scholarly journals Natural Smoldering of Cigarettes

2003 ◽  
Author(s):  
Fernando de Souza Costa
Keyword(s):  
Boundary Layer ◽  
Analytical Model ◽  
Heat Losses ◽  
Algebraic Equations ◽  
Simple Analytical Model ◽  
Influence Coefficients ◽  
Linear Algebraic Equations ◽  
Char Oxidation ◽  
Diffusive Processes ◽  
Good Agreement

The smoldering of cigarettes without drawing is described by a simple analytical model. A burning cigarette is assumed to be divided in 4 zones: unburned tobacco, dry tobacco, char and ash, separated by infinitesimally thin fronts of drying, pyrolysis and char oxidation. Circumferential heat losses and the convective-diffusive processes in the boundary layer are considered. A set of non-linear algebraic equations is solved to determine smoldering rates, drying lengths and pyrolysis lengths and to obtain the profiles of temperature. The influence coefficients of several parameters on smolder characteristics are calculated. Theoretical burn rates have shown a good agreement to experiments.

The laminar boundary-layer equation: a method of solution by means of an automatic computer

1955 ◽  
Vol 51 (2) ◽  
pp. 320-332 ◽  
Author(s):  
D. C. F. Leigh
Keyword(s):  
Boundary Layer ◽  
Asymptotic Solution ◽  
Laminar Boundary Layer ◽  
Iterative Process ◽  
Boundary Layer Equation ◽  
Algebraic Equations ◽  
Automatic Computer ◽  
Linear Algebraic Equations ◽  
Method Of Solution ◽  
Incompressible Boundary

ABSTRACTA method, very suitable for use with an automatic computer, of solving the Hartree-Womersley approximation to the incompressible boundary-layer equation is developed. It is based on an iterative process and the Choleski method of solving a simultaneous set of linear algebraic equations. The programming of this method for an automatic computer is discussed. Tables of a solution of the boundary-layer equation in a region upstream of the separation point are given. In the upstream neighbourhood of separation this solution is compared with Goldstein's asymptotic solution and the agreement is good.

A simple projection moiré system to measure displacements of aircraft structures

2007 ◽  
Vol 42 (6) ◽  
pp. 477-495 ◽  
Author(s):  
U Galietti ◽  
K Genovese ◽  
L Lamberti ◽  
D Posa
Keyword(s):  
Analytical Model ◽  
Large Scale ◽  
Industrial Applications ◽  
Processing Method ◽  
Simple Analytical Model ◽  
Aerodynamic Loads ◽  
Out Of Plane ◽  
Plane Displacement ◽  
Good Agreement ◽  
Projection Moire

This work presents a simple projection moiré system (PMS) to measure displacements of large-scale aeronautical components. The system includes standard optics, uses a standard fringe-processing method, and relies on a simple analytical model to recover topographic information. An extensive calibration campaign, based on design of experiments, is conducted in order to find the best analytical model for retrieving the out-of-plane displacement field from the moiré pattern and to find the optimal combination of parameters involved in the measurement system. In order to check the suitability of the present PMS device for practical industrial applications, distortions induced by aerodynamic loads on a landing-light glazing of an Airbus A340 are measured. Experimental results are in good agreement with other measurements carried out independently.

Parametric Study of the Discharge Coefficient on Critical Sonic Nozzles ISO-9300 With Turbulent Boundary Layer

2002 ◽  
Author(s):  
F. Sa´nchez Silva ◽  
J. A. Cruz Maya ◽  
A. Go´mez Mercado ◽  
G. Tolentino Eslava
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Analytical Model ◽  
Parametric Study ◽  
Discharge Coefficient ◽  
Numerical Data ◽  
Starting Point ◽  
Two Dimensional Flow ◽  
Viscous Stresses ◽  
Good Agreement

A parametric study on determining discharge coefficient in ISO 9300 [1] toroidal sonic nozzles have been developed. The focus of this paper is to obtain the an analytical model for the calculus of this discharge coefficient on turbulent boundary layer conditions for gases at Pr = 0.7. The problem is divided in two sections: one in which the viscous stresses are taking in to account at boundary layer zone, based on turbulent boundary layer theory and taking as starting point the work carried out by Stratford [2]. Then, curvature of flow field is studied at the nucleus of the nozzle, obtaining discharge coefficient values using numerical simulation for a two-dimensional flow. The results have a good agreement with correlations of ISO-9300 [1], experimental and numerical data of Wu-Yan [3] and the analytical model from Stratford [2].

