Dynamical Behaviour of Cryogenic Helium in a Partially Filled Dewar in Microgravity

1996 ◽  
Vol 210 (3) ◽  
pp. 221-230
Author(s):  
R J Hung ◽  
H L Pan
Keyword(s):  
Temporal Evolution ◽  
Rotation Speed ◽  
Spherical Shape ◽  
Dynamical Behaviour ◽  
Constant Angular Velocity ◽  
Microgravity Environment ◽  
Fluid Density ◽  
Cryogenic Helium ◽  
Helium Ii ◽  
Bubble Deformation

The temporal evolution of a spherically shaped bubble sitting to one side of a dewar at rest initially, and subsequently spun up to a constant angular velocity, is investigated. The time-dependent deformation of the bubble, which starts to elongate from a spherical shape, to wrap around the inner dewar wall, and finally to complete encirclement of the dewar wall, is numerically studied and simulated. Some similarity parameters are considered to study the bubble wrapping around the dewar wall. Examples are given to illustrate this problem which is important in the understanding of how surface tension, rotation speed, fluid density, contact angle, etc. affect the bubble deformation for the case of cryogenic helium II in a microgravity environment.

Electron dynamics in one-dimensional double layers

1985 ◽  
Vol 34 (2) ◽  
pp. 271-288 ◽  
Author(s):  
Takashi Yamamoto
Keyword(s):  
Double Layer ◽  
Temporal Evolution ◽  
Dynamical Behaviour ◽  
Double Layers ◽  
Electron Dynamics ◽  
Nonlinear Scattering ◽  
Plasma Oscillations ◽  
One Dimensional ◽  
Simulation Results ◽  
Double Layer Thickness

By numerical simulations, the dynamical behaviour of the electrons in one-dimensional double layers is studied. The simulation results show that at least one third of the electrons emitted at the low-potential boundary of the simulation system are reflected back before passing through the double layers. Such reflexion is due to (i) quasi-linear or nonlinear scattering by plasma oscillations and (ii) ambipolar potentials observed around the potential front of the localized double layer. The whole temporal evolution of the localized double layers are also presented. In particular, we attempt to explain the steepening and collapsing of the localized double layers in terms of the formula for the double-layer thickness.

scholarly journals Effects of simulated microgravity on rice (MR219) growth and yield

2018 ◽  
Vol 14 (2) ◽  
pp. 278-283 ◽  
Author(s):  
Nur Athirah Zulkifli ◽  
Teoh Chin Chuang ◽  
Ong Keat Khim ◽  
Ummul Fahri Abdul Rauf ◽  
Norliza Abu Bakar ◽  
...  
Keyword(s):  
Simulated Microgravity ◽  
Rotation Speed ◽  
Microgravity Condition ◽  
Blast Disease ◽  
Growth And Yield ◽  
Microgravity Environment ◽  
Rice Seed ◽  
Yield Parameters ◽  
Rice Tungro Disease ◽  
Rice Seeds

Rice (Oryza sativa L.) is a staple food in many Asian countries with an ever increasing demand. However, the production of high quality rice seeds is insufficient to meet this demand. Research on plant growth in space related to the exposure of a microgravity environment are rare, costly and time-limited. Similar experiments can be conducted on the ground to simulate the microgravity condition using a 2-D clinostat which compensates for the unilateral influence of gravity. This study was conducted to establish a simple and cost effective technique to enhance the quality of the Malaysian rice seed variety MR 219 by using a 2-D clinostat and to determine the effects of simulated microgravity on the growth and yield of the rice seeds. The experiments were performed at different rotation speeds (2 rpm and 10 rpm) for 10 days at room temperature. The rice growth and yield parameters were measured every 2 weeks and at harvest time (day 110), respectively.  The data were analysed using the MINITAB statistical software package. The mean value estimates of the parameters obtained under different conditions were compared using analysis of variance (ANOVA) with the Tukey test for multiple comparisons using a 0.05 significance level. Significant differences in the number of tiller, stem width , chlorophyll content , weight of grains and panicles and total grain weight per plant were identified at rotation speed 10 rpm  when compared to rotation speed 2 rpm and control. The highest means were mainly obtained under 10 rpm clinorotated rice seeds. In general, plants grown from 10 rpm clinorotated seeds are also more resistant to rice diseases (rice blast disease, rice tungro disease and hopper burn). These results suggest that simulated microgravity using a 2-D clinostat affected several rice (MR219) growth and yield parameters significantly. 

