Large-scale Laboratory Research Articles

Numerical investigation of monochromatic wave interaction with a vertical seawall located on a reef flat

Existing design codes for coastal defense structures built on coral reefs are scarce compared to those for traditional sandy or muddy beaches. A three-dimensional numerical wave flume is developed to investigate monochromatic wave interaction with a vertical seawall located on the reef flat. The Navier-Stokes equations for two-phase incompressible flow, combining with methods of Large Eddy Simulation (LES) for turbulence closure and Volume of Fluid (VOF) for tracking the free surface, are solved. A set of large-scale laboratory experiments are performed to validate the adopted model in terms of free surface, velocity, dynamic pressure as well as overtopping discharge around the seawall. The model is first applied to examine the cross-shore evolution of waves and flows associated with breaking wave interaction with the seawall. Subsequently, a series of numerical simulations are implemented to study the impacts of different hydrodynamic (incident wave height, incident wave period, and reef-flat wave level) as well as reef and seawall morphological factors (fore-reef slope, seawall position and seawall crest width) on the overtopping discharge over the seawall as well as the cross-shore wave impact force acting on the seawall. Finally, new empirical formulas are proposed, respectively, to predict the overtopping discharge and the wave force.

Does geographical origin affect lateralization and male mating success in Rhyzopertha dominica beetles?

The lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), is an important pest of stored grains globally. In this study, the impact of geographical origin on male mating success and lateralization in three strains of R. dominica (i.e., a Greek strain, a Romanian strain and a Turkish strain) was investigated. Concerning the Greek strain, even though most males showed a left-biased approach, males performing right-biased copulation attempts achieved the highest proportion of successful copulations. Males of the Romanian and Turkish strains exhibited right-biased approaches and copulation attempts, resulting in higher mating success over the males that approached and performed copulation attempts from the left or backside of females. Copula was significantly longer than mate recognition and precopula phases. Furthermore, copula duration was significantly longer in the Turkish strain over the Romanian strain, while copula duration differences between Greek and Romanian individuals, as well as between Greek and Turkish individuals, were not significant. Unsuccessful sexual interactions were characterized by a longer precopula in Greek and Romanian strains, but not in the Turkish strain. Our results add basic knowledge to the mating behaviour of R. dominica, with emphasis on impact of the geographical origin and laterality on male mating success, which may be helpful for optimizing mass-rearing techniques of stored-product pests needed for large-scale laboratory or semi-field experiments, as well as to contribute to the development of behaviour-based control tools.

Nucleation of Stick-Slip Instability Within a Large-Scale Experimental Fault: Effects of Stress Heterogeneities Due to Loading and Gouge Layer Compaction.

Geodetic observations and large‐scale laboratory experiments show that seismic instability is preceded by slow slip within a finite nucleation zone. In laboratory experiments rupture nucleation is studied mostly using bare (rock) interfaces, whereas upper crustal faults are typically filled with gouge. To investigate effects of gouge on rupture nucleation, we performed a biaxial shearing experiment on a 350 mm long saw‐cut fault filled with gypsum gouge, at room temperature and a minimum horizontal stress σ 2 = 0.3–5 MPa. The gouge layer was sandwiched between polymethylmethacrylate (PMMA) plates For reference also a fault without gouge was deformed. Strain gauges and Digital Image Correlation were used to monitor the deformation field along the fault zone margins. Stick‐slip behavior occurred on both the gouge‐filled fault and the PMMA fault. Nucleation of instability on the PMMA fault persistently occurred from one location 2/3 to 3/4 along the fault adjacent to a slow slip zone at the fault end, but nucleation on the gouge‐filled fault was more variable, nucleating at the ends and/or at approximately 2/3 along the fault, with precursory slip occurring over a large fraction of the fault. Nucleation correlated to regions of high average fault stress ratio τ/σ n, which was more variable for the gouge‐filled fault due to small length scale variations in normal stress caused by heterogeneous gouge compaction. Rupture velocities and slip rates were lower for the gouge‐filled fault than for the bare PMMA fault. Stick‐slip persisted when σ 2 was lowered and the nucleation zone length increased, expanding from the center to the sample ends before transitioning into instability.

