A master's thesis in the Department of Mechanical Engineering / College of Engineering at the University of Basrah examined (the role of thermal interference between fluid steel in controlling mixed convection within a square gap with two ventilation holes) for graduate student Haider Faisal Jassim. Thermal convection using a flexible material, the gap contains a flexible fin of a small thickness and has self-impact, which was installed on the bottom wall of the gap and was heated by the two vertical walls so that the temperature of the left wall is higher than the temperature of the right wall. Water was also used with Brandel number 5.8 = pr As a working fluid, the equations governing the fluid and the solid were solved using the existing Galerkin finite element method.