Model of Ground Handling Processes and Establishing Safety Mechanisms

The following paper focuses on the operational safety issues in the aircraft ground handling process. Ground handling is a critical phase in terms of operational safety, however, severe injuries or even fatal accidents are rare. According to the available data, during a handling process a quite large number of incidents have as an outcome a damaged aircraft, which slows down the following processes and fluency of the relevant procedures. The financial costs in case of even the slightest damage are significantly high.In order to implement different approach to safety management of ground handling companies, firstly a process analysis was performed using the Systems-Theoretic Accident Model and Process (STAMP) model. The STAMP model offers a different approach to operational safety as opposed to a traditional approach. STAMP approaches failure as a control error. The individual processes are designed for possible future STPA analysis. The processes were modelled according to the publicly available sources, and further improved with the expertise and experience from a real operation. A list of potential deviations is added to the processes or individual activities. Coordination processes between the ground handling company and the airport were also discussed. An operational measure designed to increase operational safety is proposed for selected cases

Grid turbulence studied by Particle Image Velocimetry

We studied the grid-generated turbulence by using Particle Image Velocimetry (PIV) technique. We test on this already well studied flow the new ways of analyzing spatially resolved PIV data, such as the spatial spectra and structure functions. We compare some of the turbulence characteristics with results of Laser Doppler Anemometry (LDA)

Secondary flow of second kind in a short channel observed by PIV

By using the Stereo Particle Image Velocimetry (PIV) technique we observe the secondary flow of second kind in a corner of a channel of square cross-section. The boundary layer thickness is much lower than the channel size. Therefore, the flow is still developing, not filling the entire channel cross-section, which is the case more widely reported in literature studied in a very long channel. The non-linear secondary effects of interacting boundary layers are observed as a single stream-wise vortex close to the channel corner in case of laminar boundary layers. In the case of turbulent boundary layers, the secondary flow takes shape of a symmetric pair of counter-rotating vortices. This pattern is observable only in the average velocity field, while the instantaneous ones display large amount of vortices, whose spatial distribution close to the corner in dependence on their orientation leads to statistically emergent net vorticity. At the same time, this pattern is reproduced by using a numerical simulation

Vliv sekundárního proudění na mezní vrstvu v kanále

Boundary layer in developing channel flow of air is experimentally studied by using the Stereo Particle Image Velocimetry (PIV) technique. The measurement is performed at fixed distance 400 mm from the channel inlet and the Reynolds number (based on the channel length, i.e. the distance from the boundary layer origin) is controlled via the imposed velocity. Re ranges from 8·104 to 8·105. The displacement boundary layer thickness δ varies from 1.7 to 2.5 mm while the momentum one θ from 0.9 to 1.3 mm. It is found, that the critical Reynolds number of transition to turbulence of the boundary layer is lowered by the vicinity of the other perpendicular wall of the square channel; more accurately - it is accelerated by the larger-scale secondary flow, which results into turbulence at slightly lower Reynolds numbers. The laminar-turbulent transition is first apparent on the profiles of the turbulent kinetic energy, later on the velocity profiles. The mechanism might be probably such, that the turbulent flow structures generated in the secondary flow in the corner via Richardson energy transfer mechanism migrate into the laminar boundary layer. While the large- scale structures cannot feed from the limited-size boundary layer, the smaller ones can strengthen there

Visualization of secondary flow in a corner of a channel

We report observation of secondary flow in one corner of developing channel air flow. Length of the channel, i.e. length of boundary layer, is 400?mm, which is 3.2 times the channel cross-sectional size. Three components of velocity are measured by using a Stereo Particle Image Velocimetry (PIV) technique in the measurement area of size 24×22?mm, which is perpendicular to the direction of main flow in the channel. The Reynolds number based on the length of the channel ranged from 4·104 to 8·105 and has been controlled via imposed velocity. At low Reynolds number we observe a laminar corner vortex having at all velocities the same orientation. This symmetry breaking is probably caused by an imperfectness of the experimental device. At Reynolds number around 8·104 this vortex starts to slightly variate its strength and position causing transition of boundary layers into turbulence at Re = 1.1·105. At higher Re this laminar vortex disappears from the instantaneous velocity fields, but it is still apparent in the averaged ones. It gets smaller and another oppositely oriented vortex forms; note that the second vortex is not observed in the instantaneous velocity fields, only in the ensemble average. At even higher Re, this secondary flow structure is smaller than the turbulent boundary layers, but its shape of a pair of counter-rotating vortices is conserved probably being a seed for secondary flow between fully developed boundary layers reported in the literature for longer channels with fully developed flow