Horizontal Conduit Research Articles

Integrating the complex rheological Carreau model with the Graetz-Brinkman problem in a horizontal passage

ABSTRACT The current investigation emphasizes the influence of viscous dissipation in laminar forced convection internal flow for horizontal conduit using the non-Newtonian fluid. A Carreau fluid model is taken into account. The hydrodynamically developed velocity profile is obtained by employing a perturbation approach. A classical Graetz approach is utilized to achieve the solution of the developed energy equation while the MATLAB built-in command bvp4c is taken into account for the solution of the Eigenvalue problem. The negligible axial conduction and uniform physical characteristics are presumed. The influence of the viscous dissipation and model parameters on non-dimensional bulk temperature and Nusselt number is deliberated for both cooling and heating situations. The current analysis is valid for small values of Weissenberg number We ≤ 1 . The findings reveal that viscous dissipation has a significant impact on temperature distribution in both developing and fully established regions.

Hamilton–Crosser model impact for particle shape in a nanofluid flow influenced by variable thermal conductivity

Nanofluids with immersed metallic nanoparticles possess a higher thermal conductivity. The extent of this enhancement is largely dependent on the amount of the volume fraction, composition, nanoparticles’ shape, and size. The current study emphasizes nanofluid (gold-ethylene glycol) flow with different shapes past a horizontal infinite permeable conduit. The porous walls exhibit the fluid to move in or out of the channel as the walls expand or contract. The flow problem is modeled in a Cartesian coordinate system by employing the Tiwari-Das nanofluid model. Heat transfer is enhanced with the inclusion of Cattaneo–Christov combined with heat generation/absorption effect and temperature-dependent thermal conductivity. The Hamilton–Crosser model is adopted here for the cylindrical and platelet shapes nanoparticles. By invoking appropriate transformation, the equations are transmuted into ordinary differential equations and are solved numerically by employing the bvp4c approach. The influence of the key parameters is illustrated graphically. A protuberant decline is observed in the cylindrical shape nanoparticles in the thermal field on augmenting the thermal relaxation parameter. The drag force coefficient elevates on incrementing the volume fraction of nanoparticles. A significant correlation is noticed in the findings of the comparison with the existing literature.

Imaging of a shallow magma conduit system based on a high-power frequency-domain controlled-source electromagnetic survey

Mantle-derived magma may undergo lateral flow and emplacement through horizontal magma conduits; this occurs after magma from a deep source ascends through a vertical conduit. Regardless of this understanding, the characteristics of such shallow magma conduit systems remain unclear. We have developed an image of a shallow (5 km deep) magma conduit system based on the resistivity results of a high-power frequency-domain controlled-source electromagnetic survey in the Kalatongke magmatic-type Ni-Cu deposit. The magma upwelled and ascended along the vertical fault. At shallow depths, the magma moved horizontally along the tuff layer, laterally propagating in a horizontal magma conduit. Magma extending horizontally in the horizontal tuff layer could not break through the upper, conductive, and low-density carbonaceous layer. This image provides a conduit model with vertical magma ascent and lateral magma propagation. The model provides a basis for studying shallow magma conduit systems in orogenic belts on a global scale.

СТРОЕНИЕ ВОДОНОСНЫХ ГОРИЗОНТОВ ПО АНОМАЛИЯМ МАГНИТНОГО ПОЛЯ И СИЛЫ ТЯЖЕСТИ

The results of the study of the main characteristics and structural features of the aquifer systems of cold and thermal waters on the example of well-known sources in the Middle East are presented. The study of groundwater aquifers was carried out on the basis of the technology of geophysical data complex interpretation, taking into account the features of the aquifers geological structure. Aquifers and underground reservoirs are visualized as zones of reduced magnetization and density of rocks on deep petrophysical sections calculated from magnetic field and gravity anomalies. Horizontal subterranean water conduits can be clearly traced on the areal distributions of magnetization and density along the stretches of the lineaments with reduced values. Vertical subterranean water conduits stand out vividly on magnetic and density sections in the form of ascending tracks. As a result of the study of deep sections through the zones of known thermal springs, an estimate of the dependence of the source temperature on the depth of the feeding underground reservoirs was obtained. The article examines the potential of underground resources aquifers of the arid territories of Israel, the Kingdom of Saudi Arabia and the United Arab Emirates, for which the relevance of the water problem, apparently, will not decrease in the coming decades. The forecast of the location of groundwater karst reservoirs can be carried out by magnetic and density sections, taking into account two-dimensional models of the distribution of magnetization and density of rocks. The methodology of the study of aquifer systems is applicable to the analysis of underground resources of Africa and the Middle East arid regions.

