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Unsteady flow over geometrical discontinuity: numerical simulation of a fluid-structure interation in a deformable tank
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Pressure oscillations in solid rocket motors: Numerical study
No full textA numerical study of pressure oscillation generated in Solid Rocket Motors (SRM) is presented. Attention is focused on the effect of the cavity located in the vicinity of the nozzle on the Flow-acoustic coupling and therefore on the consequent pressure oscillations. A parametric study with different cavity volumes has been conducted assuming the Flow to be axi-symmetric. Results show that the cavity volume plays an important role in the Flow-acoustic coupling mechanism. Indeed, the maximum pressure oscillation magnitude is observed to be highly dependent on the cavity volume and a close to linear dependence of the maximum excited mode against the volume of the cavity is documented. Satisfactory comparisons with experimental data available on the same geometrical configuration are also presented and discussed. (C) 2010 Elsevier Masson SAS. All rights reserved
Fluid-structure interaction: numerical simulation
No full textThe present article is a summary of the activities done by a research group of the University of Rome "La Sapienza'' on the subject of fluid-structure interaction (FSI). Implementation and numerical simulations have been conducted by means of a technique known in the literature as the partition treatment technique. A procedure to transfer the interaction effects between the individual components (fluid and structure) has been developed. As example of the methodology implemented, a numerical study of a hot flow through a pipe with a flexible structure inside, is presented. Results show that the heat flux distribution along the structure is highly influenced by the structure deformation
Ariane 5 P230 SRM frontal thermal protection evolution: numerical simulation
No full textIn the present work a numerical study of Ariane 5 P230 SRM frontal thermal protection (PTF) will be presented. The study is conducted by means of a methodology, called EFSI (erosive-fluid-structure-interaction). The first test and tuning of the whole methodology (EFSI) is performed on the present configuration of PTF S3 of ARIANE 5 booster in the frame of Arta ESA/CNES program. Comparison of numerical results with experimental data, deduced from bench firing tests and recovered flight motors, shows an impressive agreement both in terms of averaged values (percentage difference lower than 1%) and in terms of dispersions (percentage difference lower than 6%). Finally, the EFSI methodology has been applied for the design of a new concept of PTF, called PTF 3D. In this case the EFSI methodology allowed making a prevision of final geometrical configuration. Preliminary comparison of numerical prevision with experimental data shows an impressive agreement
P80 SRM Pressure Oscillations Reconstruction
No full textLarge solid rocket motors (SRMs) may exhibit pressure oscillations (PO) during their quasi-steady-state due to the coupling between chamber acoustic, usually the longitudinal modes, and other typical physical phenomena related to the combustion products flow, leading to a resonant condition. Although dissipative effects, occurring inside the motor chamber, prevent the reaching of high PO level, oscillating phenomena induce a dynamic environment on the launcher which could reduce payload comfort and safety. Both large segmented SRMs - e.g. Ariane 5 and Space Shuttle boosters - and monolithic finocyl SRMs - e.g. P80 of VEGA, exhibit pressure oscillations phenomena but in different functioning phases: the second half of the SRM operative life for segmented SRMs and the first half for aft-finocyl ones.
This study aims to discuss and analyze the signatures and the associated dispersion of PO phenomena in P80 SRM, exploiting data provided by the 11 flights (VV01-VV11) successfully accomplished by VEGA launcher. Pressure oscillations are characterized both in time and frequency domain. The experimental P80 SRM PO signature are then reconstructed by means of the Q1D model named AGAR, showing the capability of the model to represent with good correlation the whole PO scenario and to recover also the data dispersion
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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