Abstract: A method of dynamic mesh based airfoil optimization is proposed according to the drawbacks of surrogate model based airfoil optimization. Programs are designed to achieve the dynamic mesh. Boundary condition is add by integrating commercial software Pointwise, meanwhile the CFD calculation is carried out by commercial software Fluent. The data exchange and communication between the software and programs referred above have been accomplished, and the whole optimization process is performed in iSIGHT platform. A simplified airfoil optimization study case is brought out to show that aerodynamic performances of airfoil have been significantly improved, even save massive repeat operations and increase the robustness and credibility of the optimization result. The case above proclaims that dynamic mesh based airfoil optimization is an effective and high efficient method.
Abstract: In contrast to existing methods which do not take into account multiconnectivity in a broad sense of this term, we develop mathematical models and highly effective combination (BIEM and FDM) numerical methods of calculation of stationary and quasistationary temperature field of a profile part of a blade with convective cooling (from the point of view of realization on PC). The theoretical substantiation of these methods is proved by appropriate theorems. For it, converging quadrature processes have been developed and the estimations of errors in the terms of A.Ziqmound continuity modules have been received. For visualization of profiles are used: the method of the least squares with automatic conjecture, device spline, smooth replenishment and neural nets. Boundary conditions of heat exchange are determined from the solution of the corresponding integral equations and empirical relationships. The reliability of designed methods is proved by calculation and experimental investigations heat and hydraulic characteristics of the gas turbine first stage nozzle blade.
Abstract: A two dimensional three segments coupled pendulum system that mathematically models human arm configuration was developed along with constructing and solving the equations of motions for this model using the energy (work) based approach of Lagrange. The equations of motion of the model were solved iteratively both as an initial value problem and as a two point boundary value problem. In the initial value problem solutions, both the initial system configuration (segment angles) and initial system velocity (segment angular velocities) were used as inputs, whereas, in the two point boundary value problem solutions initial and final configurations and time were used as inputs to solve for the trajectory of motion. The results suggest that the model solutions are sensitive to small changes in the dynamic forces applied to the system as well as to the initial and boundary conditions used. To overcome the system sensitivity a new approach is suggested.
Abstract: In a previously developed fast vortex method, the
diffusion of the vortex sheet induced at the solid wall by the no-slip
boundary conditions was modeled according to the approximation
solution of Koumoutsakos and converted into discrete blobs in the
vicinity of the wall. This scheme had been successfully applied to a
simulation of the flow induced with an impulsively initiated circular
cylinder. In this work, further modifications on this vortex method are
attempted, including replacing the approximation solution by the
boundary-element-method solution, incorporating a new algorithm for
handling the over-weak vortex blobs, and diffusing the vortex sheet
circulation in a new way suitable for high-curvature solid bodies. The
accuracy is thus largely improved. The predictions of lift and drag
coefficients for a uniform flow past a NASA airfoil agree well with the
existing literature.
Abstract: In contrast to existing methods which do not take into account multiconnectivity in a broad sense of this term, we develop mathematical models and highly effective combination (BIEM and FDM) numerical methods of calculation of stationary and quasi-stationary temperature field of a profile part of a blade with convective cooling (from the point of view of realization on PC). The theoretical substantiation of these methods is proved by appropriate theorems. For it, converging quadrature processes have been developed and the estimations of errors in the terms of A.Ziqmound continuity modules have been received. For visualization of profiles are used: the method of the least squares with automatic conjecture, device spline, smooth replenishment and neural nets. Boundary conditions of heat exchange are determined from the solution of the corresponding integral equations and empirical relationships. The reliability of designed methods is proved by calculation and experimental investigations heat and hydraulic characteristics of the gas turbine first stage nozzle blade.
Abstract: To study the impact of the inter-module ventilation (IMV) on the space station, the Computational Fluid Dynamic (CFD) model under the influence of IMV, the mathematical model, boundary conditions and calculation method are established and determined to analyze the influence of IMV on cabin air flow characteristics and velocity distribution firstly; and then an integrated overall thermal mathematical model of the space station is used to consider the impact of IMV on thermal management. The results show that: the IMV has a significant influence on the cabin air flow, the flowrate of IMV within a certain range can effectively improve the air velocity distribution in cabin, if too much may lead to its deterioration; IMV can affect the heat deployment of the different modules in space station, thus affecting its thermal management, the use of IMV can effectively maintain the temperature levels of the different modules and help the space station to dissipate the waste heat.
Abstract: In areas of low to moderate seismicity many building contents and equipment are not positively fixed to the floor or tied to adjacent walls. Under seismic induced horizontal vibration, such contents and equipment can suffer from damage by either overturning or impact associated with rocking. This paper focuses on the estimation of shock on typical contents and equipment due to rocking. A simplified analytical model is outlined that can be used to estimate the maximum acceleration on a rocking object given its basic geometric and mechanical properties. The developed model was validated against experimental results. The experimental results revealed that the maximum shock acceleration can be underestimated if the static stiffness of the materials at the interface between the rocking object and floor is used rather than the dynamic stiffness. Excellent agreement between the model and experimental results was found when the dynamic stiffness for the interface material was used, which was found to be generally much higher than corresponding static stiffness under different investigated boundary conditions of the cushion. The proposed model can be a beneficial tool in performing a rapid assessment of shock sensitive components considered for possible seismic rectification.
