Hypersonic Transition Experiments in 3D Cone Flow with New Measurement Techniques
Abstract
This is the final report deals with laminar-turbulent transition measurements on an inclined cone at hypersonic Mach number. Within the flow field of an inclined cone three different boundary layer instabilities appear: first and second mode instability waves and crossflow vortices. Two different measurement techniques were applied: (i) IR-thermography was used for measuring stationary crossflow vortices. This instability was quantitatively measured. The position where these vortices evolve, their amplification and their wavenumber were determined. Further experiments were conducted aiming on affecting this wavenumber by placing small roughness elements on the cone surface that generate vortices. (ii) surface mounted pressure sensors were used for measuring travelling instabilities. The second mode waves are characterized regarding the position on the model where they appear, their frequency content and their spatial extensions and wave structure. Also low frequency waves (f approximately 20-40 kHz) were detected. These waves are so far interpreted as first mode waves, but since no stability computations are available this is uncertain. Also travelling crossflow vortices might cause this signal. The measurements of the wave structure and the spatial extent of second mode wave packets required an uncommon cone model. In total tree different model were used within this project. The last report covered the design of a new model with extended possibilities for mounting sensors. In the meantime new measurements have been conducted with this model and they are reported here. Measurements with suited positioning of pressure gauges and correlations of their signals allowed measurements of the spatial extent and propagation direction of second mode instability waves. New experimental results indicate the presence of low frequency waves; by analysis of the acquired data with higher order spectra new insights into the nonlinear stage of the transition process could be obtained
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 2012
- Accession Number
- ADA565852
Entities
People
- Dirk Heitmann
- Rolf Radespiel