Date of Award

Spring 5-19-2017

Author's Department

Mechanical Engineering & Materials Science

Degree Name

Master of Science (MS)

Degree Type



The critical Mach number is an important property of airfoils on aerodynamics. When the freestream Mach number exceeds the critical Mach number, shock will appear on the aircraft and cause a huge loss of energy. Lift decreases sharply and drag increases dramatically. We usually hope to increase the critical Mach number and delay the occurrence of shock so that the aircraft can fly with a higher speed and carry more weight.

In this thesis, the main task is to determine the critical Mach number of multi-element airfoil 30P30N in unbounded flow and in ground effect. Commercial software ICEM is employed to generate mesh. ANSYS Fluent is conducted to compute flow filed. The compressible The Reynolds-averaged Navier - Stokes equations (or RANS equations) with the Spalart-Allmaras Turbulence Model are solved in flow field. The results are discussed in three parts. Firstly the results lead to the determination of the critical Mach number of 30P30N airfoil in unbounded flow and compare it with the critical Mach number of single element airfoil RAE2822. In addition, the evolution of aerodynamics of 30P30N airfoil from unbounded flow to ground effect is displayed and the reasons are analyzed. Finally, the determination of the critical Mach number at different ride heights in ground effect is shown and a clear change in the critical Mach number can be seen.


English (en)


Ramesh Agarwal

Committee Members

Qiulin Qu;Swami Karunamoorthy


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