Secondary Instabilities in Compressible Boundary Layers
Abstract
This paper examines secondary instabilities in compressible boundary layers at Mach numbers M at = 0, 0.8, 1.6, and 4.5. We find that there is a broad-band of highly unstable 3-d secondary disturbances whose growth rates increase with increasing primary wave amplitude. At M < or = 1.6, fundamental resonance dominates at relatively high (2-d) primary disturbance amplitude, while subharmonic resonance is characterized by a low (2-d) primary amplitude. At M at = 4.5, the subharmonic instability which arises from the second mode disturbance is the strongest type of secondary instability. The influence of the inclination, theta, of the primary wave with respect to the mean flow direction on secondary instability is investigated at M at = 1.6 for small to moderate values of theta. It is found that the strongest fundamental instability occurs when the primary mode yields the most amplified subharmonic. The subharmonic instability at a high value of theta (namely, theta = 45 deg) is also discussed. Finally, a subset of the secondary instability results are compared against direct numerical simulations. (jhd)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1990
- Accession Number
- ADA227537
Entities
People
- G. Erlebacher
- Lian Ng