Two-media boundary layer on a flat plate

OpenAIRE

Nikolay Ilyich Klyuev; Asgat Gatyatovich Gimadiev; Yuriy Alekseevich Kryukov

2014-01-01

The present paper provides a solution to the problem of a flow over a flat semi-infinite plate set at an angle to the horizon, and having a thin liquid film on its surface by external airflow. The film is formed by extrusion of liquid from the porous wall. The paper proposes a mathematical model of a two-media boundary layer flow. The main characteristics of the flow to a zero and a first approximation are determined. A drop of frictional stress is obtained.

Modeling the Geometry of Plate Boundary and Seismic Structure in the Southern Ryukyu Trench Subduction Zone, Japan, Using Amphibious Seismic Observations

Science.gov (United States)

Yamamoto, Y.; Takahashi, T.; Ishihara, Y.; Kaiho, Y.; Arai, R.; Obana, K.; Nakanishi, A.; Miura, S.; Kodaira, S.; Kaneda, Y.

2018-02-01

Here we present the new model, the geometry of the subducted Philippine Sea Plate interface beneath the southern Ryukyu Trench subduction zone, estimated from seismic tomography and focal mechanism estimation by using passive and active data from a temporary amphibious seismic network and permanent land stations. Using relocated low-angle thrust-type earthquakes, repeating earthquakes, and structural information, we constrained the geometry of plate boundary from the trench axis to a 60 km depth with uncertainties of less than 5 km. The estimated plate geometry model exhibited large variation, including a pronounced convex structure that may be evidence of a subducted seamount in the eastern portion of study area, whereas the western part appeared smooth. We also found that the active earthquake region near the plate boundary, defined by the distance from our plate geometry model, was clearly separated from the area dominated by short-term slow-slip events (SSEs). The oceanic crust just beneath the SSE-dominant region, the western part of the study area, showed high Vp/Vs ratios (>1.8), whereas the eastern side showed moderate or low Vp/Vs (<1.75). We interpreted this as an indication that high fluid pressures near the surface of the slab are contributing to the SSE activities. Within the toe of the mantle wedge, P and S wave velocities (<7.5 and <4.2 km/s, respectively) lower than those observed through normal mantle peridotite might suggest that some portions of the mantle may be at least 40% serpentinized.

Numerical modeling of intraplate seismicity with a deformable loading plate

Science.gov (United States)

So, B. D.; Capitanio, F. A.

2017-12-01

We use finite element modeling to investigate on the stress loading-unloading cycles and earthquakes occurrence in the plate interiors, resulting from the interactions of tectonic plates along their boundary. We model a visco-elasto-plastic plate embedding a single or multiple faults, while the tectonic stress is applied along the plate boundary by an external loading visco-elastic plate, reproducing the tectonic setting of two interacting lithospheres. Because the two plates deform viscously, the timescale of stress accumulation and release on the faults is self-consistently determined, from the boundary to the interiors, and seismic recurrence is an emerging feature. This approach overcomes the constraints on recurrence period imposed by stress (stress-drop) and velocity boundary conditions, while here it is unconstrained. We illustrate emerging macroscopic characteristics of this system, showing that the seismic recurrence period τ becomes shorter as Γ and Θ decreases, where Γ = ηI/ηL the viscosity ratio of the viscosities of the internal fault-embedded to external loading plates, respectively, and Θ = σY/σL the stress ratio of the elastic limit of the fault to far-field loading stress. When the system embeds multiple, randomly distributed faults, stress transfer results in recurrence period deviations, however the time-averaged recurrence period of each fault show the same dependence on Γ and Θ, illustrating a characteristic collective behavior. The control of these parameters prevails even when initial pre-stress was randomly assigned in terms of the spatial arrangement and orientation on the internal plate, mimicking local fluctuations. Our study shows the relevance of macroscopic rheological properties of tectonic plates on the earthquake occurrence in plate interiors, as opposed to local factors, proposing a viable model for the seismic behavior of continent interiors in the context of large-scale, long-term deformation of interacting tectonic

How diking affects the longer-term structure and evolution of divergent plate boundaries

KAUST Repository

Trippanera, Daniele

2015-04-01

Recurrent diking episodes along divergent plate boundaries, as at Dabbahu (2005, Afar) or at Bardarbunga (2014, Iceland) , highlight the possibility to have m-wide opening in a short time (days to weeks). This suggests a prominent role of magma enhancing transient plate separations. However, the role of diking on a longer term (> 102 years) and its influence on the structure and the evolution of a divergent plate boundary is still poorly investigated. Here we use field surveys along the oceanic Icelandic and continental Ethiopian plate boundaries, along five eruptive fissures and four rift segments. Field observations have also been integrated with analogue and numerical models of dike emplacement to better understand the effect of dike emplacement at depth and at the surface. Our results show that the dike-fed eruptive fissures are systematically associated with graben structures formed by inward dipping normal faults having throws up to 10 m and commonly propagating downward. Moreover, rift segments (i.e. mature rift zones), despite any asymmetry and repetition, are characterized by the same features as the eruptive fissures, the only difference lying in the larger size (higher fault throws, up to 40 m, and wider deformation zones). Analogue and numerical models of dike intrusion confirm that all the structural features observed along the rift segments may be dike-induced; these features include downward propagating normal faults bordering graben structures, contraction at the base of the hanging walls of the faults and upward propagating faults. Simple calculations based on the deeper structure of the eroded rift segments in eastern and western Iceland also suggest that all the fault slip in the active rift segments may result from diking. These results suggest that the overall deformation pattern of eruptive fissures and rift segments may be explained only by dike emplacement. In a magmatic rift, the regional tectonic stress may rarely be high enough to be

MHD Boundary Layer Slip Flow and Heat Transfer over a Flat Plate

International Nuclear Information System (INIS)

Bhattacharyya, Krishnendu; Mukhopadhyay, Swati; Layek, G. C.

2011-01-01

An analysis of magnetohydrodynamic (MHD) boundary layer flow and heat transfer over a flat plate with slip condition at the boundary is presented. A complete self-similar set of equations are obtained from the governing equations using similarity transformations and are solved by a shooting method. In the boundary slip condition no local similarity occurs. Velocity and temperature distributions within the boundary layer are presented. Our analysis reveals that the increase of magnetic and slip parameters reduce the boundary layer thickness and also enhance the heat transfer from the plate. (fundamental areas of phenomenology(including applications))

Effect of inherited structures on strike-slip plate boundaries: insight from analogue modelling of the central Levant Fracture System, Lebanon

Science.gov (United States)

Ghalayini, Ramadan; Daniel, Jean-Marc; Homberg, Catherine; Nader, Fadi

2015-04-01

Analogue sandbox modeling is a tool to simulate deformation style and structural evolution of sedimentary basins. The initial goal is to test what is the effect of inherited and crustal structures on the propagation, evolution, and final geometry of major strike-slip faults at the boundary between two tectonic plates. For this purpose, we have undertaken a series of analogue models to validate and reproduce the structures of the Levant Fracture System, a major NNE-SSW sinistral strike-slip fault forming the boundary between the Arabian and African plates. Onshore observations and recent high quality 3D seismic data in the Levant Basin offshore Lebanon demonstrated that Mesozoic ENE striking normal faults were reactivated into dextral strike-slip faults during the Late Miocene till present day activity of the plate boundary which shows a major restraining bend in Lebanon with a ~ 30°clockwise rotation in its trend. Experimental parameters consisted of a silicone layer at the base simulating the ductile crust, overlain by intercalated quartz sand and glass sand layers. Pre-existing structures were simulated by creating a graben in the silicone below the sand at an oblique (>60°) angle to the main throughgoing strike-slip fault. The latter contains a small stepover at depth to create transpression during sinistral strike-slip movement and consequently result in mountain building similarly to modern day Lebanon. Strike-slip movement and compression were regulated by steady-speed computer-controlled engines and the model was scanned using a CT-scanner continuously while deforming to have a final 4D model of the system. Results showed that existing normal faults were reactivated into dextral strike-slip faults as the sinistral movement between the two plates accumulated. Notably, the resulting restraining bend is asymmetric and segmented into two different compartments with differing geometries. One compartment shows a box fold anticline, while the second shows an

Architectural Blueprint for Plate Boundary Observatories based on interoperable Data Management Platforms

Science.gov (United States)

Kerschke, D. I.; Häner, R.; Schurr, B.; Oncken, O.; Wächter, J.

2014-12-01

Interoperable data management platforms play an increasing role in the advancement of knowledge and technology in many scientific disciplines. Through high quality services they support the establishment of efficient and innovative research environments. Well-designed research environments can facilitate the sustainable utilization, exchange, and re-use of scientific data and functionality by using standardized community models. Together with innovative 3D/4D visualization, these concepts provide added value in improving scientific knowledge-gain, even across the boundaries of disciplines. A project benefiting from the added value is the Integrated Plate boundary Observatory in Chile (IPOC). IPOC is a European-South American network to study earthquakes and deformation at the Chilean continental margin and to monitor the plate boundary system for capturing an anticipated great earthquake in a seismic gap. In contrast to conventional observatories that monitor individual signals only, IPOC captures a large range of different processes through various observation methods (e.g., seismographs, GPS, magneto-telluric sensors, creep-meter, accelerometer, InSAR). For IPOC a conceptual design has been devised that comprises an architectural blueprint for a data management platform based on common and standardized data models, protocols, and encodings as well as on an exclusive use of Free and Open Source Software (FOSS) including visualization components. Following the principles of event-driven service-oriented architectures, the design enables novel processes by sharing and re-using functionality and information on the basis of innovative data mining and data fusion technologies. This platform can help to improve the understanding of the physical processes underlying plate deformations as well as the natural hazards induced by them. Through the use of standards, this blueprint can not only be facilitated for other plate observing systems (e.g., the European Plate

An Irrotational Flow Field That Approximates Flat Plate Boundary Conditions

OpenAIRE

Ruffa, Anthony A.

2004-01-01

An irrotational solution is derived for the steady-state Navier-Stokes equations that approximately satisfies the boundary conditions for flow over a finite flat plate. The nature of the flow differs substantially from boundary layer flow, with severe numerical difficulties in some regions.

Seismic gaps and plate tectonics: seismic potential for major boundaries

Energy Technology Data Exchange (ETDEWEB)

McCann, W R; Nishenko, S P; Sykes, L R; Krause, J

1979-01-01

The theory of plate tectonics provides a basic framework for evaluating the potential for future great earthquakes to occur along major plate boundaries. Along most of the transform and convergent plate boundaries considered in this paper, the majority of seismic slip occurs during large earthquakes, i.e., those of magnitude 7 or greater. The concepts that rupture zones, as delineated by aftershocks, tend to abut rather than overlap, and large events occur in regions with histories of both long-and short-term seismic quiescence are used in this paper to delineate major seismic gaps. The term seismic gap is taken to refer to any region along an active plate boundary that has not experienced a large thrust or strike-slip earthquake for more than 30 years. A region of high seismic potential is a seismic gap that, for historic or tectonic reasons, is considered likely to produce a large shock during the next few decades. The seismic gap technique provides estimates of the location, size of future events and origin time to within a few tens of years at best. The accompanying map summarizes six categories of seismic potential for major plate boundaries in and around the margins of the Pacific Ocean and the Caribbean, South Sandwich and Sunda (Indonesia) regions for the next few decades. These six categories are meant to be interpreted as forecasts of the location and size of future large shocks and should not be considered to be predictions in which a precise estimate of the time of occurrence is specified. The categories of potential assigned here provide a rationale for assigning priorities for instrumentation, for future studies aimed at predicting large earthquakes and for making estimates of tsunami potential.

Experimental Results from a Flat Plate, Turbulent Boundary Layer Modified for the Purpose of Drag Reduction

Science.gov (United States)

Elbing, Brian R.

2006-11-01

Recent experiments on a flat plate, turbulent boundary layer at high Reynolds numbers (>10^7) were performed to investigate various methods of reducing skin friction drag. The methods used involved injecting either air or a polymer solution into the boundary layer through a slot injector. Two slot injectors were mounted on the model with one located 1.4 meters downstream of the nose and the second located 3.75 meters downstream. This allowed for some synergetic experiments to be performed by varying the injections from each slot and comparing the skin friction along the plate. Skin friction measurements were made with 6 shear stress sensors flush mounted along the stream-wise direction of the model.

Theroretical modelling of the plate-tubes coupling in the hydroelasticity of the perforated plates

International Nuclear Information System (INIS)

Dzhupanov, V.A.; Manoach, E.S.

1983-01-01

In the previous investigations on the perforated plate hydroelasticity the problem of the plates-tubes-liquid interaction in the process of the general structural vibration is stated. But the interaction of the vibrating plates with the tubes, passing through them, is taken into account considering the tubes only as absolutely rigid supports. This is one of the possible technical realizations. In the present article the case when the tubes are taking part in the plate motion (vibration) is studied. Two circular perforated plates are supported by the absolutely rigid wall of the modelled roundcircular reactor barrel. The distance between the plates is given. They are connected by tubes, passing through, and clamped into the perforation holes. The plates and the tubes are made by any elastic HOOKIAN material. The volume between the two plates and outwardly to the tubes, but intrinsically of the barrel is filled by ideal, compressible and heavy liquid. Evidently the liquid volume is multiconnected one. The free vibration of the whole system is considered with the purposes: i) to give a theoretical model of the plates-tubes-liquid interaction including governing equations and boundary conditions; ii) to trace the solution of the eigen-value problem for the modelled structure; iii) to underline the engineering sides of the modelling process. (orig./GL)

Large-eddy simulation of separation and reattachment of a flat plate turbulent boundary layer

KAUST Repository

Cheng, W.; Pullin, D. I.; Samtaney, Ravi

2015-01-01

© 2015 Cambridge University Press. We present large-eddy simulations (LES) of separation and reattachment of a flat-plate turbulent boundary-layer flow. Instead of resolving the near wall region, we develop a two-dimensional virtual wall model which

Unsteady heat-flux measurements of second-mode instability waves in a hypersonic flat-plate boundary layer

Science.gov (United States)

Kegerise, Michael A.; Rufer, Shann J.

2016-08-01

In this paper, we report on the application of the atomic layer thermopile (ALTP) heat-flux sensor to the measurement of laminar-to-turbulent transition in a hypersonic flat-plate boundary layer. The centerline of the flat-plate model was instrumented with a streamwise array of ALTP sensors, and the flat-plate model was exposed to a Mach 6 freestream over a range of unit Reynolds numbers. Here, we observed an unstable band of frequencies that are associated with second-mode instability waves in the laminar boundary layer that forms on the flat-plate surface. The measured frequencies, group velocities, phase speeds, and wavelengths of these instability waves are consistent with data previously reported in the literature. Heat flux time series, and the Morlet wavelet transforms of them, revealed the wave-packet nature of the second-mode instability waves. In addition, a laser-based radiative heating system was used to measure the frequency response functions (FRF) of the ALTP sensors used in the wind tunnel test. These measurements were used to assess the stability of the sensor FRFs over time and to correct spectral estimates for any attenuation caused by the finite sensor bandwidth.

Fundamental structure model of island arcs and subducted plates in and around Japan

Science.gov (United States)

Iwasaki, T.; Sato, H.; Ishiyama, T.; Shinohara, M.; Hashima, A.

2015-12-01

The eastern margin of the Asian continent is a well-known subduction zone, where the Pacific (PAC) and Philippine Sea (PHS) plates are being subducted. In this region, several island arcs (Kuril, Northeast Japan, Southwest Japan, Izu-Bonin and Ryukyu arcs) meet one another to form a very complicated tectonic environment. At 2014, we started to construct fundamental structure models for island arcs and subducted plates in and around Japan. Our research is composed of 6 items of (1) topography, (2) plate geometry, (3) fault models, (4) the Moho and brittle-ductile transition zone, (5) the lithosphere-asthenosphere boundary, and (6) petrological/rheological models. Such information is basic but inevitably important in qualitative understanding not only for short-term crustal activities in the subduction zone (particularly caused by megathrust earthquakes) but also for long-term cumulative deformation of the arcs as a result of strong plate-arc/arc-arc interactions. This paper is the first presentation of our research, mainly presenting the results of items (1) and (2). The area of our modelling is 12o-54o N and 118o-164o E to cover almost the entire part of Japanese Islands together with Kuril, Ryukyu and Izu-Bonin trenches. The topography model was constructed from the 500-m mesh data provided from GSJ, JODC, GINA and Alaska University. Plate geometry models are being constructed through the two steps. In the first step, we modelled very smooth plate boundaries of the Pacific and Philippine Sea plates in our whole model area using 42,000 earthquake data from JMA, USGS and ISC. For 7,800 cross sections taken with several directions to the trench axes, 2D plate boundaries were defined by fitting to the earthquake distribution (the Wadati-Benioff zone), from which we obtained equi-depth points of the plate boundary. These equi-depth points were then approximated by spline interpolation technique to eliminate shorter wave length undulation (75-150 km), but provide a

Stress rotation across the Cascadia megathrust requires a weak subduction plate boundary at seismogenic depths

Science.gov (United States)

Li, Duo; McGuire, Jeffrey J.; Liu, Yajing; Hardebeck, Jeanne L.

2018-03-01

The Mendocino Triple Junction region is the most seismically active part of the Cascadia Subduction Zone. The northward moving Pacific plate collides with the subducting Gorda plate causing intense internal deformation within it. Here we show that the stress field rotates rapidly with depth across the thrust interface from a strike-slip regime within the subducting plate, reflecting the Pacific plate collision, to a thrust regime in the overriding plate. We utilize a dense focal mechanism dataset, including observations from the Cascadia Initiative ocean bottom seismograph experiment, to constrain the stress orientations. To quantify the implications of this rotation for the strength of the plate boundary, we designed an inversion that solves for the absolute stress tensors in a three-layer model subject to assumptions about the strength of the subducting mantle. Our results indicate that the shear stress on the plate boundary fault is likely no more than about ∼50 MPa at ∼20 km depth. Regardless of the assumed mantle strength, we infer a relatively weak megathrust fault with an effective friction coefficient of ∼0 to 0.2 at seismogenic depths. Such a low value for the effective friction coefficient requires a combination of high fluid pressures and/or fault-zone minerals with low inherent friction in the region where a great earthquake is expected in Cascadia.

Stress rotation across the Cascadia megathrust requires a weak subduction plate boundary at seismogenic depths

Science.gov (United States)

Li, Duo; McGuire, Jeffrey J.; Liu, Yajing; Hardebeck, Jeanne L.

2018-01-01

The Mendocino Triple Junction region is the most seismically active part of the Cascadia Subduction Zone. The northward moving Pacific plate collides with the subducting Gorda plate causing intense internal deformation within it. Here we show that the stress field rotates rapidly with depth across the thrust interface from a strike-slip regime within the subducting plate, reflecting the Pacific plate collision, to a thrust regime in the overriding plate. We utilize a dense focal mechanism dataset, including observations from the Cascadia Initiative ocean bottom seismograph experiment, to constrain the stress orientations. To quantify the implications of this rotation for the strength of the plate boundary, we designed an inversion that solves for the absolute stress tensors in a three-layer model subject to assumptions about the strength of the subducting mantle. Our results indicate that the shear stress on the plate boundary fault is likely no more than about ∼50 MPa at ∼20 km depth. Regardless of the assumed mantle strength, we infer a relatively weak megathrust fault with an effective friction coefficient of ∼0 to 0.2 at seismogenic depths. Such a low value for the effective friction coefficient requires a combination of high fluid pressures and/or fault-zone minerals with low inherent friction in the region where a great earthquake is expected in Cascadia.

Vibration modes of a single plate with general boundary conditions

Directory of Open Access Journals (Sweden)

Phamová L.

2016-06-01

Full Text Available This paper deals with free flexural vibration modes and natural frequencies of a thin plate with general boundary conditions — a simply supported plate connected to its surroundings with torsional springs. Vibration modes were derived on the basis of the Rajalingham, Bhat and Xistris approach. This approach was originally used for a clamped thin plate, so its adaptation was needed. The plate vibration function was usually expressed as a single partial differential equation. This partial differential equation was transformed into two ordinary differential equations that can be solved in the simpler way. Theoretical background of the computations is briefly described. Vibration modes of the supported plate with torsional springs are presented graphically and numerically for three different values of stiffness of torsional springs.

Transitional and turbulent flat-plate boundary layers with heat transfer

Science.gov (United States)

Wu, Xiaohua; Moin, Parviz

2010-11-01

We report on our direct numerical simulation of two incompressible, nominally zero-pressure-gradient flat-plate boundary layers from momentum thickness Reynolds number 80 to 1950. Heat transfer between the constant-temperature solid surface and the free-stream is also simulated with molecular Prandtl number=1. Throughout the entire flat-plate, the ratio of Stanton number and skin-friction St/Cfdeviates from the exact Reynolds analogy value of 0.5 by less than 1.5%. Turbulent Prandtl number t peaks at the wall. Preponderance of hairpin vortices is observed in both the transitional and turbulent regions of the boundary layers. In particular, the internal structure of merged turbulent spots is hairpin forest; the internal structure of infant turbulent spots is hairpin packet. Numerous hairpin vortices are readily detected in both the near-wall and outer regions of the boundary layers up to momentum thickness Reynolds number 1950. This suggests that the hairpin vortices in the turbulent region are not simply the aged hairpin forests convected from the upstream transitional region. Temperature iso-surfaces in the companion thermal boundary layers are found to be a useful tracer in identifying hairpin vortex structures.

Buckling transition and boundary layer in non-Euclidean plates.

Science.gov (United States)

Efrati, Efi; Sharon, Eran; Kupferman, Raz

2009-07-01

Non-Euclidean plates are thin elastic bodies having no stress-free configuration, hence exhibiting residual stresses in the absence of external constraints. These bodies are endowed with a three-dimensional reference metric, which may not necessarily be immersible in physical space. Here, based on a recently developed theory for such bodies, we characterize the transition from flat to buckled equilibrium configurations at a critical value of the plate thickness. Depending on the reference metric, the buckling transition may be either continuous or discontinuous. In the infinitely thin plate limit, under the assumption that a limiting configuration exists, we show that the limit is a configuration that minimizes the bending content, among all configurations with zero stretching content (isometric immersions of the midsurface). For small but finite plate thickness, we show the formation of a boundary layer, whose size scales with the square root of the plate thickness and whose shape is determined by a balance between stretching and bending energies.

Large-eddy simulation of separation and reattachment of a flat plate turbulent boundary layer

KAUST Repository

Cheng, W.

2015-11-11

© 2015 Cambridge University Press. We present large-eddy simulations (LES) of separation and reattachment of a flat-plate turbulent boundary-layer flow. Instead of resolving the near wall region, we develop a two-dimensional virtual wall model which can calculate the time- and space-dependent skin-friction vector field at the wall, at the resolved scale. By combining the virtual-wall model with the stretched-vortex subgrid-scale (SGS) model, we construct a self-consistent framework for the LES of separating and reattaching turbulent wall-bounded flows at large Reynolds numbers. The present LES methodology is applied to two different experimental flows designed to produce separation/reattachment of a flat-plate turbulent boundary layer at medium Reynolds number Reθ based on the momentum boundary-layer thickness θ. Comparison with data from the first case at demonstrates the present capability for accurate calculation of the variation, with the streamwise co-ordinate up to separation, of the skin friction coefficient, Reθ, the boundary-layer shape factor and a non-dimensional pressure-gradient parameter. Additionally the main large-scale features of the separation bubble, including the mean streamwise velocity profiles, show good agreement with experiment. At the larger Reθ = 11000 of the second case, the LES provides good postdiction of the measured skin-friction variation along the whole streamwise extent of the experiment, consisting of a very strong adverse pressure gradient leading to separation within the separation bubble itself, and in the recovering or reattachment region of strongly-favourable pressure gradient. Overall, the present two-dimensional wall model used in LES appears to be capable of capturing the quantitative features of a separation-reattachment turbulent boundary-layer flow at low to moderately large Reynolds numbers.

Crustal and upper mantle investigations of the Caribbean-South American plate boundary

Science.gov (United States)

Bezada, Maximiliano J.

The evolution of the Caribbean --- South America plate boundary has been a matter of vigorous debate for decades and many questions remain unresolved. In this work, and in the framework of the BOLIVAR project, we shed light on some aspects of the present state and the tectonic history of the margin by using different types of geophysical data sets and techniques. An analysis of controlled-source traveltime data collected along a boundary-normal profile at ˜65°W was used to build a 2D P-wave velocity model. The model shows that the Caribbean Large Igenous Province is present offshore eastern Venezuela and confirms the uniformity of the velocity structure along the Leeward Antilles volcanic belt. In contrast with neighboring profiles, at this longitude we see no change in velocity structure or crustal thickness across the San Sebastian - El Pilar fault system. A 2D gravity modeling methodology that uses seismically derived initial density models was developed as part of this research. The application of this new method to four of the BOLIVAR boundary-normal profiles suggests that the uppermost mantle is denser under the South American continental crust and the island arc terranes than under the Caribbean oceanic crust. Crustal rocks of the island arc and extended island arc terranes of the Leeward Antilles have a relatively low density, given their P-wave velocity. This may be caused by low iron content, relative to average magmatic arc rocks. Finally, an analysis of teleseismic traveltimes with frequency-dependent kernels produced a 3D P-wave velocity perturbation model. The model shows the structure of the mantle lithosphere under the study area and clearly images the subduction of the Atlantic slab and associated partial removal of the lower lithosphere under northern South America. We also image the subduction of a section of the Caribbean plate under South America with an east-southeast direction. Both the Atlantic and Caribbean subducting slabs penetrate the

Strength and Deformation Rate of Plate Boundaries: The Rheological Effects of Grain Size Reduction, Structure, and Serpentinization.

Science.gov (United States)

Montesi, L.; Gueydan, F.

2016-12-01

Global strain rate maps reveal 1000-fold contrasts between plate interiors, oceanic or continental diffuse plate boundaries and narrow plate boundaries. Here, we show that rheological models based on the concepts of shear zone localization and the evolution of rock structure upon strain can explain these strain rate contrasts. Ductile shear zones constitute a mechanical paradox in the lithosphere. As every plastic deformation mechanism is strain-rate-hardening, ductile rocks are expected to deform at low strain rate and low stress (broad zone of deformation). Localized ductile shear zones require either a localized forcing (locally high stress) or a thermal or structural anomaly in the shear zone; either can be inherited or develop progressively as rocks deform. We previously identified the most effective process at each depth level of the lithosphere. In the upper crust and middle crust, rocks fabric controls localization. Grain size reduction is the most efficient mechanism in the uppermost mantle. This analysis can be generalized to consider a complete lithospheric section. We assume strain rate does not vary with depth and that the depth-integrated strength of the lithospheric does not change over time, as the total force is controlled by external process such as mantle convection and plate and slab buoyancy. Reducing grain size from a coarse value typical of undeformed peridotite to a value in agreement with the stress level (piezometer) while letting that stress vary from depth to depth (the integrated stress remains the same) increases the lithospheric strain rate by about a factor of 1000. This can explain the development of diffuse plate boundaries. The slightly higher strain rate of continental plate boundary may reflect development of a layered rock fabric in the middle crust. Narrow plate boundaries require additional weakening process. The high heat flux near mid-ocean ridge implies a thin lithosphere, which enhances stress (for constant integrated

Investigation of turbulence models with compressibility corrections for hypersonic boundary flows

Directory of Open Access Journals (Sweden)

Han Tang

2015-12-01

Full Text Available The applications of pressure work, pressure-dilatation, and dilatation-dissipation (Sarkar, Zeman, and Wilcox models to hypersonic boundary flows are investigated. The flat plate boundary layer flows of Mach number 5–11 and shock wave/boundary layer interactions of compression corners are simulated numerically. For the flat plate boundary layer flows, original turbulence models overestimate the heat flux with Mach number high up to 10, and compressibility corrections applied to turbulence models lead to a decrease in friction coefficients and heating rates. The pressure work and pressure-dilatation models yield the better results. Among the three dilatation-dissipation models, Sarkar and Wilcox corrections present larger deviations from the experiment measurement, while Zeman correction can achieve acceptable results. For hypersonic compression corner flows, due to the evident increase of turbulence Mach number in separation zone, compressibility corrections make the separation areas larger, thus cannot improve the accuracy of calculated results. It is unreasonable that compressibility corrections take effect in separation zone. Density-corrected model by Catris and Aupoix is suitable for shock wave/boundary layer interaction flows which can improve the simulation accuracy of the peak heating and have a little influence on separation zone.

Generalized wall function and its application to compressible turbulent boundary layer over a flat plate

Science.gov (United States)

Liu, J.; Wu, S. P.

2017-04-01

Wall function boundary conditions including the effects of compressibility and heat transfer are improved for compressible turbulent boundary flows. Generalized wall function formulation at zero-pressure gradient is proposed based on coupled velocity and temperature profiles in the entire near-wall region. The parameters in the generalized wall function are well revised. The proposed boundary conditions are integrated into Navier-Stokes computational fluid dynamics code that includes the shear stress transport turbulence model. Numerical results are presented for a compressible boundary layer over a flat plate at zero-pressure gradient. Compared with experimental data, the computational results show that the generalized wall function reduces the first grid spacing in the directed normal to the wall and proves the feasibility and effectivity of the generalized wall function method.

Modeling of the heat transfer in bypass transitional boundary-layer flows

Science.gov (United States)

Simon, Frederick F.; Stephens, Craig A.

1991-01-01

A low Reynolds number k-epsilon turbulence model and conditioned momentum, energy and turbulence equations were used to predict bypass transition heat transfer on a flat plate in a high-disturbance environment with zero pressure gradient. The use of conditioned equations was demonstrated to be an improvement over the use of the global-time-averaged equations for the calculation of velocity profiles and turbulence intensity profiles in the transition region of a boundary layer. The approach of conditioned equations is extended to include heat transfer and a modeling of transition events is used to predict transition onset and the extent of transition on a flat plate. The events, which describe the boundary layer at the leading edge, result in boundary-layer regions consisting of: (1) the laminar, (2) pseudolaminar, (3) transitional, and (4) turbulent boundary layers. The modeled transition events were incorporated into the TEXSTAN 2-D boundary-layer code which is used to numerically predict the heat transfer. The numerical predictions in general compared well with the experimental data and revealed areas where additional experimental information is needed.

Frequency response of rectangular plates with free-edge openings and carlings subjected to point excitation force and enforced displacement at boundaries

Directory of Open Access Journals (Sweden)

Dae Seung Cho

2016-03-01

Full Text Available In this paper, a numerical procedure for the natural vibration analysis of plates with openings and carlings based on the assumed mode method is extended to assess their forced response. Firstly, natural response of plates with openings and carlings is calculated from the eigenvalue equation derived by using Lagrange's equation of motion. Secondly, the mode superposition method is applied to determine frequency response. Mindlin theory is adopted for plate modelling and the effect of openings is taken into account by subtracting their potential and kinetic energies from the corresponding plate energies. Natural and frequency response of plates with openings and carlings subjected to point excitation force and enforced acceleration at boundaries, respectively, is analysed by using developed in-house code. For the validation of the developed method and the code, extensive numerical results, related to plates with different opening shape, carlings and boundary conditions, are compared with numerical data from the relevant literature and with finite element solutions obtained by general finite element tool.

Prandtl boundary layer expansions of steady Navier-Stokes flows over a moving plate

OpenAIRE

Guo, Yan; Nguyen, Toan T.

2014-01-01

This paper concerns the validity of the Prandtl boundary layer theory in the inviscid limit for steady incompressible Navier-Stokes flows. The stationary flows, with small viscosity, are considered on $[0,L]\\times \\mathbb{R}_{+}$, assuming a no-slip boundary condition over a moving plate at $y=0$. We establish the validity of the Prandtl boundary layer expansion and its error estimates.

Defects and boundary layers in non-Euclidean plates

International Nuclear Information System (INIS)

Gemmer, J A; Venkataramani, S C

2012-01-01

We investigate the behaviour of non-Euclidean plates with constant negative Gaussian curvature using the Föppl–von Kármán reduced theory of elasticity. Motivated by recent experimental results, we focus on annuli with a periodic profile. We prove rigorous upper and lower bounds for the elastic energy that scales like the thickness squared. In particular we show that are only two types of global minimizers—deformations that remain flat and saddle shaped deformations with isolated regions of stretching near the edge of the annulus. We also show that there exist local minimizers with a periodic profile that have additional boundary layers near their lines of inflection. These additional boundary layers are a new phenomenon in thin elastic sheets and are necessary to regularize jump discontinuities in the azimuthal curvature across lines of inflection. We rigorously derive scaling laws for the width of these boundary layers as a function of the thickness of the sheet. (paper)

Geological and Structural evolution of the Eurasia Africa plate boundary in the Gulf of Cadiz Central Eastern Atlantic Sea.

OpenAIRE

D’Oriano, Filippo

2010-01-01

Iberia Africa plate boundary, cross, roughly W-E, connecting the eastern Atlantic Ocean from Azores triple junction to the Continental margin of Morocco. Relative movement between the two plate change along the boundary, from transtensive near the Azores archipelago, through trascurrent movement in the middle at the Gloria Fracture Zone, to transpressive in the Gulf of Cadiz area. This study presents the results of geophysical and geological analysis on the plate boundary area offshore Gibral...

Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake.

Science.gov (United States)

Schurr, Bernd; Asch, Günter; Hainzl, Sebastian; Bedford, Jonathan; Hoechner, Andreas; Palo, Mauro; Wang, Rongjiang; Moreno, Marcos; Bartsch, Mitja; Zhang, Yong; Oncken, Onno; Tilmann, Frederik; Dahm, Torsten; Victor, Pia; Barrientos, Sergio; Vilotte, Jean-Pierre

2014-08-21

On 1 April 2014, Northern Chile was struck by a magnitude 8.1 earthquake following a protracted series of foreshocks. The Integrated Plate Boundary Observatory Chile monitored the entire sequence of events, providing unprecedented resolution of the build-up to the main event and its rupture evolution. Here we show that the Iquique earthquake broke a central fraction of the so-called northern Chile seismic gap, the last major segment of the South American plate boundary that had not ruptured in the past century. Since July 2013 three seismic clusters, each lasting a few weeks, hit this part of the plate boundary with earthquakes of increasing peak magnitudes. Starting with the second cluster, geodetic observations show surface displacements that can be associated with slip on the plate interface. These seismic clusters and their slip transients occupied a part of the plate interface that was transitional between a fully locked and a creeping portion. Leading up to this earthquake, the b value of the foreshocks gradually decreased during the years before the earthquake, reversing its trend a few days before the Iquique earthquake. The mainshock finally nucleated at the northern end of the foreshock area, which skirted a locked patch, and ruptured mainly downdip towards higher locking. Peak slip was attained immediately downdip of the foreshock region and at the margin of the locked patch. We conclude that gradual weakening of the central part of the seismic gap accentuated by the foreshock activity in a zone of intermediate seismic coupling was instrumental in causing final failure, distinguishing the Iquique earthquake from most great earthquakes. Finally, only one-third of the gap was broken and the remaining locked segments now pose a significant, increased seismic hazard with the potential to host an earthquake with a magnitude of >8.5.

Heat conduction in a plate-type fuel element with time-dependent boundary conditions

International Nuclear Information System (INIS)

Faya, A.J.G.; Maiorino, J.R.

1981-01-01

A method for the solution of boundary-value problems with variable boundary conditions is applied to solve a heat conduction problem in a plate-type fuel element with time dependent film coefficient. The numerical results show the feasibility of the method in the solution of this class of problems. (Author) [pt

Thrust-wrench interference tectonics in the Gulf of Cadiz (Africa-Iberia plate boundary in the North-East Atlantic): Insights from analog models

OpenAIRE

Duarte , João ,; Rosas , Filipe ,; Terrinha , Pedro; Gutscher , Marc-André ,; Malavielle , Jacques; Silva , Sonia; Matias , Luis

2011-01-01

International audience; In the Gulf of Cadiz key segment of the Africa-Iberia plate boundary (North-East Atlantic ocean), three main different modes of tectonic interference between a recently identified wrench system (SWIM) and the Gulf of Cadiz Accretionary Wedge (GCAW) were tested through analog sand-box modeling: a) An active accretionary wedge on top of a pre-existent inactive basement fault; b) An active strike-slip fault cutting a previously formed, inactive, accretionary wedge; and c)...

Free Convection over a Permeable Horizontal Flat Plate Embedded in a Porous Medium with Radiation Effects and Mixed Thermal Boundary Conditions

OpenAIRE

Najiyah S. Khasi'ie; Roziena Khairuddin; Najihah Mohamed; Mohd Zuki Salleh; Roslinda Nazar; Ioan Pop

2012-01-01

Problem statement: In this study, the mathematical modeling of free convection boundary layer flow over a permeable horizontal flat plate embedded in a porous medium under mixed thermal boundary conditions and radiation effects is considered. Approach: The transformed boundary layer equations are solved numerically using the shooting method. Results: Numerical solutions are obtained for the wall temperature, the heat transfer coefficient, as well as the velocity and temperature profiles. The ...

a Lattice Boltzmann Study of the 2d Boundary Layer Created by AN Oscillating Plate

Science.gov (United States)

Cappietti, L.; Chopard, B.

We study the applicability of the Lattice Boltzmann Method (LBM) to simulate the 2D laminar boundary layer induced by an oscillating flat plate. We also investigate the transition to the disturbed laminar regime that occurs with a rough oscillating plate. The simulations were performed in two cases: first with a fluid otherwise at rest and second in presence of superimposed current. The generation of coherent vortex structures and their evolution are commented. The accuracy of the method was checked by comparisons with the exact analytical solution of the Navier-Stokes equations for the so-called Stokes' Second Problem. The comparisons show that LBM reproduces this time varying flow with first order accuracy. In the case of the wavy-plate, the results show that a mechanism of vortex-jet formations, low speed-streak and shear instability sustain a systems of stationary vortices outside the boundary layer. The vortex-jet takes place at the end of the decelerating phase whereas the boundary layer turns out to be laminar when the plate accelerates. In the presence of the superimposed current, the vortex-jet mechanism is still effective but the vortices outside the boundary layer are only present during part of the oscillating period. During the remaining part, the flow turns out to be laminar although a wave perturbation in the velocity field is present.

Boundary integral equation methods and numerical solutions thin plates on an elastic foundation

CERN Document Server

Constanda, Christian; Hamill, William

2016-01-01

This book presents and explains a general, efficient, and elegant method for solving the Dirichlet, Neumann, and Robin boundary value problems for the extensional deformation of a thin plate on an elastic foundation. The solutions of these problems are obtained both analytically—by means of direct and indirect boundary integral equation methods (BIEMs)—and numerically, through the application of a boundary element technique. The text discusses the methodology for constructing a BIEM, deriving all the attending mathematical properties with full rigor. The model investigated in the book can serve as a template for the study of any linear elliptic two-dimensional problem with constant coefficients. The representation of the solution in terms of single-layer and double-layer potentials is pivotal in the development of a BIEM, which, in turn, forms the basis for the second part of the book, where approximate solutions are computed with a high degree of accuracy. The book is intended for graduate students and r...

Turbulent thermal boundary layer on a permeable flat plate

International Nuclear Information System (INIS)

Vigdorovich, I. I.

2007-01-01

Scaling laws are established for the profiles of temperature, turbulent heat flux, rms temperature fluctuation, and wall heat transfer in the turbulent boundary layer on a flat plate with transpiration. In the case of blowing, the temperature distribution represented in scaling variables outside the viscous sublayer has a universal form known from experimental data for flows over impermeable flat plates. In the case of suction, the temperature distribution is described by a one-parameter family of curves. A universal law of heat transfer having the form of a generalized Reynolds analogy provides a basis for representation of the heat flux distributions corresponding to different Reynolds numbers and transpiration velocities in terms of a function of one variable. The results are obtained without invoking any special closure hypotheses

Three-Dimensional Vibration Analysis of Rectangular Thick Plates on Pasternak Foundation with Arbitrary Boundary Conditions

Directory of Open Access Journals (Sweden)

Huimin Liu

2017-01-01

Full Text Available This paper presents the first known vibration characteristic of rectangular thick plates on Pasternak foundation with arbitrary boundary conditions on the basis of the three-dimensional elasticity theory. The arbitrary boundary conditions are obtained by laying out three types of linear springs on all edges. The modified Fourier series are chosen as the basis functions of the admissible function of the thick plates to eliminate all the relevant discontinuities of the displacements and their derivatives at the edges. The exact solution is obtained based on the Rayleigh–Ritz procedure by the energy functions of the thick plate. The excellent accuracy and reliability of current solutions are demonstrated by numerical examples and comparisons with the results available in the literature. In addition, the influence of the foundation coefficients as well as the boundary restraint parameters is also analyzed, which can serve as the benchmark data for the future research technique.

Fluid flow and heat transfer of carbon nanotubes along a flat plate with Navier slip boundary

Science.gov (United States)

Khan, W. A.; Khan, Z. H.; Rahi, M.

2014-06-01

Homogeneous flow model is used to study the flow and heat transfer of carbon nanotubes (CNTs) along a flat plate subjected to Navier slip and uniform heat flux boundary conditions. This is the first paper on the flow and heat transfer of CNTs along a flat plate. Two types of CNTs, namely, single- and multi-wall CNTs are used with water, kerosene or engine oil as base fluids. The empirical correlations are used for the thermophysical properties of CNTs in terms of the solid volume fraction of CNTs. For the effective thermal conductivity of CNTs, Xue (Phys B Condens Matter 368:302-307, 2005) model has been used and the results are compared with the existing theoretical models. The governing partial differential equations and boundary conditions are converted into a set of nonlinear ordinary differential equations using suitable similarity transformations. These equations are solved numerically using a very efficient finite difference method with shooting scheme. The effects of the governing parameters on the dimensionless velocity, temperature, skin friction, and Nusselt numbers are investigated and presented in graphical and tabular forms. The numerical results of skin friction and Nusselt numbers are compared with the available data for special cases and are found in good agreement.

Modeling particulate removal in plate-plate and wire-plate electrostatic precipitators

Directory of Open Access Journals (Sweden)

S Ramechecandane

2016-09-01

Full Text Available The present study is concerned with the modeling of electrically charged particles in a model plate-plate and a single wire-plate electrostatic precipitator (ESP. The particle concentration distributions for both a plate-plate and a wire-plate ESP are calculated using a modified drift flux model. Numerical investigations are performed using the modified drift flux model for particle number concentration, in addition to the RNG k - ε model for the mean turbulent flow field and the Poisson equation for the electric field. The proposed model and the outlined methodology for coupling the flow field, electric field, charging kinetics and particle concentration is applied to two model precipitators that are truly representative of a wide class of commercialized ESPs. The present investigation is quite different from the earlier studies as it does not make assumptions like a homogeneous electric field or an infinite turbulent diffusivity. The electric field calculated is a strong function of position and controls the migration velocity of particles. Hence, the proposed model can be implemented in a flow solver to obtain a full-fledged solution for any kind of ESP with no limitations on the particle number concentration, as encountered in a Lagrangian approach. The effect of turbulent diffusivity on particle number concentration in a plate-plate ESP is investigated in detail and the results obtained are compared with available experimental data. Similarly, the effect of particle size/diameter and applied electric potential on the accumulative collection performance in the case of a wire-plate ESP is studied and the results obtained are compared with available numerical data. The numerical results obtained using the modified drift flux model for both the plate-plate and wire-plate ESP are in close agreement with available experimental and numerical data.

Relaxation of an unsteady turbulent boundary layer on a flat plate in an expansion tube

Science.gov (United States)

Gurta, R. N.; Trimpi, R. L.

1974-01-01

An analysis is presented for the relaxation of a turbulent boundary layer on a semi-infinite flat plate after passage of a shock wave and a trailing driver gas-driven gas interface. The problem has special application to expansion-tube flows. The flow-governing equations have been transformed into the Crocco variables, and a time-similar solution is presented in terms of the dimensionless distance-time variable alpha and the dimensionless velocity variable beta. An eddy-viscosity model, similar to that of time-steady boundary layers, is applied to the inner and outer regions of the boundary layer. A turbulent Prandtl number equal to the molecular Prandtl number is used to relate the turbulent heat flux to the eddy viscosity. The numerical results, obtained by using the Gauss-Seidel line-relaxation method, indicate that a fully turbulent boundary layer relaxes faster to the final steady-state values of heat transfer and skin friction than a laminar boundary layer. The results also give a fairly good estimate of the local skin friction and heat transfer for near steady-flow conditions.

Major earthquakes occur regularly on an isolated plate boundary fault.

Science.gov (United States)

Berryman, Kelvin R; Cochran, Ursula A; Clark, Kate J; Biasi, Glenn P; Langridge, Robert M; Villamor, Pilar

2012-06-29

The scarcity of long geological records of major earthquakes, on different types of faults, makes testing hypotheses of regular versus random or clustered earthquake recurrence behavior difficult. We provide a fault-proximal major earthquake record spanning 8000 years on the strike-slip Alpine Fault in New Zealand. Cyclic stratigraphy at Hokuri Creek suggests that the fault ruptured to the surface 24 times, and event ages yield a 0.33 coefficient of variation in recurrence interval. We associate this near-regular earthquake recurrence with a geometrically simple strike-slip fault, with high slip rate, accommodating a high proportion of plate boundary motion that works in isolation from other faults. We propose that it is valid to apply time-dependent earthquake recurrence models for seismic hazard estimation to similar faults worldwide.

A Geodetic Strain Rate Model for the Pacific-North American Plate Boundary, western United States

Science.gov (United States)

Kreemer, C.; Hammond, W. C.; Blewitt, G.; Holland, A. A.; Bennett, R. A.

2012-04-01

We present a model of crustal strain rates derived from GPS measurements of horizontal station velocities in the Pacific-North American plate boundary in the western United States. The model reflects a best estimate of present-day deformation from the San Andreas fault system in the west to the Basin and Range province in the east. Of the total 2,846 GPS velocities used in the model, 1,197 are derived by ourselves, and 1,649 are taken from (mostly) published results. The velocities derived by ourselves (the "UNR solution") are estimated from GPS position time-series of continuous and semi-continuous stations for which data are publicly available. We estimated ITRF2005 positions from 2002-2011.5 using JPL's GIPSY-OASIS II software with ambiguity resolution applied using our custom Ambizap software. Only stations with time-series that span at least 2.25 years are considered. We removed from the time-series continental-scale common-mode errors using a spatially-varying filtering technique. Velocity uncertainties (typically 0.1-0.3 mm/yr) assume that the time-series contain flicker plus white noise. We used a subset of stations on the stable parts of the Pacific and North American plates to estimate the Pacific-North American pole of rotation. This pole is applied as a boundary condition to the model and the North American - ITRF2005 pole is used to rotate our velocities into a North America fixed reference frame. We do not include parts of the time-series that show curvature due to post-seismic deformation after major earthquakes and we also exclude stations whose time-series display a significant unexplained non-linearity or that are near volcanic centers. Transient effects longer than the observation period (i.e., slow viscoelastic relaxation) are left in the data. We added to the UNR solution velocities from 12 other studies. The velocities are transformed onto the UNR solution's reference frame by estimating and applying a translation and rotation that minimizes

Plate boundary deformation at the latitude of the Salton Trough - northern Gulf of California (Invited)

Science.gov (United States)

Stock, J. M.

2013-12-01

Along the Pacific-North America plate boundary zone, the segment including the southern San Andreas fault to Salton Trough and northern Gulf of California basins has been transtensional throughout its evolution, based on Pacific-North America displacement vectors calculated from the global plate circuit (900 × 20 km at N54°W since 20 Ma; 460 × 20 km at N48°W since 11 Ma). Nevertheless, active seismicity and focal mechanisms show a broad zone of plate boundary deformation within which the inferred stress regime varies locally (Yang & Hauksson 2013 GJI), and fault patterns in some regions suggest ongoing tectonic rotation. Similar behavior is inferred to have occurred in this zone over most of its history. Crustal structure in this region is constrained by surface geology, geophysical experiments (e.g., the 2011 Salton Seismic Imaging Project (SSIP), USGS Imperial Valley 1979, PACE), and interdisciplinary marine and onland studies in Mexico (e.g., NARS-Baja, Cortes, and surveys by PEMEX). Magnetic data (e.g., EMAG-2) aids in the recognition of large-scale crustal provinces and fault boundaries in regions lacking detailed geophysical surveys. Consideration of existing constraints on crustal thickness and architecture, and fault and basin evolution suggests that to reconcile geological deformation with plate motion history, the following additional factors need to be taken into account. 1) Plate boundary displacement via interacting systems of rotating blocks, coeval with slip on steep strike slip faults, and possibly related to slip on low angle extensional faults (e.g, Axen & Fletcher 1998 IGR) may be typical prior to the onset of seafloor spreading. This fault style may have accommodated up to 150 km of plate motion in the Mexican Continental Borderland and north of the Vizcaino Peninsula, likely between 12 and 15 Ma, as well as explaining younger rotations adjacent to the Gulf of California and current deformation southwest of the Salton Sea. 2) Geophysical

Boundary layer on a flat plate with suction

International Nuclear Information System (INIS)

Favre, A.; Dumas, R.; Verollet, E.

1961-01-01

This research done in wind tunnel concerns the turbulent boundary layer of a porous flat plate with suction. The porous wall is 1 m long and begins 1 m downstream of the leading edge. The Reynolds number based on the boundary layer thickness is of the order of 16.300. The suction rate defined as the ratio of the velocity perpendicular to the wall to the external flow velocity ranges from 0 to 2 per cent. The pressure gradient can be controlled. The mean velocity profiles have been determined for various positions and suction rates by means of total pressure probes together with the intensities of the turbulent velocity fluctuations components, energy spectra and correlations by means of hot wire anemometers, spectral analyser and correlator. The stream lines, the values of the viscous and turbulent shear stresses, of the local wall friction, of the turbulent energy production term, with some information on the dissipation of the energy have been derived from these measurements. For these data the integral of equation of continuity in boundary layer have been drawn. The suction effects on the boundary layer are important. The suction thoroughly alters the mean velocity profiles by increasing the viscous shear stresses near the wall and decreasing them far from the wall, it diminishes the longitudinal and transversal turbulence intensities, the turbulent shear stresses, and the production of energy of turbulence. These effects are much stressed in the inner part of the boundary layer. On the other hand the energy spectra show that the turbulence scale is little modified, the boundary layer thickness being not much diminished by the suction. The suction effects can be appreciated by comparing twice the suction rate to the wall friction coefficient (assumed airtight), quite noticeable as soon as the rate is about unity, they become very important when it reaches ten. (author) [fr

Seismicity and Seismic Hazard along the Western part of the Eurasia-Nubia plate boundary

Science.gov (United States)

Bezzeghoud, Mourad; Fontiela, João; Ferrão, Celia; Borges, José Fernando; Caldeira, Bento; Dib, Assia; Ousadou, Farida

2016-04-01

The seismic phenomenon is the most damaging natural hazard known in the Mediterranean area. The western part of the Eurasia-Nubia plate boundary extends from the Azores to the Mediterranean region. The oceanic part of the plate boundary is well delimited from the Azores Islands, along the Azores-Gibraltar fault to approximately 12°W (west of the Strait of Gibraltar). From 12°W to 3.5°E, including the Iberia-Nubia region and extending to the western part of Algeria, the boundary is more diffuse and forms a wider area of deformation. The boundary between the Iberia and Nubia plates is the most complex part of the margin. This region corresponds to the transition from an oceanic boundary to a continental boundary, where Iberia and Nubia collide. Although most earthquakes along this plate boundary are shallow and generally have magnitudes less than 5.5, there have been several high-magnitude events. Many devastating earthquakes, some of them tsunami-triggering, inflicted heavy loss and considerable economic damage to the region. From 1920 to present, three earthquakes with magnitudes of about 8.0 (Mw 8.2, 25 November 1941; Ms 8.0, 25 February 1969; and Mw 7.9, 26 May 1975) occurred in the oceanic region, and four earthquakes with magnitudes of about 7.0 (Mw 7.1, 8 May 1939, Santa Maria Island and Mw 7.1, January 1980, Terceira and Graciosa Islands, both in the Azores; Ms 7.1, 20 May 1931, Azores-Gibraltar fracture zone; and Mw 7.3, 10 October 1980, El Asnam, Algeria) occurred along the western part of the Eurasia-Nubia plate boundary. In general, large earthquakes (M ≥7) occur within the oceanic region, with the exception of the El Asnam (Algeria) earthquakes. Some of these events caused extensive damage. The 1755 Lisbon earthquake (˜Mw 9) on the Portugal Atlantic margin, about 200 km W-SW of Cape St. Vincent, was followed by a tsunami and fires that caused the near-total destruction of Lisbon and adjacent areas. Estimates of the death toll in Lisbon alone (~70

Evidence of displacement-driven maturation along the San Cristobal Trough transform plate boundary

Science.gov (United States)

Neely, James S.; Furlong, Kevin P.

