Small-scale precipitation variability in the Alps: Climatology in comparison with semi-idealized numerical simulations

2008 ◽  
Vol 134 (636) ◽  
pp. 1865-1880 ◽  
Author(s):  
G. Zängl ◽  
D. Aulehner ◽  
C. Wastl ◽  
A. Pfeiffer
Keyword(s):  
Numerical Simulations ◽  
Precipitation Variability ◽  
Small Scale ◽  
The Alps

2D and 2.5D Numerical Simulations for Vortex-Induced Vibration (VIV) of a 1.5:1 Rectangular Cylinder

2021 ◽  
Author(s):  
Bowen Yan ◽  
Yangjin Yuan ◽  
Dalong Li ◽  
Ke Li ◽  
Qingshan Yang ◽  
...  
Keyword(s):  
Wind Speed ◽  
Numerical Simulations ◽  
Phase Difference ◽  
Vortex Shedding ◽  
Lift Force ◽  
Small Scale ◽  
Aerodynamic Damping ◽  
Displacement Response ◽  
Wind Speeds ◽  
Rectangular Cylinder

The semi-periodic vortex-shedding phenomenon caused by flow separation at the windward corners of a rectangular cylinder would result in significant vortex-induced vibrations (VIVs). Based on the aeroelastic experiment of a rectangular cylinder with side ratio of 1.5:1, 2-dimensional (2D) and 2.5-dimensional (2.5D) numerical simulations of the VIV of a rectangular cylinder were comprehensively validated. The mechanism of VIV of the rectangular cylinder was in detail discussed in terms of vortex-induced forces, aeroelastic response, work analysis, aerodynamic damping ratio and flow visualization. The outcomes showed that the numerical results of aeroelastic displacement in the cross-wind direction and the vortex-shedding procedure around the rectangular cylinder were in general consistence with the experimental results by 2.5D numerical simulation. In both simulations, the phase difference between the lift and displacement response increased with the reduced wind speed and the vortex-induced resonance (VIR) disappeared at the phase difference of approximately 180∘. The work done by lift force shows a close relationship with vibration amplitudes at different reduced wind speeds. In 2.5D simulations, the lift force of the rectangular cylinder under different wind speeds would be affected by the presence of small-scale vortices in the turbulence flow field. Similarly, the phase difference between lift force and displacement response was not a constant with the same upstream wind speed. Aerodynamic damping identified from the VIV was mainly dependent on the reduced wind speed and negative damping ratios were revealed at the lock-in regime, which also greatly influenced the probability density function (PDF) of wind-induced displacement.

Metal Flow and Die Filling in Coining of Micro Structures with and without Flash

2005 ◽  
Vol 6-8 ◽  
pp. 631-638 ◽  
Author(s):  
M. Thome ◽  
Gerhard Hirt ◽  
B. Rattay
Keyword(s):  
Numerical Simulations ◽  
Sheet Metal ◽  
Metal Forming ◽  
Production Systems ◽  
Metal Flow ◽  
Small Scale ◽  
Die Filling ◽  
Metal Plates ◽  
Micro Structures ◽  
Channel Structures

The continuing miniaturization of production systems and products poses a challenge for metal forming technologies to produce precise small scale products with microscopic geometric details. Thin metal plates with channel structures are considered to be typical examples for microfluidic applications [1,2]. In this study the coining process of sheet metal to produce channel and rib structures is examined in terms of geometrical die parameters and tool design. For this reason extensive experimental series and numerical simulations have been realized and evaluated.

Whistler Waves' Propagation in Plasmas With Systems of Small‐Scale Density Irregularities: Numerical Simulations and Theory

2019 ◽  
Vol 124 (6) ◽  
pp. 4739-4760 ◽  
Author(s):  
I. Yu. Zudin ◽  
T. M. Zaboronkova ◽  
M. E. Gushchin ◽  
N. A. Aidakina ◽  
S. V. Korobkov ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Small Scale ◽  
Whistler Waves ◽  
Waves Propagation

scholarly journals Retrospective analysis of a nonforecasted rain-on-snow flood in the Alps – a matter of model limitations or unpredictable nature?

