Solid Motion Research Articles

Dynamics of partially collapsing pulsed fluidized bed

AbstractThe use of flow pulsation as an effective assisted fluidization technique has been suggested in a number of applications, such as drying of food and pharmaceutical products, dry beneficiation of coal, and deagglomeration of nanopowders, owing mainly to its cost‐effectiveness and ease of implementation. The efficacy of this technique is, however, greatly affected by the frequency of pulsation since it controls the collapse dynamics of the fluidized bed. In this study, using ultrafine hydrophilic nanosilica with strong agglomeration tendencies, the pulsation frequency was controlled to allow only partial collapse of the bed between two successive pulsations while the global and local dynamics in different bed regions were carefully monitored. Besides the usual advantages associated with assisted fluidization techniques, such as lower minimum fluidization velocity, higher bed expansion, and elimination of bed non‐homogeneities, the continuous and intense solid motion imparted by the partial bed collapse caused a more substantial increase in the overall pressure drop than the one obtained with the conventional unassisted fluidization. The results of the frequency domain analysis highlighted the fact that the effect of pulsation event was felt differently in different regions of the bed depending upon the amplitude of the pulsation. These results were further corroborated by the similarity analysis.

Solids back-mixing in the transport zone of circulating fluidized bed boilers

This work investigates the back-mixing of solids in the transport zone of large-scale circulating fluidized bed (CFB) boilers, with the aims of identifying and evaluating the governing mechanisms and providing a mathematical description based on a solid theoretical background rather than on purely empirical correlations. In addition, transient Direct Numerical Simulation (DNS) modeling is used to identify the mechanism that drives migration of the solids from the dilute up-flow in the core region to the down-flow at the furnace walls. Previously published concentration and pressure profiles are collated and analyzed through modeling of the steady-state mass balance of the dispersed solids in the transport zone. The study shows that solids back-mixing at the furnace wall layers is limited (hence governed) by the core-to-wall layer mass transfer transport mechanism rather than by the lateral movement of solids within the core region. The latter is shown by the 3-dimensional (3D) mass balance model, and the transient DNS modeling indicates that this is due to a turbophoresis mechanism. We also show that the use of Pe-numbers to describe the lateral solids dispersion is not straightforward but rather depends on the unit scale, and that Pe-numbers < 26 are needed to yield the solids back-mixing rates measured in large-scale CFB boilers. Finally, we propose a mathematical expression for the core-to-wall layer mass transfer coefficient derived from a Sherwood number (Sh)-correlation fitted to measured values of the characteristic decay constant that result from the solids back-mixing. This expression shows better agreement with the large-scale measurements than do the expressions given in the literature.

Multi-phase-field lattice Boltzmann model for polycrystalline equiaxed solidification with motion

The formation process of equiaxed structures during alloy solidification is a complicated multiphysics problem as it includes solid–liquid phase transformations, transport of solute and heat, liquid flow, solid motion, solid–solid interactions, and grain growth after solidification completion. In this study, a multi-phase-field (MPF) model with the double-obstacle (DO) potential is introduced to our previous model [T. Takaki et al., Comput. Mater. Sci., 147 (2018) 124–131] to express the formation process of equiaxed structures accurately and efficiently, from the growth of multiple mobile dendrites to the grain growth with grain boundary anisotropy after solidification. The accuracy of the resulting MPF-lattice Boltzmann (MPF-LB) model with the DO potential is evaluated by comparison with the results obtained using a model with the double-well potential through simulations of purely diffusive dendrite growth, the growth of an immobile dendrite with forced convection, and the growth of a mobile dendrite under shear flow. Finally, the model is applied to both large-scale polycrystalline solidification and semi-solid deformation processes.

