New models and numerical methods in hydrodynamic lubrication

Abstract

When the value of as is small enough (e.g., as : 7.85 x 10'6 N-s/m) the pressure profiles that develop in the journal bearing are observed to satisfy the condition p 2 pcav, with pcav computed from Eq. (4.11). In fact, a large region where p 2 pcav is observed, which resembles the cavitation regions predicted by more traditional models. This motivates to incorporate pGav = ~0.77 atm into the Elrod-Adams and Reynolds cavitation models in order to perform comparisons with the RRP model. Doing so, the resulting pressure profiles are shown in Fig. 6.1.15 for rotating speeds of 1000 and 5000 rpm and as : 7.85 x 10-5 and 7.85 x 10"6 N-s/m. Notice that the rupture point for both the Elrod-Adams and Reynolds models are the same (which is a well-known fact), while for the RRP coupling the rupture is placed further along the fluid's movement direction. On the other hand, it is also known that the Reynolds model fails to accurately predict the reformation point when compared to a mass-conserving model (AUSAS at (Ll., 2007). Remarkably, when as is small enough the RRP model predicts a reformation point similar to that of the Elrod-Adams model. Furthermore, Fig. 6.1.16 shows the comparison of the fluid fraction produced by the RRP model, 1 _ a, with the fluid fraction produced by the Elrod-Adams model, 0. Qualitatively both fluid fraction fields are similar, the one corresponding to the RRP model being a regularized version of the other, in some sense. Notice that increasing as to 7.85 x 10"5 N's/m significantly reduces the similarities between the two models.Let us remark that the results shown in these last comparisons were obtained with a mesh having A951 = 27rJr/512 and A332 : JW/64 (i.e., N9; : 512) and with the time step fixed to 400 steps per cycle (CFL:1.3). l'ribology International 130 (2629) T9] "205 contents listsfavafla'ble at Sciencet 're a.' iournat homepage: we, etsevlemomfiocate'J-'t riboiat,