Fluid Wedge Research Articles

Endo/exothermic chemical processes influences of tri-hybridity nanofluids flowing over wedge with convective boundary constraints and activation energy

Prandtl Eyring fluid and stretchable wedge have multiple usages in many industries. The present study aims to investigate the impact of modified Buongiorno trihybrid nanofluid on Prandtl Eyring fluid past a wedge with the addition of various influences like endothermic/exothermic reactions, thermal radiation, and thermal conductivity, Cattaneo-Christov double diffusion. Aluminium alloys (AA7072), Aluminium alloys (AA7075) and Silver (Ag) are used as nanocomponents. Prandtl Eyring fluid is employed as a conventional liquid in the preparation of nanofluids by blending nano components into the base fluid. Further, the flow model is imposed with Modified Buongiorno nanofluid. By using the similarity approach, the proposed mathematical flow model of partial differential equations (PDEs) is turned into highly nonlinear ordinary differential equations (ODEs). Throughout the whole range of material parameters, the solution for the ensuing nonlinear boundary value issue is given by employing the finite element method (FEM). The numerical results of Prandtl Eyring ternary HNF motion, thermal and solute profiles are performed through graphical amassment on the collected data and discussed in detail. The numerical significances of material sections, such as the frictional force, local Nusselt quantity, and local Sherwood number requirements, are supplied in tabular form. Further, it also presents the validation and performance characteristics of the proposed device with previously published work and found excellent accuracy. In comparison to hybrid nanoparticles, the consequences reveal that heat transmission is amplified in the case of tri-hybrid nanoparticles. The numerical consequences show that the heat transfer amount reduces in the situation of exothermic reactions parameter Ω<1 and rises due to magnification in the status of endothermic reactions parameter Ω>1.

The influence of radiation on MHD boundary layer flow past a nano fluid wedge embedded in porous media

This study takes into account the viscous dissipation of the laminar viscosity and radiation influence of the MHD heat and mass transfer nanofluid flow across two dimensional boundary layers in the porous medium in the existence of heat, thermophoresis and Brownian motion influence. The governing equations are transformed into nonlinear ordinary differential equations by the aid of the similarity transformation. The solution is numerically solved with the MATLAB in the built-in bvp4c solver. The influences of the appropriate flow parameters are analysed in graphs and in tabular form.

Numerical Simulation of Water Entry of Wedges in Waves Using A CIP-Based Model

In this study, the water entry of wedges in regular waves is numerically investigated by a two-dimensional in-house numerical code. The numerical model based on the viscous Navier-Stokes (N-S) equations employs a high-order different method—the constrained interpolation profile (CIP) method to discretize the convection term. A Volume of Fluid (VOF)-type method, the tangent of hyperbola for interface capturing/slope weighting (THINC/SW) is employed to capture the free surface/interface, and an immersed boundary method is adopted to treat the motion of wedges. The momentum source function derived from the Boussinesq equation is applied as an internal wavemaker to generate regular waves. The accuracy of the numerical model is validated in comparison with experimental results in the literature. The results of water entry in waves are provided in terms of the impact force of wedge, velocity and pressure distributions of fluid. Considerable attention is paid to the effects of wave parameters and the position of wedge impacting the water surface. It is found that the existence of waves significantly influences the velocity and pressure field of fluid and impact force on the wedges.

On the rarefaction waves of the two-dimensional compressible Euler equations for magnetohydrodynamics

The expansion of a wedge of magnetic fluid into vacuum is studied in this paper. The magnetic fluid away from the sharp corner of a wedge expands into the vacuum as two plane-symmetric rarefaction waves, and the problem can be reduced to the interaction of these two rarefaction waves. In order to determine the flow in the interaction zone, we formulate a Goursat problem for the two-dimensional, self-similar Euler equations of magnetohydrodynamic. This system is of mixed type, and the type at each point is determined by the local fluid velocity and the local magneto-acoustic speed. We establish that the system is uniformly hyperbolic in the interaction zone when the half-angle of the wedge is less than some angle [Formula: see text], while the existence of a global classical solution to the Goursat problem is proven by a method of characteristic decomposition.

