Dynamic interaction between a circle moving at terminal velocity and the surrounding fluid medium

1972 ◽  
Author(s):  
S. JORDAN ◽  
J. FROMM
Keyword(s):  
Terminal Velocity ◽  
Dynamic Interaction ◽  
Fluid Medium ◽  
Surrounding Fluid

The Fine Structure of the Cockroach Subgenual Organ

1970 ◽  
Vol 28 ◽  
pp. 80-81
Author(s):  
David T. Moran
Keyword(s):  
Fine Structure ◽  
Circulatory System ◽  
Epidermal Cells ◽  
Mechanical Stimuli ◽  
Sense Organs ◽  
Fluid Medium ◽  
Blaberus Discoidalis ◽  
Highly Sensitive ◽  
Surrounding Fluid ◽  
Subgenual Organ

Insects are abundantly endowed with mechanoreceptors, sense organs that transduce mechanical stimuli into nerve impulses. Like most cockroaches, Blaberus discoidalis is highly sensitive to vibrations of the substrate on which it walks. This sensitivity is thought to be due in large part to the subgenual organ — an intricately constructed mechanoreceptor located near the proximal end of the tibia. The exoskeleton of the cockroach is secreted by a layer of epidermal cells which enclose the haemocoele of animal's open circulatory system. The subgenual organ is a thin, fan-shaped flap of tissue which is suspended from the epidermis and occludes much of the dorsal blood space in the hollow leg. It is therefore surrounded by blood on all sides; its position renders it susceptible to minor displacements of the surrounding fluid medium. Highly modified epidermal cells which are packed with hundreds of parallel microtubules support the subgenual organ as a ligament. The cells which compose the bulk of the organ are populated with a few mitochondria and many microtubules.

The Effect of a Surrounding Fluid on Pressure Waves in a Fluid-Filled Elastic Tube

1955 ◽  
Vol 22 (2) ◽  
pp. 227-231
Author(s):  
M. C. Junger
Keyword(s):  
Sound Velocity ◽  
Surrounding Medium ◽  
Elastic Tube ◽  
Pressure Waves ◽  
End Effects ◽  
Fluid Medium ◽  
Phase Velocities ◽  
Radiation Losses ◽  
Surrounding Fluid ◽  
Theory Of Shells

Abstract The analysis of the transmission of pressure waves in a fluid-filled elastic tube has been extended to the case where the tube is surrounded by a fluid medium. The sound pressure inside the tube is the resultant of a number of modes, some of which are nonpropagating, while others propagate at their own characteristic phase velocities. Neglecting end effects, and for continuously generated waves, it is found that only the modes whose velocity is larger than the sound velocity of the surrounding medium radiate sound energy radially outward. These modes will be damped out by radiation losses, while modes having a phase velocity smaller than this sound velocity are propagated without attenuation (if viscous and heat-transfer losses are neglected). Consequently, if the fluid is the same in the surrounding medium and in the tube only the lowest mode, which resembles a plane wave, propagates unattenuated. In any case, the mass-loading of the surrounding fluid lowers the phase velocities of the propagating modes, particularly at intermediate frequencies. It is shown that in this application the membrane theory of shells will lead to incorrect results, even in thin-walled tubes. This is illustrated by comparison with experimental data.

On the instability of small gas bubbles moving uniformly in various liquids

1957 ◽  
Vol 3 (1) ◽  
pp. 27-47 ◽  
Author(s):  
R. A. Hartunian ◽  
W. R. Sears
Keyword(s):  
Surface Tension ◽  
Weber Number ◽  
Gas Bubbles ◽  
Hydrodynamic Pressure ◽  
Terminal Velocity ◽  
Approximate Methods ◽  
Stability Calculation ◽  
Fluid Medium ◽  
Critical Weber Number ◽  
The Stability

The instability of small gas bubbles moving uniformly in various liquids is investigated experimentally and theoretically.The experiments consist of the measurement of the size and terminal velocity of bubbles at the threshold of instability in various liquids, together with the physical properties of the liquids. The results of the experiments indicate the existence of a universal stability curve. The nature of this curve strongly suggests that there are two separate criteria for predicting the onset of instability, namely, a critical Reynolds number (202) and a critical Weber number (1.26). The former criterion appears to be valid for bubbles moving uniformly in liquids containing impurities and in the somewhat more viscous liquids, whereas the latter criterion is for bubbles moving in pure, relatively inviscid liquids.The theoretical analysis is directed towards an investigation of the possibility of the interaction of surface tension and hydrodynamic pressure leading to unstable motions of the bubble, i.e. the existence of a critical Weber number. Accordingly, the theoretical model assumes the form of a general perturbation in the shape of a deformable sphere moving with uniform velocity in an inviscid, incompressible fluid medium of infinite extent. The calculations lead to divergent solutions above a certain Weber number, indicating, at least qualitatively, that the interaction of surface tension and hydrodynamic pressure can result in instabilities of the bubble motion.A subsequent investigation of the time-independent equations, however, shows the presence of large deformations in shape of the bubble prior to the onset of unstable motion, which is not compatible with the approximation of perturbing an essentially spherical bubble. This deformation and its possible effects on the stability calculation are therefore determined by approximate methods. From this it is concluded that the deformation of the bubble serves to introduce quantitative, but not qualitative, changes in the stability calculation.

