Stopping Phases Research Articles

Study on the dynamic characteristics of planetary gear transmission mechanism of metal cold rolling mill

Using the parametric modelling feature in Solidworks software, a three-dimensional solid model of a planetary gearbox with linear reciprocating motion of the output shaft was constructed. By conducting theoretical calculations related to the kinematics of the transmission system and combining Adams virtual prototyping simulation technology, a dynamic simulation model of the planetary gear transmission mechanism was established to analyse the motion laws and dynamic characteristics. The simulation results were compared and analysed against the theoretical calculation results, and they showed good agreement and consistency. The study also investigated the impact of counterweights on the inertia forces and moments of the output shaft in the transmission mechanism. The results indicated that adding counterweights effectively reduced the inertia impact caused by inertia forces at the start and end positions of the stroke, as well as the inertia torque caused by changes in angular acceleration during the startup and stopping phases, thereby enhancing the smooth operation of the mechanism. Additionally, different thicknesses of counterweights had varying effects on balancing the inertia forces and moments of the output shaft. The study aimed to find the optimal thickness of counterweights to achieve the best balance effect. Furthermore, the study examined the influence of different speeds of the driving gear on the inertia forces of the output shaft. The results showed that at a driving gear speed of 1500 rpm, the horizontal thrust generated by the output shaft was 63566 N, which could provide the required thrust for the rolling mill operation, and the inertia forces of the output shaft tended to stabilize.

Numerical simulation of particle flow around the impulsive monopile

In order to explore the particle flow field characteristics around the impulsive monopile, the particle flow field and particle distribution around impulsive monopile were simulated based on the classical impulsive flow around a monopile at medium and low Reynolds number (Re = 550). The Large Eddy Simulation (LES) technique was harnessed to capture the dynamic flow field around the monopile and to facilitate in-depth analysis of vortex evolution. Concurrently, the Lagrangian approach was employed to track and characterize particle trajectories, shedding light on the patterns of particle diffusion and congregation in the vicinity of the monopile under varying Reynolds numbers. Additionally, this investigation unveils the distinctive behavior of particle flow during the impulsive starting and stopping phases adjacent to the monopile. Leveraging these insights, the study elucidates the intricate influence of the unsteady flow field dynamics around the monopile on the progression of particle flow.

The Destructive Earthquake Doublet of 6 February 2023 in South-Central Türkiye and Northwestern Syria: Initial Observations and Analyses

AbstractOn 6 February 2023, two large earthquakes with magnitude 7.8 and 7.6 rocked south-central Türkiye and northwestern Syria. At the time of writing, the death toll exceeded 50,000 in Türkiye and 7200 in Syria. The epicenter of the first mainshock was located ∼15 km east of the east Anatolian fault (EAF), the second large earthquake (9 hr later) initiated ∼90 km to the north on the east–west-trending Sürgü fault. Aftershocks delineate fault lengths of ∼350 and ∼170 km, respectively. Using satellite and seismic data for first-order analyses of surface-fault offsets, space–time rupture evolution, and recorded ground motions, our study sheds light on the reasons for the extensive destruction. The first event ruptured the EAF bilaterally, lasted for ∼80 s, and created surface fault offsets of over 6 m. The second event also ruptured bilaterally with a duration of ∼35 s and more than 7 m surface offsets. Horizontal ground accelerations reached locally up to 2g in the first mainshock; severe and widespread shaking occurred in the Hatay-Antakia area with values near 0.5g. Both earthquakes are characterized by directivity effects and abrupt rupture cessation generating stopping phases that contributed to strong seismic radiation. Shaking was further aggravated locally by site-amplification effects.

Simultaneous Rupture Propagation Through Fault Bifurcation of the 2021 Mw7.4 Maduo Earthquake

AbstractFault geometric complexity plays a critical role in earthquake rupture dimension. Fault bifurcations are commonly observed in earthquake geology, yet, robust kinematic rupture processes on bifurcated fault branches are largely missing, limiting our understanding of rupture dynamics and seismic hazard. Here, we holistically study the fault geometry and bilateral rupture of the 2021 Mw7.4 Maduo, China earthquake, that shows clear fault bifurcation near its eastern terminal. We integrate space geodesy imaging, back‐projection of high‐frequency teleseismic array waveforms, multiple point source and finite fault inversions, and constrain in detail the rupture process, in particular, through its fault bifurcation. Our models reveal a stable rupture speed of ∼2.5 km/s throughout the entire rupture and a simultaneous rupture through fault branches bifurcated at 20°. The rupture on bifurcated faults radiated more high‐frequency waves, especially from the stopping phases. The stopping phase on the southern branch likely stopped the rupture on the northern branch.