Heat transfer modelling in Discrete Element Method (DEM)-based simulations of thermal processes: Theory and model development

Over the past decade, DEM-based simulation has become a promising alternative to physical measurements of thermal particulate systems. Despite their rapid advancement and successful applications to a wide range of industrial processes, a comprehensive review of the theory that underpins the thermal DEM-based simulations is yet to be conducted. This work presents a critical and in-depth review of all major thermal models and heat transfer mechanisms pertinent to DEM-based simulations. Other critical aspects such as boundary conditions and particle body temperature distribution that were often overlooked are also summarised and discussed, aiming to provide a clear path for the development of robust thermal DEM-based models.The quasi-analytical solution based on the Hertzian contact theory proves classic and remains the main method to solving the conduction of static contacts. Recent attempts have been mainly directed towards improving the calculation of conduction through collisional contacts and the thin wedge of interstitial fluid between particles. Empirical correlations that were developed before 1981 remain predominant in calculating the fluid-particle convection coefficient. Though more accurate, the discrete models of radiation that rely on the solution of view factors amongst individual particles have been applied much less than the continuum models due to the significant computational overhead. Generally, previous efforts have led to the construction of a solid framework of thermal DEM-based models. Significant work is required to improve existing or develop new heat transfer sub-models, particularly those for accurate and efficient modelling of conduction and radiation in particle-laden systems.

Revisiting inclination of large-scale motions in unstably stratified channel flow

Observational and computational studies of inertia-dominated wall turbulence with unstable thermal stratification have demonstrated that the inclination angle of large-scale motions (LSMs) increases with increasing buoyancy (as characterized by the Monin–Obukhov stability variable ). The physical implications of this structural steepening have received relatively less attention. Some authors have proposed that LSMs thicken – yet remain attached to the wall – with increasing buoyancy (Salesky & Anderson, J. Fluid Mech., vol. 856, 2018, pp. 135–168), while others have presented evidence that the upstream edge of an LSM remains anchored to the wall while its downstream edge lifts away from the wall (Hommema & Adrian, Boundary-Layer Meteorol., vol. 106, 2003, pp. 147–170). Using a suite of large-eddy simulations (LES) of unstably stratified turbulent channel flow, we demonstrate that buoyancy acts to lift LSMs away from the wall, leaving a wedge of fluid beneath with differing momentum. We develop a prognostic model for LSM inclination angle that accounts for this observed structure, where the LSM inclination angle is the sum of the inclination angle observed in a neutrally stratified wall-bounded turbulent flow, , and the stability-dependent inclination angle of the wedge . Reported values of from the literature, LES results and atmospheric surface layer observations are found to be in good agreement with the new model for .

Influence of interface slip on the surface frictional force of texturing sliding bearing

Purpose The purpose of this paper is to explore the sensitive parameters affecting the friction resistance of sliding bearings under different interface slip conditions and the influence of the texture position of circular pits on the friction force of sliding bearings. Design/methodology/approach Based on the mechanical equilibrium equation and Newton's viscous fluid mechanics formula and wedge oil film model, the calculation model of sliding bearing friction resistance under interface slip state is established, and the influence of interface slip on friction resistance under different slip conditions is analyzed by means of ANSYS. Friction simulation model of circular pit textured journal bearing under different interface slip conditions. Findings The friction resistance of bearings is mainly determined by journal linear velocity, oil film slip ratio, pressure of inlet and outlet of bearings, oil film thickness and bearing capacity. When both the upper and lower surfaces of the oil film slip, the friction resistance decreases significantly, which is only 4-17 per cent of that without slip. And the friction force of the texture model of circular pit at the exit is better than that at the entrance and the middle of the pit. Originality/value Relevant research results will lay a new theoretical foundation for friction reduction and optimization design of sliding bearings.

