International Journal of Multiphase Flow最新文献

{"title":"3D-3C measurements of flow reversal in small sessile drops in shear flow","authors":"Clemens Bilsing ,&nbsp;Uwe Janoske ,&nbsp;Jürgen Czarske ,&nbsp;Lars Büttner ,&nbsp;Sebastian Burgmann","doi":"10.1016/j.ijmultiphaseflow.2024.105017","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105017","url":null,"abstract":"<div><div>Sessile drops play an important role in nature and the operation of many technical and biological systems as for instance fuel cells, cleaning processes, lab-on-a-chip devices and single-cell analysis. Nonetheless, their dynamic behavior in a shear flow is still not fully understood (e. g. detachment mechanism). Challenges exist regarding the precise simulation of two-phase flows as well as difficulties in conducting flow measurements with sufficient temporal resolution of more than 1 kHz. In this article, we present the first three-dimensional flow measurements in strongly oscillating drops stemming from a shear flow by using a monocular 3D localization microscope based on a Double-Helix Point Spread Function combined with Particle Tracking Velocimetry. The high temporal resolution and the large measurement volume - in terms of microscopy - make it possible to measure the time- and phase-averaged flow in small drops with Bond numbers (<span><math><mi>Bo</mi></math></span>) smaller than 1. Water drops were placed in an air flow channel and measurements were conducted for Reynolds numbers (<span><math><msub><mrow><mi>Re</mi></mrow><mrow><mi>d</mi></mrow></msub></math></span>) from about 750 to 1700. Our measurements show that the results of previous investigations for drops with <span><math><mrow><mi>Bo</mi><mspace></mspace><mo>&gt;</mo><mspace></mspace><mn>1</mn></mrow></math></span> concerning vortex pattern and flow reversal inside the drop apply for smaller drops as well. In addition, we are able to reveal the three-dimensional flow structure and multiple vortex-pattern in time and space. We discover a periodic 3D vortical flow pattern that corresponds to the first and second eigenfrequency of the drop. Moreover, we demonstrate the potential of adaptive optics to correct measurement errors stemming from time-varying light refraction when conducting measurements through the fluctuating drop surface, in particular for opaque substrates. The results may help in understanding the coupling of inner and outer flow for sessile drops in shear flow which allows for an analysis of the onset motion of these drops, i.e. drop removal. Removal of sessile drops plays a crucial role in many applications, which includes among other things the water management of fuel cells where small drops with <span><math><mrow><mi>Bo</mi><mo>&lt;</mo><mn>1</mn></mrow></math></span> predominantly occur.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105017"},"PeriodicalIF":3.6,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572693","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental and theoretical study on liquid film thickness of upward annular flow in helically coiled tubes","authors":"Shuai Liu ,&nbsp;Li Liu ,&nbsp;Hanyang Gu ,&nbsp;Ke Wang","doi":"10.1016/j.ijmultiphaseflow.2024.105041","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105041","url":null,"abstract":"<div><div>The liquid film thickness is crucial for studying the thermal hydraulic mechanism of the annular flow region in helically coiled tubes (HCTs). This paper introduces a refined experimental study on the liquid film thickness of annular flow in HCTs, utilizing a newly developed liquid film sensor. The experimental results indicate that the smaller coil diameters and pitches result in thinner average liquid film thicknesses. The average liquid film thickness decreases with increasing superficial gas velocity and decreasing superficial liquid velocity. However, the liquid film thickness at different circumferential positions on the cross-section of the tube exhibits varying sensitivities to superficial gas and liquid velocities. The experimental data reveal that the existing typical correlation formula for the average liquid film thickness of annular flow in straight tubes does not apply to HCTs. Consequently, a new prediction model is proposed for the average liquid film thickness of the annular flow region in HCTs, based on the modified Froude number, modified Dean number, Ekman number, and Reynolds number. This model comprehensively incorporates the structural characteristics of HCTs and fluid properties, and its validity is verified through the utilization of available and current data in the literature.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105041"},"PeriodicalIF":3.6,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dispersion and particle pressure in sedimenting suspensions with hydrodynamic interactions and particle inertia","authors":"Filipe Henrique ,&nbsp;Francisco Ricardo Cunha","doi":"10.1016/j.ijmultiphaseflow.2024.105037","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105037","url":null,"abstract":"<div><div>Particle inertia is a feature of suspension dynamics that is often neglected. However, its neglect changes the order of the governing equations of particle motion. In this work, we examine the impact of the inertia of particles over their velocity fluctuations and the resulting stresses. In order to observe effects of particle inertia, we consider dusty-gas suspensions of spherical weakly Brownian microparticles sedimenting in a Newtonian fluid at low Reynolds numbers. We first investigate the motion of a single spherical particle. The simulations for this simple case allow us to define the appropriate physical parameters of the flow and to validate the numerical