On the structural features of fiber suspensions in converging channel flow

The structural features of fiber suspensions are dependent on the fiber alignment in the flows. In this work the orientation distribution function and orientation tensors for semi-concentrated fiber suspensions in converging channel flow were calculated, and the evolutions of the fiber alignment and the bulk effective vis-cosity were analyzed. The results showed that the bulk stress and the effective viscosity were functions of therate-of-strain tensor and the fiber orientation state ; and that the fiber suspensions evolved to steady alignment and tended to concentrate to some preferred directions close to but not same as the directions of local stream-lines. The bulk effective viscosity depended on the product of Reynolds number and time. The decrease of ef-fective viscosity near the boundary benefited the increase of the rate of flow. Finally when the fiber alignment went into steady state, the structural features of fiber suspensions were not dependent on the Reynolds numberbut on the converging channel angle.

Wave Propagation in A Converging Channel of Arbitrary Configuration

A numerical solution was derived to determine wave field in a converging channel bounded by rubble-mound jetties. The solution was achieved by applying boundary element method. The model was applied to analyze the effect of channel convergence, the cross-section of the jetties and their physical and damping properties on wave field in the channel. The study reveals numerous non-intuitive results specific for jetted and convergent channels. The analysis shows that wave reflection is usually low and is of secondary practical importance. Wave transmission strongly depends on the channel geometry and transmitted waves may be higher than incident waves, despite reflection and damping processes. Moreover, wave transmission depends on physical and damping properties of rubble jetties and the results show that wave transmission may increase with the increasing damping properties of jetties, which is a non-intuitive feature of wave fields in jetted channels. The analysis reveals several novel results of practical importance. It is shown that the rubble-mound jetties should be constructed from the material of high porosity, which ensures low transmission. More attention should be devoted to hydraulic properties of porous materials. It is recommended to use the material of moderate damping properties. The material of high damping properties often increases the wave transmission. It is possible, by a selection of rubble-mound material, to obtain lower transmission level for steep waves than for waves of moderate steepness. A series of laboratory experiments were conducted in the wave flume to verify the theoretical results. The comparisons show that theoretical results are in fairly good agreement with experimental data.

Yampa River-Colorado River Drainage Divide Origin Determined from Topographic Map Evidence, Southern Routt County, Colorado, USA

Detailed topographic map evidence and a new Cenozoic geologic and glacial history paradigm are used to determine the previously unexplained Yampa River-Colorado River drainage divide origin. The Yampa River now flows in a north direction away from the Colorado River (between the Park Range to the east and the Flat Tops region to the west) before turning in a west direction to reach the Unita Mountains where it joins the south-oriented Green River, which eventually joins the southwest-oriented Colorado River. Topographic maps show the Yampa-Colorado River drainage divide is asymmetric with steeper slopes leading to the Colorado River, barbed (south-oriented) tributaries leading to north-oriented Yampa River headwaters (especially near the Yampa River turn to the west), and evidence of a large north-to-south oriented diverging and converging channel complex that preceded present-day drainage routes. Map evidence is interpreted to mean massive south-oriented floods flowed through what are now north-oriented Yampa River headwaters valleys and that headward erosion of a deep west-oriented valley beheaded and reversed those south-oriented flood flow channels to create the north-oriented Yampa River headwaters and the Egeria Park area Yampa-Colorado River drainage divide seen today. Large south-oriented floods leading to the Colorado River (while regional uplift was occurring) are inconsistent with accepted Cenozoic geologic and glacial history paradigm predictions, but are predicted by a newly proposed Cenozoic geologic and glacial history paradigm in which a thick continental ice sheet created a deep “hole” by eroding underlying bedrock and also by causing crustal warping that raised the present-day northern Colorado east-west continental divide as immense south-oriented meltwater floods flowed across it.

Dissipative flow features of Carreau nanofluid with thermal radiation inside plane wall channel:Jeffery-Hamel analysis

The current article communicates a numerical investigation on laminar flow of dissipative generalized Newtonian Carreau nanofluid flowing through vertical conduit with converging and diverging plane walls.Thermal and concentration characteristics due to enthalpy change,activation energy,and non-linear thermal radiation have been examined in the presence of buoyancy forces.The channel walls for both temperature and volumetric fraction are assumed to be isothermal.The instability mechanism of nanofluids is reported using a two-phase nanofluid model,which works reasonably well for nanoparticle concentrations below a certain threshold.A Jeffery-Hamel(J-H)flow model is developed by assuming an incompressible purely radial flow of Carreau nanofluids with heat and mass transportation.Using the suitable non-dimensional variables,the resulting nonlinear partial differential equations are turned into a system of ordinary differential equations.The modified governing equations are then numerically solved using the built-in boundary value problem solver bvp4c,on the template form of commercial software MATLAB.The impacts of material,geometrical and thermophysical parameters governing the J-H problem are discussed and illustrated.Results indicate that higher buoyance forces incline the velocity profiles in converging enclosure,while a slight reduction is perceived in opposing forces.A significant decrease of wall heat transmission is reflected for larger values of activation energy and radiation parameter.For endorsing this communication,a comparison analysis is established with existing research and noticed a remarkable agreement.Practically,the flow inside converging and diverging channels are deployed in nuclear reactors that use plate-type nuclear energies,high heat-flux condensed heat exchangers,high-performance micro-electronic cooling systems,jets,rockets nozzles,and jet propulsion inlet.

Radiative Effects on Mixed Convection in a Uniformly HeatedVertical Convergent Channel with an Unheated Moving Plate

Fluids engineering is extremely important in a wide variety of materials processing systems,such as soldering,welding,extrusion of plastics and other polymeric materials,Chemical Vapor Deposition(CVD),composite materials manufacturing.In particular,mixed convection due to moving surfaces is very important in these applications.Mixed convection in a channel,as a result of buoyancy and motion of one of its walls has received little research attention and few guidelines are available for choosing the best performing channel configuration,particularly when radiative effects are significant.In this study a numerical investigation of the effect of radiation on mixed convection in air due to the interaction between a buoyancy flow and an unheated moving plate induced flow in a uniformly heated convergent vertical channel is carried out.The moving plate has a constant velocity and moves in the buoyancy force direction.The principal walls of the channel are heated at uniform heat flux.The numerical analysis is accomplished by means of the commercial code Fluent.The effects of the wall emissivity,the minimum channel spacing,the converging angle and the moving plate velocity are investigated and results in terms of air velocity and temperature fields inside the channel and wall temperature profiles,both of the moving and the heated plates,are given.Nusselt numbers,both accounting and not for the radiative contribution to heat removal,are also presented.