Vertical Upward Direction Research Articles

Aerodynamic characteristics of wind turbines considering the inhomogeneity and periodic incentive of wake effects

In wind farms, the wake can lead to a loss of output power, and the uneven characteristics of wake can also exacerbate the fatigue load of downstream wind turbine (WT), affecting their operating life. To explore the impact of wake effects on downstream WT, this article proposes a new method for calculating the load of WT wake wind conditions and verifies it. Establishing a 3DJG wake model coupled with improved BEM for wind turbine aerodynamic performance calculation method. The influence of downstream WT operation phase angle and positions of 3D wake on the time-varying aerodynamic characteristics of downstream WTs was discussed from three perspectives: Blade elements on the spanwise, single blade and wind rotor. Results shown that: (1) For the blade element, calculated the shear force in the flapwise direction and the edgewise direction on each blade segment. The overall shear force of blade element in the vertical upward direction of WT blades is significantly greater than that in other directions. The non-uniformity of the wake is not sufficient to change the position of the maximum shear force on the blade. The position of the maximum shear force at each wake position is in the rear segments of the blade; (2) For the single blade, the most severe load fluctuation occurs when it is in the partial wake condition. The period of this fluctuation is 360°. When in full wake condition, the load fluctuation is relatively small, and due to the symmetry of the wake, the load fluctuation period is only 180°. The load standard deviation (SD) of the partial wake condition increases by 51 % compared to the full wake condition. (3) For the wind rotor, different wake positions have a weighty impact on the power loss of the WT rotor. Compared to the incoming shear wind, the power loss at the wake center can reach up to 54.22 %. At the wake boundary, the power loss of the WT is only 5.6 %. The non-uniformity of wake also has a periodic impact on the power output of the entire WT rotor, with the fluctuation period is 120°, and the fluctuation amplitude of no more than 2 %. This article provides a more intuitive quantitative analysis of the impact of wake on the time-varying aerodynamic characteristics of downstream WTs. It has certain reference value for the design strength verification of WTs, as well as the yaw strategy and layout design of wind farms.

Numerical simulation of transient boiling and void cross flow in non-uniformly heated 5 × 5 rod bundle

A multi-dimensional numerical simulation has been conducted for a transient boiling experiment by applying rapid and non-uniform power to fluid in a 5×5 bundle channel simulated a BWR fuel assembly in atmospheric pressure. The experiment is to investigate thermal hydraulic behavior in applying transient power to subcooled reactor coolant in a stand-by mode of a nuclear power plant such as reactivity initiated accident (RIA). The numerical simulation has been conducted by TRACE (version 5.0 / patch 5) which is a nuclear system analysis code to solve thermal hydraulics of boiling two phase flow by a two fluid model. The bundle channel in the upward vertical direction has been simulated by a three dimensional component with the Cartesian coordinate system attaching heat structures to simulate heating rods for thermal conduction and heat transfer calculation. It has been revealed that the numerical result is possible to simulate the void cross flow through the sub-channel in the bundle channel qualitatively as observed in the experiment. However, there was room for improvement for a wall heat transfer model in TRACE because the numerical result is larger than the experimental result in terms of the rising rate of the rod temperature during the rapid initial increasing of applied power, and it has been inferred that the evaluation model for an onset of nucleate boiling in TRACE also has to be improved because the void initiation time in the numerical result was earlier than the experimental result. Therefore, TRACE has been optimized by modifying the two physical models described above. The numerical results with the modified TRACE have been in better agreement with the experimental results than those with the original TRACE. Using the modified TRACE, a numerical experiment has been conducted putting an inlet velocity and subcooling of fluid and applied power as parameters in addition to the experimental conditions. The results have shown that there is a square law correlation between a void cross flow and applied power to the fluid. The experiments and analyses in this study have elucidated the behavior of transient boiling two phase flow in a fuel assembly of a nuclear power plant at the transient event such as RIA.