calculation of velocity statistics over a range of Péclet and Stokes numbers. Next, we perform Langevin dynamics simulations with periodic boundary conditions to integrate the equations governing the translational and rotational motions of <span><math><mi>N</mi></math></span> hydrodynamically interacting particles suspended in the viscous fluid. The first aim of this paper is to examine the behavior of the velocity variance of inertial particles, with small fluctuations produced by Brownian motion at the moderate Péclet numbers. The interplay between mild Brownian forces and hydrodynamic interactions decreases the anisotropy of velocity fluctuations observed in non-Brownian suspensions (Pe<span><math><mo>≫</mo></math></span>1) of sedimenting particles. The simulation results suggest that particle inertia attenuates the magnitude of velocity fluctuations produced by both Brownian motion and viscous hydrodynamic interactions. Additionally, we study the long-time behavior of the velocity fluctuations by calculating their autocorrelation functions and the particle diffusivities. The numerical simulations show clear evidence of particle pressure arising from the flow disturbance produced by hydrodynamic interactions in a suspension. From the particle velocity variance obtained in the present numerical simulations, we propose a simple model for particle-phase pressure as a linear function of the particle volume fraction <span><math><mrow><mi>ϕ</mi><mo>⩽</mo><mn>5</mn><mtext>%</mtext></mrow></math></span>, which is usually a closure quantity required in models of more complex particulate systems such as fluidized beds.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105037"},"PeriodicalIF":3.6,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exposure of fractal aggregates to accelerating flows at finite Reynolds numbers","authors":"Akash Saxena ,&nbsp;Jean-Sébastien Kroll-Rabotin ,&nbsp;R. Sean Sanders","doi":"10.1016/j.ijmultiphaseflow.2024.105018","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105018","url":null,"abstract":"<div><div>Breakup of small aggregates is governed by the imbalance of imposed hydrodynamic forces and cohesive forces between constituent particles. Aggregate restructuring in ramped shear flows at infinitely low Reynolds number are known to reinforce aggregates, increasing effective cohesive strength. However, non-negligible flow inertia is known to increase breakage rates, and is expected to affect breakage kinetics under finite Reynolds number conditions in accelerated flows.</div><div>A numerical investigation was conducted to establish the effect of flow acceleration on aggregate evolution. Aggregates were characterized by their size, structure and interparticle forces. Individual aggregates were subjected to accelerating flows imposed through shear stresses at the boundaries, and their structural evolution along with breakage events were recorded. Particles were tracked with Discrete Element Method. The flow was solved using a Lattice Boltzmann method, and two-way coupling between the solid and liquid phase was achieved through an Immersed Boundary Method.</div><div>The findings show that although aggregates restructure due to the shear flow, their structure at breakage does not depend on shear stress. Increasing flow acceleration is found to slow down aggregate breakage and rotation, despite higher imposed shear stresses at the boundaries of the domain. The observed delays is found to be a transient effect of flow inertia around the aggregates. The reported findings establish a novel addition to the criteria for aggregate breakage, where, along with shear strength of the aggregates, flow accelerations and Reynolds number at the scale of the aggregates must also be considered.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105018"},"PeriodicalIF":3.6,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sensitized Reynolds stress modeling of a bubbly jet emerging into a water cross-flow","authors":"Ivan Joksimović,&nbsp;Suad Jakirlić","doi":"10.1016/j.ijmultiphaseflow.2024.105029","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105029","url":null,"abstract":"<div><div>The present work is concerned with the computational study of an air–water mixture stream emanating from a nozzle submerged in a water cross-flow inside a rectangular open channel to form a curved, intensively dispersed, bubbly jet. The work focuses on evaluating the predictive performance of an eddy-resolving turbulence model applied to the described case of a multiphase gas–liquid flow system characterized by a variety of closely coupled phenomena, including: turbulence anisotropy-induced secondary motion, free surface flow, bubbly jet propagation, and the varying interaction dynamics of the carrier water flow with the air bubble dispersion. Correspondingly, an appropriately extended differential near-wall Reynolds stress model, which describes the dynamics of unresolved subscale structures within the Sensitized Reynolds-Averaged Navier–Stokes (RANS) computational framework, is currently used in conjunction with a two-way coupled Euler–Lagrange approach to simulate this gas-water bubbly flow, with the operating and boundary conditions following the experimental reference of Zhang and Zhu (2013). Accordingly, the conditions at the free surface are adequately derived for all components of the residual turbulence stress tensor and the corresponding length scale determining variable. It is shown that the statistics of the bubble phase can be accurately captured, and the proper-orthogonal-decomposition analysis of the dynamic properties of the flow reveals at least two large-scale transient effects associated with the bubbly jet. Furthermore, in the preliminary part of this work it is shown that the currently applied turbulence model can be successfully used to correctly capture the effects of Reynolds stress anisotropy in the single-phase open-channel configuration, representing the incoming flow field of the main two-phase flow configuration.