Resistance of a plate in parallel flow at low Reynolds numbers

The present paper gives the results of measurements of the resistance of a plate placed parallel to the flow in the range of Reynolds numbers from 10 to 2300; in this range the resistance deviates from the formula of Blasius. The lower limit of validity of the Blasius formula is determined and also the increase in resistance at the edges parallel to the flow in the case of a plate of finite width

Odpor Podélné Obtékané Desky Pri Malych Reynoldsovych Císlech

The present paper gives the results of measurements of the resistance of a plate placed parallel to the flow in the range of Reynolds numbers from 10 to 2300; in this range the resistance deviates from the formula of Blasius. The lower limit of validity of the Blasius formula is determined and also the increase in resistance at the edges parallel to the flow in the case of a plate of finite width

Spatio-Temporal Modelling of Dust Transport over Surface Mining Areas and Neighbouring Residential Zones

Projects focusing on spatio-temporal modelling of the living environment need to manage a wide range of terrain measurements, existing spatial data, time series, results of spatial analysis and inputs/outputs from numerical simulations. Thus, GISs are often used to manage data from remote sensors, to provide advanced spatial analysis and to integrate numerical models. In order to demonstrate the integration of spatial data, time series and methods in the framework of the GIS, we present a case study focused on the modelling of dust transport over a surface coal mining area, exploring spatial data from 3D laser scanners, GPS measurements, aerial images, time series of meteorological observations, inputs/outputs form numerical models and existing geographic resources. To achieve this, digital terrain models, layers including GPS thematic mapping, and scenes with simulation of wind flows are created to visualize and interpret coal dust transport over the mine area and a neighbouring residential zone. A temporary coal storage and sorting site, located near the residential zone, is one of the dominant sources of emissions. Using numerical simulations, the possible effects of wind flows are observed over the surface, modified by natural objects and man-made obstacles. The coal dust drifts with the wind in the direction of the residential zone and is partially deposited in this area. The simultaneous display of the digital map layers together with the location of the dominant emission source, wind flows and protected areas enables a risk assessment of the dust deposition in the area of interest to be performed. In order to obtain a more accurate simulation of wind flows over the temporary storage and sorting site, 3D laser scanning and GPS thematic mapping are used to create a more detailed digital terrain model. Thus, visualization of wind flows over the area of interest combined with 3D map layers enables the exploration of the processes of coal dust deposition at a local scale. In general, this project could be used as a template for dust-transport modelling which couples spatial data focused on the construction of digital terrain models and thematic mapping with data generated by numerical simulations based on Reynolds averaged Navier-Stokes equations

Detailed analysis of POD method applied on turbulent flow

Proper orthogonal decomposition (POD) of a very turbulent flow inside a street canyon is performed. The energy contribution of each mode is obtained. Also, physical meaning of the POD result is clarified. Particular modes of POD are assigned to the particular flow events like a sweep event, a vortex behind a roof or a vortex at the bottom of a street. Test of POD sensitivity to the acquisition time of data records is done. Test with decreasing sample frequency is also executed. Further, interpolation of POD expansion coefficient is performed in order to test possible increase in sample frequency and get new information about the flow from the POD analysis. We tested a linear and a spline type of the interpolation and the linear one carried out a slightly better result

Detailed analysis of POD method applied on turbulent flow

Proper orthogonal decomposition (POD) of a very turbulent flow inside a street canyon is performed. The energy contribution of each mode is obtained. Also, physical meaning of the POD result is clarified. Particular modes of POD are assigned to the particular flow events like a sweep event, a vortex behind a roof or a vortex at the bottom of a street. Test of POD sensitivity to the acquisition time of data records is done. Test with decreasing sample frequency is also executed. Further, interpolation of POD expansion coefficient is performed in order to test possible increase in sample frequency and get new information about the flow from the POD analysis. We tested a linear and a spline type of the interpolation and the linear one carried out a slightly better result