Large-scale laboratory study on the evolution law of temperature fields in the context of underground coal gasification

This article presents the evolution law of temperature fields in a large-scale laboratory Underground Coal Gasification reactions using Ulanqab lignite under actual conditions. The results show that in the cultivation stage of oxidation zone, the main direction of the temperature field expansion is consistent with the crack direction of the coal seam. In the gasification stabilization stage, the main direction of the temperature field expansion is along the channel. The temperature of the coal seam and the overlying rock mass at its interface with the furnace directly above the gasification channel is equivalent to that of the coal seam temperature, and this temperature is much greater than the temperatures observed near both side walls of the gasification channel at the interface. However, temperatures perpendicular to the axis of the gasification channel are similar at a vertical distance of 40 cm away from the interface. The temperature distributions indicate that the transmission of heat through the overlying rock mass is more rapid in the vertical direction than in the horizontal direction. Moreover, some degree of thermal dispersion is observed in the vertical direction near the outlet. The thermal dispersion coefficient is 0.72 and dispersion angle γ is 78.7°.

Slags from Ruda Śląska, Poland as a large-scale laboratory for the crystallization of rare natural rocks: melilitolites and paralavas

Zinc and lead smelting slags from Ruda Śląska are unique in their chemistry and phase composition, which resemble rare natural rocks such as paralavas and melilitolites. Moreover, considering its size, we can treat a pyrometallurgical slag dump as a geological body. In slags from Ruda Śląska the assemblage melilite ± pseudowollastonite ± wollastonite ± plagioclase was discovered in glassy slag. High-temperature experiments were performed to determine the temperature conditions and to reconstruct the crystallization of such an assemblage. Two slag samples were subjected to complete melting and crystallization with controlled thermal gradients of: 53.25 °C/h, 15.20 °C/h and 7.60 °C/h. The results showed that crystal nucleation started at temperatures of 1250-1300 °C depending on the fluctuations of chemical composition. In both samples the thermal gradient only partly influenced the phase differentiation, being rather responsible for the disappearance of the primary glass. Moreover, even slight differences in chemical composition resulted in changes in phase assemblages under the same temperature conditions (mll + gls vs pwol+pl + mll + gls). It was proven that it is due to the combination of undercooling conditions and solidus dependences in the åkermanite – gehlenite solid solution. The occurrence of such phenomena should be considered in natural rocks with similar composition. In the case of the Ruda Śląska slags it explains the dominance of glassy slag in that location. The experiments gave us an opportunity to observe and precisely analyze crystallization in real time, providing new insights into the creation of slags and their natural analogues. However, the study has also shown that possible variations of the original crystallization should always be assessed.

A New Semi-Analytical Method to Calculate the Fluvial Erosion Rate of Non-Cohesive Riverbanks

Fluvial erosion due to hydraulic force and bank failure under the influence of gravity are the two physical processes of riverbank erosion. This paper presents a new, simple, semi-analytical method to estimate the rate of fluvial erosion of non-cohesive riverbanks caused by hydraulic force. The derived equation is built based on the critical flow velocity concept, rather than the commonly used shear stress approaches. Because the distribution of the shear stress of a side wall varies considerably with the side wall’s cross-sectional profile, it is difficult to estimate the shear stress distribution along a river bank. In contrast, the cross-sectional contours of flow velocity close to the side wall are parallel to the wall to some extent, which suggests that the flow velocity is more reliable and more easily measured in comparison to the shear stress. Large-scale laboratory experiments were conducted to evaluate the critical-velocity-based model. The calculated results agree well with the measured data. This semi-analytical approach is promising for estimating the fluvial bank erosion rate in the field.