Simulating fluid-structure interactions with a hybrid immersed smoothed point interpolation method

In this paper, a hybrid immersed smoothed point interpolation method (hybrid IS-PIM) is proposed, which employs a hybrid force approach to impose fluid-structure interaction (FSI) force condition. Compared with the original IS-PIM using a complete body force, the hybrid IS-PIM still utilizes the form of body force for pressure term to enhance the stability of numerical algorithm, and the shear force is applied to the boundary to accord with the physical law and the practical situation. Numerical examples have shown that the body force term enables the proposed method to overcome the constraint of mesh size ratio, and the boundary force term has a direct effect on the motion and deformation of solids, which yields more accurate results in comparison with the complete body force applied in the original IS-PIM. Moreover, the equivalence of FSI force in forms of body force and boundary force are also verified straightforwardly using a series of mesh combinations.

Research on Key Factors Influencing Surface Subsidence of Paste Backfilling Mining in Thick Coal Seam of Deep Mine

The research on the key factors of surface subsidence in paste backfilling mining of thick coal seam in deep mine is a complex system engineering, which involves mining, backfilling, support, subsidence, safety, and other aspects. At present, there is no systematic research on the key factors of surface subsidence in paste backfilling mining of thick coal seam more than 6 meters in a deep mine. In this paper, field research, laboratory experiments, theoretical analysis, and other research methods are used to carry out the research about 3# coal seam under buildings in the Lu’an area. The main conclusions are as follows: through the construction of the fuzzy extension model of surface subsidence in paste backfilling mining, five types of surface subsidence are obtained, including overburden structure, roof subsidence before backfilling, nonbackfilling account, the strength of filling body, and backfilling technology. It is the key factor to control the surface subsidence; the optimization measures are given to provide a reference for the reasonable design of paste backfilling mining in other working faces. The research conclusion has a certain reference value for solving a series of problems such as coal resources under buildings, solid waste disposal, controlling strata and surface movement, improving the recovery rate of mine resources, and extending the service life of mine.

Optimization of Geometrical Parameters of Fire Wood Fluidized Bed Burner

The aim of this work is to determine the dynamics of the firewood burning-out in the fluidized bed burners and to select the optimal constructive characteristics of the burner of the fluidized bed, which allows decreasing the unburnt fuel particles to be carried out of the burner volume. The aims and problems were solved using the experimental and numerical methods. Thus, to determine the dynamics of the burning-out, the experimental device was used with a fluidized bed, which is a 200x300 mm chamber 1000 mm high. The fuel mass of each combustion cycle was similar. It was 3.8 kg. The average time of burning-out during the combustion full cycle was in the range of 300-500 s, the maximum temperature of the layer was 800C. The studies performed showed that the major problem in the wood waste combustion is the insufficient time of the combustion process in the burner. This problem was proposed to be solved using the cone-shaped burner. The mathematical method was developed to determine the optimal main construction parameters (D is the top diameter, d is the bottom diameter and H is the cone height) of the burner accounting for the solid particle motion rate in the ascending flow. The devolatilization parameter of material was used as the optimization parameter. The most significant results are those cone-shaped geometrical parameters optimized in the research process. The significance of the results obtained is that the results of the above studies can be used in practice for designing the boilers with the fluidized bed burners.

A Layered Debris Disk around M Star TWA 7 in Scattered Light

Abstract We have obtained Hubble Space Telescope (HST) coronagraphic observations of the circumstellar disk around M star TWA 7 using the Space Telescope Imaging Spectrograph (STIS) instrument in visible light. Together with archival observations, including HST/NICMOS using the F160W filter and Very Large Telescope/SPHERE at the H-band in polarized light, we investigate the system in scattered light. By studying this nearly face-on system using geometric disk models and Henyey–Greenstein phase functions, we report a new discovery of a tertiary ring and a clump. We identify a layered architecture: three rings, a spiral, and an ≈150 au2 elliptical clump. The most extended ring peaks at 28 au, and the other components are on its outskirts. Our point-source detection-limit calculations demonstrate the necessity of disk modeling in imaging fainter planets. Morphologically, we witness a clockwise spiral motion, and the motion pattern is consistent with both solid body motion and local Keplerian motion; we also observe underdensity regions for the secondary ring that might result from mean-motion resonance or moving shadows: both call for re-observations to determine their nature. Comparing multi-instrument observations, we obtain blue STIS-NICMOS color, a STIS-SPHERE radial distribution peak difference for the tertiary ring, and a high SPHERE-NICMOS polarization fraction; these aspects indicate that TWA 7 could retain small dust particles. By viewing the debris disk around M star TWA 7 at a nearly face-on vantage point, our study allows for the understanding of such disks in scattered light in both system architecture and dust property.

