scholarly journals Structural Stability of Optofluidic Nanostructures in Flow-Through Operation

Micromachines ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 373 ◽  
Author(s):  
Yazan Bdour ◽  
Juan Gomez-Cruz ◽  
Carlos Escobedo
Keyword(s):  
Structural Stability ◽  
Optical Sensors ◽  
Theoretical Models ◽  
Effective Area ◽  
Support Surface ◽  
Structural Failure ◽  
Nanohole Array ◽  
Periodic Arrays ◽  
Flow Through ◽  
Experimental Values

Optofluidic sensors based on periodic arrays of subwavelength apertures that support surface plasmon resonance can be employed as both optical sensors and nanofluidic structures. In flow-through operation, the nanoapertures experience pressure differences across the substrate in which they are fabricated, which imposes the risk for structural failure. This work presents an investigation of the deflection and structural stability of nanohole array-based optofluidic sensors operating in flow-through mode. The analysis was approached using experiments, simulations via finite element method, and established theoretical models. The results depict that certain areas of the sensor deflect under pressure, with some regions suffering high mechanical stress. The offset in the deflection values between theoretical models and actual experimental values is overturned when only the effective area of the substrate, of 450 µm, is considered. Experimental, theoretical, and simulation results suggest that the periodic nanostructures can safely operate under trans-membrane pressures of up to 20 psi, which induce deflections of up to ~20 μm.

Nanohole Arrays as Optical and Fluidic Elements for Sensing

2008 ◽  
Author(s):  
Carlos Escobedo ◽  
Fatemeh Eftekhari ◽  
Jacqueline Ferreira ◽  
Paul Wood ◽  
Reuven Gordon ◽  
...  
Keyword(s):  
Electromagnetic Waves ◽  
Support Surface ◽  
Nanohole Array ◽  
Lab On Chip ◽  
Enhanced Transmission ◽  
Nanohole Arrays ◽  
Film Layer ◽  
Flow Through ◽  
On Chip ◽  
Array Sensing

Arrays of nanoholes in metal films present several opportunities as surface based sensors in lab-on-chip systems. Metallic nanohole arrays support surface electromagnetic waves that enable enhanced transmission through the holes and have been harnessed for chemical and biological sensing. Nanohole array based sensing performed to date has involved nanoholes that end shortly beyond the metallic film layer on a substrate such as glass. Such dead-ended holes fail to harness the potential of through-hole nanohole arrays including enhanced transport of reactants to the active area and a solution sieving action that is unique among surface-based sensing methods. In this work we investigate the potential of a flow-through-array sensing format.

Dissolution kinetics of struvite pellets grown in a pilot-scale crystallizerA paper submitted to the Journal of Environmental Engineering and Science.

2009 ◽  
Vol 36 (3) ◽  
pp. 550-568 ◽  
Author(s):  
M.I.H. Bhuiyan ◽  
D.S. Mavinic ◽  
R.D. Beckie
Keyword(s):  
Batch Reactor ◽  
Dissolution Kinetics ◽  
Theoretical Models ◽  
Pilot Scale ◽  
Reactor System ◽  
Alkaline Ph ◽  
Rate Of Dissolution ◽  
Flow Through ◽  
Experimental Values ◽  
Kinetics Of

Dissolution kinetics of struvite are important for optimizing intentional struvite crystallization, as well as for ensuring the efficient use of the crystallized products. Dissolution experiments were carried out for struvite pellets grown in a pilot-scale fluidized bed reactor. To determine the kinetics and mechanism of the dissolution process in a batch reactor system, two different theoretical models were tested. The experimental values were found to fit well with both models. In a mixed flow-through reactor system, the constituents release became stoichiometric when the input solution had an alkaline pH. The dissolution rates for struvite pellets were found to decrease with increasing pH due to proton promoted dissolution. After a transition from around 7.5 to 8, the rate of dissolution increased with the increase in pH, because of the hydroxyl promoted dissolution.

Paper 3: Steady Flow Tests on Twin Poppet Valves

1967 ◽  
Vol 182 (4) ◽  
pp. 126-133 ◽  
Author(s):  
W. A. Woods
Keyword(s):  
Steady Flow ◽  
Pressure Loss ◽  
Pressure Ratio ◽  
Effective Area ◽  
Valve Lift ◽  
Cylinder Wall ◽  
Large Area ◽  
Pressure Losses ◽  
Flow Through ◽  
Poppet Valves