A variable refractory period increases collective performance in noisy environments

Synchronized oscillations are found in all living systems, from cellsto ecosystems and on varying time scales. A generic principlebehind the production of oscillations involves a delay in theresponse of one entity to stimulations from the others in the sys-tem. Communication among entities is required for the emergenceof synchronization, but its efficacy can be impaired by surroundingnoise. In the social spiderAnelosimus eximius, individuals coordi-nate their activity to catch large prey that are otherwise inaccessi-ble to solitary hunters. When hunting in groups, dozens of spidersmove rhythmically toward their prey by synchronizing movingand stopping phases. We proposed a mechanistic model imple-menting individual behavioral rules, all derived fromfield experi-ments, to elucidate the underlying principles of synchronization.We showed that the emergence of oscillations in spiders involvesa refractory state, the duration of which depends on the relativeintensity of prey versus conspecific signals. Thisflexible behaviorallows individuals to rapidly adapt to variations in their vibrationallandscapes. Exploring the model reveals that the benefits of syn-chronization resulting from improved accuracy in prey detectionand reduced latency to capture prey more than offset the cost ofthe delay associated with immobility phases. Overall, our studyshows that a refractory period whose duration is variable anddependent on information accessible to all entities in the systemcontributes to the emergence of self-organized oscillations innoisy environments. Ourfindings may inspire the design of artifi-cial systems requiring fast andflexible synchronization betweentheir components.

A bed pressure correction of the friction term for depth-averaged granular flow models

Depth-averaged models, such as the Savage-Hutter model with Coulomb or Pouliquen friction laws, do not in some cases preserve the physical threshold of motion. In particular, the simulated granular mass can start to flow (or stay at rest) even if the slope angle of its free surface is lower (or higher) than the repose angle of the granular material involved. The problem is related to the hydrostatic pressure assumption, associated with the direction of integration, which is orthogonal to a reference plane or a reference bottom. We propose here an initial method to correct this misleading behavior. Firstly, we define a correction of the friction term that accounts for the Jacobian of a change of coordinates, making it possible to reproduce the physical threshold of motion and thus the solutions at rest. Secondly, we observe that the 3D model presented in [F. Bouchut, I. Ionescu, and A. Mangeney. An analytic approach for the evolution of the static-flowing interface in viscoplastic granular flows. Commun, Math. Sci., 14(8):2101–2126, 2016] verifies the physical thresholds of motion because it is based on a second order correction of the pressure valid for slow granular flows. The correction proposed here ensures that the model preserves, up to the second order, the physical threshold of motion defined by the repose angle of the material. Several numerical tests are presented to illustrate certain problems related to classical depth averaged models and the remedial effect of the proposed correction, in particular through comparisons with experimental data. We finally show that this correction is not exact far from the starting and stopping phases of the granular avalanche and should be improved by adding other second order terms in the pressure approximation.

Wheel Load Torque Emulation for Electric Propulsion Structure using Dual Induction Motors

Electric vehicle is an adaptation of conventional vehicle, with an integration of electrical motors. It seems to be one of the most promising technologies that can lead to significant improvements in vehicle performance and polluting emissions. However, for any vehicle in urban traffic requires regime changes, frequent acceleration, deceleration, and stopping phases, which lead to serious breakdowns. During the above phases, electric motors are continuously being exposed to thermal and mechanical effects.This paper highlights the possibility of representing the wheel load torque emulation of an electric propulsion structure using dual induction motors vector-controlled. The emulation of load torque acting on one of both electric motors placed at the rear wheels of electric vehicle (EV) structure is accomplished by a DC-generator coupled with an induction motor during vehicle drive cycle operation andunpredictable load profiles. Simulation results confirm widely the feasibility and the effectiveness of the proposed emulator scheme of induction motor-based vector-control in the electric vehicle application.

Learning walks in an Australian desert ant, Melophorus bagoti.