A Simple Analytical Model to Simulate Oblique Ballistic Impact onto Fabric

2011 ◽  
Vol 110-116 ◽  
pp. 3453-3458
Author(s):  
Mohamad Ali Akbari ◽  
Golam Hosein Liaghat ◽  
Hadi Sabouri
Keyword(s):  
Experimental Data ◽  
Analytical Model ◽  
Ballistic Impact ◽  
Experimental Results ◽  
Simple Analytical Model ◽  
Good Agreement

A simple analytical model for oblique ballistic impact of projectiles into fabrics are presented. This model is extension of Chocron-Benloulo penetration model. Results are compared with experimental data. There is good agreement between analytical and experimental results.

A SIMPLE ANALYTICAL MODEL FOR EVALUATION OF PENETRATION DEPTH AND RESISTANT STRENGTH OF CONCRETE TARGETS

2013 ◽  
Vol 13 (03) ◽  
pp. 1250061 ◽  
Author(s):  
A. RAMACHANDRA MURTHY ◽  
G. S. PALANI ◽  
NAGESH R. IYER
Keyword(s):  
Penetration Depth ◽  
Analytical Model ◽  
Cavity Expansion ◽  
Strength Parameter ◽  
Spherically Symmetric ◽  
Simple Analytical Model ◽  
Depth Of Penetration ◽  
Projectile Velocity ◽  
Symmetric Cavity ◽  
Good Agreement

This paper presents a simple analytical model for evaluation of penetration depth and resistant strength of concrete target. The model is based on the assumption that the deformation and failure of the projectile are negligible. Normal impact is assumed in the model. It is also assumed that the penetration is steady state within the time step, the momentum balance equation can be integrated, resulting in an explicit expression for the pressure at the target interface. The expressions for spherically symmetric cavity expansion for a material with locked hydrostatic stress and constant shear strength have been developed. The constants for failure criterion are derived based on Mohr–Coulomb and Tresca-limit yield line theories. Final depth of penetration has been derived using the results of spherically symmetric cavity expansion analysis, relating the radial stress at the cavity surface to cavity expansion velocity and Newton’s second law of motion. Target resistant strength parameter is expressed as a function of penetration depth, projectile velocity, nose performance coefficient, target density, mass of projectile, and radius of the projectile. The expressions for velocity, acceleration and displacement at any instant of time have been deduced based on total depth of penetration and target resistant strength. To validate the methodologies, numerical studies have been conducted and observed that the penetration depth and target resistant strength obtained in the present study are in good agreement with the corresponding experimental values reported in the literature. It is also observed that the time history of penetration depth and projectile velocity are in good agreement with the corresponding literature values.

Bending of normally loaded simply supported rectangular plates in the large-deflection range

1969 ◽  
Vol 4 (3) ◽  
pp. 190-198 ◽  
Author(s):  
A Scholes ◽  
E L Bernstein
Keyword(s):  
Linear Equations ◽  
Rectangular Plates ◽  
Algebraic Equations ◽  
Simply Supported ◽  
Aspect Ratios ◽  
Linear Algebraic Equations ◽  
Non Linear ◽  
Out Of Plane ◽  
Linear Differential ◽  
Good Agreement

Means of solving the non-linear differential equations of plate bending are revieweed and a method based on minimizing the corresponding energy integral is selected as offering most advantages. The energy intergral can be approximated either by using finite-difference approximatons or by assuming a form of displacement variation. Two sets of non-linear algebraic equations (in the in-plane and out-of-plane deflections) are thus formed and, by substitution alternately in each set, the resulting linear equations are solved. Results for simply supported rectangular plates have been worked out in some detail; these are compared with tests made on plates of various aspect ratios. Good agreement on maximum values of stress and deflection was obtained.

