44 research outputs found
Flow characteristics of an air jet impinging on a flat surface
Survey develops adequate heat transfer correlations for design use. Flow characteristics studies include - potential core length, velocity and pressure distribution through the jet, and spread of jet and velocity decay along jet axis
Experimental flow characteristics of a single turbulent jet impinging on a flat plate
Flow characteristics of single circular turbulent jet impinging on flat plate
Temperature fitting of partially resolved rotational spectra
In this paper we present a method to automatically fit the temperature of a rotational spectrum. It is shown that this fitting method yields similar results as the traditional Boltzmann plot, but is applicable in situations where lines of the spectrum overlap. The method is demonstrated on rotational spectra of nitric oxide from an atmospheric pressure microwave plasma jet operated with a flow of helium and air, obtained with two different methods: laser induced fluorescence and optical emission spectroscopy. Axial profiles of the rotational temperatures are presented for the ground NO X state and the excited NO A state
Recovering piecewise smooth functions from nonuniform Fourier measurements
In this paper, we consider the problem of reconstructing piecewise smooth
functions to high accuracy from nonuniform samples of their Fourier transform.
We use the framework of nonuniform generalized sampling (NUGS) to do this, and
to ensure high accuracy we employ reconstruction spaces consisting of splines
or (piecewise) polynomials. We analyze the relation between the dimension of
the reconstruction space and the bandwidth of the nonuniform samples, and show
that it is linear for splines and piecewise polynomials of fixed degree, and
quadratic for piecewise polynomials of varying degree
Adaptive fast multipole methods on the GPU
We present a highly general implementation of fast multipole methods on
graphics processing units (GPUs). Our two-dimensional double precision code
features an asymmetric type of adaptive space discretization leading to a
particularly elegant and flexible implementation. All steps of the multipole
algorithm are efficiently performed on the GPU, including the initial phase
which assembles the topological information of the input data. Through careful
timing experiments we investigate the effects of the various peculiarities of
the GPU architecture.Comment: Software available at http://user.it.uu.se/~stefane/freeware.htm
The stability for the Cauchy problem for elliptic equations
We discuss the ill-posed Cauchy problem for elliptic equations, which is
pervasive in inverse boundary value problems modeled by elliptic equations. We
provide essentially optimal stability results, in wide generality and under
substantially minimal assumptions. As a general scheme in our arguments, we
show that all such stability results can be derived by the use of a single
building brick, the three-spheres inequality.Comment: 57 pages, review articl
A Comparison of Splittings and Integral Equation Solvers for a Nonseparable Elliptic Equation
Spectroscopic investigations of microwave microplasmas in various gases at atmospheric pressure
In this paper results of the experimental investigations of a coaxial
microwave (2.45Â GHz) microplasma source (MMS) with graphite or tungsten
inner conductor operated in Ar, N2 and Ar/C2H2 mixture at
atmospheric pressure are presented. The microwave power absorbed by the
microplasmas and the intensity of UV-C emission from the microplasmas were
measured. Using optical emission spectroscopy, the electron number density
in Ar microplasma, and rotational and vibrational temperatures in N2
and Ar/C2H2 microplasmas were determined. All experiments were
performed with a gas flow rate from 0.3 to 8Â l/min and absorbed microwave
power from 5 to 300Â W. The simplicity of the MMS, stability of its operation
with atmospheric pressure gases, and parameters of the microplasmas allow
concluding that the MMS can be used in various applications
Spectroscopic Study of Plasma in Microwave Source Designed for Hydrogen Production via Hydrocarbons Decomposition
In this paper, results of spectroscopic study of microwave (2.45 GHz) plasma at atmospheric pressure and high flow rate are presented. The plasma was generated by waveguide-supplied nozzleless cylindrical type microwave plasma source. Working gas flow rate and microwave absorbed power varied from 50 up to 150 l/min and from 1 up to 5.5 kW, respectively. The emission spectra in the range of 300-600 nm were recorded. The rotational and vibrational temperatures of molecules, as well as the rotational temperature of OH radicals were determined by comparing the measured and simulated spectra. The plasma gas temperature inferred from rotational temperature of heavy species ranged from 4000 to 6000 K. It depended on location in plasma, microwave absorbed power and working gas flow rate. The presented microwave plasma source can be used in various gas processing applications
Experimental Investigation of Low Power Microwave Microplasma Source
The aim of this paper is to present a novel microwave microplasma source generated in different gases at atmospheric pressure. The design, rule of operation and experimental investigations of the new microwave microplasma source are described. The main advantage of the presented microwave microplasma source is its small size, simplicity, and low cost of construction and operation. The microplasma has a form of a small plasma jet of dimensions of a few mm, depending on the kind of gas, gas flow rate, and absorbed microwave power. Presented in this paper results of experimental investigations were obtained with an atmospheric pressure argon, krypton, nitrogen, and air microplasma, sustained by microwaves of standard frequency of 2.45 GHz. The absorbed microwave power was up to 70 W. The gas flow rate was from 2 to 25 l/min. The miniature size, simplicity of the source and stability of the microplasma allow to conclude that the presented new microwave microplasma source can find practical applications in various fields