Inspiratory and Expiratory Steady Flow Analysis in a Model Symmetrically Bifurcating Airway

1997 ◽  
Vol 119 (1) ◽  
pp. 52-58 ◽  
Author(s):  
Y. Zhao ◽  
C. T. Brunskill ◽  
B. B. Lieber
Keyword(s):  
Reynolds Number ◽  
Flow Analysis ◽  
Experimental Studies ◽  
Velocity Profiles ◽  
The Finite Element Method ◽  
Velocity Peak ◽  
Flow Features ◽  
Experimental Findings ◽  
Parent Tube ◽  
Good Agreement

Steady inspiratory and expiratory flow in a symmetrically bifurcating airway model was studied numerically using the finite element method (FIDAP). Flows of Reynolds number of 500 and 1000 during inspiration and a flow of Reynolds number of 500 during expiration were analyzed. Since the geometry of the bifurcation model used in this study is exactly the same as the model used in the experimental studies, the computed results were compared to the experimental findings. Results show that most of the important flow features that were observed in the experiment, such as the skewed velocity profiles in the daughter branches during inspiration and velocity peak in the parent tube during expiration, were captured in the numerical simulation. Quantitatively, the computed velocity profiles are in good agreement with the measured profiles. This comparison validates the computational simulations.

Optimization of Machining Parameters for Surface Roughness in EDM of AISI 1045 Based on Taguchi Technique

2010 ◽  
Author(s):  
Subodh Kumar ◽  
Sanjay Agarwal
Keyword(s):  
Surface Roughness ◽  
Discharge Current ◽  
Electrical Discharge Machining ◽  
Experimental Studies ◽  
Performance Measure ◽  
Influential Factors ◽  
Machining Parameters ◽  
Aisi 1045 ◽  
Experimental Findings ◽  
Good Agreement

Electrical discharge machining (EDM) is a nontraditional manufacturing technique that has been widely used in the production of tools and dies throughout the world in recent years. The most important performance measure in EDM is the surface roughness. In this study, the effect and optimization of machining parameters on surface roughness in an EDM operation was investigated by using the Taguchi method. The experimental studies were conducted under varying discharge current, duty cycle and pulse-duration. An orthogonal array, the signal-to-noise (S/N) ratio, and the analysis of variance (ANOVA) were employed to the study the surface roughness in the EDM of AISI 1045 tool steel. It was observed that the discharge current was the most influential factors on the surface roughness. To validate the study, confirmation experiment has been carried out at optimum set of parameters and predicted results have been found to be in good agreement with experimental findings.

Low Reynolds number fully developed two-dimensional turbulent channel flow with system rotation

1996 ◽  
Vol 315 ◽  
pp. 1-29 ◽  
Author(s):  
Koichi Nakabayashi ◽  
Osami Kitoh
Keyword(s):  
Reynolds Number ◽  
Skin Friction ◽  
Coriolis Force ◽  
Low Reynolds Number ◽  
Experimental Studies ◽  
Velocity Profiles ◽  
Friction Coefficients ◽  
Number Range ◽  
System Rotation ◽  
Low Reynolds

Theoretical and experimental studies have been performed on fully developed twodimensional turbulent channel flows in the low Reynolds number range that are subjected to system rotation. The turbulence is affected by the Coriolis force and the low Reynolds number simultaneously. Using dimensional analysis, the relevant parameters of this flow are found to be Reynolds number Re* = u*D/v (u* is the friction velocity, D the channel half-width) and Ωv/u2* (Ω is the angular velocity of the channel) for the inner region, and Re* and ΩD/u* for the core region. Employing these parameters, changes of skin friction coefficients and velocity profiles compared to nonrotating flow can be reasonably well understood. A Coriolis region where the Coriolis force effect predominates is shown to exist in addition to conventional regions such as viscous and buffer regions. A flow regime diagram that indicates ranges of these regions as a function of Re* and |Ω|v/u2* is given from which the overall flow structure in a rotating channel can be obtained.Experiments have been made in the range of 56 ≤ Re* ≤ 310 and -0.0057 ≤ Ωv/u2* ≤ 0.0030 (these values correspond to Re = 2UmD/v from 1700 to 10000 and rotation number R0 = 2|Ω|D/Um up to 0.055; Um is bulk mean velocity). The characteristic features of velocity profiles and the variation of skin friction coefficients are discussed in relation to the theoretical considerations.