Cloud–Aerosol–Turbulence Interactions: Science Priorities and Concepts for a Large-Scale Laboratory Facility

The National Science Foundation (NSF) provided the funding support for this workshop through grant number AGS-1945681. We are grateful to the following: Susannah Burrows (Pacific Northwest National Laboratory), Hermann Gerber (Gerber Scientific), and Fan Yang (Brookhaven National Laboratory) for looking over the meeting summary for accuracy; Jessica Brassard of Michigan Technological University for invaluable support and advising on the strategy, organization, and logistics of the workshop, as well as for the artistic musings shown in Figure 1; Peter Sullivan and Wojciech Grabowski for facilitating the coordination and co-sponsorship by the Geophysical Turbulence Program; Kris Marwitz of NCAR for administrative and logistical support; And to the more than 60 attendees who actively engaged in brainstorms and discussions, without whom this meeting summary would not have been possible

Numerical modelling of tsunamis generated by iceberg calving validated with large-scale laboratory experiments

When calving icebergs interact with water, waves of tens of meters in height, so-called iceberg-tsunamis (IBTs), may be generated. Recent examples include an IBT which reached an amplitude of 45 to 50 m in Eqip Sermia, Greenland, in 2014. A novel numerical methodology and unique large-scale laboratory experiments are presented to investigate the generation and propagation of such IBTs. In the laboratory the IBTs were generated with rigid blocks in a 50 m × 50 m basin. For the numerical model a multiphase flow solver is extended by coupling it with a motion solver to handle dynamic immersed boundaries such as the surfaces of floating icebergs. An analytical solution of the radiated waves by a heaving sphere in still water, a vertically falling and an overturning block experiment are used to validate the numerical model. The model simulates the laboratory IBTs with a maximum relative error of 15.5% in the first (leading) wave amplitude and 13.8% in the wave height decay exponent if the splash is ignored. The validated model is then used successfully to replicate the 2014 Eqip Sermia IBT. This new numerical model is expected to be useful for IBT hazard assessment and many further floating body phenomena.

Ground Penetrating Radar for Water Content and Compaction Evaluation: A Laboratory Test on Construction Material

With the aid of ground penetrating radar (GPR), it is possible to evaluate physical properties of a constructed base layer in engineered structures (pavement, land consolidation projects, etc.) non-destructively, quickly, and accurately. High spatial variations of subsurface water content and deficient compaction can lead to unexpected damage and structural instability. In this research, we established a relationship between the dielectric constant, water content, and compaction, whereby, an interactive relationship between these parameters is presented. To achieve this, large-scale laboratory experiments were carried out on construction materials to simulate field conditions. According to USCS, the tested soil type was GW-GM (type E base layer according to Iran's highway specifications code). Furthermore, water content and compaction were changed between 4% -12.9% and 84.7% -94.9%, respectively. The travel-times in each test, including three profiles with more than 210 traces, are measured automatically. Additionally, the calculated dielectric constants were compared with the Topp and Roth equations. R-square and RMS error of the final interactive equation between dielectric constant and water content-compaction were 0.95 and 0.41, respectively. Moreover, the sensitivity analysis of the proposed interactive equation shows that changes in water content of soil have greater impact on dielectric constant than soil compaction changes. The data also indicate the importance of considering the compaction changes of soil to reduce the error in dielectric constant estimation.

Widening Access to Bayesian Problem Solving.

Bayesian reasoning and decision making is widely considered normative because it minimizes prediction error in a coherent way. However, it is often difficult to apply Bayesian principles to complex real world problems, which typically have many unknowns and interconnected variables. Bayesian network modeling techniques make it possible to model such problems and obtain precise predictions about the causal impact that changing the value of one variable may have on the values of other variables connected to it. But Bayesian modeling is itself complex, and has until now remained largely inaccessible to lay people. In a large scale lab experiment, we provide proof of principle that a Bayesian network modeling tool, adapted to provide basic training and guidance on the modeling process to beginners without requiring knowledge of the mathematical machinery working behind the scenes, significantly helps lay people find normative Bayesian solutions to complex problems, compared to generic training on probabilistic reasoning. We discuss the implications of this finding for the use of Bayesian network software tools in applied contexts such as security, medical, forensic, economic or environmental decision making.

