Flow Generation Research Articles

Visualization and prediction of the pleura and thoracic duct: elucidation of changes due to respiration using arterial landmarks and CT images

PurposeThe thoracic duct uses the pulsation of accompanying arteries to facilitate lymphatic flow. However, the lymphatic flow mechanism cannot be explained when it does not accompany the arteries. This study aimed to clarify the anatomical position of the thoracic duct and surrounding structures and determine the differences in the thoracic duct length and course during inspiration and expiration.MethodsSix cadavers were dissected to observe the positional relationship between the thoracic duct and surrounding structures. Image sequences of anatomical sections from the Visible Korean Human Open Resource were observed and reconstructed to understand their three-dimensional positioning. Inspiratory and expiratory computed tomography scans were used to measure and examine respiratory variations in the distance between the arterial landmarks to predict the thoracic duct length.ResultsThe thoracic duct accompanied the arteries for most of its course and was sandwiched between the arteries and pleura, entering the mediastinum. However, there was an area on the cranial side of the aortic arch where the thoracic duct did not accompany the arteries. The distance between the arterial landmarks in this area, which approximate the thoracic duct length, was significantly longer during inspiration (39.3 ± 7.81 mm) than during expiration (31.49 ± 7.01 mm).ConclusionThis study suggests that the pleura entering the mediastinum pushes the thoracic duct toward the arteries to promote lymphatic flow generation by arterial pulsation. Additionally, this study suggests that the lymphatic flow in the thoracic duct is generated by the expansion and contraction of the thoracic duct with respiratory movement.

Dynamics and hazards of pyroclastic avalanches at Etna volcano (Italy)

We present a multidisciplinary research aimed at quantifying the conditional probabilities for hazards associated with pyroclastic avalanches at Etna, which combines physical and numerical modeling of granular avalanches and probabilistic analysis. Pyroclastic avalanches are modeled using the depth-averaged model IMEX-SfloW2D, which is able to simulate the transient propagation and emplacement of granular flows generated by the collapse of a prescribed volume of granular material. Preliminary sensitivity analysis allowed us to identify the main controlling parameters of the dynamics, i.e. the total avalanche mass, the initial position of the collapsing granular mass (and the associated terrain morphology), the initial avalanche velocity, and the two rheological parameters which determine the mechanical properties of the flow. While the first two parameters can be considered as “scenario parameters” in the definition of the hazards, the initial velocity and the rheological parameters need to be calibrated. We therefore adopted a methodology for the statistical calibration of the physical model parameters based on field observations. We used data from the pyroclastic avalanche that occurred on February 10, 2022 at Etna, for which we had an accurate mapping of the deposit and some estimates of the total mass and the initial volume. We then run a preliminary ensemble of numerical simulations, with fixed initial volume and position, to calibrate the other input parameters. Based on the accuracy of the matching of the simulated and observed deposits (measured by the Jaccard Index), we extracted from the simulation ensemble a subsample of equally probable combinations of initial velocities and rheological parameters. We then built an ensemble of model input parameters, with varying (i) avalanche volumes, (ii) initial positions, (iii) velocity, and (iv) rheological coefficients. The initial volume range was chosen within the range of observed pyroclastic avalanches at Etna (i.e., between 0.1 and 3 × 106 m3), using a prescribed probability distribution extracted from the literature data. The initial positions have been chosen on the flanks of the South East Crater of Etna, with homogeneous spatial distribution. The initial velocity and the rheological coefficients were chosen from the subsample created with the calibration. Finally, a semi-automatic procedure (digital workflow) running the Monte Carlo simulation allowed us to produce the first probabilistic map of pyroclastic avalanche invasion at Etna. Such a map, conditional to the occurrence of a pyroclastic avalanche event, can be used to identify the hazardous areas of the volcano and to plan mitigation measures.