An Experimental and Numerical Investigation on the Effects of Aerothermal Mixing in a Confined Oblique Jet Impingement Configuration

2015 ◽  
Author(s):  
Sebastian Schulz ◽  
Alexander Schindler ◽  
Jens von Wolfersdorf
Keyword(s):  
Reynolds Number ◽  
Jet Impingement ◽  
Field Measurements ◽  
Fluid Temperature ◽  
Number Range ◽  
Ansys Cfx ◽  
Image Velocimetry ◽  
Flow Features ◽  
Sst Turbulence Model ◽  
Good Agreement

An investigation to characterize the effect of entrainment in a confined jet impingement arrangement is presented. The investigated configuration models an impingement cooled turbine blade passage and holds two staggered rows of inclined impingement jets. In order to distinctly promote thermal entrainment phenomena the jets were heated separately. A steady-state liquid crystal technique was used to obtain near-wall fluid temperature distributions for the impingement surfaces at adiabatic conditions. Additionally, flow field measurements were undertaken using Particle Image Velocimetry (PIV). Furthermore, compressible RANS simulations were carried out with ANSYS CFX using Menter’s SST turbulence model to accompany the experiments. Distributions of effectiveness, velocity, and turbulent kinetic energy detail the complexity of the aerothermal situation. The study was conducted for a jet Reynolds number range from 10,000 to 45,000. The experimental and numerical results are generally in good agreement. Nevertheless, the simulations predict flow features in particular regions of the geometry that are not as prominent in the experiments. These affect the effectiveness distributions, locally. The investigations revealed that the effectiveness is independent of the temperature difference between the heated and cold jet as well as the jet Reynolds number.

Turbulent Lubrication Flow in an Annular Channel

1986 ◽  
Vol 108 (2) ◽  
pp. 185-192 ◽  
Author(s):  
H. G. Polderman ◽  
G. Velraeds ◽  
W. Knol
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Diffusion Model ◽  
Annular Channel ◽  
Velocity Profiles ◽  
Experimental Results ◽  
Wall Friction ◽  
Number Range ◽  
Gradient Diffusion ◽  
Good Agreement

An analytical and experimental study is presented of the lubrication flow in an annular channel with a moving core. Velocity profiles and wall friction were determined over a Reynolds number range up to 3 × 104 and radius ratios of 0.6 and 0.85. The experimental results are shown to be in good agreement with the predictions of a three-layer gradient-diffusion model.

Application of Back-Up Ring in Fine-Blanking Process

2010 ◽  
Vol 443 ◽  
pp. 140-145 ◽  
Author(s):  
Suthep Yiemchaiyaphum ◽  
Masahiko Jin ◽  
Sutasn Thipprakmas
Keyword(s):  
Flow Analysis ◽  
Fem Simulation ◽  
Material Flow Analysis ◽  
The Finite Element Method ◽  
Fine Blanking ◽  
Die Roll ◽  
Blanking Process ◽  
Cut Surface ◽  
Good Agreement

Considering the advantages of the fine-blanking process, the smooth-cut surface without further operation could be fabricated. However, one of the major problems of the fine-blanking is the occurrence of the die-roll formation. This problem is the main factor which affects the quality of the fine-blanked parts. In this study, to reduce the amount of die-roll formation, the application of back-up ring was proposed. The finite element method (FEM) was used to investigate the effects of back-up ring. In addition, the effects of bridge width were also investigated. The FEM simulation results illustrated that the mechanism of back-up ring and the effects of bridge width could be theoretically clarified base on the material flow analysis. The FEM simulation and experimental results showed the good agreement with each other. Therefore, the application of back-up ring could reduce the amount of die-roll formation on the fine-blanked parts. In this study, the amount of die-roll formation increased as the bridge width increase and it was constant at the bridge width of over 15 mm.

Fluid Inertia Forces in Squeeze Film Dampers

1991 ◽  
Author(s):  
A. El-Shafei ◽  
S. M. Crandall
Keyword(s):  
Reynolds Number ◽  
Velocity Profiles ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Eccentricity Ratio ◽  
Number Range ◽  
Squeeze Film Dampers ◽  
Energy Approximation ◽  
Inertia Forces ◽  
Good Agreement

Abstract Fluid inertia forces in Squeeze Film Dampers (SFDs) are obtained for short and long dampers using an energy approximation based on the assumption that the velocity profiles with inertia are the same as those for an inertialess fluid. It is shown that the inertia forces thus obtained are proportional to the usual radial, centripetal, tangential and Coriolis accelerations of the journal, plus an additional nonlinear acceleration. The inertia coefficients of the dampers are obtained, for both uncavitated and cavitated dampers, and are plotted versus the eccentricity ratio for centered, nearly circular whirl. The inertia forces obtained by the energy approximation are compared to an exact linearized solution for centered, circular whirl, and good agreement is found for both short and long dampers in the Reynolds number range of ordinary SFD application.

Analysis of the Contact Deformation of Tread Blocks

1992 ◽  
Vol 20 (4) ◽  
pp. 230-253 ◽  
Author(s):  
T. Akasaka ◽  
K. Kabe ◽  
M. Koishi ◽  
M. Kuwashima
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Deformation Behavior ◽  
Contact Deformation ◽  
The Finite Element Method ◽  
The Road ◽  
Loss Of Contact ◽  
Tread Rubber ◽  
Good Agreement ◽  
Rubber Block

Abstract The deformation behavior of a tire in contact with the roadway is complicated, in particular, under the traction and braking conditions. A tread rubber block in contact with the road undergoes compression and shearing forces. These forces may cause the loss of contact at the edges of the block. Theoretical analysis based on the energy method is presented on the contact deformation of a tread rubber block subjected to compressive and shearing forces. Experimental work and numerical calculation by means of the finite element method are conducted to verify the predicted results. Good agreement is obtained among these analytical, numerical, and experimental results.

