---

Abstract: A comparative study of the application of symbol in Safavi and Iranian contemporary architecture The human kind was always accompanied by some tendency to use symbols, signs and codes. We’ve seen the most ancient of them in works of the primary human which are mostly in the form of graffiti due to technical reasons and in modern society there are few foundations which can be found with no trace of symbols and signs, since symbols and signs don’t require any other foundation than innovative mind of their creator. However, signs, as a kind of communication, need a dynamic society which is the other side of this communication, to communicate. The amount of applying these symbols and signs in different places and their vastness and variety are of the instances which always increase complication of discovering their true meaning. This mistaken recognition was always the challenge to this communication. In response to two questions of _ what are signs and symbols and where is the place for applying them in architecture? And what is the difference between using symbols and signs in Safavi and contemporary periods? _ this essay attempts to do a comparative study on the works of these two architectural periods of Iran by pointing out kinds of signs and presenting a classification of places in works of architecture where symbols and signs were applied. Therefore, a discussion about different kinds of signs, where they are applied in architecture and a case study were embarked on by using a combination of different studying methods of interpretive-historical and logical reasoning. In the end we study the differences and similarities and application process of symbols and signs in area of architecture. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * ** * * * * * * * * * * * * * * *

---

Aerodynamic study of flows at low Reynolds for special applications such as micro unmanned underwater vehicles, underwater robots and explorers are interested. In this paper, an improved progressive preconditioning method named power-law preconditioning method, for analyzing unsteady laminar flows around hydrofoils is presented. In this method, the 2D Navier-Stokes equations modifies by altering the time derivative terms of the governing equations. The preconditioning matrix is adapted from the velocity flow-field by a power-law relation. The governing equation is integrated with a numerical resolution derived from the cell-centered Jameson’s finite volume algorithm and a dual-time implicit procedure is applied for solution of unsteady flows. The stabilization is achieved via the second- and fourth-order artificial dissipation scheme. Explicit four-step Runge–Kutta time integration is applied to achieve the steady-state condition. The computations are presented for unsteady laminar flows around NACA0012 hydrofoil at various angles of attack and Reynolds number. Results presented in the paper focus on the velocity profiles, lift and drag coefficient and effect of the power-law preconditioning method on convergence speed. The results show satisfactory agreement with numerical works of others and also indicate that using the power-law preconditioner improves the convergence rate and decreases the computational cost, significantly.