2018-03-01

The San Cristobal Trough (SCT), formed by the tearing of the Australia plate as it subducts under the Pacific plate near the Solomon Islands, provides an opportunity to study the transform boundary development process. Recent seismicity (2013-2016) along the 280 km long SCT, known as a Subduction-Transform Edge Propagator (STEP) fault, highlights the tearing process and ongoing development of the plate boundary. The region's earthquakes reveal two key characteristics. First, earthquakes at the western terminus of the SCT, which we interpret to indicate the Australia plate tearing, display disparate fault geometries. These events demonstrate that plate tearing is accommodated via multiple intersecting planes rather than a single through-going fault. Second, the SCT hosts sequences of Mw ∼7 strike-slip earthquakes that migrate westward through a rapid succession of events. Sequences in 1993 and 2015 both began along the eastern SCT and propagated west, but neither progression ruptured into or nucleated a large earthquake within the region near the tear. Utilizing b-value and Coulomb Failure Stress analyses, we examine these along-strike variations in the SCT's seismicity. b-Values are highest along the youngest, western end of the SCT and decrease with increasing distance from the tear. This trend may reflect increasing strain localization with increasing displacement. Coulomb Failure Stress analyses indicate that the stress conditions were conducive to continued western propagation of the 1993 and 2015 sequences suggesting that the unruptured western SCT may have fault geometries or properties that inhibit continued rupture. Our results indicate a displacement-driven fault maturation process. The multi-plane Australia plate tearing likely creates a western SCT with diffuse strain accommodated along a network of disorganized faults. After ∼90 km of cumulative displacement (∼900,000 yr of plate motion), strain localizes and faults align, allowing the SCT to host

3-D thermo-mechanical laboratory modeling of plate-tectonics: modeling scheme, technique and first experiments

Directory of Open Access Journals (Sweden)

D. Boutelier

2011-05-01

Full Text Available We present an experimental apparatus for 3-D thermo-mechanical analogue modeling of plate tectonic processes such as oceanic and continental subductions, arc-continent or continental collisions. The model lithosphere, made of temperature-sensitive elasto-plastic analogue materials with strain softening, is submitted to a constant temperature gradient causing a strength reduction with depth in each layer. The surface temperature is imposed using infrared emitters, which allows maintaining an unobstructed view of the model surface and the use of a high resolution optical strain monitoring technique (Particle Imaging Velocimetry. Subduction experiments illustrate how the stress conditions on the interplate zone can be estimated using a force sensor attached to the back of the upper plate and adjusted via the density and strength of the subducting lithosphere or the lubrication of the plate boundary. The first experimental results reveal the potential of the experimental set-up to investigate the three-dimensional solid-mechanics interactions of lithospheric plates in multiple natural situations.

Effect of plate permeability on nonlinear stability of the asymptotic suction boundary layer.

Science.gov (United States)

Wedin, Håkan; Cherubini, Stefania; Bottaro, Alessandro

2015-07-01

The nonlinear stability of the asymptotic suction boundary layer is studied numerically, searching for finite-amplitude solutions that bifurcate from the laminar flow state. By changing the boundary conditions for disturbances at the plate from the classical no-slip condition to more physically sound ones, the stability characteristics of the flow may change radically, both for the linearized as well as the nonlinear problem. The wall boundary condition takes into account the permeability K̂ of the plate; for very low permeability, it is acceptable to impose the classical boundary condition (K̂=0). This leads to a Reynolds number of approximately Re(c)=54400 for the onset of linearly unstable waves, and close to Re(g)=3200 for the emergence of nonlinear solutions [F. A. Milinazzo and P. G. Saffman, J. Fluid Mech. 160, 281 (1985); J. H. M. Fransson, Ph.D. thesis, Royal Institute of Technology, KTH, Sweden, 2003]. However, for larger values of the plate's permeability, the lower limit for the existence of linear and nonlinear solutions shifts to significantly lower Reynolds numbers. For the largest permeability studied here, the limit values of the Reynolds numbers reduce down to Re(c)=796 and Re(g)=294. For all cases studied, the solutions bifurcate subcritically toward lower Re, and this leads to the conjecture that they may be involved in the very first stages of a transition scenario similar to the classical route of the Blasius boundary layer initiated by Tollmien-Schlichting (TS) waves. The stability of these nonlinear solutions is also investigated, showing a low-frequency main unstable mode whose growth rate decreases with increasing permeability and with the Reynolds number, following a power law Re(-ρ), where the value of ρ depends on the permeability coefficient K̂. The nonlinear dynamics of the flow in the vicinity of the computed finite-amplitude solutions is finally investigated by direct numerical simulations, providing a viable scenario for

How diking affects the longer-term structure and evolution of divergent plate boundaries

KAUST Repository

Trippanera, Daniele; Acocella, Valerio; Ruch, Joel; Rivalta, Eleonora

2015-01-01

Recurrent diking episodes along divergent plate boundaries, as at Dabbahu (2005, Afar) or at Bardarbunga (2014, Iceland) , highlight the possibility to have m-wide opening in a short time (days to weeks). This suggests a prominent role of magma

Generalized viscothermoelasticity theory of dual-phase-lagging model for damping analysis in circular micro-plate resonators

Science.gov (United States)

Grover, D.; Seth, R. K.

2018-05-01

Analysis and numerical results are presented for the thermoelastic dissipation of a homogeneous isotropic, thermally conducting, Kelvin-Voigt type circular micro-plate based on Kirchhoff's Love plate theory utilizing generalized viscothermoelasticity theory of dual-phase-lagging model. The analytical expressions for thermoelastic damping of vibration and frequency shift are obtained for generalized dual-phase-lagging model and coupled viscothermoelastic plates. The scaled thermoelastic damping has been illustrated in case of circular plate and axisymmetric circular plate for fixed aspect ratio for clamped and simply supported boundary conditions. It is observed that the damping of vibrations significantly depend on time delay and mechanical relaxation times in addition to thermo-mechanical coupling in circular plate under resonance conditions and plate dimensions.

Heat transfer enhancement in a turbulent natural convection boundary layer along a vertical flat plate

International Nuclear Information System (INIS)

Tsuji, Toshihiro; Kajitani, Tsuyoshi; Nishino, Tatsuhiko

2007-01-01

An experimental study on heat transfer enhancement for a turbulent natural convection boundary layer in air along a vertical flat plate has been performed by inserting a long flat plate in the spanwise direction (simple heat transfer promoter) and short flat plates aligned in the spanwise direction (split heat transfer promoter) with clearances into the near-wall region of the boundary layer. For a simple heat transfer promoter, the heat transfer coefficients increase by a peak value of approximately 37% in the downstream region of the promoter compared with those in the usual turbulent natural convection boundary layer. It is found from flow visualization and simultaneous measurements of the flow and thermal fields with hot- and cold-wires that such increase of heat transfer coefficients is mainly caused by the deflection of flows toward the outer region of the boundary layer and the invasion of low-temperature fluids from the outer region to the near-wall region with large-scale vortex motions riding out the promoter. However, heat transfer coefficients for a split heat transfer promoter exhibit an increase in peak value of approximately 60% in the downstream region of the promoter. Flow visualization and PIV measurements show that such remarkable heat transfer enhancement is attributed to longitudinal vortices generated by flows passing through the clearances of the promoter in addition to large-scale vortex motions riding out the promoter. Consequently, it is concluded that heat transfer enhancement of the turbulent natural convection boundary layer can be substantially achieved in a wide area of the turbulent natural convection boundary layer by employing multiple column split heat transfer promoters. It may be expected that the heat transfer enhancement in excess of approximately 40% can be accomplished by inserting such promoters

Identifying Fault Connections of the Southern Pacific-North American Plate Boundary Using Triggered Slip and Crustal Velocities

Science.gov (United States)

Donnellan, A.; Grant Ludwig, L.; Rundle, J. B.; Parker, J. W.; Granat, R.; Heflin, M. B.; Pierce, M. E.; Wang, J.; Gunson, M.; Lyzenga, G. A.

2017-12-01

The 2010 M7.2 El Mayor - Cucapah earthquake caused extensive triggering of slip on faults proximal to the Salton Trough in southern California. Triggered slip and postseismic motions that have continued for over five years following the earthquake highlight connections between the El Mayor - Cucapah rupture and the network of faults that branch out along the southern Pacific - North American Plate Boundary. Coseismic triggering follows a network of conjugate faults from the northern end of the rupture to the Coachella segment of the southernmost San Andreas fault. Larger aftershocks and postseismic motions favor connections to the San Jacinto and Elsinore faults further west. The 2012 Brawley Swarm can be considered part of the branching on the Imperial Valley or east side of the plate boundary. Cluster analysis of long-term GPS velocities using Lloyds Algorithm, identifies bifurcation of the Pacific - North American plate boundary; The San Jacinto fault joins with the southern San Andreas fault, and the Salton Trough and Coachella segment of the San Andreas fault join with the Eastern California Shear Zone. The clustering analysis does not identify throughgoing deformation connecting the Coachella segment of the San Andreas fault with the rest of the San Andreas fault system through the San Gorgonio Pass. This observation is consistent with triggered slip from both the 1992 Landers and 2010 El Mayor - Cucapah earthquakes that follows the plate boundary bifurcation and with paleoseismic evidence of smaller earthquakes in the San Gorgonio Pass.

Plate boundary deformation and man-made subsidence around geothermal fields on the Reykjanes Peninsula, Iceland

KAUST Repository

Keiding, Marie; Á rnadó ttir, Thó ra; Jonsson, Sigurjon; Decriem, Judicaë l; Hooper, Andrew John

2010-01-01

We present Interferometric Synthetic Aperture Radar (InSAR) data from 1992-1999 and 2003-2008 as well as GPS data from 2000-2009 for the active plate boundary on the Reykjanes Peninsula, southwest Iceland. The geodetic data reveal deformation mainly due to plate spreading, anthropogenic subsidence caused by geothermal fluid extraction and, possibly, increasing pressure in a geothermal system. Subsidence of around 10. cm is observed during the first 2. years of production at the Reykjanes geothermal power plant, which started operating in May 2006. We model the surface subsidence around the new power plant using point and ellipsoidal pressure sources in an elastic halfspace. Short-lived swarms of micro-earthquakes as well as aseismic fault movement are observed near the geothermal field following the start of production, possibly triggered by the stresses induced by geothermal fluid extraction. © 2010 Elsevier B.V.

Plate boundary deformation and man-made subsidence around geothermal fields on the Reykjanes Peninsula, Iceland

KAUST Repository

Keiding, Marie

2010-07-01

We present Interferometric Synthetic Aperture Radar (InSAR) data from 1992-1999 and 2003-2008 as well as GPS data from 2000-2009 for the active plate boundary on the Reykjanes Peninsula, southwest Iceland. The geodetic data reveal deformation mainly due to plate spreading, anthropogenic subsidence caused by geothermal fluid extraction and, possibly, increasing pressure in a geothermal system. Subsidence of around 10. cm is observed during the first 2. years of production at the Reykjanes geothermal power plant, which started operating in May 2006. We model the surface subsidence around the new power plant using point and ellipsoidal pressure sources in an elastic halfspace. Short-lived swarms of micro-earthquakes as well as aseismic fault movement are observed near the geothermal field following the start of production, possibly triggered by the stresses induced by geothermal fluid extraction. © 2010 Elsevier B.V.

Experiments of dike-induced deformation: Insights on the long-term evolution of divergent plate boundaries

KAUST Repository

Trippanera, D.

2015-10-22

The shallow transport of magma occurs through dikes causing surface deformation. Our understanding of the effects of diking at the surface is limited, especially on the long term, for repeated intrusive episodes. We use analogue models to study the upper crustal deformation induced by dikes. We insert metal plates within cohesive sand with three setups: in setup A, the intrusion rises upward with constant thickness and in setups B and C, the intrusion thickens at a fixed depth, with final rectangular (setup B) or triangular (setup C) shape in section. Setup A creates a doming delimited by reverse faults, with secondary apical graben, without close correspondence in nature. In setups B and C, a depression flanked by two uplifted areas is bordered by inward dipping normal faults propagating downward and, for deeper intrusions in setup B, also by inner faults, reverse at the surface; this deformation is similar to what is observed in nature, suggesting a consistent physical behavior. Dikes in nature initially propagate developing a mode I fracture at the tip, subsequently thickened by magma intrusion, without any host rock translation in the propagation direction (as in setup A). The deformation pattern in setups B and C depends on the intrusion depth and thickness, consistently to what is observed along divergent plate boundaries. The early deformation in setups B and C is similar to that from a single rifting episode (i.e., Lakagigar, Iceland, and Dabbahu, Afar), whereas the late stages resemble the structure of mature rifts (i.e., Krafla, Iceland), confirming diking as a major process in shaping divergent plate boundaries.

What drives microplate motion and deformation in the northeastern Caribbean plate boundary region?

NARCIS (Netherlands)

van Benthem, S.A.C.; Govers, R.; Wortel, R.

2014-01-01

The north Caribbean plate boundary zone is a broad deformation zone with several fault systems and tectonic blocks that move with different velocities. The indentation by the Bahamas Platform (the “Bahamas Collision”) is generally invoked as a cause of this fragmentation. We propose that a second

Discrete quintic spline for boundary value problem in plate deflation theory

Science.gov (United States)

Wong, Patricia J. Y.

2017-07-01

We propose a numerical scheme for a fourth-order boundary value problem arising from plate deflation theory. The scheme involves a discrete quintic spline, and it is of order 4 if a parameter takes a specific value, else it is of order 2. We also present a well known numerical example to illustrate the efficiency of our method as well as to compare with other numerical methods proposed in the literature.

Potential recovery for Reissner--Mindlin and Kirchhoff--Love plate models using global Carleman estimates

International Nuclear Information System (INIS)

Osses, Axel; Palacios, Benjamín

2013-01-01

In this paper, we consider two linear plate models, namely the Reissner–Mindlin system (R–M) and the Kirchhoff–Love equation (K–L), which come from linear elasticity. We prove global Carleman inequalities for both models with boundary observations and under a suitable hypothesis on the parameters. We use these estimates to study the inverse problem of recovering a spatially dependent potential from knowledge of Neumann boundary data. We obtain L 2 -Lipschitz stability for K–L and H 1 -Lipschitz stability for R–M under the assumption that the potentials are equal at the boundary. (paper)

Global crustal movement and tectonic plate boundary deformation constrained by the ITRF2008

Directory of Open Access Journals (Sweden)

Zhu Ze

2012-08-01

Full Text Available On the basis of the newly released International Terrestrial Reference Frame(ITRF2008 by the International Earth Rotation Service (IERS, a new global plate model ITRF2008 plate for the major plates is established. This ITRF2008-derived model is analyzed in comparison with NNR-NUVEL1A model, which is mainly based on geological and geophysical data. The Eurasia and Pacific plates display obvious differences in terms of the velocity fields derived from the two plate motion models. Plate acceleration is also introduced to characterize the differences of the two velocity fields which obtained from ITRF2008 -plate and NNR-NUVEL1A models for major individual plates. The results show that the Africa, South America and Eurasia plates are undergoing acceleration, while the North America and Australia plates are in the state of deceleration motion.

An analytical study of the free and forced vibration response of a ribbed plate with free boundary conditions

Science.gov (United States)

Lin, Tian Ran; Zhang, Kai

2018-05-01

An analytical study to predict the vibration response of a ribbed plate with free boundary conditions is presented. The analytical solution was derived using a double cosine integral transform technique and then utilized to study the free and forced vibration of the ribbed plate, as well as the effect of the rib on the modal response of the uniform plate. It is shown that in addition to the three zero-frequency rigid body modes of the plate, the vibration modes of the uniform plate can be classified into four mode groups according to the symmetric properties of the plate with respect to the two orthogonal middle lines parallel to the plate edges. The four mode groups correspond to a double symmetric group, a double anti-symmetric group and two symmetric/anti-symmetric groups. Whilst the inclusion of the rib to the plate is shown to cause distortion to the distribution of vibration modes, most modes can still be traced back to the original modes of the uniform plate. Both the mass and stiffness of the rib are shown to affect the modal vibration of the uniform plate, whereby a dominant effect from the rib mass leads to a decrease in the modal frequency of the plate, whereas a dominant effect from the rib stiffness leads to an increase in plate modal frequency. When the stiffened rib behaves as an effective boundary to the plate vibration, an original plate mode becomes a pair of degenerate modes, whereby one mode has a higher frequency and the other mode has a lower frequency than that of the original mode.

Numerical analysis of viscoelastic boundary layers : the case of plate withdrawal in a Maxwellian fluid

International Nuclear Information System (INIS)

Sadeghy, K.; Sharifi, M.

2002-01-01

The effect of a fluid's elasticity on the characteristics of its boundary layer was investigated in this work. A viscoelastic fluid of Maxwellian type was selected for this purpose and the flow induced in this fluid by a plate withdrawing at a constant velocity was studied. Conventional boundary layer assumptions were invoked to reduce the equations of motion to a simple form incorporating an elastic term in addition to the familiar inertial, viscous and pressure terms. It was shown that for elastic effects to be of an importance in a boundary layer, the fluid's relaxation time should be of an order much larger than its kinematic viscosity. By introducing a stream function, the governing equation was transformed into a nonlinear ODE with x-coordinate still appearing in the equation demonstrating that no similarity solution existed for this flow. The resulting equation was then solved numerically for Deborah numbers as large as 1.0. The results showed a marked formation of boundary layer adjacent to a moving wall for a Maxwellian fluid. The boundary layer thickness and the wall shear stress were found to scale with fluid's elasticity - both decreasing the higher the fluid's elasticity. It is thus anticipated that in free coating processes, the force required to impart a constant velocity to a withdrawing belt or plate would be lower if fluid's elasticity is significant. (author)

Structure and composition of the plate-boundary slip zone for the 2011 Tohoku-Oki earthquake.

Science.gov (United States)

Chester, Frederick M; Rowe, Christie; Ujiie, Kohtaro; Kirkpatrick, James; Regalla, Christine; Remitti, Francesca; Moore, J Casey; Toy, Virginia; Wolfson-Schwehr, Monica; Bose, Santanu; Kameda, Jun; Mori, James J; Brodsky, Emily E; Eguchi, Nobuhisa; Toczko, Sean

2013-12-06

The mechanics of great subduction earthquakes are influenced by the frictional properties, structure, and composition of the plate-boundary fault. We present observations of the structure and composition of the shallow source fault of the 2011 Tohoku-Oki earthquake and tsunami from boreholes drilled by the Integrated Ocean Drilling Program Expedition 343 and 343T. Logging-while-drilling and core-sample observations show a single major plate-boundary fault accommodated the large slip of the Tohoku-Oki earthquake rupture, as well as nearly all the cumulative interplate motion at the drill site. The localization of deformation onto a limited thickness (less than 5 meters) of pelagic clay is the defining characteristic of the shallow earthquake fault, suggesting that the pelagic clay may be a regionally important control on tsunamigenic earthquakes.

3-D Simulation of Tectonic Evolution in Mariana with a Coupled Model of Plate Subduction and Back-Arc Spreading

Science.gov (United States)

Hashima, A.; Matsu'Ura, M.

2006-12-01

We obtained the expressions for internal deformation fields due to a moment tensor in an elastic-viscoelastic layered holf-space. This unified formulation of internal deformation fields for shear faulting and crack opening enabled us to deal with the problem of tectonic deformation at a composite type of plate boundary zones. The tectonic deformation can be ascribed to mechanical interaction at plate boundaries, which make a closed circuit with the mode of relative plate motion changing from divergence to convergence through transcurrent motion. One of the rational ways to represent mechanical interaction at plate boundaries is specifying the increase rates of normal or tangential displacement discontinuity across plate interfaces. On the basis of such a basic idea we developed a 3-D simulation model for the nonlinear, coupled system of plate subduction and back-arc spreading in Mariana. Through numerical simulations we revealed the evolution process of back-arc spreading. At the first stage, steady plate subduction (shear faulting at a plate interface) gradually forms tensile stress fields in the back-arc region of the overriding plate. When the accumulated tensile stress reaches a critical level, back-arc spreading (crack opening) starts at a structurally weak portion of the overriding plate. The horizontal motion of the frontal part of the overriding plate due to back-arc spreading pushes out the plate boundary toward the oceanic plate. In steady-state plate subduction the shear stress acting on a plate interface must balance with the maximum frictional resistance (shear strength) of the plate interface. Therefore, the increase of shear stress at the plate interface leads to the increase of slip rate at the plate interface. The local increase of slip rate at the plate interface produces the additional tensile stress in the back-arc region. The increased tensile stress must be canceled out by the additional crack opening. Such a feedback mechanism between plate

Transition due to streamwise streaks in a supersonic flat plate boundary layer

Science.gov (United States)

Paredes, Pedro; Choudhari, Meelan M.; Li, Fei

2016-12-01

Transition induced by stationary streaks undergoing transient growth in a supersonic flat plate boundary layer flow is studied using numerical computations. While the possibility of strong transient growth of small-amplitude stationary perturbations in supersonic boundary layer flows has been demonstrated in previous works, its relation to laminar-turbulent transition cannot be established within the framework of linear disturbances. Therefore, this paper investigates the nonlinear evolution of initially linear optimal disturbances that evolve into finite amplitude streaks in the downstream region, and then studies the modal instability of those streaks as a likely cause for the onset of bypass transition. The nonmodal evolution of linearly optimal stationary perturbations in a supersonic, Mach 3 flat plate boundary layer is computed via the nonlinear plane-marching parabolized stability equations (PSE) for stationary perturbations, or equivalently, the perturbation form of parabolized Navier-Stokes equations. To assess the effect of the nonlinear finite-amplitude streaks on transition, the linear form of plane-marching PSE is used to investigate the instability of the boundary layer flow modified by the spanwise periodic streaks. The onset of transition is estimated using an N -factor criterion based on modal amplification of the secondary instabilities of the streaks. In the absence of transient growth disturbances, first mode instabilities in a Mach 3, zero pressure gradient boundary layer reach N =10 at Rex≈107 . However, secondary instability modes of the stationary streaks undergoing transient growth are able to achieve the same N -factor at Rex<2 ×106 when the initial streak amplitude is sufficiently large. In contrast to the streak instabilities in incompressible flows, subharmonic instability modes with twice the fundamental spanwise wavelength of the streaks are found to have higher amplification ratios than the streak instabilities at fundamental

Plane wave diffraction by a finite plate with impedance boundary conditions.

Science.gov (United States)

Nawaz, Rab; Ayub, Muhammad; Javaid, Akmal

2014-01-01

In this study we have examined a plane wave diffraction problem by a finite plate having different impedance boundaries. The Fourier transforms were used to reduce the governing problem into simultaneous Wiener-Hopf equations which are then solved using the standard Wiener-Hopf procedure. Afterwards the separated and interacted fields were developed asymptotically by using inverse Fourier transform and the modified stationary phase method. Detailed graphical analysis was also made for various physical parameters we were interested in.

A combined rigid/deformable plate tectonic model for the evolution of the Indian Ocean

Science.gov (United States)

Watson, J. G.; Glover, C. T.; Adriasola Munoz, A. C.; Harris, J. P.; Goodrich, M.

2012-04-01

Plate tectonic reconstructions are essential for placing geological information in its correct spatial context, understanding depositional environments, defining basin dimensions and evolution, and serve as a basis for palaeogeographic mapping and for palaeo-climate modelling. Traditional 'rigid' plate reconstructions often result in misfits (overlaps and underfits) in the geometries of juxtaposed plate margins when restored to their pre-rift positions. This has been attributed to internal deformation pre- and/or syn- continental break-up. Poorly defined continent-ocean boundaries add to these problems. To date, few studies have integrated continental extension within a global model. Recent plate tectonic reconstructions based on the relative motions of Africa, Madagascar, India and Antarctica during the break-up of eastern Gondwana have not taken into account the effects of deformation; particularly between India and Madagascar, and India and the Seychelles. A deformable plate model is in development that builds on the current rigid plate model to describe the complex multiphase break-up history between Africa, Madagascar, Seychelles and India, the associated magmatic activity and subsequent India/Eurasia collision. The break-up of eastern Gondwana occurred in the mid Jurassic by rifting between Africa and the India-Madagascar-Australian-Antarctica plates, followed by the Late Jurassic drift of India away from Australia and the Cretaceous break-up of Australia and Antarctica. The northwards drift of the Seychelles-India block in the Tertiary was accommodated by the opening of the Laxmi Basin. This was followed by the eruption of the extensive Deccan flood basalts and the separation of India and the Seychelles. Crustal domains on volcanic margins can be very difficult to define due to the accretion of magmatic material. On these margins, there is much speculation on the position of the continent-ocean boundary and the timing of rifting and sea-floor spreading. The

Plate boundary reorganization in the active Banda Arc-continent collision: Insights from new GPS measurements

Science.gov (United States)

Nugroho, Hendro; Harris, Ron; Lestariya, Amin W.; Maruf, Bilal

2009-12-01

New GPS measurements reveal that large sections of the SE Asian Plate are progressively accreting to the edge of the Australian continent by distribution of strain away from the deformation front to forearc and backarc plate boundary segments. The study was designed to investigate relative motions across suspected plate boundary segments in the transition from subduction to collision. The oblique nature of the collision provides a way to quantify the spatial and temporal distribution of strain from the deformation front to the back arc. The 12 sites we measured from Bali to Timor included some from an earlier study and 7 additional stations, which extended the epoch of observation to ten years at many sites. The resulting GPS velocity field delineates at least three Sunda Arc-forearc regions around 500 km in strike-length that shows different amounts of coupling to the Australian Plate. Movement of these regions relative to SE Asia increases from 21% to 41% to 63% eastward toward the most advanced stages of collision. The regions are bounded by the deformation front to the south, the Flores-Wetar backarc thrust system to the north, and poorly defined structures on the sides. The suture zone between the NW Australian continental margin and the Sunda-Banda Arcs is still evolving with more than 20 mm/yr of movement measured across the Timor Trough deformation front between Timor and Australia.

Plane wave diffraction by a finite plate with impedance boundary conditions.

Directory of Open Access Journals (Sweden)

Rab Nawaz

Full Text Available In this study we have examined a plane wave diffraction problem by a finite plate having different impedance boundaries. The Fourier transforms were used to reduce the governing problem into simultaneous Wiener-Hopf equations which are then solved using the standard Wiener-Hopf procedure. Afterwards the separated and interacted fields were developed asymptotically by using inverse Fourier transform and the modified stationary phase method. Detailed graphical analysis was also made for various physical parameters we were interested in.

Upper-Mantel Earthquakes in the Australia-Pacific Plate Boundary Zone and the Roots of the Alpine Fault

Science.gov (United States)

Boese, C. M.; Warren-Smith, E.; Townend, J.; Stern, T. A.; Lamb, S. H.

2016-12-01

Seismicity in the upper mantle in continental collision zones is relatively rare, but observed around the world. Temporary seismometer deployments have repeatedly detected mantle earthquakes at depths of 40-100 km within the Australia-Pacific plate boundary zone beneath the South Island of New Zealand. Here, the transpressive Alpine Fault constitutes the primary plate boundary structure linking subduction zones of opposite polarity farther north and south. The Southern Alps Microearthquake Borehole Array (SAMBA) has been operating continuously since November 2008 along a 50 km-long section of the central Alpine Fault, where the rate of uplift of the Southern Alps is highest. To date it has detected more than 40 small to moderate-sized mantle events (1≤ML≤3.9). The Central Otago Seismic Array (COSA) has been in operation since late 2012 and detected 15 upper mantle events along the sub-vertical southern Alpine Fault. Various mechanisms have been proposed to explain the occurrence of upper mantle seismicity in the South Island, including intra-continental subduction (Reyners 1987, Geology); high shear-strain gradients due to depressed geotherms and viscous deformation of mantle lithosphere (Kohler and Eberhart-Phillips 2003, BSSA); high strain rates resulting from plate bending (Boese et al. 2013, EPSL), and underthrusting of the Australian plate (Lamb et al. 2015, G3). Focal mechanism analysis reveals a variety of mechanisms for the upper mantle events but predominantly strike-slip and reverse faulting. In this study, we apply spectral analysis to better constrain source parameters for these mantle events. These results are interpreted in conjunction with new information about crustal structure and low-frequency earthquakes near the Moho and in light of existing velocity, attenuation and resistivity models.

Effects of freestream on the characteristics of thermally-driven boundary layers along a heated vertical flat plate

International Nuclear Information System (INIS)

Abedin, Mohammad Zoynal; Tsuji, Toshihiro; Lee, Jinho

2012-01-01

Highlights: ► A time-developing direct numerical simulations are done for water along a heated vertical plate. ► The objective is to see the effects of free streams on the combined-convection boundary layers. ► There are no reports for water with direct numerical simulation in this regards. ► An experiment is also conducted on the transitional and turbulent boundary layer in water. ► This is to collect informations on the integral thickness of the velocity boundary layer. - Abstract: Time-developing thermally-driven boundary layers created by imposing aiding and opposing freestreams on the natural-convection boundary layer in water along a heated vertical flat plate have been examined with a direct numerical simulation to clarify their transition and turbulence behaviors. The numerical results for aiding flow reveal that the transition begins at a thick laminar boundary layer due to the delay of the transition and large-scale vortexes centering on the spanwise direction are followed, while, for opposing flow, the transition begins at a thin laminar boundary layer due to the quickening of the transition and relatively small-scale vortexes are generated with the progress of transition. To improve the significance of the present numerical results, the association of turbulence statistics between time- and space-developing flows has been investigated. Consequently, the numerical results for time-developing flow are converted to those for space-developing flow through the integral thickness of the velocity boundary layer for pure natural convection, and thus the regimes of boundary layer flows can be quantitatively assessed. Moreover, the turbulence statistics and the flow structures in the thermally-driven boundary layers are also presented.

Experiments of dike-induced deformation: Insights on the long-term evolution of divergent plate boundaries

KAUST Repository

Trippanera, D.; Ruch, Joel; Acocella, V.; Rivalta, E.

2015-01-01

on the intrusion depth and thickness, consistently to what is observed along divergent plate boundaries. The early deformation in setups B and C is similar to that from a single rifting episode (i.e., Lakagigar, Iceland, and Dabbahu, Afar), whereas the late stages

Development of the Plate Boundary Observatory GPS Low Latency Salton Trough Radio Network

Science.gov (United States)

Walls, C.; Miller, S.; Wilson, B.; Lawrence, S.; Arnitz, E.

2008-05-01

UNAVCO is developing a 20 GPS station low latency radio network that spans the San Andreas and San Jacinto faults in the region of highest strain in southern California and the narrowest part of the North America-Pacific plate boundary. The Salton Trough Radio Network (STRN) is instrumented with Ethernet bridge Intuicom EB6+ (900 MHz) radios to transmit a high rate low latency data stream from each permanent GPS site for the purpose of the following: 1) telemeter 15 second data (1 MB/day/station) to the Plate Boundary Observatory archive, 2) accommodate the timely download of 1 and 5 sample per second data following large earthquakes (4 MB/hour/station), and 3) test the UStream of 1Hz BINEX and RTCM data. Three of four phases have been completed. Office radio testing yielded transfer rates of 30-50 KB/s with subsecond latency while streaming 1 Hz data. Latency climbed to ~1.8 seconds while simultaneously streaming 1 Hz and downloading hourly 1 and 5 sample per second data files. Field testing demonstrated rates on the order of 30 KB/s. At present the radios are installed and have transfer rates of 10-40 KB/s between sites that span 10-32 km. The final phase will be the installation of the main telemetry relay where master radios will be connected to a high speed ISP near the town of Brawley. The high-rate low latency UStream data will be available to researchers who are developing prototype earthquake early warning systems in Southern California. A goal of the STRN is to make the data available rapidly enough for GPS-derived coseismic and dynamic displacements to be integrated into early warning system earthquake models. The improved earthquake models will better assist emergency response. UStream data will also aid surveyors who wish to use PBO GPS stations as permanent, high-quality base stations in real-time kinematic surveys.

Examples of the Re-number effect on the transitional flat plate boundary layers

Czech Academy of Sciences Publication Activity Database

Antoš, Pavel; Jonáš, Pavel; Procházka, Pavel P.; Uruba, Václav

2014-01-01

Roč. 14, č. 1 (2014), s. 605-606 ISSN 1617-7061. [Annual Meeting of the International Association of Applied Mathematics and Mechanics /85./. Erlangen, 10.03.2014-14.03.2014] R&D Projects: GA ČR GAP101/12/1271 Institutional support: RVO:61388998 Keywords : transition * flat plate * boundary layer Subject RIV: BK - Fluid Dynamics http://dx.doi.org/10.1002/pamm.201410290

Seafloor spreading on the Southeast Indian Ridge over the last one million years: a test of the Capricorn plate hypothesis

Science.gov (United States)

Conder, James A.; Forsyth, Donald W.

2001-05-01

Plate motions in the Indian Ocean are inconsistent with a rigid Indo-Australian plate. An equatorial, diffuse boundary dividing the plate into separate Indian and Australian plates significantly improves the fit of kinematic plate models to the spreading rates, transform azimuths, and earthquake slip vectors on the spreading center boundaries. An additional boundary, further dividing the Australian plate into Australian and Capricorn plates has been proposed to account for much of the remaining inconsistency and the pattern of intraplate earthquakes [J.-Y. Royer, R.G. Gordon, Science 277 (1997) 1268-1274]. The proposed boundary is ˜2000 km wide where it intersects the Southeast Indian Ridge. Several recent geophysical cruises to the Southeast Indian Ridge, including a cruise within the proposed boundary, provide many new data for investigating the validity of the Capricorn plate model. These new observations strongly support the hypothesis that the Capricorn plate exists. Statistical tests of the data from the Southeast Indian Ridge alone are not sufficient to confirm it, but motion about the Rodriguez Triple Junction (RTJ) suggests some non-rigidity in the Antarctica-Australia-Somalia circuit. Inferred deformation with enforced closure about the RTJ leads to an estimate of plate motion consistent with the Capricorn plate model. However, the diffuse Capricorn-Australia boundary does not extend south of the St. Paul Fracture Zone, 800 km narrower than the previously proposed boundary.

Modelling of boundary plasma in TOKES

International Nuclear Information System (INIS)

Igitkhanov, Yu.; Pestchanyi, S.; Landman, I.

2009-12-01

. The model based on power scaling for L to H transition and includes the mitigation of turbulence at the edge once the flowing power exceeds the H-mode onset threshold. - The model of the Edge Localized Mode oscillation based on ballooning mode instability is implemented into code. - The boundary conditions for fluid equations at the divertor plates and at the main chamber wall are formulated and implemented into the integrated code. - Analyses of available experiments and benchmarking with simple analytical solutions in respect to SOL transport phenomena have been provided. Application for ITER is described. (orig.)

Lithospheric strength in the active boundary between the Pacific Plate and Baja California microplate constrained from lower crustal and upper mantle xenoliths

Science.gov (United States)

Chatzaras, Vasileios; van der Werf, Thomas; Kriegsman, Leo M.; Kronenberg, Andreas; Tikoff, Basil; Drury, Martyn R.

2017-04-01

The lower crust is the most poorly understood of the lithospheric layers in terms of its rheology, particularly at active plate boundaries. We studied naturally deformed lower crustal xenoliths within an active plate boundary, in order to link their microstructures and rheological parameters to the well-defined active tectonic context. The Baja California shear zone (BCSZ), located at the western boundary of the Baja California microplate, comprises the active boundary accommodating the relative motion between the Pacific plate and Baja California microplate. The basalts of the Holocene San Quintin volcanic field carry lower crustal and upper mantle xenoliths, which sample the Baja California microplate lithosphere in the vicinity of the BCSZ. The lower crustal xenoliths range from undeformed gabbros to granoblastic two-pyroxene granulites. Two-pyroxene geothermometry shows that the granulites equilibrated at temperatures of 690-920 oC. Phase equilibria (P-T pseudosections using Perple_X) indicate that symplectites with intergrown pyroxenes, plagioclase, olivine and spinel formed at 3.6-5.4 kbar, following decompression from pressures exceeding 6 kbar. FTIR spectroscopy shows that the water content of plagioclase varies among the analyzed xenoliths; plagioclase is relatively dry in two xenoliths while one xenolith contains hydrated plagioclase grains. Microstructural observations and analysis of the crystallographic texture provide evidence for deformation of plagioclase by a combination of dislocation creep and grain boundary sliding. To constrain the strength of the lower crust and upper mantle near the BCSZ we estimated the differential stress using plagioclase and olivine grain size paleopiezomtery, respectively. Differential stress estimates for plagioclase range from 10 to 32 MPa and for olivine are 30 MPa. Thus the active microplate boundary records elevated crustal temperatures, heterogeneous levels of hydration, and low strength in both the lower crust and

Streamwise counter-rotating vortices generated by triangular leading edge pattern in flat plate boundary layer

KAUST Repository

Hasheminejad, S. M.

2016-01-05

A series of flow visualizations were conducted to qualitatively study the development of streamwise counter-rotating vortices over a flat plate induced by triangular patterns at the leading edge of a flat plate. The experiments were carried out for a Reynolds number based on the pattern wavelength (λ) of 3080. The results depict the onset, development and breakdown of the vortical structures within the flat plate boundary layer. Moreover, the effect of one spanwise array of holes with diameter of 0.2λ (=3 mm) was examined. This investigation was done on two different flat plates with holes placed at the location x/λ = 2 downstream of the troughs and peaks. The presence of holes after troughs does not show any significant effect on the vortical structures. However, the plate with holes after peaks noticeably delays the vortex breakdown. In this case, the “mushroom-like” vortices move away from the wall and propagate downstream with stable vortical structures. The vortex growth is halted further downstream but start to tilt aside.

Plate boundary deformation in North Iceland during 1992–2009 revealed by InSAR time-series analysis and GPS

KAUST Repository

Metzger, Sabrina

2014-08-20

In North Iceland, extensional plate motion is accommodated by the Northern Volcanic Zone, a set of en-echelon volcanic systems, and the Tjörnes Fracture Zone, a transform offset in the mid-Atlantic Ridge consisting of two parallel transform lineaments. The southern lineament, the Húsavík–Flatey fault, is a 100 km-long right-lateral strike slip fault that has not ruptured for more than 140 years and poses a significant seismic hazard to Húsavík, a fishing town located by the fault, and to other coastal communities. We present results of InSAR time-series analysis data spanning almost two decades (1992–2009) that show extensional and interseismic deformation within the Northern Volcanic Zone and the on-shore part of the Tjörnes Fracture Zone. The results also exhibit transient inflation at Theistareykir volcano, deflation at Krafla central volcano and a broad uplift north of Krafla. The current plate extension is not uniform across the Northern Volcanic Zone, but concentrated at the western fissures of the Theistareykir volcanic system and the outermost fissures of the Krafla fissure swarm. We combine a back-slip plate boundary model with a set of point pressure sources representing volcanic changes to describe the current extensional plate boundary deformation and update the previous estimations of the locking depth and slip rate of the Húsavík–Flatey fault that were based on GPS data alone. Using different combinations of input data, we find that the Húsavík–Flatey fault has a locking depth of 6–10 km and, with a slip rate of 6–9 mm/yr, is accommodating about a third of the full transform motion. We furthermore show that while the InSAR data provide important constraints on the volcanic deformation within the NVZ, they do not significantly improve the model parameter estimation for the HFF, as the dense GPS network appears to better capture the deformation across the fault.

Plate boundary deformation in North Iceland during 1992–2009 revealed by InSAR time-series analysis and GPS

KAUST Repository

Metzger, Sabrina; Jonsson, Sigurjon

2014-01-01

In North Iceland, extensional plate motion is accommodated by the Northern Volcanic Zone, a set of en-echelon volcanic systems, and the Tjörnes Fracture Zone, a transform offset in the mid-Atlantic Ridge consisting of two parallel transform lineaments. The southern lineament, the Húsavík–Flatey fault, is a 100 km-long right-lateral strike slip fault that has not ruptured for more than 140 years and poses a significant seismic hazard to Húsavík, a fishing town located by the fault, and to other coastal communities. We present results of InSAR time-series analysis data spanning almost two decades (1992–2009) that show extensional and interseismic deformation within the Northern Volcanic Zone and the on-shore part of the Tjörnes Fracture Zone. The results also exhibit transient inflation at Theistareykir volcano, deflation at Krafla central volcano and a broad uplift north of Krafla. The current plate extension is not uniform across the Northern Volcanic Zone, but concentrated at the western fissures of the Theistareykir volcanic system and the outermost fissures of the Krafla fissure swarm. We combine a back-slip plate boundary model with a set of point pressure sources representing volcanic changes to describe the current extensional plate boundary deformation and update the previous estimations of the locking depth and slip rate of the Húsavík–Flatey fault that were based on GPS data alone. Using different combinations of input data, we find that the Húsavík–Flatey fault has a locking depth of 6–10 km and, with a slip rate of 6–9 mm/yr, is accommodating about a third of the full transform motion. We furthermore show that while the InSAR data provide important constraints on the volcanic deformation within the NVZ, they do not significantly improve the model parameter estimation for the HFF, as the dense GPS network appears to better capture the deformation across the fault.

An eddy-viscosity treatment of the unsteady turbulent boundary layer on a flat plate in an expansion tube

Science.gov (United States)

Gupta, R. N.; Trimpi, R. L.

1974-01-01

An analysis is presented for the relaxation of a turbulent boundary layer on a semiinfinite flat plate after passage of a shock wave and a trailing driver gas-driven gas interface. The problem has special application to expansion tube flows. The flow-governing equations have been transformed into the Lamcrocco variables. The numerical results indicate that a fully turbulent boundary layer relaxes faster to the final steady-state values of heat transfer and skin-friction than a fully laminar boundary layer.

Development of Streamwise Counter-Rotating Vortices in Flat Plate Boundary Layer Pre-set by Leading Edge Patterns

KAUST Repository

Hasheminejad, S.M.; Mitsudharmadi, Hatsari; Winoto, S.H.; Low, H.T.; Lua, K.B.

2017-01-01

Development of streamwise counter-rotating vortices induced by leading edge patterns with different pattern shape is investigated using hot-wire anemometry in the boundary layer of a flat plate. A triangular, sinusoidal and notched patterns

Net Rotation of the Lithosphere in Mantle Convection Models with Self-consistent Plate Generation

Science.gov (United States)

Gerault, M.; Coltice, N.

2017-12-01

Lateral variations in the viscosity structure of the lithosphere and the mantle give rise to a discordant motion between the two. In a deep mantle reference frame, this motion is called the net rotation of the lithosphere. Plate motion reconstructions, mantle flow computations, and inferences from seismic anisotropy all indicate some amount of net rotation using different mantle reference frames. While the direction of rotation is somewhat consistent across studies, the predicted amplitudes range from 0.1 deg/Myr to 0.3 deg/Myr at the present-day. How net rotation rates could have differed in the past is also a subject of debate and strong geodynamic arguments are missing from the discussion. This study provides the first net rotation calculations in 3-D spherical mantle convection models with self-consistent plate generation. We run the computations for billions of years of numerical integration. We look into how sensitive the net rotation is to major tectonic events, such as subduction initiation, continental breakup and plate reorganisations, and whether some governing principles from the models could guide plate motion reconstructions. The mantle convection problem is solved with the finite volume code StagYY using a visco-pseudo-plastic rheology. Mantle flow velocities are solely driven by buoyancy forces internal to the system, with free slip upper and lower boundary conditions. We investigate how the yield stress, the mantle viscosity structure and the properties of continents affect the net rotation over time. Models with large lateral viscosity variations from continents predict net rotations that are at least threefold faster than those without continents. Models where continents cover a third of the surface produce net rotation rates that vary from nearly zero to over 0.3 deg/Myr with rapide increase during continental breakup. The pole of rotation appears to migrate along no particular path. For all models, regardless of the yield stress and the

A folded plate clamped along one side only

Science.gov (United States)

Nazarov, Serguei A.; Slutskij, Andrey S.

2017-12-01

An asymptotic model of a folded thin elastic plate is posed on two plane domains and contains transmission conditions at the common line segment of their boundaries. These conditions become non-local and inhomogeneous if only one side of the plate is fixed. Solvability and smoothness results and error estimates for the model are derived. xml:lang="fr"

Boundary-layer transition prediction using a simplified correlation-based model

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Xia Chenchao

2016-02-01

Full Text Available This paper describes a simplified transition model based on the recently developed correlation-based γ-Reθt transition model. The transport equation of transition momentum thickness Reynolds number is eliminated for simplicity, and new transition length function and critical Reynolds number correlation are proposed. The new model is implemented into an in-house computational fluid dynamics (CFD code and validated for low and high-speed flow cases, including the zero pressure flat plate, airfoils, hypersonic flat plate and double wedge. Comparisons between the simulation results and experimental data show that the boundary-layer transition phenomena can be reasonably illustrated by the new model, which gives rise to significant improvements over the fully laminar and fully turbulent results. Moreover, the new model has comparable features of accuracy and applicability when compared with the original γ-Reθt model. In the meantime, the newly proposed model takes only one transport equation of intermittency factor and requires fewer correlations, which simplifies the original model greatly. Further studies, especially on separation-induced transition flows, are required for the improvement of the new model.

Numerical investigation of a spatially developing turbulent natural convection boundary layer along a vertical heated plate

International Nuclear Information System (INIS)

Nakao, Keisuke; Hattori, Yasuo; Suto, Hitoshi

2017-01-01

Highlights: • A large-eddy simulation of a spatially developing natural convection boundary layer is conducted. • First- and second-order moments of the heat and momentum showed a reasonable agreement with past experiments. • Coherent structure of turbulent vortex inherent in this boundary layer is discussed. - Abstract: Large-eddy simulation (LES) on a spatially developing natural convection boundary layer along a vertical heated plate was conducted. The heat transfer rate, friction velocity, mean velocity and temperature, and second-order turbulent properties both in the wall-normal and the stream-wise direction showed reasonable agreement with the findings of past experiments. The spectrum of velocity and temperature fluctuation showed a -2/3-power decay slope and -2-power decay slope respectively. Quadrant analysis revealed the inclination on Q1 and Q3 in the Reynolds stress and turbulent heat flux, changing their contribution along the distance from the plate surface. Following the convention, we defined the threshold region where the stream-wise mean velocity takes local maximum, the inner layer which is closer to the plate than the threshold region, the outer layer which is farther to the plate than the threshold region. The space correlation of stream-wise velocity tilted the head toward the wall in the propagating direction in the outer layer; on the other hand, the correlated motion had little inclination in the threshold region. The time history of the second invariant of gradient tensor Q revealed that the vortex strength oscillates both in the inner and the outer layers in between the laminar and the transition region. In the turbulent region, the vortex was often dominant in the outer layer. Instantaneous three-dimensional visualization of Q revealed the existence of high-speed fluid parcels associated with arch-shape vortices. These results were considered as an intrinsic structure in the outer layer, which is symmetrical to the structure of

Direct simulation of flat-plate boundary layer with mild free-stream turbulence

Science.gov (United States)

Wu, Xiaohua; Moin, Parviz

2014-11-01

Spatially evolving direct numerical simulation of the flat-plate boundary layer has been performed. The momentum thickness Reynolds number develops from 80 to 3000 with a free-stream turbulence intensity decaying from 3 percent to 0.8 percent. Predicted skin-friction is in agreement with the Blasius solution prior to breakdown, follows the well-known T3A bypass transition data during transition, and agrees with the Erm and Joubert Melbourne wind-tunnel data after the completion of transition. We introduce the concept of bypass transition in the narrow sense. Streaks, although present, do not appear to be dynamically important during the present bypass transition as they occur downstream of infant turbulent spots. For the turbulent boundary layer, viscous scaling collapses the rate of dissipation profiles in the logarithmic region at different Reynolds numbers. The ratio of Taylor microscale and the Kolmogorov length scale is nearly constant over a large portion of the outer layer. The ratio of large-eddy characteristic length and the boundary layer thickness scales very well with Reynolds number. The turbulent boundary layer is also statistically analyzed using frequency spectra, conditional-sampling, and two-point correlations. Near momentum thickness Reynolds number of 2900, three layers of coherent vortices are observed: the upper and lower layers are distinct hairpin forests of large and small sizes respectively; the middle layer consists of mostly fragmented hairpin elements.

A preliminary investigation of boundary-layer transition along a flat plate with adverse pressure gradient

Science.gov (United States)

Von Doenhoff, Albert E

1938-01-01

Boundary-layer surveys were made throughout the transition region along a smooth flat plate placed in an airstream of practically zero turbulence and with an adverse pressure gradient. The boundary-layer Reynolds number at the laminar separation point was varied from 1,800 to 2,600. The test data, when considered in the light of certain theoretical deductions, indicated that transition probably began with separation of the laminar boundary layer. The extent of the transition region, defined as the distance from a calculated laminar separation point to the position of the first fully developed turbulent boundary-layer profile, could be expressed as a constant Reynolds number run of approximately 70,000. Some speculations are presented concerning the application of the foregoing concepts, after certain assumptions have been made, to the problem of the connection between transition on the upper surface of an airfoil at high angles of attack and the maximum lift.

Prediction of an internal boundary layer on a flat plate after a step change in roughness using a near-wall RANS model

Science.gov (United States)

Chu, Minghan; Meng, Fanxiao; Bergstrom, Donald J.

2017-11-01

An in-house computational fluid dynamics code was used to simulate turbulent flow over a flat plate with a step change in roughness, exhibiting a smooth-rough-smooth configuration. An internal boundary layer (IBL) is formed at the transition from the smooth to rough (SR) and then the rough to smooth (RS) surfaces. For an IBL the flow far above the surface has experienced a wall shear stress that is different from the local value. Within a Reynolds-Averaged-Navier-Stokes (RANS) formulation, the two-layer k- ɛ model of Durbin et al. (2001) was implemented to analyze the response of the flow to the change in surface condition. The numerical results are compared to experimental data, including some in-house measurements and the seminal work of Antonia and Luxton (1971,72). This problem captures some aspects of roughness in industrial and environmental applications, such as corrosion and the earth's surface heterogeneity, where the roughness is often encountered as discrete distributions. It illustrates the challenge of incorporating roughness models in RANS that are capable of responding to complex surface roughness profiles.

Model to Analyze Micro Circular Plate Subjected to Electrostatic Force

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Cao Tian-Jie

2013-06-01

Full Text Available In this paper a distributed model with three possible static modes was presented to investigate the behavior of the plate subjected to electrostatic force and uniform hydrostatic pressure both before pull in and beyond pull in. The differential governing equation of the micro circular plate specifically used for numerical solution of the three modes, in which the singularity at the center of the micro plate did not occur, was presented based on the classical thin plate theory, Taylor's series expansion and Saint-Venant's principle. The numerical solution to the differential governing equation for the different mode was mainly attributed to solve for one unknown boundary condition and the applied voltage, which could be obtained by using a two-fold method of bisection based on the shooting method. The voltage ranges over which the three modes could exist and the points where transitions occurred between the modes were computed. Incorporating the above numerical solution to the applied voltage at the normal mode with some constrained optimization method, pull-in voltage and the corresponding pull-in position can automatically be obtained. In examples, the entire mechanical behavior of the circular plate over the operational voltage ranges was investigated and the effects of different parameters on pull-in voltage were studied. The obtained results were compared with the existing results and good agreement has been achieved.

