Numerical and Experimental Investigations on Preload Effects in Air Foil Journal Bearings

A detailed elasto-gasdynamic model of a preloaded three-pad air foil journal bearing is presented. Bump and top foil deflections are herein calculated with a nonlinear beamshell theory according to Reissner. The 2D pressure distribution in each bearing pad is described by the Reynolds equation for compressible fluids. With this model, the influence of the assembly preload on the static bearing hysteresis as well as on the aerodynamic bearing performance is investigated. For the purpose of model validation, the predicted hysteresis curves are compared with measured curves. The numerically predicted and the measured hysteresis curves show a good agreement. The numerical predictions exhibit that the assembly preload increases the bearing stiffness (in particular for moderate shaft displacements) and the bearing damping.

Solar Wind-Comet Exosphere Interaction. 2. Could the Single-Fluid Gas-Dynamic Model be Applicable to the Rosetta Mission

Solar Wind-Comet Exosphere Interaction. 2. Could the Single-Fluid Gas-Dynamic Model be Applicable to the Rosetta Mission The capabilities of a single fluid gasdynamic model of solar wind-comet exosphere interaction, presented in the accompanying (Keremidarska et al.) [23], are discussed from the point of view of its potential implementation in interpreting data, expected to be obtained by ROSETTA mission instruments in plasma environments of the comet 67P/Churyumov-Gerasimenko. As an exapmle, some model's predictions of the structure and parameters' distribution in the inner coma of P/Halley are presented and compared with Giotto measurements. Special attention is paid to a possible non-traditional interpretation of the magnetic cavity boundasry, registered by Giotto magnetometer. Possible model's applications are discussed for each of the main expected stages in the evolution of the comet 76P/CG environments during ROSETTA rendezvous with the comet.