scholarly journals The Contrail Mitigation Potential of Aircraft Formation Flight Derived from High-Resolution Simulations

Aerospace ◽  
2020 ◽  
Vol 7 (12) ◽  
pp. 170 ◽  
Author(s):  
Simon Unterstrasser
Keyword(s):  
Water Vapour ◽  
Climate Impact ◽  
Formation Flight ◽  
Large Set ◽  
Climate Effect ◽  
Mitigation Potential ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Close Proximity

Formation flight is one potential measure to increase the efficiency of aviation. Flying in the upwash region of an aircraft’s wake vortex field is aerodynamically advantageous. It saves fuel and concomitantly reduces the carbon foot print. However, CO2 emissions are only one contribution to the aviation climate impact among several others (contrails, emission of H2O and NOx). In this study, we employ an established large eddy simulation model with a fully coupled particle-based ice microphysics code and simulate the evolution of contrails that were produced behind formations of two aircraft. For a large set of atmospheric scenarios, these contrails are compared to contrails behind single aircraft. In general, contrails grow and spread by the uptake of atmospheric water vapour. When contrails are produced in close proximity (as in the formation scenario), they compete for the available water vapour and mutually inhibit their growth. The simulations demonstrate that the contrail ice mass and total extinction behind a two-aircraft formation are substantially smaller than for a corresponding case with two separate aircraft and contrails. Hence, this first study suggests that establishing formation flight may strongly reduce the contrail climate effect.

scholarly journals Far field wake vortex evolution of two aircraft formation flight and implications on young contrails

2020 ◽  
Vol 124 (1275) ◽  
pp. 667-702 ◽  
Author(s):  
S. Unterstrasser ◽  
A. Stephan
Keyword(s):  
Nitrogen Oxides ◽  
Water Vapour ◽  
Climate Impact ◽  
Large Eddy Simulations ◽  
Formation Flight ◽  
Wake Vortex ◽  
Far Field ◽  
Vortex Wake ◽  
Geometrical Properties ◽  
Large Eddy

AbstractLarge-eddy simulations (LES) have been employed to investigate the far-field four-vortex wake vortex evolution over 10min behind an aircraft formation. In formation flight scenarios, the wake vortex behaviour was found to be much more complex, chaotic and also diverse than in the classical single aircraft case, depending very sensitively on the formation geometry, i.e. the lateral and vertical offset of the two involved aircraft. Even though the case-by-case variability of the wake vortex behaviour across the various formation flight scenarios is large, the final plume dimensions after vortex dissolution are in general substantially different from those of single aircraft scenarios. The plumes are around 170 to 250m deep and 400m to 680m broad, whereas a single A350/B777 aircraft would produce a 480m deep and 330m broad plume. Formation flight plumes are thus not as deep, yet they are broader, as the vortices do not only propagate vertically but also in span-wise direction. Two different LES models have been employed independently and show consistent results suggesting the robustness of the findings. Notably, $CO_{2}$ emissions are only one contribution to the aviation climate impact among several others like contrails and emission of water vapour and nitrogen oxides, which would be all affected by the implementation of formation flight. Thus, we also highlight the differences in ice microphysical and geometrical properties of young formation flight contrails relative to the classical single aircraft case.

scholarly journals Large eddy simulation model for wind-driven sea circulation in coastal areas

2013 ◽  
Vol 20 (6) ◽  
pp. 1095-1112 ◽  
Author(s):  
A. Petronio ◽  
F. Roman ◽  
C. Nasello ◽  
V. Armenio
Keyword(s):  
Large Eddy Simulation ◽  
Simulation Model ◽  
Water Column ◽  
Eddy Viscosity ◽  
Vertical Mixing ◽  
Water Circulation ◽  
Bottom Surface ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Large Eddy