The potential of Ojo de Valjunquera cave (NE of Iberia) sediments for paleoflood reconstructions

Speleothems and detrital deposits in caves are excellent archives of cave flood events but are still poorly exploited. In this study we evaluate, the potential of the Ojo de Valjunquera (Zaragoza, NE Spain) for the study of past floods based on geomorphological, topographical, hydrological, and chronological data. The cave comprises two subhorizontal levels. The lower level consists of a main horizontal conduit including six siphons. This level is connected to the upper one by shafts and ramps. That situation, together with the constrictions of the gallery in the lower level, favours the water rise during rainfall events. The upper level is characterized by a larger presence of speleothems and detrital sequences compared to the lower level. Current observations indicate that water can rise by ~9 m in some cave sectors during rainfall episodes >60 mm, although the hydraulic head rise is not homogeneous along the cave, depending on the section's morphology. The stalagmites and detrital sequences hosted in the upper gallery most likely contain evidence of extreme events of rainfall. However, geomorphological and sedimentological evidences also suggest that the cave outlet could have been blocked in the past by sediments, favouring the water rise to high places usually not affected by regular floods. The detrital sequences located in lower positions with respect to the cave entrance show a higher proportion of sandy sediments than those located in the higher sectors related to the water energy during the flood. Stalagmites show clean carbonate alternating with well-defined detrital layers. These detrital layers vary in thickness: the thinner ones are related to small floods, whereas the thicker ones are connected to large floods. Two important historical floods (1709 and 1755 CE) occurred in the area that coincide with distinct detrital layers recorded in the stalagmites. All these observations suggest that Ojo de Valjunquera cave contains an important paleoflood archive based on speleothems and detrital deposits during the Holocene.

Stratified flow distribution during gas–liquid downflow in the mesodomain

The paper discusses the formation and characteristics of stratified air–water downflow in the mesodomain. The stratified pattern, observed at low phase velocities, is characterized by air and water flowing side by side and both wetting the conduit wall, similar to stratified distributions in horizontal conduits. Such flow segregation without the influence of gravity is counterintuitive and no detailed investigation on the formation and flow physics of this distribution is reported till date. We have performed extensive experiments in glass conduits of 2.5–12.5 mm diameter where the two phases are introduced through T and Y junctions with different included angles between the entry arms. Our experiments reveal that stratified flows are formed up to a critical angle ϕc subtended by the edges of the circumferential liquid film and beyond the critical wetting angle, the flow pattern is annular with liquid completely wetting the conduit wall. We further note ϕc to depend on liquid properties, included angle of Y-entry, conduit diameter, and phase flow rates. Based on experimental observations, we propose a simplistic analysis to relate the liquid properties, conduit dimension, and Y-entry included angle and the liquid and gas flow rates to describe the formation of stratified and annular flow at the junction. The analysis also estimates the in situ void fraction during stratified gas–liquid downflow.

Magnetohydrodynamics Peristaltic Flow of a Couple- Stress for a Jeffrey Fluid through a Flexible Porous Medium

The topic of this paper is the peristaltic motion of a non-Newtonian Jeffrey fluid with couple stress across a porous medium inside a horizontal conduit. The unit is strained by a uniform magnetic field. It is taken into account the effects of viscous dissipation, internal heat generation, and radiation. This approach solves the equations of momentum, temperature, and velocity. The numerical formulas for axial velocity, temperature, and velocity are obtained as functions of the physical parameters of the problem. Numerical calculations, as well as the effects of temperature and magnetic field on the velocity equation, were conducted for this formula, and the results were shown on the channel wall. The results of the problem’s physical parameters on this formula are discussed numerically and graphically in a series of statistics.

