---

In this study, the numerical investigation of transient natural convection with respect to the effects of two-way fluid-structure interaction, is presented in a square enclosure containing a flexible baffle. The enclosure is filled with air of Prandtl number 0.71. Temperature is constant in both hot and cold vertical walls, while baffle and horizontal walls are adiabatic. Arbitrary Lagrangian-Eulerian (ALE) formulation is used to describe the fluid motion in the given model. Non-Dimensional fluid domain equations with relevant boundary conditions are discretized by the finite volume method (FVM), and PISO algorithm is used to solve the pressure-velocity coupling. Non-Dimensional equations of the baffle motion are solved by the finite element method (FEM) and Newton-Raphson iteration technique. Rayleigh number changes over the range of 10^3 to 10^6. Among the assessed cases in this study, 25 and 35 percentages of them indicate respectively, increase and decrease in the rate of heat transfer in compare with the enclosure containing a rigid baffle. Maximum and minimum values of Num,ss variation are respectively, 4.5 and -15.4 percent. In compare with the rigid baffle, about 90 percent of assessed cases indicate an increase in the time to reach the steady state situations, that it is not considered favorable.

---

The purpose of this study is to investigate the effect of the simultaneous use of fuel injection injectors in an air cross flow. Nowadays, several methods are proposed for optimizing fuel injection in internal combustion engines. These optimizations are due to the high impact of this variable on engine performance and reduction of emissions. The method proposed in this study is to use two fuel injectors instead of a single injector in the air inlet manifold. The uses of two injectors in order to impingement two fuel sprays and increase the turbulent and collision of droplets, and so break them up faster. Also, the use of two injectors can provide more control over spatial and temporal distribution. Simulations are performed numerically using the generalized Kiva code. These simulations are similar to the fuel injection conditions in the manifold of the spark ignition internal combustion engine. The results indicate that the placement of two injectors in a longitudinal distance, the installation of two injectors at a 70 ° angle with the duct, placing two injectors in 180° or 90° relative angles and a 15° conical angle reduces the average diameter of the droplets. The results of this study can be used to design an internal combustion engine fuel injection system.