scholarly journals Study on Permeability Characteristics of Porous Transparent Gels Based on Synthetic Materials

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 4009
Author(s):  
Gaoliang Tao ◽  
Qingshi Luo ◽  
Shaoping Huang ◽  
Yi Li ◽  
Zhe Huang ◽  
...  
Keyword(s):  
Porous Polymer ◽  
Migration Behavior ◽  
Pressure Gradients ◽  
Low Velocity ◽  
Permeability Characteristics ◽  
Synthetic Materials ◽  
Image Velocimetry ◽  
New Type ◽  
Transparent Gels ◽  
Advanced Knowledge

Advanced knowledge of the permeability characteristics of transparent gels play a key role in providing a rational basis for the study of porous polymer permeability and the research on the migration behavior of superpolymer solutions. Thus, a new type of transparent gel was prepared to simulate porous media, with aim to observe and analyze the permeability characteristics of transparent gel under the conditions of our experimental design by combining a transparent soil test and simple particle image velocimetry. The experimental results showed that the permeability of the transparent gel was similar to that through actual soil. The permeability coefficients of the transparent gel under different pressure gradients varied greatly early in the experimental cycle, while changing only slightly afterward, showing an overall trend of decreasing first and then stabilizing. With the increase of the mass ratio, the permeability coefficient of the sample decreased, the distribution of the low-velocity zone of the intercepted section became wider and tended to move upward. Differences in spatial position also caused different patterns of velocity and direction. The findings presented in this paper contribute to providing a new direction for the study of porous polymer permeability and the porous migration of superpolymer solutions.

scholarly journals Cosmic-Ray Driven Outflows to Mpc Scales from L* Galaxies

2020 ◽  
Author(s):  
Philip F Hopkins ◽  
T K Chan ◽  
Suoqing Ji ◽  
Cameron B Hummels ◽  
Dušan Kereš ◽  
...  
Keyword(s):  
Cosmic Ray ◽  
Plane Layer ◽  
Equilibrium Density ◽  
Pressure Gradients ◽  
Low Velocity ◽  
Star Forming ◽  
Stellar Feedback ◽  
Massive Halos ◽  
Halo Masses

Abstract We study the effects of cosmic rays (CRs) on outflows from star-forming galaxies in the circum and inter-galactic medium (CGM/IGM), in high-resolution, fully-cosmological FIRE-2 simulations (accounting for mechanical and radiative stellar feedback, magnetic fields, anisotropic conduction/viscosity/CR diffusion and streaming, and CR losses). We showed previously that massive (Mhalo ≳ 1011 M⊙), low-redshift (z ≲ 1 − 2) halos can have CR pressure dominate over thermal CGM pressure and balance gravity, giving rise to a cooler CGM with an equilibrium density profile. This dramatically alters outflows. Absent CRs, high gas thermal pressure in massive halos “traps” galactic outflows near the disk, so they recycle. With CRs injected in supernovae as modeled here, the low-pressure halo allows “escape” and CR pressure gradients continuously accelerate this material well into the IGM in “fast” outflows, while lower-density gas at large radii is accelerated in-situ into “slow” outflows that extend to >Mpc scales. CGM/IGM outflow morphologies are radically altered: they become mostly volume-filling (with inflow in a thin mid-plane layer) and coherently biconical from the disk to >Mpc. The CR-driven outflows are primarily cool (T ∼ 105 K) and low-velocity. All of these effects weaken and eventually vanish at lower halo masses (≲ 1011 M⊙) or higher redshifts (z ≳ 1 − 2), reflecting the ratio of CR to thermal+gravitational pressure in the outer halo. We present a simple analytic model which explains all of the above phenomena. We caution that these predictions may depend on uncertain CR transport physics.

scholarly journals Study of the Effect of a Plug with Torsion Channels on the Mixing Time in a Continuous Casting Ladle Water Model