Coupled effects of director orientations and boundary conditions on light induced bending of monodomain nematic liquid crystalline polymer plates

International Nuclear Information System (INIS)

You, Yue; Ding, Shurong; Huo, Yongzhong; Xu, Changwei

2012-01-01

A photo-chromic liquid crystal polymers (LCPs) is a smart material for large light-activated variation or bending to transfer luminous energy into mechanical energy. We study the light induced behavior by modeling planar and homeotropic nematic network polymer plates. We effectively illustrate some reported experimental outcomes and theoretically predict some possible bending patterns. This paper constructs an understanding between the bending behaviors and interactions among the alignments, aspect ratios and boundary conditions, etc. Our work provides information on optimizing light induced bending in the process of micro-opto-mechanical system (MOMS) design. (paper)

Earthquake recurrence and magnitude and seismic deformation of the northwestern Okhotsk plate, northeast Russia

Science.gov (United States)

Hindle, D.; Mackey, K.

2011-02-01

Recorded seismicity from the northwestern Okhotsk plate, northeast Asia, is currently insufficient to account for the predicted slip rates along its boundaries due to plate tectonics. However, the magnitude-frequency relationship for earthquakes from the region suggests that larger earthquakes are possible in the future and that events of ˜Mw 7.5 which should occur every ˜100-350 years would account for almost all the slip of the plate along its boundaries due to Eurasia-North America convergence. We use models for seismic slip distribution along the bounding faults of Okhotsk to conclude that relatively little aseismic strain release is occurring and that larger future earthquakes are likely in the region. Our models broadly support the idea of a single Okhotsk plate, with the large majority of tectonic strain released along its boundaries.

Global Dynamic Numerical Simulations of Plate Tectonic Reorganizations

Science.gov (United States)

Morra, G.; Quevedo, L.; Butterworth, N.; Matthews, K. J.; Müller, D.

2010-12-01

We use a new numerical approach for global geodynamics to investigate the origin of present global plate motion and to identify the causes of the last two global tectonic reorganizations occurred about 50 and 100 million years ago (Ma) [1]. While the 50 Ma event is the most well-known global plate-mantle event, expressed by the bend in the Hawaiian-Emperor volcanic chain, a prominent plate reorganization at about 100 Ma, although presently little studied, is clearly indicated by a major bend in the fracture zones in the Indian Ocean and by a change in Pacific plate motion [2]. Our workflow involves turning plate reconstructions into surface meshes that are subsequently employed as initial conditions for global Boundary Element numerical models. The tectonic setting that anticipates the reorganizations is processed with the software GPlates, combining the 3D mesh of the paleo-plate morphology and the reconstruction of paleo-subducted slabs, elaborated from tectonic history [3]. All our models involve the entire planetary system, are fully dynamic, have free surface, are characterized by a spectacular computational speed due to the simultaneous use of the multi-pole algorithm and the Boundary Element formulation and are limited only by the use of sharp material property variations [4]. We employ this new tool to unravel the causes of plate tectonic reorganizations, producing and comparing global plate motion with the reconstructed ones. References: [1] Torsvik, T., Müller, R.D., Van der Voo, R., Steinberger, B., and Gaina, C., 2008, Global Plate Motion Frames: Toward a unified model: Reviews in Geophysics, VOL. 46, RG3004, 44 PP., 2008 [2] Wessel, P. and Kroenke, L.W. Pacific absolute plate motion since 145 Ma: An assessment of the fixed hot spot hypothesis. Journal of Geophysical Research, Vol 113, B06101, 2008 [3] L. Quevedo, G. Morra, R. D. Mueller. Parallel Fast Multipole Boundary Element Method for Crustal Dynamics, Proceeding 9th World Congress and 4th Asian

Isostatic models and isostatic gravity anomalies of the Arabian plate and surroundings

Science.gov (United States)

Kaban, Mikhail K.; El Khrepy, Sami; Al-Arifi, Nassir

2015-04-01

Isostaic anomalies represent one of the most useful "geological" reduction of the gravity field. With the isostatic correction it is possible to remove a significant part of the effect of deep density heterogeneity, which dominates in the Bouguer gravity anomalies. This correction is based on the fact that a major part of the near-surface load is compensated by variations of the lithosphere boundaries (chiefly the Moho and LAB) and by density variations within the crust and upper mantle. It is usually supposed that it is less important to a first order, what is the actual compensation model when reducing the effect of compensating masses, since their total weight is exactly opposite to the near-surface load. We compare several compensating models for the Arabian plate and surrounding area. The Airy model gives very significant regional isostatic anomalies, which can not be explained by the upper crust structure or disturbances of the isostatic equilibrium. Also the predicted "isostatic" Moho is very different from the existing observations. The second group of the isostatic models includes the Moho, which is based on existing seismic determinations. Additional compensation is provided by density variations within the lithosphere (chiefly in the upper mantle). In this way we minimize regional anomalies over the Arabian plate. The residual local anomalies well correspond to tectonic structure of the plate. Still very significant anomalies are associated with the Zagros fold belt, the collision zone of the Arabian and Eurasian plates.

Does permanent extensional deformation in lower forearc slopes indicate shallow plate-boundary rupture?

Science.gov (United States)

Geersen, J.; Ranero, C. R.; Kopp, H.; Behrmann, J. H.; Lange, D.; Klaucke, I.; Barrientos, S.; Diaz-Naveas, J.; Barckhausen, U.; Reichert, C.

2018-05-01

Seismic rupture of the shallow plate-boundary can result in large tsunamis with tragic socio-economic consequences, as exemplified by the 2011 Tohoku-Oki earthquake. To better understand the processes involved in shallow earthquake rupture in seismic gaps (where megathrust earthquakes are expected), and investigate the tsunami hazard, it is important to assess whether the region experienced shallow earthquake rupture in the past. However, there are currently no established methods to elucidate whether a margin segment has repeatedly experienced shallow earthquake rupture, with the exception of mechanical studies on subducted fault-rocks. Here we combine new swath bathymetric data, unpublished seismic reflection images, and inter-seismic seismicity to evaluate if the pattern of permanent deformation in the marine forearc of the Northern Chile seismic gap allows inferences on past earthquake behavior. While the tectonic configuration of the middle and upper slope remains similar over hundreds of kilometers along the North Chilean margin, we document permanent extensional deformation of the lower slope localized to the region 20.8°S-22°S. Critical taper analyses, the comparison of permanent deformation to inter-seismic seismicity and plate-coupling models, as well as recent observations from other subduction-zones, including the area that ruptured during the 2011 Tohoku-Oki earthquake, suggest that the normal faults at the lower slope may have resulted from shallow, possibly near-trench breaking earthquake ruptures in the past. In the adjacent margin segments, the 1995 Antofagasta, 2007 Tocopilla, and 2014 Iquique earthquakes were limited to the middle and upper-slope and the terrestrial forearc, and so are upper-plate normal faults. Our findings suggest a seismo-tectonic segmentation of the North Chilean margin that seems to be stable over multiple earthquake cycles. If our interpretations are correct, they indicate a high tsunami hazard posed by the yet un

Effects of Thermal Radiation and Chemical Reaction on MHD Free Convection Flow past a Flat Plate with Heat Source and Convective Surface Boundary Condition

OpenAIRE

E.Hemalatha; N. Bhaskar Reddy

2015-01-01

This paper analyzes the radiation and chemical reaction effects on MHD steady two-dimensional laminar viscous incompressible radiating boundary layer flow over a flat plate in the presence of internal heat generation and convective boundary condition. It is assumed that lower surface of the plate is in contact with a hot fluid while a stream of cold fluid flows steadily over the upper surface with a heat source that decays exponentially. The Rosseland approximation is used to desc...

High-velocity basal sediment package atop oceanic crust, offshore Cascadia: Impacts on plate boundary processes and fluid migration

Science.gov (United States)

Peterson, D. E.; Keranen, K. M.

2017-12-01

Differences in fluid pressure and mechanical properties at megathrust boundaries in subduction zones have been proposed to create varying seismogenic behavior. In Cascadia, where large ruptures are possible but little seismicity occurs presently, new seismic transects across the deformation front (COAST cruise; Holbrook et al., 2012) image an unusually high-wavespeed sedimentary unit directly overlying oceanic crust. Wavespeed increases before sediments reach the deformation front, and the well-laminated unit, consistently of 1 km thickness, can be traced for 50 km beneath the accretionary prism before imaging quality declines. Wavespeed is modeled via iterative prestack time migration (PSTM) imaging and increases from 3.5 km/sec on the seaward end of the profile to >5.0 km/s near the deformation front. Landward of the deformation front, wavespeed is low along seaward-dipping thrust faults in the Quaternary accretionary prism, indicative of rapid dewatering along faults. The observed wavespeed of 5.5 km/sec just above subducting crust is consistent with porosity intersects the plate boundary at an oblique angle and changes the degree of hydration of the oceanic plate as it subducts within our area. Fluid flow out of oceanic crust is likely impeded by the low-porosity basal sediment package except along the focused thrust faults. Decollements are present at the top of oceanic basement, at the top of the high-wavespeed basal unit, and within sedimentary strata at higher levels; the decollement at the top of oceanic crust is active at the toe of the deformation front. The basal sedimentary unit appears to be mechanically strong, similar to observations from offshore Sumatra, where strongly consolidated sediments at the deformation front are interpreted to facilitate megathrust rupture to the trench (Hupers et al., 2017). A uniformly strong plate interface at Cascadia may inhibit microseismicity while building stress that is released in great earthquakes.

Large Eddy Simulation of Supersonic Boundary Layer Transition over a Flat-Plate Based on the Spatial Mode

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Suozhu Wang

2014-02-01

Full Text Available The large eddy simulation (LES of spatially evolving supersonic boundary layer transition over a flat-plate with freestream Mach number 4.5 is performed in the present work. The Favre-filtered Navier-Stokes equations are used to simulate large scales, while a dynamic mixed subgrid-scale (SGS model is used to simulate subgrid stress. The convective terms are discretized with a fifth-order upwind compact difference scheme, while a sixth-order symmetric compact difference scheme is employed for the diffusive terms. The basic mean flow is obtained from the similarity solution of the compressible laminar boundary layer. In order to ensure the transition from the initial laminar flow to fully developed turbulence, a pair of oblique first-mode perturbation is imposed on the inflow boundary. The whole process of the spatial transition is obtained from the simulation. Through the space-time average, the variations of typical statistical quantities are analyzed. It is found that the distributions of turbulent Mach number, root-mean-square (rms fluctuation quantities, and Reynolds stresses along the wall-normal direction at different streamwise locations exhibit self-similarity in fully developed turbulent region. Finally, the onset and development of large-scale coherent structures through the transition process are depicted.

Modelling and solution of contact problem for infinite plate and cross-shaped embedment

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O.B. Kozin

2016-09-01

Full Text Available Development of efficient methods of determination of an intense-strained state of thin-walled constructional designs with inclusions, reinforcements and other stress raisers is an important problem both with theoretical, and from the practical point of view, considering their wide practical application. Aim: The aim of this research is to develop the analytical mathematical method of studying of an intense-strained state of infinite plate with cross-shaped embedment at a bend. Materials and Methods: The method of boundary elements is an efficient way of the boundary value problems solution for systems of differential equations. The methods based on boundary integral equations get wide application in many branches of science and technique, calculation of plates and shells. One of methods of solution of a numerous class of the integral equations and systems arising on the basis of a method of boundary integral equations is the analytical method of construction of these equations and systems to Riemann problems with their forthcoming decision. Results: The integral equation for the analysis of deflections and the analysis of an intense-strained state of a thin rigid plate with rigid cross-shaped embedment is received. The precise solution of this boundary value problem is received by reduction to a Riemann problem and its forthcoming solution. An asymptotical behavior of contact efforts at the ends of embedment is investigated.

On the vibrations of a simply supported square plate on a weakly nonlinear elastic foundation

NARCIS (Netherlands)

Zarubinskaya, M.A.; Van Horssen, W.T.

2003-01-01

In this paper an initial-boundary value problem for a weakly nonlinear plate equation with a quadratic nonlinearity will be studied. This initial-boundary value problem can be regarded as a simple model describing free oscillations of a simply supported square plate on an elastic foundation. It is

Boundary Layer Flow and Heat Transfer with Variable Fluid Properties on a Moving Flat Plate in a Parallel Free Stream

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Norfifah Bachok

2012-01-01

Full Text Available The steady boundary layer flow and heat transfer of a viscous fluid on a moving flat plate in a parallel free stream with variable fluid properties are studied. Two special cases, namely, constant fluid properties and variable fluid viscosity, are considered. The transformed boundary layer equations are solved numerically by a finite-difference scheme known as Keller-box method. Numerical results for the flow and the thermal fields for both cases are obtained for various values of the free stream parameter and the Prandtl number. It is found that dual solutions exist for both cases when the fluid and the plate move in the opposite directions. Moreover, fluid with constant properties shows drag reduction characteristics compared to fluid with variable viscosity.

Stress Transfer Processes during Great Plate Boundary Thrusting Events: A Study from the Andaman and Nicobar Segments

Science.gov (United States)

Andrade, V.; Rajendran, K.

2010-12-01

The response of subduction zones to large earthquakes varies along their strike, both during the interseismic and post-seismic periods. The December 26, 2004 earthquake nucleated at 3° N latitude and its rupture propagated northward, along the Andaman-Sumatra subduction zone, terminating at 15°N. Rupture speed was estimated at about 2.0 km per second in the northern part under the Andaman region and 2.5 - 2.7 km per second under southern Nicobar and North Sumatra. We have examined the pre and post-2004 seismicity to understand the stress transfer processes within the subducting plate, in the Andaman (10° - 15° N ) and Nicobar (5° - 10° N) segments. The seismicity pattern in these segments shows distinctive characteristics associated with the outer rise, accretionary prism and the spreading ridge, all of which are relatively better developed in the Andaman segment. The Ninety East ridge and the Sumatra Fault System are significant tectonic features in the Nicobar segment. The pre-2004 seismicity in both these segments conform to the steady-state conditions wherein large earthquakes are fewer and compressive stresses dominate along the plate interface. Among the pre-2004 great earthquakes are the 1881 Nicobar and 1941 Andaman events. The former is considered to be a shallow thrust event that generated a small tsunami. Studies in other subduction zones suggest that large outer-rise tensional events follow great plate boundary breaking earthquakes due to the the up-dip transfer of stresses within the subducting plate. The seismicity of the Andaman segment (1977-2004) concurs with the steady-state stress conditions where earthquakes occur dominantly by thrust faulting. The post-2004 seismicity shows up-dip migration along the plate interface, with dominance of shallow normal faulting, including a few outer rise events and some deeper (> 100 km) strike-slip faulting events within the subducting plate. The September 13, 2002, Mw 6.5 thrust faulting earthquake at

Electromagnetic on-aircraft antenna radiation in the presence of composite plates

Science.gov (United States)

Kan, S. H-T.; Rojas, R. G.

1994-01-01

The UTD-based NEWAIR3 code is modified such that it can model modern aircraft by composite plates. One good model of conductor-backed composites is the impedance boundary condition where the composites are replaced by surfaces with complex impedances. This impedance-plate model is then used to model the composite plates in the NEWAIR3 code. In most applications, the aircraft distorts the desired radiation pattern of the antenna. However, test examples conducted in this report have shown that the undesired scattered fields are minimized if the right impedance values are chosen for the surface impedance plates.

An analysis of the relaxation of laminar boundary layer on a flat plate after passage of an interface with application to expansion-tube flows

Science.gov (United States)

Gupta, R. N.

1972-01-01

The relaxation of the accelerating-gas boundary layer to the test-gas boundary layer over a flat plate in an expansion tube is analyzed. Several combinations of test gas and acceleration gas are considered. The problem is treated in two conically similar limits: (1) when the time lag between the arrival of the shock and the interface at the leading edge of the plate is very large, and (2) when this lag is negligible. The time-dependent laminar-boundary-layer equations of a binary mixture of perfect gases are taken as the flow-governing equations. This coupled set of differential equations, written in terms of the Lam-Crocco variables, has been solved by a line-relaxation finite-difference techniques. The results presented include the Stanton number and the local skin-friction coefficient as functions of shock Mach number and the nondimensional distance-time variable. The results indicate that more than 95 percent of the test-gas boundary layer exists over a length, measured from the leading edge of the plate, equal to about three-tenths of the distance traversed by the interface in the free stream.

Structural Response of Submerged Air-Backed Plates by Experimental and Numerical Analyses

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Lloyd Hammond

2000-01-01

Full Text Available This paper presents the results of a series of small-scale underwater shock experiments that measured the structural responses of submerged, fully clamped, air-backed, steel plates to a range of high explosive charge sizes. The experimental results were subsequently used to validate a series of simulations using the coupled LS-DYNA/USA finite element/boundary element codes. The modelling exercise was complicated by a significant amount of local cavitation occurring in the fluid adjacent to the plate and difficulties in modelling the boundary conditions of the test plates. The finite element model results satisfactorily predicted the displacement-time history of the plate over a range of shock loadings although a less satisfactory correlation was achieved for the peak velocities. It is expected that the predictive capability of the finite element model will be significantly improved once hydrostatic initialisation can be fully utilised with the LS-DYNA/USA software.

Deciphering Detailed Plate Kinematics of the Indian Ocean: A Combined Indian-Australian-French Initiative

Science.gov (United States)

Vadakkeyakath, Y.; Müller, R.; Dyment, J.; Bhattacharya, G.; Lister, G. S.; Kattoju, K. R.; Whittaker, J.; Shuhail, M.; Gibbons, A.; Jacob, J.; White, L. T.; Bissessur, P. D.; Kiranmai, S.

2012-12-01

The Indian Ocean formed as a result of the fragmentation and dispersal of East Gondwanaland since the Jurassic. The deep ocean basins in the Indian Ocean contain the imprints of this plate tectonic history, which is related with several major events such as the Kerguelen, Marion and Reunion hotspot inception and the Indo-Eurasian collision. A broad model for evolution of the Indian Ocean was proposed in the early 1980s. Subsequently, French scientists collected a large amount of magnetic data from the western and southern parts of the Indian Ocean while Indian and Australian scientists collected considerable volumes of magnetic data from the regions of Indian Ocean around their mainlands. Using these data, the Indian, French and Australian researchers independently carried out investigations over different parts of the Indian Ocean and provided improved models of plate kinematics at different sectoral plate boundaries. Under two Indo-French collaborative projects, detailed magnetic investigations were carried out in the Northwestern and Central Indian Ocean by combining the available magnetic data from conjugate regions. Those projects were complemented by additional area-specific studies in the Mascarene, Wharton, Laxmi and Gop basins, which are characterized by extinct spreading regimes. These Indo-French projects provided high resolution and improved plate tectonic models for the evolution of the conjugate Arabian and Eastern Somali basins that constrain the relative motion between the Indian-African (now Indian-Somalian) plate boundaries, and the conjugate Central Indian, Crozet and Madagascar basins that mainly constrain the relative motions of Indian-African (now Capricorn-Somalian) and Indian-Antarctic (now Capricorn-Antarctic) plate boundaries. During the same period, Australian scientists carried out investigations in the southeastern part of the Indian Ocean and provided an improved understanding of the plate tectonic evolution of the Indian

A model for the motion of the Philippine Sea plate consistent with NUVEL-1 and geological data

Science.gov (United States)

Seno, Tetsuzo; Stein, Seth; Gripp, Alice E.

1993-01-01

We investigate angular velocity vectors of the Philippine Sea (PH) plate relative to the adjacent major plates, Eurasia (EU) and Pacific (PA), and the smaller Caroline (CR) plate. Earthquake slip vector data along the Philippine Sea plate are inverted, subject to the constraint that EU-PA motion equals that predicted by the global relative plate model NUVEL-1. The resulting solution fails to satisfy geological constraints along the Caroline-Pacific boundary: convergence along the Mussau Trench and divergence along the Sorol Trough. We then seek solutions satisfying both the CR-PA boundary conditions and the Philippine Sea slip vector data, by adjusting the PA-PH and EU-PH best fitting poles within their error ellipses. We also consider northern Honshu to be part of the North American plate and impose the constraint that the Philippine Sea plate subducts beneath northern Honshu along the Sagmi Trough in a NNW-NW direction. Of the solutions satisfying these conditions, we select the best EU-PH as 48.2 deg N, 157.0 deg E, 1.09 deg/my, corresponding to a pole far from Japan and south of Kamchatka, and PA-PH, 1.2 deg N, 134.2 deg E, 1.00 deg/my. Predicted NA-PH and EU-PH convergence rates in central Honshu are consistent with estimated seismic slip rates. Previous estimates of the EU-PH pole close to central Honshu are inconsistent with extension within the Bonin backarc implied by earthquake slip vectors and NNW-NW convergence of the Bonin forearc at the Sagami Trough.

Boundary Layer of Photon Absorption Applied to Heterogeneous Photocatalytic Solar Flat Plate Reactor Design

Directory of Open Access Journals (Sweden)

Héctor L. Otálvaro-Marín

2014-01-01

Full Text Available This study provides information to design heterogeneous photocatalytic solar reactors with flat plate geometry used in treatment of effluents and conversion of biomass to hydrogen. The concept of boundary layer of photon absorption taking into account the efficient absorption of radiant energy was introduced; this concept can be understood as the reactor thickness measured from the irradiated surface where 99% of total energy is absorbed. Its thickness and the volumetric rate of photons absorption (VRPA were used as design parameters to determine (i reactor thickness, (ii maximum absorbed radiant energy, and (iii the optimal catalyst concentration. Six different commercial brands of titanium dioxide were studied: Evonik-Degussa P-25, Aldrich, Merck, Hombikat, Fluka, and Fisher. The local volumetric rate of photon absorption (LVRPA inside the reactor was described using six-flux absorption-scattering model (SFM applied to solar radiation. The radiation field and the boundary layer thickness of photon absorption were simulated with absorption and dispersion effects of catalysts in water at different catalyst loadings. The relationship between catalyst loading and reactor thickness that maximizes the absorption of radiant energy was obtained for each catalyst by apparent optical thickness. The optimum concentration of photocatalyst Degussa P-25 was 0.2 g/l in 0.86 cm of thickness, and for photocatalyst Aldrich it was 0.3 g/l in 0.80 cm of thickness.

Skin friction drag reduction on a flat plate turbulent boundary layer using synthetic jets

Science.gov (United States)

Belanger, Randy; Boom, Pieter D.; Hanson, Ronald E.; Lavoie, Philippe; Zingg, David W.

2017-11-01

In these studies, we investigate the effect of mild synthetic jet actuation on a flat plate turbulent boundary layer with the goal of interacting with the large scales in the log region of the boundary layer and manipulating the overall skin friction. Results will be presented from both large eddy simulations (LES) and wind tunnel experiments. In the experiments, a large parameter space of synthetic jet frequency and amplitude was studied with hot film sensors at select locations behind a pair of synthetic jets to identify the parameters that produce the greatest changes in the skin friction. The LES simulations were performed for a selected set of parameters and provide a more complete evaluation of the interaction between the boundary layer and synthetic jets. Five boundary layer thicknesses downstream, the skin friction between the actuators is generally found to increase, while regions of reduced skin friction persist downstream of the actuators. This pattern is reversed for forcing at low frequency. Overall, the spanwise-averaged skin friction is increased by the forcing, except when forcing at high frequency and low amplitude, for which a net skin friction reduction persists downstream. The physical interpretation of these results will be discussed. The financial support of Airbus is gratefully acknowledged.

Asymmetric Vibration of Polar Orthotropic Annular Circular Plates of Quadratically Varying Thickness with Same Boundary Conditions

Directory of Open Access Journals (Sweden)

N. Bhardwaj

2008-01-01

Full Text Available In the present paper, asymmetric vibration of polar orthotropic annular circular plates of quadratically varying thickness resting on Winkler elastic foundation is studied by using boundary characteristic orthonormal polynomials in Rayleigh-Ritz method. Convergence of the results is tested and comparison is made with results already available in the existing literature. Numerical results for the first ten frequencies for various values of parameters describing width of annular plate, thickness profile, material orthotropy and foundation constant for all three possible combinations of clamped, simply supported and free edge conditions are shown and discussed. It is found that (a higher elastic property in circumferential direction leads to higher stiffness against lateral vibration; (b Lateral vibration characteristics of F-Fplates is more sensitive towards parametric changes in material orthotropy and foundation stiffness than C-C and S-Splates; (c Effect of quadratical thickness variation on fundamental frequency is more significant in cases of C-C and S-S plates than that of F-Fplates. Thickness profile which is convex relative to plate center-line tends to result in higher stiffness of annular plates against lateral vibration than the one which is concave and (d Fundamental mode of vibration of C-C and S-Splates is axisymmetrical while that of F-Fplates is asymmetrical.

Focused Fluid Flow along Convergent Plate Boundaries - Deriving Flow Rates along Faults from Local Upwarping of the Base of the Gas Hydrate Stability Zone

Science.gov (United States)

Kunath, P.; Chi, W. C.; Liu, C. S.

2017-12-01

Convergent plate boundaries provide the ideal opportunity to examine the interactions of deformation, fluid flow and gas hydrate stability. However, there are still processes and parameters that remain unclear or scarce. This may be in part due to the fact that in situ determination of fluid flow rate is very difficult. Here, we present a newly developed 2-D hydrothermal model for (1) simulating the steady state, thermal effect of forced heat advection along a thin and shallow dipping fault and (2) quantifying fluid velocities required to deliver a thermal anomalies manifested at the bottom-simulating reflector (BSR) at its intersection with the fault zone. Assuming the horizontal thermal conduction is negligible, we derive our model using only a few crucial parameters: (a) the thermal conductivity structure between seafloor and fault; (b) the temperature at BSR depth and the seafloor; (c) fluid flow rate; (d) geometry of the fault conduit, including depth and thickness. Temperature disturbance is then described as a function of Peclet number and of the dip of the fault. Application of our model to Site 892 at Cascadia accretionary wedge (ODP Leg 146), where borehole data provide excellent thermal constraints on the hydrology, shows consistent results. By comparing the temperatures derived at the BSRs with the temperature field of our model, the results demonstrate that the temperature discrepancy is about 0 - 0.5 oC. We propose that this simple approach can provide, on the basis of a few parameters, rough estimate of the disturbance of the temperature caused by advecting fluid. Localized lateral BSR-based heat flow variations have been observed near thrust faults along many convergent plate boundaries around the world and are associated with strong localized fluid flow. We wish to further testing this approach using other seismic datasets to estimate first order of magnitude fluid migration patterns in other convergent boundaries.

Boundary Layer Flow and Heat Transfer of FMWCNT/Water Nanofluids over a Flat Plate

Directory of Open Access Journals (Sweden)

Mohammad Reza Safaei

2016-09-01

Full Text Available In the present study, the heat transfer and flow of water/FMWCNT (functionalized multi-walled carbon nanotube nanofluids over a flat plate was investigated using a finite volume method. Simulations were performed for velocity ranging from 0.17 mm/s to 1.7 mm/s under laminar regime and nanotube concentrations up to 0.2%. The 2-D governing equations were solved using an in-house FORTRAN code. For a specific free stream velocity, the presented results showed that increasing the weight percentage of nanotubes increased the Nusselt number. However, an increase in the solid weight percentage had a negligible effect on the wall shear stress. The results also indicated that increasing the free stream velocity for all cases leads to thinner boundary layer thickness, while increasing the FMWCNT concentration causes an increase in the boundary layer thickness.

Interaction between central volcanoes and regional tectonics along divergent plate boundaries: Askja, Iceland

Science.gov (United States)

Trippanera, Daniele; Ruch, Joël; Acocella, Valerio; Thordarson, Thor; Urbani, Stefano

2018-01-01

Activity within magmatic divergent plate boundaries (MDPB) focuses along both regional fissure swarms and central volcanoes. An ideal place to investigate their mutual relationship is the Askja central volcano in Iceland. Askja consists of three nested calderas (namely Kollur, Askja and Öskjuvatn) located within a hyaloclastite massif along the NNE-SSW trending Icelandic MDPB. We performed an extensive field-based structural analysis supported by a remote sensing study of tectonic and volcanic features of Askja's calderas and of the eastern flank of the hyaloclastite massif. In the massif, volcano-tectonic structures trend N 10° E to N 40° E, but they vary around the Askja caldera being both parallel to the caldera rim and cross-cutting on the Western side. Structural trends around the Öskjuvatn caldera are typically rim parallel. Volcanic vents and dikes are preferentially distributed along the caldera ring faults; however, they follow the NNE-SSW regional structures when located outside the calderas. Our results highlight that the Askja volcano displays a balanced amount of regional (fissure-swarm related) and local (shallow-magma-chamber related) tectonic structures along with a mutual interaction among these. This is different from Krafla volcano (to the north of Askja) dominated by regional structures and Grímsvötn (to the South) dominated by local structures. Therefore, Askja represents an intermediate tectono-magmatic setting for volcanoes located in a slow divergent plate boundary. This is also likely in accordance with a northward increase in the spreading rate along the Icelandic MDPB.

Interaction between central volcanoes and regional tectonics along divergent plate boundaries: Askja, Iceland

KAUST Repository

Trippanera, Daniele

2017-12-04

Activity within magmatic divergent plate boundaries (MDPB) focuses along both regional fissure swarms and central volcanoes. An ideal place to investigate their mutual relationship is the Askja central volcano in Iceland. Askja consists of three nested calderas (namely Kollur, Askja and Öskjuvatn) located within a hyaloclastite massif along the NNE-SSW trending Icelandic MDPB. We performed an extensive field-based structural analysis supported by a remote sensing study of tectonic and volcanic features of Askja’s calderas and of the eastern flank of the hyaloclastite massif. In the massif, volcano-tectonic structures trend N 10° E to N 40° E, but they vary around the Askja caldera being both parallel to the caldera rim and cross-cutting on the Western side. Structural trends around the Öskjuvatn caldera are typically rim parallel. Volcanic vents and dikes are preferentially distributed along the caldera ring faults; however, they follow the NNE-SSW regional structures when located outside the calderas. Our results highlight that the Askja volcano displays a balanced amount of regional (fissure-swarm related) and local (shallow-magma-chamber related) tectonic structures along with a mutual interaction among these. This is different from Krafla volcano (to the north of Askja) dominated by regional structures and Grímsvötn (to the South) dominated by local structures. Therefore, Askja represents an intermediate tectono-magmatic setting for volcanoes located in a slow divergent plate boundary. This is also likely in accordance with a northward increase in the spreading rate along the Icelandic MDPB.

Is There Really A North American Plate?

Science.gov (United States)

Krill, A.

2011-12-01

Lithospheric plates are typically identified from earthquake epicenters and evidence such as GPS movements. But no evidence indicates a plate boundary between the North American and South American Plates. Some plate maps show them separated by a transform boundary, but it is only a fracture zone. Other maps show an "undefined plate boundary" or put no boundary between these two plates (check Google images). Early plate maps showed a single large American Plate, quite narrow east of the Caribbean Plate (Le Pichon 1968, Morgan 1968). The North and South American Plates became established by the leading textbook Earth (Press & Siever 1974). On their map, from a Scientific American article by John Dewey (1972), these new plates were separated by an "uncertain plate boundary." The reasons for postulating a North American Plate were probably more psychological than geological. Each of the other continents of the world had its own plate, and North American geologists naturally wanted theirs. Similarly, European geographers used to view Europe as its own continent. A single large plate should again be hypothesized. But the term American Plate would now be ambiguous ("Which plate, North or South?") Perhaps future textbook authors could call it the "Two-American Plate." Textbook authors ultimately decide such global-tectonic matters. I became aware of textbook authors' opinions and influence from my research into the history of Alfred Wegener's continental drift (see Fixists vs. Mobilists by Krill 2011). Leading textbook author Charles Schuchert realized that continental drift would abolish his cherished paleogeographic models of large east-west continents (Eria, Gondwana) and small oceans (Poseiden, Nereis). He and his junior coauthors conspired to keep drift evidence out of their textbooks, from the 1934-editions until the 1969-editions (Physical Geology by Longwell et al. 1969, Historical Geology by Dunbar & Waage 1969). Their textbooks ruled in America. Textbooks

Thermal Shock In Periodic Edge-Cracked Plate Supported By Elastic Foundation

OpenAIRE

Abd El-Fattah A. Rizk

2012-01-01

The study of the transient thermal stress problem for a periodic edge cracks in an elastic plate on an elastic foundations is investigated. This study may also be applied for circumferentially periodic cracked hollow cylinder under transient thermal stresses. Based on previous studies, the cylindrical shell may be modeled by a plate on an elastic foundation. The thermal stresses are generated due to sudden convective cooling on the boundary containing the edge cracks while the other boundary ...

About one counterexample of applying method of splitting in modeling of plating processes

Science.gov (United States)

Solovjev, D. S.; Solovjeva, I. A.; Litovka, Yu V.; Korobova, I. L.

2018-05-01

The paper presents the main factors that affect the uniformity of the thickness distribution of plating on the surface of the product. The experimental search for the optimal values of these factors is expensive and time-consuming. The problem of adequate simulation of coating processes is very relevant. The finite-difference approximation using seven-point and five-point templates in combination with the splitting method is considered as solution methods for the equations of the model. To study the correctness of the solution of equations of the mathematical model by these methods, the experiments were conducted on plating with a flat anode and cathode, which relative position was not changed in the bath. The studies have shown that the solution using the splitting method was up to 1.5 times faster, but it did not give adequate results due to the geometric features of the task under the given boundary conditions.

Dynamic Stress Concentration at the Boundary of an Incision at the Plate Under the Action of Weak Shock Waves

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Mikulich Olena

2017-09-01

Full Text Available This paper proposes the novel technique for analysis of dynamic stress state of multi-connected infinite plates under the action of weak shock waves. For solution of the problem it uses the integral and discrete Fourier transforms. Calculation of transformed dynamic stresses at the incisions of plates is held using the boundary-integral equation method and the theory of complex variable functions. The numerical implementation of the developed algorithm is based on the method of mechanical quadratures and collocation technique. For calculation of originals of the dynamic stresses it uses modified discrete Fourier transform. The algorithm is effective in the analysis of the dynamic stress state of defective plates.

A Source-Term Based Boundary Layer Bleed/Effusion Model for Passive Shock Control

Science.gov (United States)

Baurle, Robert A.; Norris, Andrew T.

2011-01-01

A modeling framework for boundary layer effusion has been developed based on the use of source (or sink) terms instead of the usual practice of specifying bleed directly as a boundary condition. This framework allows the surface boundary condition (i.e. isothermal wall, adiabatic wall, slip wall, etc.) to remain unaltered in the presence of bleed. This approach also lends itself to easily permit the addition of empirical models for second order effects that are not easily accounted for by simply defining effective transpiration values. Two effusion models formulated for supersonic flows have been implemented into this framework; the Doerffer/Bohning law and the Slater formulation. These models were applied to unit problems that contain key aspects of the flow physics applicable to bleed systems designed for hypersonic air-breathing propulsion systems. The ability of each model to predict bulk bleed properties was assessed, as well as the response of the boundary layer as it passes through and downstream of a porous bleed system. The model assessment was performed with and without the presence of shock waves. Three-dimensional CFD simulations that included the geometric details of the porous plate bleed systems were also carried out to supplement the experimental data, and provide additional insights into the bleed flow physics. Overall, both bleed formulations fared well for the tests performed in this study. However, the sample of test problems considered in this effort was not large enough to permit a comprehensive validation of the models.

Global Plate Velocities from the Global Positioning System

Science.gov (United States)

Larson, Kristine M.; Freymueller, Jeffrey T.; Philipsen, Steven

1997-01-01

We have analyzed 204 days of Global Positioning System (GPS) data from the global GPS network spanning January 1991 through March 1996. On the basis of these GPS coordinate solutions, we have estimated velocities for 38 sites, mostly located on the interiors of the Africa, Antarctica, Australia, Eurasia, Nazca, North America, Pacific, and South America plates. The uncertainties of the horizontal velocity components range from 1.2 to 5.0 mm/yr. With the exception of sites on the Pacific and Nazca plates, the GPS velocities agree with absolute plate model predictions within 95% confidence. For most of the sites in North America, Antarctica, and Eurasia, the agreement is better than 2 mm/yr. We find no persuasive evidence for significant vertical motions (less than 3 standard deviations), except at four sites. Three of these four were sites constrained to geodetic reference frame velocities. The GPS velocities were then used to estimate angular velocities for eight tectonic plates. Absolute angular velocities derived from the GPS data agree with the no net rotation (NNR) NUVEL-1A model within 95% confidence except for the Pacific plate. Our pole of rotation for the Pacific plate lies 11.5 deg west of the NNR NUVEL-1A pole, with an angular speed 10% faster. Our relative angular velocities agree with NUVEL-1A except for some involving the Pacific plate. While our Pacific-North America angular velocity differs significantly from NUVEL-1A, our model and NUVEL-1A predict very small differences in relative motion along the Pacific-North America plate boundary itself. Our Pacific-Australia and Pacific- Eurasia angular velocities are significantly faster than NUVEL-1A, predicting more rapid convergence at these two plate boundaries. Along the East Pacific Pise, our Pacific-Nazca angular velocity agrees in both rate and azimuth with NUVFL-1A.

BEPLATE emdash simulation of electrochemical plating

Energy Technology Data Exchange (ETDEWEB)

Giles, G.E. (Oak Ridge K-25 Site, TN (USA)); Gray, L.J. (Oak Ridge National Lab., TN (USA)); Bullock, J.S. IV (Oak Ridge Y-12 Plant, TN (USA))

1990-09-01

BEPLATE is a FORTRAN code that uses the boundary element method to simulate the electrochemical plating of material on parts, primarily rotating axisymmetric parts. A boundary element technique is used to solve for the local current density and thus the plating rate on the part, which is used to calculate the growth in the plated layer over a user-specified time step. The surface is moved to reflect this growth, and the new surface is used to generate the local current density. This cycle is repeated until the final time specified by the analyst, producing the final plated thickness. BEPLATE includes models for the polarization effects at both the part (cathode) and anode and allows the use of symmetry planes and nonconducting shields. For electroplating simulations, the part shape is normally assumed to be axisymmetric with a centerline along the z-axis. More general part shapes can be analyzed by BEPLATE if the surface growth simulation is not needed. In either case, the shield, anode, and tank geometries are not restricted to specific shapes. This report includes the information required to run BEPLATE, specifically, a brief description of the BEPLATE system including hardware and software requirements, a description of the complete simulation process, discussion of rules for generating models, and additional reference material. This system of codes consists of model generators (PIGS or PATRAN), input processor (BEPIN), the simulation code (BEPLATE) and postprocessing codes (PATRAN or CONPLOT).

New Models for Velocity/Pressure-Gradient Correlations in Turbulent Boundary Layers

Science.gov (United States)

Poroseva, Svetlana; Murman, Scott

2014-11-01

To improve the performance of Reynolds-Averaged Navier-Stokes (RANS) turbulence models, one has to improve the accuracy of models for three physical processes: turbulent diffusion, interaction of turbulent pressure and velocity fluctuation fields, and dissipative processes. The accuracy of modeling the turbulent diffusion depends on the order of a statistical closure chosen as a basis for a RANS model. When the Gram-Charlier series expansions for the velocity correlations are used to close the set of RANS equations, no assumption on Gaussian turbulence is invoked and no unknown model coefficients are introduced into the modeled equations. In such a way, this closure procedure reduces the modeling uncertainty of fourth-order RANS (FORANS) closures. Experimental and direct numerical simulation data confirmed the validity of using the Gram-Charlier series expansions in various flows including boundary layers. We will address modeling the velocity/pressure-gradient correlations. New linear models will be introduced for the second- and higher-order correlations applicable to two-dimensional incompressible wall-bounded flows. Results of models' validation with DNS data in a channel flow and in a zero-pressure gradient boundary layer over a flat plate will be demonstrated. A part of the material is based upon work supported by NASA under award NNX12AJ61A.

Deformation of the Northwestern Okhotsk Plate: How is it happening?

OpenAIRE

Hindle, D.; Fujita, K.; Mackey, K.

2009-01-01

The Eurasia (EU) – North America (NA) plate boundary zone across Northeast Asia still presents many open questions within the plate tectonic paradigm. Constraining the geometry and number of plates or microplates present in the plate boundary zone is especially difficult because of the location of the EU-NA euler pole close to or even upon the EU-NA boundary. One of the major challenges remains the geometry of the Okhotsk plate (OK). whose northwestern portion terminates on ...

Vibration characteristics of functionally graded carbon nanotube reinforced composite rectangular plates on Pasternak foundation with arbitrary boundary conditions and internal line supports

Science.gov (United States)

Zhong, Rui; Wang, Qingshan; Tang, Jinyuan; Shuai, Cijun; Liang, Qian

2018-02-01

This paper presents the first known vibration characteristics of moderately thick functionally graded carbon nanotube reinforced composite rectangular plates on Pasternak foundation with arbitrary boundary conditions and internal line supports on the basis of the firstorder shear deformation theory. Different distributions of single walled carbon nanotubes (SWCNTs) along the thickness are considered. Uniform and other three kinds of functionally graded distributions of carbon nanotubes along the thickness direction of plates are studied. The solutions carried out using an enhanced Ritz method mainly include the following three points: Firstly, create the Lagrange energy function by the energy principle; Secondly, as the main innovation point, the modified Fourier series are chosen as the basic functions of the admissible functions of the plates to eliminate all the relevant discontinuities of the displacements and their derivatives at the edges; Lastly, solve the natural frequencies as well as the associated mode shapes by means of the Ritz-variational energy method. In this study, the influences of the volume fraction of CNTs, distribution type of CNTs, boundary restrain parameters, location of the internal line supports, foundation coefficients on the natural frequencies and mode shapes of the FG-CNT reinforced composite rectangular plates are presented.

Development of boundary layers

International Nuclear Information System (INIS)

Herbst, R.

1980-01-01

Boundary layers develop along the blade surfaces on both the pressure and the suction side in a non-stationary flow field. This is due to the fact that there is a strongly fluctuating flow on the downstream blade row, especially as a result of the wakes of the upstream blade row. The author investigates the formation of boundary layers under non-stationary flow conditions and tries to establish a model describing the non-stationary boundary layer. For this purpose, plate boundary layers are measured, at constant flow rates but different interferent frequency and variable pressure gradients. By introducing the sample technique, measurements of the non-stationary boundary layer become possible, and the flow rate fluctuation can be divided in its components, i.e. stochastic turbulence and periodical fluctuation. (GL) [de

Numerical investigation of hypersonic flat-plate boundary layer transition mechanism induced by different roughness shapes

Science.gov (United States)

Zhou, Yunlong; Zhao, Yunfei; Xu, Dan; Chai, Zhenxia; Liu, Wei

2016-10-01

The roughness-induced laminar-turbulent boundary layer transition is significant for high-speed aerospace applications. The transition mechanism is closely related to the roughness shape. In this paper, high-order numerical method is used to investigate the effect of roughness shape on the flat-plate laminar-to-turbulent boundary layer transition. Computations are performed in both the supersonic and hypersonic regimes (free-stream Mach number from 3.37 up to 6.63) for the square, cylinder, diamond and hemisphere roughness elements. It is observed that the square and diamond roughness elements are more effective in inducing transition compared with the cylinder and hemisphere ones. The square roughness element has the longest separated region in which strong unsteadiness exists and the absolute instability is formed, thus resulting in the earliest transition. The diamond roughness element has a maximum width of the separated region leading to the widest turbulent wake region far downstream. Furthermore, transition location moves backward as the Mach number increases, which indicates that the compressibility significantly suppresses the roughness-induced boundary layer transition.

Mechanics and Partitioning of Deformation of the Northwestern Okhostk Plate, Northeast Russia

Science.gov (United States)

Hindle, D.; Mackey, K.; Fujita, K.

2007-12-01

The tectonic evolution and present day deformation of northeastern Russia remains one of the major challenges in plate tectonics. Arguments over the existence of at least a separate Okhotsk plate between North America and Eurasia appear to be resolved on the basis of the latest GPS studies combined with elastic modeling. The question of the mechanical behaviour of the Okhotsk plate, caught between the slowly, obliquely converging North American and Eurasian plates now becomes important. We present an analysis of geological lineaments, micro-seismicity, total seismic moment release and seismic deformation rate and GPS campaign data and global plate tectonic model data (REVEL) to estimate the likelihood of future seismicity and the relative amount of elastic and viscous deformation of the lithosphere of the northwestern Okhotsk plate. We find that it is likely that the Okhotsk plate is cracked into slivers, but that rates of relative motion of these slivers are close to indistinguishable from the behaviour of a single, rigid plate. The analysis also suggests the upper bound for large earthquakes in the region to be Mw 7-7.5 which we expect to occur only on the plate boundary fault itself. This fits geological evidence for a long term offset rate 5-10 times higher on the major plate boundary fault than other lineaments cutting the Okhotsk plate itself.

Sensor for Boundary Shear Stress in Fluid Flow

Science.gov (United States)

Bao, Xiaoqi; Badescu, Mircea; Sherrit, Stewart; Bar-Cohen, Yoseph; Lih, Shyh-Shiuh; Chang, Zensheu; Trease, Brian P.; Kerenyi, Kornel; Widholm, Scott E.; Ostlund, Patrick N.

2012-01-01

The formation of scour patterns at bridge piers is driven by the forces at the boundary of the water flow. In most experimental scour studies, indirect processes have been applied to estimate the shear stress using measured velocity profiles. The estimations are based on theoretical models and associated assumptions. However, the turbulence flow fields and boundary layer in the pier-scour region are very complex and lead to low-fidelity results. In addition, available turbulence models cannot account accurately for the bed roughness effect. Direct measurement of the boundary shear stress, normal stress, and their fluctuations are attractive alternatives. However, most direct-measurement shear sensors are bulky in size or not compatible to fluid flow. A sensor has been developed that consists of a floating plate with folded beam support and an optical grid on the back, combined with a high-resolution optical position probe. The folded beam support makes the floating plate more flexible in the sensing direction within a small footprint, while maintaining high stiffness in the other directions. The floating plate converts the shear force to displacement, and the optical probe detects the plate s position with nanometer resolution by sensing the pattern of the diffraction field of the grid through a glass window. This configuration makes the sensor compatible with liquid flow applications.

Model-based estimation with boundary side information or boundary regularization

International Nuclear Information System (INIS)

Chiao, P.C.; Rogers, W.L.; Fessler, J.A.; Clinthorne, N.H.; Hero, A.O.

1994-01-01

The authors have previously developed a model-based strategy for joint estimation of myocardial perfusion and boundaries using ECT (Emission Computed Tomography). The authors have also reported difficulties with boundary estimation in low contrast and low count rate situations. In this paper, the authors propose using boundary side information (obtainable from high resolution MRI and CT images) or boundary regularization to improve both perfusion and boundary estimation in these situations. To fuse boundary side information into the emission measurements, the authors formulate a joint log-likelihood function to include auxiliary boundary measurements as well as ECT projection measurements. In addition, the authors introduce registration parameters to align auxiliary boundary measurements with ECT measurements and jointly estimate these parameters with other parameters of interest from the composite measurements. In simulated PET O-15 water myocardial perfusion studies using a simplified model, the authors show that the joint estimation improves perfusion estimation performance and gives boundary alignment accuracy of <0.5 mm even at 0.2 million counts. The authors implement boundary regularization through formulating a penalized log-likelihood function. The authors also demonstrate in simulations that simultaneous regularization of the epicardial boundary and myocardial thickness gives comparable perfusion estimation accuracy with the use of boundary side information

Inverse models of plate coupling and mantle rheology: Towards a direct link between large-scale mantle flow and mega thrust earthquakes

Science.gov (United States)

Gurnis, M.; Ratnaswamy, V.; Stadler, G.; Rudi, J.; Liu, X.; Ghattas, O.

2017-12-01

We are developing high-resolution inverse models for plate motions and mantle flow to recover the degree of mechanical coupling between plates and the non-linear and plastic parameters governing viscous flow within the lithosphere and mantle. We have developed adjoint versions of the Stokes equations with fully non-linear viscosity with a cost function that measures the fit with plate motions and with regional constrains on effective upper mantle viscosity (from post-glacial rebound and post seismic relaxation). In our earlier work, we demonstrate that when the temperature field is known, the strength of plate boundaries, the yield stress and strain rate exponent in the upper mantle are recoverable. As the plate boundary coupling drops below a threshold, the uncertainty of the inferred parameters increases due to insensitivity of plate motion to plate coupling. Comparing the trade-offs between inferred rheological parameters found from a Gaussian approximation of the parameter distribution and from MCMC sampling, we found that the Gaussian approximation—which is significantly cheaper to compute—is often a good approximation. We have extended our earlier method such that we can recover normal and shear stresses within the zones determining the interface between subducting and over-riding plates determined through seismic constraints (using the Slab1.0 model). We find that those subduction zones with low seismic coupling correspond with low inferred values of mechanical coupling. By fitting plate motion data in the optimization scheme, we find that Tonga and the Marianas have the lowest values of mechanical coupling while Chile and Sumatra the highest, among the subduction zones we have studies. Moreover, because of the nature of the high-resolution adjoint models, the subduction zones with the lowest coupling have back-arc extension. Globally we find that the non-linear stress-strain exponent, n, is about 3.0 +/- 0.25 (in the upper mantle and lithosphere) and a

3D geometry of a plate boundary fault related to the 2016 Off-Mie earthquake in the Nankai subduction zone, Japan

Science.gov (United States)

Tsuji, Takeshi; Minato, Shohei; Kamei, Rie; Tsuru, Tetsuro; Kimura, Gaku

2017-11-01

We used recent seismic data and advanced techniques to investigate 3D fault geometry over the transition from the partially coupled to the fully coupled plate interface inboard of the Nankai Trough off the Kii Peninsula, Japan. We found that a gently dipping plate boundary décollement with a thick underthrust layer extends beneath the entire Kumano forearc basin. The 1 April 2016 Off-Mie earthquake (Mw6.0) and its aftershocks occurred, where the plate boundary décollement steps down close to the oceanic crust surface. This location also lies beneath the trenchward edge of an older accretionary prism (∼14 Ma) developed along the coast of the Kii peninsula. The strike of the 2016 rupture plane was similar to that of a formerly active splay fault system in the accretionary prism. Thus, the fault planes of the 2016 earthquake and its aftershocks were influenced by the geometry of the plate interface as well as splay faulting. The 2016 earthquake occurred within the rupture area of large interplate earthquakes such as the 1944 Tonankai earthquake (Mw8.1), although the 2016 rupture area was much smaller than that of the 1944 event. Whereas the hypocenter of the 2016 earthquake was around the underplating sequence beneath the younger accretionary prism (∼6 Ma), the 1944 great earthquake hypocenter was close to oceanic crust surface beneath the older accretionary prism. The variation of fault geometry and lithology may influence the degree of coupling along the plate interface, and such coupling variation could hinder slip propagation toward the deeper plate interface in the 2016 event.

An EarthScope Plate Boundary Observatory Progress Report

Science.gov (United States)

Jackson, M.; Anderson, G.; Blume, F.; Walls, C.; Coyle, B.; Feaux, K.; Friesen, B.; Phillips, D.; Hafner, K.; Johnson, W.; Mencin, D.; Pauk, B.; Dittmann, T.

2007-12-01

UNAVCO is building and operating the Plate Boundary Observatory (PBO), part of the NSF-funded EarthScope project to understand the structure, dynamics, and evolution of the North American continent. When complete in October 2008, the 875 GPS, 103 strain and seismic, and 28 tiltmeters stations will comprise the largest integrated geodetic and seismic network in United States and the second largest in the world. Data from the PBO network will facilitate research into plate boundary deformation with unprecedented scope and detail. As of 1 September 2007, UNAVCO had completed 680 PBO GPS stations and had upgraded 89% of the planned PBO Nucleus stations. Highlights of the past year's work include the expansion of the Alaska subnetwork to 95 continuously-operating stations, including coverage of Akutan and Augustine volcanoes and reconnaissance for future installations on Unimak Island; the installation of nine new stations on Mt. St. Helens; and the arrival of 33 permits for station installations on BLM land in Nevada. The Augustine network provided critical data on magmatic and volcanic processes associated with the 2005-2006 volcanic crisis, and has expanded to a total of 11 stations. Please visit http://pboweb.unavco.org/?pageid=3 for further information on PBO GPS network construction activities. As of September 2007, 41 PBO borehole stations had been installed and three laser strainmeter stations were operating, with a total of 60 borehole stations and 4 laser strainmeters expected by October 2007. In response to direction from the EarthScope community, UNAVCO installed a dense network of six stations along the San Jacinto Fault near Anza, California; installed three of four planned borehole strainmeter stations on Mt. St. Helens; and has densified coverage of the Parkfield area. Please visit http://pboweb.unavco.org/?pageid=8 for more information on PBO strainmeter network construction progress. The combined PBO/Nucleus GPS network provides 350 GB of raw standard

Study of Boundary Layer Convective Heat Transfer with Low Pressure Gradient Over a Flat Plate Via He's Homotopy Perturbation Method

International Nuclear Information System (INIS)

Fathizadeh, M.; Aroujalian, A.