합기도 술기 칼넣기 동작의 운동학적 분석

The purpose of this study is to conduct a kinematic comparative analysis of the hapkido skill Kalnugki motion. To this end, an infrared high-speed camera were used for motion analysis. The Kwon3d program was used for the analysis of kinematic variables. Additionally, an independent t-test was conducted to verify the differences between the skilled and the unskilled, and this time, the statistical significance level was set at .05. The results were as follows. First, the time required for the completion of the Sulki and Kalnugki techniques was short for those skilled in Hapkido. Second, there was no difference in the movement of the COM(center of mass) by event for both the skilled and unskilled. Third, there was no difference in the left/right and forward/backward velocities of the COM during demonstrations of Sulki and Kalnugki between the skilled and unskilled. In event 2, the vertical velocity of the COM in the vertical upward direction was faster in the skilled. Fourth, there was no difference in the hip joint, and ankle joint angles. However, in event 2 and 3 of the right knee joint angle, skilled showed smaller angles than unskilled, and for left knee joint angles in event 1 and 2, skilled showed smaller angles than unskilled.

Cuantificación del efecto del movimiento vertical del paciente durante la gated-SPECT de perfusión miocárdica sobre los índices de perfusión y de función del ventrículo izquierdo

ObjectiveTo assess the effect of software-simulated «bouncing» motion on left ventricle (LV) perfusion and function indices concerning 3main determinants of motion (duration, magnitude and time) by evaluating the sole effect and interaction of these attributes in a statistical model. MethodsTwenty-nine gated myocardial perfusion SPECT scans were selected for the study and then, «bounce» motion pattern was simulated manually regarding 3main attributes of motion including duration (short versus long), magnitude (2 versus 4 pixels) and time (early versus late), all in upward vertical direction. All SPECT images are reconstructed and filtered with an identical method (OSEM algorithm) and same parameters. Indices of LV myocardial perfusion and function are derived using QGS package of Cedars-Sinai software in original and simulated-motion images and are then compared with each other. Two- and 3-way repeated measure within-subjects ANOVA tests are conducted to evaluate the main effect of each variable or attribute and the interaction between them. ResultsSummed scores increase roughly exponentially from «no motion» to short bounce and then, to long bounce. In long 4-pixel bounce, perfusion defects are remarkable. All comparisons of defect extent and total perfusion deficit are statistically significant. Mean difference between short bounce motion patterns with «no motion» is small even in 4-pixel movements (almost 3% or lower). In contrast, mean difference between long bounce motion patterns with «no motion» is higher than 5%. Using a paired-sample t test, in all pairs, mean difference for ejection fraction is less than 4% which all are statistically significant. Value of end-diastolic volume and end-systolic volume are consistently decreased based on duration (from short to long) and magnitude (from 2 to 4 pixels). Using within-subjects ANOVAs, in long bounce, main effect of magnitude and interaction of magnitude and time, but not time solely, were statistically significant. In 2-pixel magnitude, none of variables and their interaction were significant, but in 4-pixel magnitude, EF showed statistical significance with duration. ConclusionThe perfusion parameters are to a higher extent involved by motion particularly in long bounce with a 4-pixel displacement. In short bounce, the effect is negligible, and therefore, no need to repeat the scan. Parameters of function are much less vulnerable to be affected by motion. Thus, contrary to current recommendations, there may be less need to repeat the scan in short 2-pixel bounce.

Quantifying the effect of vertical motion of patient during gated myocardial perfusion SPECT on indices of perfusion and function of left ventricle

ObjectiveTo assess the effect of software-simulated “bouncing” motion on left ventricle (LV) perfusion and function indices concerning three main determinants of motion (duration, magnitude and time) by evaluating the sole effect and interaction of these attributes in a statistical model. MethodsTwenty-nine gated myocardial perfusion SPECT scans were selected for the study and then, “bounce” motion pattern was simulated manually regarding three main attributes of motion including duration (short versus long), magnitude (2 versus 4 pixels) and time (early versus late), all in upward vertical direction. All SPECT images are reconstructed and filtered with an identical method (OSEM algorithm) and same parameters. Indices of LV myocardial perfusion and function are derived using QGS package of Cedars-Sinai software in original and simulated-motion images and are then compared with each other. Two- and three-way Repeated Measure Within-Subjects ANOVA tests are conducted to evaluate the main effect of each variable or attribute and the interaction between them. ResultsSummed scores increase roughly exponentially from “no motion” to short bounce and then, to long bounce. In long 4-pixel bounce, perfusion defects are remarkable. All comparisons of defect extent (DE) and total perfusion deficit (TPD) are statistically significant. Mean difference between short bounce motion patterns with “no motion” is small even in 4-pixel movements (almost 3% or lower). In contrast, mean difference between long bounce motion patterns with “no motion” is higher than 5%. Using a paired-sample t-test, in all pairs, mean difference for ejection fraction (EF) is less than 4% which all are statistically significant. Value of end-diastolic volume (EDV) and end-systolic volume (ESV) are consistently decreased based on duration (from short to long) and magnitude (from 2 to 4 pixels). Using Within-Subjects ANOVAs, in long bounce, main effect of magnitude and interaction of magnitude and time, but not time solely, were statistically significant. In 2-pixel magnitude, none of variables and their interaction were significant, but in 4-pixel magnitude, EF showed statistical significance with duration. ConclusionThe perfusion parameters are to a higher extent involved by motion particularly in long bounce with a 4-pixel displacement. In short bounce, the effect is negligible, and therefore, no need to repeat the scan. Parameters of function are much less vulnerable to be affected by motion. Thus, contrary to current recommendations, there may be less need to repeat the scan in short 2-pixel bounce.

