DETERMINATION OF THE PM10 URBAN THRESHOLD VELOCITY OF RE-SUSPENSION IN AN INNER PART OF URBAN AREA

In this paper authors focus on determination of the threshold velocity of re-suspension for particles 10 m in an urban street canyon with two-way traffic. The urban wind threshold velocity of re-suspension is derived from a long-term measurement carried out in the city of Brno. A numerical modelling based on the finite volume method is used for a detail study of the relation between a wind velocity above buildings roofs and an air velocity just above the ground surface. The predicted threshold air velocity of re-suspension at the bottom part of the studied street canyon is compared with two theoretical studies on particle re-suspension. Calculations are carried out for perpendicular, longitudinal and oblique (45°) wind direction with and without inclusion of traffic dynamic. To simulate traffic, an original model developed previously by the authors is used that takes into account traffic density, speed of cars and number of traffic lanes

Meshfree method for computational aeroacoustics using lee for the solution of noise propagation

Meshfree Finite point method (FPM) has been used for the solution of sound (noise) propagation, which can be modeled by linearized Euler equations (LEE). Important property of a numerical method for simulation of sound propagation is the capability to reach the high order of accuracy. In this paper we present the accuracy improvements of FPM using the reconstruction of variables in the Riemann solver by Taylor polynomial. Order of the derived meshfree method will be verified on 2D Acoustic pulse problem which serves as a benchmark problem with known analytical solution

2D numerical investigation of liquid dispersion in rotating packed bed and its comparison with experimental measurements using high-speed camera

Study deals with liquid dispersion of water in unstructured wire mesh of rotating packed bed, experimentally investigated using high speed camera. Dispersed water in outer region of rotating packed bed were captured by high-speed camera and droplet size were investigated using image processing. Numerical simulations were performed on two – dimensional plane with similar geometry characteristics (diameter and distance between each wire). Volume of fluid method was used to describe a multiphase behaviour of phenomena and turbulence was modelled using k-epsilon model. Results of both were compared on basis of frequency distribution of individual size fraction of dispersed water in outer region of rotating packed bed and its velocities. Discussion was focused on possibility of 2D numerical investigation and possibility of its comparison with experimental measurement

Large eddy simulation of turbulent particle-laden channel flow considering turbulence modulation by particles

Large Eddy Simulation of vertical turbulent channel flow laden with particles are performed. The number of particles is chosen very large and the volume fraction of particles is high enough for consideration of two-way coupling. This means that the particles are influenced by fluid and vice versa. The inter-particle collisions are neglected. The Euler-Lagrange method is adopted, which means that the fluid is considered to be continuum (Euler approach) and for each individual particle is solved Lagrangian equation of motion. Particles are considered to be spherical. The simulations are performed for different volume fractions of particles in the channel. The results are compared to the single-phase channel flow in order to investigate the effect of the particles on the turbulence statistics of the carrier phas