Влияние операционных аспектов процесса восстановления оксида кремния на соотношение материального и теплового потоков в рудно-термической печи

A study was carried out into the effect of the loading method and surface distribution of charges at the furnace top on the parameters of carbon reduction of silica in submerged arc furnaces. In the study, the direct physical modelling method was applied. The experiments were carried out under large-scale laboratory conditions using a 200 kVA single-electrode furnace of the Zh. Abishev Chemical and Metallurgical Institute (Kazakhstan). An additional dynamic industrial experiment was conducted in the 30 MVA furnace of Tau-Ken Temir LLP. In a large laboratory furnace, two smelting campaigns were performed, each using different approaches to the treatment of the furnace top. In the first campaign, no balancing in the energy and material flows of the system took place, resulting in forced slipping and an uncontrolled feed rate of the charge. The second campaign, conversely, included the specified balancing measures. A similar study took place over 3 days under industrial conditions. The following technological parameters were empirically determined: specific electricity consumption, furnace average active power and performance, as well as power per unit area of the furnace hearth. The Fe, Al, Ca, Si material balance of the smelting was compiled. In order to assess the load balance, the concept of charge excess in relation to charge demand at the current furnace power was used for the first time. This concept value was determined as the ratio of number of batches actually loaded relative to the theoretically-calculated number ensuring the harmonisation of material and energy flows in the furnace. As a result of the research, an increase in the interval between the furnace top treatments up to 30 min and maintenance of harmonisation between material and thermal flows in the ore smelting furnace was established for increasing silicon extraction efficiency by 10-15%. In addition, oscillations in the phase current were stabilised. The proposed balancing concept was established to support the rapid elimination of crisis conditions in an industrial furnace.

Structural health monitoring and seismic response assessment of bridge structures using target-tracking digital image correlation

Our nation’s infrastructure is aging and deteriorating which increases the need for condition assessment and structural health monitoring. For this purpose, there is a growing interest in using non-contact monitoring methods because of the challenges associated with deploying and installing conventional instrumentation. Target-tracking digital image correlation (DIC) is among these methods and is the focus of this paper. Several research activities have been conducted at the University of Nevada, Reno in the field of dynamic monitoring using DIC and presented here. The first part of the paper is concerned with a large-scale laboratory application where target-tracking DIC was utilized to monitor the response of a bridge structure tested under bidirectional earthquake shaking. The 3D dynamic response of the bridge, along with modal properties, i.e. natural frequency, damping ratio, and mode shapes, were measured or determined using both DIC and conventional instrumentation then compared for validation purposes. The second part of the paper presents results from field monitoring of an actual footbridge under pedestrian loading to determine the vibration frequencies of the bridge, and again compare it against results from conventional accelerometers for validation. From both applications, the DIC is demonstrated to successfully capture (1) peak and residual bridge deck rotation and deformation under different earthquake intensity levels and (2) modal properties for system identification. Practical DIC sampling rates were used to accurately monitor and capture the dynamic response of bridges, which shows a high potential for using DIC for larger structural health monitoring applications and future reconnaissance works.

Laboratory Characterization of The Load Transfer-Crack Width Relation for Innovative Short Concrete Slabs Pavements

Aggregate interlock is the dominant load transfer mechanism in non-dowelled Jointed Plain Concrete Pavements, as the innovative short concrete slabs. Although the Load Transfer Efficiency of this pavement innovation is based on that mechanism, the structural design methods do not relate the Load Transfer Efficiency by aggregate interlock with its direct cause, which is the Crack Width under the joints. The objective of the present article is to characterise in the laboratory the Load Transfer Efficiency−Crack Width relation for innovative short slabs Jointed Plain Concrete Pavements. Additionally, as an alternative to large-scale laboratory tests to study the Load Transfer Efficiency, a practical test on a reduced scale is proposed. The results confirmed that short slabs Jointed Plain Concrete Pavements with high-quality aggregates are able to provide adequate Load Transfer Efficiency (above 70%) without dowels bars. Based on the laboratory results, complemented with previous field data, a Load Transfer Efficiency−Crack Width curve is proposed and made available for structural design methods of short slabs Jointed Plain Concrete Pavements. Finally, the laboratory test on a reduced scale is useful to develop specific Load Transfer Efficiency−Crack Width relations using standard equipment available in traditional concrete laboratories.

