scholarly journals Numerical Simulations as Tool to Predict Chemical and Radiological Hazardous Diffusion in Case of Nonconventional Events

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
J.-F. Ciparisse ◽  
A. Malizia ◽  
L. A. Poggi ◽  
O. Cenciarelli ◽  
M. Gelfusa ◽  
...  
Keyword(s):  
Industrial Applications ◽  
Gas Release ◽  
Open Environment ◽  
Nuclear Explosive ◽  
Dust Mobilization ◽  
Computational Fluid Dynamics Simulations ◽  
Dangerous Substances ◽  
Dynamics Simulations ◽  
Pure Research ◽  
Good Agreement

CFD (Computational Fluid Dynamics) simulations are widely used nowadays to predict the behaviour of fluids in pure research and in industrial applications. This approach makes it possible to get quantitatively meaningful results, often in good agreement with the experimental ones. The aim of this paper is to show how CFD calculations can help to understand the time evolution of two possible CBRNe (Chemical-Biological-Radiological-Nuclear-explosive) events: (1) hazardous dust mobilization due to the interaction between a jet of air and a metallic powder in case of a LOVA (Loss Of Vacuum Accidents) that is one of the possible accidents that can occur in experimental nuclear fusion plants; (2) toxic gas release in atmosphere. The scenario analysed in the paper has consequences similar to those expected in case of a release of dangerous substances (chemical or radioactive) in enclosed or open environment during nonconventional events (like accidents or man-made or natural disasters).

Experimental and Numerical Investigation on the Effects of the Seeding Properties on LDA Measurements

2005 ◽  
Vol 127 (3) ◽  
pp. 514-522 ◽  
Author(s):  
Angelo Algieri ◽  
Sergio Bova ◽  
Carmine De Bartolo
Keyword(s):  
Particle Size ◽  
High Performance ◽  
Laser Doppler Anemometry ◽  
Two Phase ◽  
Large Particles ◽  
Computational Fluid Dynamics Simulations ◽  
Influence Measurement ◽  
Dynamics Simulations ◽  
Commercial Device ◽  
Good Agreement

The characteristics of the seeding particles, which are necessary to implement the laser Doppler anemometry (LDA) technique, may significantly influence measurement accuracy. LDA data were taken on a steady-flow rig, at the entrance of the trumpet of the intake system of a high-performance engine head. Five sets of measurements were carried out using different seeding particles: samples of micro-balloons sieved to give three different size ranges (25–63μm,90–200μm, and standard as received from the manufacturer 1–200μm), smoke from a “home-made” sawdust burner (particle size ⩽1μm), and fog from a commercial device (particle size around 1μm). The LDA data were compared with the results of two-phase computational fluid dynamics simulations. The comparison showed a very good agreement between the experimental and numerical results and confirmed that LDA measurements with particle dimensions in the order of 1μm or less represent the actual gas velocity. On the contrary, quite large particles, which are often used because of their cost and cleanliness advantages, introduce non-negligible errors.

Simulations of an Air-Ventilated Strut Crossing Water Surface at Variable Yaw Angles

2018 ◽  
Author(s):  
Konstantin I. Matveev ◽  
Miles P. Wheeler ◽  
Tao Xing
Keyword(s):  
Water Surface ◽  
Free Water ◽  
Suction Side ◽  
Complex Flow ◽  
Air Ventilation ◽  
History Of ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Lift Control ◽  
Good Agreement

Hydrodynamic devices intended to produce lift, control actions, or propulsion can be prone to air ventilation when operating near the free water surface. The atmospheric air may propagate to the low-pressure zones around these devices located under the nominal water level. This often leads to performance degradation of hydrodynamic systems. Modeling of air-ventilated flows is challenging due to complex flow nature and many factors in play. In this study, the computational fluid dynamics simulations are carried out for a surface-piercing strut at different yaw angles. At small yaw angles, the strut underwater surfaces remain wetted, whereas at large yaw and sufficiently high Froude numbers the suction side becomes air ventilated. At the intermediate yaw angles, both wetted and ventilated flow regimes are possible, and the existence of a specific state depends on the history of the process. The present computational results demonstrate good agreement with available experimental data.

scholarly journals Radiotracer Technology in Mixing Processes for Industrial Applications

2014 ◽  
Vol 2014 ◽  
pp. 1-15 ◽  
Author(s):  
N. Othman ◽  
S. K. Kamarudin
Keyword(s):  
Fluid Dynamics ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Mixing Time ◽  
Industrial Applications ◽  
Mixing Process ◽  
Mixing Processes ◽  
Mixing Performance ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

Many problems associated with the mixing process remain unsolved and result in poor mixing performance. The residence time distribution (RTD) and the mixing time are the most important parameters that determine the homogenisation that is achieved in the mixing vessel and are discussed in detail in this paper. In addition, this paper reviews the current problems associated with conventional tracers, mathematical models, and computational fluid dynamics simulations involved in radiotracer experiments and hybrid of radiotracer.

scholarly journals Effects of scale and Froude number on the hydraulics of waste stabilization ponds

2017 ◽  
Vol 77 (1) ◽  
pp. 239-247
Author(s):  
Isabela De Luna Vieira ◽  
Jhonatan Barbosa Da Silva ◽  
Carlos Nobuyoshi Ide ◽  
Johannes Gérson Janzen
Keyword(s):  
Froude Number ◽  
Reynolds Numbers ◽  
Transport Processes ◽  
Tracer Transport ◽  
Waste Stabilization Ponds ◽  
Stabilization Ponds ◽  
Waste Stabilization ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Good Agreement

