A new method to evaluate force constants from experimental spectral data

An iterative procedure is proposed to facilitate the determination of molecular vi-brational force constants from the experimental fundamental frequencies. Proper restrictions are introduced to the force constants based on physical considerations for getting reasonable results. The experimental data of Coriolis coupling coefficients and isotopic frequency shifts are utilized to reduce the uncertainty of the calculated force constants when they are available. A series of various kinds of molecules have been calculated by this method and the results are satisfactory.     

Study of force-dependent and time-dependent transition of secondary flow in a rotating straight channel by the lattice Boltzmann method

A numerical study using the lattice Boltzmann method has been carried out for flow through a rotating straight channel with a rectangular cross section. With different forces applied, the secondary flow exhibits two-cell states, four-cell states or six-cell states at a range of low rotational Reynolds number, however, within which only the two-cell states have been commonly reported. In addition to the force-dependent flow transition, a time-dependent flow transition of the secondary flow among two-cell states, four-cell states and six-cell states is also discovered during flow development. These newly found flow transitions and their regulations by force application have been analyzed. Based on numbers of case studies, it is found that a dimensionless number, the ratio of the driving pressure gradient to the centrifugal force, regulates such flow transitions. This study not only releases new phenomena of flow transition, but also indicates new applications in flow control, particle separation and heat transfer.     

The high-resolution infrared spectrum of thiophene between 600 and 1200 cm: A spectroscopic and theoretical study of the fundamental bands ν6, ν7, ν13, and the c-Coriolis interacting dyad ν5, ν19

The Fourier transform infrared spectrum of gaseous thiophene, C₄H₄S, has been recorded in the 600-1200 cm⁻¹ spectral region with a resolution of ca. 0.0030 cm⁻¹. Five fundamental bands ν₁₃ (B₁, 712.1 cm⁻¹), ν₇ (A₁; 840.0 cm⁻¹), ν₆ (A₁; 1036.4 cm⁻¹), ν₅ (A₁; 1081.5 cm⁻¹) and ν₁₉ (B₂; 1084.0 cm⁻¹) have been analysed by the standard Watson model (A-reduction). Ground state rotational and quartic centrifugal distortion constants have been obtained from a simultaneous fit of ground state combination differences from four of these bands and previous microwave transitions. Upper state spectroscopic constants have been obtained for all five bands from single band fits using the Watson model. A strong c-Coriolis resonance perturbs the close lying ν₅ and ν₁₉ bands. We have analysed this dyad system by a model including first and second order Coriolis resonance using the theoretically predicted Coriolis coupling constant . From this analysis we locate the previously unobserved ν₁₉ band at 1083.969 cm⁻¹. The rotational constants, ground state quartic centrifugal distortion constants, anharmonic frequencies, and vibration-rotational constants (α-constants) predicted by quantum chemical calculations using a cc-pVTZ basis with B3LYP methodology, are compared with the present experimental data, where there is generally good agreement. A complete set of anharmonic frequencies and α-constants for all fundamental levels of the molecule is given.     

Drift of spheres in a rotating fluid

The drift of spheres in a rotating fluid is investigated. The problem is studied experimentally and numerically using the Galerkin method. It is shown that for small angular velocities of the fluid Ω the drift velocity of the spheres is almost independent of Ω, but once a certain threshold value Ω_* is attained the drift velocity rapidly decreases. The experimental dependence of the translational velocity of the sphere on the fluid angular velocity is explained on the basis of a theoretical analysis.     

Experimental investigation of natural convective flows in slowly rotating wide spherical shells

Experimental results are presented on natural convection in a spherical shell of inner and outer radii r ₁ = 14 mm and r ₂ = 35 mm, with the inner sphere cooled and the outer sphere heated. The fluids filling the shell are two different silicon oils having Prandtl numbers 39 and 233. Both spheres are fixed together and can be rotated. In the studied regime, both Coriolis and centrifugal forces become significant. For sufficiently small Rayleigh numbers the resulting flow pattern is axisymmetric and steady, consisting of a plume descending from the south pole of the inner sphere, and returning in the equatorial regions. For greater Rayleigh numbers the flow becomes non-axisymmetric, with azimuthal modes m = 2 to 4 arising. We map out the critical Rayleigh number for the onset of these different modes, and consider how they vary with increasingly rapid overall rotation. Detailed flow measurements are done by converting a standard 2D particle image velocimetry system into a scanning quasi-3D PIV system.     

Allowance for resonances in solving inverse and direct spectroscopic problems in an anharmonic approximation. A scheme of processing for experimental data

The most important aspects in solving inverse and direct spectroscopic problems in the second order of perturbation theory in the presence of Coriolis, Fermi, and Darling-Dennison resonances are discussed. A scheme for obtaining unperturbed values of spectroscopic parameters is suggested which has some advantages over that proposed earlier in [6]. It is believed that this information can be useful to specialists in the field of applied spectroscopy. Saratov State Technical University, 77, Politechnicheskaya St., Saratov, 410054, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 249–255, March–April, 1997.     

A finite element approximation of steady flow through a rotating non-aligned straight tube

A finite element solution is developed for a penalty function formulation of the equations which govern the steady motion of a Newtonian fluid through a pipe that rotates about an axis not parallel to its own. The motion in this system is driven by the Coriolis acceleration, which has components in the axial direction as well as in the transverse plane of the pipe. The relative magnitudes of these components significantly affect the qualitative and quantitative nature of the primary and secondary flow field. The present results compare favourably with those of previously reported experimental and theoretical studies over a wide range of flow regimes.     

High resolution analysis of the ν12 and ν17 fundamental bands of acrolein, CH2CHCHO, in the 600 cm region

Synchrotron radiation from the new Canadian Light Source facility has been used to obtain a high resolution (0.0012 cm⁻¹) absorption spectrum of acrolein vapor in the 550-660 cm⁻¹ region. Almost 2000 transitions have been included in a detailed analysis of the ν₁₂ (∼564 cm⁻¹) and ν₁₇ (∼593 cm⁻¹) fundamental bands which yielded precise values for the band origins, rotational and centrifugal distortion parameters. The analysis included the a- and b-type Coriolis interactions connecting ν₁₂ and ν₁₇, as well as an a-type Coriolis interaction between ν₁₇ and a “dark” perturbing state, identified as 4ν₁₈. We believe that this is the first high resolution infrared study of acrolein.