Holographic astigmatic particle tracking velocimetry (HAPTV)

The formation of twin images in digital inline holography (DIH) prevents the placement of the focal plane in the center of a sample volume for DIH-based particle tracking velocimetry (DIH-PTV) with a single camera. As a result, it is challenging to apply DIH-PTV for flow measurements in large-scale laboratory facilities or many field applications where it would otherwise be desirable due to the low cost and compact setup. Here we introduce holographic astigmatic PTV (HAPTV) by inserting a cylindrical lens in the optical setup of DIH-PTV, generating distorted holograms. Such distortion is subsequently utilized in a customized reconstruction algorithm to distinguish tracers positioned on different sides of the focal plane which can in turn be placed in the middle of a sample volume. Our HAPTV approach is calibrated under high (1 µm pixel−1) and low (10 µm pixel−1) magnifications with an error standard deviation of 4.2 µm (one particle diameter) and 120.7 µm (~5 times the particle diameter), respectively. We compare the velocity field of a laminar jet flow obtained using HAPTV and conventional PIV to illustrate the accuracy of the technique when applied to practical flow measurement applications. The work demonstrates that HAPTV improves upon the depth of field of conventional astigmatic PTV and enables the implementation of DIH-based PTV for in situ applications.

Particle history from massively parallel large eddy simulations of pulverised coal combustion in a large-scale laboratory furnace

A study on the coal particle history during combustion in a large-scale furnace using large eddy simulation is presented. The massively parallel execution produces a high-resolution representation of the fluid mixing and particle dispersion throughout the whole computational domain. The coal combustion is modelled using well-established, cost-effective combustion models. A specific feature of the devolatilization model is the optimisation of the kinetic constants for the furnace operating condition, which were obtained through an iterative procedure between particle heating rates from full large eddy simulation runs and the advanced model Chemical Percolation Devolatilization. In a previous work, we showed that the classical coal combustion models, when used in a high-resolution massively parallel large eddy simulation, lead to satisfactory predictions of the in-flame gas properties, namely gas temperature and gas species concentrations. In this work, we went beyond the comparisons between gas phase measurements and predictions. Single particles were tracked over time and instantaneous ensambles were collected to obtain a better understanding of the conditions that coal particles are subjected to in the investigated test case. The particles trajectory, combustion history and instantaneous state distribution were analysed. The volatile flame features were related with the characteristic trajectory of different sized particles. The combustion history revealed that particles are subjected to large variations of heating rates, including very short sequential periods alternating between heating and cooling during the early stages of combustion, due to the high turbulence intensity in the near burner region. Finally, the state distribution of the ensamble provided a global picture of the instantaneous coal combustion process.

Large-scale Experimental Investigations to Evaluate the Feasibility of Producing Methane-Rich Gas (SNG) through Underground Coal Gasification Process. Effect of Coal Rank and Gasification Pressure

An experimental campaign on the methane-oriented underground coal gasification (UCG) process was carried out in a large-scale laboratory installation. Two different types of coal were used for the oxygen/steam blown experiments, i.e., “Six Feet” semi-anthracite (Wales) and “Wesoła” hard coal (Poland). Four multi-day gasification tests (96 h continuous processes) were conducted in artificially created coal seams under two distinct pressure regimes-20 and 40 bar. The experiments demonstrated that the methane yields are significantly dependent on both the properties of coal (coal rank) and the pressure regime. The average CH4 concentration for “Six Feet” semi-anthracite was 15.8%vol. at 20 bar and 19.1%vol. at 40 bar. During the gasification of “Wesoła” coal, the methane concentrations were 10.9%vol. and 14.8%vol. at 20 and 40 bar, respectively. The “Six Feet” coal gasification was characterized by much higher energy efficiency than gasification of the “Wesoła” coal and for both tested coals, the efficiency increased with gasification pressure. The maximum energy efficiency of 71.6% was obtained for “Six Feet” coal at 40 bar. A positive effect of the increase in gasification pressure on the stabilization of the quantitative parameters of UCG gas was demonstrated.