Granular column collapse: Analysis of inter-particle friction effects

The purpose of this paper is to investigate the effects of inter-particle friction on the granular column collapses via the discrete element method (DEM) while eliminating the particle-size effects. As the inter-particle friction increases, the runout distance decreases, the deposit height increases, the force chains tend to be closer to the vertical upward direction, the percentage of the strong force chains become greater and the granular assembly is less susceptible to the external gravity field, thus making the collapse tend to be toppling-dominant flow. The correlation between the initial height and runout distance of particles at the final deposits becomes stronger when the collapse tends to be more toppling-dominant. The motion patterns of the collapse are governed by the inter-particle friction and initial aspect ratio through dimensional analysis and the effective aspect ratio parameter is proposed to classify granular column collapse into three regimes (sliding-dominant, transition, and toppling-dominant collapse).

The influence of sedimentary heterogeneity on the diffusion of radionuclides in the sandy facies of Opalinus Clay at the field scale

Abstract. Radionuclide migration in clay-rich formations is typically dominated by diffusion considering the low permeability of these formations. An accurate estimation of radionuclide migration in host rocks using numerical tools plays a key role in the safety assessment of disposal concepts for nuclear waste. In the sandy facies of the Opalinus Clay (SF-OPA), the spatial variability of the pore space network and compositional heterogeneity at the pore scale (nm to µm) cause heterogeneous diffusion at the core scale (cm to dm). Such heterogeneous diffusion patterns affect the migration of radionuclides in various sedimentary layers even above the core scale (m). In this work, we study the heterogeneous diffusion of cations based on a two-dimensional (2D) structural model at the m-scale. As key parameters for the diffusive transport calculation, the effective diffusion coefficients in different sedimentary layers are quantified based on our previous developed up-scaling workflow from pore- to core-scale simulation combined with the multi-scale digital rock models. The heterogeneous effective diffusivities are then implemented into the large-scale structural model for diffusive transport simulation using the FEM-based OpenGeoSys-6 simulator. The sensitivity analysis focuses on the effects of the SF-OPA bedding angle and the effect of different layer-succession layout with different canister emplacement on the spatio-temporal evolution of radionuclide diffusion front line. Results show that the moving distance of the diffusion front is farther away from the canister center, along the direction with the neighboring layer having lower diffusion coefficient within the total simulation time of 2000 years. When the bedding angle increases, the diffusion front moves farther in in vertical upward direction direction, which has less retardation effect for the radionuclide from the ground surface point. For different layer-succession layout with different canister emplacement, the smallest migration distance of the diffusion front line is 1.65 m. Within 2000 years, for the conceptual model 2B that the canister is emplaced in the layer with the highest diffusivity coefficient, the diffusion front can migrate 0.19 m farther along vertical downward direction due to the influence of the neighboring layer. The numerical results provide insight into the effects of rocks heterogeneity on diffusion of radionuclides, contributing to enhanced long-term predictability of radionuclide migration in SF-OPA as potential host rock for a deep geological repository.

