Introduction
Oil will inevitably pulsate during circulating processes of employed oil
equipment due to the functional action of the equipment, and this effect
will affect the action accuracy of the equipment. A variety of measures
are often employed in industry to reduce the effects of such pulsations.
However, the pulsation of oil is not only related to the mechanical
function but also the characteristics of the oil itself, and the
particle size and concentration of particles in oil also play
significant roles in the pulsation of oil. The effect of particle size
and concentration on the pulsation characteristics of oil belongs to a
sparse solid-liquid two-phase flow field, on which domestic and foreign
scholars have carried out theoretical simulation and experimental
research and obtained many research results(Abiev and Galushko, 2013;
Eschmann et al., 2015; Wang et al., 2016; Yuan et al., 2016). These
results have a certain reference value to investigate the influence of
particle size and concentration in oil with higher viscosity on the
pulsation characteristics of the oil.
Papadopoulos et al.(2016) conducted a
direct numerical simulation of sinusoidal pulsation turbulence in a
straight tube with a low-volume Reynolds number and a high-frequency,
indicating the evolution of the average velocity and fluid pulsation
over time. Tian et al.(2016) obtained the variation trend of vibration
displacement and velocity of a pipeline system by establishing an
analysis method of pressure pulsation in the channel and the coupling
interaction of tube flow. Yan et al.(2012) studied the interaction
between quasiperiodic large-scale vortex structures and flow pulsation
in a rectangular channel, and the conclusions indicated that the
pulsation of the vortex structure and the flow velocity pulsation could
be enhanced by an adjacent velocity interface. Zhao Hui et al.(2016)
studied the unsteady flow field in a channel using direct numerical
simulation and found that the contributions of the low-frequency
vortices to the flow direction and normal pulsation velocity increase
with increasing normal height; the pulsation of the spanwise velocity at
the near-wall surface exhibited a large pulsation strength in the
logarithmic layer and the viscous bottom layer. Ghadi et al.(2016)
conducted jet oscillating flow experiments and showed that pulsating
flow forms a coherent periodic structure and that the pulsation
frequency has a significant influence on the formation, size, and
dynamics of a vortex structure. Hsu et al.(2014) measured a jet field
using high-speed particle image velocimetry (PIV) and found that with
the change in the jet exit velocity, the jet produced vibration within a
pulsating period and induced a periodic wavy flow structure in the
downstream region. Yang bin et al.(2013) believed that the change in
frequency of wind-sand flow was at least greater than 100 Hz, and the
effect of atmospheric turbulent pulsation on sediment concentration was
related to the sand grain size; the smaller the particle size was, the
greater the effect of wind speed fluctuation.
Two-phase flow in pipelines has been
studied for the generation and development of flow field pulsation and
the interaction of vortex structures in flow fields at home and abroad.
Due to the random nature of oil movement and the complexity of its
interaction with particles, the understanding of the pulsation
characteristics of oil with different particle sizes and concentrations
remains in the qualitative or semiquantitative stage. There is little
literature that analyzes the pulsation characteristics of oil with
higher viscous fluids. Therefore, it is necessary to investigate the
pulsation characteristics of oil in the flow direction and for the
normal pulsation strength as well as the instantaneous velocity and the
average velocity based on the vector field data measured by the PIV of
the oil containing particles in pipelines. Additionally, understanding
the pulsation movement of oil at different concentrations and particle
sizes reveals the interaction between particles and oil and lays a
foundation for understanding the physical essence of the formation and
development of oil pollution.