Prediction of liquid water content distribution in an altitude test cell using the FASER two-phase flow code

New aircraft/weapon systems are tested through a broad range of areas to insure safe and reliable use in actual flight operations. This testing traditionally is initiated in a ground test environment for safety and financial considerations. One area that must be examined prior to flight operations is the aircraft/weapon systems ability to perform its mission in icing conditions. The proper simulation of icing conditions in a test cell includes the requirement to have a uniform spatial distribution of Liquid Water Content (LWC).

The uniformity of the spatial LWC distribution is determined by the physical configuration of the test cell and the meteorological flight conditions being tested. A parametric study was performed to characterize the effects of changes to these parameters on spatial LWC for test cell J-1 in the Engine Test Facility. This characterization will be available to guide future efforts to improve the test cell design.

The two-dimensional two-phase flow code FASER was used to describe the effect of changes to test cell and meteorological parameters. This computer code provides qualitative plots to visually depict changes in spatial LWC uniformity. FASER was modified to include a calculation of the standard deviation and the mean of LWC. The standard deviation was used as a quantitative measure of the uniformity. A configuration from previous testing was used as a baseline condition. All changes made were compared to the baseline configuration.

The results obtained are the first step in a FASER code calibration. The results showed very little change for the meteorological parametric study. This indicates that similar uniformity is available throughout the range of icing conditions tested at the Arnold Engineering Development Center (AEDC). The test cell configuration parameters had a significant effect on uniformity. Careful test planning can take advantage of these results. The number of spray nozzles should be the highest possible to meet the total water flow required. The spray nozzles should be placed equidistant circumferentially but skewed outward radially. The area contraction ratio should be the highest possible. The bellmouth eccentricity should be as high as the area contraction ratio and bellmouth length will allow.

Future efforts must include acquisition of experimental data with known uncertainties to help in the code calibration. This data should be at the same conditions as performed in this parametric study. A subscale test program would provide the necessary data in a cost effective manner. The effect of varying more than one parameter at a time in the FASER program should be examined. Until the FASER code calibration is complete, the ability to accurately predict flight icing conditions in an altitude test cell will be limited.