Heat transfer of flow boiling carbon dioxide in vertical upward direction

Heat transfer measurements of flow boiling Carbon Dioxide (CO2) in vertical upward direction have been carried out with a dedicated test facility at the European Organization for Nuclear Research (CERN). The investigation covers saturation temperatures within a range of −25∘C≤Tsat≤+5∘C, mass velocities from 100kgm−2s−1≤G≤450kgm−2s−1 and heat fluxes of 5.3kWm−2 and 11.4kWm−2. The experiments have been conducted in a vertical upward evaporator of 8 mm inner diameter and 8 m length and a database of more than 1900 measurements has been compiled within the present study. The heat transfer mechanism is dominated by the nucleate boiling contribution and dryout is observed as a function of saturation temperature, mass velocity and heat flux. A correlation is proposed to predict the dryout inception within the experimental range where the onset of dryout has been observed. The results suggest that most commonly used heat transfer prediction models underpredict the heat transfer mechanisms of CO2. Moreover, the heat transfer coefficients of CO2 increase in vertical upward direction, compared to the data of horizontal studies. For that reason, a vertical multiplier is suggested to capture the trends of vertical upflow with two existing prediction models.

국가대표 에어로빅 체조선수의 Pike Jump 동작에 대한 운동학적 분석

The purpose of this study was to analyze the kinematics of the aerobic gymnastics Pike jump motion. This study analyzed the kinematic variables such as duration time, COM(center of mass) displacement and velocity, and body segment angle, and the following conclusions were drawn. First, the duration time of the Pike jump motion was long in the order of P1, P4, P2, and P3. And the total duration time was 1.73±0.09 s. Second, during the Pike jump, the COM left and right displacements did not show any significant change, and the COM front and rear displacements moved the most in the forward direction in P1, the jumping phase. And the vertical displacement of the COM moved vertically down in P1, vertically up in P2 and P3, and moved vertically down in P4 again. Third, during the Pike jump, the COM left and right velocity showed the left and right velocity in the left direction except for E1 for jumping. The COM front and rear velocity showed the fastest velocity in E1, and showed a slow velocity as the movement progressed. And the COM vertical velocity showed the velocity in the vertical downward direction in E1, E4, and E5, and the velocity in the vertical upward direction in E2 and E3. Fourth, it was found that both hip joints performed flexion in P1, extension in P2, flexion in P3, and extension in P4 during the Pike jump operation. The angle of both knee joints was found to be flexed in P1, extended in P2, and flexed again in P3 and P4, and the angles of both ankle joints were flexion in P1, extension in P2, It was found that flexion exercise was performed in the P3 and P4.

Spatial distribution of particulate matter 2.5 released from surface fuel combustion of Pinus koraiensis – A laboratory simulation study

High concentration particulate matter 2.5 released from forest fires, in addition to direct burns and asphyxia, PM2.5 is one of the main pollutants which threaten the safety of forest fire fighter. Therefore, to assess spatial distribution of PM2.5, a simulation study was conducted. Fuel beds with different moisture contents and loads were constructed. 144 times burning experiments were carried out under different wind speeds by using wind tunnel device. PM2.5 particles at different spatial points were collected and calculated. The results show that, in the two of three variables interaction between wind speed, fuel load, and, except fuel moisture content, wind speed and fuel load are positively correlated with the PM2.5 concentrations. From PM2.5 concentration which collected at each point in the horizontal and vertical directions, the overall trend is that PM2.5 concentration increases along the horizontal downwind direction (C and D higer than A and B) and the vertical upward direction (A and C higer than B and D) Based on BP neural network, the spatial distribution model of PM2.5 concentration with single hidden layer was established. The prediction accuracy of modeling samples and validation samples is balanced when hidden layer node is 5. This study will help to make reference for PM2.5 occupational exposure standards, forest fire smoke management and forest fire management in China.

Non-similar mixed convection analysis for magnetic flow of second-grade nanofluid over a vertically stretching sheet

The aspiration of this research is to explore the impact of non-similar modeling for mixed convection in magnetized second-grade nanofluid flow. The flow is initiated by the stretching of a sheet at an exponential rate in the upward vertical direction. The buoyancy effects in terms of temperature and concentration differences are inserted in the -momentum equation. The aspects of heat and mass transfer are studied using dimensionless thermophoresis, Schmidt and Brownian motion parameters. The governing coupled partial differential system (PDEs) is remodeled into coupled non-similar nonlinear PDEs by introducing non-similar transformations. The numerical analysis for the dimensionless non-similar partial differential system is performed using a local non-similarity method via bvp4c. Finally, the quantitative effects of emerging dimensionless quantities on the non-dimensional velocity, temperature and mass concentration in the boundary layer are conferred graphically, and inferences are drawn that important quantities of interest are substantially affected by these parameters. It is concluded that non-similar modeling, in contrast to similar models, is more general and more accurate in convection studies in the presence of buoyancy effects for second-grade non-Newtonian fluids.

