TY - JOUR
T1 - Non-modal stability analysis of stratified two-phase channel flows
AU - Barmak, I.
AU - Gelfgat, A. Yu
AU - Ullmann, A.
AU - Brauner, N.
N1 - Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2019/2
Y1 - 2019/2
N2 - The non-modal transient growth of perturbations in horizontal and inclined channel flows of two immiscible fluids is studied. 3D perturbations are examined in order to find the optimal perturbations that attain the maximum amplification of perturbation energy at relatively short times. Definition of the energy norm is extended to account for the gravitational potential energy along with the kinetic energy and the interfacial capillary energy. Contrarily to the fastest exponential growth, which is reached by essentially 2D perturbations, the maximal non-modal energy growth is attained mostly by three-dimensional spanwise perturbations. Significant transient energy growth is found to occur in linearly stable flow configurations, which, similarly to single phase shear flows, may trigger non-linear destabilizing mechanisms within one of the phases. It is shown that the transient energy growth in linearly stable cases can be accompanied by noticeable interface deformations. Therefore, flow pattern transition due to non-modal transient growth and reduction of the range of operational conditions for which stratified-smooth flow remains stable cannot be ruled out.
AB - The non-modal transient growth of perturbations in horizontal and inclined channel flows of two immiscible fluids is studied. 3D perturbations are examined in order to find the optimal perturbations that attain the maximum amplification of perturbation energy at relatively short times. Definition of the energy norm is extended to account for the gravitational potential energy along with the kinetic energy and the interfacial capillary energy. Contrarily to the fastest exponential growth, which is reached by essentially 2D perturbations, the maximal non-modal energy growth is attained mostly by three-dimensional spanwise perturbations. Significant transient energy growth is found to occur in linearly stable flow configurations, which, similarly to single phase shear flows, may trigger non-linear destabilizing mechanisms within one of the phases. It is shown that the transient energy growth in linearly stable cases can be accompanied by noticeable interface deformations. Therefore, flow pattern transition due to non-modal transient growth and reduction of the range of operational conditions for which stratified-smooth flow remains stable cannot be ruled out.
KW - Gravity effect
KW - Non-modal stability
KW - Optimal perturbations
KW - Transient energy growth
KW - Two-phase stratified flow
UR - http://www.scopus.com/inward/record.url?scp=85057456949&partnerID=8YFLogxK
U2 - 10.1016/j.ijmultiphaseflow.2018.10.020
DO - 10.1016/j.ijmultiphaseflow.2018.10.020
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AN - SCOPUS:85057456949
SN - 0301-9322
VL - 111
SP - 122
EP - 139
JO - International Journal of Multiphase Flow
JF - International Journal of Multiphase Flow
ER -