A Stokesian analysis of a submerged viscous jet impinging on a planar wall

2012 ◽  
Vol 712 ◽  
pp. 531-551 ◽  
Author(s):  
A. M. J. Davis ◽  
J. H. Kim ◽  
C. Ceritoglu ◽  
J. T. Ratnanather
Keyword(s):  
Flow Analysis ◽  
Wall Stress ◽  
Wall Pressure ◽  
Creeping Flow ◽  
Parabolic Profile ◽  
Sensory Hair Cells ◽  
Viscous Jet ◽  
Planar Wall ◽  
Two Stages ◽  
Density Singularity

AbstractThe wall pressure and wall shear stress of a submerged viscous jet impinging on an infinite planar wall are derived. The whole creeping flow of semi-infinite extent is generated via distributions on a cylindrical pipe of tangentially and normally directed Stokeslets which are modified to achieve no-slip at the wall in two stages. First the pressure and vorticity jumps associated with the Poiseuille flow upstream in the pipe are readily forced, and then further distributions, of zero density far upstream but with square-root density singularity at the orifice $z= h$, are added to achieve no-slip on the pipe wall. Thus the adjustment of the interior pipe flow from its upstream parabolic profile to its exit profile is fully included in – and a major feature of – this creeping flow analysis. The maximum plane wall pressure is always located on the axis $r= 0$, and decreases as $h$ increases to alleviate the obstruction effect of the wall. The interaction of the inflow with the ambient fluid in the neighbourhood of $z= 0$ causes the wall stress to rise rapidly to a maximum and then decay with the radial position of this maximum increasing as $h$ increases. This behaviour is discussed in the context of physiological experiments on auditory sensory hair cells that motivated this study.

scholarly journals The Stokesian flow field of an oscillatory submerged viscous jet impinging on a planar wall

2013 ◽  
Vol 469 (2157) ◽  
pp. 20130282 ◽  
Author(s):  
A. M. J. Davis ◽  
J. H. Kim ◽  
G. M. Gunter ◽  
J. T. Ratnanather
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Field ◽  
Wall Pressure ◽  
Half Cycle ◽  
Point Forces ◽  
Planar Wall ◽  
Wall Shear ◽  
Two Stages ◽  
Pressure Driven Flow

This model of experiments on auditory sensory hair cells extends previous work via distributions on a cylindrical pipe of tangentially and normally directed oscillatory point forces, which are modified to achieve no-slip at the wall in two stages. Starting with the pressure and vorticity jumps associated with the oscillatory pressure-driven flow upstream in the pipe, the adjustment of the interior pipe flow from its upstream complex-valued profile to its exit profile is fully included. This is essentially achieved by modifying the steps of the steady case analysis. The flow field oscillates with phase dependent on position, and the level curves of the streamfunction indicate instantaneous particle motion but not streamlines. Thus, an eddy is not indicated by the closed curve that occurs midway through the two half cycles and is due to competing forces between the inflow and outflow, particularly in the second half cycle as the fluid enters the pipe. The wall pressure and wall shear stress also oscillate with the non-uniformities concentrated near the origin, but are relatively damped midway through the two half cycles. Independent of the orifice location, there is a small effect of frequency on the wall pressure and the wall shear stress.

CREEPING FLOW ANALYSIS OF SLIGHTLY NON-NEWTONIAN FLUID IN A UNIFORMLY POROUS SLIT

2019 ◽  
Vol 9 (1) ◽  
pp. 140-158 ◽  
Author(s):  
Hameed Ullah ◽  
◽  
Huafei Sun ◽  
Abdul Majeed Siddiqui ◽  
Tahira Haroon ◽  
...  
Keyword(s):  
Newtonian Fluid ◽  
Flow Analysis ◽  
Creeping Flow

Prediction of Vortex Shedding From a High Reynolds Number Airfoil Using LES With and Without Wall Model

2006 ◽  
Author(s):  
Peter A. Chang ◽  
Meng Wang ◽  
Jonathan Gershfeld
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Vortex Shedding ◽  
High Reynolds Number ◽  
Wall Stress ◽  
Wall Pressure ◽  
Pressure Side ◽  
Stress Model ◽  
High Reynolds

