Spelling suggestions: "subject:"[een] TAYLOR VORTEX"" "subject:"[enn] TAYLOR VORTEX""
1 |
Bubble Behavior in a Taylor VortexDeng, Rensheng, Wang, Chi-Hwa, Smith, Kenneth A. 01 1900 (has links)
We present an experimental study on the behavior of bubbles captured in a Taylor vortex. The gap between a rotating inner cylinder and a stationary outer cylinder is filled with a Newtonian mineral oil. Beyond a critical rotation speed (ω[subscript c]), Taylor vortices appear in this system. Small air bubbles are introduced into the gap through a needle connected to a syringe pump. These are then captured in the cores of the vortices (core bubble) and in the outflow regions along the inner cylinder (wall bubble). The flow field is measured with a two-dimensional particle imaging velocimetry (PIV) system. The motion of the bubbles is monitored by using a high speed video camera. It has been found that, if the core bubbles are all of the same size, a bubble ring forms at the center of the vortex such that bubbles are azimuthally uniformly distributed. There is a saturation number (N[subscript s]) of bubbles in the ring, such that the addition of one more bubble leads eventually to a coalescence and a subsequent complicated evolution. Ns increases with increasing rotation speed and decreasing bubble size. For bubbles of non-uniform size, small bubbles and large bubbles in nearly the same orbit can be observed to cross due to their different circulating speeds. The wall bubbles, however, do not become uniformly distributed, but instead form short bubble-chains which might eventually evolve into large bubbles. The motion of droplets and particles in a Taylor vortex was also investigated. As with bubbles, droplets and particles align into a ring structure at low rotation speeds, but the saturation number is much smaller. Moreover, at high rotation speeds, droplets and particles exhibit a characteristic periodic oscillation in the axial, radial and tangential directions due to their inertia. In addition, experiments with non-spherical particles show that they behave rather similarly. This study provides a better understanding of particulate behavior in vortex flow structures. / Singapore-MIT Alliance (SMA)
|
2 |
アスペクト比が小さい場合のテイラー渦流れ (時間発展力学系におけるモード形成と分岐)古川, 裕之, FURUKAWA, Hiroyuki, 渡辺, 崇, WATANABE, Takashi, 戸谷, 順信, TOYA, Yorinobu, 中村, 育雄, NAKAMURA, Ikuo 03 1900 (has links)
No description available.
|
3 |
アスペクト比が小さい場合のテイラー渦流れ (変異・正規モード間の流動形態変化と非定常モードの遷移過程)古川, 裕之, FURUKAWA, Hiroyuki, 渡辺, 崇, WATANABE, Takashi, 中村, 育雄, NAKAMURA, Ikuo 10 1900 (has links)
No description available.
|
4 |
[pt] ESCOAMENTO SECUNDÁRIO EM UM ANULAR PARCIALMENTE OBSTRUÍDO COM ROTAÇÃO DO CILINDRO INTERNO / [en] SECONDARY FLOW IN PARTIALLY-OBSTRUCTED ANNULAR SPACE WITH INNER CYLINDER ROTATION25 April 2005 (has links)
[pt] O escoamento em um espaço anular parcialmente obstruído é
estudado
para uma geometria entre cilindros concêntricos. A
obstrução parcial é uma
primeira aproximação de um escoamento em um espaço anular
com um leito de
cascalhos sedimentado que ocorre no processo de perfuração
de poços para
produção de óleo e gás, particularmente no caso de poços
inclinados e
horizontais. A presença de uma placa de obstrução parcial
promove a assimetria
no escoamento de tal modo que interfere na formação do
regime de vórtices de
Taylor. O campo de velocidade para esses escoamentos foi
obtido via solução
numérica e experimental. Nas simulações numéricas, as
equações de
conservação de massa e quantidade de movimento linear foram
resolvidas para
um escoamento de fluido newtoniano e não newtoniano pela
técnica de volumes
finitos. Os resultados experimentais foram obtidos a partir
de campos
instantâneos e médios de velocidade em planos meridionais
do espaço anular
usando a técnica de velocimetria por imagens de partículas
(PIV). As medições
focalizaram a obtenção do número de Reynolds rotacional
crítico e a obtenção
do perfil de velocidade axial passando pelo olho do
vórtice. Os resultados
mostram que o número de Reynolds crítico é diretamente
afetado pelo grau de
obstrução do espaço anular, assim como a largura dos
vórtices de Taylor. O
resultado dos perfis de velocidade axial calculados
concorda bem com os
resultados obtidos experimentalmente. A transição para o
regime de vórtices de
Taylor também é bem prevista pelo método numérico. Os
resultados numéricos
para a largura dos vórtices de Taylor não apresentam boa
concordância,
dependendo das condições de contorno estipuladas. A
presença da placa de
obstrução parcial promove uma recirculação circunferencial
no escoamento que
interage com o escoamento de vórtices de Taylor formando um
escoamento
complexo a partir de níveis de obstrução moderados. / [en] The flow inside a horizontal annulus due to the inner
cylinder rotation is
studied. The bottom of the annular space is partially
blocked by a plate parallel to
the axis of rotation, thereby destroying the
circumferential symmetry of the
annular space geometry. This flow configuration is found in
the drilling process of
horizontal petroleum wells, where a bed of cuttings is
deposited at the bottom
part of the annulus. The velocity field for this flow was
obtained both numerically
and experimentally. In the numerical work, the equations
which govern the threedimensional,
laminar flow of Newtonian and non-Newtonian liquids were
solved
via a finite-volume technique. In the experimental
research, the instantaneous
and time-averaged flow fields over two-dimensional
meridional sections of the
annular space were measured employing the particle image
velocimetry (PIV)
technique, both for Newtonian and power-law liquids.
Attention was focused on
the determination of the onset of secondary flow in the
form of distorted Taylor
vortices. The results showed that the critical rotational
Reynolds number is
directly influenced by the degree of obstruction of the
flow. The influence of the
obstruction is more perceptible in Newtonian than non-
Newtonian liquids. The
larger is the obstruction, the larger is the critical
Taylor number. The height of the
obstruction also controls the width of the vortices. The
calculated steady state
axial velocity profiles agreed well with the corresponding
measurements.
Transition values of the rotational Reynolds number are
also well predicted by the
computations. However, the measured and predicted values
for the vortex size
do not agree as well. Transverse flow maps revealed a
complex interaction
between the Taylor vortices and the zones of recirculating
flow, for moderate to
high degrees of flow obstruction.
|
Page generated in 0.0234 seconds