Measurements of Entrainment by Acoustically Pulsed Axisymmetric Air Jets

1986 ◽  
Vol 108 (3) ◽  
pp. 479-484 ◽  
Author(s):  
P. J. Vermeulen ◽  
V. Ramesh ◽  
Wai Keung Yu
Keyword(s):  
Strouhal Number ◽  
Exit Plane ◽  
Downstream Distance ◽  
Air Jets ◽  
Upper Limit ◽  
Direct Measurements

Direct measurements of entrainment by acoustically pulsed axisymmetric air jets flowing into surrounding air have been made for a range of orifice sizes, Strouhal numbers, and excitation powers. The entrainment was considerably increased, by up to 5.8 times at distances greater than 15 diameters axially downstream of the orifice exit plane. The entrainment of the excited jet varied linearly with downstream distance. The jet response varied nonlinearly with excitation strength, indicating that there may be a practical upper limit to the acoustic augmentation of entrainment. The response depends on Strouhal number and appears to be optimum at about 0.25.

Measurements of the Entrainment Coefficient of Acoustically Pulsed Axisymmetric Free Air Jets

1992 ◽  
Vol 114 (2) ◽  
pp. 409-415 ◽  
Author(s):  
P. J. Vermeulen ◽  
P. Rainville ◽  
V. Ramesh
Keyword(s):  
Strouhal Number ◽  
Excitation Power ◽  
Axial Distance ◽  
Nozzle Orifice ◽  
Air Jets ◽  
Air Jet ◽  
Free Air ◽  
Direct Measurements ◽  
Entrainment Coefficient ◽  
Initial Zone

Novel direct measurements of the entrainment coefficient in the initial zone of a pulsating air jet have been successfully accomplished. A series of pulsating air jets flowing from different nozzle orifice sizes into surrounding air were investigated for the effects of jet axial length, excitation power, and Strouhal number. The entrainment coefficient of the excited jet varied strongly with axial distance downstream of the orifice exit plane and with pulsation strength. The acoustic drive considerably increased the entrainment coefficient by up to 4.6 times at 10 diameters downstream of the nozzle. There was only a tendency for the entrainment coefficient to increase with the Strouhal number and hence an optimum Strouhal number for jet response was not found.

scholarly journals Measurements of the Entrainment Coefficient of Acoustically Pulsed Axisymmetric Free Air Jets

1991 ◽  
Author(s):  
P. J. Vermeulen ◽  
P. Rainville ◽  
V. Ramesh
Keyword(s):  
Strouhal Number ◽  
Excitation Power ◽  
Axial Distance ◽  
Nozzle Orifice ◽  
Air Jets ◽  
Air Jet ◽  
Free Air ◽  
Direct Measurements ◽  
Entrainment Coefficient ◽  
Initial Zone

Novel direct measurements of the entrainment coefficient in the initial zone of a pulsating air jet have been successfully accomplished. A series of pulsating air jets flowing from different nozzle orifice sizes into surrounding air were investigated for the effects of jet axial length, excitation power and Strouhal number. The entrainment coefficient of the excited jet varied strongly with axial distance downstream of the orifice exit plane and with pulsation strength. The acoustic drive considerably increased the entrainment coefficient by up to 4.6 times at 10 diameters downstream of the nozzle. There was only a tendency for the entrainment coefficient to increase with the Strouhal number and hence an optimum Strouhal number for jet response was not found.

HALF-LIVES OF Rb94, Sr94, Y94, Rb93, Sr95, Y95

1961 ◽  
Vol 39 (3) ◽  
pp. 675-680 ◽  
Author(s):  
K. Fritze ◽  
T. J. Kennett ◽  
W. V. Prestwich
Keyword(s):  
Fission Product ◽  
Half Life ◽  
Strontium Isotopes ◽  
Upper Limit ◽  
Direct Measurements

The existence of a new rubidium isotope, Rb94, has been established and its half-life measured. The half-life of this fission product was determined using the technique of timed precipitations. The value obtained for Rb94 was 2.9 ± 0.3 seconds. With this same technique only an upper limit of 2.5 seconds could be assigned to Rb95. The half-lives of the strontium and yttrium daughters were also determined. The strontium isotopes were studied both by timed precipitations and direct measurements. The half-lives of Sr94 and Sr95 were found to be 1.36 ± 0.06 minutes and 0.8 ± 0.15 minute, respectively. Direct measurements lead to half-lives of 20.35 ± 0.20 minutes for Y94 and 10.9 ± 0.2 minutes for Y95.