This paper presents the results of an experimental investigation of steady flow through a pair of exhaust poppet valves. An account is given of the gas exchange process on engines which use poppet valves and the reason why pressure losses should be kept to a minimum is explained. Tests carried out on the cylinder head of a uniflow two-stroke cycle engine are described following a brief description of the apparatus used. The results of a simple analysis of incompressible flow are also given. It is shown that the two previous models of flow through a valve, namely the sudden enlargement and constant static pressure, both give unrealistic pressure losses for large area ratios, i.e. at high valve lifts. A new model is introduced which leads to realistic pressure losses at small and large area ratios, i.e. at low and high valve lifts. Effective areas for the present tests are calculated on the basis of the constant pressure model, and details of calculation of pressure losses are outlined. The blockage effect caused by placing the exhaust valves near the cylinder wall is given in the discussion of the test results. This is zero for 0 < l/d < 0·08, but reaches a maximum blockage of 10 per cent at l/d = 0·28. With unrestricted twin valves the effective area is about twice that of a single valve up to l/d = 0·18 with a progressively larger effective area at lifts up to 13 per cent higher at l/d = 0·4. A comparison is also made with other data readily available. The pressure losses determined from the tests were analysed using a parameter derived in the simple theory. The parameter used is found to be almost independent of pressure ratio and the results are presented by means of this pressure loss parameter as a function of valve lift. The representation provides a quantitative method of comparing the performance of a given configuration of valve and port. On this basis the twin poppet valves are shown to give a slightly higher pressure loss than a single valve.

scholarly journals Understanding jökulhlaups: From tale to theory

2010 ◽  
Vol 56 (200) ◽  
pp. 1002-1010 ◽  
Author(s):  
Helgi Björnsson
Keyword(s):  
Theoretical Models ◽  
Frictional Heat ◽  
Drainage Systems ◽  
Linear Rise ◽  
Observed Behaviour ◽  
Flow Through ◽  
Discharge Patterns ◽  
The One ◽  
Different Sources ◽  
Source Geometry

AbstractThe study of jökulhlaups has advanced from describing them qualitatively to measuring systematically on site their discharge curves and source geometry, as well as investigating conditions when particular floods were initiated. In the early days of this science, hypotheses were formulated which attempted to explain the processes responsible for unstable flood growth. The general theory of time-dependent turbulent water flow through intraglacial conduits marked a breakthrough in understanding jökulhlaup hydraulics and has since remained a classical foundation for jökulhlaup studies. This theory described flood evolution in terms of water input into the upper end of a tunnel leading from a reservoir, taking account of sensible stored lake heat and geometry. Such a tunnel expands by positive feedback, since its ice walls melt through frictional heat produced by the flowing water. While this model successfully described jökulhlaups in which the discharge hydrograph increases more or less exponentially over time, other floods were observed which are in stark contrast. In them, pressurized floodwater propagates in a turbulent subglacial water sheet which opens and expands a system of conduits, with an extremely rapid linear rise in discharge. The rushing water enlarges its subglacial pathway not only by melting the ice around it but also by lifting, deforming and fracturing it. Subsequent drainage is nourished by two different sources, with conduit growth being controlled not only by water input at the upper end of the flood path but also by further water joining in, all the way to the edge of the glacier. Moreover, the trigger for releasing meltwater from glacial lakes has been seen to be either of two conduit opening mechanisms, which also determine whether a turbulent subglacial water sheet will result or not. On the one hand, drainage may begin by expanding already existing conduits, in which case the pressure remains lower than that of the ice overburden at the dam and the conduits grow slowly. On the other hand, lake levels may rise until flotation of the ice dam, abruptly opening a sufficient gap for water to propagate as a sheet flow. In order to explain which of these two initiation mechanisms will act, further studies are required into the structure of hydrological drainage systems under ice dams and into their linkage with these two mechanisms. Although current theoretical models of jökulhlaups drainage have managed to reproduce the observed discharge patterns, inconsistencies with the observed behaviour of subglacial drainage systems along the flood path demand further exploration of the actual hydraulic and glaciodynamic processes of jökulhlaups.

scholarly journals Modelling the Force Action of a Liquid on the Shutter of a Measuring Transducer

2020 ◽  
Vol 157 ◽  
pp. 02007
Author(s):  
Vitaly Golubovsky ◽  
Vladimir Konovalov ◽  
Marina Doncova
Keyword(s):  
Measuring Transducer ◽  
Theoretical Models ◽  
Liquid Jets ◽  
Hydrodynamic Effect ◽  
Correction Factors ◽  
Force Action ◽  
Original Design ◽  
Supply Pressure ◽  
Experimental Values ◽  
Two Jets

The article describes the original design of the measuring transducer of angular velocity of the type “flapper-nozzle “. The aim of the study is mathematical modeling in the MathCAD program of the force action of liquid jets exiting nozzles, since this significantly affects the characteristics of the converter. The calculated values of the acting forces are compared by several known methods and their results are compared with experimental data. For the proposed design of the measuring transducer, greater convergence of the theoretical and experimental values of the power characteristic in the linear section is provided by the expressions for determining the force effect of two jets on the damper, defined as the hydrodynamic effect of the liquid jet on the obstacle. Given the real differences in the design of the converter from theoretical models, it is required to apply correction factors. As pressure increases, the coefficient increases from 1 to 1.24-1.30 depending on the pressure supplied to the measuring transducer and the version of expression used to calculate it. When using the expression for the approximate calculation of the acting forces in the converter, the correction factor is much higher and varies from 1.9 at a supply pressure of 0.5 MPa to 1.74 at a supply pressure of 1.5-2.0 MPa. The practical use of this calculation option is limited to the linear zone of pressure dependence in the working chambers of the converter on the gap between the nozzles and the shutter.

