Svetlana A. Valger

Eine verständliche Visualisierung von Umweltdaten ist essenziell für die Stadtplanung, um komplexe Zusammenhänge zu verstehen und fundierte Entscheidungen zu ermöglichen. Das Zusammenspiel von 3D-Stadtmodellen, numerischer Strömungssimulation und Geo-Visualisierung ermöglicht eine interaktive und zugängliche Darstellung, die Planern hilft, nachhaltige Maßnahmen gezielt zu entwickeln und die urbane Lebensqualität zu verbessern.

Air pollution from motor vehicles in densely populated cities remains an urgent problem. In order to analyse and predict air quality at city scale, in-situ monitoring systems of pollutant concentrations and meteorological parameters are used, supplemented by mathematical prediction models and numerical simulations. However, local pollution processes in urban areas located close to roads often cannot be studied efficiently by monitoring due to the lack of a detailed sensor network. Numerical modelling at the urban micro-scale can provide detailed information on the pollutant transport around buildings, but requires high resolution building geometry and approaches to describe boundary and initial conditions for meteorological parameters, pollution sources and traffic intensity.In the present study, the authors focus on the numerical modelling of scenarios of pollutant transport from vehicles in the vicinity of an urban environment fragment in Stuttgart, Germany. The modelling methodology is based on a combination of classical CFD methods, sensor data on traffic intensity and vehicle statistics, and meteorological data. The traffic statistics used in the simulation include the number of vehicles per hour, divided into 11 vehicle classes, and vehicle speed data. The numerical simulation was performed using the 3D Reynolds-averaged Navier-Stokes equations with the k-ε turbulence model, supplemented by gaseous pollutant and particulate matter transport models. Ansys Fluent 2023R1 is used as the main CFD modelling tool.Non-stationary measured data of traffic on the considered road section were analysed and used to improve the numerical model. This allows the description of the daily air pollution dynamics within the urban fragment. This detailed simulation of unsteady aerodynamics and air quality at the urban micro-scale can be used to focus on indoor/outdoor air exchange problems, to optimise the transport system, and to contribute to the provision of sustainability and climate safety technologies in cities.

The transport and sedimentation of polystyrene particles with sizes in the range of 0.31 µm -10 µm in a ventilated room have been numerically investigated. For various particle diameters, flow velocity fields, and normalized concentration of particles in characteristic vertical and horizontal sections in the room were obtained. Numerical data were compared with experimental data on average particle concentrations in the room and at the room exits. It was shown that the numerical model adequately describes the experimental data and makes it possible to obtain a good quantitative agreement with the experimental data on the particle concentration averaged over the room and the concentration of particles at the exit from the considered region.

City canyon is a typical urban development configuration with two rows of tall buildings located along the road. Green infrastructure (tree alleys, green hedges/roofs/walls) inside urban canyons are a part of a city planning strategy, and it is actively used by architects around the world to ensure pedestrian comfort, reduce noise and the adverse effects of the urban heat island as well as to combat gaseous and dust pollution. However, a relatively large amount of data indicates a possible adverse effect of alleys with tall trees on the airflow characteristics inside urban canyons. The aim of the work is to numerically investigate the distribution of impurities from vehicles in urban canyons. The paper presents a description of microclimatic models built in ANSYS Fluent. It is based on the Reynolds-averaged Navier-Stokes equations closed with a two-equation k - ε realizable model, and the multi-species approach is used to simulate the impurities dispersion. Models are considered to take into account the influence of green spaces on the mean flow field and impurities concentration in the urban canyon. The simulation model is tested against the CODASC 2008 experimental data.

In the paper, the authors describe some results of a numerical simulation of the air flow around a bluff body mounted on a flat plate taking into account the injection of a tracer gas through a hole located in the substrate behind the body. The aim of this paper is to describe flow structure in the vicinity of a prism taking into account unstable stratification of the boundary layer which is characterized by a negative vertical temperature gradient. The results of numerical simulation for an unstable thermal state were compared with those obtained for the case of stable stratification for the same geometry configuration.

