Bulletin of the American Physical Society
67th Annual Meeting of the APS Division of Fluid Dynamics
Volume 59, Number 20
Sunday–Tuesday, November 23–25, 2014; San Francisco, California
Session M22: Instability: Multiphase Flow |
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Chair: Snezhana Abarzhi, Carnegie Mellon University Room: 2012 |
Tuesday, November 25, 2014 8:00AM - 8:13AM |
M22.00001: Stability of a hydrodynamic discontinuity Snezhana I. Abarzhi, Yasuhide Fukumoto, Leo P. Kadanoff While looking from a far field at a discontinuous front separating two incompressible ideal fluids of different densities, we identify two qualitatively different behaviors of the front (unstable and stable) depending upon whether the energy flux produced by the perturbed front is large or small compared to the flux of kinetic energy across the planar front. Landau's solution for the Landau-Darriues instability is consistent with one of these cases, whether the gravity is present or not. [Preview Abstract] |
Tuesday, November 25, 2014 8:13AM - 8:26AM |
M22.00002: Phase Change Effects on Immiscible Flow Displacements in Radial Injection Majid Ahmadlouydarab, Jalel Azaiez, Zhangxin Chen We report a systematic simulation of immiscible fluid-fluid displacements in radial injection in the presence of phase change. Due to the presence of two fluid-fluid interfaces in the system, a special treatment has been adopted. To track the leading interface position, two highly accurate methods including\textit{ Level Set} and \textit{Immersed Interface Method} were used, while for locating the trailing interface an energy equation was adopted assuming the existence of a constant thin condensate layer. Dimensional analysis led to three important dimensionless groups including capillary number (Ca), Jacob number (Ja) and viscosity ratios (M) of the three fluids. Simulation results indicate significant influences of these parameters on the development of the instability and the interfacial morphology of fingers. Increasing Ca or M tends to amplify the interfacial instability, fingertip splitting, and results in longer fingers. In contrast, increasing Ja has stabilizing effects due to an increase of the thickness of the condensate layer. On the other hand at lower viscosity ratios as well as lower Ca, because of compensation effects of the phase change, both leading and trailing interfaces are found to be less unstable. Moreover accumulated condensate and oil saturation depletion curves show increasing and decreasing trends, respectively, when the Ca increases. Although viscosity ratio and Ja have similar effects on the accumulated condensate, they do not show any effect on the oil depletion saturation. [Preview Abstract] |
Tuesday, November 25, 2014 8:26AM - 8:39AM |
M22.00003: Instability of a particle-laden jet in a confined environment Florent P.M. Sharpin, Julien R. Landel, C.P. Caulfield The dynamics of particle-laden jets is relevant to many geophysical events and industrial applications from volcanic eruptions to chemical reactors and oil refinement. We consider experimentally the dynamically rich behavior of a vertical momentum jet, constrained in a narrow gap whose length is two orders of magnitude smaller than the length-scales of the other two dimensions, and constrained to flow through, from below, a bed of small heavy particles. In the regime where the jet has eroded a large triangular region of the particle bed, a dense particle-laden jet develops, as the initially pure jet continually entrains, and carries to some height above the bed, a certain concentration of particles. This coupled particle-laden jet is unstable and oscillates from side to side in the confined environment. A large vortical structure forms as the particle-laden jet tilts sideways, at a well-defined frequency. Using an analogy with turbulent, single-phase fountains, we model the maximum height of rise of the particle-laden jet using a ratio between the single-phase jet source volume flux, and its coupled, particle-laden negative source buoyancy flux, which we determine using a novel non-intrusive technique. We also model the frequency of the particle-laden jet instability using the characteristic travel time of a particle in the jet, which also depends on the reduced gravity of the particle-laden jet. [Preview Abstract] |
Tuesday, November 25, 2014 8:39AM - 8:52AM |
