Research on Aerodynamic Noise Reduction with Non-Smooth Surfaces of Exterior Rearview Mirror Cover

2012 ◽  
Vol 430-432 ◽  
pp. 1768-1772
Author(s):  
Xin Chen ◽  
Lei Yang
Keyword(s):  
Transient Flow ◽  
Noise Spectrum ◽  
Aerodynamic Noise ◽  
Smooth Surfaces ◽  
Acoustic Model ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Computational Fluid Dynamics Cfd ◽  
Rearview Mirror

In order to research the car interior aerodynamic noise, the non-smooth surfaces of exterior rearview mirror are studied based on computational fluid dynamics (CFD) and computational aero acoustic (CAA) method. The large eddy simulation model was used to construct transient flow field, and the FW-H acoustic model was used to analyze the aerodynamic noise generated by the exterior rearview mirror. From the comparative analysis on aerodynamic noise spectrum of every monitor point, a conclusion can be drawn that the rearview mirror with non-smooth surfaces can improve the performance of car interior aerodynamic noise.

Applied-Information Technology with Different Sub-Grid Models in Large Eddy Simulation

2014 ◽  
Vol 978 ◽  
pp. 231-235
Author(s):  
Xin Chen ◽  
Yuan Qiang Wu ◽  
Huai Yu Wang ◽  
Hou Yu Ning
Keyword(s):  
Experimental Data ◽  
Large Eddy Simulation ◽  
Dynamic Stress ◽  
Aerodynamic Noise ◽  
Noise Prediction ◽  
Wind Noise ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Rearview Mirror ◽  
The Difference

Aiming at different sub-grid models of large eddy simulation, numerical simulation of aerodynamic noise caused by rearview mirror was conducted by the large eddy simulation. Compared with experimental data, the results of four sub-grid models on rearview mirror simulation have the difference respectively. Studies have shown that simulation result using the Dynamic Stress Smagorinsky-Lilly model is closest to the experimental data, and the other three models have larger error. Using the Dynamic Stress Smagorinsky-Lilly model in large eddy simulation for predicting aerodynamic noise of rearview mirror is effective and feasible, which can be used as reference for subsequent rearview mirror wind noise prediction.

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.

Flow Patterns and Temperature Distribution in an Underground Metro Station

2018 ◽  
Author(s):  
Alaa Hasan ◽  
Tarek ElGammal ◽  
Ryoichi S. Amano ◽  
Essam E. Khalil
Keyword(s):  
Thermal Comfort ◽  
Thermal Conditions ◽  
Large Space ◽  
Metro Station ◽  
Air Conditioning System ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Computational Fluid Dynamics Cfd ◽  
Set Up ◽  
Les Model

Accurate control of thermal conditions in large space buildings like an underground metro station is a significant issue because passengers’ thermal comfort must be maintained at a satisfactory level. The large eddy simulation (LES) model was adopted while using the computational fluid dynamics (CFD) software “STAR CCM+” to set up a CFD station model to predict static air temperature, velocity, relative humidity and predicted mean vote (PMV), which indicates the passengers’ thermal comfort. The increase in the number of passengers using the model station is taken into consideration. The studied cases covered all the possible modes of the station box, these modes are (1) the station box is empty of trains, (2) the presence of one train inside the station box, (3) the presence of two trains inside the station box. The objective is to bring the passengers’ thermal comfort in all modes to the acceptable level. The operation of under platform exhaust (UPE) system is considered in case of train presence inside the station box. The use of UPE is more energy efficient than depending entirely on the air conditioning system to maintain the thermal conditions comfortable.

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.

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