2012-01-01

The boundary layer convective heat transfer equations with low pressure gradient over a flat plate are solved using Homotopy Perturbation Method, which is one of the semi-exact methods. The nonlinear equations of momentum and energy solved simultaneously via Homotopy Perturbation Method are in good agreement with results obtained from numerical methods. Using this method, a general equation in terms of Pr number and pressure gradient (λ) is derived which can be used to investigate velocity and temperature profiles in the boundary layer.

Application of a Brittle Damage Model to Normal Plate-on-Plate Impact

National Research Council Canada - National Science Library

Raftenberg, Martin N

2005-01-01

A brittle damage model presented by Grinfeld and Wright of the U.S. Army Research Laboratory was implemented in the LS-DYNA finite element code and applied to the simulation of normal plate-on-plate impact...

Rough horizontal plates: heat transfer and hysteresis

Energy Technology Data Exchange (ETDEWEB)

Tisserand, J-C; Gasteuil, Y; Pabiou, H; Castaing, B; Chilla, F [Universite de Lyon, ENS Lyon, CNRS, 46 Allee d' ltalie, 69364 Lyon Cedex 7 (France); Creyssels, M [LMFA, CNRS, Ecole Centrale Lyon, 69134 Ecully Cedex (France); Gibert, M, E-mail: mathieu.creyssels@ec-lyon.fr [Also at MPI-DS (LFPN) Gottingen (Germany)

2011-12-22

To investigate the influence of a rough-wall boundary layer on turbulent heat transport, an experiment of high-Rayleigh convection in water is carried out in a Rayleigh-Benard cell with a rough lower plate and a smooth upper plate. A transition in the heat transport is observed when the thermal boundary layer thickness becomes comparable to or smaller than the roughness height. Besides, at larger Rayleigh numbers than the threshold value, heat transport is found to be increased up to 60%. This enhancement cannot be explained simply by an increase in the contact area of the rough surface since the contact area is increased only by a factor of 40%. Finally, a simple model is proposed to explain the enhanced heat transport.

Thermal and mechanical modelling of convergent plate margins

NARCIS (Netherlands)

van den Beukel, P.J.

1990-01-01

In this thesis, the thermal and mechanical structure of convergent plate margins will be investigated by means of numerical modelling. In addition, we will discuss the implications of modelling results for geological processes such as metamorphism or the break-up of a plate at a convergent plate

A Long-term Slip Model for the San Ramón Fault, Santiago de Chile, from Tectonically Reconcilable Boundary Conditions

Science.gov (United States)

Aron, F.; Estay, N.; Cembrano, J. M.; Yanez, G. A.

2016-12-01

We constructed a 3D Boundary Elements model simulating subduction of the Nazca plate underneath South America, from 29° to 38° S, to compute long-term surface deformation and slip rates on crustal faults imbedded in the upper-plate wedge of the Andean orogen. We tested our model on the San Ramón Fault (SRF), a major E-dipping, thrust structure limiting the western front of the Main Cordillera with surface expression along the entire, 40 km long, extension of the Santiago de Chile basin. Long-lived thrusting has produced more than 2 km of differential uplift of the mountains. Given its proximity to the country's largest city, this potentially seismogenic fault —dormant during historic times— has drawn increasing public attention. We used earthquake hypocenters captured over a one-year seismic deployment, 2D resistivity profiles, and published geologic cross-sections to determine the geometry of the SRF. The base of the lithosphere and plate interface surfaces were defined based on average Andean values and the Slab1.0 model. The simulation reproduces plate convergence and mechanic decoupling of the lithospheric plates across the subduction seismic cycle using mixed boundary conditions. Relative plate motion is achieved prescribing uniform, far-field horizontal displacement over the depth extension of both the oceanic and continental lithospheric plates. Long-term deformation is carried out in two steps. First, the modeled surfaces are allowed to slip freely emulating continuous slip on the subduction megathrust; subsequently, zero displacement is prescribed on the locking zone of the megathrust down to 40 km depth, while keeping the rest of the surfaces traction free, mimicking interseismic conditions. Long-term slip rate fields obtained for the SRF range between 0.1 and 1% the plate convergence rate, with maximum values near the surface. Interestingly, at an estimated 76-77 mm/yr relative plate motion velocity, those rates agree well with what has been

Investigation of acoustic field near to elastic thin plate using integral method

Directory of Open Access Journals (Sweden)

В.І. Токарев

2004-01-01

Full Text Available  Investigation of acoustic field near to elastic thin plate using  integral method The influence of boundary conditions on sound wave propagation, radiation and transmission through thin elastic plate is investigated. Necessary for that numerical model was found using the Helmholtz equation and equation of oscilated plate by means of integral formulation of the solution for acoustic fields near to elastic thin plate and for bending waves of small amplitudes.

Correlations for modeling transitional boundary layers under influences of freestream turbulence and pressure gradient

International Nuclear Information System (INIS)

Suluksna, Keerati; Dechaumphai, Pramote; Juntasaro, Ekachai

2009-01-01

This paper presents mathematical expressions for two significant parameters which control the onset location and length of transition in the γ-Re θ transition model of Menter et al. [Menter, F.R., Langtry, R.B., Volker, S., Huang, P.G., 2005. Transition modelling for general purpose CFD codes. In: ERCOFTAC International Symposium on Engineering Turbulence Modelling and Measurements]. The expressions are formulated and calibrated by means of numerical experiments for predicting transitional boundary layers under the influences of freestream turbulence and pressure gradient. It was also found that the correlation for transition momentum thickness Reynolds number needs only to be expressed in terms of local turbulence intensity, so that the more complex form that includes pressure gradient effects is unnecessary. Transitional boundary layers on a flat plate both with and without pressure gradients are employed to assess the performance of these two expressions for predicting the transition. The results show that the proposed expressions can work well with the model of Menter et al. (2005)

Modeling RERTR experimental fuel plates using the PLATE code

International Nuclear Information System (INIS)

Hayes, S.L.; Meyer, M.K.; Hofman, G.L.; Snelgrove, J.L.; Brazener, R.A.

2003-01-01

Modeling results using the PLATE dispersion fuel performance code are presented for the U-Mo/Al experimental fuel plates from the RERTR-1, -2, -3 and -5 irradiation tests. Agreement of the calculations with experimental data obtained in post-irradiation examinations of these fuels, where available, is shown to be good. Use of the code to perform a series of parametric evaluations highlights the sensitivity of U-Mo dispersion fuel performance to fabrication variables, especially fuel particle shape and size distributions. (author)

Unsteady boundary layer flow and heat transfer of a Casson fluid past an oscillating vertical plate with Newtonian heating.

Science.gov (United States)

Hussanan, Abid; Zuki Salleh, Mohd; Tahar, Razman Mat; Khan, Ilyas

2014-01-01

In this paper, the heat transfer effect on the unsteady boundary layer flow of a Casson fluid past an infinite oscillating vertical plate with Newtonian heating is investigated. The governing equations are transformed to a systems of linear partial differential equations using appropriate non-dimensional variables. The resulting equations are solved analytically by using the Laplace transform method and the expressions for velocity and temperature are obtained. They satisfy all imposed initial and boundary conditions and reduce to some well-known solutions for Newtonian fluids. Numerical results for velocity, temperature, skin friction and Nusselt number are shown in various graphs and discussed for embedded flow parameters. It is found that velocity decreases as Casson parameters increases and thermal boundary layer thickness increases with increasing Newtonian heating parameter.

Analytical model of unsteady-state convective heat transfer between the heat carrier and the finite sizes plate adjusted for the thermal relaxation

Directory of Open Access Journals (Sweden)

Makarushkin Danila

2017-01-01

Full Text Available A hyperbolic boundary value problem of the thermal conduction of a two-dimensional plate with the third kind boundary conditions is formulated. The transient thermal process in the plate is due to the temperature changes of the external medium over time and along the plate length, and also by a multiple step change of the plate surface heat transfer coefficient throughout the transient process. An analytical solution with improved convergence adjusted for thermal relaxation and thermal damping is obtained for the temperature field in the plate.

Rheological structure of the lithosphere in plate boundary strike-slip fault zones

Science.gov (United States)

Chatzaras, Vasileios; Tikoff, Basil; Kruckenberg, Seth C.; Newman, Julie; Titus, Sarah J.; Withers, Anthony C.; Drury, Martyn R.

2016-04-01

How well constrained is the rheological structure of the lithosphere in plate boundary strike-slip fault systems? Further, how do lithospheric layers, with rheologically distinct behaviors, interact within the strike-slip fault zones? To address these questions, we present rheological observations from the mantle sections of two lithospheric-scale, strike-slip fault zones. Xenoliths from ˜40 km depth (970-1100 ° C) beneath the San Andreas fault system (SAF) provide critical constraints on the mechanical stratification of the lithosphere in this continental transform fault. Samples from the Bogota Peninsula shear zone (BPSZ, New Caledonia), which is an exhumed oceanic transform fault, provide insights on lateral variations in mantle strength and viscosity across the fault zone at a depth corresponding to deformation temperatures of ˜900 ° C. Olivine recrystallized grain size piezometry suggests that the shear stress in the SAF upper mantle is 5-9 MPa and in the BPSZ is 4-10 MPa. Thus, the mantle strength in both fault zones is comparable to the crustal strength (˜10 MPa) of seismogenic strike-slip faults in the SAF system. Across the BPSZ, shear stress increases from 4 MPa in the surrounding rocks to 10 MPa in the mylonites, which comprise the core of the shear zone. Further, the BPSZ is characterized by at least one order of magnitude difference in the viscosity between the mylonites (1018 Paṡs) and the surrounding rocks (1019 Paṡs). Mantle viscosity in both the BPSZ mylonites and the SAF (7.0ṡ1018-3.1ṡ1020 Paṡs) is relatively low. To explain our observations from these two strike-slip fault zones, we propose the "lithospheric feedback" model in which the upper crust and lithospheric mantle act together as an integrated system. Mantle flow controls displacement and the upper crust controls the stress magnitude in the system. Our stress data combined with data that are now available for the middle and lower crustal sections of other transcurrent fault

Bending and stretching of plates

CERN Document Server

Mansfield, E H; Hemp, W S

1964-01-01

The Bending and Stretching of Plates deals with elastic plate theory, particularly on small- and large-deflexion theory. Small-deflexion theory concerns derivation of basic equations, rectangular plates, plates of various shapes, plates whose boundaries are amenable to conformal transformation, plates with variable rigidity, and approximate methods. Large-deflexion theory includes general equations and some exact solutions, approximate methods in large-deflexion theory, asymptotic large-deflexion theories for very thin plates. Asymptotic theories covers membrane theory, tension field theory, a

Conformal boundary loop models

International Nuclear Information System (INIS)

Jacobsen, Jesper Lykke; Saleur, Hubert

2008-01-01

We study a model of densely packed self-avoiding loops on the annulus, related to the Temperley-Lieb algebra with an extra idempotent boundary generator. Four different weights are given to the loops, depending on their homotopy class and whether they touch the outer rim of the annulus. When the weight of a contractible bulk loop x≡q+q -1 element of (-2,2], this model is conformally invariant for any real weight of the remaining three parameters. We classify the conformal boundary conditions and give exact expressions for the corresponding boundary scaling dimensions. The amplitudes with which the sectors with any prescribed number and types of non-contractible loops appear in the full partition function Z are computed rigorously. Based on this, we write a number of identities involving Z which hold true for any finite size. When the weight of a contractible boundary loop y takes certain discrete values, y r ≡([r+1] q )/([r] q ) with r integer, other identities involving the standard characters K r,s of the Virasoro algebra are established. The connection with Dirichlet and Neumann boundary conditions in the O(n) model is discussed in detail, and new scaling dimensions are derived. When q is a root of unity and y=y r , exact connections with the A m type RSOS model are made. These involve precise relations between the spectra of the loop and RSOS model transfer matrices, valid in finite size. Finally, the results where y=y r are related to the theory of Temperley-Lieb cabling

Geometry and structure of the pull-apart basins developed along the western South American-Scotia plate boundary (SW Atlantic Ocean)

Science.gov (United States)

Esteban, F. D.; Tassone, A.; Isola, J. I.; Lodolo, E.; Menichetti, M.

2018-04-01

The South American-Scotia plate boundary is a left-lateral fault system which runs roughly E-W for more than 3000 km across the SW Atlantic Ocean and the Tierra del Fuego Island, reaching to the west the southern Chile Trench. Analyses of a large dataset of single- and multi-channel seismic reflection profiles acquired offshore has allowed to map the trace of the plate boundary from Tierra del Fuego to the Malvinas Trough, a tectonic depression located in the eastern part of the fault system, and to reconstruct the shape and geometry of the basins formed along the principal displacement zone of the fault system. Three main Neogene pull-apart basins that range from 70 to 100 km in length, and from 12 to 22 km in width, have been identified along this segment of the plate boundary. These basins have elongated shapes with their major axes parallel to the ENE-WSW direction of the fault zone. The sedimentary architecture and the infill geometry of the basins suggest that they represent mostly strike-slip dominated transtension basins which propagated from E to W. The basins imaged by seismic data show in some cases geometrical and structural features linked to the possible reactivation of previous wedge-top basins and inherited structures pertaining to the external front of the Magallanes fold-and-thrust compression belt, along which the South American-Scotia fault system has been superimposed. It is suggested that the sequence of the elongated basins occur symmetrically to a thorough going strike-slip fault, in a left-stepping geometrical arrangement, in a manner similar to those basins seen in other transcurrent environments.

Boundary correlators in supergroup WZNW models

Energy Technology Data Exchange (ETDEWEB)

Creutzig, T.; Schomerus, V.

2008-04-15

We investigate correlation functions for maximally symmetric boundary conditions in the WZNW model on GL(11). Special attention is payed to volume filling branes. Generalizing earlier ideas for the bulk sector, we set up a Kac-Wakimotolike formalism for the boundary model. This first order formalism is then used to calculate bulk-boundary 2-point functions and the boundary 3-point functions of the model. The note ends with a few comments on correlation functions of atypical fields, point-like branes and generalizations to other supergroups. (orig.)

Mathematical methods for elastic plates

CERN Document Server

Constanda, Christian

2014-01-01

Mathematical models of deformation of elastic plates are used by applied mathematicians and engineers in connection with a wide range of practical applications, from microchip production to the construction of skyscrapers and aircraft. This book employs two important analytic techniques to solve the fundamental boundary value problems for the theory of plates with transverse shear deformation, which offers a more complete picture of the physical process of bending than Kirchhoff’s classical one.   The first method transfers the ellipticity of the governing system to the boundary, leading to singular integral equations on the contour of the domain. These equations, established on the basis of the properties of suitable layer potentials, are then solved in spaces of smooth (Hölder continuous and Hölder continuously differentiable) functions.   The second technique rewrites the differential system in terms of complex variables and fully integrates it, expressing the solution as a combination of complex ana...

Modelling of CMUTs with Anisotropic Plates

DEFF Research Database (Denmark)

la Cour, Mette Funding; Christiansen, Thomas Lehrmann; Jensen, Jørgen Arendt

2012-01-01

Traditionally, CMUTs are modelled using the isotropic plate equation and this leads to deviations between analytical calculations and FEM simulations. In this paper, the deflection profile and material parameters are calculated using the anisotropic plate equation. It is shown that the anisotropic...... calculations match perfectly with FEM while an isotropic approach causes up to 10% deviations in deflection profile. Furthermore, we show how commonly used analytic modelling methods such as static calculations of the pull-in voltage and dynamic modelling through an equivalent circuit representation can...

Unsteady boundary layer flow and heat transfer of a Casson fluid past an oscillating vertical plate with Newtonian heating.

Directory of Open Access Journals (Sweden)

Abid Hussanan

Full Text Available In this paper, the heat transfer effect on the unsteady boundary layer flow of a Casson fluid past an infinite oscillating vertical plate with Newtonian heating is investigated. The governing equations are transformed to a systems of linear partial differential equations using appropriate non-dimensional variables. The resulting equations are solved analytically by using the Laplace transform method and the expressions for velocity and temperature are obtained. They satisfy all imposed initial and boundary conditions and reduce to some well-known solutions for Newtonian fluids. Numerical results for velocity, temperature, skin friction and Nusselt number are shown in various graphs and discussed for embedded flow parameters. It is found that velocity decreases as Casson parameters increases and thermal boundary layer thickness increases with increasing Newtonian heating parameter.

Deformation of the Northwestern Okhotsk Plate: How is it happening?

Science.gov (United States)

Hindle, D.; Fujita, K.; Mackey, K.

2009-09-01

The Eurasia (EU) - North America (NA) plate boundary zone across Northeast Asia still presents many open questions within the plate tectonic paradigm. Constraining the geometry and number of plates or microplates present in the plate boundary zone is especially difficult because of the location of the EU-NA euler pole close to or even upon the EU-NA boundary. One of the major challenges remains the geometry of the Okhotsk plate (OK). whose northwestern portion terminates on the EU-OK-NA triple junction and is thus caught and compressed between converging EU and NA. We suggest that this leads to a coherent and understandable large scale deformation pattern of mostly northwest-southeast trending strike-slip faults which split Northwest OK into several extruding slivers. When the fault geometry is analysed together with space geodetic and focal mechanism data it suggests a central block which is extruding faster bordered east and west by progressively slower extruding blocks until the OK plate boundary faults are encountered. Taking into account elastic loading from both the intra-OK faults and the OK-Pacific (PA) boundary reconciles geodetic motions with geologic slip rates on at least the OK-NA boundary which corresponds to the Ulakhan fault.

The γ-ε martensitic transformation: a model for stress induced variant and its interaction with grain boundary

International Nuclear Information System (INIS)

Guenin, G.

1995-01-01

The γ (f.c.c.) to ε (h.c.p.) martensitic transformation occurs through the Shockley a/6 left angle 211 right angle faulting every second {111} plane of the f.c.c. structure. A stress induced thin single variant corresponds to a single a/6 left angle 211 right angle faulting vector and leads to a large homogeneous shear (0.35) in amplitude. The tip of such a plate is composed of a set of identical Shockley partial dislocations with large mutual interactions. This work is a presentation of a model which describes the martensite morphology of stress induced ε martensite in shape memory Fe-Mn-Si based alloys. The model includes the formation mechanism of the plate (Seeger's like) and its growth inside a limited grain. The mutual interaction of Shockley dislocations and their interaction with the grain boundary is semi quantitatively described; it leads to a lenticular shape of ε martensite thin plates. The model is able to explain the behaviour of this kind of alloys concerning the superelastic effect and the shape memory. (orig.)

Modeling dielectric half-wave plates for cosmic microwave background polarimetry using a Mueller matrix formalism.

Science.gov (United States)

Bryan, Sean A; Montroy, Thomas E; Ruhl, John E

2010-11-10

We derive an analytic formula using the Mueller matrix formalism that parameterizes the nonidealities of a half-wave plate (HWP) made from dielectric antireflection-coated birefringent slabs. This model accounts for frequency-dependent effects at normal incidence, including effects driven by the reflections at dielectric boundaries. The model also may be used to guide the characterization of an instrument that uses a HWP. We discuss the coupling of a HWP to different source spectra, and the potential impact of that effect on foreground removal for the SPIDER cosmic microwave background experiment. We also describe a way to use this model in a mapmaking algorithm that fully corrects for HWP nonidealities.

INCOMPRESSIBLE LAMINAR BOUNDARY LAYER CONTROL BY BLOWING AND SUCTION

OpenAIRE

AZZEDINE NAHOUI; LAKHDAR BAHI

2013-01-01

A two-dimensional incompressible laminar boundary layer and its control using blowing and suction over a flat plate and around the NACA 0012 and 661012 profiles, is studied numerically. The study is based on the Prandtl boundary layer model using the finite differences method and the Crank-Nicolson scheme. The velocity distribution, the boundary layer thickness and the friction coefficient, are determined and presented with and without control. The application of the control technique, has de...

Shear flow beneath oceanic plates: Local nonsimilarity boundary layers for olivine rheology

International Nuclear Information System (INIS)

Yuen, D.A.; Tovish, A.; Schubert, G.

1978-01-01

The principle of local similarity, which has been used to model the two-dimensional boundary layers in the oceanic upper mantle, permits calculation of the temperature, velocity, and stress fields with essentially analytic techniques. Finite difference numerical methods are hard pressed to resolve the detail required by the large variation of viscosity between the lithosphere and the asthenosphere. In this paper the local similarity approximation has been justified by quantitatively evaluating the effect of nonsimilarity due to viscous heating, nonlinear temperature- and pressure-dependent rheology, buoyancy, adiabatic cooling, etc. Nonsimilar effects produce only small modifications of the locally similar boundary layers; important geophysical observables such as surface heat flux and ocean floor topography are given to better than 10% by the locally similar solution. A posteriori evaluations of the term neglected in the boundary layer simplification of the complete equations have been conducted on the locally similar temperature and velocity profiles close to the spreading ridge. The boundary layer models are valid to depths of 100 km at 3 m.y. and 10 km at 0.3 m.y

The ultra low frequency electromagnetic radiation observed in the topside ionosphere above boundaries of tectonic plates

Directory of Open Access Journals (Sweden)

Michael A. Athanasiou

2015-01-01

Full Text Available In this paper we present results of a comparison between ultra low frequency (ULF electromagnetic (EM radiation, recorded by an electric field instrument onboard the satellite detection of electromagnetic emissions transmitted from earthquake regions in the topside ionosphere, and the seismicity of regions with high and low seismic activity. In particular, we evaluated the energy variations of the ULF Ezelectric field component during a period of four years (2006-2009, in order to examine the possible relation of ULF EM radiation with seismogenic regions located in Central America, Indonesia, the Eastern Mediterranean Basin and Greece. As a tool for evaluating the ULF Ez energy variations we used singular spectrum analysis techniques. The results of our analysis clearly show a significant increase of the ULF EM energy emitted from regions of highest seismic activity at the boundaries tectonic plates. Furthermore, we found that higher electromagnetic radiation was detected in a region above the northern- western Greek Arc (R1 than above the adjacent region including Athens and its urban area. We interpret these results of the present study as suggesting that: i the seismogenic regions at the boundary of tectonic plates radiate ULF EM emissions observed by satellites in the topside ionosphere; and ii that this EM radiation is not only related with the occurrence time of great (M≥5 earthquakes, but it is often present in intermediate times and it appears as a quasi-permanent phenomenon.

Modeling the hydrodynamics of phloem sieve plates

Directory of Open Access Journals (Sweden)

Kaare Hartvig Jensen

2012-07-01

Full Text Available Sieve plates have an enormous impact on the efficiency of the phloem vascular system of plants, responsible for the distribution of photosynthetic products. These thin plates, which separate neighboring phloem cells, are perforated by a large number of tiny sieve pores and are believed to play a crucial role in protecting the phloem sap from intruding animals by blocking flow when the phloem cell is damaged. The resistance to the flow of viscous sap in the phloem vascular system is strongly affected by the presence of the sieve plates, but the hydrodynamics of the flow through them remains poorly understood. We propose a theoretical model for quantifying the effect of sieve plates on the phloem in the plant, thus unifying and improving previous work in the field. Numerical simulations of the flow in real and idealized phloem channels verify our model, and anatomical data from 19 plant species are investigated. We find that the sieve plate resistance is correlated to the cell lumen resistance, and that the sieve plate and the lumen contribute almost equally to the total hydraulic resistance of the phloem translocation pathway.

Motion of the Rivera plate since 10 Ma relative to the Pacific and North American plates and the mantle

Science.gov (United States)

DeMets, Charles; Traylen, Stephen

2000-03-01

To better understand the influence of Rivera plate kinematics on the geodynamic evolution of western Mexico, we use more than 1400 crossings of seafloor spreading magnetic lineations along the Pacific-Rivera rise and northern Mathematician ridge to solve for rotations of the Rivera plate relative to the underlying mantle and the Pacific and North American plates at 14 times since 9.9 Ma. Our comparison of magnetic anomaly crossings from the undeformed Pacific plate to their counterparts on the Rivera plate indicates that significant areas of the Rivera plate have deformed since 9.9 Ma. Dextral shear along the southern edge of the plate from 3.3-2.2 Ma during a regional plate boundary reorganization deformed the Rivera plate farther into its interior than previously recognized. In addition, seafloor located north of two rupture zones within the Rivera plate sutured to North America after 1.5 Ma. Anomaly crossings from these two deformed regions thus cannot be used to reconstruct motion of the Rivera plate. Finite rotations that best reconstruct Pacific plate anomaly crossings onto their undeformed counterparts on the Rivera plate yield stage spreading rates that decrease gradually by 10% between 10 and 3.6 Ma, decrease rapidly by 20% after ˜3.6 Ma, and recover after 1 Ma. The slowdown in Pacific-Rivera seafloor spreading at 3.6 Ma coincided with the onset of dextral shear across the then-incipient southern boundary of the Rivera plate with the Pacific plate. The available evidence indicates that the Rivera plate has been an independent microplate since at least 10 Ma, contrary to published assertions that it fragmented from the Cocos plate at ˜5 Ma. Motion of the Rivera plate relative to North America has changed significantly since 10 Ma, in concert with significant changes in Pacific-Rivera motion. A significant and robust feature of Rivera-North America motion not previously recognized is the cessation of margin-normal convergence and thus subduction from 2

Dynamic Linkages Between the Transition Zone & Surface Plate Motions in 2D Models of Subduction

Science.gov (United States)

Arredondo, K.; Billen, M. I.

2013-12-01

While slab pull is considered the dominant force controlling plate motion and speed, its magnitude is controlled by slab behavior in the mantle, where tomographic studies show a wide range of possibilities from direct penetration to folding, or stagnation directly above the lower mantle (e.g. Fukao et al., 2009). Geodynamic studies have investigated various parameters, such as plate age and two phase transitions, to recreate observed behavior (e.g. Běhounková and Cízková, 2008). However, past geodynamic models have left out known slab characteristics that may have a large impact on slab behavior and our understanding of subduction processes. Mineral experiments and seismic observations have indicated the existence of additional phase transitions in the mantle transition zone that may produce buoyancy forces large enough to affect the descent of a subducting slab (e.g. Ricard et al., 2005). The current study systematically tests different common assumptions used in geodynamic models: kinematic versus free-slip boundary conditions, the effects of adiabatic heating, viscous dissipation and latent heat, compositional layering and a more complete suite of phase transitions. Final models have a complete energy equation, with eclogite, harzburgite and pyrolite lithosphere compositional layers, and seven composition-dependent phase transitions within the olivine, pyroxene and garnet polymorph minerals. Results show important feedback loops between different assumptions and new behavior from the most complete models. Kinematic models show slab weakening or breaking above the 660 km boundary and between compositional layers. The behavior in dynamic models with a free-moving trench and overriding plate is compared to the more commonly found kinematic models. The new behavior may have important implications for the depth distribution of deep earthquakes within the slab. Though the thermodynamic parameters of certain phase transitions may be uncertain, their presence and

Stretched flow of Carreau nanofluid with convective boundary ...

Indian Academy of Sciences (India)

journal of. January 2016 physics pp. 3–17. Stretched flow of Carreau nanofluid with ... fluid over a flat plate subjected to convective surface condition. ... the steady laminar boundary layer flow over a permeable plate with a convective boundary.

LARGE-EDDY SIMULATIONS OF A SEPARATION/REATTACHMENT BUBBLE IN A TURBULENT-BOUNDARY-LAYER SUBJECTED TO A PRESCRIBED UPPER-BOUNDARY, VERTICAL-VELOCITY PROFILE

KAUST Repository

Cheng, Wan; Pullin, D. I.; Samtaney, Ravi

2015-01-01

We describe large-eddy simulations of turbulent boundary-layer flow over a flat plate at high Reynolds number in the presence of an unsteady, three-dimensional flow separation/reattachment bubble. The stretched-vortex subgrid-scale model is used

DNS of heat transfer in transitional, accelerated boundary layer flow over a flat plate affected by free-stream fluctuations

International Nuclear Information System (INIS)

Wissink, Jan G.; Rodi, Wolfgang

2009-01-01

Direct numerical simulations (DNS) of flow over and heat transfer from a flat plate affected by free-stream fluctuations were performed. A contoured upper wall was employed to generate a favourable streamwise pressure gradient along a large portion of the flat plate. The free-stream fluctuations originated from a separate LES of isotropic turbulence in a box. In the laminar portions of the accelerating boundary layer flow the formation of streaks was observed to induce an increase in heat transfer by the exchange of hot fluid near the surface of the plate and cold fluid from the free-stream. In the regions where the streamwise pressure gradient was only mildly favourable, intermittent turbulent spots were detected which relaminarised downstream as the streamwise pressure gradient became stronger. The relaminarisation of the turbulent spots was reflected by a slight decrease in the friction coefficient, which converged to its laminar value in the region where the streamwise pressure gradient was strongest.

Repeating Deep Very Low Frequency Earthquakes: An Evidence of Transition Zone between Brittle and Ductile Zone along Plate Boundary

Science.gov (United States)

Ishihara, Y.; Yamamoto, Y.; Arai, R.

2017-12-01

Recently slow or low frequency seismic and geodetic events are focused under recognition of important role in tectonic process. The most western region of Ryukyu trench, Yaeyama Islands, is very active area of these type events. It has semiannual-like slow slip (Heki et.al., 2008; Nishimura et.al.,2014) and very frequent shallow very low frequency earthquakes near trench zone (Ando et.al.,2012; Nakamura et.al.,2014). Arai et.al.(2016) identified clear reverse phase discontinuity along plate boundary by air-gun survey, suggesting existence of low velocity layer including fluid. The subducting fluid layer is considered to control slip characteristics. On the other hand, deep low frequency earthquake and tremor observed at south-western Honshu and Shikoku of Japan are not identified well due to lack of high-quality seismic network. A broadband seismic station(ISG/PS) of Pacific21 network is operating in last 20 years that locates on occurrence potential area of low frequency earthquake. We tried to review continuous broadband record, searching low frequency earthquakes. In pilot survey, we found three very low frequency seismic events which are dominant in less than 0.1Hz component and are not listed in earthquake catalogue. Source locates about 50km depth and at transition area between slow slip event and active area of general earthquake along plate boundary. To detect small and/or hidden very low frequency earthquake, we applied matched filter analysis to continuous three components waveform data using pre-reviewed seismogram as template signal. 12 events with high correlation are picked up in last 10 years. Most events have very similar waveform, which means characteristics of repeating deep very low frequency earthquake. The event history of very low frequency earthquake is not related with one of slow slip event in this region. In Yaeyama region, low frequency earthquake, general earthquake and slow slip event occur dividing in space and have apparent

Plate Like Convection with Viscous Strain Weakening and Corresponding Surface Deformation Pattern

Science.gov (United States)

Fuchs, L.; Becker, T. W.

2017-12-01

How plate tectonic surface motions are generated by mantle convection on Earth and possibly other terrestrial type planets has recently become more readily accessible with fully dynamic convection computations. However, it remains debated how plate-like the behavior in such models truly is, and in particular how the well plate boundary dynamics are captured in models which typically exclude the effects of deformation history and memory. Here, we analyze some of the effects of viscous strain weakening on plate behavior and the interactions between interior convection dynamics and surface deformation patterns. We use the finite element code CitcomCU to model convection in a 3D Cartesian model setup. The models are internally heated, with an Arrhenius-type temperature dependent viscosity including plastic yielding and viscous strain weakening (VSW) and healing (VSWH). VSW can mimic first order features of more complex damage mechanisms such as grain-size dependent rheology. Besides plate diagnostic parameters (Plateness, Mobility, and Toroidal: Poloidal ratio) to analyze the tectonic behavior our models, we also explore how "plate boundaries" link to convective patterns. In a first model series, we analyze general surface deformation patterns without VSW. In the early stages, deformation patterns are clearly co-located with up- and downwelling limbs of convection. Along downwellings strain-rates are high and localized, whereas upwellings tend to lead to broad zones of high deformation. At a more advanced stage, however, the plates' interior is highly deformed due to continuous strain accumulation and resurfaced inherited strain. Including only VSW leads to more localized deformation along downwellings. However, at a more advanced stage plate-like convection fails due an overall weakening of the material. This is prevented including strain healing. Deformation pattern at the surface more closely coincide with the internal convection patterns. The average surface

Crustal Structure and Evolution of the Eastern Himalayan Plate Boundary System, Northeast India

Science.gov (United States)

Mitra, S.; Priestley, K. F.; Borah, Kajaljyoti; Gaur, V. K.

2018-01-01

We use data from 24 broadband seismographs located south of the Eastern Himalayan plate boundary system to investigate the crustal structure beneath Northeast India. P wave receiver function analysis reveals felsic continental crust beneath the Brahmaputra Valley, Shillong Plateau and Mikir Hills, and mafic thinned passive margin transitional crust (basement layer) beneath the Bengal Basin. Within the continental crust, the central Shillong Plateau and Mikir Hills have the thinnest crust (30 ± 2 km) with similar velocity structure, suggesting a unified origin and uplift history. North of the plateau and Mikir Hills the crustal thickness increases sharply by 8-10 km and is modeled by ˜30∘ north dipping Moho flexure. South of the plateau, across the ˜1 km topographic relief of the Dawki Fault, the crustal thickness increases abruptly by 12-13 km and is modeled by downfaulting of the plateau crust, overlain by 13-14 km thick sedimentary layer/rocks of the Bengal Basin. Farther south, beneath central Bengal Basin, the basement layer is thinner (20-22 km) and has higher Vs (˜4.1 km s-1) indicating a transitional crystalline crust, overlain by the thickest sedimentary layer/rocks (18-20 km). Our models suggest that the uplift of the Shillong Plateau occurred by thrust faulting on the reactivated Dawki Fault, a continent margin paleorift fault, and subsequent back thrusting on the south dipping Oldham Fault, in response to flexural loading of the Eastern Himalaya. Our estimated Dawki Fault offset combined with timing of surface uplift of the plateau reveals a reasonable match between long-term uplift and convergence rate across the Dawki Fault with present-day GPS velocities.

Logistical Support for the Installation of the Plate Boundary Observatory GPS and Borehole Strainmeter Networks

Science.gov (United States)

Kurnik, C.; Austin, K.; Coyle, B.; Dittmann, T.; Feaux, K.; Friesen, B.; Johnson, W.; Mencin, D.; Pauk, B.; Walls, C.

2007-12-01

The Plate Boundary Observatory (PBO), part of the NSF-funded EarthScope project, is designed to study the three- dimensional strain field resulting from deformation across the active boundary zone between the Pacific and North American plates in the western United States. To meet these goals, UNAVCO will install 880 continuous GPS stations, 103 borehole strainmeter stations, 28 tiltmeters, and five laser strainmeters by October 2008. Such a broad network presents significant logisitical challenges, including moving supplies, equipment, and personnel around 6 million square kilometers, and this requires accurate tracking and careful planning. The PBO logistics chain includes the PBO headquarters at UNAVCO in Boulder, Colorado and five regional offices in the continental United States and Alaska, served by dozens of suppliers spread across the globe. These offices are responsible for building and maintaining sites in their region. Most equipment and supplies first arrive in Boulder, where they are tagged and entered into a UNAVCO-wide equipment database, assembled and quality checked as necessary, and sent on to the appropriate regional office. Larger items which are costly to store and ship from Boulder, such as batteries or long sections of stainless steel pipe and bar required for monuments, are shipped directly from the supplier to each region as needed. These supplies and equipment are also tracked through the ordering, delivery, installation, and maintenance cycle via Earned Value Management techniques which allow us to meet NSF and other Federal procurement rules. Early prototypes and assembly configurations aid the development of material and supply budgets. A thorough understanding of Federal procurement rules at project start up is critical as the project moves forward.

The San Andreas fault experiment. [gross tectonic plates relative velocity

Science.gov (United States)

Smith, D. E.; Vonbun, F. O.

1973-01-01

A plan was developed during 1971 to determine gross tectonic plate motions along the San Andreas Fault System in California. Knowledge of the gross motion along the total fault system is an essential component in the construction of realistic deformation models of fault regions. Such mathematical models will be used in the future for studies which will eventually lead to prediction of major earthquakes. The main purpose of the experiment described is the determination of the relative velocity of the North American and the Pacific Plates. This motion being so extremely small, cannot be measured directly but can be deduced from distance measurements between points on opposite sites of the plate boundary taken over a number of years.

Anisotropic elastic plates

CERN Document Server

Hwu, Chyanbin

2010-01-01

As structural elements, anisotropic elastic plates find wide applications in modern technology. The plates here are considered to be subjected to not only in plane load but also transverse load. In other words, both plane and plate bending problems as well as the stretching-bending coupling problems are all explained in this book. In addition to the introduction of the theory of anisotropic elasticity, several important subjects have are discussed in this book such as interfaces, cracks, holes, inclusions, contact problems, piezoelectric materials, thermoelastic problems and boundary element a

Modeling the hydrodynamics of Phloem sieve plates

DEFF Research Database (Denmark)

Jensen, Kaare Hartvig; Mullendore, Daniel Leroy; Holbrook, Noel Michele

2012-01-01

Sieve plates have an enormous impact on the efficiency of the phloem vascular system of plants, responsible for the distribution of photosynthetic products. These thin plates, which separate neighboring phloem cells, are perforated by a large number of tiny sieve pores and are believed to play...... understood. We propose a theoretical model for quantifying the effect of sieve plates on the phloem in the plant, thus unifying and improving previous work in the field. Numerical simulations of the flow in real and idealized phloem channels verify our model, and anatomical data from 19 plant species...... a crucial role in protecting the phloem sap from intruding animals by blocking flow when the phloem cell is damaged. The resistance to the flow of viscous sap in the phloem vascular system is strongly affected by the presence of the sieve plates, but the hydrodynamics of the flow through them remains poorly...

Model-based estimation with boundary side information or boundary regularization [cardiac emission CT].

Science.gov (United States)

Chiao, P C; Rogers, W L; Fessler, J A; Clinthorne, N H; Hero, A O

1994-01-01

The authors have previously developed a model-based strategy for joint estimation of myocardial perfusion and boundaries using ECT (emission computed tomography). They have also reported difficulties with boundary estimation in low contrast and low count rate situations. Here they propose using boundary side information (obtainable from high resolution MRI and CT images) or boundary regularization to improve both perfusion and boundary estimation in these situations. To fuse boundary side information into the emission measurements, the authors formulate a joint log-likelihood function to include auxiliary boundary measurements as well as ECT projection measurements. In addition, they introduce registration parameters to align auxiliary boundary measurements with ECT measurements and jointly estimate these parameters with other parameters of interest from the composite measurements. In simulated PET O-15 water myocardial perfusion studies using a simplified model, the authors show that the joint estimation improves perfusion estimation performance and gives boundary alignment accuracy of <0.5 mm even at 0.2 million counts. They implement boundary regularization through formulating a penalized log-likelihood function. They also demonstrate in simulations that simultaneous regularization of the epicardial boundary and myocardial thickness gives comparable perfusion estimation accuracy with the use of boundary side information.

Influence of electrical boundary conditions on profiles of acoustic field and electric potential of shear-horizontal acoustic waves in potassium niobate plates.

Science.gov (United States)

Kuznetsova, I E; Nedospasov, I A; Kolesov, V V; Qian, Z; Wang, B; Zhu, F

2018-05-01

The profiles of an acoustic field and electric potential of the forward and backward shear-horizontal (SH) acoustic waves of a higher order propagating in X-Y potassium niobate plate have been theoretically investigated. It has been shown that by changing electrical boundary conditions on a surface of piezoelectric plates, it is possible to change the distributions of an acoustic field and electric potential of the forward and backward acoustic waves. The dependencies of the distribution of a mechanical displacement and electrical potential over the plate thickness for electrically open and electrically shorted plates have been plotted. The influence of a layer with arbitrary conductivity placed on a one or on the both plate surfaces on the profiles under study, phase and group velocities of the forward and backward acoustic waves in X-Y potassium niobate has been also investigated. The obtained results can be useful for development of the method for control of a particle or electrical charge movement inside the piezoelectric plates, as well a sensor for definition of the thin film conductivity. Copyright © 2018 Elsevier B.V. All rights reserved.

Design of a Scaled Model for Experimental Flowfield Studies of Louvered Plate Fins.

Science.gov (United States)

Springer, Marlow E.; Thole, Karen A.

1997-11-01

The optimization of compact heat exchangers maximizing heat transfer while minimizing pressure drop is important for many industrial applications. Because the dominant thermal resistance for most air-and-water or air-and-oil heat exchangers occurs on the air side, an understanding of the flowfield on the air side is needed to further optimize the heat exchanger. Louvered plate fin heat exchangers are used not only to increase the convective heat transfer surface area, but also to initiate the growth of multiple boundary layers. There is also evidence that vortex shedding occurs from the trailing edge of the louvers, which would increase heat transfer. Computational fluid dynamics models have been used to design a scaled up model of a louvered plate fin geometry representative of what would occur in a compact heat exchanger. The current model has a louver angle of 27^circ and a louver-to-fin pitch ratio of 1.31. The same technique can be used to design models for other geometries. Critical issues in the design include endwall spacings to maintain a straight inlet flow, and the required number of louver rows to capture the periodic nature of a heat exchanger with perhaps hundreds of rows. Within the louver passages, measurements of mean and time-resolved velocities to characterize the mean flowfield and vortex shedding have been obtained using laser Doppler velocimetry.

MHD Heat and Mass Transfer of Chemical Reaction Fluid Flow over a Moving Vertical Plate in Presence of Heat Source with Convective Surface Boundary Condition

Directory of Open Access Journals (Sweden)

B. R. Rout

2013-01-01

Full Text Available This paper aims to investigate the influence of chemical reaction and the combined effects of internal heat generation and a convective boundary condition on the laminar boundary layer MHD heat and mass transfer flow over a moving vertical flat plate. The lower surface of the plate is in contact with a hot fluid while the stream of cold fluid flows over the upper surface with heat source and chemical reaction. The basic equations governing the flow, heat transfer, and concentration are reduced to a set of ordinary differential equations by using appropriate transformation for variables and solved numerically by Runge-Kutta fourth-order integration scheme in association with shooting method. The effects of physical parameters on the velocity, temperature, and concentration profiles are illustrated graphically. A table recording the values of skin friction, heat transfer, and mass transfer at the plate is also presented. The discussion focuses on the physical interpretation of the results as well as their comparison with previous studies which shows good agreement as a special case of the problem.

Three dimensional grain boundary modeling in polycrystalline plasticity

Science.gov (United States)

Yalçinkaya, Tuncay; Özdemir, Izzet; Fırat, Ali Osman

2018-05-01

At grain scale, polycrystalline materials develop heterogeneous plastic deformation fields, localizations and stress concentrations due to variation of grain orientations, geometries and defects. Development of inter-granular stresses due to misorientation are crucial for a range of grain boundary (GB) related failure mechanisms, such as stress corrosion cracking (SCC) and fatigue cracking. Local crystal plasticity finite element modelling of polycrystalline metals at micron scale results in stress jumps at the grain boundaries. Moreover, the concepts such as the transmission of dislocations between grains and strength of the grain boundaries are not included in the modelling. The higher order strain gradient crystal plasticity modelling approaches offer the possibility of defining grain boundary conditions. However, these conditions are mostly not dependent on misorientation of grains and can define only extreme cases. For a proper definition of grain boundary behavior in plasticity, a model for grain boundary behavior should be incorporated into the plasticity framework. In this context, a particular grain boundary model ([l]) is incorporated into a strain gradient crystal plasticity framework ([2]). In a 3-D setting, both bulk and grain boundary models are implemented as user-defined elements in Abaqus. The strain gradient crystal plasticity model works in the bulk elements and considers displacements and plastic slips as degree of freedoms. Interface elements model the plastic slip behavior, yet they do not possess any kind of mechanical cohesive behavior. The physical aspects of grain boundaries and the performance of the model are addressed through numerical examples.

A numerical investigation of turbulent flow in an 18-plate nuclear fuel assembly

International Nuclear Information System (INIS)

Yu, R.; Lightstone, M.F.

2003-01-01

A numerical simulation of the fluid flow in the core of the McMaster Nuclear Reactor (MNR) was performed. The standard k - ε turbulence model together with a two-layer wall boundary model was used in the current study. A two-dimensional numerical model for the MNR 18-plate nuclear fuel assembly was developed using the advanced commercial computational fluid dynamics (CFD) code CFX-TASCflow. The numerical predictions were compared with experimental data for the MNR 18-plate assembly at the same flow conditions. In general, the code over predicts the pressure drop for the range of the mass flow rate investigated, however, the difference decreases as the mass flow rate (or Reynolds number) increases. Errors of less than 4% were obtained for mass flows greater than 4.0 kg/s. The comparison shows that the predicted flow distribution and velocities are very close to the measured data for the high Reynolds number flows. It is found that the k - ε model with the two-layer wall boundary model can predict the flow in the vertical parallel plate channels in the low Reynolds number region (Re=3000 to 10,000) very well. (author)

Effect of matrix cracking and material uncertainty on composite plates

International Nuclear Information System (INIS)

Gayathri, P.; Umesh, K.; Ganguli, R.

2010-01-01

A laminated composite plate model based on first order shear deformation theory is implemented using the finite element method. Matrix cracks are introduced into the finite element model by considering changes in the A, B and D matrices of composites. The effects of different boundary conditions, laminate types and ply angles on the behavior of composite plates with matrix cracks are studied. Finally, the effect of material property uncertainty, which is important for composite material on the composite plate, is investigated using Monte Carlo simulations. Probabilistic estimates of damage detection reliability in composite plates are made for static and dynamic measurements. It is found that the effect of uncertainty must be considered for accurate damage detection in composite structures. The estimates of variance obtained for observable system properties due to uncertainty can be used for developing more robust damage detection algorithms.

Dual Solutions in a Boundary Layer Flow of a Power Law Fluid over a Moving Permeable Flat Plate with Thermal Radiation, Viscous Dissipation and Heat Generation/Absorption

Directory of Open Access Journals (Sweden)

Aftab Ahmed

2018-01-01

Full Text Available The aim of the present study is to investigate the combined effects of the thermal radiation, viscous dissipation, suction/injection and internal heat generation/absorption on the boundary layer flow of a non-Newtonian power law fluid over a semi infinite permeable flat plate moving in parallel or reversely to a free stream. The resulting system of partial differential equations (PDEs is first transformed into a system of coupled nonlinear ordinary differential equations (ODEs which are then solved numerically by using the shooting technique. It is found that the dual solutions exist when the flat plate and the free stream move in the opposite directions. Dimensionless boundary layer velocity and temperature distributions are plotted and discussed for various values of the emerging physical parameters. Finally, the tables of the relevant boundary derivatives are presented for some values of the governing physical parameters.

DYNAMIC SURFACE BOUNDARY-CONDITIONS - A SIMPLE BOUNDARY MODEL FOR MOLECULAR-DYNAMICS SIMULATIONS

NARCIS (Netherlands)

JUFFER, AH; BERENDSEN, HJC

1993-01-01

A simple model for the treatment of boundaries in molecular dynamics simulations is presented. The method involves the positioning of boundary atoms on a surface that surrounds a system of interest. The boundary atoms interact with the inner region and represent the effect of atoms outside the

Modeling of plates with multiple anisotropic layers and residual stress

DEFF Research Database (Denmark)

Engholm, Mathias; Pedersen, Thomas; Thomsen, Erik Vilain

2016-01-01

Usually the analytical approach for modeling of plates uses the single layer plate equation to obtain the deflection and does not take anisotropy and residual stress into account. Based on the stress–strain relation of each layer and balancing stress resultants and bending moments, a general...... multilayered anisotropic plate equation is developed for plates with an arbitrary number of layers. The exact deflection profile is calculated for a circular clamped plate of anisotropic materials with residual bi-axial stress.From the deflection shape the critical stress for buckling is calculated......, and an excellent agreement between the two models is seen with a relative difference of less than 2% for all calculations. The model was also used to extract the cell capacitance, the parasitic capacitance and the residual stress of a pressure sensor composed of a multilayered plate of silicon and silicon oxide...

Prediction of interior noise due to random acoustic or turbulent boundary layer excitation using statistical energy analysis

Science.gov (United States)

Grosveld, Ferdinand W.

1990-01-01

The feasibility of predicting interior noise due to random acoustic or turbulent boundary layer excitation was investigated in experiments in which a statistical energy analysis model (VAPEPS) was used to analyze measurements of the acceleration response and sound transmission of flat aluminum, lucite, and graphite/epoxy plates exposed to random acoustic or turbulent boundary layer excitation. The noise reduction of the plate, when backed by a shallow cavity and excited by a turbulent boundary layer, was predicted using a simplified theory based on the assumption of adiabatic compression of the fluid in the cavity. The predicted plate acceleration response was used as input in the noise reduction prediction. Reasonable agreement was found between the predictions and the measured noise reduction in the frequency range 315-1000 Hz.

Analytical Study on the Flexural Behavior of Reinforced Concrete Beams Strengthened with Prestressed Carbon Fiber-Reinforced Polymer Plates

International Nuclear Information System (INIS)

Woo, S. K.; Song, Y. C.; Lee, H. P.; Byun, K. J.

2007-01-01

This study aims to predict the behavior of concrete structures strengthened with prestressed CFRP plates with more reliability, and then develop a nonlinear structural analysis model that can be applied more effectively in reinforcement designs, after examining the behavior characteristics of CFRP plates and epoxy, and the behavior of the boundary layer between CFRP plates and concrete

Introduction to Plate Boundaries and Natural Hazards

NARCIS (Netherlands)

Duarte, João C.; Schellart, Wouter P.

2016-01-01

A great variety of natural hazards occur on Earth, including earthquakes, volcanic eruptions, tsunamis, landslides, floods, fires, tornadoes, hurricanes, and avalanches. The most destructive of these hazards, earthquakes, tsunamis, and volcanic eruptions, are mostly associated with tectonic plate

Relative motions of the Australian, Pacific and Antarctic plates estimated by the Global Positioning System

Science.gov (United States)

Larson, Kristine M.; Freymueller, Jeff

1995-01-01

Global Positioning System (GPS) measurements spanning approximately 3 years have been used to determine velocities for 7 sites on the Australian, Pacific and Antarctic plates. The site velocities agree with both plate model predictions and other space geodetic techniques. We find no evidence for internal deformation of the interior of the Australian plate. Wellington, New Zealand, located in the Australian-Pacific plate boundary zone, moves 20 +/- 5 mm/yr west-southwest relative to the Australian plate. Its velocity lies midway between the predicted velocities of the two plates. Relative Euler vectors for the Australia-Antarctica and Pacific-Antarctica plates agree within one standard deviation with the NUVEL-1A predictions.

