Numerical Simulation of the Flow Around a Circular Cylinder Following a Figure-8-Like Path

2010 ◽  
Author(s):  
La´szlo´ Baranyi
Keyword(s):  
Circular Cylinder ◽  
Frequency Ratio ◽  
Numerical Study ◽  
Mirror Image ◽  
Computational Method ◽  
Mean Values ◽  
Smooth Curves ◽  
Before And After ◽  
The Finite Difference Method ◽  
Line Amplitude

This numerical study investigates a circular cylinder placed in a uniform stream and moving along a slender figure-8 path. A 2D computational method based on the finite difference method was used. Two aspects were investigated separately: the effect of in-line amplitude of oscillation and the effect of the frequency ratio. Computations for varying amplitude values were carried out at Re = 150, 200 and 250. Time-mean and rms values of force coefficients yielded smooth curves and tended to increase with amplitude. When plotted against frequency ratio in the domain of 0.69 to 0.98 at Re = 250, a jump was found in the time-mean values of lift and torque. This was also present in the energy transfer curves, and positive and negative values were found. Limit cycle curves from before and after a jump were symmetric, mirror images, and quite complex. Vorticity contours also showed a mirror image pre- and post-jump. These results indicate the possibility of symmetry-breaking bifurcation.

scholarly journals Simulation of a low-reynolds number flow around a cylinder following a figure-8-path

2012 ◽  
Vol 3 (2) ◽  
pp. 133-146 ◽  
Author(s):  
L. Baranyi
Keyword(s):  
Frequency Ratio ◽  
Numerical Study ◽  
Mechanical Energy ◽  
Computational Method ◽  
Smooth Curves ◽  
Reynolds Number Flow ◽  
Before And After ◽  
Specific Frequency ◽  
Number Flow ◽  
Lock In

Abstract This numerical study investigates a circular cylinder placed in a uniform stream and moving along a slender figure-8-path, using a 2D computational method based on the finite difference method. The effects of in-line amplitude of oscillation and of frequency ratio are investigated. Computations for varying amplitude values were carried out at Re = 150, 200 and 250 for a clockwise orbit (in the upper loop). Time-mean and rms values of force coefficients yielded smooth curves and tended to increase with amplitude. The effect of frequency ratio was investigated at Re = 200, 250 and 300 in the lock-in domain for both clockwise (CW) and anticlockwise (ACW) orientation. Results differ substantially depending on the direction of orientation. Mechanical energy transfer was always positive in ACW direction, which may lead to vortex-induced vibration, and always negative for CW orientation. The time-mean of drag was much lower for CW over the whole frequency ratio domain investigated. For the CW orbit vortex switches were found at specific frequency ratios at Re = 250 and 300. Limit cycle curves for the CW orbit before and after a jump were symmetric, mirror images, and quite complex, while vorticity contours were close to symmetry. These results indicate the possibility of symmetry-breaking bifurcation.

The Numerical Simulation of Two-Degrees-of-Freedom Vortex-Induced Vibrations of Circular Cylinder with High Mass-Ratio

2013 ◽  
Vol 284-287 ◽  
pp. 557-561
Author(s):  
Jie Li Fan ◽  
Wei Ping Huang
Keyword(s):  
Circular Cylinder ◽  
Drag Force ◽  
Frequency Ratio ◽  
Lift Force ◽  
Degrees Of Freedom ◽  
Cross Flow ◽  
High Mass ◽  
Mass Ratio ◽  
Main Frequency ◽  
Line Amplitude

