ORIGINAL_ARTICLE
Simulation of free surface wave pattern due to the moving bodies
Steady three-dimensional free surface waves generated by three dimensional moving bodies are presented. By applying Green’s theorem and the Green function method, an integral equation for the perturbation velocity potential is obtained based on the potential flow theory. The method uses constant-strength doublet and source density distribution over the foil body surface and Neumann-type condition. On the undisturbed free surface source density is applied to satisfy the free surface condition that is defined by the first and second order solutions. After solving the doublet on the body and source on the free surface, the computational results of pressure, lift, wave drag, wave pattern and wave elevation can be calculated at various Froude numbers. The results for the surface piercing (such as strut and Wigley hull) and submerged moving hydrofoils have been presented. The validity of the numerical results is examined by comparing it with the experimental results.
http://ijstm.shirazu.ac.ir/article_906_1b167018046dc0a27c3de495affbd785.pdf
2010-04-28T11:23:20
2018-08-22T11:23:20
117
134
10.22099/ijstm.2010.906
Free surface
pressure distribution
lift and drag
wave pattern
Wigley hull
ORIGINAL_ARTICLE
A complete treatment of thermo-mechanical ALE analysis; Part I: Formulation
Arbitrary Lagrangian Eulerian (ALE) finite element method is extensively used for numerical simulation of solid mechanics problem. The versatility of the mesh in ALE approach makes it particularly effective and efficient in solving large deformation problems. In this work, a complete treatment of fully coupled ALE formulation is presented incorporating inertial, rate and thermal effects. The formulation may be used in conjunction with thermo-elasto-viscoplactic material models. A consistent and efficient tangent operator is developed in closed form to handle stress integration. The applications of this formulation are given in the second part of this paper.
http://ijstm.shirazu.ac.ir/article_907_29460d72e828b527625e55250004123d.pdf
2010-04-28T11:23:20
2018-08-22T11:23:20
135
148
10.22099/ijstm.2010.907
Arbitrary Lagrangian Eulerian
Finite element method
large deformation
implicit dynamic analysis
thermo-mechanical
viscoplastic
ORIGINAL_ARTICLE
A complete treatment of thermo-mechanical ALE analysis; Part 2: Finite element equations and applications
In the first part of this paper series, a complete formulation for fully coupled ALE analysis of large deformation solid mechanic problems was developed. The formulation incorporated inertial, rate and thermal effects, and the treatment of rate and temperature dependent constitutive equations were presented. In this part, the ALE equations are discretized to form finite element equations. An algorithm for the treatment of mesh motion is described and example problems are presented to demonstrate the capability of the proposed formulation.
http://ijstm.shirazu.ac.ir/article_908_ea1a71982ba265fc6b4ac4b60dc6c305.pdf
2010-04-28T11:23:20
2018-08-22T11:23:20
149
165
10.22099/ijstm.2010.908
Arbitrary Lagrangian Eulerian
Finite element method
large deformation
implicit dynamic analysis
thermo-mechanical
viscoplastic
ORIGINAL_ARTICLE
Durability of a small agricultural engine on biogas/diesel dual fuel operation
Biogas from anaerobic digestion of organic waste is a potential alternative to the partial substitution of petroleum derived fuels because it is from renewable resources that are widely available. The effect of long term durability tests using biogas/diesel dual fuel operation on wear characteristics is evaluated and presented in this paper. Steady state tests were performed on a small, single cylinder, naturally aspirated, 4-stroke, direct injection diesel engine at a speed of 1500 rpm, coupled to a generator set to generate electricity for over 3500 hours. Lubricating oil samples were collected during the test run and were subjected to the analysis of various wear metal traces present and the changes in their properties. After completion of the endurance test, the engine was dismantled for physical inspection and wear assessment of vital parts. Formation of carbon deposits on in-cylinder surfaces was not found to be problematic. Injector tip coking did not occur. Surface wear and accumulations of metal debris in crankcase lubricating oil samples were analyzed and found to increase with time, but not at an unusual rate. Properties of used lubricating oils did not alter significantly from their original values. Wear was not significantly different in the test engine fueled with the biogas/diesel combination. An overall evaluation of the results indicated that the biogas/diesel duel fuel operation could be substituted for diesel fuel in electricity generation and worked satisfactorily under long term engine operation without any major troubles.