Magnetohydrodynamics Peristaltic Flow of a Couple-Stress with Varying Temperature and concentrationfor Jeffrey Fluid through a Flexible Porous Medium


 The topic of this paper is the peristaltic motion of a non-Newtonian Jeffrey fluid with couple stress across a porous medium inside a horizontal conduit. The unit is strained by a uniform magnetic field. It is taken into account the effects of viscous dissipation, internal heat generation, and radiation. This approach solves the equations of momentum, temperature, and velocity. The numerical formulas for temperature, axial velocity, and velocity are calculated as functionsof the problem's physical parameters. Numerical calculations, as well as the effects of temperature and the inclined slanted magnetic field and concentration on the velocity equation, were conducted for this formula, and the results were shown on the channel wall. The results of the problem's physical parameters In a series of statistics, the effects of this formula are explained numerically and graphically.

Between droplets and fluid thread—the role of gravity in meso-scale flow

How gravity affects immiscible liquid co-flow is best illustrated through experiments in inclined conduits. In the macro-domain, gravity leads to flow stratification while in the microscale, the phase distribution is practically insensitive to conduit tilt. The influence of flow orientation in the intermediate scale conventionally known as meso-domain or milli-channel, although noted, has not been discussed earlier. In the present study, flow morphology is experimentally investigated during up, down, and horizontal co-flow of a biphasic liquid mixture in a glass conduit of diameter 2.38 mm. In all orientations, the dispersed phase flows either as droplets/plugs or as a continuous thread. Gravity modulates the process of thread pinch off and regulates the domain of thread/droplet flow. Apart from flow orientation, we also note entry arrangement to influence droplet detachment in horizontal conduit. The experimental observations are explained from a simplified analysis based on momentum and energy considerations; the defining parameters are fluid properties and flow rates, conduit dimension, and flow orientation. The proposed analysis, albeit the approximations, has successfully predicted thread pinch off for the present experiments. Pinch off from the thread tip is noted to be cyclic and comprises several steps, of which inception of necking to its completion is only a part.

Performance evaluation of partially filled high porosity metal foam configurations in a pipe

• Numerical simulation of partially filled metal foams for heat transfer augmentation is studied. • Darcy Forchheimer and Local Thermal Non-Equilibrium models for numerical modeling. • Six different strategies for maximum heat transfer and minimum pressure drop. • 10 to 45 pores per inch and 0.88 and 0.95 porosity are considered. • 30 pores per inch with porosity of 0.92 provides the best performance factor. In this contemporary research, a parametric analysis of partially filled high porosity metallic foams in a horizontal conduit is performed to augment heat transfer with reasonable pressure drop. The investigation includes six different models filled partly with aluminium foam by varying internal diameter of foams from the wall side and external diameter of foam from the core of the tube. The pore density of the foam ranges from 10 to 45 PPI and their porosity varies from 0.90 to 0.95. Flow dynamics are captured using Darcy Extended Forchheimer model for the porous filled region and two-equation turbulence k-ω model employed in clear region of the fluid. The local thermal non-equilibrium assumption is incorporated in porous filled region of the conduit to compute the heat transport characteristics. The results showed that the thermal performance factor of 10 PPI aluminium foam performs close to the 10 PPI expensive copper foam. The performance factor is found to be higher for 30 PPI aluminium foam amongst the PPI’s of the foam considered. However, the performance factor is found to be 2.93, 2.22 and 1.73 for 30PPI, 45 PPI and 20PPI with their porosities of 0.92, 0.90 and 0.90, respectively for the model 1, model 2 and model 3 at lower Reynolds number of 4500 and then it decreases progressively with increasing flow rates of the fluid. The results of average wall temperature, average Nusselt number and Colburn j factor are also evaluated to obtain best possible performance.

