Abstract

Calculation of gas i.e. water distribution network is much more complex compared with branch-like distribution pipelines. In this paper is shown one more suitable method in comparison to modified Hardy Cross. Here shown method as well as modified Hardy Cross method are iterative methods. For balancing of network, approximately equal number of iteration are to be calculated after the here presented node-loop method as for the improved Hardy Cross. Main advantage of the node-loop method in comparison to improved Hardy Cross method is that the final result in each calculation is flow which is used directly as input parameter in the next iteration cycle. Disadvantage of the improved Hardy Cross method is that this flows are calculated indirectly using flow corrections which they need to be added after complicated algebraic scheme to the flows calculated in previous iteration.

Abstract

After the calculation of flows in a looped pipeline distribution network is done, very often velocity of fluid in some of the pipeline branches are undersized while in other are oversized. Hence, it is necessary to perform optimization of the pipes’ diameter to fit in range of suggested values. Suggested velocities for water flow in waterworks systems are 0.75-1.5 m/s, while in the case of natural gas flow in gas-pipelines this velocity limit is increased up to20 m/s. Problem of velocity in a gas pipeline is more complex in comparison to water velocity. This issue is caused by compressibility of gas. In this paper is shown procedure of diameters’ optimization after the modified Hardy Cross method. Difference in comparison to classical problem in which flow distribution is unknown is that on the contrary, in optimization problem flows are now constants while the diameters are treated as variables.

Abstract

This paper analyses the two-plane bending test to characterise the behaviour of unidirectional composite laminates. This test consists of a flat plate supported at four points to which a point force is applied at the centre. Currently, this configuration is not mathematically solved for orthotropic materials.

Initially, the displacements and bending moments produced in plates of isotropic material have been analysed by means of numerical simulation and analytical approach. The results obtained have been corroborated with other works published in the scientific literature.

Subsequently, the numerical models and the analytical development have been applied to plates formed with orthotropic material, in the configuration of the two-plane bending test. For this purpose, rectangular plates with different aspect ratio have been analysed in order to obtain different stress ratios along the fibre and perpendicular to it.

Finally, the results obtained both by numerical simulation and by the analytical approach have been compared with experimental tests carried out on unidirectional composite specimens made of epoxy matrix and carbon fibre.

Abstract

In this work, a new analytical procedure is developed to obtain the displacement field of a unidirectional composite plate subjected to bending in two planes. The analysed configuration consists of a plane plate supported at four points to which a point force is applied at the centre. The calculation procedure is based on the strain energy. The effects created by bending moments, torsional moments and shear forces in the plate have been considered. The results obtained analytically have been validated by comparing them with existing literature and with numerical simulations performed with the finite element software ABAQUS. High correlations have been obtained for the values corresponding to the vertical displacements in different alignments of points belonging to the plate, however, the same has not occurred with the distribution of moments.

Abstract

Existing experimental methods or traditional numerical methods struggled to separate the resistance caused by a vessel's movement and the impact of waves. However, the impact of waves significantly affected the stability and safety of Unmanned Underwater Vehicles (UUVs). To summarize the influence of different attitudes and sea conditions on ocean wave impact, this work first proposed a method to separate the influence of ocean waves. This method used the unsteady finite volume method to analyze the forces on the vehicle in both wave and calm water environments. It also employed a separation formula to isolate the wave impact based on a separation equation. Then, this work selected a specific UUV as the research subject and applied this method to separate the wave impact under various attitudes and sea conditions. The results were then reconstructed. Finally, the effects of various factors on wave impact were summarized, including wave height, wave period, pitch angle, heading angle, velocity, and diving depth.