Experimental and numerical study of super-critical flow around the rough sphere

Suzana Linić; Slavica Ristić; Zoran Stefanović; Mirko Kozić; Goran Ocokoljić

doi:10.5937/str1502011l

Critical microjets in collapsing cavities

Journal of Fluid Mechanics ◽

10.1017/s0022112095002461 ◽

1995 ◽

Vol 290 ◽

pp. 183-201 ◽

Cited By ~ 35

Author(s):

Michael S. Longuet-Higgins ◽

Hasan Oguz

Keyword(s):

Flow Field ◽

Spherical Harmonic ◽

Velocity Potential ◽

Initial Conditions ◽

Numerical Study ◽

Critical Flow ◽

Jet Formation ◽

Initial Flow ◽

The Family ◽

Self Similar

Inward microjets are commonly observed in collapsing cavities, but here we show that jets with exceptionally high velocities and accelerations occur in certain critical flows dividing jet formation from bubble pinch-off. An example of the phenomenon occurs in the family of flows which evolve from a certain class of initial conditions: the initial flow field is that due to a moving point sink within the cavity.A numerical study of the critical flow shows that in the neighbourhood of microjet formation the flow is self-similar. The local accelerations, velocities and distances scale as tβ-2, tβ-1 and tβ respectively, where β = 0.575. The velocity potential is approximately a spherical harmonic of degree ¼.

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Fluid dynamics around three cylinders in presence of small control cylinders

Canadian Journal of Physics ◽

10.1139/cjp-2019-0599 ◽

2020 ◽

Vol 98 (11) ◽

pp. 1060-1076

Author(s):

Ali Ahmed ◽

Shams-ul Islam ◽

Chao Ying Zhou ◽

Raheela Manzoor

Keyword(s):

Drag Coefficient ◽

Flow Regime ◽

Strouhal Number ◽

Numerical Study ◽

Critical Flow ◽

Square Cylinders ◽

Tandem Square Cylinders ◽

Critical Flow Regime ◽

Force Reduction ◽

Control Cylinder

A numerical study is performed to analyze the effect of small control cylinders on fluid force reduction and vortex shedding suppression on the flow past three inline square cylinders using the lattice Boltzmann method. The Reynolds number Re = 160 is fixed while the spacing between the cylinders is taken in the range of 1.0D ≤ g* ≤ 5.0D (where D is the size of the main cylinder) and the control cylinder size is varied from 0.1D to 0.5D. To systematically understand the effect of control cylinders on the forces, a detailed analysis of Strouhal number (St), mean drag coefficient (CDmean), and root mean square values of the drag and lift coefficients is presented in this paper. In this study, it is observed that the average mean drag coefficient (CDmeanaverage) and Strouhal number reached either maximum or minimum values at different values of separation ratio (g*) and small control cylinder size (d). It is found that at (g*, d) = (5.0, 0.0) and (1.0, 0.5), the average CDmean attains its maximum (CDmeanaverage = 0.7813) and minimum (CDmean = 0.0988) values. Furthermore, at (g*, d) = (5.0, 0.3) and (2.0, 0.0) the average St attains its maximum (St = 0.1780) and minimum (St = 0.041) values. It is found that the flow regimes completely change in the presence of control cylinders. In particular, at g* = 4.0 there is a critical flow regime when the size of the control cylinder changes from 0.1 to 0.5. The sudden jump in the mean drag coefficient and Strouhal number for the middle cylinder with their maximum and minimum values also confirms the critical flow regime. The effect of control cylinders within tandem square cylinders has not been studied before.

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A numerical study of the deformation and burst of a viscous drop in general shear flows

Journal of Fluid Mechanics ◽

10.1017/s002211208100116x ◽

1981 ◽

Vol 109 ◽

pp. 465-482 ◽

Cited By ~ 145

Author(s):

J. M. Rallison

Keyword(s):

Reynolds Number ◽

Numerical Scheme ◽

Numerical Study ◽

Time Dependent ◽

Critical Flow ◽

Two Dimensional ◽

Flow Rates ◽

Drop Shape ◽

Viscous Drop ◽

Orthogonal Rheometer

The time-dependent deformation and burst of a viscous drop in an arbitrary shear flow at zero Reynolds number is studied. The viscosities of the drop and the suspending fluid are assumed to be equal. A numerical scheme to track the (non-axisymmetric) drop shape in time is presented, and used to investigate the deformation induced by two-dimensional shear and orthogonal rheometer flows. Steady deformations, critical flow rates and burst modes are determined, and compared with asymptotic (small and large) deformation theories, and with experiment.

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Experimental and Numerical Study of Critical Flow Model Development for Supercritical CO2 Power Cycle Application

Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy ◽

10.1115/gt2018-75934 ◽

2018 ◽

Author(s):

Min Seok Kim ◽

Bong Seong Oh ◽

Hwa-Young Jung ◽

Seong Jun Bae ◽

Jeong Ik Lee

Keyword(s):

Supercritical Co2 ◽

Numerical Study ◽

Operating Conditions ◽

Working Fluid ◽

Critical Flow ◽

Phase System ◽

Phase Flow ◽

Two Phase ◽

Gaseous State ◽

Power Cycle

Supercritical CO2 (S-CO2) has the potential to be used as the working fluid in a power cycle since S-CO2 shows a density value high as its liquid phase while the viscosity value remains closer to its gaseous phase. Thus, it requires much less work to compress due to its low compressibility as well as relatively small flow resistance. However, the S-CO2 leakage flow from turbo-machinery via seal becomes one of the important issues since not only it influences the cycle efficiency due to parasitic loss but also it is important for evaluating the system safety under various operating conditions. In the previous turbo expo paper, the effect of the tooth length on the critical flow and comparing the results to the existing two phase system analysis code calculation were presented. In this paper, the gap effect, which is simulated by changing the diameter of a orifice and the number of tooth effect in a labyrinth seal geometry nozzle are presented by using the same experimental facility described in the previous paper. In addition, this paper includes the experimental results under various conditions including not only single phase flow such as supercritical, and gaseous state only but also two phase flow condition.

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