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105029"},"PeriodicalIF":3.6,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cell-centered Lagrange+Remap numerical strategy for a multi-material multi-velocity model","authors":"B. Manach-Pérennou ,&nbsp;R. Chauvin ,&nbsp;S. Guisset ,&nbsp;A. Llor","doi":"10.1016/j.ijmultiphaseflow.2024.105030","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105030","url":null,"abstract":"<div><div>The present work is devoted to the numerical approximation of multi-material flows. The so-called 6-equation system is considered where each material has its own velocity but shares the same pressure with the rest of the mixture. This model is a necessary building block as dissipation is completely removed outside of shocks. A numerical scheme is then presented and extends the classical “Lagrange+Remap” strategy to a multi-velocity setting. Entropy considerations are the focal point of its derivation as a mean of stabilizing results, ensuring thermodynamical consistency and selecting shocks of interest. Finally the scheme’s robustness and ability to deal with the inner stiffness of contrasted mixtures are evaluated on several test cases.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105030"},"PeriodicalIF":3.6,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cyclic flow cut-off characteristics of gas-liquid two-phase flow in pipeline-riser system and prediction of its occurring condition","authors":"Tianyu Liu,&nbsp;Suifeng Zou,&nbsp;Hanxuan Wang,&nbsp;Luhan Xu,&nbsp;Liejin Guo","doi":"10.1016/j.ijmultiphaseflow.2024.105042","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105042","url":null,"abstract":"<div><div>In offshore oil and gas fields, the prediction of gas-liquid two-phase flow pattern is of great importance for the design and operation of pipeline-riser systems. However, no special attention was put on the mechanism of periodic flow cut-off at the riser outlet, which is an inherent characteristic of certain flow patterns directly related to operation safety, in the study of flow pattern transition. In this study, differential pressure signals are used to explore the internal correlation between the flow cut-off of gas and/or liquid phase at the riser bottom and the riser outlet. The flow patterns are classified based on continuous flow or flow cut-off at the riser outlet. Then, the flow pattern transition mechanisms are studied from the view of the condition under which flow cut-off will appear. At high gas and low liquid velocities, the mechanism can be explained by a conventional theory; while at high gas and high liquid velocities, dissipation of hydrodynamic slugs becomes the major reason for flow pattern transition; and a unified model is introduced to predict the dissipation. At low gas and high liquid velocities, the condition for gas-liquid eruption can still describe the flow pattern transition, but it is modified by the slug dissipation model. At higher pressure, the lasting time of gas cut-off at the riser elbow becomes shorter, and a threshold can be set to decide whether it can be ignored. The predicted results are in good agreement with the flow pattern maps under different pipeline structures and fluid properties, and the reason why flow cut-off disappears in the experimental loop at high pressure of 10 MPa is successfully explained.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105042"},"PeriodicalIF":3.6,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142586228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrodynamic analysis of core annular flow with a viscoplastic lubricant","authors":"Ekta Tayal ,&nbsp;Subhabrata Ray ,&nbsp;Chirodeep Bakli ,&nbsp;Gargi Das","doi":"10.1016/j.ijmultiphaseflow.2024.105036","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105036","url":null,"abstract":"<div><div>Core annular flow (CAF) with viscoplastic lubrication (VPL) is an attractive proposition for pipeline transportation of high viscous oil, slurries and suspensions. Past studies have performed stability analysis to show that the unyielded zone at the liquid-liquid interface stabilizes CAF by suppressing interfacial instabilities. However, an in-depth investigation of the flow hydrodynamics and the conditions which reduce the pumping power within stable CAF range using VPL has not been reported till date. Moreover, most of the studies have considered a Bingham Plastic liquid in the annulus. Only a single study (Usha &amp; Sahu, 2019) is reported with Herschel-Bulkley (HB) liquid in the annulus that considers the entire annulus to be in the shear zone. Another experimental study (Huen et al., 2007) has demonstrated stable core annular flow with a shear thinning core and a HB annulus. In the present work, we analyze viscoplastically lubricated CAF for a Newtonian core where the yield stress annular liquid is described by the generalized HB model. The simplified analysis can predict CAF stability and is further explored to (i) assess the efficacy of VPL for stable energy-efficient oil transportation, and (ii) enhanced throughput without clogging during suspension transportation. The analysis, validated against data from literature, unravels the influence of rheological properties on flow hydrodynamics. We note that an annular liquid with low flow behavior index, <span><math><mrow><mspace></mspace><mi>n</mi></mrow></math></span> and yield stress, <span><math><msub><mi>τ</mi><mi>y</mi></msub></math></span> lowers pumping power, but the yield stress should be sufficient to form a plug zone at the interface for suppressing instabilities and stabilizing CAF. For viscous oil, a phase diagram in dimensionless coordinates (Reynolds number of the oil core and Herschel-Bulkley number of the annular liquid, both expressed at the inlet conditions) suggests the range of operation where an available HB liquid can serve as an effective annular lubricant for energy-efficient transportation.