scholarly journals Spin: Ubiquitous, Fundamental, Purposeful: Its Complementary Interactions with Gravity

2020 ◽  
Vol 4 (3) ◽  
pp. p1
Author(s):  
Puthalath Koroth Raghuprasad
Keyword(s):  
Rotation Speed ◽  
Spherical Shape ◽  
Axial Rotation ◽  
Small Satellites ◽  
Fundamental Particles ◽  
Close Relationship ◽  
The Galaxy ◽  
Synchronous Rotation ◽  
Celestial Bodies ◽  
Complementary Interactions

In a prior article we explained how axial spin of celestial bodies interact with mutual gravitation in the phenomenon of synchronous rotation of our moon and the major moons of the gas giants. We also showed how the same complementary interactions could explain both the nonsynchronous (regular orbits) and the negative rotations in Venus, Uranus and Pluto, as well as in the peripheral small satellites of the gas giants. This paper expands on that theme and identifies the various other areas in which these two fundamental and ubiquitous forces cooperate to bring about many other phenomena in the larger universe. Prominent among these phenomena is the role played by the mother bodies’ axial rotation in determining the direction of the orbital motion of their satellite bodies. The other effects include the appearance and maintenance of the spherical shape of large celestial bodies, generation of magnetism in planets, their respective roles in the formation of solar nebulae and proto-planetary disks, and the flattened profile of spiral and elliptical galaxies. Another important finding reported in this paper is the close relationship that exists between the size of planets, as well as the stars, with their axial rotation speeds. This increase of axial rotation speed of celestial bodies in direct proportion to the mass of those bodies, we believe serves to counteract the inward thrust of gravity, in exact proportions and thus help maintain the roughly spherical contour of those bodies. This finding even extends to spiral galaxies, where the axial rotation speed seems to be positively related to the size of the galaxy. This phenomenon and others suggest that spin is a fundamental and purposeful property of matter. Thus, in this paper we stress the important contributions made by the collaborative interactions between the ubiquitous gravity and spin in matter at the level of the fundamental particles, as well as in large celestial bodies, including the largest units in the universe, the galaxies.

scholarly journals The three-dimensional transition in the flow around a rotating cylinder

2008 ◽  
Vol 607 ◽  
pp. 1-11 ◽  
Author(s):  
R. EL AKOURY ◽  
M. BRAZA ◽  
R. PERRIN ◽  
G. HARRAN ◽  
Y. HOARAU
Keyword(s):  
Rotation Rate ◽  
Critical Reynolds Number ◽  
Rotation Speed ◽  
Three Dimensional ◽  
Rotating Cylinder ◽  
Constant Angular Velocity ◽  
Three Dimensional Flow ◽  
Rotation Rates ◽  
Proper Orthogonal ◽  
Rate Suppression

The flow around a circular cylinder rotating with a constant angular velocity, placed in a uniform stream, is investigated by means of two- and three-dimensional direct numerical simulations. The successive changes in the flow pattern are studied as a function of the rotation rate. Suppression of vortex shedding occurs as the rotation rate increases (>2). A second kind of instabilty appears for higher rotation speed where a series of counter-clockwise vortices is shed in the upper shear layer. Three-dimensional computations are carried out to analyse the three-dimensional transition under the effect of rotation for low rotation rates. The rotation attenuates the secondary instability and increases the critical Reynolds number for the appearance of this instability. The linear and nonlinear parts of the three-dimensional transition have been quantified by means of the amplitude evolution versus time, using the Landau global oscillator model. Proper orthogonal decomposition of the three-dimensional fields allowed identification of the most energetic modes and three-dimensional flow reconstruction involving a reduced number of modes.