Coherence between large-scale jet-mixing structure and its pressure field

1982 ◽  
Vol 116 ◽  
pp. 31-57 ◽  
Author(s):  
M. R. Davis
Keyword(s):  
Strouhal Number ◽  
Large Scale ◽  
Pressure Field ◽  
Large Scale Structure ◽  
Harmonic Excitation ◽  
Scale Structure ◽  
Exit Plane ◽  
Cross Sectional ◽  
Potential Core ◽  
Jet Mixing

A schlieren system has been arranged to sense the total fluctuation over a cross-section of the flow and thus becomes very sensitive to large-scale azimuthally coherent structures in the flow. For a natural unexcited jet it is found that there is a concentration of the large-scale structure at a characteristic Strouhal number which is not sensitive to the beam thickness and which reduces progressively with distance from the nozzle. This large-scale structure exhibits a coherence of over 70 % with the near-field pressure and convects at between 75 % and 95 % of the jet velocity. The coherence between the potential core-pressure field and the large-scale structure downstream increases rapidly with distance from the nozzle exit plane, rather limited coherence being found at the exit plane for these observations at a jet-exit Mach number Mj = 0·7. Movement of a central microphone from x = 0 to x = 2D introduced a solid centre body over the first 2·5 diameters of flow and gave rise to a set of discrete components in the flow structure in the range 0.6 < S < 1·4.With harmonic excitation at S = 1·12 a subharmonic at S = 0·55 occurs at x/D = 3 and a second at S = 0.26, x/D = 6. The flow cross-sectional-average sensing thus appears to show up the vortex-pairing mechanism at greater distances from the nozzle than is easily detectable by other means. Under strong impulse excitation a set of discrete components was observed in a transient response extending over times of 400D/Uj. These had a strongest component which decreases more rapidly in Strouhal number with distance than that associated with natural or harmonically excited conditions.

Graves'-Basedow disease in pregnancy

2015 ◽  
Vol 54 (03) ◽  
pp. 106-111 ◽  
Author(s):  
S. L. Andersen ◽  
P. Laurberg
Keyword(s):  
Side Effects ◽  
Birth Defects ◽  
Thyroid Dysfunction ◽  
National Study ◽  
Antithyroid Drugs ◽  
Upper Limit ◽  
Special Concern ◽  
Maternal Thyroid ◽  
Toxic Reactions ◽  
Serum Tsh

SummaryThyroid hormones are essential development factors and maternal thyroid dysfunction may cause pregnancy complications and diseases in the fetus/child. In the present review we discuss new data on the incidence of Graves'-Basedow disease (GBD) in and around pregnancy, and how hyperthyroidism may affect the risk of spontaneous abortion and stillbirth.A special concern in pregnant women is the potential side effects from the use of antithyroid drugs (ATDs). One type of side effects is the allergic/toxic reactions to the drugs, which seem to be similar in and outside pregnancy, and another is that ATDs tend to over treat the fetus when the mother with GBD is made euthyroid. To avoid fetal hypothyroidism, the lowest possible ATD dose should be used to keep maternal thyroid function at the upper limit of normality with low serum TSH. Birth defects after the use of methimazole (MMI) (or its prodrug carbimazole) have been considered to be very rare, and no risk has previously been associated with the use of propylthiouracil (PTU). However, a recent Danish national study found that 1/30 of children exposed to MMI in early pregnancy had birth defects associated with this, and many defects were severe. PTU exposure was associated with defects in 1/40, and these defects were less severe. Proposals are given on how to reduce the risk of ATD associated birth defects.

Quantitative Radioisotope Measurement of Duodenogastric Reflux in Patients with Ulcer or Gastrectomized for Ulcer

1985 ◽  
Vol 24 (03) ◽  
pp. 107-110
Author(s):  
M. Pääkkönen ◽  
S. Aukee ◽  
K. Korhonen ◽  
A. Pääkkönen ◽  
E. Länsimies ◽  
...  
Keyword(s):  
Gamma Camera ◽  
Background Activity ◽  
Bile Reflux ◽  
Duodenogastric Reflux ◽  
Upper Limit ◽  
Visual Evidence ◽  
Biochemical Measurement

SummaryIn this work the duodenogastric reflux was quantified as the amount of radioactivity entering the stomach after an i.v. administration of 99mmTc-HIDA in ulcer patients and in patients who had undergone BI gastrectomy. The results were compared with visual evidence of gastric activity in the gamma camera images and biochemical determination of gastric bile reflux. The method is useful in quantifying the reflux if the activity is above the background activity. It allows the determination of an upper limit for the reflux when the reflux is evident visually. Only two or three images are needed for the quantitation. No correlation was found between biochemical measurement of fasting bile reflux in the stomach and radioisotopic quantification.

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