Forming characteristics and mechanism of double-sided heat source synergic vertical welding on an aluminum alloy

Top-quality aluminum alloy weld beads, exploiting the double-sided heat source synergic welding (DSHSSW) process, were obtained with medium heat input, no arc spacing, no root gap, and upward vertical direction. The energy utilization was reduced with the augmented arc spacing because of the attendant increased heat dissipation. Compared with one-side welding (OSW), the fusion area and melting efficiency of DSHSSW were enormously raised, indicating the enhancement of melting performance and energy utilization, and superior joints could be fabricated using DSHSSW under the identical heat input. Additionally, the DSHSSW arc was constricted and thus improved the energy density in contrast to OSW. As the weld penetration deepened during DSHSSW, the heat conduction space was diminished, and the heat accumulation effect was generated. The arc contraction and heat accumulation effect mutually lead to the increased penetrating ability during DSHSSW.

골볼 터닝 드로우 동작의 운동역학적 분석

The purpose of this study is to analyze the kinematics of the goal ball turning throwing motion, and the conclusions are as follows. First, the total time for goal ball turning and throwing motion was 1.82 s, 76.95 % in P1 and 23.02 % in P2. Second, it was found that the COM (center of mass) left and right displacement of the goalball turning throwing motion moved leftward from P1 (E1~E2) and moved to the right from P2 (E2~E3). COM forward and backwark displacement Moved to the forward according to the progress of the event. COM vertical displacement moved downward according to the progress of the event. Third, the COM left and right velocities of the goal ball turning throwing motion showed the fastest velocity from E3 to the right, and the COM forward and backward velocities showed the fastest speed from E2 to the forward. COM vertical velocity showed the fastest downward velocity at E2. Fourth, when the goal ball turning throwing motion was released, the velocity of the ball was 12.00±0.88 ㎧, and the stride width was 1.09±0.12 m. Fifth, the body segment’s angular momentum at the time of release of the goal ball turning throwing motion was found to be the largest in the trunk. And the upper arm, forearm, and hand segment of the upper limb all showed greater angular momentum than the left. In the case of the lower extremities, the right thigh and foot segments showed greater angular momentum than the left, but the left shank segment showed greater angular momentum than the right. Sixth, when the goal ball turning throwing motion was released, the ground reaction force of the forefoot showed the force in the right direction, the rear direction, and the vertical upward direction, and at this time, the large force was in the order of Fz, Fy, and Fx.

Multi-DOF (Degree of Freedom) Articulating Laparoscopic Instrument is an Effective Device in Performing Challenging Sutures.

PurposeAlthough laparoscopic surgery had been performed in clinical practice for over 30 years, there has not been much improvement on instruments. Several articulating laparoscopic instruments have been developed including the robotic system. A new multi-degree of freedom (DOF) articulating laparoscopic device has been developed. We compared the ability to perform challenging sutures between the new device and the robotic system.MethodsFive experienced surgeons with over 100 laparoscopic surgery cases performed the suture task with both instruments. Everyone was new at articulating instruments including a robotic system. The suturing task consisted of two vertical sutures, downward and upward vertical direction. The duration of needle grabbing, first surgical tie, square tie, and the final reverse tie was measured.ResultsWhen doing the downward suture, the median time to complete the suture was 127 vs. 136 seconds for ArtiSential® and the robot, respectively (p=0.754). Other measurements such as needle grabbing, first tie, second tie and final knot did not show any significant difference between the two instruments. Upward suture also did not show a significant difference. The total completion time was 127 vs. 112 seconds for for ArtiSential® and the robot, respectively (p=0.675). Time taken in each interval did not show any significant difference.ConclusionBoth instruments performed the suturing tasks with no difference in duration. ArtiSential® can be mixed up with usual instruments. Surgeons can choose any device, but when articulation is needed, ArtiSential® could be an alternative choice to the robotic system.

