Validation data for models of contaminant dispersal : scaling laws and data needs.

Predicting specific impulse distributions for spherical explosives in the extreme near-field using a Gaussian function

International Journal of Protective Structures ◽

10.1177/2041419621993492 ◽

2021 ◽

pp. 204141962199349

Author(s):

Jordan J Pannell ◽

George Panoutsos ◽

Sam B Cooke ◽

Dan J Pope ◽

Sam E Rigby

Keyword(s):

Scaling Laws ◽

Near Field ◽

Specific Impulse ◽

Gaussian Function ◽

Data Driven ◽

Blast Load ◽

Structural Deformation ◽

Load Prediction ◽

Validation Data ◽

Wide Range

Accurate quantification of the blast load arising from detonation of a high explosive has applications in transport security, infrastructure assessment and defence. In order to design efficient and safe protective systems in such aggressive environments, it is of critical importance to understand the magnitude and distribution of loading on a structural component located close to an explosive charge. In particular, peak specific impulse is the primary parameter that governs structural deformation under short-duration loading. Within this so-called extreme near-field region, existing semi-empirical methods are known to be inaccurate, and high-fidelity numerical schemes are generally hampered by a lack of available experimental validation data. As such, the blast protection community is not currently equipped with a satisfactory fast-running tool for load prediction in the near-field. In this article, a validated computational model is used to develop a suite of numerical near-field blast load distributions, which are shown to follow a similar normalised shape. This forms the basis of the data-driven predictive model developed herein: a Gaussian function is fit to the normalised loading distributions, and a power law is used to calculate the magnitude of the curve according to established scaling laws. The predictive method is rigorously assessed against the existing numerical dataset, and is validated against new test models and available experimental data. High levels of agreement are demonstrated throughout, with typical variations of <5% between experiment/model and prediction. The new approach presented in this article allows the analyst to rapidly compute the distribution of specific impulse across the loaded face of a wide range of target sizes and near-field scaled distances and provides a benchmark for data-driven modelling approaches to capture blast loading phenomena in more complex scenarios.

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Siphon Flows in Stratified Coronal Loops

International Astronomical Union Colloquium ◽

10.1017/s0252921100025288 ◽

1994 ◽

Vol 144 ◽

pp. 185-187

Author(s):

S. Orlando ◽

G. Peres ◽

S. Serio

Keyword(s):

Heat Flux ◽

Scaling Laws ◽

Flow Model ◽

Supersonic Flows ◽

Coronal Loops ◽

Characteristic Parameters

AbstractWe have developed a detailed siphon flow model for coronal loops. We find scaling laws relating the characteristic parameters of the loop, explore systematically the space of solutions and show that supersonic flows are impossible for realistic values of heat flux at the base of the upflowing leg.

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Equilibrium scaling laws for layered spin glasses

Journal de Physique I ◽

10.1051/jp1:1993231 ◽

1993 ◽

Vol 3 (10) ◽

pp. 2041-2062 ◽

Cited By ~ 1

Author(s):

M. J. Thill ◽

H. J. Hilhorst

Keyword(s):

Spin Glasses ◽

Scaling Laws ◽

Layered Spin

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Analysis of shear bands in slow granular flows using a frictional Cosserat model

MRS Proceedings ◽

10.1557/proc-627-bb4.3 ◽

2000 ◽

Vol 627 ◽

Author(s):

Prabhu R. Nott ◽

K. Kesava Rao ◽

L. Srinivasa Mohan

Keyword(s):

Scaling Laws ◽

Shear Bands ◽

Shear Layers ◽

Theoretical Description ◽

Field Variable ◽

Cosserat Continuum ◽

Momentum Balance ◽

Rigid Plastic ◽

Independent Field ◽

Cosserat Model

ABSTRACTThe slow flow of granular materials is often marked by the existence of narrow shear layers, adjacent to large regions that suffer little or no deformation. This behaviour, in the regime where shear stress is generated primarily by the frictional interactions between grains, has so far eluded theoretical description. In this paper, we present a rigid-plastic frictional Cosserat model that captures thin shear layers by incorporating a microscopic length scale. We treat the granular medium as a Cosserat continuum, which allows the existence of localised couple stresses and, therefore, the possibility of an asymmetric stress tensor. In addition, the local rotation is an independent field variable and is not necessarily equal to the vorticity. The angular momentum balance, which is implicitly satisfied for a classical continuum, must now be solved in conjunction with the linear momentum balances. We extend the critical state model, used in soil plasticity, for a Cosserat continuum and obtain predictions for flow in plane and cylindrical Couette devices. The velocity profile predicted by our model is in qualitative agreement with available experimental data. In addition, our model can predict scaling laws for the shear layer thickness as a function of the Couette gap, which must be verified in future experiments. Most significantly, our model can determine the velocity field in viscometric flows, which classical plasticity-based model cannot.

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