Dynamical Casimir effect on a cavity with mixed boundary conditions

International Nuclear Information System (INIS)

Alves, Danilo T.; Farina, Carlos; Maia Neto, Paulo Americo

2002-01-01

The most well-known mechanical effect related to the quantum vacuum is the Casimir force between two mirrors at rest. A new effect appears when the mirrors are set to move. In this case, the vacuum field may exert a dissipative force, damping the motion. As a consequence of energy conservation, there will be creation of real particles. If the motion is non-relativistic and has a small amplitude, the dynamical Casimir force can be found via a perturbative method proposed by Ford and Vilenkin. Using their technique, the electromagnetic dynamical Casimir problem, considered when the oscillating cavity is formed by two parallel plates of the same nature (perfectly conducting or perfectly permeable), can be divided into two separated boundary condition problems, namely: one involving Dirichlet BC, related to the transverse electric polarization and the other involving a Neumann BC, related to the transverse magnetic mode. The case of conducting plates can be found in the literature. However, another interesting case, the mixed oscillating cavity where the plates are of different nature, namely, a perfectly conducting plate and a perfectly permeable one (Boyer plates), has not been studied yet. We show that,for this case, the transverse electric models will be related to mixed boundary conditions: Dirichlet-like BC at the conducting plate and Neumann-like BC at the permeable plate. Analogously, the magnetic modes are related to a Neumann BC at the conducting plate and to a Dirichlet BC at the permeable one. As a first step before attacking the three-dimensional electromagnetic problem with mixed BC, we present here a simpler model: a one-dimensional cavity, where a massless scalar field is submitted to mixed (Dirichlet-Neumann) BC. For simplicity, we consider a non-relativistic motion for the conducting wall (Dirichlet BC) and suppose that the perfectly permeable wall (Neumann BC) is at rest. From this model we can extract insights about the dynamical Casimir

Free Vibration Study of Anti-Symmetric Angle-Ply Laminated Plates under Clamped Boundary Conditions

Science.gov (United States)

Viswanathan, K. K.; Karthik, K.; Sanyasiraju, Y. V. S. S.; Aziz, Z. A.

2016-11-01

Two type of numerical approach namely, Radial Basis Function and Spline approximation, used to analyse the free vibration of anti-symmetric angle-ply laminated plates under clamped boundary conditions. The equations of motion are derived using YNS theory under first order shear deformation. By assuming the solution in separable form, coupled differential equations obtained in term of mid-plane displacement and rotational functions. The coupled differential is then approximated using Spline function and radial basis function to obtain the generalize eigenvalue problem and parametric studies are made to investigate the effect of aspect ratio, length-to-thickness ratio, number of layers, fibre orientation and material properties with respect to the frequency parameter. Some results are compared with the existing literature and other new results are given in tables and graphs.

Fission gas behaviour modelling in plate fuel during a power transient

International Nuclear Information System (INIS)

Portier, S.

2003-01-01

This thesis is dedicated to the identification and modelization of the phenomena which are at the origin of the release of the fission gas formed in UO 2 plate fuels during the irradiation in a power transient. In the first experimental part, samples of plate fuels, irradiated at 36 GWj/tU, have been annealed to temperatures from 1100 C to 1500 C in a device that enabled the measurement of gas release in real time. At 1300 C, post-annealing observations demonstrated a link between the measured gas releases to a rapid formation of labyrinths at the grain surface. These labyrinths, which were formed by intergranular bubble interconnection, create release paths for the gas atoms which reach the grain surface. At this stage, the available experimental results (annealing and observations) were interpreted considering that it is the spreading of the gas atoms from the grains to the grain boundaries that is at the origin of the observed releases. This interpretation generates the hypothesis that a) at the end of the basic irradiation, the gas is at the atomic state and b) during the annealing, the spreading is reduced by the intragranular bubbles of the gas atoms. The last part of the work is dedicated to the modelization of the main phenomena at the origin of the gas release. The model developed, based on the model of the gas behaviour in MARGARET PWR, highlighted the great influence of the irradiation conditions on the gas distribution at the end of the irradiation and also its influence on the fission gas release during the power transient. (author) [fr

Tokamak plasma boundary layer model

International Nuclear Information System (INIS)

Volkov, T.F.; Kirillov, V.D.

1983-01-01

A model has been developed for the limiter layer and for the boundary region of the plasma column in a tokamak to facilitate analytic calculations of the thickness of the limiter layers, the profiles and boundary values of the temperature and the density under various conditions, and the difference between the electron and ion temperatures. This model can also be used to analyze the recycling of neutrals, the energy and particle losses to the wall and the limiter, and other characteristics

Numerical Investigation of an Oscillating Flat Plate Airfoil

Science.gov (United States)

Mohaghegh, Fazlolah; Janechek, Matthew; Buchholz, James; Udaykumar, Hs

2017-11-01

This research investigates the vortex dynamics of a plunging flat plate airfoil by analyzing the vorticity transport in 2D simulations. A horizontal airfoil is subject to a freestream flow at Re =10000. A prescribed vertical sinusoidal motion is applied to the airfoil. Smoothed Profile Method (SPM) models the fluid-structure interaction. SPM as a diffuse interface model considers a thickness for the interface and applies a smooth transition from solid to fluid. As the forces on the airfoil are highly affected by the interaction of the generated vortices from the surface, it is very important to find out whether a diffuse interface solver can model a flow dominated by vorticities. The results show that variation of lift coefficient with time agrees well with the experiment. Study of vortex evolution shows that similar to experiments, when the plate starts moving downward from top, the boundary layer is attached to the surface and the leading-edge vortex (LEV) is very small. By time, LEV grows and rolls up and a secondary vortex emerges. Meanwhile, the boundary layer starts to separate and finally LEV detaches from the surface. In overall, SPM as a diffuse interface model can predict the lift force and vortex pattern accurately.

Barrel organ of plate tectonics - a new tool for outreach and education

Science.gov (United States)

Broz, Petr; Machek, Matěj; Šorm, Zdar

2016-04-01

Plate tectonics is the major geological concept to explain dynamics and structure of Earth's outer shell, the lithosphere. In the plate tectonic theory processes in the Earth lithosphere and its dynamics is driven by the relative motion and interaction of lithospheric plates. Geologically most active regions on Earth often correlate with the lithospheric plate boundaries. Thus for explaining the earth surface evolution, mountain building, volcanism and earthquake origin it is important to understand processes at the plate boundaries. However these processes associated with plate tectonics usually require significant period of time to take effects, therefore, their entire cycles cannot be directly observed in the nature by humans. This makes a challenge for scientists studying these processes, but also for teachers and popularizers trying to explain them to students and to the general public. Therefore, to overcome this problem, we developed a mechanical model of plate tectonics enabling demonstration of most important processes associated with plate tectonics in real time. The mechanical model is a wooden box, more specifically a special type of barrel organ, with hand painted backdrops in the front side. These backdrops are divided into several components representing geodynamic processes associated with plate tectonics, specifically convective currents occurring in the mantle, sea-floor spreading, a subduction of the oceanic crust under the continental crust, partial melting and volcanism associated with subduction, a formation of magmatic stripes, an ascent of mantle plume throughout the mantle, a volcanic activity associated with hot spots, and a formation and degradation of volcanic islands on moving lithospheric plate. All components are set in motion by a handle controlled by a human operator, and the scene is illuminated with colored lights controlled automatically by an electric device embedded in the box. Operation of the model may be seen on www

Mathematical modeling of impact of two metal plates using two-fluid approach

Science.gov (United States)

Utkin, P. S.; Fortova, S. V.

2018-01-01

The paper is devoted to the development of the two-fluid mathematical model and the computational algorithm for the modeling of two metal plates impact. In one-dimensional case the governing system of equations comprises seven equations: three conservation laws for each fluid and transfer equation for the volume fraction of one of the fluids. Both fluids are considered to be compressible and equilibrium on velocities. Pressures equilibrium is used as fluids interface condition. The system has hyperbolic type but could not be written in the conservative form because of nozzling terms in the right-hand side of the equations. The algorithm is based on the Harten-Lax-van Leer numerical flux function. The robust computation in the presence of the interface boundary is carried out due to the special pressure relaxation procedure. The problem is solved using stiffened gas equations of state for each fluid. The parameters in the equations of state are calibrated using the results of computations using wide-range equations of state for the metals. In simulations of metal plates impact we get two shocks after the initial impact that propagate to the free surfaces of the samples. The characteristics of shock waves are close (maximum relative error in characteristics of shocks is not greater than 7%) to the data from the wide-range equations of states computations.

Tricritical Ising model with a boundary

International Nuclear Information System (INIS)

De Martino, A.; Moriconi, M.

1998-03-01

We study the integrable and supersymmetric massive φ (1,3) deformation of the tricritical Ising model in the presence of a boundary. We use constraints from supersymmetry in order to compute the exact boundary S-matrices, which turn out to depend explicitly on the topological charge of the supersymmetry algebra. We also solve the general boundary Yang-Baxter equation and show that in appropriate limits the general reflection matrices go over the supersymmetry preserving solutions. Finally, we briefly discuss the possible connection between our reflection matrices and boundary perturbations within the framework of perturbed boundary conformal field theory. (author)

LARGE-EDDY SIMULATIONS OF A SEPARATION/REATTACHMENT BUBBLE IN A TURBULENT-BOUNDARY-LAYER SUBJECTED TO A PRESCRIBED UPPER-BOUNDARY, VERTICAL-VELOCITY PROFILE

KAUST Repository

Cheng, Wan

2015-06-30

We describe large-eddy simulations of turbulent boundary-layer flow over a flat plate at high Reynolds number in the presence of an unsteady, three-dimensional flow separation/reattachment bubble. The stretched-vortex subgrid-scale model is used in the main flow domain combined with a wall-model that is a two-dimensional extension of that developed by Chung & Pullin (2009). Flow separation and re-attachment of the incoming boundary layer is induced by prescribing wall-normal velocity distribution on the upper boundary of the flow domain that produces an adverse-favorable stream-wise pressure distribution at the wall. The LES predicts the distribution of mean shear stress along the wall including the interior of the separation bubble. Several properties of the separation/reattachment flow are discussed.

Modeling and analysis of waves in a heat conducting thermo-elastic plate of elliptical shape

Directory of Open Access Journals (Sweden)

R. Selvamani

Full Text Available Wave propagation in heat conducting thermo elastic plate of elliptical cross-section is studied using the Fourier expansion collocation method based on Suhubi's generalized theory. The equations of motion based on two-dimensional theory of elasticity is applied under the plane strain assumption of generalized thermo elastic plate of elliptical cross-sections composed of homogeneous isotropic material. The frequency equations are obtained by using the boundary conditions along outer and inner surface of elliptical cross-sectional plate using Fourier expansion collocation method. The computed non-dimensional frequency, velocity and quality factor are plotted in dispersion curves for longitudinal and flexural (symmetric and antisymmetric modes of vibrations.

Predictions of the effect of stratification on superimposed forced and free convection between vertical parallel plates for various boundary conditions

International Nuclear Information System (INIS)

Cowan, G.H.; Irvine, T.J. Jr.; Quarini, G.L.

1983-01-01

The velocity and temperature equations for laminar buoyancy and forced convection flows between vertical flat parallel plates are presented. The thermal boundary conditions on the plate define the buoyancy driven field, while the channel Reynolds number defines the forced flow field. Specific examples relating to tall narrow channels with laminar convention and to closed high ratio cavities (as may be found in the proposed active and passive insulation systems for sodium cooled fast reactors) are presented. The analysis is limited to the laminar flow regimes, whilst some reactor situations are likely to be turbulent, hence a proposal for a simple extension of this analysis to the turbulent regime is made. It is shown how the analysis can be made to apply to fluids of various Prandtl numbers. (author)

The Fairway-Aotea Basin and the New Caledonia Trough, witnesses of the Pacific-Australian plate boundary evolution : from mid-Cretaceous cessation of subduction to Eocene subduction renewal

Science.gov (United States)

Collot, J.; Geli, L. B.; Lafoy, Y.; Sutherland, R.; Herzer, R. H.; Roest, W. R.

2009-12-01

The geodynamical history of the SW Pacific is controlled since the Mesozoic by the evolution of peri-Pacific subduction zones, in a trench retreat by slab roll-back process, which successively occurred along the Eastern Gondwana margin. In this context, most basins which formed after 45 Ma reached a stage of seafloor spreading, have recorded the inversions of the earth's magnetic field and present typical oceanic crust morphologies. By contrast, the New Caledonia and Fairway basins, which are narrower and present thick sedimentary covers have a less known and more controversial origin. Based on a regional geological synthesis and on interpretation of multichannel seismic reflection and refraction data, combined with drill hole data off New Zealand and a compilation of regional potential data, we distinguish 2 phases of the evolution of the Fairway-Aotea Basin (FAB) and the New Caledonia Trough (NCT), which reflect the evolution of the Gondwana-Pacific plate boundary: Phase 1: Mid Cretaceous formation of the FAB in a continental intra- or back- arc position of the Pacific-Gondwana subduction system. The formation of this shallow basin reflects the onset of continental breakup of the Eastern Gondwana margin during Cenomanian which was most probably caused by a dynamic change of the subduction zone through a « verticalization » of the slab. This event may be the result of the 99 Ma kinematic plate reorganization which probably led to subduction cessation along the Gondwana-Pacific plate boundary. A tectonic escape mechanism, in relation with the locking of the subduction zone by the Hikurangi Plateau, could also be responsible of the trench retreat leading to backarc extension. Phase 2: Regional Eocene-Oligocene uplift followed by rapid subsidence (3-4 km) of the system « Lord Howe Rise - FAB - Norfolk Ridge ». The structural style of this deformation leads us to suggest that detachment of the lower crust is the cause of subsidence. We therefore propose a model in

Three-dimensional model of plate geometry and velocity model for Nankai Trough seismogenic zone based on results from structural studies

Science.gov (United States)

Nakanishi, A.; Shimomura, N.; Kodaira, S.; Obana, K.; Takahashi, T.; Yamamoto, Y.; Yamashita, M.; Takahashi, N.; Kaneda, Y.

2012-12-01

In the Nankai Trough subduction seismogenic zone, the Nankai and Tonankai earthquakes had often occurred simultaneously, and caused a great event. In order to reduce a great deal of damage to coastal area from both strong ground motion and tsunami generation, it is necessary to understand rupture synchronization and segmentation of the Nankai megathrust earthquake. For a precise estimate of the rupture zone of the Nankai megathrust event based on the knowledge of realistic earthquake cycle and variation of magnitude, it is important to know the geometry and property of the plate boundary of the subduction seismogenic zone. To improve a physical model of the Nankai Trough seismogenic zone, the large-scale high-resolution wide-angle and reflection (MCS) seismic study, and long-term observation has been conducted since 2008. Marine active source seismic data have been acquired along grid two-dimensional profiles having the total length of ~800km every year. A three-dimensional seismic tomography using active and passive seismic data observed both land and ocean bottom stations have been also performed. From those data, we found that several strong lateral variations of the subducting Philippine Sea plate and overriding plate corresponding to margins of coseismic rupture zone of historical large event occurred along the Nankai Trough. Particularly a possible prominent reflector for the forearc Moho is recently imaged in the offshore side in the Kii channel at the depth of ~18km which is shallower than those of other area along the Nankai Trough. Such a drastic variation of the overriding plate might be related to the existence of the segmentation of the Nankai megathrust earthquake. Based on our results derived from seismic studies, we have tried to make a geometrical model of the Philippine Sea plate and a three-dimensional velocity structure model of the Nankai Trough seismogenic zone. In this presentation, we will summarize major results of out seismic studies, and

Modeling the summertime Arctic cloudy boundary layer

Energy Technology Data Exchange (ETDEWEB)

Curry, J.A.; Pinto, J.O. [Univ. of Colorado, Boulder, CO (United States); McInnes, K.L. [CSIRO Division of Atmospheric Research, Mordialloc (Australia)

1996-04-01

Global climate models have particular difficulty in simulating the low-level clouds during the Arctic summer. Model problems are exacerbated in the polar regions by the complicated vertical structure of the Arctic boundary layer. The presence of multiple cloud layers, a humidity inversion above cloud top, and vertical fluxes in the cloud that are decoupled from the surface fluxes, identified in Curry et al. (1988), suggest that models containing sophisticated physical parameterizations would be required to accurately model this region. Accurate modeling of the vertical structure of multiple cloud layers in climate models is important for determination of the surface radiative fluxes. This study focuses on the problem of modeling the layered structure of the Arctic summertime boundary-layer clouds and in particular, the representation of the more complex boundary layer type consisting of a stable foggy surface layer surmounted by a cloud-topped mixed layer. A hierarchical modeling/diagnosis approach is used. A case study from the summertime Arctic Stratus Experiment is examined. A high-resolution, one-dimensional model of turbulence and radiation is tested against the observations and is then used in sensitivity studies to infer the optimal conditions for maintaining two separate layers in the Arctic summertime boundary layer. A three-dimensional mesoscale atmospheric model is then used to simulate the interaction of this cloud deck with the large-scale atmospheric dynamics. An assessment of the improvements needed to the parameterizations of the boundary layer, cloud microphysics, and radiation in the 3-D model is made.

Vortex Shedding Characteristics of the Wake of a Thin Flat Plate with a Circular Trailing Edge

Science.gov (United States)

Rai, Man Mohan

2018-01-01

The near and very near wake of a thin flat plate with a circular trailing edge are investigated with direct numerical simulations (DNS). Data obtained for two different Reynolds numbers (based on plate thickness, D) are the main focus of this study. The separating boundary layers are turbulent in both cases. An earlier investigation of one of the cases (Case F) showed shed vortices in the wake that were about 1.0 D to 4.0 D in spanwise length. Considerable variation in both the strength and frequency of these shed vortices was observed. One objective of the present investigation is to determine the important contributors to this variability in strength and frequency of shed vortices and their finite spanwise extent. Analysis of the data shows that streamwise vortices in the separating boundary layer play an important role in strengthening/weakening of the shed vortices and that high/low-speed streaks in the boundary layer are important contributors to variability in shedding frequency. Both these features of the boundary layer contribute to the finite extent of the vortices in the spanwise direction. The second plate DNS (Case G, with 40 percent of the plate thickness of Case F) shows that while shedding intensity is weaker than obtained in Case F, many of the wake features are similar to that of Case F. This is important in understanding the path to the wake of the thin plate with a sharp trailing edge where shedding is absent. Here we also test the efficacy of a functional relationship between the shedding frequency and the Reynolds numbers based on the boundary layer momentum thickness (Re (sub theta) and D (Re (sub D)); data for developing this behavioral model is from Cases F & G and five earlier DNSs of the flat plate wake.

Non-linear analysis of wave progagation using transform methods and plates and shells using integral equations

Science.gov (United States)

Pipkins, Daniel Scott

Two diverse topics of relevance in modern computational mechanics are treated. The first involves the modeling of linear and non-linear wave propagation in flexible, lattice structures. The technique used combines the Laplace Transform with the Finite Element Method (FEM). The procedure is to transform the governing differential equations and boundary conditions into the transform domain where the FEM formulation is carried out. For linear problems, the transformed differential equations can be solved exactly, hence the method is exact. As a result, each member of the lattice structure is modeled using only one element. In the non-linear problem, the method is no longer exact. The approximation introduced is a spatial discretization of the transformed non-linear terms. The non-linear terms are represented in the transform domain by making use of the complex convolution theorem. A weak formulation of the resulting transformed non-linear equations yields a set of element level matrix equations. The trial and test functions used in the weak formulation correspond to the exact solution of the linear part of the transformed governing differential equation. Numerical results are presented for both linear and non-linear systems. The linear systems modeled are longitudinal and torsional rods and Bernoulli-Euler and Timoshenko beams. For non-linear systems, a viscoelastic rod and Von Karman type beam are modeled. The second topic is the analysis of plates and shallow shells under-going finite deflections by the Field/Boundary Element Method. Numerical results are presented for two plate problems. The first is the bifurcation problem associated with a square plate having free boundaries which is loaded by four, self equilibrating corner forces. The results are compared to two existing numerical solutions of the problem which differ substantially. plate. &The bending moments in the non-linear model are compared to those

Dynamic Modeling of Natural Convection Solar Energy Flat Plate ...

African Journals Online (AJOL)

The analytical solutions to the dynamic model of an air-heating flat plate solar energy thermal collector were validated by direct measurement from a physical model constructed for that purpose, of the temperatures of the cover and absorber plates, the inlet and outlet fluids, and the ambient air from morning to evening for ...

Is Active Tectonics on Madagascar Consistent with Somalian Plate Kinematics?

Science.gov (United States)

Stamps, D. S.; Kreemer, C.; Rajaonarison, T. A.

2017-12-01

The East African Rift System (EARS) actively breaks apart the Nubian and Somalian tectonic plates. Madagascar finds itself at the easternmost boundary of the EARS, between the Rovuma block, Lwandle plate, and the Somalian plate. Earthquake focal mechanisms and N-S oriented fault structures on the continental island suggest that Madagascar is experiencing east-west oriented extension. However, some previous plate kinematic studies indicate minor compressional strains across Madagascar. This inconsistency may be due to uncertainties in Somalian plate rotation. Past estimates of the rotation of the Somalian plate suffered from a poor coverage of GPS stations, but some important new stations are now available for a re-evaluation. In this work, we revise the kinematics of the Somalian plate. We first calculate a new GPS velocity solution and perform block kinematic modeling to evaluate the Somalian plate rotation. We then estimate new Somalia-Rovuma and Somalia-Lwandle relative motions across Madagascar and evaluate whether they are consistent with GPS measurements made on the island itself, as well as with other kinematic indicators.

Vortex sheet approximation of boundary layers

International Nuclear Information System (INIS)

Chorin, A.J.

1978-01-01

a grid free method for approximating incomprssible boundary layers is introduced. The computational elements are segments of vortex sheets. The method is related to the earlier vortex method; simplicity is achieved at the cost of replacing the Navier-Stokes equations by the Prandtl boundary layer equations. A new method for generating vorticity at boundaries is also presented; it can be used with the earlier voartex method. The applications presented include (i) flat plate problems, and (ii) a flow problem in a model cylinder- piston assembly, where the new method is used near walls and an improved version of the random choice method is used in the interior. One of the attractive features of the new method is the ease with which it can be incorporated into hybrid algorithms

CREATION OF MATHEMATICAL MODEL OF EXTRACTION BY CHEESE WHEY FROM A LUPINE IN THE FORM OF A PLATE

Directory of Open Access Journals (Sweden)

Y. I. Shishatskii

2015-01-01

Full Text Available Prerequisites for creation of model are stated. At a problem definition consideration of a particle of a lupine as unlimited plate is proved. The main assumptions are formulated, regional conditions are written out. Partial solutions of the differential equation, and also the common decision for the current value of a concentration pressure С'(x,у. Distribution of concentration is symmetric concerning ordinate axis. Final expression for a field of concentration at extraction of a flat plate in a dimensionless look is written out. It is shown that distribution of concentration is rather precisely described by the first member of a row. Th e conclusion is drawn that for any timepoint under the set boundary conditions the field of concentration has an appearance of a symmetric curve with a maximum on a plate axis (Х=0. For each subsequent timepoint there will be the curve which is monotonously decreasing to a plate surface. It is proved that it is possible to define nature of change of concentration in a body at a preset value the case when strives for infinity at the set physical parameters, thickness of a plate and the organization of high intensity of branch of extractive substances from a surface Is considered. For this case the equations of rather dimensionless concentration and Fourier's numb er are received. Also the equation for definition of final time of extraction is written out. It is shown that the received solutions of the eq uations of model are found in a good consent with experimental data.

Transpressional Tectonics across the N. American-Caribbean Plate Boundary: Preliminary Results of a Multichannel Seismic Survey of Lake Azuei, Haiti.

Science.gov (United States)

Hearn, C. K.; Cormier, M. H.; Sloan, H.; Wattrus, N. J.; Boisson, D.; Brown, B.; Guerrier, K.; King, J. W.; Knotts, P.; Momplaisir, R.; Sorlien, C. C.; Stempel, R.; Symithe, S. J.; Ulysse, S. M. J.

2017-12-01

On January 12, 2010, a Mw 7.0 earthquake struck Haiti, killing over 200,000 people and devastating the Capital city of Port-au-Prince and the surrounding regions. It ruptured a previously unknown blind-thrust fault that abuts the Enriquillo Plantain Garden Fault (EPGF), one of two transform faults that define the North American-Caribbean plate boundary. That earthquake highlighted how transpression across this complex boundary is accommodated by slip partitioning into strike-slip and compressional structures. Because the seismic hazard is higher for a rupture on a reverse or oblique-slip fault than on a vertical strike-slip fault, the need to characterize the geometry of that fault system is clear. Lake Azuei overlies this plate boundary 60 km east of the 2010 epicenter. The lake's 23 km long axis trends NW-SE, parallel to the Haitian fold-and-thrust belt and oblique to the EPGF. This tectonic context makes it an ideal target for investigating the partitioning of plate motion between strike-slip and compressional structures. In January 2017, we acquired 222 km of multichannel seismic (MCS) profiles in the lake, largely concurrent with subbottom seismic (CHIRP) profiles. The MCS data were acquired using a high-frequency BubbleGun source and a 75 m-long, 24-channel streamer, achieving a 24 seismic fold with a penetration of 200 m below lakebed. With the goal of resolving tectonic structures in 3-D, survey lines were laid out in a grid with profiles spaced 1.2 km apart. Additional profiles were acquired at the SE end of the lake where most of the tectonic activity is presumably occurring. The co-located CHIRP and MCS profiles document the continuity of tectonic deformation between the surficial sediments and the deeper strata. Preliminary processing suggests that a SW-dipping blind thrust fault, expressed updip as a large monocline fold, may control the western edge of the lake. Gentle, young folds that protrude from the flat lakebed are also imaged with the CHIRP

Dynamics of subduction and continental collision: Influence of the nature of the plate contact. Geologica Ultraiectina (284)

NARCIS (Netherlands)

De Franco, R.

2008-01-01

At convergent plate boundaries, the properties of the actual plate contact are important for the overall dynamics. Convergent plate boundaries both mechanically decouple and link tectonic plates and accommodate large amounts of strain. We investigate two fundamental physical states of the subduction

Interaction between bubble and air-backed plate with circular hole

Science.gov (United States)

Liu, Y. L.; Wang, S. P.; Zhang, A. M.

2016-06-01

This paper investigates the nonlinear interaction between a violent bubble and an air-backed plate with a circular hole. A numerical model is established using the incompressible potential theory coupled with the boundary integral method. A double-node technique is used to solve the overdetermined problem caused by the intersection between the solid wall and the free surface. A spark-generated bubble near the air-backed plate with a circular hole is observed experimentally using a high-speed camera. Our numerical results agree well with the experimental results. Both experimental and numerical results show that a multilevel spike emerges during the bubble's expansion and contraction. Careful numerical simulation reveals that this special type of spike is caused by the discontinuity in the boundary condition. The influences of the hole size and depth on the bubble and spike dynamics are also analyzed.

Heat transfer at microscopic level in a MHD fractional inertial flow confined between non-isothermal boundaries

Science.gov (United States)

Shoaib Anwar, Muhammad; Rasheed, Amer

2017-07-01

Heat transfer through a Forchheimer medium in an unsteady magnetohydrodynamic (MHD) developed differential-type fluid flow is analyzed numerically in this study. The boundary layer flow is modeled with the help of the fractional calculus approach. The fluid is confined between infinite parallel plates and flows by motion of the plates in their own plane. Both the plates have variable surface temperature. Governing partial differential equations with appropriate initial and boundary conditions are solved by employing a finite-difference scheme to discretize the fractional time derivative and finite-element discretization for spatial variables. Coefficients of skin friction and local Nusselt numbers are computed for the fractional model. The flow behavior is presented for various values of the involved parameters. The influence of different dimensionless numbers on skin friction and Nusselt number is discussed by tabular results. Forchheimer medium flows that involve catalytic converters and gas turbines can be modeled in a similar manner.

The baffle influence on sound radiation characteristics of a plate

Directory of Open Access Journals (Sweden)

Bao Liu

2017-01-01

Full Text Available The acoustic radiation characteristics of the baffle plates and unbaffle plates are calculated and compared by single-layer potential and double-layer potential. Based on the boundary integral equation, the sound pressure integral equation of the baffle and the baffle are deduced respectively. According to the boundary compatibility condition, the sound pressure and the vibration velocity of the plates are obtained. Further, the dynamic equation of the structure is substituted into the vibration equation in the form of the baffle plate and the baffle plate. The sound pressure difference and the displacement of a plate surface are in the form of the vibration mode superposition and the acoustic radiation impedance of the double integral form is obtained, which determines vibration mode coefficient and sound radiation parameters. The effect of the baffle on the acoustic radiation characteristics of the thin plate is analyzed by comparing the acoustic radiation parameters with the simple and simple rectangular plate in water.

Importance of initial buoyancy field on evolution of mantle thermal structure: Implications of surface boundary conditions

Directory of Open Access Journals (Sweden)

Petar Glišović

2015-01-01

Full Text Available Although there has been significant progress in the seismic imaging of mantle heterogeneity, the outstanding issue that remains to be resolved is the unknown distribution of mantle temperature anomalies in the distant geological past that give rise to the present-day anomalies inferred by global tomography models. To address this question, we present 3-D convection models in compressible and self-gravitating mantle initialised by different hypothetical temperature patterns. A notable feature of our forward convection modelling is the use of self-consistent coupling of the motion of surface tectonic plates to the underlying mantle flow, without imposing prescribed surface velocities (i.e., plate-like boundary condition. As an approximation for the surface mechanical conditions before plate tectonics began to operate we employ the no-slip (rigid boundary condition. A rigid boundary condition demonstrates that the initial thermally-dominated structure is preserved, and its geographical location is fixed during the evolution of mantle flow. Considering the impact of different assumed surface boundary conditions (rigid and plate-like on the evolution of thermal heterogeneity in the mantle we suggest that the intrinsic buoyancy of seven superplumes is most-likely resolved in the tomographic images of present-day mantle thermal structure. Our convection simulations with a plate-like boundary condition reveal that the evolution of an initial cold anomaly beneath the Java-Indonesian trench system yields a long-term, stable pattern of thermal heterogeneity in the lowermost mantle that resembles the present-day Large Low Shear Velocity Provinces (LLSVPs, especially below the Pacific. The evolution of subduction zones may be, however, influenced by the mantle-wide flow driven by deeply-rooted and long-lived superplumes since Archean times. These convection models also detect the intrinsic buoyancy of the Perm Anomaly that has been identified as a unique

Hall effects on free convection hydromagnetic boundary layer flow of Rivlin-Ericksen fluid past a vertical plate

International Nuclear Information System (INIS)

Jha, P.K.

1986-01-01

An attempt has been made to study the problem of free convection hydromagnetic flow of an elastico-viscous fluid past a porous vertical plate in a rotating frame of reference taking ohmic and viscous dissipations into account in the presence of Hall current. The nature of velocity profile shows the existence of multiple boundary layers. Their 'thickness' is seen to decrease with increasing values of Ekman, Hartman and Prandtl numbers and Hall parameter. The graphical study reveals that the increasing values of Hall parameter and Ekman number (for a fixed large value of Hall parameter) exert opposite influence on the flow. (author). 11 refs., 2 tables

INCOMPRESSIBLE LAMINAR BOUNDARY LAYER CONTROL BY BLOWING AND SUCTION

Directory of Open Access Journals (Sweden)

AZZEDINE NAHOUI

2013-12-01

Full Text Available A two-dimensional incompressible laminar boundary layer and its control using blowing and suction over a flat plate and around the NACA 0012 and 661012 profiles, is studied numerically. The study is based on the Prandtl boundary layer model using the finite differences method and the Crank-Nicolson scheme. The velocity distribution, the boundary layer thickness and the friction coefficient, are determined and presented with and without control. The application of the control technique, has demonstrated its positive effect on the transition point and the friction coefficient. Both control procedures are compared for different lengths, speeds and angles of blowing and suction.

Boundary representation modelling techniques

CERN Document Server

2006-01-01

Provides the most complete presentation of boundary representation solid modelling yet publishedOffers basic reference information for software developers, application developers and users Includes a historical perspective as well as giving a background for modern research.

Finite-Element Modeling of Timber Joints with Punched Metal Plate Fasteners

DEFF Research Database (Denmark)

Ellegaard, Peter

2006-01-01

The focus of this paper is to describe the idea and the theory behind a finite-element model developed for analysis of timber trusses with punched metal plate fasteners (nail plates). The finite-element model includes the semirigid and nonlinear behavior of the joints (nonlinear nail and plate...... elements) and contact between timber beams, if any (bilinear contact elements). The timber beams have linear-elastic properties. The section forces needed for design of the joints are given directly by the finite-element model, since special elements are used to model the nail groups and the nail plate...... the behavior of the joints very well at lower load levels. At higher load levels the stiffness is overestimated due to development of cracks in the timber and the linear-elastic timber properties in the finite-element model....

Finite element modelling for thermal analysis of stud-to-plate laser brazing for a dissimilar metal joint

International Nuclear Information System (INIS)

Park, Jun Soo; Kim, Jong Min

1996-06-01

A finite element model was developed for the thermal analysis of a stud-to-plate laser brazing joint, and the transient temperature fields were analysed by using a three-dimensional model. The finite element program ABAQUS, together with a few user subroutines, was employed to perform the numerical approximation. Temperature-dependent thermal properties, effect of latent heat, and the convection and radiative heat losses were considered. The brazing parts used were AISI 304 stainless steel stud and aluminium A1 5052 plate, and the brazing alloy 88 A1-12 Si was used as filler metal. A pseudo-TM 01 mode of the cw CO 2 laser beam was used as heat source, for which TM 00 mode generated by beam oscillator was optically modulated using axicon lens. Re-location of the filler metal during the brazing process including its wetting and spreading was examined by using a high speed motion analyser, and the results were incorporated inn the FEM modelling for defining the solution domain and boundary conditions. The numerical results were obtained for typical process parameters, and were compared with experimental ones determined by using the infrared and thermocouple measurements. 11 figs., 30 refs. (Author)

Theories for Elastic Plates via Orthogonal Polynomials

DEFF Research Database (Denmark)

Krenk, Steen

1981-01-01

A complementary energy functional is used to derive an infinite system of two-dimensional differential equations and appropriate boundary conditions for stresses and displacements in homogeneous anisotropic elastic plates. Stress boundary conditions are imposed on the faces a priori......, and this introduces a weight function in the variations of the transverse normal and shear stresses. As a result the coupling between the two-dimensional differential equations is described in terms of a single difference operator. Special attention is given to a truncated system of equations for bending...... of transversely isotropic plates. This theory has three boundary conditions, like Reissner's, but includes the effect of transverse normal strain, essentially through a reinterpretation of the transverse displacement function. Full agreement with general integrals to the homogeneous three-dimensional equations...

Flow of nanofluid past a Riga plate

Energy Technology Data Exchange (ETDEWEB)

Ahmad, Adeel, E-mail: adeelahmed@comsats.edu.pk [Department of Mathematics, COMSATS Institute of Information Technology, Park Road, Chak Shahzad, 44000 Islamabad (Pakistan); Laboratoire J.A. Dieudonné, Université de Nice Sophia Antipolis, Parc Valrose, 06108 Nice (France); Asghar, Saleem [Department of Mathematics, COMSATS Institute of Information Technology, Park Road, Chak Shahzad, 44000 Islamabad (Pakistan); Department of Mathematics, King Abdul Aziz University, Jeddah (Saudi Arabia); Afzal, Sumaira [Department of Mathematics, COMSATS Institute of Information Technology, Park Road, Chak Shahzad, 44000 Islamabad (Pakistan)

2016-03-15

This paper studies the mixed convection boundary layer flow of a nanofluid past a vertical Riga plate in the presence of strong suction. The mathematical model incorporates the Brownian motion and thermophoresis effects due to nanofluid and the Grinberg-term for the wall parallel Lorentz force due to Riga plate. The analytical solution of the problem is presented using the perturbation method for small Brownian and thermophoresis diffusion parameters. The numerical solution is also presented to ensure the reliability of the asymptotic method. The comparison of the two solutions shows an excellent agreement. The correlation expressions for skin friction, Nusselt number and Sherwood number are developed by performing linear regression on the obtained numerical data. The effects of nanofluid and the Lorentz force due to Riga plate, on the skin friction are discussed. - Highlights: • Mixed convection flow of a nanofluid past a vertical Riga plate. • The Brownian motion and thermophoresis effects due to nanofluid are incorporated. • Grinberg-term represents the wall parallel Lorentz force due to Riga plate. • The correlation expressions for skin friction, Nusselt and Sherwood numbers are developed. • The effects of nanofluid and the Lorentz force on the skin friction are discussed.

Modeling of high-density U-MO dispersion fuel plate performance

International Nuclear Information System (INIS)

Hayes, S.L.; Meyer, M.K.; Hofman, G.L.; Rest, J.; Snelgrove, J.L.

2002-01-01

Results from postirradiation examinations (PIE) of highly loaded U-Mo/Al dispersion fuel plates over the past several years have shown that the interaction between the metallic fuel particles and the matrix aluminum can be extensive, reducing the volume of the high-conductivity matrix phase and producing a significant volume of low-conductivity reaction-product phase. This phenomenon results in a significant decrease in fuel meat thermal conductivity during irradiation. PIE has further shown that the fuel-matrix interaction rate is a sensitive function of irradiation temperature. The interplay between fuel temperature and fuel-matrix interaction makes the development of a simple empirical correlation between the two difficult. For this reason a comprehensive thermal model has been developed to calculate temperatures throughout the fuel plate over its lifetime, taking into account the changing volume fractions of fuel, matrix and reaction-product phases within the fuel meat owing to fuel-matrix interaction; this thermal model has been incorporated into the dispersion fuel performance code designated PLATE. Other phenomena important to fuel thermal performance that are also treated in PLATE include: gas generation and swelling in the fuel and reaction-product phases, incorporation of matrix aluminum into solid solution with the unreacted metallic fuel particles, matrix extrusion resulting from fuel swelling, and cladding corrosion. The phenomena modeled also make possible a prediction of fuel plate swelling. This paper presents a description of the models and empirical correlations employed within PLATE as well as validation of code predictions against fuel performance data for U-Mo experimental fuel plates from the RERTR-3 irradiation test. (author)

Analysis Of Convective Plane Stagnation Point Chemically Reactive Mhd Flow Past A Vertical Porous Plate With A Convective Boundary Condition In The Presence Of A Uniform Magnetic Field.

OpenAIRE

Adeniyan, A.,

2013-01-01

The numerical investigation of a stagnation point boundary layer flow , mass and heat transfer of a steady two dimensional , incompressible , viscous electrically conducting, chemically reacting laminar fluid over a vertical convectively heated , electrically neutral flat plate exposed to a transverse uniform magnetic field has been carried out to examine the influence of the simultaneous presence of the effects of a convective boundary condition, chemical reaction, heat transfer and suctio...

NATURAL TRANSVERSE VIBRATIONS OF A PRESTRESSED ORTHOTROPIC PLATE-STRIPE

Directory of Open Access Journals (Sweden)

Egorychev Oleg Aleksandrovich

2012-10-01

Full Text Available The article represents a new outlook at the boundary-value problem of natural vibrations of a homogeneous pre-stressed orthotropic plate-stripe. In the paper, the motion equation represents a new approximate hyperbolic equation (rather than a parabolic equation used in the majority of papers covering the same problem describing the vibration of a homogeneous orthotropic plate-stripe. The proposed research is based on newly derived boundary conditions describing the pin-edge, rigid, and elastic (vertical types of fixing, as well as the boundary conditions applicable to the unfixed edge of the plate. The paper contemplates the application of the Laplace transformation and a non-standard representation of a homogeneous differential equation with fixed factors. The article proposes a detailed representation of the problem of natural vibrations of a homogeneous orthotropic plate-stripe if rigidly fixed at opposite sides; besides, the article also provides frequency equations (no conclusions describing the plate characterized by the following boundary conditions: rigid fixing at one side and pin-edge fixing at the opposite side; pin-edge fixing at one side and free (unfixed other side; rigid fixing at one side and elastic fixing at the other side. The results described in the article may be helpful if applied in the construction sector whenever flat structural elements are considered. Moreover, specialists in solid mechanics and theory of elasticity may benefit from the ideas proposed in the article.

Vibration Analysis of a Magnetoelectroelastic Rectangular Plate Based on a Higher-Order Shear Deformation Theory

Directory of Open Access Journals (Sweden)

Alireza Shooshtari

Full Text Available Abstract Free vibration of a magnetoelectroelastic rectangular plate is investigated based on the Reddy's third-order shear deformation theory. The plate rests on an elastic foundation and it is considered to have different boundary conditions. Gauss's laws for electrostatics and magnetostatics are used to model the electric and magnetic behavior. The partial differential equations of motion are reduced to a single partial differential equation and then by using the Galerkin method, the ordinary differential equation of motion as well as an analytical relation for the natural frequency of the plate is obtained. Some numerical examples are presented to validate the proposed model and to investigate the effects of several parameters on the vibration frequency of the considered smart plate.

Unsteady Heat-Flux Measurements of Second-Mode Instability Waves in a Hypersonic Boundary Layer

Science.gov (United States)

Kergerise, Michael A.; Rufer, Shann J.

2016-01-01

In this paper we report on the application of the atomic layer thermopile (ALTP) heat- flux sensor to the measurement of laminar-to-turbulent transition in a hypersonic flat plate boundary layer. The centerline of the flat-plate model was instrumented with a streamwise array of ALTP sensors and the flat-plate model was exposed to a Mach 6 freestream over a range of unit Reynolds numbers. Here, we observed an unstable band of frequencies that are associated with second-mode instability waves in the laminar boundary layer that forms on the flat-plate surface. The measured frequencies, group velocities, phase speeds, and wavelengths of these instability waves are in agreement with data previously reported in the literature. Heat flux time series, and the Morlet-wavelet transforms of them, revealed the wave-packet nature of the second-mode instability waves. In addition, a laser-based radiative heating system was developed to measure the frequency response functions (FRF) of the ALTP sensors used in the wind tunnel test. These measurements were used to assess the stability of the sensor FRFs over time and to correct spectral estimates for any attenuation caused by the finite sensor bandwidth.

Hydrogen Recombination Rates of Plate-type Passive Auto-catalytic Recombiner

Energy Technology Data Exchange (ETDEWEB)

Kim, Jongtae; Hong, Seong-Wan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kim, Gun Hong [Kyungwon E-C Co., Seongnam (Korea, Republic of)

2014-10-15

The hydrogen mitigation system may include igniters, passive autocatalytic recombiner (PAR), and venting or dilution system. Recently PAR is commonly used as a main component of HMS in a NPP containment because of its passive nature. PARs are categorized by the shape and material of catalytic surface. Catalytic surface coated by platinum is mostly used for the hydrogen recombiners. The shapes of the catalytic surface can be grouped into plate type, honeycomb type and porous media type. Among them, the plate-type PAR is well tested by many experiments. PAR performance analysis can be approached by a multi-scale method which is composed of micro, meso and macro scales. The criterion of the scaling is the ratio of thickness of boundary layer developed on a catalytic surface to representative length of a computational domain. Mass diffusion in the boundary layer must be resolved in the micro scale analysis. In a lumped parameter (LP) analysis using a system code such as MAAP or MELCOR, the chamber of the PAR is much smaller than a computational node. The hydrogen depletion by a PAR is modeled as a source of mass and energy conservation equations. Te catalytic surface reaction of hydrogen must be modeled by a volume-averaged correlation. In this study, a micro scale analysis method is developed using libraries in OpenFOAM to evaluate a hydrogen depletion rate depending on parameters such as size and number of plates and plate arrangement. The analysis code is validated by simulating REKO-3 experiment. And hydrogen depletion analysis is conducted by changing the plate arrangement as a trial of the performance enhancement of a PAR. In this study, a numerical code for an analysis of a PAR performance in a micro scale has been developed by using OpenFOAM libraries. The physical and numerical models were validated by simulating the REKO-3 experiment. As a try to enhance the performance of the plate-type PAR, it was proposed to apply a staggered two-layer arrangement of the

Hydrogen Recombination Rates of Plate-type Passive Auto-catalytic Recombiner

International Nuclear Information System (INIS)

Kim, Jongtae; Hong, Seong-Wan; Kim, Gun Hong

2014-01-01

The hydrogen mitigation system may include igniters, passive autocatalytic recombiner (PAR), and venting or dilution system. Recently PAR is commonly used as a main component of HMS in a NPP containment because of its passive nature. PARs are categorized by the shape and material of catalytic surface. Catalytic surface coated by platinum is mostly used for the hydrogen recombiners. The shapes of the catalytic surface can be grouped into plate type, honeycomb type and porous media type. Among them, the plate-type PAR is well tested by many experiments. PAR performance analysis can be approached by a multi-scale method which is composed of micro, meso and macro scales. The criterion of the scaling is the ratio of thickness of boundary layer developed on a catalytic surface to representative length of a computational domain. Mass diffusion in the boundary layer must be resolved in the micro scale analysis. In a lumped parameter (LP) analysis using a system code such as MAAP or MELCOR, the chamber of the PAR is much smaller than a computational node. The hydrogen depletion by a PAR is modeled as a source of mass and energy conservation equations. Te catalytic surface reaction of hydrogen must be modeled by a volume-averaged correlation. In this study, a micro scale analysis method is developed using libraries in OpenFOAM to evaluate a hydrogen depletion rate depending on parameters such as size and number of plates and plate arrangement. The analysis code is validated by simulating REKO-3 experiment. And hydrogen depletion analysis is conducted by changing the plate arrangement as a trial of the performance enhancement of a PAR. In this study, a numerical code for an analysis of a PAR performance in a micro scale has been developed by using OpenFOAM libraries. The physical and numerical models were validated by simulating the REKO-3 experiment. As a try to enhance the performance of the plate-type PAR, it was proposed to apply a staggered two-layer arrangement of the

The Interaction between the Plane Wave and the Plate with Limited Height in Soil

Directory of Open Access Journals (Sweden)

N.A. Lokteva

2017-03-01

Full Text Available A solution of the two-dimensional task on interaction between the harmonic wave and the plate with the limited height in soil has been provided. The plate surrounded on both sides with the half-spaces filled with soil medium has been used as a vibro-absorbing obstacle. The mechanical behavior of the plate has been described by S.P. Timoshenko's shift model and the mechanical behavior of soil by a linear elasticity theory equation. The main purpose of the paper is to determine the total acceleration vector field inducted by the penetrated and radiated waves in the second half-space. The mathematical formulation of the task includes a model of upcoming wave, soil medium and plate movement equation, infinity conditions, and conditions of soil contact with obstacle. Conditions of free slip have been taken as the contact conditions between the soil and the obstacle. We have considered a closed system of equations, which includes wave equations for scalar and vector potentials, elasticity theory equations for soil mediums, Koshi's relations, physical law, and plate movement equation. The boundary conditions for the plate correspond to a hinged support. To solve this task, all functions have been expanded in trigonometric series that allowed to obtain potential values in the coefficients of the series. To define the integrations constants, the contact conditions between the obstacle and soil have been used. On the basis of the revealed potentials, we have defined displacements on the boundary between the plate and soil and in other points of the second half-space. The vibro-absorbing properties of the plate have been investigated depending on the frequency of the harmonic wave falling on the plate. From the practical point of view, this task is related to protection of buildings from vibrations formed at a distance from underground railways.

A unified analysis of kinetic models for the problem of thermal creep based on the boundary conditions of Cercignani-Lampis for heterogeneous plates

International Nuclear Information System (INIS)

Rosa, Cinara Ewerling da; Knackfuss, Rosenei Felippe

2013-01-01

In this work is presented a series of numerical results and graphical comparisons of the physical quantities of interest such as: the velocity profile and the heat on profile. This formulation is developed for the problem of Thermal Creep, where the gas is moving between two parallel plates with different chemical constitutions (heterogeneous plates) due to a temperature gradient. The flow of a rarefied gas, is investigated with special attention to the gas-surface interaction, modeled by the Cercignani-Lampis kernel, that unlike Maxwell's scattering kernel, is defined in terms of two accommodation coefficients (normal and tangential) to represent the physical properties of the gas. The kinetic theory for rarefied gas dynamics, derived from the linearized Boltzmann equation, is developed in an unified approach, to the BGK model, S model, GJ model and MRS model. In the search for solutions to solve the problem of Thermal Creep with kernel of the Cercignani-Lampis, we used a analytical version of the discrete ordinates method (ADO) based on an arbitrary quadrature scheme, under which is determined a problem of eigenvalues and their respective separation constants. Numerical results are developed by the computer program FORTRAN. (author)

High precision refractometry based on Fresnel diffraction from phase plates.

Science.gov (United States)

Tavassoly, M Taghi; Naraghi, Roxana Rezvani; Nahal, Arashmid; Hassani, Khosrow

2012-05-01

When a transparent plane-parallel plate is illuminated at a boundary region by a monochromatic parallel beam of light, Fresnel diffraction occurs because of the abrupt change in phase imposed by the finite change in refractive index at the plate boundary. The visibility of the diffraction fringes varies periodically with changes in incident angle. The visibility period depends on the plate thickness and the refractive indices of the plate and the surrounding medium. Plotting the phase change versus incident angle or counting the visibility repetition in an incident-angle interval provides, for a given plate thickness, the refractive index of the plate very accurately. It is shown here that the refractive index of a plate can be determined without knowing the plate thickness. Therefore, the technique can be utilized for measuring plate thickness with high precision. In addition, by installing a plate with known refractive index in a rectangular cell filled with a liquid and following the described procedures, the refractive index of the liquid is obtained. The technique is applied to measure the refractive indices of a glass slide, distilled water, and ethanol. The potential and merits of the technique are also discussed.

Advanced Modelling of Trusses with Punched Metal Plate Fasteners

DEFF Research Database (Denmark)

Ellegaard, Peter; Nielsen, Jacob

Most of the finite element programs for design of timber trusses with punched metal fasteners are based on models using beam and fictitious elements. Different models have been used for different types of joints. Common problems for all the models are how to calculate the forces in the nail groups...... and the plates and furthermore, how big 'the deformations in the joints are. By developing an advanced model that includes all parts of the joint, i.e. plate, nail groups and contact it is possible to give a better description of the joint. An advanced model with these properties is presented. The advanced model...

Fuel cell cooler-humidifier plate

Science.gov (United States)

Vitale, Nicholas G.; Jones, Daniel O.

2000-01-01

A cooler-humidifier plate for use in a proton exchange membrane (PEM) fuel cell stack assembly is provided. The cooler-humidifier plate combines functions of cooling and humidification within the fuel cell stack assembly, thereby providing a more compact structure, simpler manifolding, and reduced reject heat from the fuel cell. Coolant on the cooler side of the plate removes heat generated within the fuel cell assembly. Heat is also removed by the humidifier side of the plate for use in evaporating the humidification water. On the humidifier side of the plate, evaporating water humidifies reactant gas flowing over a moistened wick. After exiting the humidifier side of the plate, humidified reactant gas provides needed moisture to the proton exchange membranes used in the fuel cell stack assembly. The invention also provides a fuel cell plate that maximizes structural support within the fuel cell by ensuring that the ribs that form the boundaries of channels on one side of the plate have ends at locations that substantially correspond to the locations of ribs on the opposite side of the plate.

Fracture Characteristics Analysis of Double-layer Rock Plates with Both Ends Fixed Condition

Directory of Open Access Journals (Sweden)

S. R. Wang

2014-07-01

Full Text Available In order to research on the fracture and instability characteristics of double-layer rock plates with both ends fixed, the three-dimension computational model of double-layer rock plates under the concentrated load was built by using PFC3D technique (three-dimension particle flow code, and the mechanical parameters of the numerical model were determined based on the physical model tests. The results showed the instability process of the double-layer rock plates had four mechanical response phases: the elastic deformation stage, the brittle fracture of upper thick plate arching stage, two rock-arch bearing stage and two rock-arch failure stage; moreover, with the rock plate particle radius from small to large change, the maximum vertical force of double rock-arch appeared when the particle size was a certain value. The maximum vertical force showed an upward trend with the increase of the rock plate temperature, and in the case of the same thickness the maximum vertical force increased with the increase of the upper rock plate thickness. When the boundary conditions of double-layer rock plates changed from the hinged support to the fixed support, the maximum horizontal force observably decreased, and the maximum vertical force showed small fluctuations and then tended towards stability with the increase of cohesive strength of double-layer rock plates.

Analysis of hydraulic instability of ANS involute fuel plates

International Nuclear Information System (INIS)

Sartory, W.K.