Computational and asymptotic methods for three-dimensional boundary-layer flow and heat transfer over a wedge

This paper is devoted to mathematical analysis of three-dimensional boundary-layer flow and heat transfer over a wedge. The boundary layer is formed due to the flow of a viscous and incompressible fluid and grows downstream along the walls of the wedge. This is appropriately approximated by a power of distances along both lateral directions. This analysis introduces a shear-to-strain-rate parameter $$\gamma$$ in the study which plays an essential role in three-dimensional boundary-layer study. A set of boundary-layer equations along with the conservation of energy has been transformed into a coupled nonlinear ordinary differential equations. Two methods are employed. The fluid–wedge interaction problem is solved in the circumstances where the equations are linearized and obtained the solutions in terms of confluent hypergeometric functions, and otherwise, the full-nonlinear problem numerically using the Keller-box method. In the former case, the results of eigenfunction analysis that is based on asymptotic study of the problem qualitatively support the latter numerical results. In either methods, the existence of solutions and range of parameter domain depending on various physical quantities is successfully analyzed. The two different approaches give good agreement with each other in predicting the velocity and temperature profiles in three-dimensional boundary layer. However, both approaches show that a solution to the problem exist only $$-\,1< \gamma < \infty$$ . Since the Reynolds number is asymptotically large, the flow clearly divides into two regions showing the effects of viscosity and thermal conductivity. The velocity and thermal profiles are found to be benign. Flow always attached to the wedge surfaces and, thus, related thicknesses are becoming thinner. Extensive comparisons of the various results are made and a possible explanation on the results is discussed in some detail.

Performance Study of Conical Hydrodynamic Bearing Under Different Semi Cone Angle on Conical Hydrodynamic Bearing Performance With Air Lubrication

Bearing plays crucial role in the functioning of almost all industries such as chemical, petrochemical, automotive, and various process industries. Bearing supports, guides, and reduces the friction of moving machine parts. The lubrication in fluid film journal bearing is used to separate two relatively sliding surfaces with a thin film. The fluid wedge between shaft and bearing causes pressure built to support the load. Conical bearing supports load in both axial and radial direction over separate cylindrical journal bearing and thrust bearing. Conical bearing replaces two bearings with one. The present study related to performance analysis of conical hydrodynamic bearing with air as lubricant. In this paper, semi-cone angle effect is analyzed on the pressure distribution of air lubricated conical bearing. The performance is carried out with semi cone angle of 5, 10, 20, 45, 60 and 80 degrees using ANSYS workbench. Results shows maximum pressure distribution is obtained for the semi cone angle between 5 to 10. Bearing load capacity in radial direction reduces after 450 angle.

A red-corundum-bearing vein in the Rai–Iz ultramafic rocks, Polar Urals, Russia: the product of fluid activity in a subduction zone

The veins in the mantle wedge peridotite can record the activity of slab-derived melt/fluid, which is the reflection of the material circulation between crust and mantle. A red-corundum-bearing vein is present in the Rai–Iz ultramafic rocks in the Polar Urals, Russia. The ultramafic rocks are harzburgite and dunite, and the red corundum-bearing rocks consist of phlogopite, paragonite, oligoclase, red corundum, and chromian spinel. Red corundum occurs as prophyroblasts or fine grains that contain 92–98 wt% Al2O3 and 2–7 wt% Cr2O3. Chromian spinel has Cr# values ([100Cr/ (Cr + Al)] atomic ratio) of 46–78. Oligoclase is characterized by An values of 20–30. Phlogopite is Ba-rich (BaO = 0.8–2.7 wt%) and paragonite is Sr-rich (SrO = 0.8–2.3 wt%). Zircons from the oligoclasite show oscillatory zoning and Th/U values of <0.2, indicating crystallization from fluid. A zircon weighted-mean 206Pb/238U age of 382 ± 2 Ma and a phlogopite 40Ar/39Ar plateau age of 377 ± 3 Ma indicate that the red-corundum-bearing vein formed at 380 Ma. The occurrence and formation age of the vein, structure and composition of vein minerals, and zircon εHf values (−11 to +13) suggest that the vein was the product of interaction between a subduction-zone-derived fluid and mantle wedge peridotite.