M22.00004: Spatio-temporal evolution of interfacial instabilities in vertical gas-liquid flows Patrick Schmidt, Prashant Valluri, Lennon \'{O} N\'{a}raigh, Mathieu Lucquiaud Vertical gas-liquid flows are characteristic for process engineering and widely employed in various technical applications. However, the dynamic behaviour of the liquid interface in such flows is still not fully understood. We focus in our work on characterising the interfacial instability as well as associated interfacial waves in vertical laminar-laminar gas-liquid flows over a wide range of parameters covering different flow regimes, i.e. counter-current, zero-interface velocity (loading) and partial-to-full liquid flow reversal (flooding). High-resolution direct numerical simulations using the TPLS flow solver (http://sourceforge.net/projects/tpls/) reveal the existence of weakly nonlinear interfacial waves, which are in good agreement with Stuart-Landau theory. These waves travel down- or upstream, depending on the flow regime. Furthermore, spatio-temporal linear stability analysis indicates the occurrence of absolute instability within the investigated parameter range. DNS is used to analyse this feature in more detail whereby agreement with linear theory has been established. [Preview Abstract] |
Tuesday, November 25, 2014 8:52AM - 9:05AM |
M22.00005: Control strategy for a double-diffusive two-fluid channel flow: A stability analysis Sukhendu Ghosh, R. Usha, Kirti Sahu The effect of velocity slip (symmetric and asymmetric) at the walls on the linear stability characteristics of miscible two-fluid channel flow is considered in the presence of double diffusive (DD) phenomenon. The channel walls are made of same material or different materials; this suggests symmetric or asymmetric slip condition at the walls. The fluids are miscible, and consist of two solute species having different rate of diffusion. Both the fluids are assumed to be of the same density, but varying viscosity, which depends on the concentration of the solute species. This flow system is more unstable than the corresponding single component (SC) flow as well as unstratified flow, due to the presence of double-diffusive (DD) effect. When the mixed region of the fluids moves towards the channel walls a new unstable mode (namely the DD mode) arises at low Reynolds numbers. The slip parameter has nonmonotonic effect on the stability characteristics in this system. The trend of slip effect is influenced by other flow parameters. The effects of wall slip on the flow stability is weak or strong depending on the slip condition, only for the upper wall or only for the lower layer or for both the walls. Increasing the value of the slip parameter delays the first occurrence of the DD-mode. [Preview Abstract] |
Tuesday, November 25, 2014 9:05AM - 9:18AM |
M22.00006: The Effect of Varying Stokes Number on the Growth Rate of Instabilities in Particle-Laden Shear Layers Sean Davis, Giacomo Senatore, Gustaaf Jacobs The growth rates of instabilities in the shear layer of a stratified particle-laden flow are analyzed using both a Linear Stability Analysis (LSA) of a stochastic Eulerian-Eulerian (EE) model and a high-order Eulerian-Lagrangian (EL) computation. In the LSA, a modified Rayleigh equation is derived, which governs the linear growth rate of a spatially periodic disturbance while the EL method solves the inviscid Euler equations using a particle source in cell method. A study of the particle response time shows that small-inertia particles (St \textless\ 0.2) may destabilize the inviscid mixing layer development as compared to a pure-gas flow. Energy is transferred globally from the particle phase to the fluid phase triggering this destabilization. The maximum stabilizing effect occurs at intermediate St (1 \textless\ St \textless\ 10), while multiple unstable modes coexist at larger St. These small, medium and large St effects are validated with numerical experiments using the EL code, showing very good agreement with the growth rates computed using the LSA. [Preview Abstract] |
Tuesday, November 25, 2014 9:18AM - 9:31AM |