scholarly journals The dynamical evolution of Be star disks

2010 ◽  
Vol 6 (S272) ◽  
pp. 396-397
Author(s):  
Xavier Haubois ◽  
Alex C. Carciofi ◽  
Atsuo T. Okazaki ◽  
Jon E. Bjorkman
Keyword(s):  
Temporal Evolution ◽  
Three Dimensional ◽  
Dynamical Evolution ◽  
Computer Code ◽  
Diffusion Problem ◽  
Dynamical Behaviour ◽  
Line Profiles ◽  
Different Types ◽  
Dynamical Parameters ◽  
Be Star

AbstractWe present a novel theoretical tool to analyze the dynamical behaviour of a Be disk fed by non-constant decretion rates. It is mainly based on the computer code HDUST, a fully three-dimensional radiative transfer code that has been successfully applied to study several Be systems so far, and the SINGLEBE code that solves the 1D viscous diffusion problem. We have computed models of the temporal evolution of different types of Be star disks for different dynamical scenarios. By showing the behaviour of a large number of observables (interferometry, polarization, photometry and spectral line profiles), we show how it is possible to infer from observations some key dynamical parameters of the disk.

Macrostructure and microphysics of Saturn's E-ring

1984 ◽  
Vol 75 ◽  
pp. 607-613 ◽  
Author(s):  
Kevin D. Pang ◽  
Charles C. Voge ◽  
Jack W. Rhoads
Keyword(s):  
Size Distribution ◽  
Spherical Shape ◽  
Mie Scattering ◽  
Narrow Size Distribution ◽  
Electrostatic Levitation ◽  
Volcanic Origin ◽  
Micron Diameter

Abstract.All observed optical and infrared properties of Saturn's E-ring can be explained in terms of Mie scattering by a narrow size distribution of ice spheres of 2 - 2.5 micron diameter. The spherical shape of the ring particles and their narrow size distribution imply a molten (possibly volcanic) origin on Enceladus. The E-ring consists of many layers, possibly stratified by electrostatic levitation.

On the Shape of Field-Ion Emitters

1976 ◽  
Vol 34 ◽  
pp. 520-521
Author(s):  
H.C. Eaton ◽  
B.N. Ranganathan ◽  
T.W. Burwinkle ◽  
R. J. Bayuzick ◽  
J.J. Hren
Keyword(s):  
Grain Boundary ◽  
Spherical Shape ◽  
Theoretical Strength ◽  
Evaporation Process ◽  
Field Evaporation ◽  
Geometric Information ◽  
Field Ion Microscopy ◽  
Considerable Error ◽  
True Shape ◽  
Ion Microscopy

The shape of the emitter is of cardinal importance to field-ion microscopy. First, the field evaporation process itself is closely related to the initial tip shape. Secondly, the imaging stress, which is near the theoretical strength of the material and intrinsic to the imaging process, cannot be characterized without knowledge of the emitter shape. Finally, the problem of obtaining quantitative geometric information from the micrograph cannot be solved without knowing the shape. Previously published grain-boundary topographies were obtained employing an assumption of a spherical shape (1). The present investigation shows that the true shape deviates as much as 100 Å from sphericity and boundary reconstructions contain considerable error as a result.Our present procedures for obtaining tip shape may be summarized as follows. An empirical projection, D=f(θ), is obtained by digitizing the positions of poles on a field-ion micrograph.