ATTACHED, wall-bounded flows impose computational requirements on LES that increase drastically with Reynolds number. For that reason, even simple geometries, such as airfoils at small angles of attack, with spanwise uniform section shape, challenge the bounds of LES as chord-based Reynolds numbers increase much above 1 million. Of particular concern is the ability of LES to predict the occurrence, and strength of, weak vortex shedding from the airfoil trailing edge (by weak vortex shedding we mean that the acoustic vortex shedding signature may rise only a few decibels above that for the broadband turbulent boundary layer acoustic sources). Correct prediction of weak vortex shedding may depend on accurately predicting the flow over the entire airfoil that includes the attached, turbulent upstream flow, adverse pressure gradient and separated flow regions and finally, the turbulent wake. This paper compares results of two full-LES and two LES with wall-stress model for the flow about a modified NACA 0016 airfoil with a 41° trailing edge apex angle and a slightly convex pressure side. Comparisons of vortex shedding, as measured by the power spectral density (PSD) of wall pressure fluctuations (WPF) on the pressure side of the TE and the PSD of the vertical velocity fluctuations in the wake are made. The results indicate that vortex shedding predictions are dependent upon the stream-wise and spanwise grid resolution. In order to reduce the large computational times required for simulating the high-Reynolds number flows with fully-resolved LES, a wall-stress model that solves the turbulent boundary layer equations in the near-wall region is applied. Compared with the fully-resolved LES, the LES with wall-stress simulations require about 20 percent the number of grid points and require about 10 percent of the computational time. However, the LES with wall stress model results under-predict the vortex shedding peak in the wake and are not able to predict the vortex shedding signature in TE wall pressure spectra. These results indicate that near-wall turbulence structures need to be resolved in order to correctly predict the occurence and strength of vortex shedding.

Modeling of Continuous Mixers in Polymer Processing

1985 ◽  
Vol 107 (1) ◽  
pp. 70-76 ◽  
Author(s):  
J. Arimond ◽  
L. Erwin
Keyword(s):  
Splitting Method ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Sufficient Conditions ◽  
Polymer Processing ◽  
Two Dimensions ◽  
Creeping Flow ◽  
Continuous Mixing ◽  
Model Mixing ◽  
Mixing Problem

The numerical modeling of creeping flow and continuous mixing in polymer processing equipment is considered. The decoupling of axial and transverse flow problems is the main subject of analysis. The conditions under which and the procedures whereby a steady three-dimensional mixing problem can be modeled via numerical procedures in two dimensions are discussed. The flow through a Kenics Static Mixer is chosen as a sample problem. Symmetry is exploited by formulating the problem in a nonorthogonal helical coordinate system, and a splitting method is devised for the resulting finite-difference equations which solves the axial and transverse problems alternately until convergence is reached. Three criteria are postulated as necessary and sufficient conditions for such decoupling. Finally, a method is presented whereby the result of the flow analysis can be used to model mixing. Graphical representations of the progress of mixing with down-channel displacement in the Kenics are obtained, and its mechanism of mixing is discussed.

Creeping flow analysis of an integrated microfluidic device for rheometry

2010 ◽  
Vol 165 (19-20) ◽  
pp. 1302-1308 ◽  
Author(s):  
H.C. Hemaka Bandalusena ◽  
William B. Zimmerman ◽  
Julia M. Rees
Keyword(s):  
Microfluidic Device ◽  
Flow Analysis ◽  
Creeping Flow

A Numerical Approach for the Design of the Compressor Impeller Exit Diameter Variations in a Marine Engine Turbocharger

2005 ◽  
Author(s):  
Hong-Won Kim ◽  
Seung-Hyup Ryu ◽  
Sang-Hak Ghal ◽  
Ji-Soo Ha ◽  
Sang-Ki Lee
Keyword(s):  
Pressure Ratio ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Medium Speed ◽  
Compressor Impeller ◽  
Marine Engines ◽  
Simple Change ◽  
Fluid Flow Analysis ◽  
Two Stages

A turbocharger has been designed to fulfill the requirements of medium speed marine engines, 900 kW output power at nominal operation point. The main objective of the design was to meet the requirements of engine power and increased engine operating range. This must be achieved by improving the degree of aerodynamic efficiency and the pressure ratio. The design was performed by the two stages. First, quasi-two dimensional program code was used to determine the main geometry of the compressor. Second, the detailed geometries of compressor blade were completed by using a three dimensional fluid flow analysis. The analyzed performance results were compared with the experimental data for the verification of their validity. Also, the designed three different impeller exits allow for a substantial performance variation. Increased compression ratio and mass flow rate of new optimized impeller were 10.08 and 27.3 percent higher than those of origin impeller, respectively. This simple change of design parameter offers considerable advantages to customers when upgrading their engines.

scholarly journals Swapping trajectories: a new wall-induced cross-streamline particle migration mechanism in a dilute suspension of spheres

2007 ◽  
Vol 592 ◽  
pp. 447-469 ◽  
Author(s):  
M. ZURITA-GOTOR ◽  
J. BŁAWZDZIEWICZ ◽  
E. WAJNRYB
Keyword(s):  
Shear Flow ◽  
Particle Migration ◽  
Creeping Flow ◽  
Spherical Particles ◽  
Self Diffusion ◽  
New Class ◽  
Planar Wall ◽  
Dilute Suspension ◽  
Wall Proximity ◽  
Self Diffusion Coefficient

Binary encounters between spherical particles in shear flow are studied for a system bounded by a single planar wall or two parallel planar walls under creeping flow conditions. We show that wall proximity gives rise to a new class of binary trajectories resulting in cross-streamline migration of the particles. The spheres on these new trajectories do not pass each other (as they would in free space) but instead they swap their cross-streamline positions. To determine the significance of the wall-induced particle migration, we have evaluated the hydrodynamic self-diffusion coefficient associated with a sequence of uncorrelated particle displacements due to binary particle encounters. The results of our calculations quantitatively agree with the experimental value obtained by Zarraga & Leighton (Phys. Fluids, vol. 14, 2002, p. 2194) for the self-diffusivity in a dilute suspension of spheres undergoing shear flow in a Couette device. We thus show that the wall-induced cross-streamline particle migration is the source of the anomalously large self-diffusivity revealed by their experiments.