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105036"},"PeriodicalIF":3.6,"publicationDate":"2024-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572454","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"CFD study of propeller tip vortex cavitation","authors":"Yu-Xin Zhang ,&nbsp;Yue-Xing Zhu ,&nbsp;Lei Zhang ,&nbsp;Zheng-Tong Yang ,&nbsp;Yu-Long Li","doi":"10.1016/j.ijmultiphaseflow.2024.105020","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105020","url":null,"abstract":"<div><div>Tip vortex cavitation (TVC) caused by a marine propeller is a complex cavitating flow phenomenon, often featured by long helical trajectories making it challenging to simulate numerically. This paper presents a study on the CFD simulation of TVC with the focus on four key influence factors: mesh size, turbulence modeling, gas content, and Reynolds number. For the effect of mesh size, the simulations with different mesh refinement strategies show that the TVC is highly sensitive to mesh sizes and it is crucial to refine the mesh in the propeller wake. The adaptive mesh refinement method used in this study is shown to be effective in refining the mesh where the tip vortex locates. Compared with RANS (Reynolds averaged Navier-Stokes equations) method, IDDES (Improved Delayed Detached Eddy Simulation) method produces a noticeably better result since the dissipation of the tip vortex in the IDDES simulation is weaker. To suppress the dissipation of the tip vortices, vorticity confinement (VC) method is applied. The VC method significantly improved the TVC trajectory prediction for IDDES simulation, even with a less refined mesh, but it is not effective for RANS simulation. The effect of gas nuclei in water is considered by utilizing an Euler-Lagrangian method combined with a modified Schnarr-Sauer cavitation model in which a group of Lagrangian gas bubbles are used to model the non-condensable gas. The improvement on the TVC trajectory is notable by considering the air bubble effect. The effect of Reynolds number on TVC simulation is discussed by modifying the propeller's rotational speeds. Results show that the high Reynolds number gives a stronger tip vortex thus resulting in a longer TVC trajectory, but the improvement is limited compared with the effect of the other three influence factors.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105020"},"PeriodicalIF":3.6,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental research on self-amplifying density waves in horizontal pipelines of two phase granular slurries: Measurements on the effect of particle diameter and concentration","authors":"Edwin de Hoog ,&nbsp;Oscar van der Ven ,&nbsp;Rudy Helmons ,&nbsp;Arno Talmon ,&nbsp;Cees van Rhee","doi":"10.1016/j.ijmultiphaseflow.2024.105027","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105027","url":null,"abstract":"<div><div>Self-amplifying density waves in hydraulic transport pipelines is a scarcely researched topic. Density waves are in essence the result of a spatial redistributing effect and clustering of solids in hydraulic transport pipelines. Self-amplifying density waves are very undesirable for practical applications, as these waves increasing the risk of pipeline blockages. The two available experimental studies (Talmon et al., 2007; Matoušek and Krupička, 2013) report conflicting properties of the density waves, such as wave length and wave celerity. This new experimental research aims to shed light on the reported differences, by broadly varying particle size and concentration in a new dedicated experiment. The main highlight of this research is that two separate mechanisms were identified that can cause density waves, and Talmon et al. (2007) and Matoušek and Krupička (2013) in hindsight were studying the two different mechanism respectively. Both wave type mechanisms come into effect at mixture velocities close to the deposit limit velocity, and require a stationary bed layer to initiate. The first mechanism is caused by an imbalance of erosion and sedimentation of the bed layer, which is predominant for fine sand particles (<span><math><mrow><mo>∼</mo><mn>242</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span> and <span><math><mrow><mo>∼</mo><mn>308</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span> in this research). The second mechanism occurs when the bed layer starts sliding, instead of being eroded, and is specific for larger sand sizes (<span><math><mrow><mo>∼</mo><mn>617</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span> and <span><math><mrow><mo>∼</mo><mn>1</mn><mo>.</mo><mn>08</mn><mspace></mspace><mi>mm</mi></mrow></math></span> in this research). These two mechanisms are clearly distinguishable, having different wave lengths, celerity, amplitudes and amplification rates. The results also show a clear relationship between the mean concentration of a density wave, the wave amplitude and wave celerity specific for each of the two mechanisms.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"181 ","pages":"Article 105027"},"PeriodicalIF":3.6,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142526771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}