Convective stability of a permeable nanofluid inside a horizontal conduit: Fast chemical reactions

This problem considers the instabilities, which can occur when a horizontal sparsely filled nanofluid porous layer is saturated with a binary mixture with fast chemical reaction. The upper and lower plates are heated isothermally. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis. The modified Darcy equation that includes the time derivative term is used to model the momentum equation. The energy equation includes cross and regular diffusion conditions. In conjunction with the Brownian motion, the nanoparticle fraction becomes stratified; hence the viscosity and the conductivity are stratified. The nanofluid is assumed to be diluted and this enables the porous medium to be treated as a weakly heterogeneous medium with variation, in the vertical direction, of conductivity and viscosity. The oscillatory and stationary convection are evaluated analytically. The reaction rate is supposed to be greater than the diffusion rate. We find that both a stationary instability and an oscillatory instability can occur as the first bifurcation, depending on the sign and the value of the heat of reaction. The execution of the porous parameter, Prandtl number, Soret parameter, Dufour parameter, Lewis number, solutal Rayleigh number, chemical reaction and the modified diffusivity ratio parameters is implemented pictorially. It is found that the presence of nanoparticles the critical Rayleigh number is increased and helps to stabilize the system. The presence of chemical reaction parameter destabilizes the system. The results of previously-published work are also obtained as special cases of the general solution.

Assessment and Prediction of Air Entrainment and Geyser Formation in a Bottom Outlet: Field Observations and CFD Simulation

Air entrainment at the intake of a bottom outlet often gives rise to air pockets in its conduit and formation of geysers. The outlet in question comprises a bulkhead gate, gate shaft, horizontal conduit, and exit. Operations show that it suffers from appreciable flow fluctuations and blowouts in the tailwater, which leads to gate operation restrictions. For the purpose of understanding the hydraulic phenomenon, both prototype discharge tests and three-dimensional computational fluid dynamics (CFD) modeling of two-phase flows are performed. The operational focus of the facility are small and large gate openings. The CFD results reveal that, with air entrained in the gate shaft, continual breakup and coalescence of air bubbles in the conduit typify the flow. At small openings below 1 meter, the air–water flow is characterized by either distinct blowouts of regular frequency or continuous air release. In terms of geyser behaviors inclusive of frequency, the agreement is good between field and numerical studies. At large openings, the gate becomes fully submerged, and the flow is discharged without air entrainment and blowouts. The paper showcases the air–water flow features in a typical bottom outlet layout in Sweden, which is intended to serve as an illustration of the study procedure for other similar outlets.

Two-phase flow regimes of refrigerant R134a in an oscillating horizontal rectangular minichannel conduit

ABSTRACT In this study, refrigerant R134a experiments were carried out to observe two-phase flow in an oscillating horizontal rectangular minichannel conduit at refrigerant mass flux of approximately 30 kg•m − 2•s − 1 to 300 kg•m − 2•s − 1, saturation temperature of approximately 30 °C, and average vapor quality in the test section inlet of approximately 0.05 to 0.9. The test section was made from quartz and consists of a visible rectangular minichannel with a hydraulic diameter of 0.84 mm. The test section was oscillated vertically using a reciprocating motor. The effects of oscillation on slug and stratified flow patterns were investigated. The experimental observation was compared with an existing flow pattern map. The thin liquid film around the vapor of slug flow mostly moved up and down when the test section oscillated. As a result, a dry surface was not observed around the vapor due to the lower heat transfer coefficient. When the test section oscillated, the stratified flow changed to annular flow, and a dry surface was also not observed on the upper side of the minichannel conduit.

