuum fruit extract (CAFE) was examined under hydrodynamic solution at 1500 rpm in 15 % on P110 steel. Results of the assessment showed that CAFE inhibits the corrosion of P110 steel and the rate of corrosion is significantly reduced on increasing its dosing amount. CAFE exhibits the maximum anticorrosive efficiency to 89.5 % (CAFE/800 mg/L) and 92.2 % (CAFE + KI/600 mg/L). The CAFE shows the chemical nature of inhibition effect. The maximum and minimum charge transfer resistance (R ct) and double layer capacitance (C dl) are 239.5 Ω cm−1 and 27 μF/cm2 with the addition of CAFE indicate the corrosion inhibition mitigation. The corrosion mitigation is caused by the adsorption of CAFE molecules on P110 steel surface via Temkin isotherm with chemical mechanism adsorption. The metal surface appearance was visualized via scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The interaction among the most active constituent i.e., Capsaicin (RCM) sulfate reducing bacteria (SRB) protein was examined by molecular docking. Additionally, an atomic level study of RCM was performed using DFT and MD.

Kinetic Equation Study on Momentum Conservation of Aerodynamics Incompressible Fluid of High-Altitude Aircraft

This paper introduces an integrated aerodynamic design method for aircraft based on numerical solution of hydrodynamics and electromagnetics equations. By using Pro/Engineer, ANSA, Fluent and MATLAB, the geometric shape, unstructured fluid mesh, hydrodynamic parameters and unpowered flight trajectory data of an aircraft were processed and calculated. In this paper, N-S equations are studied, and a test scheme for a hydrodynamic material aerodynamic model is established. Then, relevant parameters of the aircraft are tested and studied. The feasibility of this method for unsteady aerodynamics analysis of aircraft is verified.

On the design of stable, consistent, and conservative high-order methods for multi-material hydrodynamics

Obtaining stable and high-order numerical solutions for multi-material hydrodynamics is an open challenge. Although slope limiters are widely used to maintain monotonicity near discontinuities, typical limiting procedures violate closure laws at the discrete level when applied to multi-material hydrodynamics equations. Due to this, the high-order expansions of quantities related by the closure laws are no longer consistent. The commonly observed symptom of this consistency-violation is that the numerical method fails to maintain constant pressure and velocity across material interfaces. This leads to sub-optimal convergence rates for smooth multi-material problems as well. Specialized limiting procedures that satisfy consistency while maintaining conservation need to be developed for such equations. A novel procedure that re-instates consistency into slope-limited high-order discretizations applied to the multi-material hydrodynamics equations is presented here. Using simple examples, it is demonstrated that the presented method satisfies closure laws at the discrete level, while maintaining conservative properties of the high-order method. Furthermore, this procedure involves a projection step which relies on the compact basis of the underlying spatial discretization, i.e. for discontinuous schemes (viz. DG and FV) the projection is local, and does not involve global matrix solves. Comparisons with conventional approaches emphasizes the necessity of the consistent closure-law preserving limiting approach, in order to maintain design order of accuracy for smooth multi-material problems.

The nut-and-bolt motion of a bacteriophage sliding along a bacterial flagellum: a complete hydrodynamics model

The ‘nut-and-bolt’ mechanism of a bacteriophage-bacteria flagellum translocation motion is modelled by numerically integrating the 3D Stokes equations using a Finite-Element Method (FEM). Following the works by Katsamba and Lauga (Phys Rev Fluids 4(1): 013101, 2019), two mechanical models of the flagellum-phage complex are considered. In the first model, the phage fiber wraps around the smooth flagellum surface separated by some distance. In the second model, the phage fiber is partly immersed in the flagellum volume via a helical groove imprinted in the flagellum and replicating the fiber shape. In both cases, the results of the Stokes solution for the translocation speed are compared with the Resistive Force Theory (RFT) solutions (obtained in Katsamba and Lauga Phys Rev Fluids 4(1): 013101, 2019) and the asymptotic theory in a limiting case. The previous RFT solutions of the same mechanical models of the flagellum-phage complex showed opposite trends for how the phage translocation speed depends on the phage tail length. The current work uses complete hydrodynamics solutions, which are free from the RFT assumptions to understand the divergence of the two mechanical models of the same biological system. A parametric investigation is performed by changing pertinent geometrical parameters of the flagellum-phage complex and computing the resulting phage translocation speed. The FEM solutions are compared with the RFT results using insights provided from the velocity field visualisation in the fluid domain.