In order to diminish the flow fluctuations of the rotary energy recovery device (RERD), the pre-pressurization and pre-depressurization grooves were introduced and typically slotted on the surface of the RERD's endcovers. Effects of the grooves on performance fluctuations of the RERD were researched by means of computational fluid dynamics (CFD) simulations and validating experiments. Simulative results indicated that when compared with the un-slotted RERD under flow rate of 12m(3)/h, rotary speed of 400 rpm, and operating pressure of 6.0 MPa, the flow fluctuation amplitudes of the slotted RERD were reduced about 75.3% for high pressure outlet and 77.2% for low pressure outlet respectively. Similarly, the pressure fluctuation amplitudes of the slotted RERD were dramatically reduced about 92.5% for high pressure outlet and 90.7% for low pressure outlet. In addition, the validating experiments were conducted under the same operating conditions. The results showed that flow fluctuation amplitudes of experiments were in good agreement with that of the simulations, and the difference between them were about 2.76-7.55%, verifying the simulation model was reasonable. Thus, it provides a feasible and effective way to use the pre-pressurization and pre-depressurization grooves to diminish the flow fluctuations of the RERD. (C) 2017 Elsevier B.V. All rights reserved.