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1942
Author(s):  
Gerardo Aguilar ◽  
Gildardo Solorio-Diaz ◽  
Alicia Aguilar-Corona ◽  
José Angel Ramos-Banderas ◽  
Constantin A. Hernández ◽  
...  
Keyword(s):  
Continuous Casting ◽  
Mixing Time ◽  
Tangential Velocity ◽  
Water Model ◽  
Mixing Times ◽  
Low Velocity ◽  
Velocity Magnitude ◽  
Image Velocimetry ◽  
Casting Ladle ◽  
Upward Direction

The use of porous plugs in injecting gas through the bottom of a ladle forms vertical plumes in a very similar way to a truncated cone. The gas plume when exiting the plug has a smaller diameter compared to that formed in the upper zone of the ladle because inertial forces predominate over buoyancy forces in this zone. In addition, the magnitude of the plume velocity is concentrated in an upward direction, which increases the likelihood of low velocity zones forming near the bottom of the ladle, especially in lower corners. In this work, a plug with spiral-shaped channels with different torsion angles is proposed, with the objective that the gas, when passing through them, has a tangential velocity gain or that the velocity magnitude is distributed in the three axes and does not just focus on the upward direction, helping to decrease low velocity zones near the bottom of the ladle for better mixing times. For the experimentation, we worked in a continuous casting ladle water model with two configuration injections, which in previous works were reported as the most efficient in mixing the steel in this ladle. The results obtained using the PIV technique (particle image velocimetry) and conductimetry technique indicate that the plugs with the torsion channels at angles of 60° and 120° improve the mixing times for the two injection configurations.

Rotor Boundary Layer Response to an Impinging Wake

Volume 1 ◽  
2004 ◽  
Author(s):  
Francesco Soranna ◽  
Yi-Chih Chow ◽  
Oguz Uzol ◽  
Joseph Katz
Keyword(s):  
Boundary Layer ◽  
Guide Vane ◽  
Suction Side ◽  
Velocity Profiles ◽  
Inlet Guide Vane ◽  
Pressure Gradients ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Image Velocimetry ◽  
Entire Flow

This paper presents results of an experimental investigation on the response of a rotor boundary layer to an impinging Inlet Guide Vane (IGV) wake. High resolution two-dimensional Particle Image Velocimetry (PIV) measurements are conducted in a refractive index matched facility that provides an unobstructed view of the entire flow field. Data obtained at four different rotor phases, as the wake is chopped and passes by the rotor blade, allows us to examine the response of the rotor boundary layer to the mean flow and turbulence associated with the impinging wake. We focus on the suction side boundary layer in regions with adverse pressure gradients, from mid chord to the trailing edge. The phase-averaged velocity profiles are used for calculating the momentum and displacement thicknesses of the boundary layer, and for estimating the pressure gradients along the wall. Distributions of Reynolds stresses are also provided. The phase-averaged velocity profiles in the rotor boundary layer vary significantly with phase. During wake impingement the boundary layer becomes significantly thinner and more stable compared to other phases at the same location. Analysis of the possible causes for this trend suggests that the dominant contributors are unsteady, phase-dependent variation in pressure gradients along the wall.

Optimization of a columnar vortex generator installed over an aircraft carrier ski-jump ramp

2019 ◽  
Vol 234 (1) ◽  
pp. 223-230
Author(s):  
Rafael Bardera
Keyword(s):  
Vortex Generator ◽  
Wind Tunnel Testing ◽  
Low Velocity ◽  
Aircraft Carrier ◽  
Recirculation Bubble ◽  
Columnar Vortex ◽  
Flow Disturbances ◽  
Image Velocimetry ◽  
Field Velocity ◽  
Flight Deck

Aircraft performances over aircraft carriers are essential in modern navies. Take-off operation is critical due to the short runway available. The ski-jump ramp is a useful system that allows to operate under safe conditions. However, the sharp edge at the end of the runway provokes a region with recirculation bubble and low velocity producing strong flow disturbances. Hence, the aircraft performances are affected and the pilot’s workload is augmented. Previous researches showed that columnar vortex generator reduces the recirculation bubble generated over the end of flight deck. This article presents an in-depth experimental study performed by wind tunnel testing in order to determine the relation between the columnar vortex generator size and the recirculation bubble reduction. Particle image velocimetry is used to investigate the flow field velocity and flow structure around the ski-jump ramp as a non-intrusive experimental technique. Encouraging results were found for the biggest columnar vortex generator studied.