Numerical assessment of heat transfer and entropy generation of a mixed convection ferrofluid flow under the effect of a non-uniform magnetic field

Numerical assessment of heat transfer and entropy generation of a mixed convection ferrofluid flow under the effect of a non-uniform magnetic field

High-Pressure Hydrogen Charge Check-Valve Energy Loss-Based Correlation Analysis Affecting Internal Flow Characterizations

In this study, we analyzed changes in flow characteristics and energy-dissipation characteristics due to changes in hydrogen temperature and inlet/outlet differential pressure in a check valve, which affect the storage safety and reliability of high-pressure hydrogen refueling systems. The effects of flow separation and recirculation flow generation at the back end of the valve were investigated, and the pressure, flow rate, pressure coefficient, and energy dissipation at the core part (where the hydrogen inflow is blocked) and the outlet part (where the hydrogen is discharged) were numerically analyzed. The hydrogen-inlet temperature (Tin) was selected as 233 K, 293 K, and 363 K, and the differential pressure (∆P) was selected in the range of 2 to 10 MPa in 2 MPa steps. To ensure the reliability of the numerical results, mesh dependence was performed, and the effect of the mesh geometry on the results was less than 2%. The numerical simulation results showed that the hydrogen introduced into the core part is discharged into the discharge part, and the pressure decreases by up to 6% and the velocity increases by up to 16% at the 95 mm position of the L-shaped curved tube. In addition, for the hydrogen-inlet temperature of 233 K in the L-shaped curved tube, the flow velocity decreases by up to 60% and the pressure coefficient increases at the 2.3 mm point in the Y-axis direction, indicating that the main flow area is biased towards the bottom of the valve due to the constriction of the veins caused by flow separation. The TDR results showed that the hydrogen discharge to the discharge region increased by 96% at 95 mm compared to 90 mm, and the turbulent kinetic energy of the hydrogen was dissipated, resulting in a temperature increase of up to 4.5 K. The exergy destruction was maximized in the core region where flow separation occurs, indicating that the pressure, velocity, and TDR changes due to flow separation and recombination have a significant impact on the energy loss of the flow in the check valve.

Numerical Analysis of Magnetohydrodynamics Mixed Convection and Entropy Generation in a Double Lid‐Driven Cavity Using Ternary Hybrid Nanofluids

AbstractThe present study numerically investigates the effects of a magnetic field on mixed convection flow and entropy generation within a double lid‐driven square cavity filled with a hybrid nanofluid. The flow is induced by two isothermally heated semi‐circles located on the bottom and left walls of the cavity. The cavity is filled with a ternary composition of hybrid nanofluid (aluminum oxide/silver/copper oxide‐water) and is exposed to a uniform magnetic field. The velocity ratio of the moving lids and the radius ratio of the semi‐circles are key parameters in the analysis. The study employs the finite volume method and full multigrid acceleration to solve the coupled continuity, momentum, energy, and entropy generation equations, along with the relevant boundary conditions. Key dimensionless parameters considered include the Hartmann number (0 ≤ Ha ≤ 100), Richardson number (0.01 ≤ Ri ≤ 1), hybrid nanofluid volume fraction (3% ≤ ϕ ≤ 12%), internal semi‐circle radius ratio (β = 0.5 and 1), and velocity ratio (−2 ≤ λ ≤ 2). Results revealed that the optimal heat transfer is achieved for Ri = 0.04, Ha = 100, ϕ = 0%, β = 1, and λ = 0.5 with 63% enhancement. Moreover, the maximum entropy generation rates are obtained for the same parameters with a rate of 47%, reflecting the complex balance of enhanced heat transfer and associated irreversibility's. Results reveal also that heat transfer and entropy generation are a decreasing function of Hartmann number implying a suppress of fluid motion due to the Lorentz force. This study provides a valuable resource and parametric analysis for researchers and engineers, aiding in the design and optimization of thermal management systems for various industrial applications, including heat exchangers, nuclear reactors, and energy systems.

A first principles study of convection cells to shear flow instability in 2D Yukawa liquids driven by Reynolds stress

The stability of kinetic-level convection cells (wherein the magnitude of macroscopic and microscopic velocities are of same order) is studied in a two-dimensional Yukawa liquid under the effect of microscopic velocity perturbations. Our numerical experiments demonstrate that for a given system aspect ratio viz., the ratio of system length to its height and number of convective rolls initiated , the fate of the convective cells is decided by . For , Reynolds stress is found to be self-consistently generated and sustained, which results in tilting of convection cells, eventually leading to shear flow generation, whereas for , parallel shear flow is found to be untenable. An unambiguous quantitative connection between Reynolds stress and the onset of shear flow using particle-level data is established without free parameters. The growth rate of the instability, the role of frictional forces, generalization of our findings and the possibility of realizing the same in experiments are also discussed.

