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The pressure change in time in the hydraulic brake of the automatic cannon depends on many factors such as the geometry of the brake, the velocity of the piston, the amount of the hydraulic oil in the brake, elevation angle of the cannon, etc. The analysis was made at the extreme values of the temperature interval of the cannon usage as well as the normal temperature since the temperature affects the properties of the hydraulic oil. The numerical simulation of the flow field in the hydraulic brake during recoil was performed in CFD software ANSYS Fluent. The simulation was made in a 2D numerical domain based on the flow geometry in 3D space. Due to the flow field boundaries movement during the process, the dynamic mesh was employed. The dynamics of the hydraulic brake piston was determined using the solver in which the forces that act on the gun are defined by the User Defined Function file. The experiment was performed by firing from the 20mm M55 gun mounted on the stand. Experimental results contain pressure change in time inside the brake which was measured by the piezoelectric pressure sensor. The dynamic behavior of the cannon was recorded by the high-speed camera. The numerical results of the pressure change and position of the gun deviate within acceptable limits with respect to experimental results. Based on that, further analysis of the influence parameters on the hydraulic brake force can be done by numerical simulation.

Hydraulic brake is an important part of the artillery system because reliable amortization of energy of the recoil parts depends on its functioning. Therefore, it is important to estimate time-dependent pressure field inside the brake which depends on many factors, such as geometry of the brake parts, velocity of recoil parts and physical characteristics of the oil that is used in the brake. During recoil and counterrecoil process of the recoil parts of the artillery system, heating of the oil and the other parts of the hydraulic brake occurs. In this paper the influence of the temperature change of the hydraulic brake parts on the recoil force is analyzed. Since the hydraulic brake assembly is axisymmetric, the problem is considered to be two-dimensional. Differential equations that describe flow field in the brake are solved numerically using CFD software. A comprehensive comparison between numerical and experimental results has been performed and good agreement is observed.