Investigation of cluster property in the riser of circulating fluidized bed with a wide particle size distribution

In this work, the cluster dynamics in the riser of a pilot-scale circulating fluidized bed with the presence of wide particle size distribution (PSD) are numerically simulated via the multiphase particle-in-cell (MP-PIC) approach. Specifically, the gas and solid motions are tracked in the Eulerian and Lagrangian frameworks, respectively. The gas-solid numerical model is firstly validated with the experimental data. Then, the spatial distribution of particle clusters together with the cluster dynamics (velocity, length, aspect ratio) in the bed operating with different parameters are explored. The results demonstrate the ability of the MP-PIC model on predicting the important features of the cluster in the riser. Clusters mainly distribute in the lower part of the riser. The closer of the cluster to the riser wall, the larger vertical length, and larger aspect ratio appear. Moreover, the presence of riser outlet and solid inlet slightly affects the spatial distribution, the size and aspect ratio of clusters in the riser. The superficial gas velocity has an obvious impact on the cluster volume and the cluster vertical length, while the PSD width significantly affects the horizontal length and the aspect ratio. The results obtained in this work provide meaningful insights regarding the cluster dynamics in the riser, which will be beneficial to the deep understanding of this specific structure in the practical operation.

Influence of solids motion on ultrasonic horn tip erosion in solid–liquid two-phase flows

Ultrasound technology is a promising technique for wastewater treatment. However, its industrial application and scale-up face numerous problems, such as ultrasonic horn tip erosion. In solid–liquid flow systems, the synergy between cavitation and solid particle erosion is unclear, and the influence of solids motion is relatively unknown. By analyzing the tribosystem near the tip surface, we hypothesize that the synergistic erosion depends on the flux of solid particles flowing past the surface, relating to the local solids concentration and velocity. This hypothesis was investigated by ultrasonic cavitation–particle erosion tests performed in an eccentrically agitated tank. To study the effect of local concentrations and velocities, we carefully controlled the total solids and impeller speeds by integrating their coupled influence. Results indicate that synergistic erosion was aggravated at higher solids concentrations and velocities, and both parameters, based on a sensitivity analysis, show similarities in their relative degree of influence on erosion. This supports our hypothesis, which unifies the two parameters into a single factor, and explains the synergism in solid–liquid flows. Understanding these influencing factors and mechanisms will contribute to erosion prediction and the optimization of ultrasound applications in wastewater treatment processes.

CFD Modeling of Solid Inclusion Motion and Separation from Liquid Steel to Molten Slag

CFD Modeling of Solid Inclusion Motion and Separation from Liquid Steel to Molten Slag

Aerodynamic Simulation of a Standalone Round and Deforming Treaded Tire

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;For a typical passenger ground vehicle, the rotating treaded tires and wheel housings typically account for up to 25% of the total vehicle aerodynamic drag. Due to the importance of tires and their treads to the overall vehicle aerodynamics, it’s critically important for aerodynamics departments to have accurate simulations that can predict the effects of rotating tires. Accurate prediction of flow around a tire is a complex phenomenon and is affected by details of tire features such as tread pattern, air pressure, and tire deformation. In particular, the physics of the tire treads spatial movement and deformation (i.e. expansion, contraction, sidewall bulge, and squeezing of airflow) as the tires rotate and come in contact with ground, especially around the contact patch, is vitally important in determining accurate wheel wakes, underbody flow, and the overall wake of the vehicle. Recent developments have expanded an existing capability for simulating solid body motion to simulating a true deforming tire with accurate representation of tread motion, deformation, contact patch and sidewall bulge. The current study incorporates a Lattice Boltzmann method (LBM) based CFD solution using an Immersed Boundary method (IBM) to simulate and validate a realistically rotating and deforming standalone treaded tire. For ease of use, the solution doesn’t require the user to prescribe the motion and deformation of the tire, but rather automatically calculates the changes in time from a single stationary representation of the deformed tire. Simulations using this new capability demonstrate significant improvements over previously published results, which used round rotating treaded tires. Results are validated against previous wind tunnel experimental measurements. Further discussion on the effect of tire loading (i.e. bulge deformation) on wake results is also presented and discussed.&lt;/div&gt;&lt;/div&gt;