Micropolar meets Newtonian. The Rayleigh–Bénard problem

We consider the Rayleigh–Bénard problem for the two-dimensional Boussinesq system for the micropolar fluid. Our main goal is to compare the value of the critical Rayleigh number, and estimates of the Nusselt number and the fractal dimension of the global attractor with those values for the same problem for the classical Navier–Stokes system. Our estimates reveal the stabilizing effects of micropolarity in comparison with the homogeneous Navier–Stokes fluid. In particular, the critical Rayleigh number for the micropolar model is larger than that for the Navier–Stokes one, and large micropolar viscosity may even prevent the averaged heat transport in the upward vertical direction. The estimate of the fractal dimension of the global attractor for the considered problem is better than that for the same problem for the Navier–Stokes system. Besides, we obtain also other results which relate the heat convection in the micropolar fluids to the Newtonian ones, among them, relations between the Nusselt number and the energy dissipation rate and upper semicontinuous convergence of global attractors to the Rayleigh–Bénard attractor for the considered model.

Design of solar huts

This problem is a solar hut photovoltaic cell in the attached and overhead two installation methods, the type of photovoltaic cells and array mode and inverter type optimization design issues. In question 1, since the photovoltaic cells are attached to the roof and exterior surfaces, the direction and angle of the battery are uniquely determined by the direction and angle of the attached surface. The problem is translated to optimize the installation of a certain type on a single surface area (array) of photovoltaic cells, so that the total amount of solar photovoltaic power generation as much as possible, and the unit power generation costs as small as possible, which is a multi-objective optimization problem. The problem can be discussed in the ideal environment in a single surface area of the battery installation optimization program, and then the actual environment of the multi-surface optimization. In the solution to Problem 1, the unit on the south of the roof of the battery at the moment to accept the solar energy formula is generated. The definition of and is the moment of direct radiation intensity, for the moment the sun and the south of the roof of the plane where the angle, for the level of horizontal radiation intensity, for the south of the roof and the horizontal angle, the planefor the plane, the center of the heart, the vertical upward direction is the axis of the positive coordinate system, obtained with the sun height angle , the sun azimuth , red angle, angle and the sun when the relationship is generated. The conclusion is only installed in the small roof surface type of battery C11, and the rest of the surface is not installed. 35 years of electricity generation is 77126 degrees, the economic benefits of 16,488 yuan, the recovery period of 21.3 years. In question 2, because the photovoltaic cells in the roof and the external wall surface can be installed overhead, the panel orientation and tilt will affect the efficiency of photovoltaic cells. Therefore, in the optimization scheme of Problem 1, the orientation and inclination of the panel on each surface are further adjusted to calculate the optimum orientation and inclination of the panel on each surface. The problem can be in the ideal weather environment to establish the sun running and the battery board efficiency model, and then the measured environment test. The optimal orientation of the panel is southward, and the optimal angle with the ground plane is 39.89 degrees. The conclusion is only installed in the small roof surface type of battery C11, and the rest of the surface is not installed. 35 years of generating capacity of 82165.2 degrees, the economic benefits of 18,998 yuan, the recovery period of 13 years. In question 3, by the optimization of the above two issues, in the building to meet the requirements of the hut under the design of the various aspects of the cabin and battery installation, and further optimize the total power generation of the hut, economic benefits. The whole model solver is run in MATLAB7.0.

Adiabatic two-phase gas–liquid flow behaviors during upward flow in a vertical circular micro-channel

A two-phase air–water flow experiment was carried out to obtain flow pattern, void fraction, and pressure drop data from a vertical micro-channel, which was a fused silica tube with a diameter of 0.53mm and a length of 320mm. The adiabatic two-phase flow behaviors during vertical upward direction were experimentally investigated, and consequently, a buoyancy effect can be detected in this work. A flow visualization study was performed, leading to observation of slug flow, throat–annular flow, churn flow, annular flow, and annular–rivulet flow. The shape of the interfacial surface in the slug flow pattern was deformed during vertical upward flow, which was different from the bullet-shaped gas slug observed in the horizontal channel. The flow visualization results also indicate that the flow pattern map for vertical upward flow is not completely compatible with that for horizontal flow. Image analysis was performed to determine the void fraction, which increases linearly with increasing volumetric quality. The vertical upward flow gave a lower void fraction than the horizontal flow. The frictional pressure drop can be increased when the churn flow is formed in the channel. In addition, vertical upward flow can result in higher pressure drop when compared with the horizontal channel.