IDENTIFICATION OF FRICTION CONDITIONS IN HUMAN JOINTS

The purpose of the paper is to explain the friction conditions and the lubrication mechanism in healthy joints, based on rheological tests of synovial fluid and the identification of structures and the shape of articular surfaces. The tests were performed on cadaver preparations of large lower limp joints: hip, knee, and ankle joints. The analysis included combined experimental activities with the use of modern research and test techniques in the area of viscosity and microscopy as well as diagnostic imaging, image analysis, modelling, and FEM simulation. The tests performed allowed for the analysis of lubrication process which can be described as bioelastohydrodynamic lubrication (BEHL). The most important are viscoelasticity properties of the synovial fluid and the process whereby the external load is taken over by the pressure generated by a set of oil wedges of synovial fluid formed by naturally wavy articular surface. The multi-layer structure of the joints is characterised by variable wavy shape of cartilaginous surfaces and of bone tissue and by the variable wavy thickness of the cartilage.

Guidance principle of deep-hole cutting tools based on fluid wedge effect

The existing guidance principle of deep-hole cutting tools has been used for more than 200 years. A novel guidance principle of deep-hole cutting tools is proposed based on the fluid wedge effect. The novel guidance principle stems from hydrodynamic lubrication in journal bearings and can prevent deep-hole cutting tool deviation during machining. A novel wedge-shaped body is fixed to the drill tip and the shank. The wedge-shaped body and the wall of the deep hole form four wedge-shaped spaces, and the cutting oil is drawn into the four wedge-shaped spaces to form four wedge-shaped oil films. Pressure develops in the oil film, and the forces of the oil films force the wedge-shaped body together with the drill tip and the shank to be centered in the deep hole and to move along the axis of the deep hole. The resultant force of the oil films tends to rectify the deviation of the cutting tool, and the resultant force equals 228 N in one example. Analysis and calculation of the forces of the wedge-shaped oil films were conducted, and the force of each oil film was 128 N in another example. Experiments showed that the average straightness of the deep holes machined by the novel deep-hole cutting tools was less than that achieved using the existing cutting tool. The parameters of the wedge-shaped body influenced the force of the oil film and the straightness of the deep holes.

Consideration of the multizone hydrodynamic friction, the misalignment of axes, and the contact compliance of a shaft and a bush of sliding bearings

The second version of the original Bearing Builder Finite Element Method (BBFEM) software and its application for analyzing the hydrodynamics of cylindrical sliding bearings has been briefly described. The two-dimensional problem of the lubricating fluid flow in a bearing clearance taking into consideration the different types of deviations in the contact surface from a cylindrical shape has been solved by the finite element method. The bearing design that leads to the formation of several hydrodynamic friction zones (fluid wedges) has been considered. The role of the contact compliance of a shaft and a bush and the operation factors that cause the deviation from the initial cylindrical shape of a bearing, including the deformations and the misalignment of the shaft and bush is shown by citing specific examples of antifriction composites of different compositions.

Flow Behavior of Ponded Turbidity Currents

Abstract Sea-floor topography can constrict, deflect, or reflect turbidity currents resulting in a range of distinctive deposits. Where flows rebound off slopes and a suspension cloud collects in an enclosed basin, ponded or contained turbidites are deposited. Ponded turbidites have been widely recognized in slope mini-basins and on small, structurally confined basin floors in strike-slip and foreland-basin settings. They can have a variable internal structure the significance of which remains poorly understood in terms of flow behavior. New experiments demonstrate that the ponding process can comprise up to four phases: 1) cloud establishment, 2) inflation, 3) steady-state maintenance, and 4) collapse. The experiments explored the behavior of sustained turbidity currents draining into small basins and show that the ponded suspensions that form are characterized by an important internal interface; this divides a lower outbound-moving layer from an upper return layer. The basal layer evolves to constant concentration and grain size, whereas the upper layer is graded (concentration and grain size decrease upward). During the cloud inflation stage, the concentration and velocity profiles of the ponded suspension evolve, and this phase can dominate the resulting deposit. Outbound internal waves can travel along the interface between the outbound and return layers and impinge against the confining slope, and their amplitude is highest when the density contrast between layers is greatest, e.g., when the input flows are thin and dense. The experiments show that flow reversals can arise in several ways (initial rebound, episodic collapse of the wedge of fluid above the counter slope, “grounding” of the internal velocity interface) and that despite steady input, velocities decay and the deposit grades upwards. Internal waves emanate from the input point, i.e., do not form as reflections off the counter slope. The internal grain-size interface within the suspension may dictate textural trends in sands onlapping the confining slopes. Where flows are partially ponded, internal waves can generate pulsing overspill to basins down dip.