Abstract. In the present paper a state-of-the-art large eddy simulation model (LES-COAST), suited for the analysis of water circulation and mixing in closed or semi-closed areas, is presented and applied to the study of the hydrodynamic characteristics of the Muggia bay, the industrial harbor of the city of Trieste, Italy. The model solves the non-hydrostatic, unsteady Navier–Stokes equations, under the Boussinesq approximation for temperature and salinity buoyancy effects, using a novel, two-eddy viscosity Smagorinsky model for the closure of the subgrid-scale momentum fluxes. The model employs: a simple and effective technique to take into account wind-stress inhomogeneity related to the blocking effect of emerged structures, which, in turn, can drive local-scale, short-term pollutant dispersion; a new nesting procedure to reconstruct instantaneous, turbulent velocity components, temperature and salinity at the open boundaries of the domain using data coming from large-scale circulation models (LCM). Validation tests have shown that the model reproduces field measurement satisfactorily. The analysis of water circulation and mixing in the Muggia bay has been carried out under three typical breeze conditions. Water circulation has been shown to behave as in typical semi-closed basins, with an upper layer moving along the wind direction (apart from the anti-cyclonic veering associated with the Coriolis force) and a bottom layer, thicker and slower than the upper one, moving along the opposite direction. The study has shown that water vertical mixing in the bay is inhibited by a large level of stable stratification, mainly associated with vertical variation in salinity and, to a minor extent, with temperature variation along the water column. More intense mixing, quantified by sub-critical values of the gradient Richardson number, is present in near-coastal regions where upwelling/downwelling phenomena occur. The analysis of instantaneous fields has detected the presence of large cross-sectional eddies spanning the whole water column and contributing to vertical mixing, associated with the presence of sub-surface horizontal turbulent structures. Analysis of water renewal within the bay shows that, under the typical breeze regimes considered in the study, the residence time of water in the bay is of the order of a few days. Finally, vertical eddy viscosity has been calculated and shown to vary by a couple of orders of magnitude along the water column, with larger values near the bottom surface where density stratification is smaller.

scholarly journals The Parallelized Large-Eddy Simulation Model (PALM) version 4.0 for atmospheric and oceanic flows: model formulation, recent developments, and future perspectives

2015 ◽  
Vol 8 (8) ◽  
pp. 2515-2551 ◽  
Author(s):  
B. Maronga ◽  
M. Gryschka ◽  
R. Heinze ◽  
F. Hoffmann ◽  
F. Kanani-Sühring ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Simulation Model ◽  
Graphics Processing Units ◽  
Cloud Model ◽  
Parallel Computer ◽  
Future Perspectives ◽  
Current Version ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Large Eddy

Abstract. In this paper we present the current version of the Parallelized Large-Eddy Simulation Model (PALM) whose core has been developed at the Institute of Meteorology and Climatology at Leibniz Universität Hannover (Germany). PALM is a Fortran 95-based code with some Fortran 2003 extensions and has been applied for the simulation of a variety of atmospheric and oceanic boundary layers for more than 15 years. PALM is optimized for use on massively parallel computer architectures and was recently ported to general-purpose graphics processing units. In the present paper we give a detailed description of the current version of the model and its features, such as an embedded Lagrangian cloud model and the possibility to use Cartesian topography. Moreover, we discuss recent model developments and future perspectives for LES applications.

scholarly journals On Wind Turbine Loads During Thunderstorm Downbursts in Contrasting Atmospheric Stability Regimes

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2773 ◽  
Author(s):  
Nan-You Lu ◽  
Patrick Hawbecker ◽  
Sukanta Basu ◽  
Lance Manuel
Keyword(s):  
Wind Turbine ◽  
Structural Integrity ◽  
Atmospheric Stability ◽  
International Electrotechnical Commission ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Turbine Design ◽  
The Relationship ◽  
Inflow Conditions

Severe winds produced by thunderstorm downbursts pose a serious risk to the structural integrity of wind turbines. However, guidelines for wind turbine design (such as the International Electrotechnical Commission Standard, IEC 61400-1) do not describe the key physical characteristics of such events realistically. In this study, a large-eddy simulation model is employed to generate several idealized downburst events during contrasting atmospheric stability conditions that range from convective through neutral to stable. Wind and turbulence fields generated from this dataset are then used as inflow for a 5-MW land-based wind turbine model; associated turbine loads are estimated and compared for the different inflow conditions. We first discuss time-varying characteristics of the turbine-scale flow fields during the downbursts; next, we investigate the relationship between the velocity time series and turbine loads as well as the influence and effectiveness of turbine control systems (for blade pitch and nacelle yaw). Finally, a statistical analysis is conducted to assess the distinct influences of the contrasting stability regimes on extreme and fatigue loads on the wind turbine.

