Showing 6 results for H. Ahmadi
H. Ahmadi, Rahim Zolanwar,
Volume 8, Issue 1 (4-1990)
Abstract
K. Sadrnezhaad and H. Ahmadian,
Volume 17, Issue 2 (4-1998)
Abstract
In this research a Cu-Zn-Al alloy is produced by melting the raw materials in an electric resistance furnace and then pouring it into a steel mould. The optimum way to achieve the final analysis in the hypo-eutectoid range is determined and the influence of the alloying element, Ti on the grain size and the shape memory properties of the samples are investigated. Solution treatment (done at 850˚C) followed by quenching in ice-water mixture results in the formation of the martensitic structure and the shape memory effect. Aging at temperatures bellow 200˚C results in the reduction of transformation temperatures, while aging at temperatures between 200˚C and 350˚C results in the enhancement of these temperatures and at temperatures above 350˚C results in the destruction of the shape memory properties. Effect of super-elasticity at 40˚C (between Md and Ms) is observed and tensile tests are run at 25˚C and -55˚C to verify the influence of the prevailing phase.
E. Shirani, and H. Ahmadikia,
Volume 19, Issue 2 (1-2001)
Abstract
2-D and axisymmetric Navier-Stokes equations are solved using Reiman-Roe solver with different limiters for second-order accurate schemes. The results were obtained for supersonic viscous flows over semi-infinite axisymmetric and 2-D bodies. The free stream Mach numbers were 7.78 and 16.34. The stability of Roe method with different limiters and entropy conditions were considered. The results show that the limiters greatly affect the stability and accuracy of the numerical solution while the entropy conditions do not.
A. R. Pishehvar and H. Ahmadi Kia,
Volume 20, Issue 2 (4-2001)
Abstract
In this study, the missile staging process by implementing a side-injected jet is simulated numerically. The problem is considered to be axisymmetric and the thin shear layer approximation of Navier-Stokes equations along with an algebraic turbulence model is used in a quasi-static form for the calculations. The free stream corresponds to a very high altitude flight condition with a Mach number of 10 and an injected jet pressure ratio of about 63000. An explicit Godunov-type scheme is used in the calculations, which is second-order in time and space. Computations are performed on the attached and separated geometry for a range of distances between the body and the warhead. The intense interactions between the jet flow and the main free-stream and its overall influences on the warhead aerodynamic loading are finally demonstrated.
Keywords: Missile Staging, Jet Interaction flow, TVD Scheme, Riemann problem
H. Ahmadikia, and G. A. Iravani,
Volume 26, Issue 1 (7-2007)
Abstract
Design of a natural dry cooling tower has been accomplished in two sections: the design of heat exchangers and the numerical solution of flow through the tower. Heat exchanger (Heller type) has been simulated thermodynamically and then coupled with a computer program, which calculated the turbulent natural convection flow through the tower. The computer program developed for this purpose can be used to obtain thermodynamic propertied of the cooling tower such as mass flow rate of air, temperature of outlet water, distribution of temperature, distribution of velocity, and distribution of pressure through the tower. Numerical results have been compared with experimental data of Shahid Montazery Thermal Power Plant under different environmental conditions. Comparison between numerical results and experimental data showed good agreement.
A. Eslami, H. Modaraei, and H. Ahmadi,
Volume 26, Issue 2 (1-2008)
Abstract