1960 THE EFFECT OF SURROUNDING FLUID MEDIUM ON STONE FRAGMENTATION DURING SHOCKWAVE LITHOTRIPSY

2010 ◽  
Vol 183 (4S) ◽  
Author(s):  
Carlos Mendez Probst ◽  
Alfonso Fernandez Carreno ◽  
Petar Erdeljan ◽  
Alp Sener ◽  
Maaike Vanjecek ◽  
...  
Keyword(s):  
Shockwave Lithotripsy ◽  
Fluid Medium ◽  
Stone Fragmentation ◽  
Surrounding Fluid

Computations of Buoyancy Driven Motion of a Single Droplet in Another Immiscible Liquid

2017 ◽  
Author(s):  
Shunji Homma ◽  
Tamaki Yoshikawa
Keyword(s):  
Liquid Droplet ◽  
Terminal Velocity ◽  
Immiscible Liquid ◽  
Solid Particles ◽  
Single Droplet ◽  
Drag Coefficients ◽  
Front Tracking Method ◽  
Drag Forces ◽  
Limiting Case ◽  
Surrounding Fluid

Buoyancy driven motion of a single droplet in another quiescent fluid was simulated by a Front-Tracking method. The rising velocity and the projected area of the droplet were obtained in spherical, ellipsoidal, and wobbling regimes. Form and skin drag forces were calculated by integrating pressure distribution and velocity profiles along the interface of the droplet. Drag coefficient was obtained from those values when the rising velocity reached the terminal velocity. The scaling for drag of a liquid droplet was compared with the theoretical model. When the viscosity of the droplets was lower than that of the surrounding fluid, the drag coefficients can be predicted by the model for the limiting case of gas bubbles. When the viscosity of the droplets was larger than that of the surrounding fluid, on the other hand, the drag coefficients can be predicted by the model when solid particles are assumed.

Quality of ram spermatozoa separated with modified swim up method

2018 ◽  
Vol 33 (2) ◽  
pp. 62-70 ◽  
Author(s):  
A Hossain ◽  
MM Islam ◽  
F Naznin ◽  
RN Ferdousi ◽  
FY Bari ◽  
...  
Keyword(s):  
Semen Quality ◽  
Membrane Integrity ◽  
Quality Parameters ◽  
Fluid Medium ◽  
Normal Morphology ◽  
The Mean ◽  
Mass Activity ◽  
Fresh Semen ◽  
Artificial Vagina

Semen was collected from four rams, using artificial vagina and viability%, motility% and plasma membrane integrity% were measured. Fresh ejaculates (n = 32) were separated by modified swim-up separation using modified human tubal fluid medium. Four fractions of supernatant were collected at 15-minute intervals. The mean volume, mass activity, concentration, motility%, viability%, normal morphology and membrane integrity% (HOST +ve) of fresh semen were 1.0 ± 0.14, 4.1 ± 0.1 × 109 spermatozoa/ml, 85.0 ± 1.3, 89.4 ± 1.0, 85.5 ± 0.7, 84.7 ± 0.5 respectively. There was no significant (P>0.05) difference in fresh semen quality parameters between rams. The motility%, viability% and HOST +ve % of first, second, third and fourth fractions were 53.4 ± 0.5, 68.2 ± 0.3, 74.8 ± 0.3 and 65.5 ± 0.4; 55.5 ± 0.4, 66.2 ± 0.4, 74.5 ± 0.3 and 73.6 ± 0.3 and 66.7 ± 0.5, 66.8 ± 0.5, 65.2 ± 0.4 and 74.7 ± 0.5 respectively. The motility%, viability% and membrane integrity% of separated semen samples differed significantly (P<0.05) between four fractions. The mean motility% and viability% were significantly higher (P<0.05) in third fraction (74.8 ± 0.3%), whereas the mean HOST +ve% was significantly higher (P<0.05) in fourth fraction (74.7 ± 0.5). All quality parameters of separated spermatozoa were significantly (P<0.05) lower than that of fresh semen. The pregnancy rates were higher with fresh semen (71%) in comparison to that of separated sample (57%).Bangl. vet. 2016. Vol. 33, No. 2, 62-70

Particle motion with air resistance

2012 ◽  
Vol 8 (1) ◽  
pp. 1-15
Author(s):  
Gy. Sitkei
Keyword(s):  
Basic Equation ◽  
Initial Conditions ◽  
Equation Of Motion ◽  
Terminal Velocity ◽  
Dimensionless Form ◽  
Wood Industry ◽  
Acceptable Error ◽  
General Validity ◽  
Practical Applications ◽  
Air Resistance

Motion of particles with air resistance (e.g. horizontal and inclined throwing) plays an important role in many technological processes in agriculture, wood industry and several other fields. Although, the basic equation of motion of this problem is well known, however, the solutions for practical applications are not sufficient. In this article working diagrams were developed for quick estimation of the throwing distance and the terminal velocity. Approximate solution procedures are presented in closed form with acceptable error. The working diagrams provide with arbitrary initial conditions in dimensionless form of general validity.

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