EXECUTIVE SUMMARY PURPOSE AND SCOPEThe objectives of this research program were to investigate the variability of the ASTM E 648 Standard with respect to carpets and to make recommendations for revising the standard to improve the repeatability and reproducibility of the measured results. The need for such a study arose from NVLAP's concerns about the high coefficients of variation resulting from proficiency rounds carried out as part of the Carpet LAP.One carpet was studied to investigate the ignitability and flame propagation problem experienced by CRI in the summer of 1987.Several ignition sources and procedural variations were investigated to assure that flame propagation would occur; the most significant finding was that a propane line burner gave a more uniform burn pattern than the propane torch point source pilot burner and seemed to insure propagation away from the ignition area provided the critical radiant flux was less from the maximum flux from the panel.Eight carpets of varying fibers and constructions were examined using the standard procedure to determine which would result in the lowest coefficient of variation.One was chosen for a parametric study of the test variables. Based on the findings of this study, a "proficiency round" was carried out using this carpet and recommendations were made to ASTM Committee E05 on Fire Standards for revision of ASTM E 648. CONCLUSIONS AND RECOMMENDATIONSThe following conclusions resulted from this study:• Replacement of the point ignition source by a line burner improves the likelihood of flame propagation and provides more even burn patterns.• The rate of air flow through the apparatus has a significant effect on test results.• Contrary to previous experience with NVLAP proficiency rounds, good reproducibility can be achieved by paying closer attention to prescribed procedures.• Conditioning time up to at least 12 days appears to increase critical radiant flux values .• Imposing a time limit on the test is not a viable means for determining critical radiant flux of a carpet. iii • Use of 100 lb, or smaller, bottles of commercial propane can influence operating conditions during the course of the day if proper attention is not paid to making adjustments in the gas flow rate to maintain the panel operating temperature and flux profile.• The radiant panel requires 1 1/2 hours to approach equilibrium when propane is used for the fuel; equilibrium was achieved in only 1 hour with natural gas.Specific recommendations for further work which need to be addressed are as follows ;• Carry out a round robin with a wide selection of carpets, including as many laboratories as are willing to participate.• All future NVLAP proficiency rounds should be performed using the same adhesive supplied from a single source.• Determine the effect of specimen location on the carpet to assess variation in the product and determine the effect of carpet aging on critical radiant flux.Additional consideration should be given to the following in order to further the development of the Floor...
We consider the linear stability of a modulated Taylor-Couette system when the inner cylindrical boundary consists of a crystalline solid-liquid interface. Both experimentally and in numerical calculations it is found that the two-phase system is significantly less stable than the analogous rigid-walled system for materials with moderately large Prandtl numbers. A numerical treatment based on Floquet theory is described, which gives results that are in good agreement with preliminary experimental findings. In addition, this instability is further examined by carrying out a formal asymptotic expansion of the solution in the limit of large Prandtl number. In this limit the Floquet analysis is considerably simplified, and the linear stability of the modulated system can be determined to leading order through a conventional stability analysis, without recourse to Floquet theory. The resulting simplified problem is then studied for both the narrow gap geometry and for the case of a finite gap. It is surprising that the determination of the linear stability of the two-phase system is considerably simpler than that of the rigid-walled system, despite the complications introduced by the presence of the crystal-melt interface.
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