ABSTRACTThe central Australian ant Melophorus bagoti is the most thermophilic ant in Australia and forages solitarily in the summer months during the hottest period of the day. For successful navigation, desert ants of many species are known to integrate a path and learn landmark cues around the nest. Ants perform a series of exploratory walks around the nest before their first foraging trip, during which they are presumed to learn about their landmark panorama. Here, we studied 15 naive M. bagoti ants transitioning from indoor work to foraging outside the nest. In 3–4 consecutive days, they performed 3–7 exploratory walks before heading off to forage. Naive ants increased the area of exploration around the nest and the duration of trips over successive learning walks. In their first foraging walk, the majority of the ants followed a direction explored on their last learning walk. During learning walks, the ants stopped and performed stereotypical orientation behaviours called pirouettes. They performed complete body rotations with stopping phases as well as small circular walks without stops known as voltes. After just one learning walk, these desert ants could head in the home direction from locations 2 m from the nest, although not from locations 4 m from the nest. These results suggest gradual learning of the visual landmark panorama around the foragers’ nest. Our observations show that M. bagoti exhibit similar characteristics in their learning walks to other desert ants of the genera Ocymyrmex and Cataglyphis.

Gas face seal status estimation based on acoustic emission monitoring and support vector machine regression

The difficulty of knowing the real-time status of gas face seals is the main cause of common problems, including sudden failure, ineffective diagnosis, and unpredictability of service life. This study analyzed the acoustic emission signals generated from experiments, uncovering their features in terms of the frequency distribution, periodic fluctuations, and the behaviors during different operation phases. A new vectorization procedure was designed according to the knowledge of informative acoustic emission features. Based on the vectorization procedure, a support vector machine regression method was applied to develop models predicting the eccentric load on the stator of the seal. Cross-validation was conducted to evaluate the regression performance and search for a proper kernel scale. This study found the informative features of acoustic emissions at different timescales and during different seal operation phases, and particularly the great informative potential of certain segments of the starting and stopping phases. The vectorization and support vector machine regression were shown to be effective in estimating the loads in experiments with cross-validation. Thus, a method for estimating the status of gas face seals based on acoustic emission monitoring was established.

Investigation of transient response motion of differential planetary gear train during reverse rotation and starting by using high-speed camera monitoring

Planetary gear trains (PGTs) have been used in various applications, including hybrid and electric vehicles, owing to their advantages such as compactness, light weight, and large torque-to-weight ratio; however, recently, their transient response, such as sudden stop in differential usage when applied to cooperative robots (CRs), has emerged as a critical issue. It is difficult to elucidate the motion mechanism of PGTs, due to differing meshing conditions among internal and external meshing, the large number of meshing points, and simultaneous rotation and revolution. Therefore, few experimental investigations concerning PGT transient responses have been performed worldwide. This study aims to elucidate the transient response, in particular in the case of reverse rotation, considering the critical issues pertaining to the use of PGTs in CRs. Transient response has three continuous phases: braking, stopping, and starting. A novel gear train, named 2K-HV PGT, having a clear acrylic carrier, was developed to enable direct observation of the planet gear motion, because it is otherwise impossible to observe the inner mechanisms of the conventional 2K-H PGT. Direct observations of the novel PGT were recorded using a high-speed camera. The observations of the transient responses showed differences in the switching times or stopping phases, due to differences in the moments of inertia and torsional rigidities among the PGT components. The transient response of reverse rotation did not occur instantaneously, but rather gradually within a certain time band.

Sensitivity of High-Frequency Ground Motion to Kinematic Source Parameters

Empirical ground motion prediction equations are calibrated from past earthquake seismic recordings. Although they are often used to predict Peak Ground Acceleration (PGA) and its variability, the use of these equations to predict near-fault PGA remains questionable due to the scarcity of near-fault recordings for large earthquakes (e.g. Mai Encyclopedia of complexity and systems science (pp. 4435–4474). New York: Springer. https://doi.org/10.1007/978-0-387-30440-3_263. 2009). The simulation of strong ground motion offers an attractive alternative for the assessment of near-fault seismic hazards, but the a priori choice of the source parameters used to describe the fault rupture process remains a complex issue. In order to better understand the effects of rupture parameters on surface ground motion and to capture the key source ingredients that impact ground motion variability, we simulated ground motions produced by various M7 strike-slip rupture earthquake scenarios on vertical faults. We computed ground motion up to 5 Hz using the far-field approximation as well as at the near-field stations located at 5 km, 25 km and 70 km from the fault (assuming a visco-elastic medium). The kinematic rupture parameters are modeled using a statistical rupture model generator as proposed by Song et al. Geophysical Journal International,196(3), 1770–1786 (2014). Our work demonstrates that PGA is mostly generated by abrupt changes in the rupture propagation (e.g. stopping phases at the fault boundaries or strong heterogeneities of rupture speed along the fault). We observed that PGA is mostly controlled by average rupture speed and average stress drop (in the far-field), and to a lesser extent by the standard deviation of the rupture speed. It is worth noting that for the set of stations in study, the correlation between source parameters and spatial correlation length does not affect average PGA and related variability significantly.