In the current study, the authors present a brief overview of the main factors that affect the processes of heat and mass transfer in the urban environment, and also consider the possibilities of using the ANSYS Fluent software to simulate urban climate problems. A test configuration, which corresponds to the open experimental data, was chosen for the numerical simulation. The boundary and initial conditions for the configuration were set in such a way as to reproduce the conditions of the weakly-unstable thermal stratification of the air flow. Satisfactory agreement of the experimental and simulation data on velocity and temperature profiles was obtained.

In the paper, numerical analysis is performed of 3D supersonic turbulent flows in a channel with a sudden expansion (backward-facing step) and jets injected transversally from the channel walls before the channel sudden expansion. The numerical simulations were performed under the conditions of experiments maid at the hot-shot wind tunnel IT-302M ITAM SB RAS. In the experiments, Mach number at the entrance of the channel was M = 4, the total temperature was T₀ = 1500÷2400 K, and the total pressure was P₀ = 1÷10 MPa. As secondary injecting gas, argon and hydrogen were used. The injectors were located before the backward facing step on the top and bottom walls of the model. Two-jet and eight-jet injection schemes were investigated experimentally and numerically. Mathematical modeling was carried out using ANSYS Fluent on the basis of the Reynolds-Averaged Navier-Stokes equations supplemented by the k-ω SST turbulence model. A comparison of the calculated and experimental data indicates that they are in satisfactory agreement. The calculated results made it possible to obtain a clearer understanding of the flow structure in the channel and reveal influence of the injection scheme and gas molecular weight on the mixing processes, pressure and temperature fields and the distribution of the mixture concentration over the length.

Nowadays, a lot of industrial accidents accompanied by explosions are happening throughout the world. Also, increase in the number of terrorist acts committed by means of explosions is observed. For improving safety of buildings and structures it is necessary to raise their resistance to explosive effects, as well as to be able to predict degree of potential damage upon explosive loads of various intensities. One of the principal goals in designing the structure resistant to explosive effects is to determine the dynamic response of structures to the impact of the blast wave. To this end, the transient pressure loads on the walls of the civil engineering structures are to be determined. The simulation of explosion is highly complicated, involving an explosion causing the shock wave propagation in air and then interaction with a structure. The engineering-level techniques permit one to estimate an explosive shock impact only for isolated buildings. The complexity of the building, the presence of nearby structures and the surrounding environment cannot be taken into account. Advanced computer aid engineering (CAE) software techniques combined with the latest methods of discrete three-dimensional city modelling permits one to simulate and analyse the effects of explosions in urban areas with a precision which previously was not possible. In the paper, the simulation results are presented of shock wave forming due to a spherical explosive charge and its propagation in the vicinity of geometrical configuration imitating an urban environment. The numerical simulation of a flow in the vicinity of prisms of different cross-sections and heights located on a flat plate was performed. The calculations are carried out in a three-dimensional non-viscous formulation using ANSYS software. On a basis of simulation results, a complex wave structures were analysed, and all the peculiarities of flows and pressure history records on building walls were described and explained. The possibility of a correct description of the non-stationary wave flow in the vicinity of the complex of obstacles is demonstrated. The results are compared with the experimental data on the pressure distribution in gauges located on the prism walls. The estimation of shock wave exposure intensity was performed to different objects.

Results of modeling the propagation of a shock wave formed by an explosion of a spherical charge of a high explosive in a semi-infinite space bounded by a flat substrate are reported. Problems of the...

A numerical study of the aerodynamics of a building of a complex shape has been performed taking into account the location of surrounding buildings. Simulation data based on full mathematical models of continuum mechanics have allowed us to reveal the spatial structure of the turbulent separated atmospheric flow in the neighborhood of the building, and to evaluate the wind load exerted on the building. A comparison between the calculated data for the air flow past the examined building located in a group of other buildings and past the same building at its isolated location was performed. Based on the obtained data, the impact of interference effects on the aerodynamics of buildings in urban areas was evaluated. A comparison of calculated with experimental data was performed. A satisfactory agreement between the two datasets was obtained.