Crosswell seismic imaging in a contaminated basalt aquifer

Geophysics ◽  
2004 ◽  
Vol 69 (1) ◽  
pp. 16-24 ◽  
Author(s):  
Thomas M. Daley ◽  
Ernest L. Majer ◽  
John E. Peterson
Keyword(s):  
Seismic Source ◽  
P Wave ◽  
Low Velocity ◽  
S Waves ◽  
High Attenuation ◽  
Well Spacing ◽  
Simultaneous Acquisition ◽  
Environmental Laboratory ◽  
New Type ◽  
Borehole Seismic

Multiple seismic crosswell surveys have been acquired and analyzed in a fractured basalt aquifer at Idaho National Engineering and Environmental Laboratory. Most of these surveys used a high‐frequency (1000–10,000 Hz) piezoelectric seismic source to obtain P‐wave velocity tomograms. The P‐wave velocities range from less than 3200 m/s to more than 5000 m/s. Additionally, a new type of borehole seismic source was deployed as part of the subsurface characterization program at this contaminated groundwater site. This source, known as an orbital vibrator, allows simultaneous acquisition of P‐ and S‐waves at frequencies of 100 to 400 Hz, and acquisition over larger distances. The velocity tomograms show a relationship to contaminant transport in the groundwater; zones of high contaminant concentration are coincident with zones of low velocity and high attenuation and are interpreted to be fracture zones at the boundaries between basalt flows. The orbital vibrator data show high Vp/Vs values, from 1.8 to 2.8. In spite of the lower resolution of orbital vibrator data, these data were sufficient for constraining hydrologic models at this site while achieving imaging over large interwell distances. The combination of piezoelectric data for closer well spacing and orbital vibrator data for larger well spacings has provided optimal imaging capability and has been instrumental in our understanding of the site aquifer's hydrologic properties and its scale of heterogeneity.

Multi-Laboratory Uncertainty Analysis of PIV-Measured Flow Quantities Relevant to Blood Damage in the FDA Nozzle Model

2011 ◽  
Author(s):  
Prasanna Hariharan ◽  
Matthew Giarra ◽  
Varun Reddy ◽  
Steven W. Day ◽  
Keefe B. Manning ◽  
...  
Keyword(s):  
Heart Valves ◽  
Shear Stresses ◽  
Low Velocity ◽  
Blood Damage ◽  
Flow Parameters ◽  
Image Velocimetry ◽  
Artificial Heart Valves ◽  
Post Market ◽  
Regulatory Submissions ◽  
Measured Flow

Particle image velocimetry (PIV) has been used in regulatory submissions to the FDA for pre-clinical and post-market evaluations of flow fields in medical devices, such as artificial heart valves, blood pumps, and stents. The velocity and shear fields obtained from the PIV experiments are also used to validate computational fluid dynamics (CFD) data accompanying the submissions. However, previous studies have questioned the accuracy of PIV measurements in regions of high shear and low velocity (regions prone to hemolysis and thrombosis). Currently, there is no clear estimate of the amount of uncertainty involved in measuring various flow parameters in these high-risk regions. The objective of this study was to perform an inter-laboratory PIV study in a simplified nozzle model and quantify the uncertainties involved in measuring flow quantities relevant to blood damage, such as near-wall velocity, viscous and Reynolds shear stresses, size and velocity within recirculation regions, and for estimating an index of hemolysis.

