scholarly journals Time-Dependent Pressure and Flow Behavior of a Self-oscillating Laryngeal Model With Ventricular Folds

2015 ◽  
Vol 29 (6) ◽  
pp. 649-659 ◽  
Author(s):  
Fariborz Alipour ◽  
Ronald C. Scherer
Keyword(s):  
Flow Behavior ◽  
Time Dependent ◽  
Ventricular Folds

scholarly journals Time Dependent Lyotropic Chromonic Textures in Microfluidic Confinements

Crystals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 35 ◽  
Author(s):  
Anshul Sharma ◽  
Irvine Lian Hao Ong ◽  
Anupam Sengupta
Keyword(s):  
Phase Transition ◽  
Aspect Ratio ◽  
Temporal Dynamics ◽  
Initial Conditions ◽  
Flow Behavior ◽  
Medical Diagnostics ◽  
Time Dependent ◽  
Disodium Cromoglycate ◽  
M Phase ◽  
Static Conditions

Nematic and columnar phases of lyotropic chromonic liquid crystals (LCLCs) have been long studied for their fundamental and applied prospects in material science and medical diagnostics. LCLC phases represent different self-assembled states of disc-shaped molecules, held together by noncovalent interactions that lead to highly sensitive concentration and temperature dependent properties. Yet, microscale insights into confined LCLCs, specifically in the context of confinement geometry and surface properties, are lacking. Here, we report the emergence of time dependent textures in static disodium cromoglycate (DSCG) solutions, confined in PDMS-based microfluidic devices. We use a combination of soft lithography, surface characterization, and polarized optical imaging to generate and analyze the confinement-induced LCLC textures and demonstrate that over time, herringbone and spherulite textures emerge due to spontaneous nematic (N) to columnar M-phase transition, propagating from the LCLC-PDMS interface into the LCLC bulk. By varying the confinement geometry, anchoring conditions, and the initial DSCG concentration, we can systematically tune the temporal dynamics of the N- to M-phase transition and textural behavior of the confined LCLC. Overall, the time taken to change from nematic to the characteristic M-phase textures decreased as the confinement aspect ratio (width/depth) increased. For a given aspect ratio, the transition to the M-phase was generally faster in degenerate planar confinements, relative to the transition in homeotropic confinements. Since the static molecular states register the initial conditions for LC flows, the time dependent textures reported here suggest that the surface and confinement effects—even under static conditions—could be central in understanding the flow behavior of LCLCs and the associated transport properties of this versatile material.

The flow properties of honey–malt spread

2017 ◽  
Vol 23 (5) ◽  
pp. 415-425 ◽  
Author(s):  
M Dianat ◽  
M Taghizadeh ◽  
F Shahidi ◽  
SMA Razavi
Keyword(s):  
Flow Behavior ◽  
Time Dependent ◽  
Malt Extract ◽  
Barley Malt ◽  
First Order ◽  
Dependent Behavior ◽  
Thixotropic Behaviour ◽  
Order Stress ◽  
Temperature Levels ◽  
Independent Behavior

In this study, the effect of barley malt extract at two brix levels (74 and 79 °Bx) and three ratios of malt extract/honey (65:35, 70:30 and 75:25) on the flow behavior properties of honey–malt spread at three temperature levels (35 ℃, 45 ℃ and 55 ℃) was investigated. Time-dependent behavior data of the spread samples were appropriately fitted to the Weltman, first-order stress decay with a zero stress value and first-order stress decay with a non-zero stress value models. Also, the Power-law, Herschel–Bulkley, Casson and Bingham models were used for curve fitting the time-independent behavior data. Regarding the R2 and root mean square error coefficients, the first-order stress decay with a non-zero stress value and Herschel–Bulkley models were selected as the suitable models to describe the flow behavior of samples. The results for time-dependent properties showed that spread samples exhibit a thixotropic behaviour, as the viscosity for all samples decreased with increase in shearing time at a constant shear rate of 50 s−1.

