نشریه علوم کاربردی و محاسباتی در مکانیک
سال بیست و هشتم شماره 1 (پاییز و زمستان 1395)

An optimal design and fabrication of compressors requires flow investigation through the compressor components. Flow field inside the volute is fully three dimensional and turbulent. Better understanding of flow mechanism leads to improve the volute design procedure. In this research the experimental and numerical flow investigation through a radial flow compressor volute are performed to recognize flow field pattern and its effect on pressure loss. The whole compressor components are modeled and the flow field inside the volute is explored. Numerical studies are verified by measuring the pressures at different cross sections using pressure taps. Flow field investigation through volute cross sections at different operating range of the compressor is performed utilizing a five-hole probe. The experimental and numerical result differences for volute total pressure loss prediction are limited and decrease by mass flow rate increase. Flow field measuring results show the flow forced vortex structure at volute cross section. The effect of diffuser discharge on the fluid field in semi-external volute cross section is recognized as an extra pressure loss source in addition to creating the non-uniformity in velocity profile.

Present paper investigates the numerical solution of two-dimensional unsteady compressible Navier-Stokes equations by a new scheme based on the finite volume method. Kinetic Energy Preserving (KEP) scheme is introduced for solving the supersonic and Transonic external compressible flow field on very fine grids (with a number of cells of the order of the Reynolds number) without artificial dissipation terms even in place of shock waves. It should be noted that the solution of flow field with this scheme in this range of speed, is presented for the first time. By discretization of the governing equations based on KEP scheme and elimination of dissipative effects, the Direct Numerical Simulation (DNS) of the flow is possible. The results of this solution for supersonic flow over flat plate and Transonic flow over the airfoil at low Reynolds numbers show that the KEP method can be presented stable and non-oscillatory solution by no artificial dissipation even in areas with shock waves. Therefore, the KEP method can be used for DNS of turbulent flows (without a modeling the turbulence phenomena itself).

One of the new methods for electrical powering of the bridge health monitoring systems is applying energy harvesting systems using bridge vibration. In this method, the piezoelectric material is employed for converting mechanical energy into electrical energy. The advantage of this method is based on not implementing the battery charging system. In previous research, some studies have been done on the energy harvesting from vibration of bridges, however, research on statistical analysis of produced power with considering uncertain vehicle type and specifications has not been considered. Therefore in this paper, after modelling the bridge-vehicle-piezoelectric system with complete vehicles uncertainties, the statistical analysis of produced voltage are carried out by Monte-Carlo simulation.

At present study the flow and heat transfer of Non-Newtonian nanofluid, aqueous solution of carboxymethyl cellulose-Aluminum oxide with different volume fractions of nano particles in a two dimensional microtube is simulated for the first time. Slip velocity and temperature jump boundary conditions are also considered along the microtube walls. The achieved results accuracy is investigated by comparison with those of previous data. The results are presented as isothermal contours, Nusselt number and the profiles of temperature and velocity at different cross sections of the microtube. It is observed that Nusselt number increases with slip velocity coefficient and volume fraction of nano particles; while its rate is more sensitive at higher values of Reynolds number.

On the basis of the steady-state two-dimensional theory of thermoelasticity, stress field around various holes in infinite isotropic plate is discussed. The plate is subjected to uniform heat flux and thermal insulated condition along the hole boundary is assumed. by using the complex potential functions and by applying the conformal mapping and solving the integral equations, the effect of bluntness on stress distribution around the hole is studied. The used method is the expansion of the Goodier and Florence’s method. They used complex variable method for stress analysis of infinite isotropic plates with elliptical and circular holes. For simplicity of using the Cauchy integral formula, the infinite area external to the non-circular hole can be represented by the area outside the unit circle. The results obtained demonstrate the effect of bluntness on stress distribution around the holes.

In the current study, the immersed boundary – non-Newtonian lattice Boltzmann method is developed for simulation of forces act on a particle and also for computation of the particle velocity in vicinity of non-Newtonian fluids. In this research, the effect of extra force due to accelerated mass is also considered in non-Newtonian particle motion equations. Two applied problems of power-law non-Newtonian fluid flow over a stationary cylinder with square cross-section and a square falling particle in non-Newtonian fluids with different shear-thinning and shear-thickening behaviour are investigated. Results indicate that the force act on stationary cylinder and ultimate velocity of falling particle will experience considerable increase and decrease with growth of power-law non-Newtonian behaviour index, respectively.

Diffusion Flame in a Dust cloud combustion in a Counterflow configuration is investigated in this research. It is presumed that the fuel particles vaporize first to yield a gaseous fuel to oxidize with the gas phase. The reaction rate is assumed to be of the Arrhenius type. Conservation equations for the non-unity Lewis number are solved and the flame temperature with the variations of different Lewis numbers of fuel and oxidizer is proposed. Furthermore, the variations of flame position with the variation of Lewis number are evaluated. It has been found that the flame temperature decreases with increasing of fuel and oxidizer Lewis numbers, which for rise of fuel Lewis number from 0.1 to1.4, the flame temperature decreases from 1943 to 1473K.

In this paper, surface roughness of HT29 cancerous is determined using topography images obtained by Atimic Force Microscopy (AFM). The mean radiuses of cell and substrate surface asperities are determined, based on results of conducted roughness analysis and Rabinovich roughness theory. These values have been applied in the equations of rough particle nanomanipulation dynamic model and the amounts of critical force and time are simulated. Based on results, the rolling mode is the dominant dynamic mode at the onset of cells movement and the analysis based on rabinovich model predict lower amounts of critical force and time compared to Rumpf model based analysis.

In sheet metal forming processes, one-stage production of conical-cylindrical parts with high accuracy is very difficult due to wrinkling and rupturing. Hydrodynamic deep drawing assisted by radial pressure is one of the most applicable procedures in sheet hydroforming process on the point of producing conical-cylindrical parts. In this paper, forming pressure path is investigated as one of the most important parameters of this process. The optimized pressure path is obtained utilizing a new procedure by combination of the finite element method using ANSYS/LS-DYNA and an optimization method using simulated annealing.