Abstract
The influence of gas molecular weight and specific heat ratio on entrainment and mixing is investigated for sonic jets in a supersonic crossflow. Five pure gases (argon, ethylene, carbon dioxide, helium, and nitrogen) spanning molecular weights of 4–44g/mol and specific heat ratios of 1.24–1.66 are injected into a Mach 1.71 crossflow at momentum flux ratios from 1 to 6. Planar Mie scattering and particle image velocimetry provides measurements of velocity fields on the flow's plane of symmetry. The velocity fields provide information about mean and fluctuating velocities, as well as the jet bow shock geometry. Convective Mach number profiles are computed directly from the velocity data. Results show that compressibility effects grow faster for lower molecular weight gases, with peak convective Mach numbers reaching approximately unity for helium compared to higher values for heavier gases. Injectants with higher molecular weight and lower specific heat ratios demonstrate faster entrainment and mixing, as evidenced by decreased velocity fluctuations in the near field of the jet. The convective Mach number estimates explain these trends through compressible suppression of hydrodynamic instabilities. The velocity data and spatially resolved convective Mach number profiles for a large range of injectant properties provide unprecedented quantitative guidance for the design of systems dependent on supersonic injection and mixing.
| Original language | English |
|---|---|
| Article number | 125111 |
| Journal | Physics of Fluids |
| Volume | 37 |
| Issue number | 12 |
| DOIs | |
| State | Published - Dec 1 2025 |
Bibliographical note
Publisher Copyright:© 2025 Author(s).
Funding
The authors acknowledge partial support of this study by AFOSR (Grant No. FA9550-15-1-0512) and the DOE (Grant No. DE-FOA-0001386). The authors thank Professor Craig Dutton and Professor Juan Santiago for making the data in available, Professor Toshinori Kouchi for allowing us to use the data in , and Professor Sanjiva Lele for allowing us to reproduce and . The first author also acknowledges the helpful discussions with Professor Adam Steinberg and Dr. Tim Ombrello, as well as the work done in the lab by Carson Dobbs.
| Funders | Funder number |
|---|---|
| Air Force Office of Scientific Research, United States Air Force | FA9550-15-1-0512 |
| U.S. Department of Energy EPSCoR | DE-FOA-0001386 |
ASJC Scopus subject areas
- Computational Mechanics
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering
- Fluid Flow and Transfer Processes