M22.00007: Turbulent transition modification in dispersed two-phase pipe flow Kyle Winters, Ellen Longmire In a pipe flow, transition to turbulence occurs at some critical Reynolds number, $Re_c$, and transition is associated with intermittent swirling structures extending over the pipe cross section. Depending on the magnitude of $Re_c$, these structures are known either as puffs or slugs. When a dispersed second liquid phase is added to a liquid pipe flow, $Re_c$ can be modified. To explore the mechanism for this modification, an experiment was designed to track and measure these transitional structures. The facility is a pump-driven circuit with a 9m development and test section of diameter 44mm. Static mixers are placed upstream to generate an even dispersion of silicone oil in a water-glycerine flow. Pressure signals were used to identify transitional structures and trigger a high repetition rate stereo-PIV system downstream. Stereo-PIV measurements were obtained in planes normal to the flow, and Taylor's Hypothesis was employed to infer details of the volumetric flow structure. The presentation will describe the sensing and imaging methods along with preliminary results for the single and two-phase flows. [Preview Abstract] |
Tuesday, November 25, 2014 9:31AM - 9:44AM |
M22.00008: Studies of Interfacial Perturbations in Two Phase Oil-Water Pipe Flows Induced by a Transverse Cylinder Maxime Chinaud, Kyeong Park, James Percival, Omar Matar, Christopher Pain, Panagiota Angeli Droplet detachment from interfacial waves has been the subject of many studies. To observe this phenomenon experimentally it is necessary to spatially localize the drop formation and enable quantitative measurements. In this study, a novel approach is followed where a transverse cylinder is introduced close to the mixing point of the two phases in oil-water flows which induces waves. The introduction of the cylinder induces interfacial waves that lead to drop detachment. High speed visualization has been used to generate flow pattern maps with this new system. The dispersed patterns induced by the cylinder will be linked to pressure drop measurements. The interface downstream the cylinder is affected by three different contributions: the vortices shed by the cylinder, the wall effects due to the pipe itself and the interface fluctuations due to the mixing of the two phases. These contributions will be quantified through a numerical study. A mesh adaptive multiphase finite element Navier Stokes solver, Fluidity, will be used to obtain flow pattern maps for 2D channel flow. The numerical findings will be compared against the experimental results. [Preview Abstract] |
Tuesday, November 25, 2014 9:44AM - 9:57AM |
M22.00009: Numerical study of interface stability in presence of surfactant in two phase couette flow using a multiphase lattice boltzmann method V.P.T.N.C.Srikanth Bojja The multiphase lattice Boltzmann approach is used to study the dynamics of interface between two immiscible fluids of different densities and viscosities in presence of a insoluble surfactant in Coutte flow. The simulations are performed on muti-cpu cluster using MPI. The effects of inertia (Reynolds number) and surfactant (Marangoni number) on the stability of the interface at arbitary wave numbers are investigated. Neutral-stability and growth-rate curves are plotted at different wave-numbers, Reynolds numbers and Marangoni numbers. Interesting phenomenon of surfactant accumulation on the crest of interfacial waves is observed and subsequent breakdown of the interfacial wave, droplet formation,entrainment are also observed in 3D simulations. [Preview Abstract] |
Tuesday, November 25, 2014 9:57AM - 10:10AM |
M22.00010: Thermal dispersion effects on the two-phase zone with evaporation in a porous medium Manuel Peralta Guti\'errez, Oscar Bautista The one-dimensional steady-state heat transfer in a two-phase zone of a water-saturated porous medium is studied numerically by including thermal dispersion effects. The physical system consists of a porous medium-liquid-vapor mixture that is heated from above and maintaining a fixed temperature on the bottom surface. Under certain conditions, a two-phase zone of both vapor and liquid exists in the middle of the region of the porous medium. A mathematical model for the temperature and the liquid saturation profiles within this two-phase zone is formulated by allowing for explicit temperature dependence for the saturation vapor pressure together with explicit saturation dependence for the capillary pressure. The set of resultant equations is numerically integrated by using a conventional fourth order Runge-Kutta scheme. The results evidence the strong influence of the thermal dispersion, porosity and pore diameter on the two-phase zone. $R_{1} R_{3}$ [Preview Abstract] |
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