A Fast And Efficient Simulation Tool For The Voltage Handling Capability Of High Voltage Devices

1997 ◽  
Vol 483 ◽  
Author(s):  
E. Stefanov ◽  
G. Charitat ◽  
N. Nolhier ◽  
Ph. Spiesser
Keyword(s):  
High Voltage ◽  
Algebraic Equations ◽  
Power Semiconductor ◽  
Original Algorithm ◽  
Linear Algebraic Equations ◽  
Fast Solution ◽  
Automatic Search ◽  
High Level ◽  
Good Agreement ◽  
Biconjugate Gradient

AbstractThe user-oriented simulator POWER2D for studying the voltage handling capability of power semiconductor devices is presented. The simulation is based on the Poisson's equation solution for an arbitrary shaped 1D, 2D, and cylindrical 3D high voltage semiconductor structures. Very fast solution of the potential is obtained for a high level of applied bias, based on incomplete LU decomposition preconditioned biconjugate gradient method, and combined with a multi-damping scheme for the Newton linearization of the non-linear algebraic equations. An original algorithm is developped ensuring a very fast and automatic search of the breakdown via the ionization integrals calculus. The predicting capability of the program is illustrated for different termination techniques showing good agreement with the experiment.

scholarly journals Nonlinear bending models for beams and plates

2014 ◽  
Vol 470 (2170) ◽  
pp. 20140064 ◽  
Author(s):  
Y. A. Antipov
Keyword(s):  
Jacobi Polynomials ◽  
Integral Condition ◽  
Horizontal Displacement ◽  
Form Solution ◽  
Algebraic Equations ◽  
Nonlinear Bending ◽  
Original Length ◽  
Linear Algebraic Equations ◽  
Expansion Coefficients ◽  
Good Agreement

A new nonlinear model for large deflections of a beam is proposed. It comprises the Euler–Bernoulli boundary value problem for the deflection and a nonlinear integral condition. When bending does not alter the beam length, this condition guarantees that the deflected beam has the original length and fixes the horizontal displacement of the free end. The numerical results are in good agreement with the ones provided by the elastica model. Dynamic and two-dimensional generalizations of this nonlinear one-dimensional static model are also discussed. The model problem for an inextensible rectangular Kirchhoff plate, when one side is clamped, the opposite one is subjected to a shear force, and the others are free of moments and forces, is reduced to a singular integral equation with two fixed singularities. The singularities of the unknown function are examined, and a series-form solution is derived by the collocation method in terms of the associated Jacobi polynomials. The procedure requires solving an infinite system of linear algebraic equations for the expansion coefficients subject to the inextensibility condition.

A Model for the Pull-In Parameters of Magnetostatic Actuators with Fringing Effect

2013 ◽  
Vol 432 ◽  
pp. 229-234
Author(s):  
Yu Ming Fang ◽  
Jun Jian Qie
Keyword(s):  
Analytical Model ◽  
Simple Analytical Model ◽  
The Past ◽  
Wide Range ◽  
Mems Actuators ◽  
Fringing Field ◽  
Simulation Results ◽  
Fringing Field Effect ◽  
Gap Spacing ◽  
Good Agreement

Predicting Pull-In parameters is crucial in the design of MEMS actuators. In the past, the Pull-In parameters of magnetostatic actuators with the fringing field effect are often estimated using finite element method (FEM). However, FEM is cumbersome, time consuming and non-transparent, which is not convenient for the design optimization. Usually, there are a simple analytical model without leakage reluctance and a detailed analytical model with leakage reluctance respectively. This paper used the two models to derive the Pull-In model of magnetostatic actuators respectively. The accuracy of the two Pull-In models is examined by comparing their results with the FEM results. Simulation results show that the Pull-In model without leakage reluctance is unsuitable to predict Pull-In parameters. The Pull-In model with leakage reluctance has shown a good agreement with the FEM results for a wide range of gap spacing.

Simple Analytical Model for Entire Turbulent Boundary Layer over Flat Plane

2005 ◽  
Vol 5 (4) ◽  
pp. 373-386 ◽  
Author(s):  
Victor S. L’vov ◽  
Anna Pomyalov ◽  
Vasil Tiberkevich
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Analytical Model ◽  
Simple Analytical Model
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