1991-11-01

Curved shell equations for the involute Advanced Neutron Source (ANS) fuel plates are coupled to two-dimensional hydraulic channel flow equations that include fluid friction. A complete set of fluid and plate boundary conditions is applied at the entrance and exit and along the sides of the plate and the channel. The coupled system is linearized and solved to assess the hydraulic instability of the plates

Development of Streamwise Counter-Rotating Vortices in Flat Plate Boundary Layer Pre-set by Leading Edge Patterns

KAUST Repository

Hasheminejad, S.M.

2017-04-03

Development of streamwise counter-rotating vortices induced by leading edge patterns with different pattern shape is investigated using hot-wire anemometry in the boundary layer of a flat plate. A triangular, sinusoidal and notched patterns with the same pattern wavelength λ of 15mm and the same pattern amplitude A of 7.5mm were examined for free-stream velocity of 3m/s. The results show a good agreement with earlier studies. The inflection point on the velocity profile downstream of the trough of the patterns at the beginning of the vortex formation indicates that the vortices non-linearly propagate downstream. An additional vortex structure was also observed between the troughs of the notched pattern.

High-Resolution P'P' Precursor Imaging of Nazca-South America Plate Boundary Zones and Inferences for Transition Zone Temperature and Composition

Science.gov (United States)

Gu, Y. J.; Schultz, R.

2013-12-01

elongated plate boundary zones of South America. Slab stagnation at the base of the transition zone could play a key role, though a proper interpretation of this finding would likely entail compositional (rather than strictly thermal) variations in the vicinity of the descending oceanic crust and lithosphere. Overall, the resolution and sensitivity differences between low/intermediate- S and high-frequency P wave reflections are key considerations toward reconciling seismic and mineralogical models of transition zone structure, both at the study location and worldwide.

Reorganization of convergent plate boundaries. Geologica Ultraiectina (340)

NARCIS (Netherlands)

Baes, M.

2011-01-01

It is still unclear where a subduction is initiated and what are the responsible mechanisms involved in subduction initiation process. Understanding of subduction initiation will advance our knowledge of how and when plate tectonics started on Earth. Another issue concerning the subduction process

Influence of yield stress on free convective boundary-layer flow of a non-Newtonian nanofluid past a vertical plate in a porous medium

International Nuclear Information System (INIS)

Hady, F. M.; Ibrahim, F. S.; Abdel-Gaied, S. M.; Eid, M. R.

2011-01-01

The effect of yield stress on the free convective heat transfer of dilute liquid suspensions of nanofluids flowing on a vertical plate saturated in porous medium under laminar conditions is investigated considering the nanofluid obeys the mathematical model of power-law. The model used for non-Newtonian nanofluid incorporates the effects of Brownian motion and thermophoresis. The governing boundary- layer equations are cast into dimensionless system which is solved numerically using a deferred correction technique and Newton iteration. This solution depends on yield stress parameter Ω, a power-law index n, Lewis number Le, a buoyancy-ratio number Nr, a Brownian motion number Nb, and a thermophoresis number Nt. Analyses of the results found that the reduced Nusselt and Sherwood numbers are decreasing functions of the higher yield stress parameter for each dimensionless numbers, n and Le, except the reduced Sherwood number is an increasing function of higher Nb for different values of yield stress parameter

Looking for Plate Tectonics in all the wrong fluids

Science.gov (United States)

Davaille, Anne

2017-04-01

Ever since the theory of Plate Tectonics in the 1960's, the dream of the geomodeler has been to generate plate tectonics self-consistently from thermal convection in the laboratory. By selfconsistenly, I mean that the configuration of the plate boundaries is in no way specified a priori, so that the plates develop and are wholly consumed without intervention from the modeler. The reciepe is simple : put a well-chosen fluid in a fishtank heated from below and cooled from above, wait and see. But the « well-chosen » is the difficult part... and the interesting one. Plate tectonics is occuring on Earth because of the characteristics of the lithosphere rheology. The latter are complex to estimate as they depend on temperature, pressure, phase, water content, chemistry, strain rate, memory and scale. As a result, the ingredients necessary for plate tectonics are still debated, and it would be useful to find an analog fluid who could reproduce plate tectonics in the laboratory. I have therefore spent the last 25 years to try out fluids, and I shall present a number of failures to generate plate tectonics using polymers, colloids, ketchup, milk, chocolate, sugar, oils. To understand why they failed is important to narrow down the « well-chosen » fluid.

Free vibration characteristics analysis of rectangular plate with rectangular opening based on Fourier series method

Directory of Open Access Journals (Sweden)

WANG Minhao

2017-08-01

Full Text Available Plate structures with openings are common in many engineering structures. The study of the vibration characteristics of such structures is directly related to the vibration reduction, noise reduction and stability analysis of an overall structure. This paper conducts research into the free vibration characteristics of a thin elastic plate with a rectangular opening parallel to the plate in an arbitrary position. We use the improved Fourier series to represent the displacement tolerance function of the rectangular plate with an opening. We can divide the plate into an eight zone plate to simplify the calculation. We then use linear springs, which are uniformly distributed along the boundary, to simulate the classical boundary conditions and the boundary conditions of the boundaries between the regions. According to the energy functional and variational method, we can obtain the overall energy functional. We can also obtain the generalized eigenvalue matrix equation by studying the extremum of the unknown improved Fourier series expansion coefficients. We can then obtain the natural frequencies and corresponding vibration modes of the rectangular plate with an opening by solving the equation. We then compare the calculated results with the finite element method to verify the accuracy and effectiveness of the method proposed in this paper. Finally, we research the influence of the boundary condition, opening size and opening position on the vibration characteristics of a plate with an opening. This provides a theoretical reference for practical engineering application.

On two-point boundary correlations in the six-vertex model with domain wall boundary conditions

Science.gov (United States)

Colomo, F.; Pronko, A. G.

2005-05-01

The six-vertex model with domain wall boundary conditions on an N × N square lattice is considered. The two-point correlation function describing the probability of having two vertices in a given state at opposite (top and bottom) boundaries of the lattice is calculated. It is shown that this two-point boundary correlator is expressible in a very simple way in terms of the one-point boundary correlators of the model on N × N and (N - 1) × (N - 1) lattices. In alternating sign matrix (ASM) language this result implies that the doubly refined x-enumerations of ASMs are just appropriate combinations of the singly refined ones.

Asymptotical construction of a fully coupled, Reissner–Mindlin model for piezoelectric composite plates

International Nuclear Information System (INIS)

Liao Lin; Yu Wenbin

2008-01-01

The variational asymptotic method is used to construct a fully coupled Reissner–Mindlin model for piezoelectric composite plates with some surfaces parallel to the reference surface coated with electrodes. Taking advantage of the smallness of the plate thickness, we asymptotically split the original three-dimensional electromechanical problem into a one-dimensional through-the-thickness analysis and a two-dimensional plate analysis. The through-the-thickness analysis serves as a link between the original three-dimensional analysis and the plate analysis by providing a constitutive model for the plate analysis and recovering the three-dimensional field variables in terms of two-dimensional plate global responses. The present theory is implemented into the computer program VAPAS (variational asymptotic plate and shell analysis). The resulting model is as simple as an equivalent single-layer, first-order shear deformation theory with accuracy comparable to higher-order layerwise theories. Various numerical examples have been used to validate the present model

Magneto-elastic dynamics and bifurcation of rotating annular plate*

International Nuclear Information System (INIS)

Hu Yu-Da; Piao Jiang-Min; Li Wen-Qiang

2017-01-01

In this paper, magneto-elastic dynamic behavior, bifurcation, and chaos of a rotating annular thin plate with various boundary conditions are investigated. Based on the thin plate theory and the Maxwell equations, the magneto-elastic dynamic equations of rotating annular plate are derived by means of Hamilton’s principle. Bessel function as a mode shape function and the Galerkin method are used to achieve the transverse vibration differential equation of the rotating annular plate with different boundary conditions. By numerical analysis, the bifurcation diagrams with magnetic induction, amplitude and frequency of transverse excitation force as the control parameters are respectively plotted under different boundary conditions such as clamped supported sides, simply supported sides, and clamped-one-side combined with simply-anotherside. Poincaré maps, time history charts, power spectrum charts, and phase diagrams are obtained under certain conditions, and the influence of the bifurcation parameters on the bifurcation and chaos of the system is discussed. The results show that the motion of the system is a complicated and repeated process from multi-periodic motion to quasi-period motion to chaotic motion, which is accompanied by intermittent chaos, when the bifurcation parameters change. If the amplitude of transverse excitation force is bigger or magnetic induction intensity is smaller or boundary constraints level is lower, the system can be more prone to chaos. (paper)

Eikonal Tomography of the Southern California Plate Boundary Region

Science.gov (United States)

Qiu, H.; Ben-Zion, Y.; Zigone, D.; Lin, F. C.

2016-12-01

We use eikonal tomography to derive directionally-dependent phase velocities of surface waves for the plate boundary region in southern CA sensitive to the approximate depth range 1-20 km. Seismic noise data recorded by 346 stations in the area provide a spatial coverage with 5-25 km typical station spacing and period range of 1-20 s. Noise cross-correlations are calculated for vertical component data recorded in year 2014. Rayleigh wave group and phase travel times between 2 and 13 sec period are derived for each station pair using frequency-time analysis. For each common station, all available phase travel time measurements with sufficient signal to noise ratio and envelope peak amplitude are used to construct a travel time map for a virtual source at the common station location. By solving the eikonal equation, both phase velocity and propagation direction are evaluated at each location for each virtual source. Isotropic phase velocities and 2-psi azimuthal anisotropy and their uncertainties are determined statistically using measurements from different virtual sources. Following the method of Barmin et al. (2001), group velocities are also inverted using all the group travel times that pass quality criteria. The obtained group and phase dispersions of Rayleigh waves are then inverted on a 6 x 6 km2 grid for local 1D piecewise shear wave velocity structures using the procedure of Herrmann (2013). The results agree well with previous observations of Zigone et al. (2015) in the overlapping area. Clear velocity contrasts and low velocity zones are seen for the San Andreas, San Jacinto, Elsinore and Garlock faults. We also find 2-psi azimuthal anisotropy with fast directions parallel to geometrically-simple fault sections. Details and updated results will be presented in the meeting.

Nonlinear dynamics of a circular piezoelectric plate for vibratory energy harvesting

Science.gov (United States)

Yuan, Tian-Chen; Yang, Jian; Chen, Li-Qun

2018-06-01

Nonlinear behaviors are investigated for a vibration-based energy harvester. The harvester consists of a circular composite plate with the clamped boundary, a proof mass and two steel rings. The lumped parameter model of the harvester is established and the parameters are identified from the experiment. The measured nonlinear behaviors can be approximately described by the lumped model. Both the experimental and the numerical results demonstrate that the circular plate harvester has soft characteristics under low excitation and both hard characteristics and soft characteristics under high excitation. The experimental results show that the output voltage can achieve over 35 V (about 50 mW) and more than 14 Hz of bandwidth with 25 kΩ load resistance.

Flow over a traveling wavy foil with a passively flapping flat plate

Science.gov (United States)

Liu, Nansheng; Peng, Yan; Liang, Youwen; Lu, Xiyun

2012-05-01

Flow over a traveling wavy foil with a passively flapping flat plate has been investigated using a multiblock lattice Boltzmann equation and the immersed boundary method. The foil undergoes prescribed undulations in the lateral direction and the rigid flat plate has passive motion determined by the fluid structure interaction. This simplified model is used to study the effect of the fish caudal fin and its flexibility on the locomotion of swimming animals. The flexibility of the caudal fin is modeled by a torsion spring acting about the pivot at the conjuncture of the wavy foil and the flat plate. The study reveals that the passively oscillating flat plate contributes half of the propulsive force. The flexibility, represented by the nondimensional natural frequency F, plays a very important role in the movement and propulsive force generation of the whole body. When the plate is too flexible, the drag force is observed. As the flat plate becomes more rigid, the propulsive force that is generated when the undulation is confined to last part of the wavy foil becomes larger. The steady movement occurs at F=5. These results are consistent with the observations of some swimming animals in nature.

Static and Monoharmonic Acoustic Impact on a Laminated Plate

Science.gov (United States)

Paimushin, V. N.; Gazizullin, R. K.

2017-07-01

A discrete layered damping model of a multilayer plate at small displacements and deformations, with account of the internal damping of layers according to the Thompson-Kelvin-Voight model, is presented. Based on the equations derived, an analytical solution to the static deformation problem for single-layer rectangular plate hinge-supported along its contour and subjected of a uniformly distributed pressure applied to one of its boundary planes is obtained. Its convergence to the three-dimensional solution is analyzed in relation to the dimension of mesh in the thickness direction of the plate. It is found that, for thin plates, the dimension of the problem formulated can be reduced on the basis of simplified hypotheses applied to each layer. An analytical solutions is also constructed for the forced vibrations of two- and three-layer rectangular plates hinged in the opening of an absolutely stiff dividing wall upon transmission of a monoharmonic sound wave through them. It was assumed that the dividing wall is situated between two absolutely stiff barriers; one of them, owing to the harmonic vibration with a given displacement amplitude of the plate, forms an incident sound wave, and the other is stationary and is coated by a energy-absorbing material with high damping properties. Behavior of the acoustic media in spaces between the deformable plate and the barriers is described by the classical wave equations based on the model of an ideal compressible fluid. To describe the process of dynamic deformation of the energy-absorbing coating of the fixed barrier, two-dimensional equations of motion are derived based on the model of a transversely soft layer, a linear approximation of displacement fields in the thickness direction of the coating, and the account of damping properties of its material by using the hysteresis model. The effect of physical and mechanical parameters of the mechanical system considered and of frequency of the incident sound wave on the

Pacific plate slab pull and intraplate deformation in the early Cenozoic

Directory of Open Access Journals (Sweden)

N. P. Butterworth

2014-08-01

Full Text Available Large tectonic plates are known to be susceptible to internal deformation, leading to a~range of phenomena including intraplate volcanism. However, the space and time dependence of intraplate deformation and its relationship with changing plate boundary configurations, subducting slab geometries, and absolute plate motion is poorly understood. We utilise a buoyancy-driven Stokes flow solver, BEM-Earth, to investigate the contribution of subducting slabs through time on Pacific plate motion and plate-scale deformation, and how this is linked to intraplate volcanism. We produce a series of geodynamic models from 62 to 42 Ma in which the plates are driven by the attached subducting slabs and mantle drag/suction forces. We compare our modelled intraplate deformation history with those types of intraplate volcanism that lack a clear age progression. Our models suggest that changes in Cenozoic subduction zone topology caused intraplate deformation to trigger volcanism along several linear seafloor structures, mostly by reactivation of existing seamount chains, but occasionally creating new volcanic chains on crust weakened by fracture zones and extinct ridges. Around 55 Ma, subduction of the Pacific-Izanagi ridge reconfigured the major tectonic forces acting on the plate by replacing ridge push with slab pull along its northwestern perimeter, causing lithospheric extension along pre-existing weaknesses. Large-scale deformation observed in the models coincides with the seamount chains of Hawaii, Louisville, Tokelau and Gilbert during our modelled time period of 62 to 42 Ma. We suggest that extensional stresses between 72 and 52 Ma are the likely cause of large parts of the formation of the Gilbert chain and that localised extension between 62 and 42 Ma could cause late-stage volcanism along the Musicians volcanic ridges. Our models demonstrate that early Cenozoic changes in Pacific plate driving forces only cause relatively minor changes in Pacific

Stress and displacement analysis of a core plate, i.e. grid-perforated plate compound, modelled as an equivalent beam system

International Nuclear Information System (INIS)

Frank, R.; Engel, R.

1979-01-01

The core support plate is a very important component of the reactor pressure vessel internals. Therefore, an exact stress analysis is desired. This analysis will cause high computer costs with a detailed FEM-model because of the complexity of this compound system. In this paper, a method is suggested to solve the problem with a much cheaper beam element model. The main problem is to establish an equivalent beam system with nearly the same stiffness property as the perforated circular plate stiffened by a grid. Furthermore, the system must allow to determine the maximum stresses with sufficient accuracy. The calculation of the equivalent beam stiffness is based on the analysis of perforated plates by T. SLOT and W.J. O'DONNELL. This analysis method utilizes the concept of the equivalent solid plate. In this method, the perforated plate is replaced by a solid one which is geometrically similar to the perforated plate but has modified values of the elastic constants. The simple equivalent beam system of one half of the core support plate (symmetry) was loaded with a pressure difference and stresses and displacements were analysed. After that, these results were compared with the stress and displacement analysis of a part of the real structure. This substructure was discretized by three-dimensional 20-node brick-elements. The comparison of the results of the two models shows that the stresses and displacements, calculated with the simple beam model, are in good agreement with those of the real structure. (orig.)

The influence of finite cavities on the sound insulation of double-plate structures.

Science.gov (United States)

Brunskog, Jonas

2005-06-01

Lightweight walls are often designed as frameworks of studs with plates on each side--a double-plate structure. The studs constitute boundaries for the cavities, thereby both affecting the sound transmission directly by short-circuiting the plates, and indirectly by disturbing the sound field between the plates. The paper presents a deterministic prediction model for airborne sound insulation including both effects of the studs. A spatial transform technique is used, taking advantage of the periodicity. The acoustic field inside the cavities is expanded by means of cosine-series. The transmission coefficient (angle-dependent and diffuse) and transmission loss are studied. Numerical examples are presented and comparisons with measurement are performed. The result indicates that a reasonably good agreement between theory and measurement can be achieved.

Searching for Hysteresis in Models of Mantle Convection with Grain-Damage

Science.gov (United States)

Lamichhane, R.; Foley, B. J.

2017-12-01

The mode of surface tectonics on terrestrial planets is determined by whether mantle convective forces are capable of forming weak zones of localized deformation in the lithosphere, which act as plate boundaries. If plate boundaries can form then a plate tectonic mode develops, and if not convection will be in the stagnant lid regime. Episodic subduction or sluggish lid convection are also possible in between the nominal plate tectonic and stagnant lid regimes. Plate boundary formation is largely a function of the state of the mantle, e.g. mantle temperature or surface temperature, and how these conditions influence both mantle convection and the mantle rheology's propensity for forming weak, localized plate boundaries. However, a planet's tectonic mode also influences whether plate boundaries can form, as the driving forces for plate boundary formation (e.g. stress and viscous dissipation) are different in a plate tectonic versus stagnant lid regime. As a result, tectonic mode can display hysteresis, where convection under otherwise identical conditions can reach different final states as a result of the initial regime of convection. Previous work has explored this effect in pseudoplastic models, finding that it is more difficult to initiate plate tectonics starting from a stagnant lid state than it is to sustain plate tectonics when already in a mobile lid regime, because convective stresses in the lithosphere are lower in a stagnant lid regime than in a plate tectonic regime. However, whether and to what extent such hysteresis is displayed when alternative rheological models for lithospheric shear localization are used is unknown. In particular, grainsize reduction is commonly hypothesized to be a primary cause of shear localization and plate boundary formation. We use new models of mantle convection with grain-size evolution to determine how the initial mode of surface tectonics influences the final convective regime reached when convection reaches statistical

Energy-Dissipation Performance of Combined Low Yield Point Steel Plate Damper Based on Topology Optimization and Its Application in Structural Control

Directory of Open Access Journals (Sweden)

Haoxiang He

2016-01-01

Full Text Available In view of the disadvantages such as higher yield stress and inadequate adjustability, a combined low yield point steel plate damper involving low yield point steel plates and common steel plates is proposed. Three types of combined plate dampers with new hollow shapes are proposed, and the specific forms include interior hollow, boundary hollow, and ellipse hollow. The “maximum stiffness” and “full stress state” are used as the optimization objectives, and the topology optimization of different hollow forms by alternating optimization method is to obtain the optimal shape. Various combined steel plate dampers are calculated by finite element simulation, the results indicate that the initial stiffness of the boundary optimized damper and interior optimized damper is lager, the hysteresis curves are full, and there is no stress concentration. These two types of optimization models made in different materials rations are studied by numerical simulation, and the adjustability of yield stress of these combined dampers is verified. The nonlinear dynamic responses, seismic capacity, and damping effect of steel frame structures with different combined dampers are analyzed. The results show that the boundary optimized damper has better energy-dissipation capacity and is suitable for engineering application.

On relevant boundary perturbations of unitary minimal models

International Nuclear Information System (INIS)

Recknagel, A.; Roggenkamp, D.; Schomerus, V.

2000-01-01

We consider unitary Virasoro minimal models on the disk with Cardy boundary conditions and discuss deformations by certain relevant boundary operators, analogous to tachyon condensation in string theory. Concentrating on the least relevant boundary field, we can perform a perturbative analysis of renormalization group fixed points. We find that the systems always flow towards stable fixed points which admit no further (non-trivial) relevant perturbations. The new conformal boundary conditions are in general given by superpositions of 'pure' Cardy boundary conditions

Strain resolving method of composite plane plates

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Ion FUIOREA

2011-06-01

Full Text Available The paper deals with the extension of isotropic plates problem to the case of composite plates. In order to perform it, the Kirchhoff-Love hypotheses were “softened” by some additional ones. Considering the constitutive laws for composite materials the stress functions were eliminated by using Cauchy equations. As a result a partial derivative equation in displacements was obtained. Finally the boundary condition formulation was extended for the case of complex composite plates.

Viscoelastic Plate Analysis Based on Gâteaux Differential

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Kadıoğlu Fethi

2016-01-01

Full Text Available In this study, it is aimed to analyze the quasi-static response of viscoelastic Kirchhoff plates with mixed finite element formulation based on the Gâteaux differential. Although the static response of elastic plate, beam and shell structures is a widely studied topic, there are few studies that exist in the literature pertaining to the analysis of the viscoelastic structural elements especially with complex geometries, loading conditions and constitutive relations. The developed mixed finite element model in transformed Laplace-Carson space has four unknowns as displacement, bending and twisting moments in addition to the dynamic and geometric boundary condition terms. Four-parameter solid model is employed for modelling the viscoelastic behaviour. For transformation of the solutions obtained in the Laplace-Carson domain to the time domain, different numerical inverse transform techniques are employed. The developed solution technique is applied to several quasi-static example problems for the verification of the suggested numerical procedure.

Modeling of laser welding of steel and titanium plates with a composite insert

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Isaev, V. I.; Cherepanov, A. N.; Shapeev, V. P.

2017-10-01

A 3D model of laser welding proposed before by the authors was extended to the case of welding of metallic plates made of dissimilar materials with a composite multilayer intermediate insert. The model simulates heat transfer in the welded plates and takes into account phase transitions. It was proposed to select the composition of several metals and dimensions of the insert to avoid the formation of brittle intermetallic phases in the weld joint negatively affecting its strength properties. The model accounts for key physical phenomena occurring during the complex process of laser welding. It is capable to calculate temperature regimes at each point of the plates. The model can be used to select the welding parameters reducing the risk of formation of intermetallic plates. It can forecast the dimensions and crystalline structure of the solidified melt. Based on the proposed model a numerical algorithm was constructed. Simulations were carried out for the welding of titanium and steel plates with a composite insert comprising four different metals: copper and niobium (intermediate plates) with steel and titanium (outer plates). The insert is produced by explosion welding. Temperature fields and the processes of melting, evaporation, and solidification were studied.

Multiscale model of metal alloy oxidation at grain boundaries

International Nuclear Information System (INIS)

Sushko, Maria L.; Alexandrov, Vitaly; Schreiber, Daniel K.; Rosso, Kevin M.; Bruemmer, Stephen M.

2015-01-01

High temperature intergranular oxidation and corrosion of metal alloys is one of the primary causes of materials degradation in nuclear systems. In order to gain insights into grain boundary oxidation processes, a mesoscale metal alloy oxidation model is established by combining quantum Density Functional Theory (DFT) and mesoscopic Poisson-Nernst-Planck/classical DFT with predictions focused on Ni alloyed with either Cr or Al. Analysis of species and fluxes at steady-state conditions indicates that the oxidation process involves vacancy-mediated transport of Ni and the minor alloying element to the oxidation front and the formation of stable metal oxides. The simulations further demonstrate that the mechanism of oxidation for Ni-5Cr and Ni-4Al is qualitatively different. Intergranular oxidation of Ni-5Cr involves the selective oxidation of the minor element and not matrix Ni, due to slower diffusion of Ni relative to Cr in the alloy and due to the significantly smaller energy gain upon the formation of nickel oxide compared to that of Cr 2 O 3 . This essentially one-component oxidation process results in continuous oxide formation and a monotonic Cr vacancy distribution ahead of the oxidation front, peaking at alloy/oxide interface. In contrast, Ni and Al are both oxidized in Ni-4Al forming a mixed spinel NiAl 2 O 4 . Different diffusivities of Ni and Al give rise to a complex elemental distribution in the vicinity of the oxidation front. Slower diffusing Ni accumulates in the oxide and metal within 3 nm of the interface, while Al penetrates deeper into the oxide phase. Ni and Al are both depleted from the region 3–10 nm ahead of the oxidation front creating voids. The oxide microstructure is also different. Cr 2 O 3 has a plate-like structure with 1.2–1.7 nm wide pores running along the grain boundary, while NiAl 2 O 4 has 1.5 nm wide pores in the direction parallel to the grain boundary and 0.6 nm pores in the perpendicular direction providing an additional

Using open sidewalls for modelling self-consistent lithosphere subduction dynamics

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M. V. Chertova

2012-10-01

Full Text Available Subduction modelling in regional model domains, in 2-D or 3-D, is commonly performed using closed (impermeable vertical boundaries. Here we investigate the merits of using open boundaries for 2-D modelling of lithosphere subduction. Our experiments are focused on using open and closed (free slip sidewalls while comparing results for two model aspect ratios of 3:1 and 6:1. Slab buoyancy driven subduction with open boundaries and free plates immediately develops into strong rollback with high trench retreat velocities and predominantly laminar asthenospheric flow. In contrast, free-slip sidewalls prove highly restrictive on subduction rollback evolution, unless the lithosphere plates are allowed to move away from the sidewalls. This initiates return flows pushing both plates toward the subduction zone speeding up subduction. Increasing the aspect ratio to 6:1 does not change the overall flow pattern when using open sidewalls but only the flow magnitude. In contrast, for free-slip boundaries, the slab evolution does change with respect to the 3:1 aspect ratio model and slab evolution does not resemble the evolution obtained with open boundaries using 6:1 aspect ratio. For models with open side boundaries, we could develop a flow-speed scaling based on energy dissipation arguments to convert between flow fields of different model aspect ratios. We have also investigated incorporating the effect of far-field generated lithosphere stress in our open boundary models. By applying realistic normal stress conditions to the strong part of the overriding plate at the sidewalls, we can transfer intraplate stress to influence subduction dynamics varying from slab roll-back, stationary subduction, to advancing subduction. The relative independence of the flow field on model aspect ratio allows for a smaller modelling domain. Open boundaries allow for subduction to evolve freely and avoid the adverse effects (e.g. forced return flows of free-slip boundaries. We

An Experimentally Validated Numerical Modeling Technique for Perforated Plate Heat Exchangers.

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White, M J; Nellis, G F; Kelin, S A; Zhu, W; Gianchandani, Y

2010-11-01

Cryogenic and high-temperature systems often require compact heat exchangers with a high resistance to axial conduction in order to control the heat transfer induced by axial temperature differences. One attractive design for such applications is a perforated plate heat exchanger that utilizes high conductivity perforated plates to provide the stream-to-stream heat transfer and low conductivity spacers to prevent axial conduction between the perforated plates. This paper presents a numerical model of a perforated plate heat exchanger that accounts for axial conduction, external parasitic heat loads, variable fluid and material properties, and conduction to and from the ends of the heat exchanger. The numerical model is validated by experimentally testing several perforated plate heat exchangers that are fabricated using microelectromechanical systems based manufacturing methods. This type of heat exchanger was investigated for potential use in a cryosurgical probe. One of these heat exchangers included perforated plates with integrated platinum resistance thermometers. These plates provided in situ measurements of the internal temperature distribution in addition to the temperature, pressure, and flow rate measured at the inlet and exit ports of the device. The platinum wires were deposited between the fluid passages on the perforated plate and are used to measure the temperature at the interface between the wall material and the flowing fluid. The experimental testing demonstrates the ability of the numerical model to accurately predict both the overall performance and the internal temperature distribution of perforated plate heat exchangers over a range of geometry and operating conditions. The parameters that were varied include the axial length, temperature range, mass flow rate, and working fluid.

Tectonic predictions with mantle convection models

Science.gov (United States)

Coltice, Nicolas; Shephard, Grace E.

2018-04-01

Over the past 15 yr, numerical models of convection in Earth's mantle have made a leap forward: they can now produce self-consistent plate-like behaviour at the surface together with deep mantle circulation. These digital tools provide a new window into the intimate connections between plate tectonics and mantle dynamics, and can therefore be used for tectonic predictions, in principle. This contribution explores this assumption. First, initial conditions at 30, 20, 10 and 0 Ma are generated by driving a convective flow with imposed plate velocities at the surface. We then compute instantaneous mantle flows in response to the guessed temperature fields without imposing any boundary conditions. Plate boundaries self-consistently emerge at correct locations with respect to reconstructions, except for small plates close to subduction zones. As already observed for other types of instantaneous flow calculations, the structure of the top boundary layer and upper-mantle slab is the dominant character that leads to accurate predictions of surface velocities. Perturbations of the rheological parameters have little impact on the resulting surface velocities. We then compute fully dynamic model evolution from 30 and 10 to 0 Ma, without imposing plate boundaries or plate velocities. Contrary to instantaneous calculations, errors in kinematic predictions are substantial, although the plate layout and kinematics in several areas remain consistent with the expectations for the Earth. For these calculations, varying the rheological parameters makes a difference for plate boundary evolution. Also, identified errors in initial conditions contribute to first-order kinematic errors. This experiment shows that the tectonic predictions of dynamic models over 10 My are highly sensitive to uncertainties of rheological parameters and initial temperature field in comparison to instantaneous flow calculations. Indeed, the initial conditions and the rheological parameters can be good enough

NLIE of Dirichlet sine-Gordon model for boundary bound states

International Nuclear Information System (INIS)

Ahn, Changrim; Bajnok, Zoltan; Palla, Laszlo; Ravanini, Francesco

2008-01-01

We investigate boundary bound states of sine-Gordon model on the finite-size strip with Dirichlet boundary conditions. For the purpose we derive the nonlinear integral equation (NLIE) for the boundary excited states from the Bethe ansatz equation of the inhomogeneous XXZ spin 1/2 chain with boundary imaginary roots discovered by Saleur and Skorik. Taking a large volume (IR) limit we calculate boundary energies, boundary reflection factors and boundary Luescher corrections and compare with the excited boundary states of the Dirichlet sine-Gordon model first considered by Dorey and Mattsson. We also consider the short distance limit and relate the IR scattering data with that of the UV conformal field theory

Fault and graben growth along active magmatic divergent plate boundaries in Iceland and Ethiopia

KAUST Repository

Trippanera, D.; Acocella, V.; Ruch, Joel; Abebe, B.

2015-01-01

Recent studies highlight the importance of annual-scale dike-induced rifting episodes in developing normal faults and graben along the active axis of magmatic divergent plate boundaries (MDPB). However, the longer-term (102-105 years) role of diking on the cumulative surface deformation and evolution of MDPB is not yet well understood. To better understand the longer-term normal faults and graben along the axis of MDPB, we analyze fissure swarms in Iceland and Ethiopia. We first focus on the simplest case of immature fissure swarms, with single dike-fed eruptive fissures; these consist of a <1 km wide graben bordered by normal faults with displacement up to a few meters, consistent with theoretical models and geodetic data. A similar structural pattern is found, with asymmetric and multiple graben, within wider mature fissure swarms, formed by several dike-fed eruptive fissures. We then consider the lateral termination of normal faults along these graben, to detect their upward or downward propagation. Most faults terminate as open fractures on flat surface, suggesting downward fault propagation; this is consistent with recent experiments showing dike-induced normal faults propagating downward from the surface. However, some normal faults also terminate as open fractures on monoclines, which resemble fault propagation folds; this suggests upward propagation of reactivated buried faults, promoted by diking. These results suggest that fault growth and graben development, as well as the longer-term evolution of the axis of MDPB, may be explained only through dike emplacement and that any amagmatic faulting is not necessary.

Fault and graben growth along active magmatic divergent plate boundaries in Iceland and Ethiopia

KAUST Repository

Trippanera, D.

2015-10-08

Recent studies highlight the importance of annual-scale dike-induced rifting episodes in developing normal faults and graben along the active axis of magmatic divergent plate boundaries (MDPB). However, the longer-term (102-105 years) role of diking on the cumulative surface deformation and evolution of MDPB is not yet well understood. To better understand the longer-term normal faults and graben along the axis of MDPB, we analyze fissure swarms in Iceland and Ethiopia. We first focus on the simplest case of immature fissure swarms, with single dike-fed eruptive fissures; these consist of a <1 km wide graben bordered by normal faults with displacement up to a few meters, consistent with theoretical models and geodetic data. A similar structural pattern is found, with asymmetric and multiple graben, within wider mature fissure swarms, formed by several dike-fed eruptive fissures. We then consider the lateral termination of normal faults along these graben, to detect their upward or downward propagation. Most faults terminate as open fractures on flat surface, suggesting downward fault propagation; this is consistent with recent experiments showing dike-induced normal faults propagating downward from the surface. However, some normal faults also terminate as open fractures on monoclines, which resemble fault propagation folds; this suggests upward propagation of reactivated buried faults, promoted by diking. These results suggest that fault growth and graben development, as well as the longer-term evolution of the axis of MDPB, may be explained only through dike emplacement and that any amagmatic faulting is not necessary.

Experiments in a boundary layer subjected to free stream turbulence. Part 1: Boundary layer structure and receptivity

International Nuclear Information System (INIS)

Westin, K.J.A.; Boiko, A.V.; Klingmann, B.G.B.; Kozlov, V.V.; Alfredsson, P.H.

1993-12-01

The modification of the mean and fluctuating characteristics of a flat plate boundary layer subjected to nearly isotropic free stream turbulence (FST) is studied experimentally using hot-wire anemometry. The study is focussed on the region upstream of the transition onset, where the fluctuations inside the boundary layer are dominated by elongated flow structures which grow downstream both in amplitude and length. Their downstream development and scaling is investigated, and the results are compared to those obtained by previous authors. This allows some conclusions about the parameters which are relevant for the modelling of the transition process. The mechanisms underlying the transition process and the relative importance of the Tollmien-Schlichting wave instability in this flow are treated in an accompanying paper. 25 refs

On non-equilibrium states in QFT model with boundary interaction

International Nuclear Information System (INIS)

Bazhanov, Vladimir V.; Lukyanov, Sergei L.; Zamolodchikov, Alexander B.

1999-01-01

We prove that certain non-equilibrium expectation values in the boundary sine-Gordon model coincide with associated equilibrium-state expectation values in the systems which differ from the boundary sine-Gordon in that certain extra boundary degrees of freedom (q-oscillators) are added. Applications of this result to actual calculation of non-equilibrium characteristics of the boundary sine-Gordon model are also discussed

Hydrodynamics of a flexible plate between pitching rigid plates

Science.gov (United States)

Kim, Junyoung; Kim, Daegyoum

2017-11-01

The dynamics of a flexible plate have been studied as a model problem in swimming and flying of animals and fluid-structure interaction of plants and flags. Motivated by fish schooling and an array of sea grasses, we investigate the dynamics of a flexible plate closely placed between two pitching rigid plates. In most studies on passive deformation of the flexible plate, the plate is immersed in a uniform flow or a wavy flow. However, in this study, the flexible plate experiences periodic deformation by the oscillatory flow generated by the prescribed pitching motion of the rigid plates. In our model, the pitching axes of the rigid plates and the clamping position of the flexible plate are aligned on the same line. The flexible plate shows various responses depending on length and pitching frequency of rigid plates, thickness of a flexible plate, and free-stream velocity. To find the effect of each variable on the response of the flexible plate, amplitude of a trailing edge and modal contribution of a flapping motion are compared, and flow structure around the flexible plate is examined.

A model of breakdown in parallel-plate detectors

International Nuclear Information System (INIS)

Fonte, P.

1996-01-01

Parallel-plate avalanche chambers (PPAC's) have many desirable properties, such as a fast, large area particle detector. However, the maximum gain is limited by a form of violent breakdown that limits the usefulness of this detector, despite its other evident qualities. The exact nature of this phenomenon is not yet sufficiently clear to sustain possible improvements. A previous experimental study is complemented in the present work by a quantitative model of the breakdown phenomenon in PPAC's, based on the streamer theory. The model reproduces well the peculiar behavior of the external current observed in PPAC's and resistive-plate chambers. Other breakdown properties measured in PPAC's are also well reproduced

Classically integrable boundary conditions for symmetric-space sigma models

International Nuclear Information System (INIS)

MacKay, N.J.; Young, C.A.S.

2004-01-01

We investigate boundary conditions for the non-linear sigma model on the compact symmetric space G/H. The Poisson brackets and the classical local conserved charges necessary for integrability are preserved by boundary conditions which correspond to involutions which commute with the involution defining H. Applied to SO(3)/SO(2), the non-linear sigma model on S 2 , these yield the great circles as boundary submanifolds. Applied to GxG/G, they reproduce known results for the principal chiral model

Coupled wake boundary layer model of windfarms

Science.gov (United States)

Stevens, Richard; Gayme, Dennice; Meneveau, Charles

2014-11-01

We present a coupled wake boundary layer (CWBL) model that describes the distribution of the power output in a windfarm. The model couples the traditional, industry-standard wake expansion/superposition approach with a top-down model for the overall windfarm boundary layer structure. Wake models capture the effect of turbine positioning, while the top-down approach represents the interaction between the windturbine wakes and the atmospheric boundary layer. Each portion of the CWBL model requires specification of a parameter that is unknown a-priori. The wake model requires the wake expansion rate, whereas the top-down model requires the effective spanwise turbine spacing within which the model's momentum balance is relevant. The wake expansion rate is obtained by matching the mean velocity at the turbine from both approaches, while the effective spanwise turbine spacing is determined from the wake model. Coupling of the constitutive components of the CWBL model is achieved by iterating these parameters until convergence is reached. We show that the CWBL model predictions compare more favorably with large eddy simulation results than those made with either the wake or top-down model in isolation and that the model can be applied successfully to the Horns Rev and Nysted windfarms. The `Fellowships for Young Energy Scientists' (YES!) of the Foundation for Fundamental Research on Matter supported by NWO, and NSF Grant #1243482.

Hydrogeological boundary settings in SR 97. Uncertainties in regional boundary settings and transfer of boundary conditions to site-scale models

International Nuclear Information System (INIS)

Follin, S.

1999-06-01

The SR 97 project presents a performance assessment (PA) of the overall safety of a hypothetical deep repository at three sites in Sweden arbitrarily named Aberg, Beberg and Ceberg. One component of this PA assesses the uncertainties in the hydrogeological modelling. This study focuses on uncertainties in boundary settings (size of model domain and boundary conditions) in the regional and site-scale hydrogeological modelling of the three sites used to simulating the possible transport of radionuclides from the emplacement waste packages through the host rock to the accessible environment. Model uncertainties associated with, for instance, parameter heterogeneity and structural interpretations are addressed in other studies. This study concludes that the regional modelling of the SR 97 project addresses uncertainties in the choice of boundary conditions and size of model domain differently at each site, although the overall handling is acceptable and in accordance with common modelling practice. For example, the treatment of uncertainties with regard to the ongoing post-glacial flushing of the Baltic Shield is creditably addressed although not exhaustive from a modelling point of view. A significant contribution of the performed modelling is the study of nested numerical models, i.e., the numerical interplay between regional and site-scale numerical models. In the site-scale modelling great efforts are made to address problems associated with (i) the telescopic mesh refinement (TMR) technique with regard to the stochastic continuum approach, and (ii) the transfer of boundary conditions between variable-density flow systems and flow systems that are constrained to treat uniform density flow. This study concludes that the efforts made to handle these problems are acceptable with regards to the objectives of the SR 97 project

A New Estimate for Total Offset on the Southern San Andreas Fault: Implications for Cumulative Plate Boundary Shear in the Northern Gulf of California

Science.gov (United States)

Darin, M. H.; Dorsey, R. J.

2012-12-01

Development of a consistent and balanced tectonic reconstruction for the late Cenozoic San Andreas fault (SAF) in southern California has been hindered for decades by incompatible estimates of total dextral offset based on different geologic cross-fault markers. The older estimate of 240-270 km is based on offset fluvial conglomerates of the middle Miocene Mint Canyon and Caliente Formations west of the SAF from their presumed source area in the northern Chocolate Mountains NE of the SAF (Ehlig et al., 1975; Ehlert, 2003). The second widely cited offset marker is a distinctive Triassic megaporphyritic monzogranite that has been offset 160 ± 10 km between Liebre Mountain west of the SAF and the San Bernadino Mountains (Matti and Morton, 1993). In this analysis we use existing paleocurrent data and late Miocene clockwise rotation in the eastern Transverse Ranges (ETR) to re-assess the orientation of the piercing line used in the 240 km-correlation, and present a palinspastic reconstruction that satisfies all existing geologic constraints. Our reconstruction of the Mint Canyon piercing line reduces the original estimate of 240-270 km to 195 ± 15 km of cumulative right-lateral slip on the southern SAF (sensu stricto), which is consistent with other published estimates of 185 ± 20 km based on correlative basement terranes in the Salton Trough region. Our estimate of ~195 km is consistent with the lower estimate of ~160 km on the Mojave segment because transform-parallel extension along the southwestern boundary of the ETR during transrotation produces ~25-40 km of displacement that does not affect offset markers of the Liebre/San Bernadino correlation located northwest of the ETR rotating domain. Reconciliation of these disparate estimates places an important new constraint on the total plate boundary shear that is likely accommodated in the adjacent northern Gulf of California. Global plate circuit models require ~650 km of cumulative Pacific-North America (PAC

Explicitly represented polygon wall boundary model for the explicit MPS method

Science.gov (United States)

Mitsume, Naoto; Yoshimura, Shinobu; Murotani, Kohei; Yamada, Tomonori

2015-05-01

This study presents an accurate and robust boundary model, the explicitly represented polygon (ERP) wall boundary model, to treat arbitrarily shaped wall boundaries in the explicit moving particle simulation (E-MPS) method, which is a mesh-free particle method for strong form partial differential equations. The ERP model expresses wall boundaries as polygons, which are explicitly represented without using the distance function. These are derived so that for viscous fluids, and with less computational cost, they satisfy the Neumann boundary condition for the pressure and the slip/no-slip condition on the wall surface. The proposed model is verified and validated by comparing computed results with the theoretical solution, results obtained by other models, and experimental results. Two simulations with complex boundary movements are conducted to demonstrate the applicability of the E-MPS method to the ERP model.

Measurement and modeling of radiation-induced grain boundary grain boundary segregation in stainless steels

International Nuclear Information System (INIS)

Bruemmer, S.M.; Charlot, L.A.; Simonen, E.P.

1995-08-01

Grain boundary radiation-induced segregation (RIS) in Fe-Ni-Cr stainless alloys has been measured and modelled as a function of irradiation temperature and dose. Heavy-ion irradiation was used to produce damage levels from 1 to 20 displacements per atom (dpa) at temperatures from 175 to 550 degrees C. Measured Fe, Ni, and Cr segregation increased sharply with irradiation dose (from 0 to 5 dpa) and temperature (from 175 to about 350 degrees C). However, grain boundary concentrations did not change significantly as dose or temperatures were further increased. Impurity segregation (Si and P) was also measured, but only Si enrichment appeared to be radiation-induced. Grain boundary Si levels peaked at an intermediate temperature of ∼325 degrees C reaching levels of ∼8 at. %. Equilibrium segregation of P was measured in the high-P alloys, but interfacial concentration did not increase with irradiation exposure. Examination of reported RIS in neutron-irradiated stainless steels revealed similar effects of irradiation dose on grain boundary compositional changes for both major alloying and impurity element's. The Inverse Kirkendall model accurately predicted major alloying element RIS in ion- and neutron-irradiated alloys over the wide range of temperature and dose conditions. In addition, preliminary calculations indicate that the Johnson-Lam model can reasonably estimate grain boundary Si enrichment if back diffusion is enhanced

Thermodynamic Bethe ansatz for boundary sine-Gordon model

International Nuclear Information System (INIS)

Lee, Taejun; Rim, Chaiho

2003-01-01

(R-channel) TBA is elaborated to find the effective central charge dependence on the boundary parameters for the massless boundary sine-Gordon model with the coupling constant (8π)/β 2 =1+λ with λ a positive integer. Numerical analysis of the massless boundary TBA demonstrates that at an appropriate boundary parameter range (cusp point) there exists a singularity crossing phenomena and this effect should be included in TBA to have the right behavior of the effective central charge

Plate boundary deformation of the Pacific plate. Two case studies. (1) Crustal structure of the northwestern Vizcaino block and Gorda escarpment, offshore northern California, and implications for postsubduction deformation of a paleoaccretionary margin. (2) A focused look at the Alpine fault, New Zealand: Seismicity, focal mechanisms and stress observations

Science.gov (United States)

Leitner, Beate

Two examples of Pacific rim plate boundary deformation are presented. In the first part of the thesis crustal models are derived for the northwestern part of the Vizcaino block in California using marine seismic and gravity data collected by the Mendocino Triple Junction Seismic Experiment. A northwest-southeast trending kink in the Moho is imaged and interpreted to have formed under compression by reactivation of preexisting thrust faults in the paleoaccretionary prism at the seaward margin of the Vizcaino block. The study suggests that the deformation resulted from mainly north-south compression between the Pacific-Juan de Fuca plates across the Mendocino transform fault and predates late Pliocene Pacific-North America plate convergence. In the second part, 195 earthquakes recorded during the duration of the Southern Alps Passive Seismic Experiment (SAPSE) are analysed. Precise earthquake locations and focal mechanisms provide unprecedented detail of the seismotectonics in the central South Island. The short term (6 month) SAPSE seismicity is compared with long term (8 years) seismicity recorded by the New Zealand National Seismic network and the Lake Pukaki network. The seismicity rate of the Alpine fault is low, but comparable to locked sections of the San Andreas fault, with large earthquakes expected. Changes of the depth of the seismogenic zone, generally uniform at about 10--12 km, occur only localised over distances smaller than 30 km, suggesting that thermal perturbations must be of similar scale. This implies that the thermal effects of the uplift of the Southern Alps do not change the seismogenic depth significantly and are not in accordance with most of the present thermal models. Both the Hope and Porters Pass fault zones are seismically active and deformation is accommodated near the fault zones and in the adjacent crust. North of Mt Cook, a triangular shaped region along the Alpine fault is characterised by absence of earthquakes. We interpret this

Effects of boundary-layer separation controllers on a desktop fume hood.

Science.gov (United States)

Huang, Rong Fung; Chen, Jia-Kun; Hsu, Ching Min; Hung, Shuo-Fu

2016-10-02

A desktop fume hood installed with an innovative design of flow boundary-layer separation controllers on the leading edges of the side plates, work surface, and corners was developed and characterized for its flow and containment leakage characteristics. The geometric features of the developed desktop fume hood included a rearward offset suction slot, two side plates, two side-plate boundary-layer separation controllers on the leading edges of the side plates, a slanted surface on the leading edge of the work surface, and two small triangular plates on the upper left and right corners of the hood face. The flow characteristics were examined using the laser-assisted smoke flow visualization technique. The containment leakages were measured by the tracer gas (sulphur hexafluoride) detection method on the hood face plane with a mannequin installed in front of the hood. The results of flow visualization showed that the smoke dispersions induced by the boundary-layer separations on the leading edges of the side plates and work surface, as well as the three-dimensional complex flows on the upper-left and -right corners of the hood face, were effectively alleviated by the boundary-layer separation controllers. The results of the tracer gas detection method with a mannequin standing in front of the hood showed that the leakage levels were negligibly small (≤0.003 ppm) at low face velocities (≥0.19 m/s).

FINITE ELEMENT MODELING OF THIN CIRCULAR SANDWICH PLATES DEFLECTION

Directory of Open Access Journals (Sweden)

K. S. Kurachka

2014-01-01

Full Text Available A mathematical model of a thin circular sandwich plate being under the vertical load is proposed. The model employs the finite element method and takes advantage of an axisymmetric finite element that leads to the small dimension of the resulting stiffness matrix and sufficient accuracy for practical calculations. The analytical expressions for computing local stiffness matrices are found, which can significantly speed up the process of forming the global stiffness matrix and increase the accuracy of calculations. A software is under development and verification. The discrepancy between the results of the mathematical model and those of analytical formulas for homogeneous thin circularsandwich plates does not exceed 7%.

Influence of boundary conditions on the response of multilayered plates with cohesive interfaces and delaminations using a homogenized approach

Directory of Open Access Journals (Sweden)

R. Massabò

2014-07-01

Full Text Available Stress and displacement fields in multilayered composites with interfacial imperfections, such as imperfect bonding of the layers or delaminations, or where the plies are separated by thin interlayers allowing relative motion, have large variations in the thickness, with characteristic zigzag patterns and jumps at the layer interfaces. These effects are well captured by a model recently formulated by the author for multilayered plates with imperfect interfaces and affine interfacial traction laws (Massabò & Campi, Meccanica, 2014, in press; Compos Struct, 2014, 116, 311-324. The model defines a homogenized displacement field, which satisfies interfacial continuity, and uses a variational technique to derive equilibrium equations depending on only six generalized displacement functions, for any arbitrary numbers of layers and interfaces. The model accurately predicts stresses and displacements in simply supported, highly anisotropic, thick plates with continuous, sliding interfaces. In this paper the model is applied to wide plates with clamped edges and some inconsistencies, which have been noted in the literature for models based on similar approaches and have limited their utilization, are explained. A generalized transverse shear force is introduced as the gross stress resultant which is directly related to the bending moment in the equilibrium equations of multilayered structures with imperfect interfaces and substitutes for the shear force of single-layer theory. An application to a delaminated wide plate highlights the potential and limitations of the proposed model for the solution of fracture mechanics problems.

Study of effect of a smooth hump on hypersonic boundary layer instability

Science.gov (United States)

Park, Donghun; Park, Seung O.

2016-12-01

Effect of a two-dimensional smooth hump on linear instability of hypersonic boundary layer is studied by using parabolized stability equations. Linear evolution of mode S over a hump is analyzed for Mach 4.5 and 5.92 flat plate and Mach 7.1 sharp cone boundary layers. Mean flow for stability analysis is obtained by solving the parabolized Navier-Stokes equations. Hump with height smaller than local boundary layer thickness is considered. The case of flat plate and sharp cone without the hump are also studied to provide comparable data. For flat plate boundary layers, destabilization and stabilization effect is confirmed for hump located at upstream and downstream of synchronization point, respectively. Results of parametric studies to examine the effect of hump height, location, etc., are also given. For sharp cone boundary layer, stabilization influence of hump is also identified for a specific range of frequency. Stabilization influence of hump on convective instability of mode S is found to be a possible cause of previous experimental observations of delaying transition in hypersonic boundary layers.

Boundary element method for modelling creep behaviour

International Nuclear Information System (INIS)

Zarina Masood; Shah Nor Basri; Abdel Majid Hamouda; Prithvi Raj Arora

2002-01-01

A two dimensional initial strain direct boundary element method is proposed to numerically model the creep behaviour. The boundary of the body is discretized into quadratic element and the domain into quadratic quadrilaterals. The variables are also assumed to have a quadratic variation over the elements. The boundary integral equation is solved for each boundary node and assembled into a matrix. This matrix is solved by Gauss elimination with partial pivoting to obtain the variables on the boundary and in the interior. Due to the time-dependent nature of creep, the solution has to be derived over increments of time. Automatic time incrementation technique and backward Euler method for updating the variables are implemented to assure stability and accuracy of results. A flowchart of the solution strategy is also presented. (Author)

A new plate tectonic concept for the eastern-most Mediterranean

Science.gov (United States)

Huebscher, C.; McGrandle, A.; Scaife, G.; Spoors, R.; Stieglitz, T.