2014 ◽  
Vol 18 (6) ◽  
pp. 2265-2285 ◽  
Author(s):  
O. Rössler ◽  
P. Froidevaux ◽  
U. Börst ◽  
R. Rickli ◽  
O. Martius ◽  
...  
Keyword(s):  
Snow Cover ◽  
Temperature Increase ◽  
Hydrological Model ◽  
Small Scale ◽  
The South ◽  
Flood Peak ◽  
Forecast Data ◽  
The Alps ◽  
Model Setup ◽  
Local Rainfall

Abstract. A rain-on-snow flood occurred in the Bernese Alps, Switzerland, on 10 October 2011, and caused significant damage. As the flood peak was unpredicted by the flood forecast system, questions were raised concerning the causes and the predictability of the event. Here, we aimed to reconstruct the anatomy of this rain-on-snow flood in the Lötschen Valley (160 km2) by analyzing meteorological data from the synoptic to the local scale and by reproducing the flood peak with the hydrological model WaSiM-ETH (Water Flow and Balance Simulation Model). This in order to gain process understanding and to evaluate the predictability. The atmospheric drivers of this rain-on-snow flood were (i) sustained snowfall followed by (ii) the passage of an atmospheric river bringing warm and moist air towards the Alps. As a result, intensive rainfall (average of 100 mm day-1) was accompanied by a temperature increase that shifted the 0° line from 1500 to 3200 m a.s.l. (meters above sea level) in 24 h with a maximum increase of 9 K in 9 h. The south-facing slope of the valley received significantly more precipitation than the north-facing slope, leading to flooding only in tributaries along the south-facing slope. We hypothesized that the reason for this very local rainfall distribution was a cavity circulation combined with a seeder-feeder-cloud system enhancing local rainfall and snowmelt along the south-facing slope. By applying and considerably recalibrating the standard hydrological model setup, we proved that both latent and sensible heat fluxes were needed to reconstruct the snow cover dynamic, and that locally high-precipitation sums (160 mm in 12 h) were required to produce the estimated flood peak. However, to reproduce the rapid runoff responses during the event, we conceptually represent likely lateral flow dynamics within the snow cover causing the model to react "oversensitively" to meltwater. Driving the optimized model with COSMO (Consortium for Small-scale Modeling)-2 forecast data, we still failed to simulate the flood because COSMO-2 forecast data underestimated both the local precipitation peak and the temperature increase. Thus we conclude that this rain-on-snow flood was, in general, predictable, but requires a special hydrological model setup and extensive and locally precise meteorological input data. Although, this data quality may not be achieved with forecast data, an additional model with a specific rain-on-snow configuration can provide useful information when rain-on-snow events are likely to occur.

scholarly journals The Fermi bubbles inflated by winds from the accretion flow in Sgr A*

2014 ◽  
Vol 10 (S312) ◽  
pp. 137-138
Author(s):  
Guobin Mou
Keyword(s):  
Numerical Simulations ◽  
Three Dimensional ◽  
Small Scale ◽  
Observational Constraints ◽  
Accretion Flow ◽  
Accretion Flows ◽  
The Past ◽  
Sgr A ◽  
Hydrodynamical Simulations

AbstractBy performing three-dimensional hydrodynamical simulations, we show that the Fermi bubbles could be inflated by winds launched from the “past” hot accretion flow in Sgr A*. The parameters of the accretion flow required in the model are consistent with those obtained independently from other observational constraints. The wind parameters are taken from small scale MHD numerical simulations of hot accretion flows.

Numerical Simulation of Fire in a Gasoline Storage Tank in Reduced-Scale

2017 ◽  
Vol 372 ◽  
pp. 11-20
Author(s):  
Renan Spilka Miranda ◽  
Maria Luiza Sperb Indrusiak ◽  
Felipe Roman Centeno
Keyword(s):  
Numerical Simulations ◽  
Burning Rate ◽  
Real Data ◽  
Type A ◽  
Anhydrous Ethanol ◽  
Flame Height ◽  
Small Scale ◽  
Mass Burning Rate ◽  
Fuel Mass ◽  
Type C

With the increasing demand for energy and fuels in Brazil, the storage of liquid fuels in multiple tanks is becoming much more usual, posing challenges from the point of view of fire safety. To study this type of phenomenon and to evaluate its possible causes, detecting failures such as ones in design and erection of storage systems or in detection and protection equipment, numerical simulations are performed based on real data. This work presents numerical simulations of a small-scale tank for gasoline storage, based on an experimental study reported in literature. The present research shows results related to temperature in the region adjacent to the tank on fire, fuel mass burning rate, heat release rate and average flame height. Comparisons are made between numerical and experimental results, as well as with available literature results for similar conditions. In addition to gasoline type C (which has anhydrous ethanol in its composition), also gasoline type A (anhydrous ethanol free) is considered. The results obtained for simulations with gasoline type A presented better agreement with literature data than those for gasoline type C, the differences being due to the variable composition of the type C fuel. For example, the reported fuel mass burning rate for gasoline in literature is 0.045 kg/(m2∙s), while the present simulations provided values of 0.038 kg/(m2∙s) for type C and 0.047 kg/(m2∙s) for type A.

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