Level set reinitialization at a contact line

When a level-set signed distance function is reinitialized in the vicinity of a contact line, there is a “blind spot” that prevents an accurate reconstruction of a signed distance function. The numerical method can create parasitic velocity currents near this region. If additional contact-line physics are included, the parasitic velocity currents would pollute the solution and alter the physical behavior. In this study, a modified reinitialization routine is proposed that combines the standard Hamilton–Jacobi equation with a relaxation equation for those grid cells along a wall in the blind spot. Two test cases, an angled fluid wedge (zero curvature) and a circular fluid arc (constant curvature), are used to evaluate the numerical error induced by different methods. The proposed method has less numerically-induced interface distortion than other techniques examined. Furthermore, this routine can be easily extended to three dimensions. Drops sliding on a wall are simulated in both two and three dimensions to demonstrate the advantages of this method. A spreading fluid interface further shows that this method allows contact lines to merge naturally.

Comparative Cryo-SEM and AFM studies of hylid and rhacophorid tree frog toe pads

Cryo-scanning electron microscopy (cryo-SEM) and atomic force microscopy (AFM) offer new avenues for the study of the morphology of tree frog adhesive toe pads. Using these techniques, we compare toe pad microstructure in two distantly related species of tree frog, Litoria caerulea, White (Hylidae) and Rhacophorus prominanus, Smith (Rhacophoridae), in which the toe pads are considered to be convergent. AFM demonstrates the extraordinary similarity of both surface microstructures (largely hexagonal epithelial cells surrounded by deep channels) and nanostructures (an array of nanopillars, ca. 350 nm in diameter, all with a small dimple at the apex). The cryo-SEM studies examined the distribution of the fibrillar cytoskeleton within the different layers of the stratified toe pad epithelium, demonstrating that the cytoskeletal elements (keratin tonofilaments) that lie at an angle to the surface are relatively poorly developed in L. caerulea, clearly so in comparison to R. prominanus. Cryo-SEM also enabled the visualization of the fluid layer that is critical to a toe pad's adhesive function. This was achieved by examination of the frozen fluid residues left behind after removal of a toe within the cryo-SEM's experimental chamber. Such 'toeprints' demonstrated the presence of a wedge of fluid surrounding each toe pad, as well as fluid filling the channels that surround each epithelial cell. Cryo-SEM was used to examine epithelial cell shape. In a sample of 582 cells, 59.5% were hexagonal, the remainder being mainly pentagonal (23.1%) or heptagonal (16.1%). The distribution of differently-shaped cells was not random, but was not associated with either pad curvature or the distribution of mucous pores that provide fluid for the frogs' wet adhesion mechanism. Our main finding, the great similarity of toe pad structure in these two species, has important implications for biomimetics, for such convergent evolution suggests a good starting point for attempts to develop adhesives that will function in wet conditions.

A Seismic Structure Study in the Kaoping Area, Southwestern Taiwan

The difference between S ‐wave and S ‐to‐ P ‐wave conversion ( S P phase) arrival times is enhanced with rectilinear motion detector filtering to describe alluvial‐sediment thickness in the Kaohsiung–Pingtung (Kaoping) plains area. A more complete understanding of the underground structures of the Kaoping area is provided in this paper and explains why the surrounding regions in Taiwan experience more earthquakes than the Kaoping area. Data are based on seismic activity recorded by the portable array for numerical data acquisition (PANDA) for the period from 1995 to 1997. The difference between S ‐wave and S P ‐phase arrival times shows that the sedimentary layer is thicker along the west and southwest coasts. P ‐wave travel‐time residuals, high‐frequency attenuation parameters Kappa, and quality factor Q P , Q S , and coda waves confirm this result. We also determined the orientation of the Chaochou fault using the first motion of P ‐wave arrivals. To the east of the Chaochou fault, stress trends southeast–northwest, while to the west, it trends northeast–southwest. The change in stress trends east and west of Chaochou fault suggests the presence of a highly fluid accretionary wedge in the Kaoping area. The Chaochou fault forms a seismically active tectonic boundary with the uplift of the hanging wall leading to westward tilting of the basement of the Kaoping plains. We demonstrate that these features are the reason there are relatively few earthquakes in the Kaoping area. The presence of a highly fluid accretionary wedge is indicated by a thick alluvial layer in the west and southwest Kaoping coasts; the Peikung High acts as the indenter that may allow seismic energy to escape and reduce the number of earthquakes in the region. Online Material: Figures illustrating calculations of Kappa, Q c , P ‐ and S ‐wave spectra, Q P , and Q S from ground‐motion data.