Analysis of heat transfer in magnetized Williamson fluid over a porous curved oscillating surface: Entropy generation

This paper provides an innovative idea to perform the analysis of entropy generation in the time-dependent flow of Williamson liquid toward an oscillating curvy porous surface. The characteristics of the transport phenomenon are improved by taking thermal and mass relaxation parameters in the energy and concentration equations respectively by utilizing a modulated form of Fourier and Fick laws known as Cattaneo–Christov heat and mass flux models. The mathematical form of the entire flow model is simplified by incorporating a curvilinear coordinate system. The obtained set of partial differential equations is then solved by the homotopy analysis method (HAM) which transforms them into convergent series form. The effects of various pertinent flow parameters on dimensionless pressure, entropy generation, velocity, and temperature fields are shown graphically. Furthermore, the variations in Sherwood number, skin friction coefficient, and local Nusselt number are presented in tabular form. It is observed from this study that the temperature and entropy generation increase with the radius of curvature parameter.

Optimization of In-Motion EV Charging Infrastructure for Power Systems Using Generative Adversarial Network-Based Distributionally Robust Techniques

This paper presents an innovative optimization framework for the co-management of dynamic electric vehicle (EV) charging lanes and power distribution networks, addressing grid stability amidst fluctuating EV charging demands. Integrating generative adversarial networks (GANs) and distributionally robust optimization (DRO), the framework models uncertainties in traffic flow and renewable energy generation, optimizing system performance under worst-case conditions to mitigate risks of grid instability. Applied to a highway with eight dynamic charging lanes (500 kW per lane), serving up to 50 EVs simultaneously, the framework balances energy contributions from 15 renewable generators (60% of the mix) and 10 non-renewable generators. Simulation results highlight its effectiveness, maintaining grid stability with voltage deviations within 0.02 p.u., reducing energy losses to under 0.8 MW during peak traffic (1500 vehicles per hour), and achieving 95% lane utilization. Dynamic charging enabled EV users to save USD 0.08 per kilometer through reduced stationary charging downtime, optimized travel efficiency, and lower energy costs. Additionally, the system minimizes maintenance costs by optimizing lane and grid reliability. This study underscores the potential of GAN-based DRO methodologies to enhance the efficiency of power grids supporting dynamic EV charging, offering scalable solutions for diverse regions and traffic scenarios.

Optimization of Heat Transfer on Carbon Nanotubes With Exponential Heat Generation and Nonlinear Radiation in Sakiadis and Blasius Flows Over Curved Surface

ABSTRACTEngineers and researchers in the field of thermal analysis are searching for novel approaches to boost their performance by enhancing the thermal characteristics of electrical equipment. Non‐Newtonian fluids are used in technical and industrial settings owing to their high thermal conductivity. In connection with this, the present study investigates the fluid flow and heat transmission of a hybrid nanomaterial (carbon nanotubes and ferric oxide) over a curved surface. The originality of this study is related to examining the impact of heat generation and nonlinear thermal radiation with convective boundary conditions for Sakiadis flow (SF) and Blasius flow (BF). The system of mathematical relations in the partial differential equation form is changed to an ordinary differential equation (ODE) system using appropriate variables. The indeterminate ODEs were solved using the ODE analyzer, which is accessible in the computer software Maple. The graphs demonstrate the importance of the critical factors concerning the velocity and temperature fields. SF has a thinner boundary layer than BF, which results in a more pronounced temperature drop. The effects of altering the physical parameters on the Nusselt number were optimized through response surface methodology for BF and SF. SF is more affected by radiation effects, but BF shows increased sensitivity to wall temperature gradients, indicating distinct optimization approaches for each scenario. In every situation, the hybrid nanofluid of multiwall carbon nanotubes and ferric oxide exhibits excellent thermal performance. To validate the chosen numerical approach, a tabular description is provided to generate an excellent comparison.