“To Fly Under Borrowed Colours”: Insulin Discovery Accounts, Scientific Credit, and the Nobel Prize

Abstract The struggle over credit for the discovery of insulin serves as one of the ugliest examples of the tensions and rivalries inherent in the growth of large-scale laboratory science. An understanding of this historic controversy also lends insight into the use of informal self-narratives directed to the scientifıc community in the negotiation of credit for discovery. Such informal accounts constitute a distinct form of argumentative address that is separate both from formal oral and written presentations of research, also aimed at a scientifıc audience, and popularized accounts aimed at a lay audience. In providing informal self-narratives to their scientifıc peers, the four insulin principals discussed in this article apparently shared a tacit understanding of the narrative grounds on which they could base their claims for discovery credit. In this study, we uncover widespread thematic similarities within these narratives, possibly indicating a common set of criteria within the scientifıc community for judging not only formal scientifıc proof but also the narrative proof found in informal discovery accounts.

Burn Chamber Test of Ex Situ Thermal Impulse Sensors.

Recently, we reported on a novel ex situ thermal impulse sensing technique (based on lanthanide-doped oxide precursor nanoparticles) for use in structural fire forensics and demonstrated its functionality in small-scale lab-based tests. As a next step we have now performed a large-scale lab test at the US Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) Fire Research Laboratory using a burn chamber with three sand burners. In this test we demonstrate our technique's ability to determine the average temperature experienced by surfaces during the fire. While we successfully demonstrate our techniques accuracy, we also discover several previously unknown vulnerabilities. Namely, we find that: (1) our current method of embedding sensors in paint results in our sensor particles being difficult to recover (due to a large quantity of debris), (2) the current test panels have poor survivability, (3) debris from the fire tests interferes with excitation of dopant Dy ions (limiting our sensors' functionality), and (4) dispersal in paint results in suppression of the (metastable)tetragonal-to-monoclinic phase transition of ZrO2. To overcome these vulnerabilities we are evaluating new panel materials, paints, and lanthanide-dopants.

Large-scale laboratory tests of a new type of bucket foundation in sand subjected to vertical loading

As a new breakwater foundation form, a bucket foundation with two skirted side semicircles and a skirted middle rectangle was applied to the breakwater project at Xuyu Port, China. A series of laboratory tests were performed on the bucket foundation to investigate the vertical bearing capacity and the bucket-sand interaction mechanisms during the load bearing process. The main failure mode of the bucket foundation under vertical loading was general shear failure. The vertical loads increased with penetration displacement, ultimately reaching 330~404 kN with a displacement criterion of 0.06De (equivalent diameter of the foundation) at different incremental load steps. The inner soil pressures were clearly greater than the outer soil pressures induced by the skirt constraint effect. Regarding the bearing capacity, the outer skirt friction decreasing from approximately 0.05 to 0 with increasing penetration displacement, contributed only slightly, while the foundation base provided the majority. The cover plate resistance increased rapidly after the penetration displacement exceeded 25 mm, and its sharing ratio ultimately reached approximately 0.82. The tip resistance was estimated via the assistance of the cone resistance, and its sharing ratio decreased with penetration displacement. The inner friction and corresponding friction coefficient first increased and then decreased with penetration displacement, reaching a final sharing ratio of approximately 0.14.

Railway subgrade performance after repeated flooding – Large-scale laboratory testing

Abstract A rail track system comprises a number of components and, in order to analyse and predict track behaviour, it is essential to understand the function of each component as each will have a major influence on overall track performance. Historically, rail track substructure, particularly the subgrade, has been given less attention than the superstructure despite its importance in track design. This paper presents a full-scale experimental investigation to study the behaviour of subgrade in both saturated and unsaturated conditions, and how this behaviour changes with soil suction. Further, the investigation also studies the role of sand-blanketing during and after repeated flooding events. The results show that as soil suction reduces, flooding results in a continual reduction in both soil stiffness and track stiffness. It is also shown that the introduction of a sand-blanket has limited effectiveness as a drainage material, particularly after prolonged and repeated flooding.