Pilot-scale evaluation of an in situ amendment delivery and mixing device for contaminated sediment remediation applications

In situ sediment treatment technologies can be more economical alternatives than dredging and ex situ treatment; however, their development and application had been hindered due to uncertainties associated with the homogeneity of amendment delivery and mixing and the concern of contaminated sediment resuspension and amendment release into the water column. The purpose of this study was to evaluate the subaqueous amendment delivery and mixing efficiency of a novel pilot scale in situ sediment remediation system addressing these concerns. The in situ sediment treatment system consisted of a hydraulically operated steel casing that provided contained conditions for amendment delivery and mixing to occur and the mixing tool housed by this casing. The mixing tool consisted of a hollow vertical shaft with horizontal mixing blades. The device was capable of delivering amendments to subaqueous sediments during continuous mixing in the downward or upward vertical direction. Activated carbon was used as a tracer to evaluate the efficiency of reagent delivery and mixing. The delivery and mixing system operation was defined by the following parameters: mixing speed, vertical descent or ascent speed, mixing time, total processing time, sediment mixing depth, activated carbon slurry injection volume, pumping flow rate for activated carbon, and pumping pressure for activated carbon. Better amendment yield recoveries were observed at lower added activated carbon volumes, at higher mixing speeds, at lower pump flow rates, in case of thicker mixed sediment zones, and at horizontal locations closer to the center shaft. In general, poor amendment recoveries could be attributed to the limited capacity of the sediment pore space to accommodate the activated carbon slurry. Better recoveries close to the shaft might have occurred due to the fact that the amendment delivery pressure was not controlled and therefore was not constant through each reagent delivery port. The reagent stayed within the enclosure of the device, indicating that contained mixing conditions were achieved. The majority of the suspended sediment settled out fairly quickly from the overlying water column within the enclosure. The in situ remediation system showed potential in terms of successful amendment delivery and mixing into subaqueous sediments. Lower doses of activated carbon were mixed in more efficiently due to the limited availability of pore capacity and issues with powdered activated carbon retention in the sediment. The demonstration took place in sediments with large sand and gravel fractions; sediments containing larger silt and clay fractions are likely to behave differently in terms of sediment resuspension.

Diffusion-Thermo and Radiation Effects on Unsteady MHD Flow Through Porous Medium Past an Impulsively Started Infinite Vertical Plate with Variable Temperature and Mass Diffusion

The objective of this study is to investigate diffusion-thermo (Dufour effect) and radiation effects on unsteady MHD free convection flow past an impulsively started infinite vertical plate with variable temperature and uniform mass diffusion in the presence of transverse applied magnetic field through porous medium. At time t > 0, the plate is given an impulsive motion with constant velocity u0 in the vertical upward direction against to the gravitational field. At the same time, the plate temperature is raised linearly with time t and the level of concentration near the plate is raised to \({{C}_{\rm w}^{\prime}}\). A magnetic field of uniform strength B0 is applied normal to the direction to the flow. The dimensionless governing equations are solved in closed form by Laplace transform technique. The effect of flow parameters on velocity, temperature, concentration, the rate of heat transfer and the rate of mass transfer are shown through graphs.

Numerical study of eccentric core-annular flow

A numerical study (taking into account inertial -, viscous - and pressure forces) has been made of eccentric core-annular flow through a horizontal pipe, special attention being paid to the vertical force on the core. The viscosity of the core is assumed to be so large that it behaves as a rigid solid. A wave is present at its surface. The shape of the wave is based on experimental results published earlier in the open literature. Due to the eccentricity the centre line of the core is shifted in the upward vertical direction with respect to the centre line of the tube. The vertical force on the core was found to be dependent on the Reynolds number: at small values of the Reynolds number the force is in the upward vertical direction, at large values the force is downward. This means that at large values of the Reynolds number an upward buoyancy force on the core due to a density difference between core and annulus can be counterbalanced. So a stationary core-annular flow is then possible.