Large-eddy simulation of turbulent flow over a plane free cavity and over a plane symmetric cavity was performed. The Smagorinsky sub-grid scale turbulence model was used. The compressible formulation and the MacComarck finite volume method were employed. The dynamic and thermal behavior of a thermal capacitor were analyzed. This behavior presents strong dependence on the geometry and the temperature fluctuation frequency which is imposed in the entrance of capacitor and a little dependence on the Reynolds Number.