Effect of Particle Size and Surface Properties on the Sandbed Erosion with Water Flow in a Horizontal Pipe

Summary An experimental study was conducted to investigate the transport of sand particles over the sand bed deposited in a horizontal conduit by using turbulent flow of water. The main objectives were to determine the near-wall turbulence characteristics at the onset of bed erosion (i.e., near-wall velocity profile, Reynolds shear stresses, and axial-turbulent intensity); to determine critical velocity required for particle removal from the bed deposits; and more specifically, to determine how the sand-particle size and surface characteristics would influence the critical velocity required for the onset of bed erosion and the near-wall turbulence characteristics. A large-scale horizontal flow loop equipped with a nonintrusive laser-based particle-image velocimetry (PIV) system has been used for the experiments. The effect of sand-particle surface characteristics (i.e., wettability) on the critical velocity and the near-wall turbulence characteristics were investigated by using treated and untreated industrial sands of four different mesh sizes (i.e., 20/40, 30/50, 40/70, 100). The PIV technique was used to determine instantaneous local velocity distribution near the stationary sandbed fluid interface under subcritical and critical flow conditions. The near-wall velocity distribution measured directly at the sand bed/fluid interface together with the measured frictional pressure-loss values were then used for the evaluation of the Reynolds shear stresses and axial turbulent intensities acting at the bed/fluid interface. The results indicated that critical velocity for the onset of particle removal from sand beds increased with the increasing particle size. When sands with special surface treatment were used, it was observed that the critical velocity required for the onset of the bed erosion was significantly lower than that of required for the untreated sands. The degree of reduction in critical velocity varied between 14 and 40% depending on the particle size. In this study, by conducting experiments under controlled conditions, we provided much-needed fundamental data that can be used for the development of improved solid-transport design criteria and suitable mitigation technologies. In particular, we have shown the proof of concept that the surface-treated sand particles might have great potential for improving the transport efficiency of proppants used for hydraulic-fracturing operations.

Sub-synoptic circulation variability in the Himalayan extreme precipitation event during June 2013

This study investigates the sub-synoptic scale circulation aspects associated with the extreme rainfall event occurred over the North Indian state of Uttarakhand located in the western Himalayas (WH) during the 15–18 June 2013 period. A diagnosis based on hourly ERA5 reanalyzed circulation products archived on finer grids reveals that sustenance of heavy rains during the event period is supported by a propensity of cyclonic vorticity sources channeled toward the WH region through a narrow quasi-steady conduit in the lower troposphere from the ISM circulation. The equatorward segregating mesoscale potential vorticity (PV) structures from the quasi-stationary upper level PV anomaly (trough) during the event administered two pathways for vorticity sources. The first pathway is from the base of the trough culminating into longer horizontal conduit path from the western Arabian Sea, lending perpetual cyclonic vorticity support to the ISM environment. The second pathway is from the right flank of the trough, which promotes sustained environment of deeper mesoscale convergence zone, potentially unstable atmosphere and strong ascent over the Uttarakhand region. The convergence zone is potentially viewed as a region for strong monsoon and extratropical circulation interactions to occur on finer horizontal scales of motion, where significant vertical synchronization of positive PV advection is realized during the 16–17 June 2013 period. In addition to orographic precipitation enhancements, deeper advective synchronization noticed at sub-synoptic time periods is accredited to the nearly doubling 24-h rainfall amounts in the foothill region of Uttarakhand during the event period. The ERA5 diagnosed diabatic heating additionally indicates that precipitating systems at higher (foothill) elevations contribute to upper (lower) tropospheric heat sources.

Long-term In Situ Permeability Variations of an Active Fault Zone in the Interseismic Period

Hydraulic properties were estimated by analyzing the continuous water level response to Earth tides in a well intersecting the Qujiang active fault (in Yunnan, China) which had ruptured during the 1970 Tonghai Ms 7.8 earthquake. The in situ permeability from 2001 to 2018 fluctuates around 4 × 10−14 m2, with a variation of about 25%, and the hydraulic diffusivity varies from 0.29 to 0.55 m2/s. The permeability is comparable to the permeability estimated from the slug tests. According to the results, we suggest that the permeability in the damage zone of the Qujiang fault is dynamic, and the fault zone provides a localized horizontal conduit for the along-fault fluid flow. Furthermore, the shallow part of the Qujiang fault may heal incompletely or not heal after the Tonghai earthquake, and the fault may be stable between 2001 and 2018.