Fluid Flow Through Randomly Packed Monodisperse Fibers: The Kozeny-Carman Parameter Analysis

1997 ◽  
Vol 119 (1) ◽  
pp. 188-192 ◽  
Author(s):  
O. Rahli ◽  
L. Tadrist ◽  
M. Miscevic ◽  
R. Santini
Keyword(s):  
Fluid Flow ◽  
Experimental Studies ◽  
Theoretical Models ◽  
Experimental Results ◽  
Parameter Analysis ◽  
Flow Through Porous Media ◽  
Aspect Ratios ◽  
A Value ◽  
Flow Through ◽  
Permeability Increase

Experimental studies have been carried out on fluid flow through porous media made up of randomly packed monodisperse fibers. The permeability and the Kozeny-Carman parameter kk are deduced from experimental results. The variations of the permeability increase exponentially with the porosity. The parameter kk is a decreasing function of the porosity ε and tends asymptotically to a value close to that deduced from a modified Ergun relation. The important decrease, observed for small aspect ratios, is certainly an effect of the cut sections of fibers. The results in terms of parameter kk are systematically compared to those deduced from various theoretical models. The variation laws of the parameter kk, deduced from different models, present important discrepancies with our experimental results.

Stokes Flow Through a Row of Cylinders Between Parallel Walls: Model for the Glomerular Slit Diaphragm

1994 ◽  
Vol 116 (2) ◽  
pp. 184-189 ◽  
Author(s):  
M. Claudia Drumond ◽  
William M. Deen
Keyword(s):  
Stokes Flow ◽  
Stokes Equations ◽  
Slit Diaphragm ◽  
Hydraulic Permeability ◽  
Shear Stresses ◽  
Two Factors ◽  
Additional Resistance ◽  
Flow Through ◽  
Experimental Values ◽  
Glomerular Capillaries

As a model for flow through the slit diaphragms which connect the epithelial foot processes of renal glomerular capillaries, finite element solutions of Stokes equations were obtained for flow perpendicular to a row of cylinders confined between parallel walls. A dimensionless “additional resistance” (f), defined as the increment in resistance above the Poiseuille flow value, was computed for L/W≤4 and 0.1≤ R/L≤0.9, where L is half the distance between cylinder centers, W is half the distance between walls and R is the cylinder radius. Two factors contributed to f: the drag on the cylinders, and the incremental shear stresses on the walls of the channel. Of these two factors, the drag on the cylinders tended to be dominant. A more complex representation of the slit diaphragm, suggested in the literature, was also considered. The predicted hydraulic permeability of the slit diaphragm was compared with experimental values of the overall hydraulic permeability of the glomerular capillary wall.

The Relationship Between Breach Development and the Depressurization Transient During Axial Rupture of a Gas-Pressurized Steel Pipe

1982 ◽  
Vol 104 (1) ◽  
pp. 20-24 ◽  
Author(s):  
M. R. Baum
Keyword(s):  
Rarefaction Wave ◽  
Gas Flow ◽  
Theoretical Models ◽  
Observation Point ◽  
Steel Pipe ◽  
Growth Data ◽  
Flow Through ◽  
The Relationship ◽  
Experimental Pressure ◽  
Good Agreement

Theoretical models are developed to predict the depressurization generated by a propagating axial rupture in a gas-pressurized steel pipe. The pressure transient is composed of a relatively slow depressurization within the rarefaction wave which propagates through the undisturbed gas ahead of the developing breach and a rapid depressurization within the breach zone. The models combine a simplified one-dimensional treatment of the gas flow local to the breach with experimental breach area growth data. An instantaneous steady flow through the developing breach is assumed to determine the boundary condition for the rarefaction wave. The breach zone depressurization is assumed to be dominated by the transverse wave action initiated by the arrival of the breach at the observation point. In both cases the predicted transients are in good agreement with experimental pressure histories.

Influence of the Contact Pressure on the Rolling Resistance Moments in Dry Ball-Race Contacts

2014 ◽  
Vol 658 ◽  
pp. 305-310
Author(s):  
Alina Corina Dumitrascu ◽  
Gelu Ianus ◽  
Dumitru Olaru
Keyword(s):  
Theoretical Model ◽  
Contact Pressure ◽  
Rotational Speed ◽  
Ball Bearing ◽  
Rolling Resistance ◽  
Theoretical Models ◽  
Hertzian Contact ◽  
Experimental Methodology ◽  
Experimental Values ◽  
Good Agreement

Based on a theoretical model and an experimental methodology for defining the rolling resistance moments in a modified thrust ball bearing having only 3 balls, the authors experimentally investigated the influence of the Hertzian contact pressure on rolling resistance moments between a ball and a race. The experiments were realized with balls having diameters between 1.588 mm and 4.762 mm with maximum Hertzian pressure between 0.2GPa and 1GPa, operating for rotational speed between 60rpm to 210 rpm. The experiments evidenced that the measured values of the rolling resistance moments have higher values that the theoretical hysteresis and curvature rolling resistance moments for low contact pressure. By increasing of the contact pressure to 1GPa the experimental values for rolling resistance moments are in good agreement with the theoretical models.

Sign in / Sign up

Export Citation Format

Share Document