Streamline Flow Research Articles

EXPERIMENTAL INVESTIGATION OF EFFERVESCENT ATOMIZATION, PART II: INTERNAL FLOW AND SPRAY CHARACTERIZATION WITH NOVEL DARPA SUBOFF AFTERBODY STREAMLINE AERATOR

EXPERIMENTAL INVESTIGATION OF EFFERVESCENT ATOMIZATION, PART II: INTERNAL FLOW AND SPRAY CHARACTERIZATION WITH NOVEL DARPA SUBOFF AFTERBODY STREAMLINE AERATOR

ANALYSIS OF ONE-WAY STREAMLINE FLOW BETWEEN PARALLEL PLATES VIA ROHIT INTEGRAL TRANSFORM

This paper illustrates the application of the Rohit integral transform for analyzing the one-way streamline flow between parallel plates directly without finding the general solution of a differential equation relating to the flow characteristic equation of the viscous liquid. Viscosity is the characteristic of a fluid (liquid) due to which viscous force becomes active when the fluid is in motion. This force opposes the relative motion of different layers of the fluid. This viscous force becomes active when the different layers of the fluid are operating with different velocities which leads to shearing stress between the layers of the operating fluid. In this paper, Rohit integral transform is applied for solving the differential equation relating flow characteristics of the viscous liquid to obtain the velocity distribution and shear stress distribution of a one-way streamline flow between the stationary parallel plates as well as between the parallel plates having a relative motion

Numerical Investigation of an Fe3O4 Nanofluid Filled in an Obround Enclosure Heated by Solar Energy

This research work deals with a technological application of a 2D numerical solar Magneto-Hydro-Dynamic (MHD) investigation of an Fe3O4-Water nanofluid, filled in an obround-shaped enclosure. The cold temperature is imposed on a symmetric arc wall located at the semicircular side of the enclosure, while the hot temperature is related to a circular rotating heat source located in the middle of the enclosure. The remaining walls of the enclosure are supposed to be insulated. The cold wall is considered chilled using a solar refrigeration system. The heat source is considered as a blackbody receiving solar radiation. The mathematical problem, stating the governing equations of the considered MHD problem (continuity equation, Navier Stokes equations and energy conservation equation), is elaborated in its dimension and dimensionless form. The dimensionless form permits to generalize dimensionally the considered problem. The considered problem Numerical results, stating the influences of geometrical, magnetic and Fe3O4-Water nanofluid operating parameters on the flow (streamlines and velocity magnitudes) and thermal behaviors of the Fe3O4-Water nanofluid (temperature contours) are presented, discussed and interpreted. The geometrical parameters are the wall arc angle, the heat source velocity, and the radius. The magnetic parameters are the Hartmann number and the magnetic field inclination angle. The Fe3O4-Water nanofluid operating parameters are principally the Rayleigh number.

Effect of paragliding wing dome shape on its aerodynamic characteristics

Double-membrane gliding parachutes (DGP) obtain their wide variety of application, including the solution of cargo transportation problems. This parachute is a flexible canopy, which shape is maintained by ram air. In terms of the aerodynamic performance calculation and analysis when operating, DGP is the most complex aero elastic system. The computation of DPG aerodynamic performance is only possible, utilizing the methods of nonlinear aerodynamics and the nonlinear theory of elasticity methods.This paper investigates the aerodynamic characteristics of stable geometric shapes for various gliding parachutes, taking into account their dome shape both chord-wise and span-wise. Notably, the volumetric parachute profile is modeled by its median surface. The research, conducted by the authors, showed that such an aero elastic model of DGP allows you to obtain results that reflect correctly the qualitative effects of detached and free streamline flow. To solve the problem about the airflow over a gliding parachute, considering its canopy curvature, the method of discrete vortices with closed frames is employed, which allows you to calculate the paragliding wing aerodynamic performance within a wide range of angles of attack. There is also a possibility of flow separation simulation. The ideal incompressible liquid flow over the median surface of a stable shape for a double-membrane gliding parachute is regarded. The parachute fabric porosity is not analyzed, since the upper and lower DGP panels are made of either the low permeable or non-porous fabric. In the separated flow past, the aerodynamic coefficients are identified by time averaging to its large values after computing. The DGP aerodynamic performance computation results are given at a different value of its dome shape, as in the free streamline flow as in the flow separation. The computed coefficients, that allow us to consider the influence of canopy dome shape on its aerodynamic characteristics, are obtained. The proposed technique can be used for operational estimates of aerodynamic forces while designing and planning a pipe experiment.

