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Single Bubble (single + bubble)
Selected AbstractsVOF-Simulation of the Lift Force for Single Bubbles in a Simple Shear FlowCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2006D. Bothe Abstract Bubbles in shear flows experience a lift force, causing them to migrate sideways while they are rising. This lateral migration is investigated in numerical simulations, which are carried out with an extended version of the highly parallelized code FS3D, employing an advanced Volume-of-Fluid method. The movement of single bubbles in linear shear flows is simulated to obtain the magnitude of the lift force , expressed by the lift force coefficient CL , for various bubble diameters and material data. Simulation results are in good agreement with experiments for medium liquid phase viscosities. An investigation of the dynamic pressure on the bubble surface explains why large bubbles migrate in the opposite direction compared to small bubbles. [source] Numerical simulation of a single bubble by compressible two-phase fluidsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2010Siegfried Müller Abstract The present work deals with the numerical investigation of a collapsing bubble in a liquid,gas fluid, which is modeled as a single compressible medium. The medium is characterized by the stiffened gas law using different material parameters for the two phases. For the discretization of the stiffened gas model, the approach of Saurel and Abgrall is employed where the flow equations, here the Euler equations, for the conserved quantities are approximated by a finite volume scheme, and an upwind discretization is used for the non-conservative transport equations of the pressure law coefficients. The original first-order discretization is extended to higher order applying second-order ENO reconstruction to the primitive variables. The derivation of the non-conservative upwind discretization for the phase indicator, here the gas fraction, is presented for arbitrary unstructured grids. The efficiency of the numerical scheme is significantly improved by employing local grid adaptation. For this purpose, multiscale-based grid adaptation is used in combination with a multilevel time stepping strategy to avoid small time steps for coarse cells. The resulting numerical scheme is then applied to the numerical investigation of the 2-D axisymmetric collapse of a gas bubble in a free flow field and near to a rigid wall. The numerical investigation predicts physical features such as bubble collapse, bubble splitting and the formation of a liquid jet that can be observed in experiments with laser-induced cavitation bubbles. Opposite to the experiments, the computations reveal insight to the state inside the bubble clearly indicating that these features are caused by the acceleration of the gas due to shock wave focusing and reflection as well as wave interaction processes. While incompressible models have been used to provide useful predictions on the change of the bubble shape of a collapsing bubble near a solid boundary, we wish to study the effects of shock wave emissions into the ambient liquid on the bubble collapse, a phenomenon that may not be captured using an incompressible fluid model. Copyright © 2009 John Wiley & Sons, Ltd. [source] Laser diagnostic investigation of the bubble eruption patterns in the freeboard of fluidized beds: Simultaneous acetone PLIF and stereoscopic PIV measurementsAICHE JOURNAL, Issue 6 2009C. R. Müller Abstract For the first time PIV has been applied simultaneously with acetone-PLIF in the freeboard of a fluidized bed. Here, the eruption profile of single bubbles and a continuous stream of bubbles were studied. As stereoscopic PIV was applied the out-of-plane component of the velocity was also measured. The out-of-plane component is not negligible. The observed bubble eruption patterns were in general agreement with the bubble model of Levy and Lockwood,24 Yorquez-Ramirez and Duursma5 and Solimene et al.1 No qualitative difference between the eruption of a single bubble and a stream of bubbles was observed. Based on the calculated vorticity of the gas in the freeboard, it was found that the bubble induced turbulence decays fairly rapidly. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Extension of PIV for measuring granular temperature field in dense fluidized bedsAICHE JOURNAL, Issue 1 2007W. Dijkhuizen Abstract In this work a particle image velocimetry (PIV) technique has been extended to enable the simultaneous measurement of the instantaneous velocity and granular temperature fields. The PIV algorithm has been specifically optimized for dense granular systems and has been thoroughly tested with artificially generated images. The new PIV technique has been successfully applied to a fluidized bed at incipient fluidization conditions in which a single bubble is injected by a jet and to a freely bubbling fluidized bed. The instantaneous spatial distribution of the solids-phase velocity and granular temperature that can be measured with this new technique can be used to validate CFD models for dense granular systems, such as multifluid continuum models using the KTGF (kinetic theory of granular flow) to describe the internal momentum transport in the particulate phase. © 2006 American Institute of Chemical Engineers AIChE J, 2007 [source] Laser diagnostic investigation of the bubble eruption patterns in the freeboard of fluidized beds: Simultaneous acetone PLIF and stereoscopic PIV measurementsAICHE JOURNAL, Issue 6 2009C. R. Müller Abstract For the first time PIV has been applied simultaneously with acetone-PLIF in the freeboard of a fluidized bed. Here, the eruption profile of single bubbles and a continuous stream of bubbles were studied. As stereoscopic PIV was applied the out-of-plane component of the velocity was also measured. The out-of-plane component is not negligible. The observed bubble eruption patterns were in general agreement with the bubble model of Levy and Lockwood,24 Yorquez-Ramirez and Duursma5 and Solimene et al.1 No qualitative difference between the eruption of a single bubble and a stream of bubbles was observed. Based on the calculated vorticity of the gas in the freeboard, it was found that the bubble induced turbulence decays fairly rapidly. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] VOF-Simulation of the Lift Force for Single Bubbles in a Simple Shear FlowCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2006D. Bothe Abstract Bubbles in shear flows experience a lift force, causing them to migrate sideways while they are rising. This lateral migration is investigated in numerical simulations, which are carried out with an extended version of the highly parallelized code FS3D, employing an advanced Volume-of-Fluid method. The movement of single bubbles in linear shear flows is simulated to obtain the magnitude of the lift force , expressed by the lift force coefficient CL , for various bubble diameters and material data. Simulation results are in good agreement with experiments for medium liquid phase viscosities. An investigation of the dynamic pressure on the bubble surface explains why large bubbles migrate in the opposite direction compared to small bubbles. [source] | ||||||||||