Apparent-contact-angle model at partial wetting and evaporation: Impact of surface forces

This theoretical and numerical study deals with evaporation of a fluid wedge in contact with its pure vapor. The model describes a regime where the continuous wetting film is absent and the actual line of the triple gas-liquid-solid contact appears. A constant temperature higher than the saturation temperature is imposed at the solid substrate. The fluid flow is solved in the lubrication approximation. The introduction of the surface forces in the case of the partial wetting is discussed. The apparent contact angle (the gas-liquid interface slope far from the contact line) is studied numerically as a function of the substrate superheating, contact line velocity, and parameters related to the solid-fluid interaction (Young and microscopic contact angles, Hamaker constant, etc.). The dependence of the apparent contact angle on the substrate temperature is in agreement with existing approaches. For water, the apparent contact angle may be 20° larger than the Young contact angle for 1 K superheating. The effect of the surface forces on the apparent contact angle is found to be weak.

Surface-tension-driven flow in a half-plane

We study the motion of a fat wedge of inviscid fluid, of angle π - e with e ≪ 1, in contact with a rigid wall along one edge. Initially the fluid is at rest. When t = 0, the contact angle at the tip of the wedge is changed to π - λe. The resulting flow and motion of the contact point are determined by a balance of surface tension and inertia. As there are no geometric length scales imposed, we obtain a similarity solution with lengths scalings as t 2/3 . When λ = O(1), we can linearize the domain to a half-plane with the free-surface displacement coupled to the velocity potential via linear boundary conditions. We solve the leading-order boundary-value problem numerically, with the aid of the boundary integral method, and also present asymptotic solutions for ≫ 1 and |λ - 1| ≪ 1. For ≫ 1, the asymptotic solution can be constructed in terms of an inner and an outer region, with the phase and amplitude of the capillary wave on the free-surface set in the inner region via the solution to the dock problem. The decay of the mean free-surface displacement matches into the outer region to determine the relationship between λ and the contact point position x c . For |λ - 1| ≪ 1, the leading-order problem can be solved exactly using Mellin transforms.

On the Origin of Paleocurrent Complexity Within Deep Marine Channel Levees

Abstract Complex patterns of temporal and spatial variation in paleoflow within individual turbidites have been inferred from studies of both recent and ancient submarine channel–levee sands and sandstones. Previous interpretations of these paleocurrents have invoked “shifting patterns of meandering streamlines” in essentially unconfined flows, and in some cases topographic deflection of flows as they spilled from the channel. However, other flow indicators, such as current ripples, suggest that overbank flow may exhibit more uniform flow directions. Here we re-examine the spatial and temporal evolution of overbank flow on submarine channel levees, using grain fabric data from the Cretaceous Rosario Formation and extant data from the recent Amazon channel. We integrate these observations with our theoretical understanding of the long-term evolution of overbank flow processes to propose a process-based model of evolution of overbank flow across submarine channel levees. Overbank flow over levees is inferred to be dominated by three main processes: (1) gravity forces that attempt to direct flow down the local maximum slope; (2) inherited momentum from the channelized flow, which in many cases is closer to the axial flow direction; (3) development over time of an overbank wedge of fluid that moves broadly parallel to the direction of the main channel. The interaction among these processes varies both in space and time, and collectively accounts for the observed paleoflow variations inferred from deposits. This study may allow better interpretation of depositional sub-environments within levee turbidites, both in core and in outcrop.