IMEX_SfloW2D 1.0: a depth-averaged numerical flow model for pyroclastic avalanches

Abstract. Pyroclastic avalanches are a type of granular flow generated at active volcanoes by different mechanisms, including the collapse of steep pyroclastic deposits (e.g., scoria and ash cones), fountaining during moderately explosive eruptions, and crumbling and gravitational collapse of lava domes. They represent end-members of gravity-driven pyroclastic flows characterized by relatively small volumes (less than about 1 Mm3) and relatively thin (1–10 m) layers at high particle concentration (10–50 vol %), manifesting strong topographic control. The simulation of their dynamics and mapping of their hazards pose several different problems to researchers and practitioners, mostly due to the complex and still poorly understood rheology of the polydisperse granular mixture and to the interaction with the complex natural three-dimensional topography, which often causes rapid rheological changes. In this paper, we present IMEX_SfloW2D, a depth-averaged flow model describing the granular mixture as a single-phase granular fluid. The model is formulated in absolute Cartesian coordinates (whereby the fluid flow equations are integrated along the direction of gravity) and can be solved over a topography described by a digital elevation model. The numerical discretization and solution algorithms are formulated to allow for a robust description of wet–dry conditions (thus allowing us to accurately track the front propagation) and an implicit solution to the nonlinear friction terms. Owing to these features, the model is able to reproduce steady solutions, such as the triggering and stopping phases of the flow, without the need for empirical conditions. Benchmark cases are discussed to verify the numerical code implementation and to demonstrate the main features of the new model. A preliminary application to the simulation of the 11 February pyroclastic avalanche at the Etna volcano (Italy) is finally presented. In the present formulation, a simple semi-empirical friction model (Voellmy–Salm rheology) is implemented. However, the modular structure of the code facilitates the implementation of more specific and calibrated rheological models for pyroclastic avalanches.

The Geomagnetic Field Is a Compass Cue in Cataglyphis Ant Navigation

Desert ants (Cataglyphis) are famous insect navigators. During their foraging lives, the ants leave their underground colonies for long distances and return to their starting point with fair accuracy [1, 2]. Their incessantly running path integrator provides them with a continually updated home vector [3-5]. Directional input to their path integrator is provided by avisual compass based on celestial cues [6, 7]. However, as path integration is prone to cumulative errors, the ants additionally employ landmark guidance routines [8-11]. At the start of their foraging lives, they acquire the necessary landmark information by performing well-structured learning walks [12, 13], including turns about their vertical body axes [14]. When Cataglyphis noda performs these pirouettes, it always gazes at the nest entrance during the longest of several short stopping phases [14]. As the small nest entrance is not visible, the ants can adjust their gaze direction only by reading out their path integrator. However, recent experiments have shown that, for adjusting the goal-centered gaze directions during learning walks, skylight cues are not required [15]. A most promising remaining compass cue is the geomagnetic field, which is used for orientation in one way or the other by a variety of animal species [16-25]. Here, we show that the gaze directions during the look-back-to-the-nest behavior change in a predictable way to alterations of the horizontal component of the magnetic field. This is the first demonstration that, in insects, a geomagnetic compass cue is both necessary and sufficient for accomplishing a well-defined navigational task.

Effect of Seismogenic Depth and Background Stress on Physical Limits of Earthquake Rupture Across Fault Step Overs

AbstractEarthquakes can rupture geometrically complex fault systems by breaching fault step overs. Quantifying the likelihood of rupture jump across step overs is important to evaluate earthquake hazard and to understand the interactions between dynamic rupture and fault growth processes. Here we investigate the role of seismogenic depth and background stress on physical limits of earthquake rupture across fault step overs. Our computational and theoretical study is focused on the canonical case of two parallel strike‐slip faults with large aspect ratio, uniform prestress and friction properties. We conduct a systematic set of 3‐D dynamic rupture simulations with different seismogenic depth, step over distance, and initial stresses. We find that the maximum step over distance Hc that a rupture can jump depends on seismogenic depth W and strength excess to stress drop ratio S, commonly used to evaluate probable rupture velocity, as , where n = 2 when Hc/W < 0.2 (or S > 1.5) and n = 1 otherwise. The critical nucleation size, largely controlled by frictional properties, has a second‐order effect on Hc. Rupture on the secondary fault is mainly triggered by the stopping phase emanated from the rupture end on the primary fault. Asymptotic analysis of the peak amplitude of stopping phases sheds light on the mechanical origin of the relations between Hc, W, and S, and leads to the scaling regime with n = 1 in far field and n = 2 in near field. The results suggest that strike‐slip earthquakes on faults with large seismogenic depth or operating at high shear stresses can jump wider step overs than observed so far in continental interplate earthquakes.

