A general theory for two- and three-dimensional wall-mode instabilities in boundary layers over isotropic and anisotropic compliant walls

An asymptotic theory is developed for two- and three-dimensional disturbances growing in a two-dimensional boundary layer over a compliant wall. The theory exploits the multideck structure of the boundary layer to derive asymptotic approximations at a high Reynolds number for the perturbation wall pressure and viscous stresses. These quantities can be regarded as driving the wall and, accordingly, the equation(s) of motion for the wall is (are) used as the characteristic equation(s) for finding the eigenvalue(s). The main assumptions are that the amplitude of the disturbance is sufficiently small for linear theory to hold, the Reynolds number is large, the disturbance wavelength is long compared with the boundary-layer thickness, and the critical and viscous wall layers are well separated. The theory was developed to study the travelling-wave flutter instability discussed by Carpenter and Garrad, i.e., the Class B instability of Benjamin and Landahl. Under certain limiting processes both the upper-branch and conventional triple-deck scalings for the Tollmien-Schlichting instability can be obtained with the present approach. Accordingly, the theory also gives a reliable qualitative guide to the effect of anisotropic wall compliance on the Tollmien-Schlichting instability.The theory is applied to various cases including two- and three-dimensional disturbances, developing in boundary layers over isotropic and anisotropic compliant walls. The disturbances can be treated as either temporally or spatially growing. Eigenvalues are very accurately predicted by means of the theory, especially near points of neutral stability. The computational requirements are trivial compared with those required for full numerical solution of the Orr-Sommerfeld equation. For isotropic compliant walls the theory confirms the earlier result of Miles and Benjamin that the phase shift in the disturbance velocity across the critical layer plays a dominant role in destabilization of the Class B travelling-wave flutter through making irreversible energy transfer possible due to the work done by the fluctuating pressure at the wall. The theory elucidates the secondary role played by the phase shift occurring across the wall layer. Viscous effects are much more important for anisotropic compliant walls which admit substantial horizontal, as well as vertical, displacement. For these walls an important mechanism for irreversible energy transfer is the work done by fluctuating shear stress. This almost invariably has a stabilizing effect on the travelling-wave flutter. In addition there is a weaker effect arising from the effect of anisotropic wall compliance on the phase shift across the wall layer. This may be stabilizing or destabilizing.This work was carried out with the support of the Ministry of Defence (Procurement Executive) and the Office of Naval Research and was completed while P.W.C. and J.S.B.G. were on study leave at the Department of Aerospace Engineering, The Pennsylvania State University, and the Department of Mathematics, Iowa State University, Ames, respectively. They would like to express their gratitude to those institutions and the Office of Naval Research for financial support during their study leaves.     

Transitioning from Targeted to Comprehensive Mass Spectrometry Using Genetic Algorithms

Targeted proteomic assays are becoming increasingly popular because of their robust quantitative applications enabled by internal standardization, and they can be routinely executed on high performance mass spectrometry instrumentation. However, these assays are typically limited to 100s of analytes per experiment. Considerable time and effort are often expended in obtaining and preparing samples prior to targeted analyses. It would be highly desirable to detect and quantify 1000s of analytes in such samples using comprehensive mass spectrometry techniques (e.g., SWATH and DIA) while retaining a high degree of quantitative rigor for analytes with matched internal standards. Experimentally, it is facile to port a targeted assay to a comprehensive data acquisition technique. However, data analysis challenges arise from this strategy concerning agreement of results from the targeted and comprehensive approaches. Here, we present the use of genetic algorithms to overcome these challenges in order to configure hybrid targeted/comprehensive MS assays. The genetic algorithms are used to select precursor-to-fragment transitions that maximize the agreement in quantification between the targeted and the comprehensive methods. We find that the algorithm we used provided across-the-board improvement in the quantitative agreement between the targeted assay data and the hybrid comprehensive/targeted assay that we developed, as measured by parameters of linear models fitted to the results. We also found that the algorithm could perform at least as well as an independently-trained mass spectrometrist in accomplishing this task. We hope that this approach will be a useful tool in the development of quantitative approaches for comprehensive proteomics techniques.

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Structure of Some 4f Rare Earth Liquid Metals - A Charged Hard Sphere Approach

A well-established pseodopotential is used to study the structure of some 4f rare earth liquid metals (Ce,Pr, Eu, Gd, Tb, and Yb). The structure factor S(q), pair distribution function g(r), interatomic distance r1, and coordination number n1 are calculated using Charged Hard Sphere (CHS) reference system. To introduce the exchange and correlation effects, the local field correction due to Sarkar et al. (S) is applied. The present investigation is successful in generating the structural information of Ce, Pr, Eu, Gd, Tb, and Yb 4f rare earth liquid metals.     