Experimental Study of Cuttings Transport with Non-Newtonian Fluid in an Inclined Well Using Visualization and Electrical Resistance Tomography Techniques

Summary Hole cleaning is a concern in directional and horizontal well drilling operations where drill cuttings tend to settle in the lower annulus section. Laboratory-scale experiments were performed with different non-Newtonian fluids in a 6.16-m-long, 114.3- × 63.5-mm transparent annulus test section to investigate cuttings transport behavior. This experimental study focused on understanding the cuttings transport mechanism in the annulus section with high-speed imaging technology. The movement of cuttings in the inclined annular section was captured with a high-speed camera at 2,000 frames/sec. Also, cuttings bed movement patterns at different fluid velocities and inner pipe rotations were captured with a digital single-lens reflex video camera. The electrical resistance tomography (ERT) system was used to quantify the cuttings volume fraction in the annulus. Different solid bed heights and cuttings movements were observed based on fluid rheology, fluid velocity, and inner pipe rotation. The mechanistic three-layer cuttings transport model was visualized with the experimental procedure. This study showed that solid bed height is significantly reduced with an increase in the inner pipe rotation. This study also identified that cuttings bed thickness largely depends on fluid rheology and wellbore inclination. The image from the high-speed camera identified a downward trend of some rolling particles in the annulus caused by gravitational force at a low mud velocity. Visual observation from a high-speed camera identified a helical motion of solid particles when the drillpipe is in contact with solid particles and rotating at a higher rev/min. Different cuttings movement patterns such as: rolling, sliding, suspension, helical movement, and downward movement were identified from the visualization of a high-speed camera.

A Review on Seismic Performance of L-Shaped Building Through Plan Irregularities

The patterns of sporadic structure development have quickly expanded because of tasteful and restricted accessibility of land. Past examinations have indicated that the structures with design abnormality are harmed under solid ground movement. Auxiliary inconsistencies are significant elements which decline the seismic exhibition of the structures. Structures having basic anomalies bring about the lopsided circulation of the story float, exorbitant twist, etc. The irregularity discussed here are about plan irregularity which is available in re-participant corners and torsional anomaly which is caused by abrupt changes in firmness and twist enhancement factor in building. This study is to propose a feasible solution to build this kind of structure in seismically active areas using analytical methods with the assistance of ETABS software. The analysis shall be done through a comparable static horizontal power technique and reaction range examination (dynamic investigation). The basic reactions will estimated regarding story displacement, inter-story drift ratio, torsional irregularity ratio, torsional diaphragm rotation, normalized base shear force, and overturning moment, which are also called seismic response demands. The structure will be analyzed and compare with different types of other shape plan.

