Dynamic mode decomposition of turbulent cavity flows for self-sustained oscillations

Self-sustained oscillations in a cavity arise due to the unsteady separation of boundary layers at the leading edge. The dynamic mode decomposition method was employed to analyze the self-sustained oscillations. Two cavity flow data sets, with or without self-sustained oscillations and possessing thin or thick incoming boundary layers (Re_D = 12,000 and 3000), were analyzed. The ratios between the cavity depth and the momentum thickness (D/θ) were 40 and 4.5, respectively, and the cavity aspect ratio was L/D = 2. The dynamic modes extracted from the thick boundary layer indicated that the upcoming boundary layer structures and the shear layer structures along the cavity lip line coexisted with coincident frequency space but with different wavenumber space, whereas structures with a thin boundary layer showed complete coherence among the modes to produce self-sustained oscillations. This result suggests that the hydrodynamic resonances that gave rise to the self-sustained oscillations occurred if the upcoming boundary layer structures and the shear layer structures coincided, not only in frequencies, but also in wavenumbers. The influences of the cavity dimensions and incoming momentum thickness on the self-sustained oscillations were examined.     

Synthesis,spectral and structural studies of oxovanadium(IV/V) complexes derived from 2-hydroxyacetophenone-3-hydroxy-2-naphthoylhydrazone: polymorphs of oxovanadium(V) complex [VOL(OCH<Subscript>3</Subscript>)]

Abstract  

Oxovanadium(IV/V) complexes of 2-hydroxyacetophenone-3-hydroxy-2-naphthoylhydrazone (H₂L) have been synthesized and characterized. The complexes were characterized by elemental analyses, IR, electronic and EPR spectra. The oxovanadium(V) complex [VOL(OCH₃)] is crystallized in two polymorphic forms, denoted by 1a and 1b, with space groups Pn2₁a and P_[`1] P_{{\bar{1}}} , respectively. Both have distorted square pyramidal structures.     

Crystal Study of Salicylaldehyde N(4)-Phenylthiosemicarbazone

Abstract The crystal structure of salicylaldehyde N(4)-phenyl thiosemicarbazone is described. The compound crystallizes in the triclinic crystal system, space group P Z = 6, V = 2002.1(5) ?³ with unit cell parameters a = 10.6733(15) ?, b = 13.8856(19) ?, c = 14.052(2) ?, α = 81.851(2)°, β = 77.061(2)° and γ = 83.482(2)°. There are three independent molecules in the asymmetric unit. The crystal structure reveals that the compound exists in the thione form and S1 and N3 are at E configuration to each other with respect to N2–C7 bond. Similarly, S2 and N6 are trans to each other with respect to N5–C21 bond in the second molecule of the asymmetric unit and S3 and N9 are trans to each other with respect to N8–C35 bond in the third molecule of the asymmetric unit. The packing of the molecules in the crystal lattice is stabilized by intermolecular hydrogen bonds. Index Abstract The compound salicylaldehyde N(4)-phenyl thiosemicarbazone crystallizes in the triclinic crystal system, space group P Z = 6, V=2002.1(5) ?³ with unit cell parameters a = 10.6733(15) ?, b = 13.8856(19) ?, c = 14.052(2) ?, α = 81.851(2)°, β = 77.061(2)° and γ = 83.482(2)°. The structure of the compound salicylaldehyde N(4)-phenylthiosemicarbazone     

2‐Hydroxy­acetophenone 4‐phenyl­thio­semicarbazone

The title compound, C₁₅H₁₅N₃OS, exists in the thione form and adopts an E configuration about the hydrazine bond, which is in the Z form with respect to the thiocarbonyl bond. An O—H⋯N intra­molecular hydrogen bond promotes planarity in part of the mol­ecule.     

Synthesis,spectral and EPR studies of oxovanadium(IV) complexes incorporating tridentate ONO donor hydrazone ligands: Structural study of one oxovanadium(V) complex

Five oxovanadium(IV) complexes of 2-hydroxy-4-methoxybenzaldehyde nicotinic acid hydrazone (H₂L¹), 2-hydroxy-4-methoxyacetophenone nicotinic acid hydrazone (H₂L²) and a binuclear oxovanadium(V) complex of H₂L² have been synthesized. These complexes were characterized by different physicochemical techniques like electronic, infrared and EPR spectral studies. The complexes [VOL¹]₂ · H₂O (1) and [VOL²]₂ · H₂O (4) are binuclear and [VOL¹bipy] (2), [VOL¹phen] · 1.5H₂O (3) and [VOL²phen] · 2H₂O (6) are heterocyclic base adducts and are EPR active. In frozen DMF at 77 K, all the oxovanadium(IV) complexes show axial anisotropy with two sets of eight line patterns. The complex [VOL² · OCH₃]₂ (5) is an unusual product and has distorted octahedral geometry, as obtained by X-ray diffraction studies.