2012-04-01

Owing to the seismogenic faults bordering the Levant-Sinai realm and the discovery of giant gas reservoirs in the marine Levant Basin the scientific interest in this tectonically complex setting increased in recent years. Here we provide a new model for the Levant Basin architecture and adjacent plate boundaries emphasizing the importance of industrial seismic data for frontier research in earth science. PSDM seismics, residual gravity and depth to basement maps give a clear line of evidence that the Levant Basin, formerly considered as a single tectonic entity, is divided into two different domains. Highly stretched continental crust in the southern domain is separated from deeper and presumably Tethyan oceanic crust in the north. A transform continuing from southwest Cyprus to the Carmel Fault in northern Israel is considered as the boundary. If this interpretation holds, the Carmel-Cyprus Transform represents a yet unknown continent-ocean boundary in the eastern Mediterranean, thus adding new constrains for the Mediterranean plate tectonic puzzle. The Eratosthenes Seamount, considered as the spearhead of incipient continental collision in the eastern Mediterranean, is interpreted as a carbonate platform that developed above a volcanic basement. NW-SE trending strike-slip faults are abundant in the entire Levant region. Since this trend also shapes the topography of the Levant hinterland including Quaternary deposits their recent tectonic activity is quite likely. Thus, our study supports previous studies which attributed the evolution of submarine canyons and Holocene triggering of mass failures not only to salt tectonics or depositional processes, but also to active plate-tectonics.

Numerical Investigation of Wall Cooling and Suction Effects on Supersonic Flat-Plate Boundary Layer Transition Using Large Eddy Simulation

Directory of Open Access Journals (Sweden)

Suozhu Wang

2015-02-01

Full Text Available Reducing friction resistance and aerodynamic heating has important engineering significance to improve the performances of super/hypersonic aircraft, so the purpose of transition control and turbulent drag reduction becomes one of the cutting edges in turbulence research. In order to investigate the influences of wall cooling and suction on the transition process and fully developed turbulence, the large eddy simulation of spatially evolving supersonic boundary layer transition over a flat-plate with freestream Mach number 4.5 at different wall temperature and suction intensity is performed in the present work. It is found that the wall cooling and suction are capable of changing the mean velocity profile within the boundary layer and improving the stability of the flow field, thus delaying the onset of the spatial transition process. The transition control will become more effective as the wall temperature decreases, while there is an optimal wall suction intensity under the given conditions. Moreover, the development of large-scale coherent structures can be suppressed effectively via wall cooling, but wall suction has no influence.

Experimental Fracture Model versus Osteotomy Model in Metacarpal Bone Plate Fixation

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S. Ochman

2011-01-01

Full Text Available Introduction. Osteotomy or fracture models can be used to evaluate mechanical properties of fixation techniques of the hand skeleton in vitro. Although many studies make use of osteotomy models, fracture models simulate the clinical situation more realistically. This study investigates monocortical and bicortical plate fixation on metacarpal bones considering both aforementioned models to decide which method is best suited to test fixation techniques. Methods. Porcine metacarpal bones (=40 were randomized into 4 groups. In groups I and II bones were fractured with a modified 3-point bending test. The intact bones represented a further control group to which the other groups after fixation were compared. In groups III and IV a standard osteotomy was carried out. Bones were fixated with plates monocortically (group I, III and bicortically (group II, IV and tested for failure. Results. Bones fractured at a mean maximum load of 482.8 N ± 104.8 N with a relative standard deviation (RSD of 21.7%, mean stiffness was 122.3 ± 35 N/mm. In the fracture model, there was a significant difference (=0.01 for maximum load of monocortically and bicortically fixed bones in contrast to the osteotomy model (=0.9. Discussion. In the fracture model, because one can use the same bone for both measurements in the intact state and the bone-plate construct states, the impact of inter-individual differences is reduced. In contrast to the osteotomy model there are differences between monocortical and bicortical fixations in the fracture model. Thus simulation of the in vivo situation is better and seems to be suitable for the evaluation of mechanical properties of fixation techniques on metacarpals.

Benthic boundary layer modelling studies

International Nuclear Information System (INIS)

Richards, K.J.

1984-01-01

A numerical model has been developed to study the factors which control the height of the benthic boundary layer in the deep ocean and the dispersion of a tracer within and directly above the layer. This report covers tracer clouds of horizontal scales of 10 to 100 km. The dispersion of a tracer has been studied in two ways. Firstly, a number of particles have been introduced into the flow. The trajectories of these particles provide information on dispersion rates. For flow conditions similar to those observed in the abyssal N.E. Atlantic the diffusivity of a tracer was found to be 5 x 10 6 cm 2 s -1 for a tracer within the boundary layer and 8 x 10 6 cm 2 s -1 for a tracer above the boundary layer. The results are in accord with estimates made from current meter measurements. The second method of studying dispersion was to calculate the evolution of individual tracer clouds. Clouds within and above the benthic boundary layer often show quite different behaviour from each other although the general structure of the clouds in the two regions were found to have no significant differences. (author)

Modelling stable atmospheric boundary layers over snow

NARCIS (Netherlands)

Sterk, H.A.M.

2015-01-01

Thesis entitled:

Modelling Stable Atmospheric Boundary Layers over Snow

H.A.M. Sterk

Wageningen, 29th of April, 2015

Summary

The emphasis of this thesis is on the understanding and forecasting of the Stable Boundary Layer (SBL) over snow-covered surfaces. SBLs

Computational Model for Impact-Resisting Critical Thickness of High-Speed Machine Outer Protective Plate

Science.gov (United States)

Wu, Huaying; Wang, Li Zhong; Wang, Yantao; Yuan, Xiaolei

2018-05-01

The blade or surface grinding blade of the hypervelocity grinding wheel may be damaged due to too high rotation rate of the spindle of the machine and then fly out. Its speed as a projectile may severely endanger the field persons. Critical thickness model of the protective plate of the high-speed machine is studied in this paper. For easy analysis, the shapes of the possible impact objects flying from the high-speed machine are simplified as sharp-nose model, ball-nose model and flat-nose model. Whose front ending shape to represent point, line and surface contacting. Impact analysis based on J-C model is performed for the low-carbon steel plate with different thicknesses in this paper. One critical thickness computational model for the protective plate of high-speed machine is established according to the damage characteristics of the thin plate to get relation among plate thickness and mass, shape and size and impact speed of impact object. The air cannon is used for impact test. The model accuracy is validated. This model can guide identification of the thickness of single-layer outer protective plate of a high-speed machine.

Twisted quantum double model of topological order with boundaries

Science.gov (United States)

Bullivant, Alex; Hu, Yuting; Wan, Yidun

2017-10-01

We generalize the twisted quantum double model of topological orders in two dimensions to the case with boundaries by systematically constructing the boundary Hamiltonians. Given the bulk Hamiltonian defined by a gauge group G and a 3-cocycle in the third cohomology group of G over U (1 ) , a boundary Hamiltonian can be defined by a subgroup K of G and a 2-cochain in the second cochain group of K over U (1 ) . The consistency between the bulk and boundary Hamiltonians is dictated by what we call the Frobenius condition that constrains the 2-cochain given the 3-cocyle. We offer a closed-form formula computing the ground-state degeneracy of the model on a cylinder in terms of the input data only, which can be naturally generalized to surfaces with more boundaries. We also explicitly write down the ground-state wave function of the model on a disk also in terms of the input data only.

Assessing the role of slab rheology in coupled plate-mantle convection models

Science.gov (United States)

Bello, Léa; Coltice, Nicolas; Tackley, Paul J.; Dietmar Müller, R.; Cannon, John

2015-11-01

Reconstructing the 3D structure of the Earth's mantle has been a challenge for geodynamicists for about 40 yr. Although numerical models and computational capabilities have substantially progressed, parameterizations used for modeling convection forced by plate motions are far from being Earth-like. Among the set of parameters, rheology is fundamental because it defines in a non-linear way the dynamics of slabs and plumes, and the organization of lithosphere deformation. In this study, we evaluate the role of the temperature dependence of viscosity (variations up to 6 orders of magnitude) and the importance of pseudo-plasticity on reconstructing slab evolution in 3D spherical models of convection driven by plate history models. Pseudo-plasticity, which produces plate-like behavior in convection models, allows a consistent coupling between imposed plate motions and global convection, which is not possible with temperature-dependent viscosity alone. Using test case models, we show that increasing temperature dependence of viscosity enhances vertical and lateral coherence of slabs, but leads to unrealistic slab morphologies for large viscosity contrasts. Introducing pseudo-plasticity partially solves this issue, producing thin laterally and vertically more continuous slabs, and flat subduction where trench retreat is fast. We evaluate the differences between convection reconstructions employing different viscosity laws to be very large, and similar to the differences between two models with the same rheology but using two different plate histories or initial conditions.

Buckling of Flat Thin Plates under Combined Loading

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Ion DIMA

2015-03-01

Full Text Available This article aims to provide a quick methodology to determine the critical values of the forces applied to the central plane of a flat isotropic plate at which a change to the stable configuration of equilibrium occurs. Considering the variety of shapes, boundary conditions and loading combinations, the article does not intend to make an exhaustive presentation of the plate buckling. As an alternative, there will be presented only the most used configurations such as: rectangular flat thin plates, boundary conditions with simply supported (hinged or clamped (fixed edges, combined loadings with single compression or single shear or combination between them, compression and shear, with or without transverse loading, encountered at wings and control surfaces shell of fin and rudder or stabilizer and elevator. The reserve factor and the critical stresses will be calculated using comparatively two methods, namely the methodology proposed by the present article and ASSIST 6.6.2.0 – AIRBUS France software, a dedicated software to local calculations, for a simply supported plate under combined loading, compression on the both sides and shear.

Biomechanical comparison of double-row locking plates versus single- and double-row non-locking plates in a comminuted metacarpal fracture model.

Science.gov (United States)

Gajendran, Varun K; Szabo, Robert M; Myo, George K; Curtiss, Shane B

2009-12-01

Open or unstable metacarpal fractures frequently require open reduction and internal fixation. Locking plate technology has improved fixation of unstable fractures in certain settings. In this study, we hypothesized that there would be a difference in strength of fixation using double-row locking plates compared with single- and double-row non-locking plates in comminuted metacarpal fractures. We tested our hypothesis in a gap metacarpal fracture model simulating comminution using fourth-generation, biomechanical testing-grade composite sawbones. The metacarpals were divided into 6 groups of 15 bones each. Groups 1 and 4 were plated with a standard 6-hole, 2.3-mm plate in AO fashion. Groups 2 and 5 were plated with a 6-hole double-row 3-dimensional non-locking plate with bicortical screws aimed for convergence. Groups 3 and 6 were plated with a 6-hole double-row 3-dimensional locking plate with unicortical screws. The plated metacarpals were then tested to failure against cantilever apex dorsal bending (groups 1-3) and torsion (groups 4-6). The loads to failure in groups 1 to 3 were 198 +/- 18, 223 +/- 29, and 203 +/- 19 N, respectively. The torques to failure in groups 4 to 6 were 2,033 +/- 155, 3,190 +/- 235, and 3,161 +/- 268 N mm, respectively. Group 2 had the highest load to failure, whereas groups 5 and 6 shared the highest torques to failure (p row plates had equivalent bending and torsional stiffness, significantly higher than observed for the single-row non-locking plate. No other statistical differences were noted between groups. When subjected to the physiologically relevant forces of apex dorsal bending and torsion in a comminuted metacarpal fracture model, double-row 3-dimensional non-locking plates provided superior stability in bending and equivalent stability in torsion compared with double-row 3-dimensional locking plates, whereas single-row non-locking plates provided the least stability.

Boundary rings and N=2 coset models

International Nuclear Information System (INIS)

Lerche, W.; Walcher, J.

2002-01-01

We investigate boundary states of N=2 coset models based on Grassmannians Gr(n,n+k), and find that the underlying intersection geometry is given by the fusion ring of U(n). This is isomorphic to the quantum cohomology ring of Gr(n,n+k+1), which in turn can be encoded in a 'boundary' superpotential whose critical points correspond to the boundary states. In this way the intersection properties can be represented in terms of a soliton graph that forms a generalized, Z n+k+1 symmetric McKay quiver. We investigate the spectrum of bound states and find that the rational boundary CFT produces only a small subset of the possible quiver representations

Drag reduction using wrinkled surfaces in high Reynolds number laminar boundary layer flows

Science.gov (United States)

Raayai-Ardakani, Shabnam; McKinley, Gareth H.

2017-09-01

Inspired by the design of the ribbed structure of shark skin, passive drag reduction methods using stream-wise riblet surfaces have previously been developed and tested over a wide range of flow conditions. Such textures aligned in the flow direction have been shown to be able to reduce skin friction drag by 4%-8%. Here, we explore the effects of periodic sinusoidal riblet surfaces aligned in the flow direction (also known as a "wrinkled" texture) on the evolution of a laminar boundary layer flow. Using numerical analysis with the open source Computational Fluid Dynamics solver OpenFOAM, boundary layer flow over sinusoidal wrinkled plates with a range of wavelength to plate length ratios ( λ / L ), aspect ratios ( 2 A / λ ), and inlet velocities are examined. It is shown that in the laminar boundary layer regime, the riblets are able to retard the viscous flow inside the grooves creating a cushion of stagnant fluid that the high-speed fluid above can partially slide over, thus reducing the shear stress inside the grooves and the total integrated viscous drag force on the plate. Additionally, we explore how the boundary layer thickness, local average shear stress distribution, and total drag force on the wrinkled plate vary with the aspect ratio of the riblets as well as the length of the plate. We show that riblets with an aspect ratio of close to unity lead to the highest reduction in the total drag, and that because of the interplay between the local stress distribution on the plate and stream-wise evolution of the boundary layer the plate has to exceed a critical length to give a net decrease in the total drag force.

Modelling of plate-out under gas-cooled reactor (GCR) accident conditions

International Nuclear Information System (INIS)

Taig, A.R.

1981-01-01

The importance of plate-out in mitigating consequences of gas-cooled reactor accidents, and its place in assessing these consequences, are discussed. The data requirements of a plate-out modelling program are discussed, and a brief description is given of parallel work programs on thermal/hydraulic reactor behaviour and fuel modelling, both of which will provide inputs to the plate-out program under development. The representation of a GCR system used in SRD studies is presented, and the equations governing iodine adsorption, desorption and transport round the circuit are derived. The status of SRD's plate-out program is described, and the type of sensitivity studies to be undertaken with the partially-developed computer program in order to identify the most useful lines for future research is discussed. (author)

Cretaceous to present kinematics of the Indian, African and Seychelles plates

Science.gov (United States)

Eagles, Graeme; Hoang, Ha H.

2014-01-01

An iterative inverse model of seafloor spreading data from the Mascarene and Madagascar basins and the flanks of the Carlsberg Ridge describes a continuous history of Indian-African Plate divergence since 84 Ma. Visual-fit modelling of conjugate magnetic anomaly data from near the Seychelles platform and Laxmi Ridge documents rapid rotation of a Seychelles Plate about a nearby Euler pole in Palaeocene times. As the Euler pole migrated during this rotation, the Amirante Trench on the western side of the plate accommodated first convergence and later divergence with the African Plate. The unusual present-day morphology of the Amirante Trench and neighbouring Amirante Banks can be related to crustal thickening by thrusting and folding during the convergent phase and the subsequent development of a spreading centre with a median valley during the divergent phase. The model fits FZ trends in the north Arabian and east Somali basins, suggesting that they formed in India-Africa Plate divergence. Seafloor fabric in and between the basins shows that they initially hosted a segmented spreading ridge that accommodated slow plate divergence until 71-69 Ma, and that upon arrival of the Deccan-Réunion plume and an increase to faster plate divergence rates in the period 69-65 Ma, segments of the ridge lengthened and propagated. Ridge propagation into the Indian continental margin led first to the formation of the Laxmi Basin, which accompanied extensive volcanism onshore at the Deccan Traps and offshore at the Saurashtra High and Somnath Ridge. A second propagation episode initiated the ancestral Carlsberg Ridge at which Seychelles-India and India-Africa Plate motions were accommodated. With the completion of this propagation, the plate boundaries in the Mascarene Basin were abandoned. Seafloor spreading between this time and the present has been accommodated solely at the Carlsberg Ridge.

Evolution of the Adria-Europe plate boundary in the northern Dinarides: From continent-continent collision to back-arc extension

Science.gov (United States)

Ustaszewski, Kamil; Kounov, Alexandre; Schmid, Stefan M.; Schaltegger, Urs; Krenn, Erwin; Frank, Wolfgang; Fügenschuh, Bernhard

2010-12-01

The Sava Zone of the northern Dinarides is part of the Cenozoic Adria-Europe plate boundary. Here Late Cretaceous subduction of remnants of Meliata-Vardar oceanic lithosphere led to the formation of a suture, across which upper plate European-derived units of Tisza-Dacia were juxtaposed with Adria-derived units of the Dinarides. Late Cretaceous siliciclastic sediments, deposited on the Adriatic plate, were incorporated into an accretionary wedge that evolved during the initial stages of continent-continent collision. Structurally deeper parts of the exposed accretionary wedge underwent amphibolite-grade metamorphism. Grt-Pl-Ms-Bt thermobarometry and multiphase equilibria indicate temperatures between 550°C and 630°C and pressures between 5 and 7 kbar for this event. Peak metamorphic conditions were reached at around 65 Ma. Relatively slow cooling from peak metamorphic conditions throughout most of the Paleogene was possibly induced by hanging wall erosion in conjunction with southwest directed propagation of thrusting in the Dinarides. Accelerated cooling took place in Miocene times, when the Sava Zone underwent substantial extension that led to the exhumation of the metamorphosed units along a low-angle detachment. Footwall exhumation started under greenschist facies conditions and was associated with top-to-the-north tectonic transport, indicating exhumation from below European plate units. Extension postdates the emplacement of a 27 Ma old granitoid that underwent solid-state deformation under greenschist facies conditions. The 40Ar/39Ar sericite and zircon and apatite fission track ages from the footwall allow bracketing this extensional unroofing between 25 and 14 Ma. This extension is hence linked to Miocene rift-related subsidence in the Pannonian basin, which represents a back-arc basin formed due to subduction rollback in the Carpathians.

Effect of leading-edge geometry on boundary-layer receptivity to freestream sound

Science.gov (United States)

Lin, Nay; Reed, Helen L.; Saric, W. S.

1991-01-01

The receptivity to freestream sound of the laminar boundary layer over a semi-infinite flat plate with an elliptic leading edge is simulated numerically. The incompressible flow past the flat plate is computed by solving the full Navier-Stokes equations in general curvilinear coordinates. A finite-difference method which is second-order accurate in space and time is used. Spatial and temporal developments of the Tollmien-Schlichting wave in the boundary layer, due to small-amplitude time-harmonic oscillations of the freestream velocity that closely simulate a sound wave travelling parallel to the plate, are observed. The effect of leading-edge curvature is studied by varying the aspect ratio of the ellipse. The boundary layer over the flat plate with a sharper leading edge is found to be less receptive. The relative contribution of the discontinuity in curvature at the ellipse-flat-plate juncture to receptivity is investigated by smoothing the juncture with a polynomial. Continuous curvature leads to less receptivity. A new geometry of the leading edge, a modified super ellipse, which provides continuous curvature at the juncture with the flat plate, is used to study the effect of continuous curvature and inherent pressure gradient on receptivity.

16 Years, 16 Cruises, 1.6 Billion Soundings: a Compilation of High-Resolution Multibeam Bathymetry of the Active Plate Boundary Along the Chilean Continental Margin

Science.gov (United States)

Weinrebe, W.; Flueh, E. R.; Hasert, M.; Behrmann, J. H.; Voelker, D.; Geersen, J.; Ranero, C. R.; Diaz-Naveas, J. L.

2011-12-01

Chile, a country stranding the active plate boundary between the South-American and the Nazca Plate is afflicted by recurrent earthquakes and hazardous volcanic eruptions. The strongest earthquake ever recorded occurred here, and volcanic hazards are frequent. Consequently, this area has been studied by geoscientists for many years to improve the understanding of subduction zone processes. Swath bathymetry mapping of the ocean floor has proven to bear a large potential for the interpretation of subduction-related processes, such as tectonic deformation of the marine forearc, release and migration of fluids as well as earthquake-triggered mass wasting. Multibeam bathymetry data of 16 major cruises of German, British, and Chilean research vessels recorded between 1995 and December 2010, in total more than 10,000 data files comprising about 1.6 billion soundings, have now been carefully reprocessed, compiled and merged into a unifying set of high-resolution bathymetric maps of the Chilean continental margin from latitude 40°S to 20°S. The imprint of subsurface processes on the surface morphology is well displayed in the case of the Chilean continental margin. The 3,500 km long Chilean convergent margin is not uniform, as various segments with different tectonic characteristics can be distinguished. Major factors that control margin morphology and thus the style of subduction are (1) relief and structure of the incoming oceanic plate, (2) supply of trench sediment, (3) turbidite transport within the trench, and (4) the input of terrigeneous sediments down the continental slope. A major segment boundary occurs at latitude 32°-33° S where the hotspot-related volcanic chain of Juan Fernandez is presently subducting. South of the area of ridge subduction the trench is filled with turbidites, and accretionary ridges develop across the base of the slope along most of the segment, whereas north of this boundary the turbiditic infill is reduced and subduction erosion is

Plate Speed-up and Deceleration during Continental Rifting: Insights from Global 2D Mantle Convection Models.

Science.gov (United States)

Brune, S.; Ulvrova, M.; Williams, S.

2017-12-01

The surface of the Earth is divided into a jigsaw of tectonic plates, some carrrying continents that disperse and aggregate through time, forming transient supercontinents like Pangea and Rodinia. Here, we study continental rifting using large-scale numerical simulations with self-consistent evolution of plate boundaries, where continental break-up emerges spontaneously due to slab pull, basal drag and trench suction forces.We use the StagYY convection code employing a visco-plastic rheology in a spherical annulus geometry. We consider an incompressible mantle under the Boussinesq approximation that is basally and internally heated.We show that continental separation follows a characteristic evolution with three distinctive phases: (1) A pre-rift phase that typically lasts for several hundreds of millions of years with tectonic quiescence in the suture and extensional stresses that are slowly building up. (2) A rift phase that further divides into a slow rift period of several tens of millions of years where stresses continuously increase followed by a rift acceleration period featuring an abrupt stress drop within several millions of years. The speed-up takes place before lithospheric break-up and therefore affects the structural architecture of the rifted margins. (3) The drifting phase with initially high divergence rates persists over tens of millions of years until the system adjust to new conditions and the spreading typically slows down.By illustrating the geodynamic connection between subduction dynamics and rift evolution, our results allow new interpretations of plate tectonic reconstructions. Rift acceleration within the second phase of rifting is compensated by enhanced convergence rates at subduction zones. This model outcome predicts enhanced subduction velocities, e.g. between North America and the Farallon plate during Central Atlantic rifting 200 My ago, or closure of potential back-arc basins such as in the proto-Andean ranges of South America

Boundary scattering in the ϕ{sup 4} model

Energy Technology Data Exchange (ETDEWEB)

Dorey, Patrick [Department of Mathematical Sciences, Durham University,Durham DH1 3LE (United Kingdom); Halavanau, Aliaksei [Department of Theoretical Physics and Astrophysics,BSU, Minsk Independence Avenue 4 (Belarus); Fermi National Laboratory,Pine St. and Kirk Rd., ZIP 60511, Mail Station 221, Batavia, Illinois (United States); Mercer, James [Department of Mathematical Sciences, Durham University,Durham DH1 3LE (United Kingdom); Deloitte MCS Limited,Hill House, 1 Little New Street, London, EC4A 3TR (United Kingdom); Romanczukiewicz, Tomasz [Institute of Physics, Jagiellonian University,Lojasiewicza 11, 30-348 Krakow (Poland); Shnir, Yasha [Department of Theoretical Physics and Astrophysics,BSU, Minsk Independence Avenue 4 (Belarus); BLTP, JINR,141980 Dubna (Russian Federation); Institute of Physics, Oldenburg University,Postfach 2503 D-26111 Oldenburg (Germany)

2017-05-19

We study boundary scattering in the ϕ{sup 4} model on a half-line with a one-parameter family of Neumann-type boundary conditions. A rich variety of phenomena is observed, which extends previously-studied behaviour on the full line to include regimes of near-elastic scattering, the restoration of a missing scattering window, and the creation of a kink or oscillon through the collision-induced decay of a metastable boundary state. We also study the decay of the vibrational boundary mode, and explore different scenarios for its relaxation and for the creation of kinks.

Catalytic reaction in a porous solid subject to a boundary layer flow

Energy Technology Data Exchange (ETDEWEB)

Mihail, R; Teddorescu, C

1978-01-01

A mathematical model of a boundary layer flowing past a catalytic slab was developed which included an analysis of the coupled mass and heat transfer and the heterogeneous chemical reaction. The porous flat plate was used to illustrate the interaction of boundary layer flow with chemical reaction within a porous catalytic body. The model yielded systems of transcendental equations which were solved numerically by means of a superposition integral in connection with a norm reduction procedure. A parametric study was conducted and an analysis of the possible multiplicity of steady states was developed and illustrated for the extreme case of infinite solid thermal conductivity. Tables, diagrams, graphs, and 12 references.

Nested Bethe Ansatz for Spin Ladder Model with Open Boundary Conditions

International Nuclear Information System (INIS)

Wu Junfang; Zhang Chunmin; Yue Ruihong; Li Runling

2005-01-01

The nested Bethe ansatz (BA) method is applied to find the eigenvalues and the eigenvectors of the transfer matrix for spin-ladder model with open boundary conditions. Based on the reflection equation, we find the general diagonal solution, which determines the general boundary interaction in the Hamiltonian. We introduce the spin-ladder model with open boundary conditions. By finding the solution K ± of the reflection equation which determines the nontrivial boundary terms in the Hamiltonian, we diagonalize the transfer matrix of the spin-ladder model with open boundary conditions in the framework of nested BA.

Doubling inequalities for anisotropic plate equations and applications to size estimates of inclusions

International Nuclear Information System (INIS)

Di Cristo, M; Lin, C-L; Morassi, A; Rosset, E; Vessella, S; Wang, J-N

2013-01-01

We prove the upper and lower estimates of the area of an unknown elastic inclusion in a thin plate by one boundary measurement. The plate is made of non-homogeneous linearly elastic material belonging to a general class of anisotropy and the domain of the inclusion is a measurable subset of the plate. The size estimates are expressed in terms of the work exerted by a couple field applied at the boundary and of the induced transversal displacement and its normal derivative taken at the boundary of the plate. The main new mathematical tool is a doubling inequality for solutions to fourth-order elliptic equations whose principal part P(x, D) is the product of two second-order elliptic operators P 1 (x, D), P 2 (x, D) such that P 1 (0, D) = P 2 (0, D). The proof of the doubling inequality is based on the Carleman method, a sharp three-spheres inequality and a bootstrapping argument. (paper)

Surface capillary currents: Rediscovery of fluid-structure interaction by forced evolving boundary theory

Science.gov (United States)

Wang, Chunbai; Mitra, Ambar K.

2016-01-01

Any boundary surface evolving in viscous fluid is driven with surface capillary currents. By step function defined for the fluid-structure interface, surface currents are found near a flat wall in a logarithmic form. The general flat-plate boundary layer is demonstrated through the interface kinematics. The dynamics analysis elucidates the relationship of the surface currents with the adhering region as well as the no-slip boundary condition. The wall skin friction coefficient, displacement thickness, and the logarithmic velocity-defect law of the smooth flat-plate boundary-layer flow are derived with the advent of the forced evolving boundary method. This fundamental theory has wide applications in applied science and engineering.

Weak Tectono-Magmatic Relationships along an Obliquely Convergent Plate Boundary: Sumatra, Indonesia

Directory of Open Access Journals (Sweden)

Valerio Acocella

2018-02-01

Full Text Available The tectono-magmatic relationships along obliquely convergent plate boundaries, where strain partitioning promotes strike-slip structures along the volcanic arc, are poorly known. Here it is unclear if and, in case, how the strike-slip structures control volcanic processes, distribution and size. To better define the possible tectono-magmatic relationships along strike-slip arcs, we merge available information on the case study of Sumatra (Indonesia with field structural data. The Sumatra arc (entire volcanic belt consists of 48 active volcanoes. Of these, 46% lie within 10 km from the dextral Great Sumatra Fault (GSF, which carries most horizontal displacement on the overriding plate, whereas 27% lie at >20 km from the GSF. Among the volcanoes at <10 km from GSF, 48% show a possible structural relation to the GSF, whereas only 28% show a clear structural relation, lying in pull-aparts or releasing bends; these localized areas of transtension (local extensional zone do not develop magmatic segments. There is no relation between the GSF along-strike slip rate variations and the volcanic productivity. The preferred N30°-N40°E volcano alignment and elongation are subparallel to the convergence vector or to the GSF. The structural field data, collected in the central and southern GSF, show, in addition to the dextral motions along NW-SE to N-S striking faults, also normal motions (extending WNW-ESE or NE-SW, suggesting local reactivations of the GSF. Overall, the collected data suggest a limited tectonic control on arc volcanism. The tectonic control is mostly expressed by the mean depth of the slab surface below the volcanoes (130 ± 20 km and, subordinately, local extension along the GSF. The latter, when WNW-ESE oriented (more common, may be associated with the overall tectonic convergence, as suggested by the structural data; conversely, when NE-SW oriented (less common, the extension may result from co- and post-seismic arc normal extension

Modelling classroom conditions with different boundary conditions

DEFF Research Database (Denmark)

Marbjerg, Gerd Høy; Jeong, Cheol-Ho; Brunskog, Jonas

2014-01-01

A model that combines image source modelling and acoustical radiosity with complex boundary condition, thus including phase shifts on reflection has been developed. The model is called PARISM (Phased Acoustical Radiosity and Image Source Model). It has been developed in order to be able to model...

Origin of Starting Earthquakes under Complete Coupling of the Lithosphere Plates and a Base

Science.gov (United States)

Babeshko, V. A.; Evdokimova, O. V.; Babeshko, O. M.; Zaretskaya, M. V.; Gorshkova, E. M.; Mukhin, A. S.; Gladskoi, I. B.

2018-02-01

The boundary problem of rigid coupling of lithospheric plates modeled by Kirchhoff plates with a base represented by a three-dimensional deformable layered medium is considered. The possibility of occurrence of a starting earthquake in such a block structure is investigated. For this purpose, two states of this medium in the static mode are considered. In the first case, the semi-infinite lithospheric plates in the form of half-planes are at a distance so that the distance between the end faces is different from zero. In the second case, the lithospheric plates come together to zero spacing between them. Calculations have shown that in this case more complex movements of the Earth's surface are possible. Among such movements are the cases described in our previous publications [1, 2].

A Mathematical Model for the Non-Stationary Process of Compression Molding of Plates from Granulate of Thermoplastic Composites

Directory of Open Access Journals (Sweden)

Vladimir N. Vodyakov

2017-12-01

Full Text Available Introduction: Mathematical modeling allows assigning optimal parameters for the process of compression molding of plates and calculating the dimensions of the mold without costly and long-term experiments. The options ensure the required precision of pressing. The disadvantages of the known models are the assumptions about the process isothermicity and independence of the thermal-physical coefficients from temperature. The models do not take into account the dependence of the pressure in the cavity of the mold on the excess of the melt; the problem of calculating the dimensions of the mold cavity for given plate dimensions is not posed. The known models do not give a complete description of all stages of the process. The aim of this paper is to develop a perfect mathematical model without limitations for the compression molding of plates from a granulate of highly filled thermoplastic composites. Materials and Methods: The paper proposes a non-stationary mathematical model. The model takes into account the presence of physical states transitions and dependence of the thermophysical characteristics of composites on temperature. The model is based on the known equations of thermal physics and continuum mechanics. Results: Initial and boundary conditions, rheological equations, systems of equations for the material, thermal, and power balance are determined for three stages of the process. The calculation problems are determined too. A program of iterative numerical calculation has been developed because of the resulting system of equations has no analytical solution. A convergence of experimental and theoretical results with the correlation coefficient confirms the adequacy of the developed mathematical model and the calculation program. Discussion and Conclusions: The results of the study allow calculating the dimensions of the mold cavity, the initial granulate required mass, technological losses, the time functions of pressure and temperature

DNS and the theory of receptivity of a supersonic boundary layer to free-stream disturbances

International Nuclear Information System (INIS)

Soudakov, Vitaly; Fedorov, Alexander; Ryzhov, Alexander

2011-01-01

Direct numerical simulation (DNS) of receptivity of a boundary layer over flat plate is carried out. The free stream Mach number is equal to 6. The following two-dimensional disturbances are introduced into the free-stream flow: fast and slow acoustic waves, temperature spottiness. A theoretical model describing the excitation of unstable waves in the boundary layer is developed using the biorthogonal eigenfunction decomposition method. The DNS results agree with the theoretical predictions.

Fused integrable lattice models with quantum impurities and open boundaries

International Nuclear Information System (INIS)

Doikou, Anastasia

2003-01-01

The alternating integrable spin chain and the RSOS(q 1 ,q 2 ;p) model in the presence of a quantum impurity are investigated. The boundary free energy due to the impurity is derived, the ratios of the corresponding g functions at low and high temperature are specified and their relevance to boundary flows in unitary minimal and generalized coset models is discussed. Finally, the alternating spin chain with diagonal and non-diagonal integrable boundaries is studied, and the corresponding boundary free energy and g functions are derived

Residual stress measurement of EB-welded plates with contour method. Part 2: FEM analysis of contour profiles

International Nuclear Information System (INIS)

Romppanen, A.-J.; Immonen, E.

2013-12-01

The residual stresses formed as a result of Electronic Beam welding (EB-welding) in copper are investigated by Posiva. In the present study, residual stresses of EB-welded copper plates were studied with contour method. In the method eleven copper plates (X436 - X440 and X453 - X458) were cut in half with wire electric discharge machining (EDM) after which the deformation due to stress relaxation was measured with coordinate measurement system. The measured data was then used as boundary displacement data for the FEM analyses, in which the corresponding residual stresses were calculated. Before giving the corresponding displacement boundary conditions to the FE models, the deformation data was processed and smoothed appropriately. The residual stress levels of the copper plates were found to be around 40 - 55 MPa at maximum. This corresponds to other reported residual stress measurements and current state of knowledge with this material in Posiva. (orig.)

Modeling of parallel-plate regenerators with non-uniform plate distributions

DEFF Research Database (Denmark)

Jensen, Jesper Buch; Engelbrecht, Kurt; Bahl, Christian Robert Haffenden

2010-01-01

plate spacing distributions are presented in order to understand the impact of spacing non-uniformity. Simulations of more realistic distributions where the plate spacings follow normal distributions are then discussed in order to describe the deviation of the performance of a regenerator relative...

Three-dimensional inverse transient heat transfer analysis of thick functionally graded plates

Energy Technology Data Exchange (ETDEWEB)

Haghighi, M.R. Golbahar; Malekzadeh, P. [Department of Mechanical Engineering, School of Engineering, Persian Gulf University, Bushehr 75168 (Iran); Eghtesad, M. [Department of Mechanical Engineering, School of Engineering, Shiraz University, Shiraz 71348-51154 (Iran); Necsulescu, D.S. [Department of Mechanical Engineering, Faculty of Engineering, University of Ottawa, Ottawa, Ontario (Canada)

2009-03-15

In this paper, a three-dimensional transient inverse heat conduction (IHC) procedure is presented to estimate the unknown boundary heat flux of thick functionally graded (FG) plates. For this purpose, the conjugate gradient method (CGM) in conjunction with adjoint problem is used. A recently developed three-dimensional efficient hybrid method is employed to solve variable-coefficient initial-boundary-value differential equations of direct problem as a part of the inverse solution. The accuracy of the inverse analysis is examined by simulating the exact and noisy data for problems with different types of boundary conditions and material properties. In addition to rectangular domain, skew plates are considered. The results obtained show good accuracy for the estimation of boundary heat fluxes. (author)

Free vibration analysis of corroded steel plates

Energy Technology Data Exchange (ETDEWEB)

Eslami-Majd, Alireza; Rahbar-Ranji, Ahmad [AmirKabir University of Technology, Tehran (Iran, Islamic Republic of)

2014-06-15

Vibration analysis of unstiffened/stiffened plates has long been studied due to its importance in the design and condition assessments of ship and offshore structures. Corrosion is inevitable in steel structures and has been so far considered in strength analysis of structures. We studied the free vibration of pitted corroded plates with simply supported boundary conditions. Finite element analysis, with ABAQUS, was used to determine the natural frequencies and mode shapes of corroded plates. Influential parameters including plate aspect ratio, degree of pit, one-sided/both-sided corroded plate, and different corrosion patterns were investigated. By increasing the degree of corrosion, reduction of natural frequency increases. Plate aspect ratio and plate dimensions have no influence on reduction of natural frequency. Different corrosion patterns on the surface of one-sided corroded plates have little influence on reduction of natural frequency. Ratio of pit depth over plate thickness has no influence on the reduction of natural frequency. The reduction of natural frequency in both-sided corroded plates is higher than one-sided corroded plates with the same amount of total corrosion loss. Mode shapes of vibration would change due to corrosion, except square mode shapes.

LOWLID FORMATION AND PLATE TECTONICS ON EXOPLANETS

Science.gov (United States)

Stamenkovic, V.; Noack, L.; Breuer, D.

2009-12-01

The last years of astronomical observation have opened the doors to a universe filled with extrasolar planets. Detection techniques still only offer the possibility to detect mainly Super-Earths above five Earth masses. But detection techniques do steadily improve and are offering the possibility to detect even smaller planets. The observations show that planets seem to exist in many possible sizes just as the planets and moons of our own solar system do. It is only a natural question to ask if planetary mass has an influence on some key habitability factors such as on plate tectonics, allowing us to test which exoplanets might be more likely habitable than others, and allowing us to understand if plate tectonics on Earth is a stable or a critical, instable process that could easily be perturbed. Here we present results derived from 1D parameterized thermal evolution and 2D/3D computer models, showing how planetary mass influences the propensity of plate tectonics for planets with masses ranging from 0.1 to 10 Earth masses. Lately [2, 3] studied the effect of planetary mass on the ability to break plates and hence initiate plate tectonics - but both derived results contradictory to the other. We think that one of the reasons why both studies [2, 3] are not acceptable in their current form is partly due to an oversimplification. Both treated viscosity only temperature-dependent but neglected the effect pressure has on enlarging the viscosity in the deep mantle. More massive planets have therefore a stronger pressure-viscosity-coupling making convection at high pressures sluggish or even impossible. For planets larger than two Earth masses we observe that a conductive lid (termed low-lid) forms above the core-mantle boundary and thus reduces the effective convective part of the mantle when including a pressure-dependent term into the viscosity laws as shown in [1]. Moreover [2, 3] use time independent steady state models neglecting the fact that plate tectonics is a

Biomechanical study: resistance comparison of posterior antiglide plate and lateral plate on synthetic bone models simulating Danis-Weber B malleolar fractures

Directory of Open Access Journals (Sweden)

Bruna Buscharino

2013-06-01

Full Text Available OBJECTIVE : The purpose of this study was to compare different positions of plates in lateral malleolar Danis-Weber B fractures on synthetic bone: a lateral plate and a posterior antiglide plate. METHODS : Short oblique fractures of distal fibula at the level of the syndesmosys were simulated with a fibular osteotomy in sixteen synthetic fibula bones (Synbone®. Eight fractures were fixed with lateral plating associated with an independent lag screw, and the other eight were fixed with posterior antiglide plating with a lag screw through the plate. A strain gage was installed at the center of each plate at the osteotomy site. Supination and external rotation forces were applied to each of the two groups at the bend. RESULTS : The lateral position plate group suffered more deformity in response to supination forces compared to the group with the posterior antiglide plate, but this result was not statistically significant. In the tests with external rotation forces, the posterior antiglide plating group had significantly higher resistance (p < 0.05. CONCLUSION : When subjected to external rotation forces, osteosynthesis with posterior antiglide plate models simulating type B fractures of the lateral malleolus of the ankle is more resistant than that of the neutralization plate.

Large scale deformation of the oceanic lithosphere: insights from numerical modeling of the Indo-Australian intraplate deformation

Science.gov (United States)

Royer, J.; Brandon, V.

2011-12-01

The large-scale deformation observed in the Indo-Australian plate seems to challenge tenets of plate tectonics: plate rigidity and narrow oceanic plate boundaries. Its distribution along with kinematic data inversions however suggest that the Indo-Australian plate can be viewed as a composite plate made of three rigid component plates - India, Capricorn, Australia - separated by wide and diffuse boundaries either extensional or compressional. We tested this model using the SHELLS numerical code (Kong & Bird, 1995) where the Indo-Australian plate was meshed into 5281 spherical triangular finite elements. Model boundary conditions are defined only by the plate velocities of the rigid parts of the Indo-Australian plate relative to their neighboring plates. Different plate velocity models were tested. From these boundary conditions, and taking into account the age of the lithosphere, seafloor topography, and assumptions on the rheology of the oceanic lithosphere, SHELLS predicts strain rates within the plate. We also tested the role of fossil fracture zones as potential lithospheric weaknesses. In a first step, we considered different component plate pairs (India/Capricorn, Capricorn/Australia, India/Australia). Since the limits of their respective diffuse boundary (i.e. the limits of the rigid component plates) are not known, we let the corresponding edge free. In a second step, we merged the previous meshes to consider the whole Indo-Australian plate. In this case, the velocities on the model boundaries are all fully defined and were set relative to the Capricorn plate. Our models predict deformation patterns very consistent with that observed. Pre-existing structures of the lithosphere play an important role in the intraplate deformation and its distribution. The Chagos Bank focuses the extensional deformation between the Indian and Capricorn plates. Reactivation of fossil fracture zones may accommodate large part of the deformation both in extensional areas, off

Most-Critical Transient Disturbances in an Incompressible Flat-Plate Boundary Layer

Science.gov (United States)

Monschke, Jason; White, Edward

2015-11-01

Transient growth is a linear disturbance growth mechanism that plays a key role in roughness-induced boundary-layer transition. It occurs when superposed stable, non-orthogonal continuous spectrum modes experience algebraic disturbance growth followed by exponential decay. Algebraic disturbance growth can modify the basic state making it susceptible to secondary instabilities rapidly leading to transition. Optimal disturbance theory was developed to model the most-dangerous disturbances. However, evidence suggests roughness-induced transient growth is sub-optimal yet leads to transition earlier than optimal theory suggests. This research computes initial disturbances most unstable to secondary instabilities to further develop the applicability of transient growth theory to surface roughness. The main approach is using nonlinear adjoint optimization with solutions of the parabolized Navier-Stokes and BiGlobal stability equations. Two objective functions were considered: disturbance kinetic energy growth and sinuous instability growth rate. The first objective function was used as validation of the optimization method. Counter-rotating streamwise vortices located low in the boundary layer maximize the sinuous instability growth rate. The authors would like to acknowledge NASA and the AFOSR for funding this work through AFOSR Grant FA9550-09-1-0341.

Coastal boundary layers in ocean modelling: an application to the Adriatic Sea

International Nuclear Information System (INIS)

Malanotte Rizzoli, P.; Dell'Orto, F.

1981-01-01

Boundary layers play an important role in modelling geophysical fluid-dynamical flows, in as much as they constitute regions of ageostrophic dynamics in which the physical balances characterizing the main interior of the water mass break down. A short synopsis is given of important boundary layers in ocean circulation modelling with specific emphasis drawn upon side wall boundary layers, namely those adjacent to the coastlines of the considered basin. Application of boundary layer analysis is thereafter made for one specific phenomenological situation, namely the Northern Adriatic Sea and the problem posed by its wintertime seasonal circulation. The analysis furnishes a mathematical model fo the coastal strip adjacent to the Italian shoreline, treated as a boundary layer in the density field, starting from general model equations valid throughout the interior of the Northern Adriatic. The boundary layer model is consequently used to modify the side wall boundary condition for the interior density field. Related numerical experiments are shown and compared with previous standard experiments in which the boundary layer contribution to the density field has not been considered. (author)

Analysis of three idealized reactor configurations: plate, pin, and homogeneous

International Nuclear Information System (INIS)

McKnight, R.D.

1983-01-01

Detailed Monte Carlo calculations have been performed for three distinct configurations of an idealized fast critical assembly. This idealized assembly was based on the LMFBR benchmark critical assembly ZPR-6/7. In the first configuration, the entire core was loaded with the plate unit cell of ZPR-6/7. In the second configuration, the entire core was loaded with the ZPR sodium-filled pin calandria. The actual ZPR pin calandria are loaded with mixed (U,Pu) oxide pins which closely match the composition of the ZPR-6/7 plate unit cell. For the present study, slight adjustments were made in the atom concentrations and the length of the pin calandria in order to make the core boundaries and average composition for the pin-cell configuration identical to those of the plate-cell configuration. In the third configuration, the core was homogeneous, again with identical core boundaries and average composition as the plate and pin configurations

Chemical reaction in MHD flow past a vertical plate with mass ...

African Journals Online (AJOL)

flow in a vertical double passage channel using Robin boundary conditions. ... the diffusion of a chemically reactive species in a laminar boundary layer flow. ...... hydrodynamic flow past a flat plate will Hall effects, Journal of the Physical.

A New Hyperbolic Shear Deformation Theory for Bending Analysis of Functionally Graded Plates

Directory of Open Access Journals (Sweden)

Tahar Hassaine Daouadji

2012-01-01

Full Text Available Theoretical formulation, Navier’s solutions of rectangular plates based on a new higher order shear deformation model are presented for the static response of functionally graded plates. This theory enforces traction-free boundary conditions at plate surfaces. Shear correction factors are not required because a correct representation of transverse shearing strain is given. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. The mechanical properties of the plate are assumed to vary continuously in the thickness direction by a simple power-law distribution in terms of the volume fractions of the constituents. Numerical illustrations concern flexural behavior of FG plates with metal-ceramic composition. Parametric studies are performed for varying ceramic volume fraction, volume fractions profiles, aspect ratios, and length to thickness ratios. Results are verified with available results in the literature. It can be concluded that the proposed theory is accurate and simple in solving the static bending behavior of functionally graded plates.

A novel approach to modeling plate deformations in fluid–structure interactions

Energy Technology Data Exchange (ETDEWEB)

Howard, T.K., E-mail: howartre@onid.oregonstate.edu [Oregon State University, Department of Nuclear Engineering & Radiation Health Physics, 116 Radiation Center, Corvallis, OR 97331 (United States); Marcum, W.R., E-mail: marcumw@engr.orst.edu [Oregon State University, Department of Nuclear Engineering & Radiation Health Physics, 116 Radiation Center, Corvallis, OR 97331 (United States); Jones, W.F. [Idaho National Laboratory, Nuclear Fuels & Materials Department, 2525 Fremont Ave., Idaho Falls, ID 83415 (United States)

2015-11-15

Highlights: • A new method for computing fluid structure interactions of flat plates is presented herein. • The method is validated through consideration of a single plate subject to hydraulic loading. • The model is compared against solution forms computed via ABAQUS and experimental data. • The model compares well against experimental data and the commercial computational code. - Abstract: As computational power increases, so does the desire to use computational simulations while designing fuel plates. The downside is multi-physics simulations – or more specifically, fluid–structure interactions (FSI) as addressed herein – require a larger amount of computational resources. Current simulations of a single plate can take weeks on a desktop computer, thus requiring the use of multiple servers or a cluster for FSI simulations. While computational fluid dynamic (CFD) codes coupled to computational structural mechanics (CSM) codes can provide a wealth of information regarding flow patterns, there should be some skepticism in whether or not they are the only means of achieving the desired solution. When the parameters of interest are the onset of plate collapse and the associated fluid channel velocities, coupled CFD–CSM simulations provide superfluous information. The paper provides an alternative approach to solving FSI problems using a 1-D, semi-analytical model derived from first principles. The results are compared and contrasted to the numerical and experimental work performed by Kennedy et al. (2014. Experimental Investigation of Deflection of Flat Aluminium Plates Under Variable Velocity Parallel Flow, Columbia: University of Missouri TherMec Research Group).

A novel approach to modeling plate deformations in fluid–structure interactions

International Nuclear Information System (INIS)

Howard, T.K.; Marcum, W.R.; Jones, W.F.

2015-01-01

Highlights: • A new method for computing fluid structure interactions of flat plates is presented herein. • The method is validated through consideration of a single plate subject to hydraulic loading. • The model is compared against solution forms computed via ABAQUS and experimental data. • The model compares well against experimental data and the commercial computational code. - Abstract: As computational power increases, so does the desire to use computational simulations while designing fuel plates. The downside is multi-physics simulations – or more specifically, fluid–structure interactions (FSI) as addressed herein – require a larger amount of computational resources. Current simulations of a single plate can take weeks on a desktop computer, thus requiring the use of multiple servers or a cluster for FSI simulations. While computational fluid dynamic (CFD) codes coupled to computational structural mechanics (CSM) codes can provide a wealth of information regarding flow patterns, there should be some skepticism in whether or not they are the only means of achieving the desired solution. When the parameters of interest are the onset of plate collapse and the associated fluid channel velocities, coupled CFD–CSM simulations provide superfluous information. The paper provides an alternative approach to solving FSI problems using a 1-D, semi-analytical model derived from first principles. The results are compared and contrasted to the numerical and experimental work performed by Kennedy et al. (2014. Experimental Investigation of Deflection of Flat Aluminium Plates Under Variable Velocity Parallel Flow, Columbia: University of Missouri TherMec Research Group).

Velocity- and slip-dependent weakening on the Tohoku plate boundary fault: shallow coseismic slip facilitated by foreshock afterslip

Science.gov (United States)

Ito, Y.; Ikari, M.; Ujiie, K.; Kopf, A.

2016-12-01

Understanding of role of slow earthquakes as they relate to the occurrence of both megathrust earthquakes and tsunami earthquakes is necessary to mitigate these disasters in the near future. Laboratory shearing experiments is one of important approach to evaluate these relationships. Here, we use powdered gouge samples from JFAST (IODP Expedition 343) Hole C0019E, core sample 17R-1, which is the plate boundary fault zone in the Japan Trench subduction zone. In this region, both large coseismic slip during the 2011 Tohoku-Oki earthquake as well as discrete slow slip events (SSE) have occurred. Experiments were conducted in a single-direct shear apparatus under normal stress of 16 MPa, with total shear displacements of up to 16 mm. We evaluate both the velocity- and slip-dependence of friction by extracting the velocity-dependent friction parameters a, b, and Dc, and measuring the rate of change in friction coefficient with shear displacement as the slip-dependence of friction. We report that in friction experiments using the Tohoku fault zone samples, an increase in sliding velocity exceeding that of earthquake afterslip can induce a change from steady-state frictional strength or slip hardening friction to slip-weakening frictional behavior. Our results show that the slip weakening is observed when the slip velocity exceeds 1 x 10-6 m/s during our experiments, while steady-state frictional strength or slip hardening is observed below 1x10-6 m/s. In the Japan Trench region, two slow events were observed at the downdip edge of the mainshock coseismic slip zone (< 30 m) were observed. These are an episodic SSE with a slip velocity of 0.1 x 10-6, and afterslip after the largest foreshock with a slip velocity of 2 x 10-6 m/s. This suggests that the afterslip may have facilitated the large coseismic slip during the mainshock on the plate boundary fault of the Tohoku-Oki earthquake.

Spectral assessment of the turbulent convection velocity in a spatially developing flat plate turbulent boundary layer at Reynolds numbers up to Re θ = 13000

OpenAIRE

Renard , N.; Deck , S.; Sagaut , P.

2014-01-01

International audience; A method inspired by del Alamo et al. [1] is derived to assess the wavelength-dependent convection velocity in a zero pressure gradient spatially developing flat plate turbulent boundary layer at Retheta = 13 000 for all wavelengths and all wall distances, using only estimates of the time power spectral density of the streamwise velocity and of its local spatial derivative. The resulting global convection velocity has a least-squares interpretation and is easily relate...

A model of anelastic relaxation associated with polygonization boundary

International Nuclear Information System (INIS)

Yan, S.C.