Abstract: This work presents the highly accurate numerical calculation
of the natural frequencies for functionally graded beams with
simply supported boundary conditions. The Timoshenko first order
shear deformation beam theory and the higher order shear deformation
beam theory of Reddy have been applied to the functionally
graded beams analysis. The material property gradient is assumed
to be in the thickness direction. The Hamilton-s principle is utilized
to obtain the dynamic equations of functionally graded beams. The
influences of the volume fraction index and thickness-to-length ratio
on the fundamental frequencies are discussed. Comparison of the
numerical results for the homogeneous beam with Euler-Bernoulli
beam theory results show that the derived model is satisfactory.
Abstract: Recently T. C. Au-Yeung, C.Au, and P. C. W. Fung [2] have given the solution of the KdV equation [1] to the boundary condition , where b is a constant. We have further extended the method of [2] to find the solution of the KdV equation with asymptotic degeneracy. Via simulations we find both bright and dark Solitons (i.e. Solitons with opposite phases).
Abstract: The theoretical investigation is carried out to describe
the effect of increase of pressure waves amplitude in clean and bubbly liquid. The goal of the work is to capture the regime of multiple magnification of acoustic and shock waves in the liquid,
which enables to get appropriate conditions to enlarge collapses of
micro-bubbles. The influence of boundary conditions and frequency
of the governing acoustic field is studied for the case of the
cylindrical acoustic resonator. It has been observed the formation of
standing waves with large amplitude at resonant frequencies. The
interaction of the compression wave with gas and vapor bubbles is
investigated for the convergent channel. It is shown theoretically that
the chemical reactions, which occur inside gas bubbles, provide additional impulse to the wave, that affect strongly on the collapses
of the vapor bubbles
Abstract: In this paper, mesh-free element free Galerkin (EFG) method is extended to solve two-dimensional potential flow problems. Two ideal fluid flow problems (i.e. flow over a rigid cylinder and flow over a sphere) have been formulated using variational approach. Penalty and Lagrange multiplier techniques have been utilized for the enforcement of essential boundary conditions. Four point Gauss quadrature have been used for the integration on two-dimensional domain (Ω) and nodal integration scheme has been used to enforce the essential boundary conditions on the edges (┌). The results obtained by EFG method are compared with those obtained by finite element method. The effects of scaling and penalty parameters on EFG results have also been discussed in detail.
Abstract: MOC (method of cell) is a new method of investigating
wave propagating in material with periodic microstructure, and can
reflect the effect of microstructure. Wave propagation in periodically
laminated medium consisting of linearly elastic layers can be treated
as a special application of this method. In this paper, it was used to
simulate the dynamic response of carbon-phenolic to impulsive
loading under certain boundary conditions. From the comparison
between the results obtained from this method and the exact results
based on propagator matrix theory, excellent agreement is achieved.
Conclusion can be made that the oscillation periodicity is decided by
the thickness of sub-cells. In the end, the NHDMOC method, which
permits studying stress wave propagation with one dimensional strain,
was applied to study the one-dimensional stress wave propagation. In
this paper, the ZWT nonlinear visco-elastic constitutive relationship
with 7 parameters, NHDMOC, and corresponding equations were
deduced. The equations were verified, comparing the elastic stress
wave propagation in SHPB with, respectively, the elastic and the
visco-elastic bar. Finally the dispersion and attenuation of stress wave
in SHPB with visco-elastic bar was studied.
Abstract: To achieve reliable solutions, today-s numerical and
experimental activities need developing more accurate methods and
utilizing expensive facilities, respectfully in microchannels. The analytical
study can be considered as an alternative approach to alleviate
the preceding difficulties. Among the analytical solutions, those with
high robustness and low complexities are certainly more attractive.
The perturbation theory has been used by many researchers to analyze
microflows. In present work, a compressible microflow with constant
heat flux boundary condition is analyzed. The flow is assumed to be
fully developed and steady. The Mach and Reynolds numbers are also
assumed to be very small. For this case, the creeping phenomenon
may have some effect on the velocity profile. To achieve robustness
solution it is assumed that the flow is quasi-isothermal. In this study,
the creeping term which appears in the slip boundary condition
is formulated by different mathematical formulas. The difference
between this work and the previous ones is that the creeping term
is taken into account and presented in non-dimensionalized form.
The results obtained from perturbation theory are presented based
on four non-dimensionalized parameters including the Reynolds,
Mach, Prandtl and Brinkman numbers. The axial velocity, normal
velocity and pressure profiles are obtained. Solutions for velocities
and pressure for two cases with different Br numbers are compared
with each other and the results show that the effect of creeping
phenomenon on the velocity profile becomes more important when
Br number is less than O(ε).
