Friction-factors for honeycomb surfaces are measured with a flat plate tester. The flat plate test apparatus is described and a method is discussed for determining the friction-factor experimentally. The friction-factor model is developed for the flat plate test based on the Fanno Line Flow. The comparisons of the friction-factor are plotted for smooth surface and twelve-honeycomb surfaces with three-clearances, 6.9 bar to 17.9 bar range of inlet pressure, and 5,000 to 130,000 range of the Reynolds number. The optimum geometries for the maximum friction-factor are found as a function of cell width to cell depth and clearance to cell width ratios.

A new empirical friction-factor model for honeycomb surfaces based on flat plate test results has been developed as a function of Mach number and dimensionless pressure and honeycomb geometry variables. A rotordynamic analysis for centered, turbulent-annular-honeycomb-stator seals has been developed incorporating the new empirical friction-factor model for honeycomb-stator surfaces. The results of the new analysis in predicting the rotordynamic and leakage characteristics have been compared to: (a) Moody’s friction-factor model analysis, and (b) experimental data for short (L/D = 1/6, 25.4 mm long) seal. The comparisons show that the new honeycomb friction-factor model greatly improves the predictions of leakage and rotordynamic coefficients compared to Moody’s friction-factor model, especially, for direct and cross-coupled stiffness.

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The experimental determination of friction-factors for the flow of air in a narrow channel lined with various honeycomb geometries has been carried out. Test results show that, generally, the friction-factor is nearly constant or slightly decreases as the Reynolds number increases, a characteristic common to turbulent flow in pipes. However, in some test geometries this trend is remarkably different. The friction factor dramatically drops and then rises as the Reynolds number increases. This phenomenon can be characterized as a “friction-factor jump.” Further investigations of the acoustic spectrum and friction-factor measurements for a broad range of Reynolds numbers indicate that the “friction-factor jump” phenomenon is accompanied by an onset of a normal mode resonance excited coherent flow fluctuation structure, which occurs at Reynolds number of the order of 104. The purpose of this paper is not to present the friction-factor data but to explain the friction-factor-jump phenomenon and friction-factor characteristics.