1990-01-01

A model of anelastic relaxation associated with polygonization boundary is proposed in order to explain internal friction peaks and other experimental phenomena observed recently. The model, which is referred to as vacancy-thermal jog model, shows that under conditions of high temperature and low applied stress with lower frequencies of vibration, thermal jog pairs are generated on dislocation segments of the boundaries. These jogs are in saturation with vacancies in the vicinity of them, and the vacancy current due to the concentration gradient of vacancy drifts among the boundaries. As a result, a diffusional creep is produced and a part of energy is dissipated. For vacancy drift, it is required that the thermal jogs emit (absorb) vacancies, which brings climbing bow of segments into operation, and another part of energy is dissipated so that there are two parts of energy dissipated in the strain process connected with polygonization boundary. Based on this point of view, the mathematical expressions of internal friction and modulus defect associated with polygonization boundary were subsequently derived and found to be in satisfactory agreement with experiments. (author). 13 refs, 6 figs

Free-boundary models of a meltwater conduit

KAUST Repository

Dallaston, Michael C.

2014-08-01

© 2014 AIP Publishing LLC. We analyse the cross-sectional evolution of an englacial meltwater conduit that contracts due to inward creep of the surrounding ice and expands due to melting. Making use of theoretical methods from free-boundary problems in Stokes flow and Hele-Shaw squeeze flow we construct an exact solution to the coupled problem of external viscous creep and internal heating, in which we adopt a Newtonian approximation for ice flow and an idealized uniform heat source in the conduit. This problem provides an interesting variant on standard free-boundary problems, coupling different internal and external problems through the kinematic condition at the interface. The boundary in the exact solution takes the form of an ellipse that may contract or expand (depending on the magnitudes of effective pressure and heating rate) around fixed focal points. Linear stability analysis reveals that without the melting this solution is unstable to perturbations in the shape. Melting can stabilize the interface unless the aspect ratio is too small; in that case, instabilities grow largest at the thin ends of the ellipse. The predictions are corroborated with numerical solutions using boundary integral techniques. Finally, a number of extensions to the idealized model are considered, showing that a contracting circular conduit is unstable to all modes of perturbation if melting occurs at a uniform rate around the boundary, or if the ice is modelled as a shear-thinning fluid.

Experiments on forced convection form a horizontal heated plate in a packed bed of glass spheres

Energy Technology Data Exchange (ETDEWEB)

Renken, K.J. (Univ. of Wisconsin, Milwaukee (USA)); Poulikakos, D. (Univ. of Illinois, Chicago (USA))

1989-02-01

This paper presents an experimental investigation of boundary-layer forced convective heat transfer from a flat isothermal plate in a packed bed of spheres. Extensive experimental results are reported for the thermal boundary-layer thickness, the temperature field, and the local wall heat flux (represented by the local Nusselt number). Theoretical findings of previous investigations using the Darcy flow model as well as a general model for themomentum equation accouting for flow inertia and macroscopic shear wtih and without variable porosity are used to evaluate the theoretical models. Several trends are revealed regarding the conditions of validity of these flow models. Overall the general flow model including variable porosity appears to perform better, even through the need for serious improvements in modeling becomes apparent.

Thermal Effects on Vibration and Control of Piezocomposite Kirchhoff Plate Modeled by Finite Elements Method

OpenAIRE

Sanbi, M.; Saadani, R.; Sbai, K.; Rahmoune, M.

2015-01-01

Theoretical and numerical results of the modeling of a smart plate are presented for optimal active vibration control. The smart plate consists of a rectangular aluminum piezocomposite plate modeled in cantilever configuration with surface bonded thermopiezoelectric patches. The patches are symmetrically bonded on top and bottom surfaces. A generic thermopiezoelastic theory for piezocomposite plate is derived, using linear thermopiezoelastic theory and Kirchhoff assumptions. Finite element eq...

Global Models of Ridge-Push Force, Geoid, and Lithospheric Strength of Oceanic plates

Science.gov (United States)

Mahatsente, Rezene

2017-12-01

An understanding of the transmission of ridge-push related stresses in the interior of oceanic plates is important because ridge-push force is one of the principal forces driving plate motion. Here, I assess the transmission of ridge-push related stresses in oceanic plates by comparing the magnitude of the ridge-push force to the integrated strength of oceanic plates. The strength is determined based on plate cooling and rheological models. The strength analysis includes low-temperature plasticity (LTP) in the upper mantle and assumes a range of possible tectonic conditions and rheology in the plates. The ridge-push force has been derived from the thermal state of oceanic lithosphere, seafloor depth and crustal age data. The results of modeling show that the transmission of ridge-push related stresses in oceanic plates mainly depends on rheology and predominant tectonic conditions. If a lithosphere has dry rheology, the estimated strength is higher than the ridge-push force at all ages for compressional tectonics and at old ages (>75 Ma) for extension. Therefore, under such conditions, oceanic plates may not respond to ridge-push force by intraplate deformation. Instead, the plates may transmit the ridge-push related stress in their interior. For a wet rheology, however, the strength of young lithosphere (stress may dissipate in the interior of oceanic plates and diffuses by intraplate deformation. The state of stress within a plate depends on the balance of far-field and intraplate forces.

Crossing boundaries in a collaborative modeling workspace

Science.gov (United States)

Morisette, Jeffrey T.; Cravens, Amanda; Miller, Brian W.; Talbert, Marian; Talbert, Colin; Jarnevich, Catherine S.; Fink, Michelle; Decker, Karin; Odell, Eric

2017-01-01

There is substantial literature on the importance of bridging across disciplinary and science–management boundaries. One of the ways commonly suggested to cross boundaries is for participants from both sides of the boundary to jointly produce information (i.e., knowledge co-production). But simply providing tools or bringing people together in the same room is not sufficient. Here we present a case study documenting the mechanisms by which managers and scientists collaborated to incorporate climate change projections into Colorado’s State Wildlife Action Plan. A critical component of the project was the use of a collaborative modeling and visualization workspace: the U.S. Geological Survey’s Resource for Advanced Modeling (RAM). Using video analysis and pre/post surveys from this case study, we examine how the RAM facilitated cognitive and social processes that co-produced a more salient and credible end product. This case provides practical suggestions to scientists and practitioners who want to implement actionable science.

Axisymmetric buckling analysis of laterally restrained thick annular plates using a hybrid numerical method

Energy Technology Data Exchange (ETDEWEB)

Malekzadeh, P. [Department of Mechanical Engineering, Persian Gulf University, Bushehr 75168 (Iran, Islamic Republic of); Center of Excellence for Computational Mechanics, Shiraz University, Shiraz (Iran, Islamic Republic of)], E-mail: malekzadeh@pgu.ac.ir; Ouji, A. [Department of Civil Engineering, Persian Gulf University, Bushehr 75168 (Iran, Islamic Republic of); Islamic Azad University, Larestan Branch, Larestan (Iran, Islamic Republic of)

2008-11-15

The buckling analysis of annular thick plates with lateral supports such as two-parameter elastic foundations or ring supports is investigated using an elasticity based hybrid numerical method. For this purpose, firstly, the displacement components are perturbed around the pre-buckling state, which is located using the elasticity theory. Then, by decomposing the plate into a set of sub-domain in the form of co-axial annular plates, the buckling equations are discretized through the radial direction using global interpolation functions in conjunction with the principle of virtual work. The resulting differential equations are solved using the differential quadrature method. The method has the capability of modeling the arbitrary boundary conditions either at the inner and outer edges of thin-to-thick plates and with different types of lateral restraints. The fast rate of convergence of the method is demonstrated and comparison studies are carried out to establish its accuracy and versatility for thin-to-thick plates.

Switching moving boundary models for two-phase flow evaporators and condensers

Science.gov (United States)

Bonilla, Javier; Dormido, Sebastián; Cellier, François E.

2015-03-01

The moving boundary method is an appealing approach for the design, testing and validation of advanced control schemes for evaporators and condensers. When it comes to advanced control strategies, not only accurate but fast dynamic models are required. Moving boundary models are fast low-order dynamic models, and they can describe the dynamic behavior with high accuracy. This paper presents a mathematical formulation based on physical principles for two-phase flow moving boundary evaporator and condenser models which support dynamic switching between all possible flow configurations. The models were implemented in a library using the equation-based object-oriented Modelica language. Several integrity tests in steady-state and transient predictions together with stability tests verified the models. Experimental data from a direct steam generation parabolic-trough solar thermal power plant is used to validate and compare the developed moving boundary models against finite volume models.

Flow induced deformation and collapse of a thin rectangular plate with application to the Engineering Test Reactor nuclear fuel elements

International Nuclear Information System (INIS)

Davis, C.D.

1981-01-01

This work examines a single flat fuel plate bounded by two channels and determines static plate deflections, resultant forces and bending stresses due to pressure differential and hydrodynamic loadings. The classical then reactangular plate equations are used to model the fuel plate. These equations contain as an input the hydrodynamic loading function for modeling the fluid-structural interaction. Two models of the channel flow are developed. One assumes the accelerating potential core flow is laminar with developing two-dimensional laminar boundary layers being formed on the channel walls. The Schlichting entry length solution for developing laminar flow is found to be valid the entire length of the channel. The second model assumes the core flow is fully-developed turbulent the entire length of the channel. Hydrodynamic loading functions are developed for both flow models containing parameters for fluid density, fluid velocity, Reynolds number and channel and plate dimensions. Hence the effects of each parameter can be examined independently. A criterion is developed for predicting ETR fuel plate collapse at high channel flow velocities, 1067 cm/s (420 in/sec) (R/sub e/ = 60,000). The criterion predicts that in order to prevent ETR plate collapse the inlet velocities between channels must not differ by more than 2%

A Comment Upon Previous Studies on 3-D Boundary Layer Transition

OpenAIRE

ÇARPINLIOĞLU, Melda Özdinç

2014-01-01

The common feature of the experimental studies upon 3-D boundary layer development on swept flat plates cited in the available literature is the application of streamwise and/or spanwise pressure gradients. In fact; presence of the pressure gradients was suggested to be vital for having crossflow effective in 3-D boundary layer transition. In the presented paper here, this idea is questioned evaluating the results of an experimental investigation conducted on swept flat plates under the ab...

The Lithosphere-asthenosphere Boundary beneath the South Island of New Zealand

Science.gov (United States)

Hua, J.; Fischer, K. M.; Savage, M. K.

2017-12-01

Lithosphere-asthenosphere boundary (LAB) properties beneath the South Island of New Zealand have been imaged by Sp receiver function common-conversion point stacking. In this transpressional boundary between the Australian and Pacific plates, dextral offset on the Alpine fault and convergence have occurred for the past 20 My, with the Alpine fault now bounded by Australian plate subduction to the south and Pacific plate subduction to the north. This study takes advantage of the long-duration and high-density seismometer networks deployed on or near the South Island, especially 29 broadband stations of the New Zealand permanent seismic network (GeoNet). We obtained 24,980 individual receiver functions by extended-time multi-taper deconvolution, mapping to three-dimensional space using a Fresnel zone approximation. Pervasive strong positive Sp phases are observed in the LAB depth range indicated by surface wave tomography (Ball et al., 2015) and geochemical studies. These phases are interpreted as conversions from a velocity decrease across the LAB. In the central South Island, the LAB is observed to be deeper and broader to the west of the Alpine fault. The deeper LAB to the west of the Alpine fault is consistent with oceanic lithosphere attached to the Australian plate that was partially subducted while also translating parallel to the Alpine fault (e.g. Sutherland, 2000). However, models in which the Pacific lithosphere has been underthrust to the west past the Alpine fault cannot be ruled out. Further north, a zone of thin lithosphere with a strong and vertically localized LAB velocity gradient occurs to the west of the fault, juxtaposed against a region of anomalously weak LAB conversions to the east of the fault. This structure, similar to results of Sp imaging beneath the central segment of the San Andreas fault (Ford et al., 2014), also suggests that lithospheric blocks with contrasting LAB properties meet beneath the Alpine fault. The observed variations in

LES of the adverse-pressure gradient turbulent boundary layer

International Nuclear Information System (INIS)

Inoue, M.; Pullin, D.I.; Harun, Z.; Marusic, I.

2013-01-01

Highlights: • The adverse-pressure gradient turbulent boundary layer at high Re is studied. • Wall-model LES works well for nonequilibrium turbulent boundary layer. • Relationship of skin-friction to Re and Clauser pressure parameter is explored. • Self-similarity is observed in the velocity statistics over a wide range of Re. -- Abstract: We describe large-eddy simulations (LES) of the flat-plate turbulent boundary layer in the presence of an adverse pressure gradient. The stretched-vortex subgrid-scale model is used in the domain of the flow coupled to a wall model that explicitly accounts for the presence of a finite pressure gradient. The LES are designed to match recent experiments conducted at the University of Melbourne wind tunnel where a plate section with zero pressure gradient is followed by section with constant adverse pressure gradient. First, LES are described at Reynolds numbers based on the local free-stream velocity and the local momentum thickness in the range 6560–13,900 chosen to match the experimental conditions. This is followed by a discussion of further LES at Reynolds numbers at approximately 10 times and 100 times these values, which are well out of range of present day direct numerical simulation and wall-resolved LES. For the lower Reynolds number runs, mean velocity profiles, one-point turbulent statistics of the velocity fluctuations, skin friction and the Clauser and acceleration parameters along the streamwise, adverse pressure-gradient domain are compared to the experimental measurements. For the full range of LES, the relationship of the skin-friction coefficient, in the form of the ratio of the local free-stream velocity to the local friction velocity, to both Reynolds number and the Clauser parameter is explored. At large Reynolds numbers, a region of collapse is found that is well described by a simple log-like empirical relationship over two orders of magnitude. This is expected to be useful for constant adverse

Bypass transition in compressible boundary layers

Science.gov (United States)

Vandervegt, J. J.

1992-01-01

transitional state. The effects of large free stream turbulence in compressible boundary layers at Mach numbers are examined both in the subsonic and transonic regime using direct numerical simulations. The flow is computed over a flat plate and curved surface. while many applications operate in the transonic regime. Due the nature of their numerical scheme, a non-conservation formulation of the Navier-Stokes equations, it is a non-trivial extension to compute flow fields in the transonic regime. This project aims at better understanding the effects of large free-stream turbulence in compressible boundary layers at mach number both in the subsonic and transonic regime using direct numerical simulations. The present project aims at computing the flow over a flat plate and curved surface. This research will provide data which can be used to clarify mechanisms leading to transition in an environment with high free stream turbulence. This information is useful for the development of turbulence models, which are of great importance for CFD applications, and are currently unreliable for more complex flows, such as transitional flows.

Magnetohydrodynamic boundary layer flow past a porous substrate with Beavers-Joseph boundary condition

International Nuclear Information System (INIS)

Jat, R.N.; Chaudhary, Santosh

2009-01-01

The flow of an electrically conducting fluid past a porous substrate attached to the flat plate with Beavers-Joseph boundary condition under the influence of a uniform transverse magnetic field has been studied. Taking suitable similar variables, the momentum equation is transformed to ordinary differential equation and solved by standard techniques. The energy equation is solved by considering two boundary layers, one in the porous substrate and the other above the porous substrate. The velocity and temperature distributions along with Nusselt number are discussed numerically and presented through graphs. (author)

Initializing a Mesoscale Boundary-Layer Model with Radiosonde Observations

Science.gov (United States)

Berri, Guillermo J.; Bertossa, Germán

2018-01-01

A mesoscale boundary-layer model is used to simulate low-level regional wind fields over the La Plata River of South America, a region characterized by a strong daily cycle of land-river surface-temperature contrast and low-level circulations of sea-land breeze type. The initial and boundary conditions are defined from a limited number of local observations and the upper boundary condition is taken from the only radiosonde observations available in the region. The study considers 14 different upper boundary conditions defined from the radiosonde data at standard levels, significant levels, level of the inversion base and interpolated levels at fixed heights, all of them within the first 1500 m. The period of analysis is 1994-2008 during which eight daily observations from 13 weather stations of the region are used to validate the 24-h surface-wind forecast. The model errors are defined as the root-mean-square of relative error in wind-direction frequency distribution and mean wind speed per wind sector. Wind-direction errors are greater than wind-speed errors and show significant dispersion among the different upper boundary conditions, not present in wind speed, revealing a sensitivity to the initialization method. The wind-direction errors show a well-defined daily cycle, not evident in wind speed, with the minimum at noon and the maximum at dusk, but no systematic deterioration with time. The errors grow with the height of the upper boundary condition level, in particular wind direction, and double the errors obtained when the upper boundary condition is defined from the lower levels. The conclusion is that defining the model upper boundary condition from radiosonde data closer to the ground minimizes the low-level wind-field errors throughout the region.

Decay Rates of Interactive Hyperbolic-Parabolic PDE Models with Thermal Effects on the Interface

International Nuclear Information System (INIS)

Lasiecka, I.; Lebiedzik, C.

2000-01-01

We consider coupled PDE systems comprising of a hyperbolic and a parabolic-like equation with an interface on a portion of the boundary. These models are motivated by structural acoustic problems. A specific prototype consists of a wave equation defined on a three-dimensional bounded domain Ω coupled with a thermoelastic plate equation defined on Γ 0 -a flat surface of the boundary Ω. Thus, the coupling between the wave and the plate takes place on the interface Γ 0 . The main issue studied here is that of uniform stability of the overall interactive model. Since the original (uncontrolled) model is only strongly stable, but not uniformly stable, the question becomes: what is the 'minimal amount' of dissipation necessary to obtain uniform decay rates for the energy of the overall system? Our main result states that boundary nonlinear dissipation placed only on a suitable portion of the part of the boundary which is complementary to Γ 0 , suffices for the stabilization of the entire structure. This result is new with respect to the literature on several accounts: (i) thermoelasticity is accounted for in the plate model; (ii) the plate model does not account for any type of mechanical damping, including the structural damping most often considered in the literature; (iii) there is no mechanical damping placed on the interface Γ 0 ; (iv) the boundary damping is nonlinear without a prescribed growth rate at the origin; (v) the undamped portions of the boundary partial Ω are subject to Neumann (rather than Dirichlet) boundary conditions, which is a recognized difficulty in the context of stabilization of wave equations, due to the fact that the strong Lopatinski condition does not hold. The main mathematical challenge is to show how the thermal energy is propagated onto the hyperbolic component of the structure. This is achieved by using a recently developed sharp theory of boundary traces corresponding to wave and plate equations, along with the analytic

Mean flow structure of non-equilibrium boundary layers with adverse ...

Indian Academy of Sciences (India)

According to them, an equilibrium boundary layer might exist if the pressure ... of adverse pressure gradient on the turbulent boundary layer at the flat plate for ..... of a constant-pressure turbulent layer to the sudden application of an sudden.

Turbulent boundary layer heat transfer experiments: Convex curvature effects including introduction and recovery

Science.gov (United States)

Simon, T. W.; Moffat, R. J.; Johnston, J. P.; Kays, W. M.

1982-01-01

Measurements were made of the heat transfer rate through turbulent and transitional boundary layers on an isothermal, convexly curved wall and downstream flat plate. The effect of convex curvature on the fully turbulent boundary layer was a reduction of the local Stanton numbers 20% to 50% below those predicted for a flat wall under the same circumstances. The recovery of the heat transfer rates on the downstream flat wall was extremely slow. After 60 cm of recovery length, the Stanton number was still typically 15% to 20% below the flat wall predicted value. Various effects important in the modeling of curved flows were studied separately. These are: the effect of initial boundary layer thickness, the effect of freestream velocity, the effect of freestream acceleration, the effect of unheated starting length, and the effect of the maturity of the boundary layer. An existing curvature prediction model was tested against this broad heat transfer data base to determine where it could appropriately be used for heat transfer predictions.

Reissner-Mindlin plate model with uncertain input data

Czech Academy of Sciences Publication Activity Database

Hlaváček, Ivan; Chleboun, J.

2014-01-01

Roč. 17, Jun (2014), s. 71-88 ISSN 1468-1218 Institutional support: RVO:67985840 Keywords : Reissner-Mindlin model * orthotropic plate Subject RIV: BA - General Mathematics Impact factor: 2.519, year: 2014 http://www.sciencedirect.com/science/article/pii/S1468121813001077

SCDAP/RELAP5 lower core plate model

International Nuclear Information System (INIS)

Coryell, E.W.; Griffin, F.P.

1999-01-01

The SCDAP/RELAP5 computer code is a best-estimate analysis tool for performing nuclear reactor severe accident simulations. This report describes the justification, theory, implementation, and testing of a new modeling capability which will refine the analysis of the movement of molten material from the core region to the vessel lower head. As molten material moves from the core region through the core support structures it may encounter conditions which will cause it to freeze in the region of the lower core plate, delaying its arrival to the vessel head. The timing of this arrival is significant to reactor safety, because during the time span for material relocation to the lower head, the core may be experiencing steam-limited oxidation. The time at which hot material arrives in a coolant-filled lower vessel head, thereby significantly increasing the steam flow rate through the core region, becomes significant to the progression and timing of a severe accident. This report is a revision of a report INEEL/EXT-00707, entitled ''Preliminary Design Report for SCDAP/RELAP5 Lower Core Plate Model''

The M w = 5.8 14 August 2016 middle Sakhalin earthquake on a boundary between Okhotsk and Eurasian (Amurian) plates

Science.gov (United States)

Konovalov, A. V.; Stepnov, A. A.; Safonov, D. A.; Kozhurin, A. I.; Pavlov, A. S.; Gavrilov, A. V.; Manaychev, K. A.; Tomilev, D. Ye.; Takahashi, H.; Ichiyanagi, M.

2018-04-01

An earthquake with the moment magnitude M w = 5.8 occurred in the middle part of the Sakhalin Island, Russian Federation, on 14 August 2016, at 11:17 a.m. UTC. The earthquake source was located west of the Central Sakhalin Fault Zone, which is considered to mark the boundary between the Okhotsk and Eurasian (Amurian) plates. Moment tensor solution of the mainshock as well as the configuration of aftershock cloud suggests that the earthquake was caused by slip on a SW-dipping reverse fault. For the first time for Sakhalin, we have got the felt reports unified in accordance with DYFI. We also analyzed observed PGA values and, based on them, produced shaking maps.

Low-complexity computation of plate eigenmodes with Vekua approximations and the method of particular solutions

Science.gov (United States)

Chardon, Gilles; Daudet, Laurent

2013-11-01

This paper extends the method of particular solutions (MPS) to the computation of eigenfrequencies and eigenmodes of thin plates, in the framework of the Kirchhoff-Love plate theory. Specific approximation schemes are developed, with plane waves (MPS-PW) or Fourier-Bessel functions (MPS-FB). This framework also requires a suitable formulation of the boundary conditions. Numerical tests, on two plates with various boundary conditions, demonstrate that the proposed approach provides competitive results with standard numerical schemes such as the finite element method, at reduced complexity, and with large flexibility in the implementation choices.

Thermal flexural analysis of cross-ply laminated plates using trigonometric shear deformation theory

Directory of Open Access Journals (Sweden)

Yuwaraj Marotrao Ghugal

Full Text Available Thermal stresses and displacements for orthotropic, two-layer antisymmetric, and three-layer symmetric square cross-ply laminated plates subjected to nonlinear thermal load through the thickness of laminated plates are presented by using trigonometric shear deformation theory. The in-plane displacement field uses sinusoidal function in terms of thickness co-ordinate to include the shear deformation effect. The theory satisfies the shear stress free boundary conditions on the top and bottom surfaces of the plate. The present theory obviates the need of shear correction factor. Governing equations and boundary conditions of the theory are obtained using the principle of virtual work. The validity of present theory is verified by comparing the results with those of classical plate theory and first order shear deformation theory and higher order shear deformation theory.

Application of the High Gradient hydrodynamics code to simulations of a two-dimensional zero-pressure-gradient turbulent boundary layer over a flat plate

Science.gov (United States)

Kaiser, Bryan E.; Poroseva, Svetlana V.; Canfield, Jesse M.; Sauer, Jeremy A.; Linn, Rodman R.

2013-11-01

The High Gradient hydrodynamics (HIGRAD) code is an atmospheric computational fluid dynamics code created by Los Alamos National Laboratory to accurately represent flows characterized by sharp gradients in velocity, concentration, and temperature. HIGRAD uses a fully compressible finite-volume formulation for explicit Large Eddy Simulation (LES) and features an advection scheme that is second-order accurate in time and space. In the current study, boundary conditions implemented in HIGRAD are varied to find those that better reproduce the reduced physics of a flat plate boundary layer to compare with complex physics of the atmospheric boundary layer. Numerical predictions are compared with available DNS, experimental, and LES data obtained by other researchers. High-order turbulence statistics are collected. The Reynolds number based on the free-stream velocity and the momentum thickness is 120 at the inflow and the Mach number for the flow is 0.2. Results are compared at Reynolds numbers of 670 and 1410. A part of the material is based upon work supported by NASA under award NNX12AJ61A and by the Junior Faculty UNM-LANL Collaborative Research Grant.

The Ritz - Sublaminate Generalized Unified Formulation approach for piezoelectric composite plates

Science.gov (United States)

D'Ottavio, Michele; Dozio, Lorenzo; Vescovini, Riccardo; Polit, Olivier

2018-01-01

This paper extends to composite plates including piezoelectric plies the variable kinematics plate modeling approach called Sublaminate Generalized Unified Formulation (SGUF). Two-dimensional plate equations are obtained upon defining a priori the through-thickness distribution of the displacement field and electric potential. According to SGUF, independent approximations can be adopted for the four components of these generalized displacements: an Equivalent Single Layer (ESL) or Layer-Wise (LW) description over an arbitrary group of plies constituting the composite plate (the sublaminate) and the polynomial order employed in each sublaminate. The solution of the two-dimensional equations is sought in weak form by means of a Ritz method. In this work, boundary functions are used in conjunction with the domain approximation expressed by an orthogonal basis spanned by Legendre polynomials. The proposed computational tool is capable to represent electroded surfaces with equipotentiality conditions. Free-vibration problems as well as static problems involving actuator and sensor configurations are addressed. Two case studies are presented, which demonstrate the high accuracy of the proposed Ritz-SGUF approach. A model assessment is proposed for showcasing to which extent the SGUF approach allows a reduction of the number of unknowns with a controlled impact on the accuracy of the result.

Influence on electron coherence from quantum electromagnetic fields in the presence of conducting plates

International Nuclear Information System (INIS)

Hsiang, J.-T.; Lee, D.-S.

2006-01-01

The influence of electromagnetic vacuum fluctuations in the presence of the perfectly conducting plate on electrons is studied with an interference experiment. The evolution of the reduced density matrix of the electron is derived by the method of influence functional. We find that the plate boundary anisotropically modifies vacuum fluctuations that in turn affect the electron coherence. The path plane of the interference is chosen either parallel or normal to the plate. In the vicinity of the plate, we show that the coherence between electrons due to the boundary is enhanced in the parallel configuration, but reduced in the normal case. The presence of the second parallel plate is found to boost these effects. The potential relation between the amplitude change and phase shift of interference fringes is pointed out. The finite conductivity effect on electron coherence is discussed

Reconstruction of Northeast Asian Deformation Integrated with Western Pacific Plate Subduction since 200 Ma

Science.gov (United States)

Liu, S.; Gurnis, M.; Ma, P.; Zhang, B.

2017-12-01

The configuration and kinematics of continental deformation and its marginal plate tectonics on the Earth's surface are intrinsic manifestations of plate-mantle coupling. The complex interactions of plate boundary forces result in plate motions that are dominated by slab pull and ridge push forces and the effects of mantle drag; these interactions also result in continental deformation with a complex basin-mountain architecture and evolution. The kinematics and evolution of the western Pacific subduction and northeast Asian continental-margin deformation are a first-order tectonic process whose nature and chronology remains controversial. This paper implements a "deep-time" reconstruction of the western Pacific subduction, continental accretion or collision and basin-mountain deformation in northeast Asia since 200 Ma based on a newly revised global plate model. The results demonstrate a NW-SE-oriented shortening from 200-137 Ma, a NWW-SEE-oriented extension from 136-101 Ma, a nearly N-S-oriented extension and uplift with a short-term NWW-SEE-oriented compressional inversion in northeast China from 100-67 Ma, and a NW-SE- and nearly N-S-oriented extension from 66 Ma to the present day. The western Pacific oceanic plate subducted forward under East Asia along Mudanjiang-Honshu Island during the Jurassic, and the trenches retreated to the Sikhote-Alin, North Shimanto, and South Shimanto zones from ca. 137-128 Ma, ca. 130-90 Ma, and in ca. 60 Ma, respectively. Our time-dependent analysis of plate motion and continental deformation coupling suggests that the multi-plate convergent motion and ocean-continent convergent orogeny were induced by advance subduction during the Jurassic and earliest Cretaceous. Our analysis also indicates that the intra-continent rifting and back-arc extension were triggered by trench retreat during the Cretaceous and that the subduction of oceanic ridge and arc were triggered by trench retreat during the Cenozoic. Therefore, reconstructing

Micromechanical Modeling of Grain Boundaries Damage in a Copper Alloy Under Creep

International Nuclear Information System (INIS)

Voese, Markus

2015-01-01

In order to include the processes on the scale of the grain structure into the description of the creep behaviour of polycrystalline materials, the damage development of a single grain boundary has been initially investigated in the present work. For this purpose, a special simulationmethod has been used, whose resolution procedure based on holomorphic functions. The mechanisms taken into account for the simulations include nucleation, growth by grain boundary diffusion, coalescence and shrinkage until complete sintering of grain boundary cavities. These studies have then been used to develop a simplified cavitation model, which describes the grain boundary damage by two state variables and the time-dependent development by a mechanism-oriented rate formulation. To include the influence of grain boundaries within continuum mechanical considerations of polycrystals, an interface model has been developed, that incorporates both damage according to the simplified cavitation model and grain boundary sliding in dependence of a phenomenological grain boundary viscosity. Furthermore a micromechanical model of a polycrystal has been developed that allows to include a material's grain structure into the simulation of the creep behaviour by means of finite element simulations. Thereby, the deformations of individual grains are expressed by a viscoplastic single crystal model and the grain boundaries are described by the proposed interface model. The grain structure is represented by a finite element model, in which the grain boundaries are modelled by cohesive elements. From the evaluation of experimental creep data, the micromechanical model of a polycrystal has been calibrated for a copper-antimony alloy at a temperature of 823 K. Thereby, the adjustment of the single crystal model has been carried out on the basis of creep rates of pure copper single crystal specimens. The experimental determination of grain boundary sliding and grain boundary porosity for coarse

Modeling Simple Driving Tasks with a One-Boundary Diffusion Model

Science.gov (United States)

Ratcliff, Roger; Strayer, David

2014-01-01

A one-boundary diffusion model was applied to the data from two experiments in which subjects were performing a simple simulated driving task. In the first experiment, the same subjects were tested on two driving tasks using a PC-based driving simulator and the psychomotor vigilance test (PVT). The diffusion model fit the response time (RT) distributions for each task and individual subject well. Model parameters were found to correlate across tasks which suggests common component processes were being tapped in the three tasks. The model was also fit to a distracted driving experiment of Cooper and Strayer (2008). Results showed that distraction altered performance by affecting the rate of evidence accumulation (drift rate) and/or increasing the boundary settings. This provides an interpretation of cognitive distraction whereby conversing on a cell phone diverts attention from the normal accumulation of information in the driving environment. PMID:24297620

Simulation of through via bottom—up copper plating with accelerator for the filling of TSVs

International Nuclear Information System (INIS)

Wu Heng; Tang Zhen'an; Wang Zhu; Cheng Wan; Yu Daquan

2013-01-01

Filling high aspect ratio through silicon vias (TSVs) without voids and seams by copper plating is one of the technical challenges for 3D integration. Bottom—up copper plating is an effective solution for TSV filling. In this paper, a new numerical model was developed to simulate the electrochemical deposition (ECD) process, and the influence of an accelerator in the electrolyte was investigated. The arbitrary Lagrange—Eulerian (ALE) method for solving moving boundaries in the finite element method (FEM) was used to simulate the electrochemical process. In the model, diffusion coefficient and adsorption coefficient were considered, and then the time-resolved evolution of electroplating profiles was simulated with ion concentration distribution and the electric current density. (semiconductor technology)

Intra-continental subduction and contemporaneous lateral extrusion of the upper plate: insights into Alps-Adria interactions

Science.gov (United States)

van Gelder, Inge; Willingshofer, Ernst; Sokoutis, Dimitrios; Cloetingh, Sierd

2017-04-01

A series of physical analogue experiments were performed to simulate intra-continental subduction contemporaneous with lateral extrusion of the upper plate to study the interferences between these two processes at crustal levels and in the lithospheric mantle. The lithospheric-scale models are specifically designed to represent the collision of the Adriatic microplate with the Eastern Alps, simulated by an intra-continental weak zone to initiate subduction and a weak confined margin perpendicular to the direction of convergence in order to allow for extrusion of the lithosphere. The weak confined margin is the analog for the opening of the Pannonian back-arc basin adjacent to the Eastern Alps with the direction of extension perpendicular to the strike of the orogen. The models show that intra-continental subduction and coeval lateral extrusion of the upper plate are compatible processes. The obtained deformation structures within the extruding region are similar compared to the classical setup where lateral extrusion is provoked by lithosphere-scale indentation. In the models a strong coupling across the subduction boundary allows for the transfer of abundant stresses to the upper plate, leading to laterally varying strain regimes that are characterized by crustal thickening near a confined margin and dominated by lateral displacement of material near a weak lateral confinement. During ongoing convergence the strain regimes propagate laterally, thereby creating an area of overlap characterized by transpression. In models with oblique subduction, with respect to the convergence direction, less deformation of the upper plate is observed and as a consequence the amount of lateral extrusion decreases. Additionally, strain is partitioned along the oblique plate boundary leading to less subduction in expense of right lateral displacement close to the weak lateral confinement. Both oblique and orthogonal subduction models have a strong resemblance to lateral extrusion

Elastic stability of laminated, flat and curved, long rectangular plates subjected to combined inplane loads

Science.gov (United States)

Viswanathan, A. V.; Tamekuni, M.; Baker, L. L.

1974-01-01

A method is presented to predict theoretical buckling loads of long, rectangular flat and curved laminated plates with arbitrary orientation of orthotropic axes each lamina. The plate is subjected to combined inplane normal and shear loads. Arbitrary boundary conditions may be stipulated along the longitudinal sides of the plate. In the absence of inplane shear loads and extensional-shear coupling, the analysis is also applicable to finite length plates. Numerical results are presented for curved laminated composite plates with boundary conditions and subjected to various loadings. These results indicate some of the complexities involved in the numerical solution of the analysis for general laminates. The results also show that the reduced bending stiffness approximation when applied to buckling problems could lead to considerable error in some cases and therefore must be used with caution.

Exact solutions to plaquette Ising models with free and periodic boundaries

International Nuclear Information System (INIS)

Mueller, Marco; Johnston, Desmond A.; Janke, Wolfhard

2017-01-01

An anisotropic limit of the 3d plaquette Ising model, in which the plaquette couplings in one direction were set to zero, was solved for free boundary conditions by Suzuki (1972) , who later dubbed it the fuki-nuke, or “no-ceiling”, model. Defining new spin variables as the product of nearest-neighbour spins transforms the Hamiltonian into that of a stack of (standard) 2d Ising models and reveals the planar nature of the magnetic order, which is also present in the fully isotropic 3d plaquette model. More recently, the solution of the fuki-nuke model was discussed for periodic boundary conditions, which require a different approach to defining the product spin transformation, by Castelnovo et al. (2010) . We clarify the exact relation between partition functions with free and periodic boundary conditions expressed in terms of original and product spin variables for the 2d plaquette and 3d fuki-nuke models, noting that the differences are already present in the 1d Ising model. In addition, we solve the 2d plaquette Ising model with helical boundary conditions. The various exactly solved examples illustrate how correlations can be induced in finite systems as a consequence of the choice of boundary conditions.

Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico

Science.gov (United States)

van der Werf, Thomas; Chatzaras, Vasileios; Marcel Kriegsman, Leo; Kronenberg, Andreas; Tikoff, Basil; Drury, Martyn R.

2017-12-01

The rheology of lower crust and its transient behavior in active strike-slip plate boundaries remain poorly understood. To address this issue, we analyzed a suite of granulite and lherzolite xenoliths from the upper Pleistocene-Holocene San Quintín volcanic field of northern Baja California, Mexico. The San Quintín volcanic field is located 20 km east of the Baja California shear zone, which accommodates the relative movement between the Pacific plate and Baja California microplate. The development of a strong foliation in both the mafic granulites and lherzolites, suggests that a lithospheric-scale shear zone exists beneath the San Quintín volcanic field. Combining microstructural observations, geothermometry, and phase equilibria modeling, we estimated that crystal-plastic deformation took place at temperatures of 750-890 °C and pressures of 400-560 MPa, corresponding to 15-22 km depth. A hot crustal geotherm of 40 ° C km-1 is required to explain the estimated deformation conditions. Infrared spectroscopy shows that plagioclase in the mafic granulites is relatively dry. Microstructures are interpreted to show that deformation in both the uppermost lower crust and upper mantle was accommodated by a combination of dislocation creep and grain-size-sensitive creep. Recrystallized grain size paleopiezometry yields low differential stresses of 12-33 and 17 MPa for plagioclase and olivine, respectively. The lower range of stresses (12-17 MPa) in the mafic granulite and lherzolite xenoliths is interpreted to be associated with transient deformation under decreasing stress conditions, following an event of stress increase. Using flow laws for dry plagioclase, we estimated a low viscosity of 1.1-1.3×1020 Pa ṡ s for the high temperature conditions (890 °C) in the lower crust. Significantly lower viscosities in the range of 1016-1019 Pa ṡ s, were estimated using flow laws for wet plagioclase. The shallow upper mantle has a low viscosity of 5.7×1019 Pa ṡ s

Oblique radiation lateral open boundary conditions for a regional climate atmospheric model

Science.gov (United States)

Cabos Narvaez, William; De Frutos Redondo, Jose Antonio; Perez Sanz, Juan Ignacio; Sein, Dmitry

2013-04-01

The prescription of lateral boundary conditions in regional atmospheric models represent a very important issue for limited area models. The ill-posed nature of the open boundary conditions makes it necessary to devise schemes in order to filter spurious wave reflections at boundaries, being desirable to have one boundary condition per variable. On the other side, due to the essentially hyperbolic nature of the equations solved in state of the art atmospheric models, external data is required only for inward boundary fluxes. These circumstances make radiation lateral boundary conditions a good choice for the filtering of spurious wave reflections. Here we apply the adaptive oblique radiation modification proposed by Mikoyada and Roseti to each of the prognostic variables of the REMO regional atmospheric model and compare it to the more common normal radiation condition used in REMO. In the proposed scheme, special attention is paid to the estimation of the radiation phase speed, essential to detecting the direction of boundary fluxes. One of the differences with the classical scheme is that in case of outward propagation, the adaptive nudging imposed in the boundaries allows to minimize under and over specifications problems, adequately incorporating the external information.

The Modeling of Viscoelastic Circular Plates for Use as Waveguide Absorbers

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1988-09-01

oncituoe Security Ciasstircation) X THE MODELING OF VISCOELASTIC CIRCULAR PLATES FOR USE AS WAVEGUIDE ABSORBERS C 12 PERSONAL AUTmO ?S) -Hettema...33mvU3dT’U Figure 67. Experimental Jmainiey Part ot the Driving Point Jmpedancs of a 6 in Radius Elastic Plate, With and Without aaker and Mount Conecon, In

Oblique Wave-Induced Responses of A VLFS Edged with A Pair of Inclined Perforated Plates

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Cheng, Yong; Ji, Chun-yan; Zhai, Gang-jun; Oleg, Gaidai

2018-03-01

This paper is concerned with the hydroelastic responses of a mat-like, rectangular very large floating structure (VLFS) edged with a pair of horizontal/inclined perforated anti-motion plates in the context of the direct coupling method. The updated Lagrangian formulae are applied to establish the equilibrium equations of the VLFS and the total potential formula is employed for fluids in the numerical model including the viscous effect of the perforated plates through the Darcy's law. The hybrid finite element-boundary element (FE-BE) method is implemented to determine the response reduction of VLFS with attached perforated plates under various oblique incident waves. Also, the numerical solutions are validated against a series of experimental tests. The effectiveness of the attached perforated plates in reducing the deflections of the VLFS can be significantly improved by selecting the proper design parameters such as the porous parameter, submergence depth, plate width and inclination angle for the given sea conditions.

Modal radiation patterns of baffled circular plates and membranes.

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Christiansen, Thomas Lehrmann; Hansen, Ole; Thomsen, Erik Vilain; Jensen, Jørgen Arendt

2014-05-01

The far field velocity potential and radiation pattern of baffled circular plates and membranes are found analytically using the full set of modal velocity profiles derived from the corresponding equation of motion. The derivation is valid for a plate or membrane subjected to an external excitation force, which is used as a sound receiver in any medium or as a sound transmitter in a gaseous medium. A general, concise expression is given for the radiation pattern of any mode of the membrane and the plate with arbitrary boundary conditions. Specific solutions are given for the four special cases of a plate with clamped, simply supported, and free edge boundary conditions as well as for the membrane. For all non-axisymmetric modes, the velocity potential along the axis of the radiator is found to be strictly zero. In the long wavelength limit, the radiation pattern of all axisymmetric modes approaches that of a monopole, while the non-axisymmetric modes exhibit multipole behavior. Numerical results are also given, demonstrating the implications of having non-axisymmetric excitation using both a point excitation with varying eccentricity and a homogeneous excitation acting on half of the circular radiator.

Shed vortex structure and phase-averaged velocity statistics in symmetric/asymmetric turbulent flat plate wakes

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Rai, Man Mohan

2018-05-01

The near wake of a flat plate is investigated via direct numerical simulations. Many earlier experimental investigations have used thin plates with sharp trailing edges and turbulent boundary layers to create the wake. This results in large θ/DTE values (θ is the boundary layer momentum thickness toward the end of the plate and DTE is the trailing edge thickness). In the present study, the emphasis is on relatively thick plates with circular trailing edges (CTEs) resulting in θ/D values less than one (D is the plate thickness and the diameter of the CTE) and vigorous vortex shedding. The Reynolds numbers based on the plate length and D are 1.255 × 106 and 10 000, respectively. Two cases are computed: one with turbulent boundary layers on both the upper and lower surfaces of the plate (statistically the same, symmetric wake, Case TT) and the other with turbulent and laminar boundary layers on the upper and lower surfaces, respectively (asymmetric case, Case TL). The data and understanding obtained are of considerable engineering interest, particularly in turbomachinery where the pressure side of an airfoil can remain laminar or transitional because of a favorable pressure gradient and the suction side is turbulent. Shed-vortex structure and phase-averaged velocity statistics obtained in the two cases are compared here. The upper negative shed vortices in Case TL (turbulent separating boundary layer) are weaker than the lower positive ones (laminar separating boundary layer) at inception (a factor of 1.27 weaker in terms of peak phase-averaged spanwise vorticity at the first appearance of a peak). The upper vortices weaken rapidly as they travel downstream. A second feature of interest in Case TL is a considerable increase in the peak phase-averaged, streamwise normal intensity (random component) with increasing streamwise distance (x/D) that occurs near the positive vortex cores. This behavior is observed for a few diameters in the near wake. This is counter to

A layer-wise MITC9 finite element for the free-vibration analysis of plates with piezo-patches

Directory of Open Access Journals (Sweden)

Maria Cinefra

2015-04-01

Full Text Available The present article considers the free-vibration analysis of plate structures with piezoelectric patches by means of a plate finite element with variable through-the-thickness layer-wise kinematic. The refined models used are derived from Carrera’s Unified Formulation (CUF and they permit the vibration modes along the thickness to be accurately described. The finite-element method is employed and the plate element implemented has nine nodes, and the mixed interpolation of tensorial component (MITC method is used to contrast the membrane and shear locking phenomenon. The related governing equations are derived from the principle of virtual displacement, extended to the analysis of electromechanical problems. An isotropic plate with piezoelectric patches is analyzed, with clamped-free boundary conditions and subjected to open- and short-circuit configurations. The results, obtained with different theories, are compared with the higher-order type solutions given in the literature. The conclusion is reached that the plate element based on the CUF is more suitable and efficient compared to the classical models in the study of multilayered structures embedding piezo-patches.

Using GPS, tide gauge and altimetry data to constrain subduction parameters at the Vanuatu plate boundary.

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Ballu, V.; Bouin, M.; Baillard, C.; Calmant, S.; Pelletier, B.; Crawford, W. C.; Kanas, T.; Garaebiti, E.

2012-12-01

two offshore sites using absolute pressure gauges. The sites - Wusi and Sabine Banks - are installed beneath altimetry satellite tracks, Wusi Bank on the over-riding plate and Sabine Bank on the subducting plate. The difference in the pressure records between the sites shows that Wusi Bank subsides by 11 +/- 3 mm/yr with respect to Sabine Bank. We combined the water depths derived from the pressure measurements with altimetry-derived sea-surface heights to tie these heights to a global reference frame: Wusi Bank subsides and Sabine Bank's vertical motion is near zero. Using a 2D elastic model and a finite-element code, we used the gradient of vertical deformation between the coast and the Wusi Bank site to discriminate between possible locked zone geometries. The best simple approximation is a 25° dipping, 30 km long fully locked zone, indicating that stress is currently accumulating west of Santo, Central Vanuatu. The movement of Wusi Bank is a key factor in constraining the dip and length of the locked zone, demonstrating the importance of offshore geodesy measurements.

Changes in Student Knowledge and Views of Geohazards, Societal Risks, and Monitoring at Active Plate Boundaries Using a Data-Rich Curriculum

Science.gov (United States)

Selkin, P. A.; Goodell, L. P.; Teasdale, R.

2015-12-01

The "Living on the Edge: Building Resilient Societies on Active Plate Margins" curriculum consists of six data-rich activities, each intended for a 50-minute class, in which students assess risk at active plate boundaries due to earthquakes and volcanoes. Developed as part of the InTeGrate NSF STEP Center the peer-reviewed, publically available materials (http://serc.carleton.edu/104296) have been used at several institutions in diverse classroom settings including small laboratory sections, large lecture courses, medium-sized upper division courses and professional development programs for middle and high school teachers. Pre- and post-instruction surveys measured content knowledge and geoscience literacy, self-efficacy in using geologic data to assess hazards and risk, and attitudes towards the value of monitoring plate margins. The activities have overall positive effects on knowledge of geohazard concepts. Views about the value of scientific practice also became more positive: 74% of students indicated they "agree" or "strongly agree" that monitoring geologic activity has value to them personally (even if they don't live on an active plate margin) and 94% indicated that such monitoring is valuable to society. Most became more confident in evaluating geologic hazard and risk (>60% of students self-described increased confidence by one or more Likert levels). Student knowledge of both the types and limits of data in forecasting geological hazards and their effects also improved. However, attitudes toward sustainability and geoscience careers did not change. Learning and attitudinal improvements are true for all classroom types, but the degree of change varies with class size and the amount of time spent on activities. Learning data and instructor feedback suggest that interactive classroom activities that use real-world data to address societally relevant issues increase student learning and enhance students' ability to synthesize scientific information.

Self-consistent model of the low-latitude boundary layer

International Nuclear Information System (INIS)

Phan, T.D.; Sonnerup, B.U.Oe.; Lotko, W.

1989-01-01

A simple two-dimensional, steady state, viscous model of the dawnside and duskside low-latitude boundary layer (LLBL) has been developed. It incorporates coupling to the ionosphere via field-aligned currents and associated field-aligned potential drops, governed by a simple conductance law, and it describes boundary layer currents, magnetic fields, and plasma flow in a self-consistent manner. The magnetic field induced by these currents leads to two effects: (1) a diamagnetic depression of the magnetic field in the equatorial region and (2) bending of the field lines into parabolas in the xz plane with their vertices in the equatorial plane, at z = 0, and pointing in the flow direction, i.e., tailward. Both effects are strongest at the magnetopause edge of the boundary layer and vanish at the magnetospheric edge. The diamagnetic depression corresponds to an excess of plasma pressure in the equatorial boundary layer near the magnetopause. The boundary layer structure is governed by a fourth-order, nonlinear, ordinary differential equation in which one nondimensional parameter, the Hartmann number M, appears. A second parameter, introduced via the boundary conditions, is a nondimensional flow velocity v 0 * at the magnetopause. Numerical results from the model are presented and the possible use of observations to determine the model parameters is discussed. The main new contribution of the study is to provide a better description of the field and plasma configuration in the LLBL itself and to clarify in quantitative terms the circumstances in which induced magnetic fields become important

Modeling Open-Loop MEMS Tunneling Accelerometer Based on Circular Plate

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Hossein Jodat Kordlar

2007-04-01

Full Text Available In this paper open-loop MEMS tunneling accelerometer was modeled based on a clamped micro circular plate with a tip tunneling at its centre. Mechanical behavior of the micro plate was studied deriving governing equation based on classic Kirchhoff thin plate theory and it was discretized using Galerkin method. Dynamic response of the proposed accelerometer due to step and harmonic external excitation was studied and the magnitude of the applied acceleration was identified by measuring of the changing of tunneling current. Obtained results show that the proposed tunneling accelerometer very sensitive and it can be measure acceleration with very high resolution but very small gap of tip tunneling limit the range of measurable acceleration.

RANS Modeling of Benchmark Shockwave / Boundary Layer Interaction Experiments

Science.gov (United States)

Georgiadis, Nick; Vyas, Manan; Yoder, Dennis

2010-01-01

This presentation summarizes the computations of a set of shock wave / turbulent boundary layer interaction (SWTBLI) test cases using the Wind-US code, as part of the 2010 American Institute of Aeronautics and Astronautics (AIAA) shock / boundary layer interaction workshop. The experiments involve supersonic flows in wind tunnels with a shock generator that directs an oblique shock wave toward the boundary layer along one of the walls of the wind tunnel. The Wind-US calculations utilized structured grid computations performed in Reynolds-averaged Navier-Stokes mode. Three turbulence models were investigated: the Spalart-Allmaras one-equation model, the Menter Shear Stress Transport wavenumber-angular frequency two-equation model, and an explicit algebraic stress wavenumber-angular frequency formulation. Effects of grid resolution and upwinding scheme were also considered. The results from the CFD calculations are compared to particle image velocimetry (PIV) data from the experiments. As expected, turbulence model effects dominated the accuracy of the solutions with upwinding scheme selection indicating minimal effects.!

The Importance of Lower Mantle Structure to Plate Stresses and Plate Motions

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Holt, W. E.; Wang, X.; Ghosh, A.

2016-12-01

Plate motions and plate stresses are widely assumed as the surface expression of mantle convection. The generation of plate tectonics from mantle convection has been studied for many years. Lithospheric thickening (or ridge push) and slab pull forces are commonly accepted as the major driving forces for the plate motions. However, the importance of the lower mantle to plate stresses and plate motions remains less clear. Here, we use the joint modeling of lithosphere and mantle dynamics approach of Wang et al. (2015) to compute the tractions originating from deeper mantle convection and follow the method of Ghosh et al. (2013) to calculate gravitational potential energy per unit area (GPE) based on Crust 1.0 (Laske et al., 2013). Absolute values of deviatoric stresses are determined by the body force distributions (GPE gradients and traction magnitudes applied at the base of the lithosphere). We use the same relative viscosity model that Ghosh et al. (2013) used, and we solve for one single adjustable scaling factor that multiplies the entire relative viscosity field to provide absolute values of viscosity throughout the lithosphere. This distribution of absolute values of lithosphere viscosities defines the magnitudes of surface motions. In this procedure, the dynamic model first satisfies the internal constraint of no-net-rotation of motions. The model viscosity field is then scaled by the single factor until we achieve a root mean square (RMS) minimum between computed surface motions and the kinematic no-net-rotation (NNR) model of Kreemer et al. (2006). We compute plate stresses and plate motions from recently published global tomography models (over 70 based on Wang et al., 2015). We find that RMS misfits are significantly reduced when details of lower mantle structure from the latest tomography models are added to models that contain only upper and mid-mantle density distributions. One of the key reasons is that active upwelling from the Large Low Shear