THREE-DIMENSIONAL NUMERICAL ANALYSIS OF STAGGERED GROINS

Mahmuzlar, kıyıda katı madde hareketini engelleyerek, kıyıların mevcut durumunu korumak üzere inşa edilirler. Dalga hareketlerinin mevsimsel farklılık göstermesi, kıyıların değişimine neden olabilmektedir. Kıyıları korumak adına inşa edilen mahmuzlarla etkileşim halinde olan akımın hareketinin analiz edilmesi, kıyıların korunması açısından alınacak önemleri daha etkili kılacaktır. Bu çalışmada, farklı akım durumlarında deneysel olarak incelenen şaşırtmalı mahmuzların üç boyutlu sayısal modellemesi yapılmıştır. Sayısal modellemelerde, akımın hareketini tanımlayan, Navier Stokes ve süreklilik denklemleri, sonlu hacimler yöntemi kullanılarak çözülmüştür. Sayısal modellemelerde, türbülans viskozitesinin hesabında, Ayrılmış Girdap Simülasyon (Detached Eddy Simulation-DES) modeli ve su-hava arakesitinin belirlenmesinde ise akışkan hacimleri yöntemi kullanılmıştır. DES modeli kullanılarak elde edilen sayısal model sonuçları deneysel bulgularla karşılaştırılmış ve karşılaştırma sonucunda sayısal model sonuçlarının deneysel bulgularla oldukça uyumlu olduğu görülmüştür. Sonuç olarak, sayısal modelleme tekniklerinin şaşırtmalı mahmuz yapılarıyla etkileşimde bulunan akım problemlerinin çözümünde başarılı olduğu, farklı akım ve yapı koşullarında tekrar edilebilme imkânı sunmasından dolayı tercih edilebileceği belirlenmiştir.

Features of Aerosols Solid Particles Movement with Various Densities inside Ventilated Airspace of the Cladding Façade Systems

This article presents the results of a study of aerosols solid particles movement inside ventilated air space of the ventilation facade. Particles of pollutants in the form of solid aerosol particles penetrate inside the air space of the ventilated façade. In the scientific literature, studies of settling processes (downward movement) of pollutant particles are given. However, the patterns of their movement inside the ventilated facades structure have not been studied thoroughly. The calculation method proposed by the author makes it possible to establish the speed of aerosol solid particles movement inside the ventilated air space of the ventilation facade and establish whether the particles will move upward together with the air flow or will settle on the structural elements of the ventilation facade facing the ventilated air space, taking into account the air flow rate and its temperature, and the size and density of aerosol contaminants.

Full scale KCS self-propulsion simulation using different propulsion models

It is critical to be able to estimate the full-scale ship self-propulsion, since the more real sailing performance of the ship can be assessed. Results of scaling model are used to predict full-scale self-propulsion performance. However, the difference between the full-scale prediction and reality would be caused by scale effect. URANS simulations is conducted to predict self-propulsion of a full-scale KRISO Container Ship with the propeller KP505. Design speed is selected as simulation working condition according to Gothenburg 2010. In house CFD code HUST-Ship will be used to solve RANS equation coupled with two degrees of freedom (2DOF) solid body motion equations including heave and pitch. RANS equations are discretized by finite difference method and solved by PISO algorithm. The discretized propeller model and improved body-force model are used as the propulsion models. Grid and time step sensitivity analysis of full-scale propeller and hull is conducted separately. The self-propulsion indexes of full-scale simulation are compared with the extrapolation of model experimental data and full-scale simulation results from literatures. The prediction self-propulsion indexes based on different propulsion models are compared and discussed.

Thermodynamics of fractional-order nonlocal continua and its application to the thermoelastic response of beams

This study presents a comprehensive framework for constitutive modeling of a frame-invariant fractional-order approach to nonlocal thermoelasticity in solids. For this purpose, thermodynamic and mechanical balance laws are derived for nonlocal solids modeled using the fractional-order continuum theory. This includes revisiting the Cauchy’s hypothesis for surface traction vector in order to account for long-range interactions across the domain of nonlocal solid. Remarkably, it is shown that the fractional-order model allows the rigorous localized application of thermodynamic balance principles unlike existing integral approaches to nonlocal elasticity. Further, the mechanical governing equations of motion for the fractional-order solids obtained here are consistent with existing results from variational principles. These fractional-order governing equations involve self-adjoint operators and admit unique solutions, in contrast to analogous studies following the local Cauchy’s hypothesis. To illustrate the efficacy of this framework, case-studies for the linear and the geometrically nonlinear responses of nonlocal beams subject to combined thermomechanical loads are considered here. Comparisons with existing integer-order integral nonlocal approaches highlight a consistent softening response of nonlocal structures predicted by the fractional-order framework, irrespective of the boundary and thermomechanical loading conditions. This latter aspect addresses an important incongruence often observed following the strain-based integral approaches to nonlocal elasticity.

