Abstract-The effect of cavitation on the lubrication performance of the journal bearing operating with non-Newtonian lubricant is studied. The non-Newtonian behaviour of lubricant is addressed based on power law fluid model. The hydrodynamic performance in terms of pressure distribution and load carrying capacity and how it depends on power law index are explored using CFD (computational fluid dynamic). The comparison between the case of "no-cavitation" and the "with cavitation" for the lubrication analysis is also performed. It is found that including the cavitation modelling in the analysis gives a more accurate prediction with respect to the load carrying capacity and vortex development. In addition, more significant error between the case of 'no cavitation' and the case of 'with cavitation' is found when n = 1 (i.e. Newtonian lubricant).Keyword-Cavitation; CFD (Computational Fluid Dynamic); lubrication; non Newtonian. I. INTRODUCTION Journal bearing is mechanical element designed to carry shaft or journal which rotates freely in a supporting metals or shell. The insertion of a lubricant into the region around the interacting devices could avoid direct contact between the surfaces, so the wear can be minimized. In addition, the pressure gradients that occur in the clearance between the journal and the bearing yield the load-carrying capacity. Due to the divergent-convergent gap, numerically the analysis of hydrodynamically lubricated journal bearings falls into several classes, using the Sommerfeld theory, using Half-Sommerfeld theory, using Reynolds approach, or using mass-conservative approach. The first three theories are often considered as a rough approximation, because it is not based on real physical phenomenon [1].There are few numerical works performed in literature to address the bearing lubricated by non-Newtonian either by taking into account the cavitation model or not. Mishra [2] proposed a numerical method by solving the Reynolds equation and energy equation to investigate the effect of journal misalignment, bore noncircularity, and lubricant non-Newtonian behaviour. In order to describe the lubricant characteristic in the cavitation region, Elrod method [3] was adopted. Yadav and Sharma [4] analysed the influence of the texturing parameter on the static and dynamic performance characteristic of the bearing. Lin et al.[5] studied the nonNewtonian effects on the non-linear stability boundary of short journal bearings through the transient non-linear analysis. Pratomo et al. [6] investigated the combined effect of single texturing (pocketing) and wall slip on pressure. The modified Reynolds equation for lubrication with non-Newtonian power-law fluid was proposed. It was shown that the maximum load support is achieved when the pocket depth is equal to the film thickness. However, in their study, the cavitation Reynolds boundary condition was applied. In the following work, Tauviqirrahman et al. [7] using a mass conserving numerical approach for modelling cavitation investigated hydrodynamic lubri...

ABSTRAKSaat ini, dalam dunia medis telah dikembangkan berbagai peralatan biomekanik yang dibuat untuk memperbaiki kualitas kesehatan manusia. Dalam peralatan tersebut, bearing merupakan salah satu elemen-elemen mesin yang memiliki fungsi vital. Hal ini dikarenakan bearing berfungsi membatasi gerak relatif antara dua atau lebih komponen mesin agar selalu bergerak pada arah yang diinginkan. Dengan menjaga fungsi pelumasan pada bearing, maka putaran bisa berlangsung secara halus dan aman, sehingga diharapkan pada akhirnya nanti peralatan kesehatan tersebut dapat mempunyai umur pakai yang lebih panjang. Penelitian-penelitian tentang pelumasan pada bearing saat ini banyak mengasumsikan pelumas bersifat Newtonian. Dalam kenyataannya, pelumas pada bearing di tingkat lapangan memiliki karakteristik non-Newtonian. Oleh karena itu, dalam penelitian kali ini, bearing dengan pelumas non Newtonian akan dianalisa lebih lanjut dengan menggunakan CFD (computational fluid dynamic). Permukaan kontak pada bearing akan dimodifikasi dengan tekstur dan slip untuk meningkatkan performansi pelumasan. Kedalaman tekstur divariasikan sebesar 0.1 dan 0.75 kali ketebalan film pelumas. Daya dukung beban dan gesekan menjadi dua parameter utama performansi pelumasan yang akan dianalisa. Dalam tulisan ini, perbandingan hasil antara analisa yang mempertimbangkan model kavitasi dengan yang tidak, menjadi pokok kajian. Hasil simulasi menunjukkan bahwa terdapat perbedaan hasil numerik antara yang mempertimbangkan kavitasi dan yang tidak sampai dengan 20 %. Selain itu, dengan memberikan slip pada tekstur dapat meningkatkan performansi daya dukung beban sebesar 300 % dengan menjaga gesekan tetap kecil. Hasil penelitian kali ini dapat dijadikan sebagai langkah awal untuk memperbaiki kualitas performansi textured bearing yang berpelumas non Newtonian.Kata kunci: CFD (computational fluid dynamic), kavitasi, non Newtonian, pelumasan, slip, tesktur