Grid adaption for bluff bodies

Methods of grid adaptation are reviewed and a method is developed with the capability of adaptation to several flow variables. This method is based on a variational approach and is an algebraic method which does not require the solution of partial differential equations. Also the method was formulated in such a way that there is no need for any matrix inversion. The method is used in conjunction with the calculation of hypersonic flow over a blunt nose. The equations of motion are the compressible Navier-Stokes equations where all viscous terms are retained. They are solved by the MacCormack time-splitting method and a movie was produced which shows simulataneously the transient behavior of the solution and the grid adaptation. The results are compared with the experimental and other numerical results

Topology and grid adaption for high-speed flow computations

This study investigates the effects of grid topology and grid adaptation on numerical solutions of the Navier-Stokes equations. In the first part of this study, a general procedure is presented for computation of high-speed flow over complex three-dimensional configurations. The flow field is simulated on the surface of a Butler wing in a uniform stream. Results are presented for Mach number 3.5 and a Reynolds number of 2,000,000. The O-type and H-type grids have been used for this study, and the results are compared together and with other theoretical and experimental results. The results demonstrate that while the H-type grid is suitable for the leading and trailing edges, a more accurate solution can be obtained for the middle part of the wing with an O-type grid. In the second part of this study, methods of grid adaption are reviewed and a method is developed with the capability of adapting to several variables. This method is based on a variational approach and is an algebraic method. Also, the method has been formulated in such a way that there is no need for any matrix inversion. This method is used in conjunction with the calculation of hypersonic flow over a blunt-nose body. A movie has been produced which shows simultaneously the transient behavior of the solution and the grid adaption

Superconductivity-driven magnetization modulation in YBa2Cu3O7-{\delta} /SrTiO3/La0.67Sr0.33MnO3 heterostructures

Using spin polarized neutron reflectivity experiments, we demonstrate an unusual proximity behaviour when the superconductor (SC) and the ferromagnet (FM) are coupled through an insulator (I) in YBa2Cu3O7-{\delta} (SC)/SrTiO3 (I)/La0.67Sr0.33MnO3 (FM) heterostructures. We have observed an unexpected magnetic modulation at the interface region of the FM below the superconducting transition temperature. The magnetization of the FM layer at the I/FM interface was drastically reduced as compared to the magnetization in the rest of the FM layer. This result indicates that the Cooper pairs tunnel across the insulator and interact with the local magnetization at the interface region (extending ~ 30 {\AA}) of the FM causing modification of the magnetization at the interface. This unexpected magnetic behavior cannot be explained on the basis of the existing theoretical models. However, the length scale associated here clearly suggests the long range proximity effect as a result of tunneling of Cooper pairs.Comment: 6 figure

Antiferromagnetic Coupling between Surface and Bulk Magnetization and Anomalous Magnetic Transport in Electro-deposited Co Film

We report an interesting magnetic behavior of a Co film (thickness ~ 350 {\AA}) grown on Si/Ti/Cu buffer layer by electro-deposition (ED) technique. Using depth sensitive X-ray reflectivity and polarized neutron reflectivity (PNR) we observed two layer structures for the Co film grown by ED with a surface layer (thickness ~ 100 {\AA}) of reduced density (~ 68% of bulk) compared to rest of the Co film (thickness ~ 250 {\AA}). The two layer structure is consistent with the histogram profile obtained from atomic force microscope (AFM) of the film. Interestingly, using PNR, we found that the magnetization in the surface Co layer is inversely (antiferomagnetically) coupled (negative magnetization for surface Co layer) with the rest of the Co layer for the ED grown film. While we compare PNR result for a Co film of similar layered structure grown by sputtering, the film showed a uniform magnetization as expected. We also show that the depth dependent unusual magnetic behavior of ED grown Co film may be responsible for anomalous anisotropic magnetoresistance observed in low field in this film as compared to the Co film grown by sputtering. Combining X-ray scattering, AFM, superconducting quantum interface device magnetometry (SQUID), PNR and magneto-transport measurements we attempted to correlate and compare the structural, magnetic and morphological properties with magneto-transport of Co films grown by ED and sputtering. The study indicates that the interesting surface magnetic property and magneto-transport property of the ED film is caused by its unique surface morphology

2p3/2 –13x–1–3x–13d–1 X-ray satellites spectra in the Lα1 region of 4d transition elements

The X-ray satellite spectra arising due to 2p3/2–13x–1–3x–13d–1 (x = s, p, d) transition array, in elements with Z = 40 to 48, have been calculated, using available Hartree-Fock-Slater (HFS) data on 1s–1–2p–1 3x – and 2p3/2–1–3x–1,3x–1 Auger transition energies. The relative intensities of all the possible transitions have been estimated by considering cross – sections for the Auger transitions simultaneous to a hole creation and then distributing statistically the total cross sections for initial two hole states 2p3/2–1–3x–1 amongst various allowed transitions from these initial states to 3x–1 3d–1 final states by Coster-Kronig (CK) and shake off processes. In both these processes initial single hole creation is the prime phenomenon. Each transition has been assumed to give rise to a Gaussian line and the overall spectrum has been computed as the sum of these Gaussian curves. The calculated spectra have been compared with the measured satellite energies in La1 spectra. Their intense peaks have been identified as the observed satellite lines. The peaks in the theoretical satellite spectra were identified as the experimentally reported satellites a3, a4 and a5, which lie on the high-energy side of the La1 dipole line.Author Affiliation: Surendra Poonia and S N Sonib 1.Division of Natural Resources and Environment, Central Arid Zone Research Institute, Jodhpur-342 003, Rajasthan, India bX-ray Laboratory, Physics Department, Jai Narain Vyas University, Jodhpur-342 005, Rajasthan, India E-mail : [email protected] of Natural Resources and Environment, Central Arid Zone Research Institute, Jodhpur-342 003, Rajasthan, India bX-ray Laboratory, Physics Department, Jai Narain Vyas University, Jodhpur-342 005, Rajasthan, Indi