The two-degrees-of-freedom VIV of the circular cylinder with high mass-ratio is numerically simulated with the software ANSYS/CFX. The VIV characteristic is analyzed in the different conditions (Ur=3, 5, 6, 8, 10). When Ur is 5, 6, 8 and 10, the conclusion which is different from the cylinder with low mass-ratio can be obtained. When Ur is 3, the frequency of in-line VIV is twice of that of cross-flow VIV which is equal to the frequency ratio between drag force and lift force, and the in-line amplitude is much smaller than the cross-flow amplitude. The motion trace is the crescent. When Ur is 5 and 6, the frequency ratio between the drag force and lift force is still 2, but the main frequency of in-line VIV is mainly the same as that of cross-flow VIV and the secondary frequency of in-line VIV is equal to the frequency of the drag force. The in-line amplitude is still very small compared with the cross-flow amplitude. When Ur is up to 8 and 10, the frequency of in-line VIV is the same as the main frequency of cross-flow VIV which is close to the inherent frequency of the cylinder and is different from the frequency of drag force or lift force. But the secondary frequency of cross-flow VIV is equal to the frequency of the lift force. The amplitude ratio of the VIV between in-line and cross-flow direction is about 0.5. When Ur is 5, 6, 8 and 10, the motion trace is mainly the oval.

ENDOCRINE CHANGES BEFORE AND AFTER THE MENARCHE

1973 ◽  
Vol 74 (4) ◽  
pp. 685-694 ◽  
Author(s):  
B.-A. Lamberg ◽  
R.-L. Kantero ◽  
P. Saarinen ◽  
O. Widholm
Keyword(s):  
Binding Proteins ◽  
Maturation Process ◽  
Hormone Binding ◽  
Maximal Level ◽  
Continuous Increase ◽  
Mean Values ◽  
Thyroxine Binding Globulin ◽  
Before And After ◽  
Free Thyroxine Index ◽  
Level 1

ABSTRACT In an endocrine survey of healthy girls aged 8 to 20 years before and after the menarche, the serum thyroxine (T4), uptake of triiodothyronine by Sephadex (T3U), and the binding capacities of thyroxine binding globulin (TBG) and pre-albumin (TBPA) were measured, and a free thyroxine index (FTI = T4 × T3U) was calculated. The subjects were grouped according to skeletal age (SA) until the menarche and after this in the post-menarcheal age (PMA), expressed in years. T4 and FTI increased concomitantly and reached peak values of 8.40 μg/100 ml and 8.40, respectively, at 2–3 years PMA. The corresponding mean values for post-menarcheal girls (7.74 μg/100 ml and 7.51) differed statistically significantly from the means before the menarche (7.03 μg/ 100 ml and 6.75). The TBG remained virtually unchanged during the whole period, whereas the TBPA showed a continuous increase and reached a maximal level 1–2 years after the menarche. The maturation process in girls in some way involves an increase in the total and free T4 level which is not dependent on hormone binding proteins.

Sensitivity of bioelectrical impedance to detect changes in human body composition

1989 ◽  
Vol 67 (4) ◽  
pp. 1643-1648 ◽  
Author(s):  
R. Ross ◽  
L. Leger ◽  
P. Martin ◽  
R. Roy
Keyword(s):  
Body Composition ◽  
Human Body ◽  
Correlation Coefficients ◽  
Bioelectrical Impedance ◽  
Mean Values ◽  
Significance Level ◽  
Exercise Regimen ◽  
Before And After ◽  
Hydrostatic Weighing ◽  
Human Body Composition

The purpose of this study was to compare the estimates of lean body mass (LBM) and percent body fat (%BF), as predicted by bioelectrical impedance (BIA) and sum of skinfolds (SF), with those derived by hydrostatic weighing (HW) obtained before and after a 10-wk diet and exercise regimen. The experimental (E) group consisted of 17 healthy male subjects; 20 healthy males served as the control (C) group. Post hoc Scheffe contrasts computed on E group data indicated that, for both LBM and %BF, the Lukaski and Segal BIA equations, as well as the Durnin SF equation, derived mean values that were not significantly different (0.05 significance level) from HW in both pre- and postregimen conditions. For LBM, the same equations derived the following significant (P less than 0.01) correlation coefficients for both pre- and postregimen data: Lukaski, 0.87 and 0.85; Segal, 0.89 and 0.87; and Durnin, 0.90 and 0.88. For %BF, the correlation coefficients were slightly lower but remained statistically significant (P less than 0.01). The findings of this study suggest that the BIA method, by use of either the Lukaski or Segal prediction equations, is a valid means of predicting changes in human body composition as measured by the Siri transformation of body density.

