Abstract
Bulk flow theory has been widely used to estimate annular seals dynamic coefficients. To predict the flow behavior through the seal, this theory relies on empirical friction factor correlations based on pipe data. Several experiments have gathered seals performance and leakage information indicating that friction factor increases as the seal clearance is increased, contradicting the theory predictions based on Moody's pipe-friction model. A Computational Fluid Dynamics (CFD) code is used to simulate the fluid motion over surfaces with particular roughness patterns. Flat plate experimental tests showing such friction factor vs. clearance behavior were numerically modeled. It was consistently found that the higher friction factor characteristics of these deliberately roughened surfaces are governed by the roughness ability to develop a high static pressure in the trailing face of each roughness cavity. Wall shear stresses play a secondary role.
Villasmil Urdaneta, Larry Alfonso (2002). Understanding the friction factor behavior in liquid annular seals with deliberately roughened surfaces, a CFD approach. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2002 -THESIS -V49.