Vibrations due to mechanical excitation and internal and external fluid flow can cause fatigue in pipelines and leaks in fittings. A beam-based dynamic vibration absorber (beam DVA) is a device comprising an L-shaped beam with a concentrated mass at its free end that can be used to absorb and dissipate vibrations in the pipeline. In this paper, a mathematical equation is extracted to design the beam DVA using the dimensional analysis (DA) method and data recorded from 120 experimental tests. In the experimental studies, the pipes are fabricated in 1-inch, 2-inch, and 3-inch sizes. Each pipe is subjected to harmonic excitation at different frequencies, and the amplitude of vibration of the pipe is evaluated by changes in the geometric characteristics of beam DVA and concentrated mass. The proposed methodology is validated using the finite element method and simulation in the SIMULINK/MATLAB. The results showed that, out of the nine effective dimensionless parameters identified in pipe vibration control, mass ratio and stiffness ratio have the highest and lowest impacts on pipe vibration absorption, respectively.

Addition of mass, spring, and damper as a dynamic vibration absorber to a structure that is vibrating out of the permissible vibration range can be an economic and applicable solution to reduce structure vibrations provided that the absorber is designed and adjusted properly. In practice, real structures are damped, which can make it impossible to design vibration absorbers without using numerical solutions and complicated calculations. Using dimensional analysis technique and data obtained from system simulation by MATLAB Simulink, this study aims to provide simple and reliable correlations for designing and analyzing vibration absorbers. For this purpose, the motion equations of a one-degree-of-freedom system with a vibration absorber and a harmonic force applied is simulated. Use of a set of simulation output data to minimize the maximum motion amplitude of the structure along with multiple linear regression method enables determination of unknown coefficients of the correlations derived from dimensional analysis. Studies show that mass ratio and stiffness ratio are important for designing vibration absorbers for undamped and damped structures, respectively. The correlations are validated using the methods introduced in previous studies. Also, an example of vibration absorbers is calculated for an air compressor. The vibration absorber designed by this methodology results in a reduction in the magnification factor of the compressor by 78%.

This paper investigates the effect of impeller diameter on the dynamic response of a centrifugal pump using an inverse dynamic method. For this purpose, the equations of motion of the shaft and the impeller are derived based on Timoshenko beam theory considering the impeller as a concentrated mass disk. For practical modeling, the model of Jones and Harris is added to the equation to include the effect of bearings. As a case study, the model is applied to a process pump used in an oil refinery. Computing the eigenvalues of the model and comparing them with the natural frequencies of the structure, the model updating of the problem is performed through an indirect method. Three impellers with different diameters are applied to the updated model. The results show that increasing the diameter of the pump impeller can increase the amplitude of vibration up to 52% at critical speeds of the rotor. It is found that in addition to the hydraulic condition and efficiency, the impeller diameter should be considered as an important factor in the selection of centrifugal pumps.