*Article* **Drag Reduction Analysis of the Hydrostatic Bearing with Surface Micro Textures**

**Youyun Shang 1,\* ,† , Kai Cheng 2,†, Qingshun Bai <sup>1</sup> and Shijin Chen <sup>1</sup>**


**Abstract:** Surface microtexturing has been widely used due to its good hydrophobic or drag reduction characteristics, and become an effective method to improve product performance and reduce energy consumption. This paper mainly discusses the improvement of microtextures on the dynamic pressure characteristics of hydrostatic bearings, and explores the effects of texture parameters on carrying capacity, macroscopic wall two-plane shear force, cavity area and other factors. In the oil film model calculation of the smooth wall surface of the radial hydrostatic bearing under the action of high speed and large external load, the oil film divergent wedge often has a negative pressure area, which is obviously not in line with the actual situation, so the cavitation effect needs to be considered. The CFD analysis method of the "gas-oil" two-phase flow model was carried out by using the mixture model to seek the optimal texture model scheme and thus to improve the load carrying capacity (LCC) and reduce the wall shear force. The effects of the texture area arrangement and geometric parameters on the lubrication characteristics were compared and analyzed. It is found that the carrying capacity of local texture is better than that of global texture, and different texture arrangements can achieve better drag reduction rates. The work presented in this paper studies the lubrication of the surface texture of a hydrostatic bearing. Taking the oil film carrying capacity and shear force as the target parameters, the factors, such as texture morphology, geometric parameters, texture distribution and cavitation phenomenon, are investigated through simulation and experimental methods. The surface textured hydrostatic bearing is expected to obtain the maximum oil film carrying capacity and the minimum friction resistance. The analysis results show that by arranging the partial streamwise texture at the rear end of the diverging wedge, the maximum shear force of the wall can be reduced by about 15%, and the LCC can be increased by about 18%.

**Keywords:** CFD method; cavitation effects; drag reduction; microtexture; hydrostatic bearing