Simulation of Contaminant Dispersal in an Apartment Building

2004 ◽  
Author(s):  
Sankalp Soni ◽  
Bakhtier Farouk ◽  
Charles N. Haas
Keyword(s):  
Transport Processes ◽  
Apartment Building ◽  
Large Eddy Simulation Model ◽  
Spatial And Temporal Scales ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Contaminant Dispersal ◽  
Detailed Simulation ◽  
Time Histories ◽  
Ventilation Rates

Bio-terrorism events (like the 2001 anthrax attacks) accentuate the importance of countering these incidents. In order to develop reliable countermeasures for these events, it is essential to understand the associated transport processes. The transport processes involved pose challenges as they occur over wide ranges of spatial and temporal scales. CONTAMW, a multi zone indoor air quality and ventilation analysis program is used to predict the contaminant dispersal in an apartment building. Detailed simulation results and analysis of controlled release of propylene within a generic apartment building is presented. A zonal analysis is carried out for the entire apartment building (using CONTAMW) to obtain time histories of propylene concentration in different zones. The simulations provide the dispersion, transport and contaminant concentration within each zone of the apartment. This study also considers the effect of flow obstructions and ventilation rates on contaminant dispersal. The results are validated with the experimental results reported in Cybyk et al. (1999). We have also simulated propylene transport in the apartment with FDS, a large eddy simulation model.

scholarly journals PALM-USM v1.0: A new urban surface model integrated into the PALM large-eddy simulation model

2017 ◽  
Vol 10 (10) ◽  
pp. 3635-3659 ◽  
Author(s):  
Jaroslav Resler ◽  
Pavel Krč ◽  
Michal Belda ◽  
Pavel Juruš ◽  
Nina Benešová ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Simulation Model ◽  
Heat Wave ◽  
Urban Climate ◽  
Urban Surface ◽  
Surface Model ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Summer Heat ◽  
Large Eddy

Abstract. Urban areas are an important part of the climate system and many aspects of urban climate have direct effects on human health and living conditions. This implies that reliable tools for local urban climate studies supporting sustainable urban planning are needed. However, a realistic implementation of urban canopy processes still poses a serious challenge for weather and climate modelling for the current generation of numerical models. To address this demand, a new urban surface model (USM), describing the surface energy processes for urban environments, was developed and integrated as a module into the PALM large-eddy simulation model. The development of the presented first version of the USM originated from modelling the urban heat island during summer heat wave episodes and thus implements primarily processes important in such conditions. The USM contains a multi-reflection radiation model for shortwave and longwave radiation with an integrated model of absorption of radiation by resolved plant canopy (i.e. trees, shrubs). Furthermore, it consists of an energy balance solver for horizontal and vertical impervious surfaces, and thermal diffusion in ground, wall, and roof materials, and it includes a simple model for the consideration of anthropogenic heat sources. The USM was parallelized using the standard Message Passing Interface and performance testing demonstrates that the computational costs of the USM are reasonable on typical clusters for the tested configurations. The module was fully integrated into PALM and is available via its online repository under the GNU General Public License (GPL). The USM was tested on a summer heat-wave episode for a selected Prague crossroads. The general representation of the urban boundary layer and patterns of surface temperatures of various surface types (walls, pavement) are in good agreement with in situ observations made in Prague. Additional simulations were performed in order to assess the sensitivity of the results to uncertainties in the material parameters, the domain size, and the general effect of the USM itself. The first version of the USM is limited to the processes most relevant to the study of summer heat waves and serves as a basis for ongoing development which will address additional processes of the urban environment and lead to improvements to extend the utilization of the USM to other environments and conditions.

scholarly journals Stably Stratified Flows: A Model with No Ri(cr)*

2008 ◽  
Vol 65 (7) ◽  
pp. 2437-2447 ◽  
Author(s):  
V. M. Canuto ◽  
Y. Cheng ◽  
A. M. Howard ◽  
I. N. Esau
Keyword(s):  
Numerical Simulation ◽  
Large Eddy Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Mixing ◽  
Stratified Flows ◽  
The Other ◽  
Large Set ◽  
Eddy Simulation ◽  
Stably Stratified Flows ◽  
Large Eddy

Abstract A large set of laboratory, direct numerical simulation (DNS), and large eddy simulation (LES) data indicates that in stably stratified flows turbulent mixing exists up to Ri ∼ O(100), meaning that there is practically no Ri(cr). On the other hand, traditional local second-order closure (SOC) models entail a critical Ri(cr) ∼ O(1) above which turbulence ceases to exist and are therefore unable to explain the above data. The authors suggest how to modify the recent SOC model of Cheng et al. to reproduce the above data for arbitrary Ri.

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