Laser Wakefield Driven Generation of Isolated Carrier-Envelope-Phase Tunable Intense Subcycle Pulses

Sources of intense, ultrashort electromagnetic pulses enable applications such as attosecond pulse generation, control of electron motion in solids, and the observation of reaction dynamics at the electronic level. For such applications, both high intensity and carrier-envelope-phase (CEP) tunability are beneficial, yet hard to obtain with current methods. In this Letter, we present a new scheme for generation of isolated CEP tunable intense subcycle pulses with central frequencies that range from the midinfrared to the ultraviolet. It utilizes an intense laser pulse that drives a wake in a plasma, copropagating with a long-wavelength seed pulse. The moving electron density spike of the wake amplifies the seed and forms a subcycle pulse. Controlling the CEP of the seed pulse or the delay between driver and seed leads to CEP tunability, while frequency tunability can be achieved by adjusting the laser and plasma parameters. Our 2D and 3D particle-in-cell simulations predict laser-to-subcycle-pulse conversion efficiencies up to 1%, resulting in relativistically intense subcycle pulses.

Reduced complexity solidification models

The solidification of a binary alloy, flowing between two cooled parallel plates is considered. A two-dimensional model for this system, involving the conservation equations of heat, solute, mass, and momentum, is constructed – the hi-fidelity model. Through a depth integration, a Reduced Complexity Model (RCM), in terms of one-dimensional advection equations, expressing the transient conservation of heat and solute, is obtained– the transient- RCM. For thermo-physical data, consistent with a dilute Al-Cu binary alloy, numerical predictions from the transient- RCM are shown to be in close agreement with predictions obtained from a numerical solution of the hi-fidelity model. The RCM is reduced further, to a model formed as a single initial value problem, predicting the steady-state axial temperature and liquid fraction profiles between the plates – the steady-RCM. Analysis and numerical solutions of the transient- RCM and steady-RCM, provide a means of modeling, evaluating, and illustrating the role of solid phase motion in the timing and pattern of a binary alloy solidification.

Numerical Simulation of Green Water on Deck with a Hybrid Eulerian-Lagrangian Method

Green water on the ship deck in rough sea conditions may induce extreme impulsive wave impacts on superstructures and result in severe structural damage. It is of great importance to consider green water loads in ship structure design. However, there are many challenges in predicting green water loads due to the strongly nonlinear wave–ship interactions and the multiphase, multi-scale nature of the wave impact phenomena. In this article, a three-dimensional hybrid Eulerian–Lagrangian approach is proposed for simulating green water loads on the ship deck. It is extended from an efficient and accurate two-dimensional method developed for fluid–structure interaction problems. In this method, the flow field is solved on a fixed regular Cartesian grid system in an Eulerian framework, whereas the solid body motion is tracked with a set of markers immersed in the fluid and solved in a Lagrangian framework. Two benchmark cases, green water on a fixed simplified Floating Production Storage and Offloading (FPSO) model and green water on ship, are simulated. Comparison between experimental data and numerical results shows that our method is a viable choice for predicting green water loads. Introduction In rough sea conditions, ships may undergo large-amplitude motions and suffer green water impacts due to the strongly nonlinear wave–body interaction. Large waves run up to the ship deck and impact on superstructures with huge volume of water impulsively. It can induce extreme impulsive wave impact loads on superstructures and result in severe structural damage. Thus, it is important to predict wave impact loads for ship structure design. However, there are still great challenges in predicting green water impact loads accurately because it is a flow phenomenon of high complexity and randomness due to its multiphase, highly turbulent nature with wave breaking, air entrainment, etc (Temarel et al. 2016).