Boundary Layer Separation Control on a Flat Plate With Adverse Pressure Gradients Using Vortex Generators

2006 ◽  
Author(s):  
Edward Canepa ◽  
Davide Lengani ◽  
Francesca Satta ◽  
Ennio Spano ◽  
Marina Ubaldi ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Particle Image Velocimetry ◽  
Flat Plate ◽  
Particle Image ◽  
Boundary Layer Separation ◽  
Vortex Generators ◽  
Separation Control ◽  
Pressure Gradients ◽  
Layer Separation ◽  
Image Velocimetry

The continuous tendency in modern aeroengine gas turbines towards reduction of blade count and ducts length may lead to aerodynamic loading increase beyond the limit of boundary layer separation. For this reason boundary layer separation control methods, up to now mostly employed in external aerodynamics, begin to be experimented in internal flows applications. The present paper reports the results of a detailed experimental study on low profile vortex generators used to control boundary layer separation on a large-scale flat plate with prescribed adverse pressure gradients. Inlet turbulent boundary layer conditions and pressure gradients are representative of aggressive turbine intermediate ducts. This activity is part of a joint European research program on Aggressive Intermediate Duct Aerodynamics (AIDA). The pressure gradients on the flat plate are generated by increasing the aperture angle of a movable wall opposite to the flat plate. To avoid separation on the movable wall, boundary layer suction is applied on it. Complementary measurements (surface static pressure distributions, surface flow visualizations by means of wall mounted tufts, instantaneous and time-averaged velocity fields in the meridional and cross-stream planes by means of Particle Image Velocimetry) have been used to survey the flow with and without vortex generators. Three different pressure gradients, which induce turbulent separation in absence of boundary layer control, were tested. Vortex generators height and location effects on separation reduction and pressure recovery increase were investigated. For the most effective VGs configurations detailed analyses of the flow field were performed, that demonstrate the effectiveness of this passive control device to control separation in diffusing ducts. Particle Image Velocimetry vector and vorticity plots illustrate the mechanisms by which the vortex generators transfer momentum towards the surface, re-energizing the near-wall flow and preserving the boundary layer from separation.

Characteristics of Turbulent Flows Over Forward Facing Steps in Adverse Pressure Gradients Based on Two-Point Analyses

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Hassan Iftekhar ◽  
Martin Agelin-Chaab
Keyword(s):  
Particle Image Velocimetry ◽  
Turbulent Flows ◽  
Coherent Structures ◽  
Particle Image ◽  
Adverse Pressure Gradient ◽  
Pressure Gradients ◽  
Physical Size ◽  
Piv Technique ◽  
Image Velocimetry ◽  
Point Velocity

This study reports the results of turbulent flows forward facing steps (FFS) in pressure gradients using a particle image velocimetry (PIV) technique to obtain data up to 68 step heights downstream. The contours of two-point velocity correlations indicate that regardless of the pressure gradients, the physical size of the coherent structures characterized by the autocorrelations grows as the flow develops downstream along the step. Additionally, adverse pressure gradient (APG) elevates the size of the autocorrelations.

Study of the airflow induced by a sliding discharge plasma actuator

2019 ◽  
Vol 33 (02) ◽  
pp. 1950011
Author(s):  
Hao Dong ◽  
Zheng Li ◽  
Xi Geng ◽  
Zhiwei Shi ◽  
Qijie Sun
Keyword(s):  
Electrical Discharge ◽  
Particle Image ◽  
Discharge Plasma ◽  
Active Flow Control ◽  
Plasma Actuator ◽  
Ac Power ◽  
Image Velocimetry ◽  
New Type ◽  
Active Flow ◽  
Sliding Discharge

Sliding discharge, as a new type of electrical discharge, is being gradually applied in plasma active flow control in recent years. In this work, the particle image velocimetry (PIV) experiments were conducted to investigate the airflow characteristics induced by the sliding discharge plasma actuator at varied voltage signals. The results show that the integral thrust produced by the negative alternating current (AC) power is stronger than normal AC power under the same voltage magnitude. The induced airflow direction changes along with the changing of two power voltage signals. Furthermore, the angle of the induced airflow is mainly linear with the loading voltage.

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