Investigation of The Thermocapillary Flow in A Liquid Bridge subject to A Non-uniform Rotating Magnetic Field
The effect of an external non-uniform rotating magnetic field (RMF) on the thermocapillary flow in a liquid bridge under microgravity is studied numerically. The thermocapillary flow subject to a non-uniform RMF (7mT, 25Hz) is investigated over a range of Marangoni numbers (15-40). The results indicate that, in comparison with the thermocapillary flow without the magnetic field, the maximum tangential velocity is greatly enhanced and the maximum axial velocity is reduced significantly due to the effect of the non-uniform RMF. As a consequence, the thermocapillary flow remains steady and approximately axisymmetric under the effect of the non-uniform RMF. These results demonstrate that a non-uniform RMF can be used as an effective method to control the thermocapillary flow.
Numerical study of the unstable thermocapillary flow in a silicon float zone under μ–g condition
Abstract In this work, the problem of the hydrodynamic instabilities of the thermocapillary flow inside a Silicon ( Pr =0.016) float zone supported by a pair of coaxial disks and operating under μ – g conditions has been investigated. The system of the conservation equations corresponding to a three-dimensional transient model was directly solved by employing a finite control volumes method fully-implicit in time and a staggered spatial mesh in the cylindrical coordinates system. Results have shown that for a low Marangoni number or a low temperature difference between the disks, the flow remains steady and consists of a perfectly axisymmetrical toroidal structure with the vortex center located beneath the free surface near the cold disk. Beyond the first critical Marangoni number, say Ma cr 1 ≈48, the transition from the axisymmetrical to the steady three-dimensional state has been observed. The flow structure consists of a drastically distorted torus with its vortex centers displaced both radially and axially and is located along a ‘saddle-like’ curve. At the second critical Marangoni number, say Ma cr 2 ≈80, the transition from this three-dimensional-steady-state to the three-dimensional-oscillatory state occurs. Under the effects of some azimuthally travelling instabilities, the entire velocity and temperature fields rotate around the main axis; and a dependent variable varies periodically both in time and space. The flow instabilities, which appear similar to those of the theoretical ‘unstable vortex ring’, are believed to be of the hydrodynamic origin. A detailed description of the internal flow structure and its dynamic behavior as well as a comparison with the previous numerical and experimental data have been given.
First Insights into the Draft Genome Sequence of the Endophyte Paenibacillus amylolyticus Strain GM1FR, Isolated from Festuca rubra L.
ABSTRACT Paenibacillus amylolyticus strain GM1FR is an endophyte isolated from aerial plant tissues of Festuca rubra L. Here, we report the draft genome sequence (7.3 Mb) of GM1FR containing 6,241 protein-coding genes, some of which are potentially involved in plant growth promotion and biocontrol.