Species-specific differences in the fine structure of learning walk elements in Cataglyphis ants.

Cataglyphis desert ants are famous navigators. Like all central place foragers, they are confronted with the challenge to return home, i.e. relocate an inconspicuous nest entrance in the ground, after their extensive foraging trips. When leaving the underground nest for the first time, desert ants perform a striking behavior, so-called learning walks that are well structured. However, it is still unclear how the ants initially acquire the information needed for sky- and landmark-based navigation, in particular how they calibrate their compass system at the beginning of their foraging careers. Using high-speed video analyses, we show that different Cataglyphis species include different types of characteristic turns in their learning walks. Pirouettes are full or partial rotations (tight turns about the vertical body axis) during which the ants frequently stop and gaze back in the direction of the nest entrance during the longest stopping phases. In contrast, voltes are small walked circles without directed stopping phases. Interestingly, only Cataglyphis ant species living in a cluttered, and therefore visually rich, environment (i.e. C. noda and C. aenescens in southern Greece) perform both voltes and pirouettes. They look back to the nest entrance during pirouettes, most probably to take snapshots of the surroundings. In contrast, C. fortis inhabiting featureless saltpans in Tunisia perform only voltes and do not stop during these turns to gaze back at the nest - even if a set of artificial landmarks surrounds the nest entrance.

Influence of both friction and wear on the vibration of marine water lubricated rubber bearing

Marine water-lubricated bearing is the key part of the thrust shafting of underwater vehicles and some surface vessels, that is currently made with rubber, Thordon, Feroform, nylon, lignumvitae materials etc. Because the performance of vibration and noise reduction of the rubber material is better than some materials so that it is usually applied in water-lubricated propeller shaft bearing of submarines and underwater vehicles to improve their stealth, security, performance and reliability. Although the rubber is of better damping effect, it is always easy to cause friction vibration and noise under low speed, heavy load and wear situation, especially at starting or stopping phases. Therefore, it is of important theoretical significance and engineering value to enhance the mute level of the vehicles and alleviate friction vibration and noise.The tribological properties of water-lubricated rubber bearing such as friction and wear can affect the bearing vibration directly. So the research objective is to explore the influence of both friction and wear of water-lubricated rubber bearing on the bearing vibration under the different rubber materials of the bearing lining and working conditions. In the research, both theoretical analysis and test methods are applied. In theoretical analysis, the finite element model of the bearing is established and the deformation of the bearing lining is analyzed, and in test research, kinds of water-lubricated bearings with different rubber material were tested on the bearing test-bed under different shaft rotary speed, load and cooling water temperature. The research results show that both friction coefficient and wear of water-lubricated rubber bearings are affected with the different rotary speed, load and cooling water temperature, which result in the bearing vibration status changed significantly. With the increase of the load in some range, the deformation of the bearing lining is intensified and the specific pressure of the bearing is decreased due to the augment of contact area of between test shaft and bearing lining so that the friction coefficient and vibration are declined. As cooling water temperature is enhanced, both wear and vibration are aggravated.The higher shaft rotary speed is, smaller friction coefficient is in certain speed range so friction vibration is reduced.

Semi-automated salt-assisted liquid–liquid extraction coupled to high-performance liquid chromatography to determine three aromatic hydrocarbons in aqueous samples

In this study, a new device for semi-automated salt-assisted liquid–liquid extraction was designed and coupled with high-performance liquid chromatography (HPLC) to determine three aromatic hydrocarbons in aqueous samples. In order to evaluate the performance of the designed device, three aromatic hydrocarbons including 2-naphthol, naphthalene and anthracene were selected as model analytes. Sample solution, extraction solvent and salt solution using separate channels were transferred to a sample holder, respectively. These three components were mixed using a magnetic stirrer. After stirrer stopping, the aqueous and organic phases were separated and organic layer transferred to the injection loop of HPLC system. Optimization process was achieved using response surface methodology by Design-Expert software. A central composite design was used to optimize the main parameters including pH (A), stirrer time (B), organic solvent volume (C) and salt concentration (D). The limit of quantitation for 2-naphthol, naphthalene and anthracene was 15.0, 25.0 and 1.0 ng mL−1, respectively. Under the optimum conditions, obtained recoveries for three analytes were in the range of 76.0–96.2% with relative standard deviation less than 8.2%. The salt-assisted liquid–liquid extraction method using the proposed device has been successfully used for the analysis of real samples containing studied analytes in various matrices.