Nonlinear dynamics of a shell encapsulated microbubble near solid boundary in an ultrasonic field

2020 ◽  
Vol 14 (3) ◽  
pp. 7235-7243
Author(s):  
N.M. Ali ◽  
F. Dzaharudin ◽  
E.A. Alias
Keyword(s):  
Oscillation Amplitude ◽  
Ultrasonic Field ◽  
Dynamical Behaviour ◽  
Ultrasound Contrast Agents ◽  
Chaotic Behaviour ◽  
Solid Boundary ◽  
Driving Frequency ◽  
Pressure Amplitude ◽  
Radial Expansion ◽  
Therapeutic Delivery

Microbubbles have the potential to be used for diagnostic imaging and therapeutic delivery. However, the transition from microbubbles currently being used as ultrasound contrast agents to achieve its’ potentials in the biomedical field requires more in depth understanding. Of particular importance is the influence of microbubble encapsulation of a microbubble near a vessel wall on the dynamical behaviour as it stabilizes the bubble. However, many bubble studies do not consider shell encapsulation in their studies. In this work, the dynamics of an encapsulated microbubble near a boundary was studied by numerically solving the governing equations for microbubble oscillation. In order to elucidate the effects of a boundary to the non-linear microbubble oscillation the separation distances between microbubble will be varied along with the acoustic driving. The complex nonlinear vibration response was studied in terms of bifurcation diagrams and the maximum radial expansion. It was found that the increase in distance between the boundary and the encapsulated bubble will increase the oscillation amplitude. When the value of pressure amplitude increased the single bubble is more likely to exhibit the chaotic behaviour and maximum radius also increase as the inter wall-bubble distance is gradually increased. While, with higher driving frequency the maximum radial expansion decreases and suppress the chaotic behaviour.

An appraisal of characteristic mechanical properties and microstructure of friction stir welding for Aluminium 6061 alloy – Silicon Carbide (SiCp) metal matrix composite

2019 ◽  
Vol 13 (4) ◽  
pp. 5804-5817
Author(s):  
Ibrahim Sabry
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Metal Matrix Composite ◽  
Matrix Composite ◽  
Metal Matrix ◽  
Welded Joint ◽  
Rotation Speed ◽  
Fusion Welding ◽  
Friction Stir ◽  
Al 6061

It is expected that the demand for Metal Matrix Composite (MMCs) will increase in these applications in the aerospace and automotive industries sectors, strengthened AMC has different advantages over monolithic aluminium alloy as it has characteristics between matrix metal and reinforcement particles.  However, adequate joining technique, which is important for structural materials, has not been established for (MMCs) yet. Conventional fusion welding is difficult because of the irregular redistribution or reinforcement particles.  Also, the reaction between reinforcement particles and aluminium matrix as weld defects such as porosity in the fusion zone make fusion welding more difficult. The aim of this work was to show friction stir welding (FSW) feasibility for entering Al 6061/5 to Al 6061/18 wt. % SiCp composites has been produced by using stir casting technique. SiCp is added as reinforcement in to Aluminium alloy (Al 6061) for preparing metal matrix composite. This method is less expensive and very effective. Different rotational speeds,1000 and 1800 rpm and traverse speed 10 mm \ min was examined. Specimen composite plates having thick 10 mm were FS welded successfully. A high-speed steel (HSS) cylindrical instrument with conical pin form was used for FSW. The outcome revealed that the ultimate tensile strength of the welded joint (Al 6061/18 wt. %) was 195 MPa at rotation speed 1800 rpm, the outcome revealed that the ultimate tensile strength of the welded joint (Al 6061/18 wt.%) was 165 MPa at rotation speed 1000 rpm, that was very near to the composite matrix as-cast strength. The research of microstructure showed the reason for increased joint strength and microhardness. The microstructural study showed the reason (4 %) for higher joint strength and microhardness.  due to Significant   of SiCp close to the boundary of the dynamically recrystallized and thermo mechanically affected zone (TMAZ) was observed through rotation speed 1800 rpm. The friction stir welded ultimate tensile strength Decreases as the volume fraction increases of SiCp (18 wt.%).

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