Abstract This paper presents the findings from a series of computational fluid dynamics simulations to estimate the effect of scale and Froude number on hydraulic performance and effluent pollutant fraction of scaled waste stabilization ponds designed using Froude similarity. Prior to its application, the model was verified by comparing the computational and experimental results of a model scaled pond, showing good agreement and confirming that the model accurately reproduces the hydrodynamics and tracer transport processes. Our results showed that the scale and the interaction between scale and Froude number has an effect on the hydraulics of ponds. At 1:5 scale, the increase of scale increased short-circuiting and decreased mixing. Furthermore, at 1:10 scale, the increase of scale decreased the effluent pollutant fraction. Since the Reynolds effect cannot be ignored, a ratio of Reynolds and Froude numbers was suggested to predict the effluent pollutant fraction for flows with different Reynolds numbers.

scholarly journals Considerations for the design of bottom intake systems

2017 ◽  
Vol 20 (1) ◽  
pp. 232-245 ◽  
Author(s):  
José M. Carrillo ◽  
Luis G. Castillo ◽  
Juan T. García ◽  
Álvaro Sordo-Ward
Keyword(s):  
Numerical Models ◽  
Turbulence Models ◽  
Discharge Coefficients ◽  
Ansys Cfx ◽  
Laboratory Results ◽  
Computational Fluid Dynamics Simulations ◽  
The Many ◽  
Dynamics Simulations ◽  
Laboratory Experiences ◽  
Good Agreement

Abstract Knowing the scarcity of water in the southeast of Spain and how the rain occurs, we considered the design of intake systems in ephemeral riverbeds in order to try to capture part of the runoff flow. The intake systems generally consist of a rack located in the bottom of a river channel, so that the water collected passes down the rack and leads to the side channel. This behaviour has been studied in the laboratory by several researchers. However, due to the many effects that occur on the bars, it is not possible to analyse the whole problem of characterization with traditional methodologies. For instance, the wetted rack length necessary to collect a required flow presents important differences depending on what each author has considered relevant. Computational fluid dynamics simulations have been done to improve the knowledge of the hydraulic phenomenon observed in different laboratory experiences, for which we have previously calibrated the numerical models using laboratory results. The ANSYS CFX code was selected. Several two-equation turbulence models have been considered. The results show differences smaller than 1% in the wetted rack length, and discharge coefficients also present good agreement.

Multicanonical Molecular Dynamics Simulation Study of the Liquid-Solid and Solid-Solid Transitions in Lennard-Jones Clusters

2011 ◽  
Author(s):  
Toshihiro Kaneko ◽  
Kenji Yasuoka ◽  
Ayori Mitsutake ◽  
Xiao Cheng Zeng
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Transition Temperature ◽  
Peak Position ◽  
Temperature Curve ◽  
Dynamics Simulation ◽  
Lennard Jones ◽  
Dynamics Simulations ◽  
First Time ◽  
Good Agreement

Multicanonical molecular dynamics simulations are applied, for the first time, to study the liquid-solid and solid-solid transitions in Lennard-Jones (LJ) clusters. The transition temperatures are estimated based on the peak position in the heat capacity versus temperature curve. For LJ31, LJ58 and LJ98, our results on the solid-solid transition temperature are in good agreement with previous ones. For LJ309, the predicted liquid-solid transition temperature is also in agreement with previous result.

scholarly journals Hybrid POF/VLC Links Based on a Single LED for Indoor Communications

Photonics ◽  
2021 ◽  
Vol 8 (7) ◽  
pp. 254
Author(s):  
Juan Andrés Apolo ◽  
Beatriz Ortega ◽  
Vicenç Almenar
Keyword(s):  
Optical Power ◽  
Industrial Applications ◽  
Free Space Optics ◽  
Polymer Optical Fiber ◽  
Hybrid Fiber ◽  
Modulation Formats ◽  
Space Optics ◽  
Indoor Communications ◽  
Power Measurements ◽  
Good Agreement

A hybrid fiber/wireless link based on a single visible LED and free of opto-electronic intermediate conversion stages has been demonstrated for indoor communications. This paper shows the main guidelines for proper coupling in fiber/air/detector interfaces. Experimental demonstration has validated the design results with very good agreement between geometrical optics simulation and received optical power measurements. Different signal bandwidths and modulation formats, i.e., QPSK, 16-QAM, and 64-QAM, have been transmitted over 1.5 m polymer optical fiber (POF) and 1.5 m free-space optics (FSO). Throughputs up to 294 Mb/s using a 64-QAM signal have been demonstrated using a commercial LED, which paves the way for massive deployment in industrial applications.

scholarly journals Aerodynamic analysis of uphill drafting in cycling

2021 ◽  
Vol 24 (1) ◽  
Author(s):  
T. van Druenen ◽  
B. Blocken
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Scientific Literature ◽  
Sensitivity Analyses ◽  
Air Resistance ◽  
Wind Tunnel Measurements ◽  
Aerodynamic Effect ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

AbstractSome teams aiming for victory in a mountain stage in cycling take control in the uphill sections of the stage. While drafting, the team imposes a high speed at the front of the peloton defending their team leader from opponent’s attacks. Drafting is a well-known strategy on flat or descending sections and has been studied before in this context. However, there are no systematic and extensive studies in the scientific literature on the aerodynamic effect of uphill drafting. Some studies even suggested that for gradients above 7.2% the speeds drop to 17 km/h and the air resistance can be neglected. In this paper, uphill drafting is analyzed and quantified by means of drag reductions and power reductions obtained by computational fluid dynamics simulations validated with wind tunnel measurements. It is shown that even for gradients above 7.2%, drafting can yield substantial benefits. Drafting allows cyclists to save over 7% of power on a slope of 7.5% at a speed of 6 m/s. At a speed of 8 m/s, this reduction can exceed 16%. Sensitivity analyses indicate that significant power savings can be achieved, also with varying bicycle, cyclist, road and environmental characteristics.

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