Finite element method in thermal characterization and streamline flow analysis of electromagnetic silver-magnesium oxide nanofluid inside grooved enclosure

Employing magnetic effect, behavior of heat and fluidity of hybrid nanofluid based on the mixed water of magnesium oxide and silver is explored in the present work on the permeable and hollow ampoule. Inertia of penetrable layer is obtained by employing Darcy Forchheimer model especially and efficient thermos-physical model. Effective Galerkin Finite Element Analysis (GFEM) is executed to solve the governing equations of model. 10−6 error tolerance was used to examine the results. Impacts of isotherms and streamlines were marked by performing the parametrical analysis of important and effective constraints. Except the influencing constraints of the flow, there is a prominent effect of twisting ampoule structure on fluidity. This effect can be seen in the developed contours in the plots of streamlines. Heat diffusion is made away from the wall with the initial values of Rayleigh number (Ra) as well as Darcy number (Da), mainly from the hotter side of the wall that have two structures of cliff bar. Except the increment in Hartmann number (Ha) and low Rayleigh number (Ra), increment is observed in heat transfer rate with many constraints.

A metamaterial-free fluid-flow cloak.

The model of ideal fluid flow around a cylindrical obstacle exhibits a long-established physical picture, where originally straight streamlines are deflected over the whole space by the obstacle. Inspired by transformation optics and metamaterials, recent theories have proposed the concept of fluid cloaking, which is able to recover the straight streamlines, as if the obstacle did not exist. However, such a cloak, similar to all previous transformation-optics-based devices, relies on complex metamaterials with inhomogeneous parameters and is difficult to implement. Here we deploy the theory of scattering cancellation and report on the experimental realization of a fluid-flow cloak without metamaterials. This cloak is realized by engineering the geometry of the fluid channel, which effectively cancels the dipole-like scattering of the obstacle. The cloaking effect is demonstrated through the direct observation of recovered straight streamlines in the fluid flow. Our work sheds new light on conventional fluid control and may find application in microfluidic devices.

Buckling capacity of composite panels with cutouts using continuous curvilinear fibres and stiffeners based on streamlines

In this paper a novel concept is proposed for improving the buckling capacity of composite aircraft panels with cutouts. The key idea is to adopt the streamlines of a fluid flow around a given body of arbitrary shape that represents the cutout to define both the fibre and stiffener trajectories. As such, fibres and stiffeners can curve around the cutout in a continuous fashion which may improve the structural performance of panels. The buckling performance of typical aircraft panels with cutouts is addressed. Circular cutouts with various sizes as well as elliptical ones with different sizes and alignments are considered. Unstiffened, longitudinally stiffened and grid-stiffened panels subjected to in-plane uniaxial compressive and shear loads are investigated. The critical buckling loads obtained using curvilinear fibres and stiffeners are compared with those obtained for conventional panels with straight fibres and stiffeners. It is shown that up to 30% improvement in the buckling performance of the unstiffened panels can be achieved. For the stiffened panels, replacing the straight-line format by a streamline format for the fibres and stiffeners yields tremendous improvements in the buckling capacity. The improvements may exceed 150% and 200% for longitudinally stiffened panels and grid-stiffened panels, respectively.

Effect of Emissary Vein on Hemodynamics of the Transverse- Sigmoid Sinus Junction.