A universal geography neural network for mobility flow prediction in planning scenarios

AbstractThis study primarily focuses on generating mobility flow in regions and cities, which plays an important role in urban planning and management. The majority of existing mobility flow models, including conventional statistical models and deep learning‐based models, are heavily dependent on historical data to predict future mobility flows. The application of these models poses significant challenges in the planning and construction of emerging cities and regions, particularly in developing countries experiencing swift urbanization. These challenges are exacerbated by a dearth of historical data and rapid shifts in mobility patterns. Consequently, the scenario necessitates a mobility flow generation model capable of generating flows without historical data. This study introduces the universal geography neural network, an algorithm designed to glean potential patterns in human mobility across diverse cities and temporal spans. This is achieved through the analysis of substantial quantities of location‐based data, resulting in the generation of mobility flows within a city. Our experiment, designed to extract various features and generate fine‐grained mobility flows in the testing set, outperforms both traditional models and state‐of‐the‐art deep learning models. Moreover, our model has proven capable of generating reliable results across various time periods and grid areas.

Heart-retina time analysis using electrocardiogram-coupled time-resolved dynamic optical coherence tomography

The eye and the heart are two closely interlinked organs, and many diseases affecting the cardiovascular system manifest in the eye. To contribute to the understanding of blood flow propagation towards the retina, we developed a method to acquire electrocardiogram (ECG) coupled time-resolved dynamic optical coherence tomography (OCT) images. This method allows for continuous synchronised monitoring of the cardiac cycle and retinal blood flow dynamics. The dynamic OCT measurements were used to calculate time-resolved blood flow profiles using fringe washout analysis. The relative fringe washout was computed to generate the flow velocity profiles within arterioles at the optic nerve head rim. We found that the blood column between the heart and the retina propagates within one cardiac cycle, denoting the arrival time as the heart-retina time (HRT). In a group of healthy subjects, the HRT was 144 ± 19 ms (mean ± SD). The HRT could provide a novel potential biomarker for cardiovascular health in direct relation to retinal perfusion.

Solitary wave structure of transitional flow in the wake of a sphere

The soliton-like coherent structure (SCS), which has been verified to exist in both transitional and turbulent boundary layers [Y. S. Kachanov, “Physical mechanisms of laminar-boundary-layer transition,” Annu. Rev. Fluid Mech. 26, 411–482 (1994); C. Lee, “New features of CS solitons and the formation of vortices,” Phys. Lett. A 247, 397–402 (1998); C. Lee and J. Z. Wu, “Transition in wall-bounded flows,” Appl. Mech. Rev. 61, 030802 (2008); and C. Lee and X. Jiang, “Flow structures in transitional and turbulent boundary layers,” Phys. Fluids 31, 111301 (2019)], still poses a challenge in the understanding of its formation and behavior. In our previous study [Niu et al., “Turbulence generation in the transitional wake flow behind a sphere,” Phys. Fluids 36, 034127 (2024)], the SCS was also found to exist in the transitional wake flow behind a sphere. In the present study, the formation and evolution of the SCS is further investigated at various Reynolds numbers by numerical simulation. The results show that at the early stage of the turbulence transition, the SCS appears as a form of wave packet during the Tollmien–Schlichting (T–S) wave stage. With the increase in the Reynolds number, the SCS reaches its maximum amplitude downstream where the velocity discontinuity occurs. This position is located after the breakdown of the T–S wave and the three-dimensional structure is formed. Then, the SCS conserves its shape and amplitude over a long distance downstream. The relationships among the SCS, the spikes, the vortex structures, and the high-shear layers are further analyzed. It is found that the SCS in the wake flow has similarities to the phenomena observed in boundary layer flows during the turbulent transition. The vortex structures and high-shear layers mostly wrap around the border of the SCS. The vortex structure is considered to be a consequence of the development of the SCS rather than its cause.

Analytical approach to control the irreversibilities in a chemically reactive nanofluid flow over a Darcy–Forchheimer medium with nonuniform heat source/sink