New perspectives on self‐similarity for shallow thrust earthquakes

AbstractScaling of dynamic rupture processes from small to large earthquakes is critical to seismic hazard assessment. Large subduction earthquakes are typically remote, and we mostly rely on teleseismic body waves to extract information on their slip rate functions. We estimate the P wave source spectra of 942 thrust earthquakes of magnitude Mw 5.5 and above by carefully removing wave propagation effects (geometrical spreading, attenuation, and free surface effects). The conventional spectral model of a single‐corner frequency and high‐frequency falloff rate does not explain our data, and we instead introduce a double‐corner‐frequency model, modified from the Haskell propagating source model, with an intermediate falloff of f−1. The first corner frequency f1 relates closely to the source duration T1, its scaling follows for Mw<7.5, and changes to for larger earthquakes. An elliptical rupture geometry better explains the observed scaling than circular crack models. The second time scale T2 varies more weakly with moment, , varies weakly with depth, and can be interpreted either as expressions of starting and stopping phases, as a pulse‐like rupture, or a dynamic weakening process. Estimated stress drops and scaled energy (ratio of radiated energy over seismic moment) are both invariant with seismic moment. However, the observed earthquakes are not self‐similar because their source geometry and spectral shapes vary with earthquake size. We find and map global variations of these source parameters.

Earthquake dynamics on circular faults: a review 1970–2015

We review the development of earthquake dynamics taken from the point of view of the origin of seismic radiation instead of the detailed study of rupture propagation on complex surfaces. Many features of seismic radiation can be explained by simple models that serve as elementary canonical problems. Some of these properties are very well known like the fact that at low frequencies, the seismic spectrum is proportional to the seismic moment. At high frequencies, on the other hand, radiation is generated by the motion of the rupture front, in particular stopping phases and geometrical obstacles (barriers). A rupture front moving at constant speed does not produce far-field radiation. For many practical applications, for determining source size and stress drop, for example, it is not necessary to determine geometrical details of the rupture. For such cases, a simple circular crack model is quite sufficient. An improvement on this method is to do dynamic inversion on simple, elliptical-shaped sources and letting the rupture start arbitrarily from a point on the fault. This problem can be solved nowadays with finite differences and a variety of inversion techniques.

Towards a quantitative understanding of pyroclastic flows: Effects of expansion on the dynamics of laboratory fluidized granular flows

We conducted laboratory dam-break experiments on initially fluidized granular flows using two different fine-grained powders (mean grain sizes 47 and 67μm) down a smooth, horizontal channel with an impermeable base. The powders were first fluidized and expanded to a known degree in the flume reservoir, then released down the channel by opening a sliding gate. The mixture formed rapidly moving flows that defluidized and deposited progressively as they propagated. The experiments were similar to those carried out previously using volcanic ash by Girolami et al. (2008, 2010) but explored a much larger range of initial aspect ratios (height-to-length ratio, a=0.25 to 4). They were designed to investigate the effects of initial expansion (up to 50vol.% above loose packing) and aspect ratio on the dynamics of flow propagation and deposition, and to explore different scalings in order to determine the physical parameters governing these processes. The flows exhibit a similar behaviour to other types of transient granular flows, including three well defined propagation phases (acceleration, constant velocity, and stopping phases) and the progressive aggradation of a basal static layer during emplacement. The deposit aggradation velocity depends only on the initial powder expansion and is similar to that of a collapsing bed of the same powder, expanded by the same amount, under quasi-static, non-shearing conditions. At a given initial expansion, the maximum runout distance scales with the initial bed height h0, the runout duration with (h0/g)1/2 and the maximum velocity with (gh0)1/2. However, runout distance and duration both increase with increasing initial expansion. This is attributed to the effect of hindered settling in delaying defluidization of the dense, but slightly expanded, suspension. The data enable us to identify an additive scaling law providing a smooth transition from non-expanded to expanded flows.