Time-Dependent Rheological Behavior of Fluids For Electronics Packaging

2005 ◽  
Vol 127 (4) ◽  
pp. 370-374 ◽  
Author(s):  
X. B. Chen
Keyword(s):  
Rheological Behavior ◽  
Printed Circuit Boards ◽  
Flow Behavior ◽  
Electronics Packaging ◽  
Time Dependent ◽  
Circuit Boards ◽  
Printed Circuit ◽  
Fluid Behavior ◽  
Surface Mounting

In electronics packaging, one of the key processes is dispensing fluid materials, such as adhesive, epoxy, encapsulant, onto substrates or printed circuit boards for the purpose of surface mounting or encapsulation. In order to precisely control the dispensing process, the understanding and characterization of the flow behavior of the fluid being dispensed is very important, as the behavior can have a significant influence on the dispensing process. However, this task has proven to be very challenging due to the fact that the fluids for electronics packaging usually exhibit the time-dependent rheological behavior, which has not been well defined in literature. In the paper a study on the characterization of the time-dependent rheological behavior of the fluids for electronics packaging is presented. In particular, a model is developed based on structural theory and then applied to the characterization of the decay and recovery of fluid behavior, which happen in the dispensing process due to the interruption of process. Experiments are carried out to verify the effectiveness of the model developed.

Characterization of the Time-Dependent Rheological Behavior of Fluids for Electronics Packaging

2003 ◽  
Author(s):  
X. B. Chen ◽  
W. J. Zhang ◽  
G. Schoenau ◽  
B. W. Surgenor
Keyword(s):  
Rheological Behavior ◽  
Flow Behavior ◽  
Electronics Packaging ◽  
Structural Theory ◽  
Time Dependent ◽  
Fluid Behavior ◽  
Proposed Model ◽  
Key Issues

To effectively control the dispensing process by which fluids are delivered onto substrates in electronics packaging, one of the key issues is to understand and characterize the flow behavior of the fluids being dispensed. However, this task has proven to be a demanding one as the fluids used for electronics packaging usually exhibit the time-dependent rheological behavior, which has not been well documented in the literature. In this paper, the characterization of time-dependent rheological behavior of fluids is studied. In particular, a model using the structural theory is proposed and applied to the characterization of the decay and recovery of fluid behavior, which are typically encountered in a dispensing process. Experiments are conducted to validate the proposed model.

Experimental Investigation of a Single Stage Axial Flow Compressor With Controlled Diffusion Airfoils

1996 ◽  
Author(s):  
S. Pieper ◽  
J. Schulte ◽  
A. Hoynacki ◽  
H. E. Gallus
Keyword(s):  
Pressure Field ◽  
Flow Behavior ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Time Dependent ◽  
Suction Surface ◽  
Average Technique ◽  
Unsteady Pressure ◽  
Controlled Diffusion

In order to verify an inverse design concept for modern compressor bladings, a subsonic compressor front stage with IGV was investigated. One objective of the design was to survey the flow field in detail, with emphasis on 3D viscous and unsteady aspects of the flow. Therefore, the compressor was equipped with various steady and unsteady measurement techniques. Additionally, a compressor design was chosen that allows an extension up to three stages with regard to the investigation of multistage axial compressor flow behavior. Test results of the steady measurements are discussed for IGV, rotor, and stator flow at design conditions as well as the overall stage performance. The measurements of the steady flow behavior confirm the expected design performance and show the high potential of the controlled diffusion airfoil concept. Only at the side walls near hub and casing there are some differences between design and measurement due to the complex three dimensional flow. For the study of unsteady effects, detailed measurements using hot-wire probes, glue-on hot-films, and semiconductor pressure transducers were performed. All measurements are evaluated using the ensemble-average technique. The results show how the boundary layers of the inlet guide vanes and stator blades develop in a flow that is periodically disturbed by the rotor. Time-dependent pressure distributions at midspan of both stators are described. In addition, the unsteady pressure field at the casing above the rotor was investigated. The minimum wall pressure is located away from the blade suction surface. The effects of tip clearance flow on the performance are presented. The radial extent covers 15% span from the tip. At rotor exit, the unsteady pressure field and the time-dependent three-dimensional velocity vectors illustrate the salient features of the viscous flow associated with the rotor.