A numerical model in predicting the initial karst development in porous limestone

The numerical model proposed in this paper represents a new method in predicting initial karst spatial distribution of carbonate aquifers. Karstification Index, \( \varPhi_{\text{K}} \), is a measure of the possible largest amount of calcite that can be dissolved from a unit area of rock and transported by groundwater flow during a unit length of time. Mathematically, it is defined as \( \varPhi_{\text{K}} = q \cdot s \), where q is the flux of groundwater and s is the rock solubility; and Karstification Index, \( \varPhi_{\text{K}} \), is the function of flow, heat, and calcium concentration. The numerical model simulates the time- and space-dependent susceptibility to, and process of, karstification by iterative calculations between \( \varPhi_{\text{K}} \) and hydraulic conductivity. A sample calculation is presented on a hypothetical limestone plateau with steep escarpment, a spring, and a river on one side, a vertical no flow boundary on the other side, and a horizontal impermeable base. The rock has an equivalent porous-medium hydraulic conductivity of K = 5E−8 ms−1, which is characteristic to non-karstified limestone. Initially, the spring is located at the intersection of the water table and the escarpment’s face some distance above the river. The simulation result showed that the water table is lowered in 2325 years across the plateau, but the spring’s drop is stopped after 65 years. Karstification is most intensive along the water table due to the higher value of Karstification Index which resulted from the intensive flux of the water. The continual decline of the water table results in a laterally elongated and progressively expanding body of karstified rock and finally as a horizontal conduit at river level. The concentration of Ca2+ and conduit diameter decrease from the spring toward the impermeable vertical wall on the opposite side and downward to the base of the plateau. The results are consistent with general theories and empirical observations of karst and cave evolution.

Closure to “Water Hammer in a Horizontal Rectangular Conduit Containing Air-Water Two-Phase Slug Flow” by Amin Eyhavand-Koohzadi, Seyed M. Borghei, and Abdorreza Kabiri-Samani

Closure to “Water Hammer in a Horizontal Rectangular Conduit Containing Air-Water Two-Phase Slug Flow” by Amin Eyhavand-Koohzadi, Seyed M. Borghei, and Abdorreza Kabiri-Samani

Water Hammer in a Horizontal Rectangular Conduit Containing Air-Water Two-Phase Slug Flow

AbstractThe study of water hammer in air-water, two-phase flows in hydraulic structures such as pressurized pipelines and tunnels, siphons, culverts, and junctions is of great importance for design purposes. Water hammer if combined with a periodic slug flow would lead to severe periodic transient pressure fluctuations inside the conduit. Laboratory experiments have been conducted to investigate water-hammer pressure inside a horizontal rectangular conduit carrying a two-phase, air-water slug flow. Tests were performed in an experimental apparatus comprising a 6.8-m-long transparent pipeline 0.06 m wide and 0.1 m high. By rapidly closing a control gate at the end of the conduit, propagating pressure surges were generated. Transient pressure fluctuations were recorded by means of pressure transducers. Furthermore, a digital camera was used to document flow properties and air-bubble characteristics throughout the pipeline. Pressure measurements along the pipe indicated that two scenarios could be considered...

Experimental Study of Bleed Countermeasures for Post-Tensioning

During the grouting of post-tensioned structures, voids left by bleed water creates the risk of corrosion by aggressive agents on the prestressing steel. In this paper, the development of and countermeasures for bleed water are discussed. To improve the bleed performance of conduits, a combined rubber rod is proposed to form a compound-cross-sectional prestressing conduit. This conduit presents a unique approach to addressing bleed water, and its effectiveness at preventing bleed water was studied. A full-scale grouting comparative test was conducted based on the prototype of a Chinese high-speed railway 32 m simply-supported box girder. Based on these test results, the characteristics of the generation, transmission and distribution of bleed water in conduits were investigated, and the relationship between the bend-up height and grouting compactness percentage (GCP) was analyzed. The test results showed that compound-cross-sectional conduits can separate the voids created by bleed water from prestressing steel to protect the tendons from corrosion. For horizontal and bend-up conduits in post-tensioned structures, the compound-cross-sectional prestressing conduits had much better bleed performance than circular conduits.