http://ijstm.shirazu.ac.ir/article_909_0c4071db88f1e20c741a642ffee710e3.pdf
2010-04-28T11:23:20
2018-08-22T11:23:20
167
177
10.22099/ijstm.2010.909
Biogas
compression ignition
dual fuel
endurance test
renewable energy
Wear
ORIGINAL_ARTICLE
A three-dimensional study of the motion of a drop in plane poiseuille flow at finite Reynolds number
Three-dimensional simulations are presented on the motion of a neutrally buoyant drop between two parallel plates at a finite-Reynolds-number in plane Poiseuille flow, under conditions of negligible gravitational force. The full Navier-Stokes equations are solved by a finite difference/front tracking method that allows a fully deformable interface between the drop and the suspending medium and the inclusion of the surface tension. In the limit of a small Reynolds number (<1), the direction of motion of the drop depends on the ratio of the viscosity of the drop fluid to the viscosity of the ambient fluid. At finite Reynolds numbers, the drop migrates to an equilibrium lateral position about halfway between the wall and the centerline (the Segre-Silberberg effect). Results are presented over a range of capillary number, Reynolds number, viscosity ratio and drop size. As the Reynolds number increases or capillary number or viscosity ratio decreases, the equilibrium position moves closer to the wall. The drop velocity is observed to increase with increasing capillary number and viscosity ratio, but decreases with increasing Reynolds number. The drops are more deformed with increasing the capillary number or viscosity ratio. The drop deformation increases slightly with increasing Reynolds number at constant capillary number. The equilibrium position of the three-dimensional drop is close to that predicted by two-dimensional simulations. But the translational velocities do not agree quantitatively with two-dimensional simulations.
http://ijstm.shirazu.ac.ir/article_910_ff371bd414e83da62ee2f926df86ba78.pdf
2010-04-28T11:23:20
2018-08-22T11:23:20
179
196
10.22099/ijstm.2010.910
Drop
Poiseuille flow
finite difference/front tracking method
capillary number
ORIGINAL_ARTICLE
Explicit minimum fuel intercept strategy for high-order dynamics
An optimal fuel guidance strategy with acceleration limit is derived for interception of maneuvering targets. The guidance/control system is assumed as a linear time-varying arbitrary-order and is identical in each channel. An approximate model for drag acceleration is also considered in the solution. The optimal fuel strategy has some detrimental effects in most practical situations, if it is used entirely to the end. This strategy can be used at the beginning of the guidance phase for large initial heading errors in order to quickly reduce it with minimum effort. An explicit guidance law is then developed for minimum and nonminimum phase autopilots in order to modify the undesirable effects of the optimal fuel guidance law.
http://ijstm.shirazu.ac.ir/article_911_398448083271cac325d657cddc257ce8.pdf
2010-04-28T11:23:20
2018-08-22T11:23:20
197
213
10.22099/ijstm.2010.911
Intercept guidance
minimum fuel
acceleration limit
ORIGINAL_ARTICLE
Rotor mass effect on nonlinear dynamic behavior of aerodynamic noncircular journal bearing systems
This paper presents the effect of rotor mass on nonlinear dynamic behavior of a rigid rotor supported by aerodynamic noncircular journal bearings. A finite element method has been employed to solve the Reynolds equation in static and dynamical states and the dynamical equations are solved using Runge-Kutta method. To analyze the behavior of the rotor center in horizontal and vertical directions under different operating conditions, dynamic trajectory, power spectra, Poincare maps and bifurcation diagrams are used. Results of this study reveal how the complex dynamic behavior of two types of noncircular bearing systems comprising periodic and -periodic responses of the rotor center varies with changes in rotor mass values.
http://ijstm.shirazu.ac.ir/article_912_b1d792f1830a5ffca6b1d6a0ea50c4a6.pdf
2010-04-28T11:23:20
2018-08-22T11:23:20
215
230
10.22099/ijstm.2010.912
Aerodynamic noncircular bearing
rotor mass
poincare map
Bifurcation
ORIGINAL_ARTICLE
Influence of particle size on corrosion resistance of electroless Ni-P-SiC composite coatings
High phosphorus electroless nickel bath has been used to prepare composite coatings containing SiC particles (40 nm, 3 mm and 7 mm). The coated samples were subjected to heat treatment at 400 °C for 1h. The effect of heat treatment on the microstructure of Ni-P-SiC composite coatings was investigated by X-ray diffraction. Potentiodynamic polarization measurements made on these deposits in 3% sodium chloride solution showed that corrosion resistance in nano-composite coatings was much higher than micro-composite coatings. The corrosion rate results for nano-composite coatings showed a 6 fold improvement as compared to the micro-composite coatings.
http://ijstm.shirazu.ac.ir/article_913_a0fa34929684f2ffde21c1be8d0e7c5f.pdf
2010-04-28T11:23:20
2018-08-22T11:23:20
213
234
10.22099/ijstm.2010.913
Particle size
Ni-P-SiC
electroless
corrosion resistance