scholarly journals Influence of Apical Patency and Cleaning of the Apical Foramen on Periapical Extrusion in Retreatment

2013 ◽  
Vol 24 (5) ◽  
pp. 482-486 ◽  
Author(s):  
Marili Doro Andrade Deonizio ◽  
Gilson Blitzkow Sydney ◽  
Antonio Batista ◽  
Roberto Pontarolo ◽  
Paulo Ricardo Bittencourt Guimarães ◽  
...  
Keyword(s):  
Material Removal ◽  
Filling Material ◽  
Mean Values ◽  
Filtration System ◽  
Root Canal Retreatment ◽  
Significant Difference ◽  
Before And After ◽  
The Mean ◽  
The Difference ◽  
Removal Technique

This study evaluated the influence of apical patency, root filling removal technique and cleaning of the apical foramen, concerning the amount of debris extruded during root canal retreatment. Forty mandibular incisors were randomly assigned to 4 groups - GIM (n=10), GIIM (n=10), GIPT (n=10) and GIIPT (n=10), which were named according to leaving (I) or not (II) apical patency during canal preparation and filling removal technique (manual - M or ProTaper system - PT). After filling material removal, each specimen of each group had the apical foramen cleaned by sizes 15, 20 and 25 instruments, generating 12 subgroups: GIM15, GIM20, GIM25, GIIM15, GIIM20, GIIM25, GIPT15, GIPT20, GIPT25, GIIPT15, GIIPT20 and GIIPT25. Extruded filling debris was collected by a Milipore filtration system, an HV-durapore, 0.45 µm pore filter with a 25 mm diameter. The filters were weighed before and after the collection on an analytical scale (10–5 g), and the difference was calculated. The mean weight of extruded filling debris was analyzed statistically by Kruskal-Wallis and Friedman ANOVA tests (α=0.05). The mean values found in the groups (in mg) were: GIM (0.95±0.94), GIIM (0.47±0.62), GIPT (0.30±0.31) and GIIPT (0.32±0.44). There was no statistically significant difference among any of the groups or subgroups (p>0.05). ProTaper provided the smallest amount of extruded filling material, regardless of presence or absence of apical patency, followed by manual technique, without and with apical patency. Additional amounts of debris were collected during cleaning of the apical foramen, regardless of the instrument, presence/absence of patency or root filling removal technique.

Effect of induced metabolic acidosis on intracellular pH, buffer capacity and contraction force of human skeletal muscle

1985 ◽  
Vol 69 (5) ◽  
pp. 505-510 ◽  
Author(s):  
E. Hultman ◽  
S. Del Canale ◽  
H. Sjöholm
Keyword(s):  
Buffer Capacity ◽  
Recovery Period ◽  
Mean Values ◽  
Muscle Ph ◽  
Before And After ◽  
Ph Buffer ◽  
Total Capacity ◽  
Ph Decrease ◽  
Muscle Biopsies

1. Five volunteers were studied before and after oral administration of NH4Cl (0.3 g/kg body wt.) given in order to create a moderate acidosis. 2. The quadriceps femoris muscles were stimulated electrically for 75 s and muscle biopsies for determination of pH and metabolite content were taken before, at the end of contraction and after 10 min in the recovery period. 3. Muscle pH at rest (mean 7.04) was not significantly decreased after acidification despite an extracellular pH decrease of 0.15 unit. 4. After contraction muscle pH was significantly lower after NH4Cl. Mean values before and after acidification were 6.70 and 6.54 respectively. 5. The buffer capacity calculated as the total capacity of the muscle to buffer H+ produced during the isometric contraction before and after NH4Cl ingestion was reduced from 68.6 sl to 54.5 sl. 6. The force produced by contracting muscle was significantly lower at the end of the contraction period after NH4Cl ingestion, 44.6% of initial compared with 55.4% without NH4Cl.

