This thesis aims to investigate the interaction between the multibody dynamics and fluid dynamics of a pressure relief valve for hydraulic applications. The performance of a hydraulic valve is significantly influenced by flow forces generated due to changes in fluid momentum within the valve. These flow forces consist of three components: a steady-state factor, directly proportional to the flow rate and fluid velocity, and two unsteady factors, dependent on the flow rate derivative and spool acceleration, respectively. The first contribution, which is the most influential, consistently tends to decrease the flow area. It has been proven that, under a constant pressure drop across the valve, the steady-state force is directly proportional to the spool displacement, resembling the behavior of a virtual spring.