Abstract: New theory for functionally graded (FG) shell based on expansion of the equations of elasticity for functionally graded materials (GFMs) into Legendre polynomials series has been developed. Stress and strain tensors, vectors of displacements, traction and body forces have been expanded into Legendre polynomials series in a thickness coordinate. In the same way functions that describe functionally graded relations has been also expanded. Thereby all equations of elasticity including Hook-s law have been transformed to corresponding equations for Fourier coefficients. Then system of differential equations in term of displacements and boundary conditions for Fourier coefficients has been obtained. Cases of the first and second approximations have been considered in more details. For obtained boundary-value problems solution finite element (FE) has been used of Numerical calculations have been done with Comsol Multiphysics and Matlab.
Abstract: In this paper, the dynamic analysis of fuel storage
tanks has been studied and some equations are presented for the
created fluid waves due to storage tank motions. Also, the equations
for finite elements of fluid and structure interactions, and boundary
conditions dominant on structure and fluid, were researched. In this
paper, a numerical simulation is performed for the dynamic analysis
of a storage tank contained a fluid. This simulation has carried out by
ANSYS software, using FSI solver (Fluid and Structure Interaction
solver), and by considering the simulated fluid dynamic motions due
to earthquake loading, based on velocities and movements of
structure and fluid according to all boundary conditions dominant on
structure and fluid.
Abstract: The square-lattice Ising model is the simplest system
showing phase transitions (the transition between the paramagnetic
phase and the ferromagnetic phase and the transition between the
paramagnetic phase and the antiferromagnetic phase) and critical
phenomena at finite temperatures. The exact solution of the squarelattice
Ising model with free boundary conditions is not known for
systems of arbitrary size. For the first time, the exact solution of
the Ising model on the square lattice with free boundary
conditions is obtained after classifying all )
spin configurations with the microcanonical transfer matrix. Also, the
phase transitions and critical phenomena of the square-lattice Ising
model are discussed using the exact solution on the square
lattice with free boundary conditions.
Abstract: The present paper considers the steady free convection
boundary layer flow of a viscoelastic fluid on solid sphere with
Newtonian heating. The boundary layer equations are an order higher
than those for the Newtonian (viscous) fluid and the adherence
boundary conditions are insufficient to determine the solution of
these equations completely. Thus, the augmentation an extra
boundary condition is needed to perform the numerical
computational. The governing boundary layer equations are first
transformed into non-dimensional form by using special
dimensionless group and then solved by using an implicit finite
difference scheme. The results are displayed graphically to illustrate
the influence of viscoelastic K and Prandtl Number Pr parameters on
skin friction, heat transfer, velocity profiles and temperature profiles.
Present results are compared with the published papers and are found
to concur very well.
Abstract: The precision of heat flux simulation influences the
temperature field and test aberration for TB test and also reflects the
test level for spacecraft development. This paper describes TB tests for
a small satellite using solar simulator, electric heaters, calrod heaters
to evaluate the difference of the three methods. Under the same
boundary condition, calrod heaters cases were about 6oC higher than
solar simulator cases and electric heaters cases for
non-external-heat-flux cases (extreme low temperature cases). While
calrod heaters cases and electric heaters cases were 5~7oC and 2~3oC
lower than solar simulator cases respectively for high temperature
cases. The results show that the solar simulator is better than calrod
heaters for its better collimation, non-homogeneity and stability.
Abstract: This paper presents the buckling analysis of short and
long functionally graded cylindrical shells under thermal and
mechanical loads. The shell properties are assumed to vary
continuously from the inner surface to the outer surface of the shell.
The equilibrium and stability equations are derived using the total
potential energy equations, Euler equations and first order shear
deformation theory assumptions. The resulting equations are solved
for simply supported boundary conditions. The critical temperature
and pressure loads are calculated for both short and long cylindrical
shells. Comparison studies show the effects of functionally graded
index, loading type and shell geometry on critical buckling loads of
short and long functionally graded cylindrical shells.
Abstract: This paper deals with a numerical analysis of the
transient response of composite beams with strain rate dependent
mechanical properties by use of a finite difference method. The
equations of motion based on Timoshenko beam theory are derived.
The geometric nonlinearity effects are taken into account with von
Kármán large deflection theory. The finite difference method in
conjunction with Newmark average acceleration method is applied to
solve the differential equations. A modified progressive damage
model which accounts for strain rate effects is developed based on
the material property degradation rules and modified Hashin-type
failure criteria and added to the finite difference model. The
components of the model are implemented into a computer code in
Mathematica 6. Glass/epoxy laminated composite beams with
constant and strain rate dependent mechanical properties under
dynamic load are analyzed. Effects of strain rate on dynamic
response of the beam for various stacking sequences, load and
boundary conditions are investigated.