A Comparative Study on High Reynolds Number Turbulent Boundary Layers

An increasing number of high quality measurements of turbulent boundary layers at high Reynolds number have been reported in the literature. These measurements come from flows that were established and developed employing different approaches and facilities. It is interesting to assess how the choice of an experimental set-up and the employment of different types of tripping device influence the state of development for such layers. The present study aims to establish, qualitatively, a relationship between mean flow parameters and higher order statistics of the flow, namely, the streamwise turbulence intensity. Detailed mean flow parameters and turbulence intensity profiles for normally tripped layers, in the sense of Coles [4], do not show dependence on the type of tripping device at high Reynolds number. However, there is some evidence indicating that naturally transition flows and artificially tripped layers that are highly perturbed during initial stages of development will not follow similar behaviour. It appears that flows with high Coles' profile parameter, П, will exhibit high levels of turbulence intensity in the outer flow regio

A unified approach for numerical simulation of viscous compressible and incompressible flows over adiabatic and isothermal walls

A new formulation (including the choice of variables, their non-dimensionalization, and the form of the artificial viscosity) is proposed for the numerical solution of the full Navier-Stokes equations for compressible and incompressible flows with heat transfer. With the present approach, the same code can be used for constant as well as variable density flows. The changes of the density due to pressure and temperature variations are identified and it is shown that the low Mach number approximation is a special case. At zero Mach number, the density changes due to the temperature variation are accounted for, mainly through a body force term in the momentum equation. It is also shown that the Boussinesq approximation of the buoyancy effects in an incompressible flow is a special case. To demonstrate the new capability, three examples are tested. Flows in driven cavities with adiabatic and isothermal walls are simulated with the same code as well as incompressible and supersonic flows over a wall with and without a groove. Finally, viscous flow simulations of an oblique shock reflection from a flat plate are shown to be in good agreement with the solutions available in literature

An entropy correction method for unsteady full potential flows with strong shocks

An entropy correction method for the unsteady full potential equation is presented. The unsteady potential equation is modified to account for entropy jumps across shock waves. The conservative form of the modified equation is solved in generalized coordinates using an implicit, approximate factorization method. A flux-biasing differencing method, which generates the proper amounts of artificial viscosity in supersonic regions, is used to discretize the flow equations in space. Comparisons between the present method and solutions of the Euler equations and between the present method and experimental data are presented. The comparisons show that the present method more accurately models solutions of the Euler equations and experiment than does the isentropic potential formulation

V2O5/SiO2 as an efficient catalyst in the synthesis of 5-amino- pyrazole derivatives under solvent free condition

An efficient and facile approach for the synthesis of 5-aminopyrazoles from ketene S,N-acetal and hydrazine hydrate via catalytic reaction under solvent free condition has been described. V2O5/SiO2 as a heterogeneous catalyst was prepared and characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM).               KEY WORDS: One-pot synthesis, 5-Amino-1H-pyrazole, Hydrazine hydrate, Vanadium oxide, Silica Bull. Chem. Soc. Ethiop. 2019, 33(1), 135-142DOI: https://dx.doi.org/10.4314/bcse.v33i1.13

Adrenocortical status in infants and children with sepsis and septic shock

AbstractBackgroundThe benefit from corticosteroids remains controversial in sepsis and septic shock and the presence of adrenal insufficiency (AI) has been proposed to justify steroid use.AimTo determine adrenal state and its relation with outcome in critical children admitted with sepsis to PICU of Cairo University, Children Hospital.MethodsThirty cases with sepsis and septic shock were studied. Cortisol levels (CL) were estimated at baseline and after high-dose short ACTH stimulation in those patients and in 30 matched controls. Absolute AI was defined as basal CL<7μg/dl and peak CL<18μg/dl. Relative AI was diagnosed if cortisol increment after stimulation is <9μg/dl.ResultsOverall mortality of cases was 50%. The mean CL at baseline in cases was higher than that of controls (51.39μg/dl vs. 12.83μg/dl, p=0.000). The mean CL 60min after ACTH stimulation was higher than that of controls (73.38μg/dl vs. 32.80μg/dl, p=0.000). The median of %rise in cases was lower than that of controls (45.3% vs. 151.7%). There was a positive correlation between basal and post-stimulation cortisol with number of system failure, inotropic support duration, mechanical ventilation days, and CO2 level in blood. There was a negative correlation between basal and post stimulation cortisol with blood pH and HCO3.ConclusionRAI is common with severe sepsis/septic shock. It is associated with more inotropic support and has higher mortality. Studies are warranted to determine whether corticosteroid therapy has a survival benefit in children with RAI and catecholamine resistant septic shock

Editorial Comment for Sandhu et al.

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140372/1/end.2012.0411.pd

Classical Analogue of the Ionic Hubbard Model

In our earlier work [M. Hafez, {\em et al.}, Phys. Lett. A {\bf 373} (2009) 4479] we employed the flow equation method to obtain a classic effective model from a quantum mechanical parent Hamiltonian called, the ionic Hubbard model (IHM). The classical ionic Hubbard model (CIHM) obtained in this way contains solely Fermionic occupation numbers of two species corresponding to particles with \up and \down spin, respectively. In this paper, we employ the transfer matrix method to analytically solve the CIHM at finite temperature in one dimension. In the limit of zero temperature, we find two insulating phases at large and small Coulomb interaction strength, $U$, mediated with a gap-less metallic phase, resulting in two continuous metal-insulator transitions. Our results are further supported with Monte Carlo simulations.Comment: 12 figure

Heart ventricular histology and microvasculature together with aortic histology and elastic lamellar structure: A comparison of a novel dual-purpose to a broiler chicken line

The use of dual-purpose chickens is a strategy to avoid killing one-day-old male chicks of egg laying lines. Lohmann Dual (LD) is a novel dual-purpose chicken line created by the crossbreeding of layer and broiler lines. However, many of the cardiovascular diseases of broilers are likely to be associated with intensive genetic selection for growth and feed conversion efficiency. This study aimed to compare the macroscopic and microscopic structure of the heart and the aorta of the LD chicken line with that of the broiler chicken line, Ross 308 (Ross) under typical husbandry conditions for meat production. Eighty, one-day-old male chicks of each line were housed for 5 weeks (Ross) and 9 weeks (LD). Six birds of each line were sampled weekly. Heart mass, thickness of ventricular walls, cardiomyocyte size and blood capillary density as well as aortic diameter and thickness, number of elastic lamellae and elastic fiber percentage in the aortic wall were determined. The growth patterns of the heart were the same in the two lines. Although LD chickens had a lower absolute heart mass than that of Ross chickens, the relative heart mass in both lines was similar. The cardiomyocytes of LD chickens were larger than those of Ross’s of the same body weight (BW), nevertheless both lines had similar thicknesses of their ventricular walls. The blood capillary density was greater in the LD heart than in that of the Ross heart. The aorta of LD chickens had proportionally; a greater aortic lumen radius, larger numbers of elastic lamellae and more elastic fibers than in Ross chickens. Our results suggest that the heart and aorta of the LD chickens have not been disadvantaged by their intensive genetic selection; furthermore, LD chickens have a better myocardial capillary supply and better aortic mechanical properties than those of Ross chickens