A. Hyll and V. Horák
The phenomenon of the in-flight icing can affect all types of aircraft. Presence of the ice accretion on wings can lead to performance degradation. Thus, it is important to understand how the different ice shapes affect aerodynamic characteristics. The prediction of the ice accretion on the wing with flaps of different position was made by the in-house code ICE 4.1. The two-dimensional CFD simulation was used for the study of aerodynamic performance degradation of multi-element iced airfoil. The results are discussed and some of them are compared with the wind tunnel testing.
Keywords: Aerodynamics, aircraft icing, performance degradation
Certain Problems in Infrastructure Management of the Armed Forces of the Czech Republic on Military Bases in Foreign Operations
This article is devoted to certain infrastructure management options of the Armed Forces of the Czech Republic and designing military bases in foreign operations. In connection with the Defence Research Project, software architecture based on databases is projected, which is designated for special requirements of the Engineering Corps. At some level there must be coherence within the All-military Logistics Information System; moreover, to increase the efficiency of the process of base design, it is possible to use other options and software tools. To select the optimal base design option the multicriteria decision-making may be used, whose principles are elaborated on in the article.
Keywords: Military base, base design, variant, multi-criteria decision-making
J. Hub and J. Komenda
The article presents an experimental and numerical approach to estimate ballistic limits of handgun hollow point bullet Action 5 penetrating the target representing a transport airplane fuselage and a forward obstacle. The target containing the composite sidewall, the insulation glass wool layer and the duralumin skin plate is perforated in two combinations – directly and using forward obstacle in form of ballistic gel as substitute biological material to achieve the conditions of firing on-board by Air Marshals, for instance. The ballistic resistance of the fuselage structure fired directly is very poor and in case of firing the gel block first is limited to some extend due to expansion ability of the bullet. The simulation using Finite Element Method system Ansys Autodyn v.14 introduces 2D model presenting the estimation of the ballistic limit in form of gel block thickness for particular combinations of the target based on experiments.
Keywords: Handgun ammunition, Action 5, hollow point bullet, ballistic limit, aircraft fuselage, gel, FEM
M. Štiavnický and R. Löričíková
The paper deals with numerical and analytical analysis of sliding wedge breech mechanism response during one shot fired from 100mm cannon. The model of the breech together with gun tube was modelled in LS-Dyna environment using available commands for mesh generation and for handling boundary conditions including contact surfaces. Only the components that significantly affect the force redistribution are modelled for the analysis. The explicit finite element method was used to retrieve stresses and deformations of the breech. The emphasis was put on the breech block which was the critical phenomenon. The numerical results were compared to analytic solution which is commonly used in the process of designing sliding wedge breech blocks. The response of the gun as a whole was also analysed.
Keywords: Sliding wedge breech block, 100mm cannon, simulation, finite element method, LS-Dyna
Apertures with Laval Nozzle and Circular Orifice in Secondary Electron Detector for Environmental Scanning Electron Microscope
P. Vyroubal, J. Maxa, V. Neděla, J. Jirák and K. Hladká
Environmental scanning electron microscopes offer wide possibilities for the exploration of various types of specimens, especially non-conductive and wet specimens containing different material phases. The evaluation of pressure on the secondary electrons trajectory is one of the important parameters in design of scintillation detector of secondary electrons. The final process is influenced by the size and the shape of the apertures used to separate areas with different pressure gradient. This article is focused on the comparison of the aperture with circular orifice and aperture with Laval nozzle.
Keywords: Aperture, Laval nozzle, circular orifice, pressure, detector, Mach number, flow, trajectory of secondary electrons
R. Dandoš, H. Staňková, P. Černota and M. Subíková
The article describes a creation of spatial visualisation of the infantry blockhouse OP – S 25 “U trigonometru”. The history of both the Czechoslovak fortification and the infantry blockhouse is briefly mentioned here. The main part of this contribution deals with field work to collect input data and with their processing during creation of a 3D model. A demonstration of the final model from all cardinal directions follows. The conclusion describes possibilities of using the visualisation of the infantry blockhouse OP – S 25 “U trigonometru” not only from the historical, but also from the modern point of view.
Keywords: Spatial, 3D model, historical, infantry blockhouse, surveying, visualisation
L. Čermák, P. Götz and L. Šimon
The aim of this study was the development and the preparation for serial production of a new generation of pyro-generators with a new assembling technology and with new properties, which were requested by force ministries. It means multiple uses of basic components and technology with new lacquers, mastics and glues for product assembling.
Keywords: Pyro-generator, cartridge, pyro-cartridge, destruction device
Influence of Barrel Vibration on the Barrel Muzzle Position at the Moment when Bullet Exits Barrel
M. Štiavnický and P. Lisý
By numerical simulation, influence of the barrel fixing on barrel vibration when a bullet moves down the barrel during shot will be investigated. Both the barrel and bullet were modelled by LS-DYNA software. The barrel is modelled as perfectly straight without any manufacturing deviations. The bullet is a NATO standard 5.56mm calibre consisting of brass jacket and lead core. Gas pressure is applied on the barrel and bullet base. As the bullet is forced into the lands of the barrel, the bullet obtains forward momentum and rotational speed. Interaction of the bullet with the barrel acts as excitation force and the barrel vibrates. In this article, two modifications of the barrels with and without the attachments are shown. These all have an influence on the barrel behaviour during shot mainly at the moment when the bullet leaves the barrel muzzle. Also some impulses are given to the barrel when the bullet leaves the barrel muzzle.
Keywords: Assault rifle, barrel vibration, numerical simulation