THE INFLUENCE OF SOME FLUID-DYNAMIC MODELS ON ROOF LOADINGS FOR THE COVA EXPERIMENTS
This paper deals with the roof loading overpredictions, the problem of the strain underpredictions being treated in a complementary paper. It has to be noted that the measured pressure records on the roof for long and short tanks are generally quite different in character. Long tank records tend to be smooth and it is thought that, due to the cover gas, little or no contact of the fluid with the roof occurs, this observation is confirmed by the computed results. In contrast, the short tank records change rapidly and the fluid contact with the roof takes place except for the extreme outer region of the roof. In order to reduce the complexity of the reasons for the overpredicted roof loadings, results from calculations of simple COVA tests such as IT6, a thick overstrong bare cylindrical vessel, are mainly considered in this paper. Use is made of SEURBNUK and other ancillary codes to investigate different aspects of the problem. Taking note that the impulses on the base and walls are well predicted and that results obtained by different codes are in close agreement, the number of possible reasons for the roof impulse overpredictions is reduced. Particular attention is focused on the following aspects which could account for some of the inadequacies observed: - oversimplified cover gas treatment which neglects the wave propagation phenomena within the gas; - oversimplified assumption that the roof is perfectly rigid; - unrealistic behaviour of the LDE charge equation of state when the expansion ratios are outside the range foreseen by the charge calibration experiments. According to the results of this analysis possible improvements in the modelling are discussed.
Bibliographic Reference: SMIRT-CONFERENCE, CHICAGO (USA), AUG. 22-26, 1983 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 30993 ORA
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Record Number: 1989122040100 / Last updated on: 1987-01-01
Available languages: en