Time-dependent rheological behavior of blood at low shear in narrow vertical tubes

1993 ◽  
Vol 265 (2) ◽  
pp. H553-H561 ◽  
Author(s):  
C. Alonso ◽  
A. R. Pries ◽  
P. Gaehtgens
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Shear Flow ◽  
Apparent Viscosity ◽  
Flow Behavior ◽  
Time Dependent ◽  
Flow Conditions ◽  
Wall Shear ◽  
Vertical Tubes ◽  
Low Shear

The time-dependent flow behavior of normal human blood after a sudden reduction of wall shear stress from 5,000 mPa to a low level (2-100 mPa) was studied during perfusion of vertical tubes (internal diam 28-101 microns) at constant driving pressures. Immediately after the implementation of low-shear flow conditions the concentration of red blood cells (RBCs) near the tube wall started to decrease, and marginal plasma spaces developed as a result of the assembly of RBC aggregates. This was associated with a time-dependent increase of flow velocity by up to 200% within 300 s, reflecting a reduction of apparent viscosity. These time-dependent changes of flow behavior increased strongly with decreasing wall shear stress and with increasing tube diameter. A correlation between the width of the marginal plasma layer and relative apparent viscosity was obtained for every condition of tube diameter, wall shear stress, and time. Time-dependent changes of blood rheological properties could be relevant in the circulation, where the blood is exposed to rapid and repeated transitions from high-shear flow conditions in the arterial and capillary system to low-shear conditions in the venous system.

Rheological and microstructural characterization of WPI-stabilized O/W emulsions exhibiting time-dependent flow behavior

LWT ◽  
2012 ◽  
Vol 46 (2) ◽  
pp. 375-381 ◽  
Author(s):  
Pablo Bellalta ◽  
Elizabeth Troncoso ◽  
Rommy N. Zúñiga ◽  
José M. Aguilera
Keyword(s):  
Flow Behavior ◽  
Microstructural Characterization ◽  
Time Dependent ◽  
Dependent Flow

Numerical and Experimental Investigation on Unsteady Inflow Conditions of a Pump-Turbine at Low Load

2014 ◽  
Author(s):  
S. Erne ◽  
G. Edinger ◽  
E. Doujak ◽  
C. Bauer
Keyword(s):  
Draft Tube ◽  
Flow Behavior ◽  
Low Frequency ◽  
Wall Pressure ◽  
Time Dependent ◽  
Discrete Fourier Transformation ◽  
Computational Domain ◽  
Pressure Measurements ◽  
Transient Pressure ◽  
Pump Turbine

This paper examines the occurrence of prerotation and reversal flow in the conical draft tube of a pump-turbine by using different turbulence models and compares the results to experiments. The computational domain consists of the entire geometry of a reduced scale pump-turbine. The results based on time-dependent computational fluid dynamics (CFD) are compared to laser doppler velocimetry (LDV) and wall-pressure-measurements in the conical part of the draft tube. Beside the LDV measurements, pressure fluctuations induced by complex flow patterns are also recorded and analyzed. The capability of simulations is assessed by an evaluation of the global integral values of the pump-turbine. The velocity profiles in axial and circumferential directions are compared at two measurement planes for two part-load operating points. The increased wall pressure distribution caused by swirling inflow is compared to the time averaged wall static-pressure from experiments. When operating at unstable pump conditions, an unsteady flow behavior arises in form of co-rotating vortices upstream of the impeller inlet. Analysis of the inlet flow shows continuously appearing and decaying vortex ropes in the conical draft tube. On the basis of these observations, discrete fourier transformation (DFT) analysis provides the power spectrum of the simulated time dependent pressure signal in the draft tube cone, where significant peaks below the runner rotational frequency are observed. The spectral analysis applied to transient pressure measurements at the draft tube wall shows dominant peaks in the low frequency region, which may indicate weak vortex structures rotating at low frequency.

Flow Behavior of Concentrated Suspensions of Yeast Grown on Sauerkraut Waste1

1975 ◽  
Vol 38 (6) ◽  
pp. 315-318 ◽  
Author(s):  
M. A. RAO ◽  
Y. D. HANG
Keyword(s):  
Power Law ◽  
Candida Utilis ◽  
Flow Behavior ◽  
Shear Thinning ◽  
Newtonian Fluids ◽  
Time Dependent ◽  
Concentrated Suspensions ◽  
Flow Models

The flow behavior of suspensions of yeast (Candida utilis) grown on sauerkraut waste was studied as a function of concentration at 25.8 C. Suspensions containing 5.8, 21.7, 22.6, 23.6, 24.7 and 27.0% dry solids behaved as Newtonian fluids. The viscosity of these suspensions increased exponentially with the concentration of dry solids. A 29.2% suspension showed time dependent shear-thinning behavior. The non-Newtonian characteristics of the suspension could be described by both the Power law and the Casson flow models.

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