I.Introduction

I-1 Presentation of the problem

I-2 The Theory

I-3 The Mesh
 

  II.Comparison between steady and unsteady options

II-1 Velicity magnitude

II-2 Temperature

II-3 Pressure

II-4 The Results
 

  III Determination of the critical Rayleigh number

III-1 From a high Rayleigh number with steady option

III-2 From low Rayleigh number with steady option

III-3 Comparison between the two methods with steady option

III-4. From high Rayleigh number with unsteady option

III-5. From low Rayleigh number with unsteady option

III-6. Comparison between the two methods with unsteady option

III-7. Comparison between the two options unsteady and steady
 

  IV.Conclusion