AbstractIn real‐world processes, such as heat transfer, fluid flow, and chemical reactions, irreversibility occurs frequently, which induces an augment in entropy. The optimization of the entropy generation in a mechanical system is one of the fundamental areas of research to channel the energy of the system for utilization. This research exhibits an entropy generation in a nanofluid flow drenched in a fluid‐saturated non‐Darcy porous medium toward a stagnation point. The flow line also experiences the existence of nonuniform heat generation/absorption following the first‐order chemical reaction, which enhances the applicability of this model in different domains of science and engineering. A special form of the Lie group approach is applied to revert the governing partial differential system into its self‐similar ordinary differential form. The solutions of the transformed nonlinear ODEs are acquired analytically through the DTM ‐Padé as well as numerically by the Runge–Kutta–Fehlberg (RKF‐45) method coupled with the shooting process. The fallouts are vividly sketched graphically. One of the upshots reveals that the escalation of space and temperature‐reliant heat absorption parameters can optimize the thermal irreversibility of the system and so as the total entropy generation. Meanwhile, by incrementing the Darcy parameter from 0 to 0.8, the wall shear stress decays by 23.7%, whereas with the same hike in the Forchheimer resistance factor, declines the rate of heat and mass transfer approximately by 2.6% and 3.6%, respectively. Another upshot reveals that with the escalation of the space‐dependent heat source parameter from 0.1 to 0.5, the Nusselt number significantly decreased by 23.9%. Meanwhile boosting the temperature‐reliant heat sink parameter from ‐0.1 to ‐0.5 causes an inclination in the rate of heat transportation by 10.5%. Moreover, it is found that mass transport irreversibility can be controlled by enhancing the constructive chemical reaction rate. We hope that this study will be beneficial for many engineering and industrial processes, particularly in geothermal energy extraction, nuclear waste disposal management, groundwater filtration machinery and food processing equipment.

Entropy generation and heat convection analysis of second-grade viscoelastic nanofluid flow in a tilted lid-driven square enclosure: A finite difference approach

Entropy generation and heat convection analysis of second-grade viscoelastic nanofluid flow in a tilted lid-driven square enclosure: A finite difference approach

Spontaneous net flow generation using passive artificial cilia in the nucleate boiling region

The occurrence of spontaneous net flows in nature is fascinating. Here, we report spontaneous net flow generation using passive artificial cilia consisting of directional fabric in the nucleate boiling regime. Surprisingly, by placing simple ordinary flocking rayon fibers at an angle of approximately 18 degrees on a base cloth on the circular wall in a container as the artificial cilia, we observed the circular flow of the angular velocity of up to ∼2 rad/s (the average velocity of up to ∼34 mm/s) in the nucleate boiling regime. Moreover, by the observation of a high-speed camera (960 fps), we found that the bubbles rise obliquely at a high velocity of about 80–180 mm/s, which drives the net flow. Our findings should contribute to a better understanding of spontaneous flows in nature and should be applied to utilize unused heat, such as factory waste heat effectively.

A non‐rigid point cloud registration method based on scene flow estimation

AbstractPoint cloud registration is an important aspect of computer vision, encompassing various applications. However, many existing algorithms neglect the registration of non‐rigid point cloud. Recent studies have focused on scene flow, which can achieve non‐rigid point cloud registration by estimating the scene flow of two point clouds. The presence of occlusion in a scene is primarily attributed to variations in viewpoint and access time, thereby posing a significant challenge in accurately predicting scene flow. In the endeavour to mitigate this issue, the focus is on the propagation of scene flow originating from non‐occluded points towards occlusion points while concurrently estimating the occlusion map. The proposed network, a non‐rigid point cloud registration method based on scene flow estimation, achieves exceptional performance for the EPE3D metric on the FlyingThings3D and KITTI scene flow datasets, and it demonstrates strong generalization on the railroad dataset.

An explicit peridynamics model for hydraulic fracturing in porous media

PurposeThe purpose of this paper is to systematically investigate the hydraulic fracture branching phenomena in porous media under different loading conditions and the stepwise phenomenon. The effect of the pore pressure in hydraulic fracturing branching is studied, and more evidence for the stepwise phenomenon with the peridynamics approach is provided.Design/methodology/approachA fully coupled fluid-filled explicit peridynamics model is developed to simulate the complex evolution of crack branching and stepwise phenomena in saturated porous media. Based on the peridynamics theory, an explicit time integration scheme is used to solve the coupled equation system including rock deformation, fluid flow and fracture propagation. Using the proposed model, a series of peridynamic computational tests are performed to examine two common kinds of phenomena observed in hydraulic fracturing: the crack branching phenomenon and the stepwise phenomenon.FindingsFor crack branching phenomenon, the results obtained indicate that sufficient loading is required in order to initiate the crack branching process. Compared with the stress applied on crack surfaces condition, crack branching is more easily induced with the stress applied on boundaries. In addition, for the fluid-driven crack (stress applied on crack surfaces), the existence of pore pressure will depress the growth and branching of the crack. For stepwise phenomena, the results obtained indicate that the peridynamics is a promising tool to study the stepwise phenomenon. The stepwise phenomenon is more distinct under mechanical loading conditions due to the solid behaviour. A sudden jump or crack extension will happen when enough energy is accumulated in the hydraulic fracturing system.Research limitations/implicationsIn this study, the explicit method is used, which means it is conditionally stable, and the critical time step needs to be decided. The reason to use the explicit method is for the study purpose; the explicit method is faster and has no need for matrix inversions.Originality/valueThis study helps to understand the effect of the pore pressure in hydraulic fracturing branching and provides more evidence for the stepwise phenomenon with peridynamics.