Sloshing in Rectangular and Cylindrical Tanks

2002 ◽  
Vol 46 (03) ◽  
pp. 186-200 ◽  
Author(s):  
Pierre C. Sames ◽  
Delphine Marcouly ◽  
Thomas E. Schellin
Keyword(s):  
Free Surface ◽  
Finite Volume ◽  
Temporal Evolution ◽  
Numerical Study ◽  
Computational Method ◽  
Test Cases ◽  
Grid Refinement ◽  
Cylindrical Tank ◽  
Excitation Period ◽  
Cylindrical Tanks

To validate an existing finite volume computational method, featuring a novel scheme to capture the temporal evolution of the free surface, fluid motions in partially filled tanks were simulated. The purpose was to compare computational and experimental results for test cases where measurements were available. Investigations comprised sloshing in a rectangular tank with a baffle at 60% filling level and in a cylindrical tank at 50% filling level. The numerical study started with examining effects of systematic grid refinement and concluded with examining effects of three-dimensionality and effects of variation of excitation period and amplitude. Predicted time traces of pressures and forces compared favorably with measurements.

Effect of Incisions in the Brainstem Commissural Network on the Short-Term Vestibulo-Ocular Adaptation of the CAT

1991 ◽  
Vol 1 (3) ◽  
pp. 223-239
Author(s):  
G. Cheron
Keyword(s):  
Low Frequency ◽  
Adaptive Plasticity ◽  
Training Procedure ◽  
Optokinetic Response ◽  
Mean Values ◽  
Ocular Reflex ◽  
Optokinetic Reflex ◽  
Before And After ◽  
Vestibulo Ocular Reflex ◽  
Vor Adaptation

This study was intended to test the adaptive plasticity of the vestibulo-ocular reflex before and after either a midsagittal or parasagittal incision in the brainstem. Eye movements were measured with the electromagnetic search coil technique during the vestibulo-ocular reflex (VORD) in the dark, the optokinetic reflex (OKN), and the visuo-vestibular adaptive training procedure. Two types of visual-vestibular combined stimulation were applied by means of low frequency stimuli (0.05 to 0.10 Hz). In order to increase or decrease the VORD gain, the optokinetic drum was oscillated either 180∘ out-of-phase or in-phase with the vestibular stimulus turntable. This “training” procedure was applied for 4 hours. Initial measurements of the VORD were normal with a mean gain value of 0.92 ± 0.08. After 4 hours of “training” with the out-of-phase condition (180∘), VORD gain reached mean values of 1.33 ± 0.11 (n = 6 cats). In the in-phase combination, the mean VORD gain decreased from 1.0 to 0.63 ± 0.02 (n = 2 cats). No significant change of VORD phase was found in any of the cats. Midsagittal or parasagittal pontomedullary brainstem incisions were performed in 4 cats. Recovery of the VOR was tested on the 2nd, 7th, and 30th day after operation. After the 30th day, recovery of the VORD gain stabilized at about 66% of the initial preoperative value. At this stage of the recovery, the optokinetic response (OKN) of the midsagittal-Iesioned cats was practically normal: in the parasagittal-Jesioned cats, the postoperative OKN responses were asymmetric. After stabilization of recovery, lesioned cats were trained with the same adaptation procedure. Although the direct effect of the visuo-vestibular combined stimulation during the training was still operative in all lesioned cats, the adaptive plasticity was completely abolished by the lesions. These results suggest that the commissural brainstem network may play a crucial role in the acquisition of the forced VOR adaptation.

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