Some Properties of Si,Ge, and α-Sn Using Pseudopotential Theory

The pseudopotential theory beyond second order with our well establishedsingle parametric model potential is employed to compute total crystalenergy, static bulk modulus, energy band gap at the point X on theJones-zone face and pressure-volume relation (equation of state underpressure) of Si, Ge and α-Sn using Nagy's static local field correction function. The results are compared with those obtained using few other local field correction functions. The present results of total energy are in good agreement with the experimental data. Bulk modulus calculated byNagy's screening function is perfectly matching with the experimentalresults for Ge and α-Sn. Some deviation is found in the value of energy band gap.     

“Synthesis,design and characterization of supramolecular self-assembly of calix[4]resorcinare substituted LCs”

A new class of supramolecular calix[4 (a) Kuang, G.C., Jia, X.R., Teng, M.J., Chen, E.Q., Li, W.S., Ji, Y., Chem Mater. 2012, 24,71–80; (b) Macros, M., Omenat, A., Serrano, J.L., and Ezcurra, A., Adv. Mater. 1992, 4, 285–287.[Crossref], [Web of Science ®] , [Google Scholar], [Google Scholar]]resorcinarene substituted alkoxy side chain (-OC₅H₁₁, -OC₈H₁₇, -OC₁₀H₂₁) has been synthesized and well characterized. These supramolecular compounds were investigated by polarizing optical microscope (POM), differential scanning calorimetry (DSC), thermogravimmetric analysis (TGA) and high-temperature X-ray diffraction studies (XRD). The present synthesized supramolecular derivatives are promising to stabilize the hexagonal columnar phase over a broad thermal range. All the synthesized derivatives showed hexagonal columnar phase at lower temperature and showed enantiotropical nature. Compound 2a with small alkyl spacer on eight side showed higher thermal stability as compare to higher alkyl spacer substituted compounds 2b and compound 2c. These research results suggest that calix[4 (a) Kuang, G.C., Jia, X.R., Teng, M.J., Chen, E.Q., Li, W.S., Ji, Y., Chem Mater. 2012, 24,71–80; (b) Macros, M., Omenat, A., Serrano, J.L., and Ezcurra, A., Adv. Mater. 1992, 4, 285–287.[Crossref], [Web of Science ®] , [Google Scholar], [Google Scholar]]resorcinarene was a good platform to construct bowl-shaped derivatives to exhibits the columnar liquid crystal phase and the observed liquid crystalline properties were greatly effected by the substituted alkoxy side chain on eight side of calix[4 (a) Kuang, G.C., Jia, X.R., Teng, M.J., Chen, E.Q., Li, W.S., Ji, Y., Chem Mater. 2012, 24,71–80; (b) Macros, M., Omenat, A., Serrano, J.L., and Ezcurra, A., Adv. Mater. 1992, 4, 285–287.[Crossref], [Web of Science ®] , [Google Scholar], [Google Scholar]]resorcinarene skeletone. All the synthesized compounds were characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopy.     

Handbook of Compressible Aerodynamics,by Jean Délery

Present knowledge of the constitution, structure and dynamics of the atmospheres of Venus and Jupiter are reviewed in the light of observations and measurements from recent space missions.     

An Analytic Approach for Calculating Absolutely Unstable Inviscid Modes of the Boundary Layer on a Rotating Disk

An analytical treatment of inviscidly absolutely unstable modes is pursued using the long-wavelength asymptotic approach. It is shown using the inviscid Rayleigh scalings in conjunction with the linear critical layer theory that the rotating-disk boundary layer flow undergoes a region of absolute instability for some small azimuthal wave numbers. The analytically calculated branch points for the absolute instability are found to be in good agreement with those obtained via a numerical solution of the inviscid Rayleigh equation.     

Stability of flow past cylinder cascade

The global stability analysis of the two–dimensional incompressible unsteady flow past a circular clinder cascade is studied using linear stability analysis. A new numerical technique is used to find the value of critical Reynolds number that causes the flow to undergo Hopf bifurcation. An attempt has also been made to study the blockage effect on critical Reynolds number and associated Strouhal number. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Global instability computations of separated flows

The primary motivation for the current work is to develop suitable techniques for studying the global instability in many different flows such as that occuring in the subsonic flow past a corner. In this paper we will discuss the methodology and some of the results obtained. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)