Application of fluid dynamics in modeling the spatial spread of infectious diseases with low mortality rate: A study using MUSCL scheme

Abstract This study presents a comprehensive mathematical framework that applies fluid dynamics to model the spatial spread of infectious diseases with low mortality rates. By treating susceptible, infected, and treated population densities as fluids governed by a system of partial differential equations, the study simulates the epidemic’s spatial dynamics. The Monotone Upwind Scheme for Conservation Laws is employed to enhance the accuracy of numerical solutions, providing a high-resolution approach for capturing disease transmission patterns. The model’s analogy between fluid flow and epidemic propagation reveals critical insights into how diseases disperse geographically, influenced by factors like human mobility and environmental conditions. Numerical simulations show that the model can predict the evolution of infection and treatment population densities over time, offering practical applications for public health strategies. Sensitivity analysis of the reproduction number highlights the influence of key epidemiological parameters, guiding the development of more efficient disease control measures. This work contributes a novel perspective to spatial epidemiology by integrating principles of fluid dynamics, aiding in the design of targeted interventions for controlling disease outbreaks.

Numerical simulation of various flow regimes in water delivery systems

Transient flow frequently occurs in water delivery systems, including various flow regimes such as water hammer, free surface flow, and slug flow. Current models often oversimplify these phenomena by simulating single-phase flow or using simplistic one-dimensional assumptions for the gas-water interface, neglecting interface instability. Although two-fluid models can address some of these issues, they cannot simulate open channel flow and have not yet been applied to transient flow scenarios. To date, no single model has been able to simultaneously simulate all these flow regimes while overcoming these limitations. To address this gap, the two-fluid model is enhanced in this paper. For water hammer simulation, a gas volume fraction of zero is assumed, and a TVB unsteady friction model is introduced to enhance numerical accuracy. For open channel flow, a variable wave speed equation and a new state equation are presented. Despite the different state equations required for various flow regimes, a Roe-type scheme is introduced to solve the two-fluid model. This approach accurately simulates water hammer, free surface flow (including open channel flow and stratified flow), and slug flow. An experimental pipeline system is designed to validate the proposed model's ability to simulate water hammer. Additionally, several cases are used to verify the model's capability in simulating open channel flow, stratified flow, and slug flow. The model accurately predicts the occurrence of slug flow, consistent with experimental flow pattern maps, and effectively simulates the evolution of slug flow, closely matching the measured gas-water interface. The effects of gas volume fraction, pipe length, and pipe slope on slug flow are systematically discussed. Results indicate that smaller initial gas volume fractions, longer pipe lengths, and upward pipe slopes increase the likelihood of slug flow generation within the pipeline, which should be minimized during design. Abbreviations: TVB: Trikha-Vardy-Brown model; Cr: Courant number

Density-dependent flow generation in active cytoskeletal fluids

The actomyosin cytoskeleton, a protein assembly comprising actin fibers and the myosin molecular motor, drives various cellular dynamics through contractile force generation at high densities. However, the relationship between the density dependence of the actomyosin cytoskeleton and force-controlled ordered structure remains poorly understood. In this study, we measured contraction-driven flow generation by varying the concentration of cell extracts containing the actomyosin cytoskeleton and associated nucleation factors. We observed continuous actin flow toward the center at a critical actomyosin density in cell-sized droplets. The actin flow exhibited an emergent oscillation in which the tracer advection in the bulk solution periodically changed in a stop-and-go fashion. In the vicinity of the actomyosin density where oscillatory dynamics occur, the velocity of tracer particle motion decreases with actomyosin density but exhibits superdiffusive motion. Furthermore, the increase or decrease in myosin activity causes the oscillatory flow generation to become irregular, indicating that the density-dependent flow generation of actomyosin is driven by an interplay between actin density and myosin force generation.