Recirculating Flow (recirculating + flow)

Distribution by Scientific Domains


Selected Abstracts


3D tangentially injected swirling recirculating flow in a nozzle with a slotted-tube,Effects of groove parameters

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2010
Hui-Fen Guo
Abstract A numerical prediction for 3D swirling recirculating flow in an air-jet spinning nozzle with a slotted-tube is carried out with the realizable k,, turbulence model. The effects of the groove parameters on the flow and yarn properties are investigated. The simulation results show that some factors, such as reverse flow upstream of the injector, vortex breakdown downstream of the injector, corner recirculation zone (CRZ) behind the step and vortex ring in the groove caused by the groove geometric variation, are significantly related to fluid flow, and consequently to yarn properties. With increasing groove height, the length of the CRZ increases, while the initial vortex ring in the groove decreases and a same direction rotating vortex forms in the bottom of the groove. Similarly, as the groove width increases, the extent of both vortex breakdown in downstream of the injectors and the vortex ring in the groove increases slightly, whereas the CRZ lengths in stream-wise direction decrease. Some factors, such as the negative tangential velocities, the size of the vortex rings in the grooves and the CRZ, are constant for nozzles with different groove lengths. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Large eddy simulation of turbulent flows by a least-squares finite element method

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2001
Xu Ding
Abstract The least-squares finite element method (LSFEM) based on first-order formulations of governing equations has been used successfully for incompressible and compressible flows and transport processes. It has not been applied to turbulent flows. In this work, large eddy simulation (LES) with dynamic subgrid-scale models is used to simulate turbulent flows. The LSFEM is implemented to solve the filtered LES equations for turbulent flows and transport processes. Numerical experiments have been carried out for three types of turbulent flows, turbulent channel flow, transitional recirculating flow, and thermal convective turbulent flow. Numerical results are compared with experimental data or direct numerical simulation results. Copyright © 2001 John Wiley & Sons, Ltd. [source]


The Influence of Operational Protocol on the Fluid Dynamics in the 12 cc Penn State Pulsatile Pediatric Ventricular Assist Device: The Effect of End-Diastolic Delay

ARTIFICIAL ORGANS, Issue 4 2010
Benjamin T. Cooper
Abstract The success of adult ventricular assist devices (VADs), coupled with the high transplant waiting list mortality of infants (40%) has prompted Penn State to develop a pediatric version of the clinically successful adult device. Although the primary use of this device will be bridge-to-transplant, there has been sufficient clinical data to demonstrate the efficacy of VADs in a bridge-to-recovery setting. However, removing the patient from the device, a process known as weaning, demands operation of the device at a lower beat rate and concomitant increased risk for thromboembolism. Previous studies have shown that the interrelated flow characteristics necessary for the prevention of thrombosis in a pulsatile VAD are a strong inlet jet, a late diastolic recirculating flow, and a wall shear rate greater than 500/s. In an effort to develop a strong inlet jet and rotational flow pattern at a lower beat and flow rate, we have compressed diastole by altering the end-diastolic delay time (EDD). Particle image velocimetry was used to compare the flow fields and wall shear rates in the chamber of the 12 cc Penn State pulsatile pediatric VAD operated at 50 beats per minute using EDDs of 10, 50, and 100 ms. Although we expected the 100 ms EDD to have the best wall shear profiles, we found that the 50 ms EDD condition was superior to both the 10 and 100 EDD conditions, due to a longer sustained inlet jet. [source]


Mixed convection in a horizontal square duct with local inner heating

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2005
Koichi Ichimiya
Abstract Numerical analyses were performed for the effect of local inner heating on the mixing flow in a horizontal square duct. Three-dimensional governing equations were solved for Re = 100,Pr = 0.72, and six kinds of inner heating sizes in a duct, with insulated walls or uniform temperature walls. Local inner heating induced the local buoyancy force and produced four recirculating flows across a section in a thermally insulated duct. In a horizontal square duct with uniform wall temperature, the interaction of the buoyancy-induced flows by temperature difference between the fluid and the local inner heating, and between the fluid and the walls reduced the maximum intensity of the secondary flow. Two recirculating flows were generated in a downward region. Heat transfer was locally enhanced or depressed corresponding to the flow situation. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(3): 160,170, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20056 [source]