CFD Simulation of Chemical Gas Dispersion Under Atmospheric Boundary Conditions

2019 ◽  
Vol 17 (05) ◽  
pp. 1940011
Author(s):  
George Xu ◽  
Arthur Lim ◽  
Harish Gopalan ◽  
Jing Lou ◽  
Hee Joo Poh
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Boundary Conditions ◽  
Atmospheric Boundary Layer ◽  
Schmidt Number ◽  
Cfd Simulation ◽  
Urban Setting ◽  
Mitigation Measures ◽  
Gas Dispersion ◽  
Turbulent Schmidt Number

Pollutant control is one of the key concerns in the design of buildings, for the sake of occupational health, safety and environment sustainability. In particular, risk analyses related to emergency leakage of chemicals from storage tanks or chemical processes have aroused increasing attentions in recent days, as well as the effectiveness of mitigation measures in order to eliminate, reduce and control the risks. In this paper, a CFD methodology with nonreactive chemical gases treated as passive scalars has been developed to simulate the gas dispersion across urban environments, subject to atmospheric boundary layer wind conditions. Special treatments to maintain the consistency in atmospheric boundary layer flow profiles, turbulence modeling and boundary conditions have also been accounted for. The proposed CFD methodology for gas dispersion has been implemented in the open source CFD code — OpenFOAM. It has been validated by modeling the gas dispersions for two urban-related test cases: the CODASC street canyon test case measured in a laboratory wind tunnel and the Mock Urban Setting Test (MUST) field experiment conducted in the desert area of Utah State. Effects of turbulent Schmidt number (Sct have been primarily addressed in this study. Statistical analyses about the discrepancies between predicted and experimental data have been carried out and statistical performance measures are used to quantify the accuracy of the proposed methodology. Simulations results from passive scalar transport equation demonstrate good agreement with experimental data, though tracer gases heavier than the atmospheric air were used in both the measurements. Furthermore, sensitivity tests also indicate that the accuracy of the simulation results is sensitive to the value of turbulent Schmidt number.

scholarly journals Determination of the Structural Characteristic of the Refractive Index of Optical Waves in the Atmospheric Boundary Layer with Remote Acoustic Sounding Facilities

Atmosphere ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 711 ◽  
Author(s):  
Odintsov ◽  
Gladkikh ◽  
Kamardin ◽  
Nevzorova
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Refractive Index ◽  
Atmospheric Boundary Layer ◽  
Structural Characteristic ◽  
Structural Characteristics ◽  
Acoustic Sounding ◽  
Optical Waves ◽  
Ultrasonic Anemometer

The structural characteristic of the refractive index of optical waves was calculated from experimental data on the microstructure of the temperature turbulence in the atmospheric boundary layer. The experimental data were obtained with an acoustic meteorological radar (sodar), ultrasonic anemometer–thermometer, and meteorological temperature profilometer. Estimates of the structural characteristics for different conditions in the atmospheric boundary layer are presented and were compared with model profiles.

scholarly journals On the algebraic perturbations in atmospheric boundary layer

2019 ◽  
Vol 55 (5) ◽  
pp. 62-75
Author(s):  
O. G. Chkhetiani ◽  
N. V. Vazaeva
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
High Resolution ◽  
Simple Model ◽  
Velocity Profile ◽  
Atmospheric Boundary Layer ◽  
Wind Field ◽  
Acoustic Sounding ◽  
Algebraic Instability ◽  
Scientific Station

A simple model for the development of submesoscale perturbations in the atmospheric boundary layer (ABL) is proposed. The growth of perturbations is associated with the shear algebraic instability of the wind velocity profile in the atmospheric boundary layer (ABL). For the scales of optimal perturbations (streaks) in the lower part of the ABL, estimates of their sizes were obtained about 100-200 m vertically and 300-600 m horizontally. Similar scales are noted for experimental data on the structure of the wind field in the lower part of the ABL, obtained in 2017, 2018 in the summer at the Tsimlyansk Scientific Station at the acoustic sounding of the atmosphere by the Doppler three-component minisodar of high resolution.

scholarly journals Mesoscale nesting interface of the PALM model system 6.0

2020 ◽  
Author(s):  
Eckhard Kadasch ◽  
Matthias Sühring ◽  
Tobias Gronemeier ◽  
Siegfried Raasch
Keyword(s):  
Boundary Layer ◽  
Boundary Conditions ◽  
Atmospheric Boundary Layer ◽  
Mesoscale Model ◽  
Model System ◽  
Convective Boundary ◽  
Convective Structures ◽  
Eddy Simulation ◽  
Synoptic Conditions ◽  
Turbulence Generation

Abstract. In this paper, we present a newly developed mesoscale nesting interface for the PALM model system 6.0, which enables PALM to simulate the atmospheric boundary layer under spatially heterogeneous and non-stationary synoptic conditions. The implemented nesting interface, which is currently tailored to the mesoscale model COSMO, consists of two major parts: (i) the preprocessor INIFOR, which provides initial and time-dependent boundary conditions from mesoscale model output and (ii) PALM's internal routines for reading the provided forcing data and superimposing synthetic turbulence to accelerate the transition to a fully developed turbulent atmospheric boundary layer. We describe in detail the conversion between the sets of prognostic variables, transformations between model coordinate systems, as well as data interpolation onto PALM's grid, which are carried out by INIFOR. Furthermore, we describe PALM's internal usage of the provided forcing data, which besides the temporal interpolation of boundary conditions and removal of any residual divergence includes the generation of stability-dependent synthetic turbulence at the inflow boundaries in order to accelerate the transition from the turbulence-free mesoscale solution to a resolved turbulent flow. We demonstrate and evaluate the nesting interface by means of a semi-idealized benchmark case. We carried out a large-eddy simulation (LES) of an evolving convective boundary layer on a clear-sky spring day. Besides verifying that changes in the inflow conditions enter into and successively propagate through the PALM domain, we focus our analysis on the effectiveness of the synthetic turbulence generation. By analysing various turbulence statistics, we show that the inflow in the present case is fully adjusted after having propagated for about 1.5 eddy turn-over times downstream, which corresponds well to other state-of-the-art methods for turbulence generation. Furthermore, we observe that numerical artefacts in the form of under-resolved convective structures in the mesoscale model enter the PALM domain, biasing the location of the turbulent up- and downdrafts in the LES. With these findings presented, we aim to verify the mesoscale nesting approach implemented in PALM, point out specific shortcomings, and build a baseline for future improvements and developments.

A contribution to the problem of turbulent mass transfer at high values of the Schmidt number and to the hydrodynamics of the turbulent boundary layer

1986 ◽  
Vol 51 (1) ◽  
pp. 75-80 ◽  
Author(s):  
Václav Kolář ◽  
František Vašák ◽  
Zdeněk Brož
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Mass Transfer ◽  
Turbulent Boundary Layer ◽  
Transition Layer ◽  
Schmidt Number ◽  
Interface Parameters ◽  
Turbulent Mass Transfer

It has been shown in the paper that under the turbulence (Re > 104) and at high values of the Schmidt number (Sc > 103), when the principal resistance to mass transfer is concentrated in the laminar layer immediately adhering to the interface, significant instabilities appear induced by the turbulent disturbances in the neighbouring transition layer, or by the discontinuities at the interface. Parameters have been determined characterizing this phenomenon on the basis of experimental data and their values have been compared with the data published in the literature as characteristics of the periodic viscous sublayers.

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