scholarly journals Experimental studies on the transformation from firn to ice in the wet-snow zone of temperate glaciers

1997 ◽  
Vol 24 ◽  
pp. 181-185 ◽  
Author(s):  
Katsuhisa Kawashima ◽  
Tomomi Yamada
Keyword(s):  
Experimental Studies ◽  
Ice Formation ◽  
Compression Tests ◽  
Densification Rate ◽  
Overburden Pressure ◽  
Proportionality Constant ◽  
Wet Snow ◽  
Water Saturated ◽  
The Relationship ◽  
Good Agreement

The densification of water-saturated firn, which had formed just above the firn-ice transition in the wet-snow zone of temperate glaciers, was investigated by compression tests under pressures ranging from 0.036 to 0.173 MPa, with special reference to the relationship between densification rate, time and pressure. At each test, the logarithm of the densification rate was proportional to the logarithm of the time, and its proportionality constant increased exponentially with increasing pressure. The time necessary for ice formation in the firn aquifer was calculated using the empirical formula obtained from the tests. Consequently, the necessary time decreased exponentially as the pressure increased, which shows that the transformation from firn in ice can be completed within the period when the firn aquifer exists, if the overburden pressure acting on the water-saturated firn is above 0.12–0.14 MPa. This critical value of pressure was in good agreement with the overburden pressure obtained from depth–density curves of temperate glaciers. It was concluded that the depth of firn–ice transition was self-balanced by the overburden pressure to result in the concentration between 20 and 30 m.

scholarly journals Study of Influence of Width to Thickness Ratio in Sheet Metals on Bendability under Ambient and Superimposed Hydrostatic Pressure

2021 ◽  
Vol 2 (3) ◽  
pp. 542-558
Author(s):  
Mohammadmehdi Shahzamanian ◽  
David Lloyd ◽  
Amir Partovi ◽  
Peidong Wu
Keyword(s):  
Hydrostatic Pressure ◽  
Stress Ratio ◽  
Fracture Strain ◽  
Stress Triaxiality ◽  
Volumetric Strain ◽  
Thickness Ratio ◽  
Sheet Metals ◽  
The Finite Element Method ◽  
Bending Strain ◽  
Good Agreement

The effect of the width to thickness ratio on the bendability of sheet metal is investigated using the finite element method (FEM) employing the Gurson–Tvergaard–Needleman (GTN) model. Strain path changes in the sheet with change in the width/thickness ratio. It is shown that bendability and fracture strain increase significantly by decrease in the width/thickness ratio. The stress state is almost uniaxial when the stress ratio (α) is close to zero for narrow sheets. Stress ratio is nothing but the major stress to minor stress ratio. This delays the growth and coalescence of micro-voids as the volumetric strain and stress triaxiality (pressure/effective stress) decrease. On the other hand, ductility decreases with increase in α for wider sheets. Fracture bending strain is calculated and, as expected, it increases with decrease in the width/thickness ratio. Furthermore, a brief study is performed to understand the effect of superimposed hydrostatic pressure on fracture strain for various sheet metals with different width/thickness ratios. It is found that the superimposed hydrostatic pressure increases the ductility, and that the effect of the width/thickness ratio in metals on ductility is as significant as the effect of superimposed hydrostatic pressure. Numerical results are found to be in good agreement with experimental observations.

scholarly journals The Influence of Alcohol Consumption on Fighting, Shoplifting and Vandalism in Young Adults

2021 ◽  
Vol 18 (7) ◽  
pp. 3509
Author(s):  
Ieuan Evans ◽  
Jon Heron ◽  
Joseph Murray ◽  
Matthew Hickman ◽  
Gemma Hammerton
Keyword(s):  
Young Adults ◽  
Longitudinal Study ◽  
Alcohol Consumption ◽  
Experimental Studies ◽  
Real Life ◽  
Self Report ◽  
Parents And Children ◽  
Experimental Findings ◽  
Avon Longitudinal Study ◽  
Causal Component

Experimental studies support the conventional belief that people behave more aggressively whilst under the influence of alcohol. To examine how these experimental findings manifest in real life situations, this study uses a method for estimating evidence for causality with observational data—‘situational decomposition’ to examine the association between alcohol consumption and crime in young adults from the Avon Longitudinal Study of Parents and Children. Self-report questionnaires were completed at age 24 years to assess typical alcohol consumption and frequency, participation in fighting, shoplifting and vandalism in the previous year, and whether these crimes were committed under the influence of alcohol. Situational decomposition compares the strength of two associations, (1) the total association between alcohol consumption and crime (sober or intoxicated) versus (2) the association between alcohol consumption and crime committed while sober. There was an association between typical alcohol consumption and total crime for fighting [OR (95% CI): 1.47 (1.29, 1.67)], shoplifting [OR (95% CI): 1.25 (1.12, 1.40)], and vandalism [OR (95% CI): 1.33 (1.12, 1.57)]. The associations for both fighting and shoplifting had a small causal component (with the association for sober crime slightly smaller than the association for total crime). However, the association for vandalism had a larger causal component.

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