Abstract: Periodic vortex shedding in pulsating flow inside wavy
channel and the effect it has on heat transfer are studied using the
finite volume method. A sinusoidally-varying component is superimposed
on a uniform flow inside a sinusoidal wavy channel and
the effects on the Nusselt number is analyzed. It was found that a
unique optimum value of the pulsation frequency, represented by the
Strouhal number, exists for Reynolds numbers ranging from 125 to
1000. Results suggest that the gain in heat transfer is related to the
process of vortex formation, movement about the troughs of the wavy
channel, and subsequent ejection/destruction through the converging
section. Heat transfer is the highest when the frequencies of the
pulsation and vortex formation approach being in-phase. Analysis of
Strouhal number effect on Nu over a period of pulsation substantiates
the proposed physical mechanism for enhancement. The effect of
changing the amplitude of pulsation is also presented over a period
of pulsation, showing a monotonic increase in heat transfer with
increasing amplitude. The 60% increase in Nusselt number suggests
that sinusoidal fluid pulsation can an effective method for enhancing
heat transfer in laminar, wavy-channel flows.
Abstract: Stuck-pipe in drilling operations is one of the most
pressing and expensive problems in the oil industry. This paper
describes a computational simulation and an experimental study of
the hydrodynamic vibrator, which may be used for liquidation of
stuck-pipe problems during well drilling. The work principle of the
vibrator is based upon the known phenomena of Vortex Street of
Karman and the resulting generation of vibrations. We will discuss
the computational simulation and experimental investigations of
vibrations in this device. The frequency of the vibration parameters
has been measured as a function of the wide range Reynolds Number.
The validity of the computational simulation and of the assumptions
on which it is based has been proved experimentally. The
computational simulation of the vibrator work and its effectiveness
was carried out using FLUENT software. The research showed high
degree of congruence with the results of the laboratory tests and
allowed to determine the effect of the granular material features upon
the pipe vibration in the well. This study demonstrates the potential
of using the hydrodynamic vibrator in a well drilling system.