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Lift Force (lift + force)
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] Fundamental characteristics and 3D electromagnetic analysis for magnetic levitation transporter using YBCO superconductorsELECTRICAL ENGINEERING IN JAPAN, Issue 2 2007Hiroshi Ueda Abstract A magnetic levitation device with two-dimensional movement, the so-called "levitating X-Y transporter," has been developed. In order to develop a working levitating X-Y transporter, it is necessary to clarify the levitation characteristics, such as the lift force, levitation height, and stability against mechanical disturbances. In this paper, we examine the lift and the restoring force experimentally and propose a new simulation program based on the three-dimensional hybrid finite and boundary element method to analyze the dynamic behavior of electromagnetic characteristics of YBCO bulk. Using the numerical simulation and experiments, we investigated a suitable arrangement of permanent magnets to enhance the levitation characteristics. We also designed a levitating transporter which can carry a load of 200 kg with a gap of 16 mm. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(2): 44,54, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20220 [source] Effect of blockage on free vibration of a circular cylinder at low ReINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10 2008T. K. Prasanth Abstract The effect of the blockage on vortex-induced vibrations of a circular cylinder of low non-dimensional mass (m*=10) in the laminar flow regime is investigated in detail. A stabilized space,time finite element formulation is utilized to solve the incompressible flow equations in primitive variables form in two dimensions. The transverse response of the cylinder is found to be hysteretic at both ends of synchronization/lock-in region for 5% blockage. However, for the 1% blockage hysteresis occurs only at the higher Re end of synchronization/lock-in region. Computations are carried out at other blockages to understand its effect on the hysteretic behavior. The hysteresis loop at the lower Re end of the synchronization decreases with decrease in blockage and is completely eliminated for blockage of 2.5% and less. On the other hand, hysteresis persists for all values of blockage at the higher Re end of synchronization/lock-in. Although the peak transverse oscillation amplitude is found to be same for all blockage (,0.6D), the peak value of the aerodynamic coefficients vary significantly with blockage. The r.m.s. values show lesser variation with blockage. The effect of streamwise extent of computational domain on hysteretic behavior is also studied. The phase between the lift force and transverse displacement shows a jump of almost 180° at, approximately, the middle of the synchronization region. This jump is not hysteretic and is independent of blockage. Copyright © 2008 John Wiley & Sons, Ltd. [source] Characterization of microseparator/classifier with a simple arc microchannelAICHE JOURNAL, Issue 1 2009Nobuo Oozeki Abstract Experimentally characterized is a novel microseparator/classifier, whose functional part is an arc microchannel with a width of 200 ,m, depth of 150 ,m, and radius of 20 mm. First, a unique separation principle due to shear-induced lift force is visually demonstrated with neutrally buoyant particles. The device performance is subsequently measured in terms of cut size, separation sharpness, and feed pressure for slightly denser acrylic particles. Compared with representative hydrocyclones, the present device is found to attain significantly smaller cut size at comparable feed pressure, and vice versa. It is finally shown that the device performance remains highest below a critical Stokes number because of no or negligible shear-induced interparticle collisions. It is concluded that the device is to operate with a high efficiency based on the proposed Stokes number. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] A CFD,PBM coupled model for gas,liquid flowsAICHE JOURNAL, Issue 1 2006Tiefeng Wang Abstract A computational fluid dynamics,population balance model (CFD-PBM) coupled model was developed that combines the advantages of CFD to calculate the entire flow field and of the PBM to calculate the local bubble size distribution. Bubble coalescence and breakup were taken into account to determine the evolution of the bubble size. Different bubble breakup and coalescence models were compared. An algorithm was proposed for computing the parameters based on the bubble size distribution, including the drag force, transverse lift force, wall lubrication force, turbulent dispersion force, and bubble-induced turbulence. With the bubble breakup and coalescence models and the interphase force formulations in this work, the CFD-PBM coupled model can give a unified description for both the homogeneous and the heterogeneous regimes. Good agreement was obtained with the experimental results for the gas holdup, liquid velocity, and bubble size distribution. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [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] Numerical simulations of viscous flows using a meshless methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 7 2008Changfu You Abstract This paper uses the element-free Galerkin (EFG) method to simulate 2D, viscous, incompressible flows. The control equations are discretized with the standard Galerkin method in space and a fractional step finite element scheme in time. Regular background cells are used for the quadrature. Several classical fluid mechanics problems were analyzed including flow in a pipe, flow past a step and flow in a driven cavity. The flow field computed with the EFG method compared well with those calculated using the finite element method (FEM) and finite difference method. The simulations show that although EFG is more expensive computationally than FEM, it is capable of dealing with cases where the nodes are poorly distributed or even overlap with each other; hence, it may be used to resolve remeshing problems in direct numerical simulations. Flows around a cylinder for different Reynolds numbers are also simulated to study the flow patterns for various conditions and the drag and lift forces exerted by the fluid on the cylinder. These forces are calculated by integrating the pressure and shear forces over the cylinder surface. The results show how the drag and lift forces oscillate for high Reynolds numbers. The calculated Strouhal number agrees well with previous results. Copyright © 2008 John Wiley & Sons, Ltd. [source] Continuous scalable blood filtration device using inertial microfluidicsBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2010Albert J. Mach Abstract Cell separation is broadly useful for applications in clinical diagnostics, biological research, and potentially regenerative medicine. Recent attention has been paid to label-free size-based techniques that may avoid the costs or clogging issues associated with centrifugation and mechanical filtration. We present for the first time a massively parallel microfluidic device that passively separates pathogenic bacteria cells from diluted blood with macroscale performance. The device was designed to process large sample volumes in a high-throughput, continuous manner using 40 single microchannels placed in a radial array with one inlet and two rings of outlets. Each single channel consists of a short focusing, gradual expansion and collection region and uses unique differential transit times due to size-dependent inertial lift forces as a method of cell separation. The gradual channel expansion region is shown to manipulate cell equilibrium positions close to the microchannel walls, critical for higher efficiency collection. We demonstrate >80% removal of pathogenic bacteria from blood after two passes of the single channel system. The massively parallel device can process 240,mL/h with a throughput of 400 million cells/min. We expect that this parallelizable, robust, and label-free approach would be useful for filtration of blood as well as for other cell separation and concentration applications from large volume samples. Biotechnol. Bioeng. 2010;107: 302,311. © 2010 Wiley Periodicals, Inc. [source] | |||||||||||||