Articles with tag: "drag"

1. Estimating Icing Conditions with Highest Drag

   "These data will be useful in evaluating and formulating ice accretion analyses and also performance penalty predictions."

   from NASA-TM-83556.

   

   Summary

   In "Ice Shape Drag Correlations" a correlation of drag due to icing was detailed using data from NASA-TM-83556 ¹. Here, we use the correlation to predict or estimate which icing conditions can result in the highest drag.

   The icing conditions predicted to have the highest Cd values cluster in a limited range of Figures 1 and 2 of Appendix C ², even when wide ranges of airspeed and altitude are considered.

   The Appendix C, Figure 1 Icing Environment

   We will use the Appendix C Continuous Maximum Icing Conditions.

   Appendix C Figure 1 defines LWC as a function of water drop size MVD (noted as "Median Effective Drop Diameter").

   
   Public Domain image.

   There is a standard horizontal extent of 17.4 nmi. defined that will be used here.

   A true airspeed …

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2. Ice Shape Drag Correlations

   "No certain explanation for the poor repeatability of glaze ice shapes is available at this time."

   NASA-TM-83556.

   Public Domain image from AEDC-TR-87-23.

   Summary

   We have seen several attempts to correlate drag for an airfoil with icing conditions.
   Here, we will review prior correlations, and refine the methods to achieve a better, more widely applicable correlation.

   Prior Correlations

   One significant correlation is from NASA-TM-83556 ¹, that used test control parameters such as total temperature, LWC, and airspeed:

   
   Public Domain image from NASA-TM-83556.

   Another is from AEDC-TR-87-23 ², which used the calculated leading edge freezing fraction (N):

   
   Public Domain image from AEDC-TR-87-23.

   About the lines on Figure 3, AEDC-TR-87-23 states:

   The curves for these figures were drawn as the author interpreted the data.

   The curves are similar in shape because of the functional dependency of N on test conditions that affect the change in ice shape and, thus, Cd. Again, it depends …

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