Objective: To investigate the effect of the blood flow direction and afflux location of emissary veins (EVs) on the hemodynamics of the transverse-sigmoid sinus (TS-SS) junction.Methods: A patient-specific geometric model was constructed using computed tomography venography (CTV) and 4D flow MR data from a venous pulsatile tinnitus (PT) patient. New EV models were assembled with the afflux at the superior, middle and inferior portions of the SS from the original model, and inlet and outlet directions were applied. Computational fluid dynamics (CFD) simulation was performed to analyze the wall pressure and flow pattern of the TS-SS junction in each condition.Results: Compared to the model without EVs, the wall pressure was greatly increased in models with inlet flow and greatly decreased in models with outlet flow. The more closely the EV approached the TS-SS, the larger the pressure in models with inlet flow, and the smaller the pressure in models with outlet flow. The flow streamline in the lateral part of the TS-SS junction was smooth in all models. The streamlines in the medial part were regular spirals in outlet models and chaotic in inlet models. The streamlines showed no obvious changes regardless of afflux location. The velocity at the TS-SS junction of inlet models were uniform, medium-low flow rate, while in control and outlet models were the lateral high flow rate and the central low flow rate.Conclusion: The flow direction and afflux location of EVs affect the hemodynamics of the TS-SS junction, which may influence the severity of PT.

Numerical Analysis of Gravitational Vortex Chamber

A rotating mass of fluid is known as vortex and the motion of the rotating mass of fluid is known as vortex motion. Vorticity is the circulation per unit area. In this research simulation of a vortex chamber is to be carried out in ANSYS CFD taking water as fluid domain for generating a water vortex that is capable enough to move a turbine for electricity generation. The CAD modelling of the setup was set down and simulation was done in fine mesh by taking suitable wall function in the model of a cylindrical chamber along with a rectangular channel with a contraction portion at the end of it where good amount of vortex generation was acquired by observing velocity and pressure by setting different parameters. The results shows the pressure and velocity contours with 3D velocity streamline flow and the curve of the velocity and pressure curve shows the decrease of pressure and increase of velocity from inlet to outlet that leads to a decent vortex generation.

Abstract 1122‐000142: Safety and Efficacy of Surpass Streamline for Intracranial Aneurysms: A Multicenter US Real‐World Experience (SESSIA)

Introduction : Flow diversion has established itself as standard treatment of wide complex intracranial aneurysms (IA). Its recognition has been validated with positive occlusion rates and favorable clinical outcomes. The Surpass Streamline (SS) flow diverter (FD) is a braided cobalt/chromium alloy implant with 72 or 96 wires approved by the FDA in 2018. The aim of this study is to determine the safety and efficacy of the SS in a post‐marketing large US cohort. Methods : We performed a multicenter, retrospective study for consecutive patients treated with the SS FD for IA between January 2018 and June 2021 in the United States. Inclusion criteria for participants were: 1. Adults (≥ 18 years) and 2. Treatment with SS FD for IA. Primary safety end point was a major ipsilateral stroke (increase in National Institutes of Health Stroke Scale Score of ≥ 4) or neurological death within 12 months. Primary efficacy was assessed using the 3‐point Raymond‐Roy (RR) occlusion scale on digital subtraction angiography (DSA) at 6‐12‐month follow‐up. Results : A total of 276 patients with 313 aneurysms were enrolled. The median age was 59 years and 199 (72%) were females. The most common comorbidities included hypertension in 156 (57%) subjects followed by hyperlipidemia in 76 (28%) patients. One hundred and twenty‐two (44%) patients were asymptomatic while subarachnoid hemorrhage was present in only 10 (4%) patients. A total of 143 (46%) aneurysms were left‐sided. Aneurysms were located as follows: 274 (88%) were in the anterior circulation with paraophthalmic being the most common in 120 (38%) followed by petrocavernous ICA in 81 (26%); 33 (11%) aneurysms were located in the posterior circulation with basilar trunk being the most common in 14 (5%). The mean maximum aneurysm dome width was 5.77 ± 4.7 mm, neck width 4.22 ± 3.8 mm and dome to neck ratio was 1.63 ± 1.3 mm. The mean number of SS FD implanted per aneurysm was 1.06 (range 1–3) with more than one SS FD implanted in 21 (7%) aneurysms. Modified Rankin Scale (mRS) of 0–2 was present in 206/213 (97%) patients at 6–12 month follow‐up. The complete aneurysm occlusion (RR 1) rate was 145/175 (83%) among subjects who had angiographic follow‐up at 6–12 months. Major stroke and death was encountered in 7 (2%) and 5 (1.8%) of the patients respectively. Conclusions : Our data represent the largest real‐world study using SS FD. These results corroborate its post‐marketing safety and efficacy for the treatment of intracranial aneurysms showing more favorable rates to the initial experience during SCENT trial.