Altered Fine Structure of B Lymphocytes Correlated with Defective Terminal Differentiation

1973 ◽  
Vol 31 ◽  
pp. 386-387
Author(s):  
Dale E. Bockman ◽  
L. Y. Frank Wu ◽  
Alexander R. Lawton ◽  
Max D. Cooper
Keyword(s):  
Immune Deficiency ◽  
B Lymphocytes ◽  
Plasma Cells ◽  
Present Report ◽  
Specific Antigen ◽  
Terminal Differentiation ◽  
Second Stage ◽  
Two Stages ◽  
Deficiency Diseases ◽  
Cell Line Generation

B-lymphocytes normally synthesize small amounts of immunoglobulin, some of which is incorporated into the cell membrane where it serves as receptor of antigen. These cells, on contact with specific antigen, proliferate and differentiate to plasma cells which synthesize and secrete large quantities of immunoglobulin. The two stages of differentiation of this cell line (generation of B-lymphocytes and antigen-driven maturation to plasma cells) are clearly separable during ontogeny and in some immune deficiency diseases. The present report describes morphologic aberrations of B-lymphocytes in two diseases in which second stage differentiation is defective.

Formation of Dislocation Channels in Neutron Irradiated Molybdenum

1972 ◽  
Vol 30 ◽  
pp. 672-673
Author(s):  
S. Mahajan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ambient Temperature ◽  
Room Temperature ◽  
Channel Formation ◽  
Early Stages ◽  
Transmission Electron ◽  
Three Stages ◽  
Two Stages ◽  
Polycrystalline Molybdenum

The evolution of dislocation channels in irradiated metals during deformation can be envisaged to occur in three stages: (i) formation of embryonic cluster free regions, (ii) growth of these regions into microscopically observable channels and (iii) termination of their growth due to the accumulation of dislocation damage. The first two stages are particularly intriguing, and we have attempted to follow the early stages of channel formation in polycrystalline molybdenum, irradiated to 5×1019 n. cm−2 (E > 1 Mev) at the reactor ambient temperature (∼ 60°C), using transmission electron microscopy. The irradiated samples were strained, at room temperature, up to the macroscopic yield point.Figure 1 illustrates the early stages of channel formation. The observations suggest that the cluster free regions, such as A, B and C, form in isolated packets, which could subsequently link-up to evolve a channel.

Ultrastructure of superficial neuromasts in the mottled sculpin, Cottus bairdi

1989 ◽  
Vol 47 ◽  
pp. 958-959
Author(s):  
W.R. Jones ◽  
S. Coombs ◽  
J. Janssen
Keyword(s):  
Hair Cells ◽  
Lateral Line System ◽  
Electron Microscopic ◽  
Line System ◽  
Dense Cores ◽  
Sensory Hair Cells ◽  
Cytoplasmic Vesicles ◽  
Cottus Bairdi ◽  
Mottled Sculpin ◽  
Upper Third

The lateral line system of the mottled sculpin, like that of most bony fish, has both canal (CNM) and superficial (SNM) sensory end organs, neuromasts, which are distributed on the head and trunk in discrete, readily identifiable groupings (Fig. 1). CNM and SNM differ grossly in location and in overall size and shape. The former are located in subdermal canals and are larger and asymmetric in shape, The latter are located directly on the surface of the skin and are much smaller and more symmetrical It has been suggested that the two may differ at a more fundamental level in such functionally related parameters as extent of myelination of innervating fibers and the absence of efferent innervation in SNM. The present study addresses the validity of these last two features as distinguishing criteria by examining the structure of those SNM populations indicated in Fig. 1 at both the light and electron microscopic levels.All of the populations of SNM examined conform in general to previously published descriptions, consisting of a neuroepithelium composed of sensory hair cells, support cells and mantle cells, Several significant differences from these accounts have, however, emerged. Firstly, the structural composition of the innervating fibers is heterogeneous with respect to the extent of myelination. All SNM groups, with the possible exception of the TRrs and CFLs, possess both myelinated and unmyelinated fibers within the neuroepithelium proper (Fig. 2), just as do CNM. The extent of myelina- tion is quite variable, with some fibers sheath terminating just before crossing the neuroepithelial basal lamina, some just after and a few retaining their myelination all the way to the base of the hair cells in the upper third of the neuroepithelium. Secondly, all SNMs possess fibers that may, on the basis of ultrastructural criteria, be identified as efferent. Such fibers contained numerous cytoplasmic vesicles, both clear and with dense cores. In regions where such fibers closely apposed hair cells, subsynaptic cisternae were observed in the hair cell (Fig. 3).

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