The problem of the numerical modelling of the damping effect of the spiral compensators of percussion–rotary drilling devices is considered. The Roe first-order difference method has been adapted for the computation of a three-dimensional flow of a barotropic compressible fluid on a spatial curvilinear grid. As a result, the distributions of the solution components have been obtained both inside the compensator channel and at its upper outlet. A comparison of the damping effect of the compensator with the results of the one-dimensional computation by a TVD second-order scheme has shown that the three-dimensional computations produce a slightly more pronounced damping effect than the one-dimensional computations.