Flow analysis of a front opening unified pod (FOUP) subjected to different fan filter unit (FFU) coverage area in mini-environment

Moisture contamination control has been adopted in many wafer handling and storage processes. In portable wafer carriers called front opening unified pods (FOUPs), the current industry-accepted methods of moisture control are gas purging and laminar air curtain (LAC). Both typically use purified clean dry air (CDA). In this study, we investigated five different methods of FOUP moisture control: conventional and diffuser-based purging, LAC, and combinations of each purging method with LAC. Two different scenarios of 100% and 75% FFU coverage area were examined. The FOUP was empty and its internal volume was exposed to a mock-up mini-environment (ME)–a process confinement device used in semiconductor fabs. Also, the LAC was mounted inside the ME above the FOUP opening. Smoke flow visualization, particle image velocimetry (PIV) and humidity measurement were performed in the FOUP median plane. Streamline flow patterns were obtained from the PIV results that can significantly enhance the evaluation of the moisture removal performance of different case studies. The findings showed that the combination of diffuser purge and LAC was the most resistant against external lateral moist air flow wherein it yielded the lowest average humidity. The findings could be beneficial for reducing waste and increasing product quality in semiconductor manufacturing. This can lead to significant reductions in energy usage and drastically reduce manufacturing costs.

Linear and nonlinear fluid flow responses of connected fractures subject to shearing under constant normal load and constant normal stiffness boundary conditions

Linear and nonlinear fluid flow behaviors of connected fractures during shearing under constant normal load and constant normal stiffness boundary conditions are numerically characterized solving the Navier-Stokes equations. The model consists of three fractures having an identical length of 200 mm and a width of 100 mm, among which the bridge fracture is sheared. Both smooth and rough-walled fracture surfaces are generated to investigate the effect of surface roughness on flow streamline distributions and the ratio of flow rate to hydraulic gradient. The results show that the permeability monotonically increases during shearing under constant normal load conditions, due to the shear-induced dilation of fractures. Under constant normal stiffness conditions, the permeability either increases or decreases during shearing, controlled by the competing role played by the shearing fracture and nearby fractures. As shear advances, the shearing fracture dilates and increases the permeability, whereas the surrounding fractures are compressed that decrease the permeability. The flow rate of rough-walled models is overestimated by approximately 45 ∼ 80% comparing to the smooth parallel plate model. For smooth models, the critical hydraulic gradient dramatically decreases with increasing the shear strain from 0.015 to 0.025 and then slightly fluctuates with the increment of shear strain from 0.025 to 0.05. The critical hydraulic gradient monotonically decreases during the shearing process for rough-walled models. The range of critical hydraulic gradient is between 0.001 and 0.02.

Simultaneous PIV/LIF-PIV measurements and numerical simulation of liquid flow and ambient gas flow for transient diesel spray

The characteristics of spray/ambient gas flow and the turbulent mixing process significantly influence the subsequent combustion feature. There are some related studies on the simultaneous measurement of spray liquid/gas phase flow using optical diagnosis techniques. However, the two-phase flow characteristics of the transient Diesel spray have not been discussed in detail, few works have verified the measuring accuracy of the methods. This study proposes a PIV/LIF-PIV measuring method for simultaneously investigating the liquid/gas flow of transient Diesel spray. The experimental process and effects of imaging parameters/digital image processing method on the measuring accuracy are discussed based on the detectability of cross-correlation peak. The characteristics of the local turbulent mixing of liquid/gas flow for Diesel spray are presented. Numerical simulation using the Large-Eddy Simulation (LES) Eulerian-Lagrangian method is also carried out for extending the understanding regarding the liquid/gas phase flow process. The results indicate that the upstream vortex structures of spray flow lead to the random direction of velocity vectors at the tip, which is related to the shot-by-shot variation of spray structure at early timing after SOI. A similar streamline of spray flow and ambient gas flow could be observed in the spray region especially at 2.0 ms ASOI, which implies the gaseous phase is accelerated rapidly by the internal spray droplets as soon as entering the spray boundary, and both phases reach a “balanced state” at the end of the injection period. Similar results could be derived from the simulation results, the position where the maximum spray velocity exists is quite different because of the randomness of the instantaneous flow. An improved quasi-dimensional velocity predicting model that accounts for the spatial variation of velocity distribution is also developed.

