In order to model the effect of the cutting fluid on wet grinding processes, a model is built to investigate the hydrodynamic properties. This model can be divided into two parts. First, a macroscopic description of a grinding wheel is developed to model pressure build-up, cavitation and thermal effects driven by viscous shear. The numerical analysis at this scale is carried out using isogeometric analysis (IGA) based on NURBS and the Reynolds equation, while the cavitation effects are described using a mortar-based approach. With respect to the complex interactions of temperature and pressure dependencies of fluid properties, the comparatively small size of the discretised system matrices of the IGA approach allows a fully coupled description of fluid pressure and temperature in a monolithic approach, taking into account the necessary stabilisation mechanisms for NURBS-based descriptions. At the microscopic level, the actual engagement of the abrasive grains with the workpiece plays an important role. In addition to surface roughness, contact areas block the flow of fluid, increasing the need to consider the influence of the microscale on the global pressure build-up and coefficient of friction. By using exemplary grinding wheel sections to calculate flow parameters, the macroscopic pressure calculation can also be used to account for the actual grinding wheel topography and grain engagement.