Experimental and numerical investigations on the local wall heat transfer coefficient in a narrow packed bed with spheres

Packed beds are used at the laboratory scales to model and understand the phenomena of water flow through soil and rocks. The behaviour of local wall heat transfer coefficient with randomised packing of mono-dispersed spheres is examined in the present study. Under steady-state conditions, the high-resolution local wall temperature data is obtained by placing the infrared (IR) camera in close proximity to the test section. The local wall heat transfer coefficient is computed using the measured bulk fluid temperature, local wall temperature data and applied heat flux. Physical and numerical experiments were conducted for the narrow bed to particle diameter ratio of 1.25 using random packing of mono-dispersed (impermeable) glass spheres (diameter 6 mm) in order to be able to recreate similar geometry for numerical simulations of fluid flow and heat transfer. An attempt is made for recreation of the experimental narrow bed geometry by using the technique of method of gaps and computational fluid dynamics simulations were performed. The results of simulations are presented in appropriate velocity vectorial plots and flow stream lines revealing complex 3D mixing patterns inside void spaces of the narrow bed. Local variations of wall heat transfer coefficient are found along the packed bed and the numerical simulations of fluid flow and heat transfer reveal interesting complex flow patterns inside the bed.

Concentric ballooned catheterization to the fractional non-newtonian hybrid nano blood flow through a stenosed aneurysmal artery with heat transfer

The current work analyzes the effects of concentric ballooned catheterization and heat transfer on the hybrid nano blood flow through diseased arterial segment having both stenosis and aneurysm along its boundary. A fractional second-grade fluid model is considered which describes the non-Newtonian characteristics of the blood. Governing equations are linearized under mild stenosis and mild aneurysm assumptions. Precise articulations for various important flow characteristics such as heat transfer, hemodynamic velocity, wall shear stress, and resistance impedance are attained. Graphical portrayals for the impact of the significant parameters on the flow attributes have been devised. The streamlines of blood flow have been examined as well. The present finding is useful for drug conveyance system and biomedicines.

Buckling and postbuckling performance of composite fuselage panels with cutouts using continuous streamline fibres

In this paper the buckling and postbuckling behaviour of variable-stiffness composite fuselage panels with window openings based on streamline fibres is addressed. Streamlines of a fluid flow around a given body that represents the cutout are adopted to define the fibre trajectories that curve around the cutout in a continuous fashion. Plates and shells with circular and elliptical cutouts subjected to compressive and shear loads are investigated. Various design scenarios using different laminate layups are considered. As a first step, an optimum stacking sequence is obtained for maximum buckling capacity. Then, a postbuckling analysis is performed to evaluate the initial postbuckling stiffness that represents the strength of the laminates beyond buckling. The buckling and postbuckling performance of panels with streamline fibres is compared with that obtained for traditional panels with straight fibres. It is shown that significant improvements in the buckling capacity can be achieved using streamline fibres instead of straight ones. Moreover, laminates with streamline fibres optimized for maximum buckling loads exhibit a higher postbuckling strength than do the laminates with straight fibres.

Numerical Simulations of Heat Transfer Phenomena through a Baffled Rectangular Channel

In presence of baffle, the turbulent airflow phenomena as well as forced convective heat exchange characteristics in two-dimensional rectangular channel have been analyzed in this work. For variations in Reynolds number (Re), we have studied the variations in characteristics of thermal behavior due to the change in the shape of baffle. Computations have been done using finite volume method (FVM) and FLUENT software and the SIMPLE algorithm has been employed for solving the governing equations. Finally, the flow and thermal exchange characteristics viz., streamline flow, turbulence intensity (TE), axial velocity, turbulence kinetic energy (TKE), normalized friction factor (F), normalized average Nusselt number (Nuavg) and thermal enhancement factor (TEF) have been studied in details from numerical standpoint. It has been found that the triangular shaped baffle provides highest value of F at Re = 30,000 and at Re = 46, 000, the maximum value of the TEF is found for the same baffle implying that triangular shaped baffle is more suitable for overall purposes.

Waves in a coherent two-dimensional flow

A condensate in two-dimensional turbulence confined to a finite domain was predicted by Kraichnan. The most common spatial form of the condensate is a coherent vortex of radius comparable with the domain size, which is statistically steady over times much longer than its turnover time. The vortices were successively studied during the last four decades, and their time-averaged properties were recently and extensively considered in theory and measured in experiments. Here, we consider weak perturbations of the coherent flow in the vortices. Our interest lies in slow perturbations, which implies that they are homogeneous along the streamlines of the coherent flow. We show that such kind of perturbations can be considered as waves of condensate propagating in the radial direction with some dispersion law. In the present work, the dispersion law and the propagation length of the waves are found as a function of the radial position inside a vortex flow. Cases of condensate saturated due to bottom friction and of viscous condensate are different. In the first case, there are waves with low damping. In the second case, all waves are of a similar kind as the shear waves in an unsteady laminar boundary layer.

Numerical study of natural convection of nanofluids in an inclined flat bottom flask using finite-volume approach.

In this work, we study numerically the natural convection of nanofluids (NF) in an inclined flat bottom flask; it is one of laboratory flasks used in organic chemistry synthesis. The main reason of this study is to enhance the thermal properties of the reaction medium inside the flat bottom flask and to ameliorate the rate of chemical reactions using nanofluids. The flat bottom wall is maintained at a constant high temperature Th. While the top, left and right walls of the cavity are maintained at a low temperature TL. The NF comprises Cu and Al2O3 nanoparticles (NP) suspended in pure water. The governing equations are solved numerically using the finite-volume approach and formulated using the Boussinesq approximation. In this simulation we examined the effects of the NP volume fraction (φ) from 0% to 5%, the Rayleigh number from 103 to 106, the various inclination angles of enclosure (γ=0°,5°,10°, 15°) and the NF type (Cu and Al2O3) on the flow streamlines, isotherm distribution and Nusselt number. The obtained results show that the addition of Cu and Al2O3 NP increases the mean Nusselt number which enhances the heat transfer in the flat bottom flask and causes significant changes in the flow pattern. In addition, the mean Nusselt number is increase with increasing the Rayleigh number and the volume fraction and the best results have obtained from the Cu nanofluide. Also, as the inclination angle increases the mean Nusselt number decreases and the highest value of Nusselt number was obtained for a vertical enclosure (γ=0°). The obtained streamlines are mostly symmetric and their values are generally increase by increasing the Rayleigh number and volume fractions of NPs. Besides, the obtained isotherms are generally follow the geometry of the flat bottom flask.

Effects of oil channels and oil flow rate on cooling performance of closed circuit axial piston transmission

Closed circuit axial piston transmission (CCAPT) has been implemented in the field of hydraulic transmission. As a result of frictional loss and leakage loss, the temperature rise is unavoidable, that can shorten the service life of crucial components. Based on the method of computational fluid dynamics and liquid-solid mathematical coupling, structure optimization of CCAPT is investigated in the paper to decrease temperature. The influence of the position of oil inlet and outlet channels, oil flow rate and the filling-oil channels type is analyzed, meanwhile the temperature distribution and flow streamline are monitored. The results indicate that the higher inlet velocity may give rise to a better cooling performance of CCAPT but there is an optimal upper limit of inlet velocity, which is 3.5 m/s in this study. Besides, cooling performance and reducing temperature are obvious when oil inlet and outlet channels are set close to both sides of CCAPT. In addition, axisymmetric filling-oil channels have a slightly better effect on cooling performance but the cooling performance is not obvious. The paper can provide design reference for reasonable selection of oil channels and oil flow rate.