A Commodity Supercomputer for Turbulence-Control Simulations
Abstract
Recent experiments have shown that properly designed high amplitude, low mass flux pulsed slot jets blowing normal to a jet's shear layer near the nozzle can significantly alter the jet's development (Parekh et al., AIAA Paper 96-0308). In contrasts to commonly used low amplitude forcing, this strong excitation appears to overwhelm the turbulence, having nearly the same effect at high and low Reynolds numbers. It can therefore be studied in detail by numerical simulation. In this study, direct numerical simulations of Mach 0.9, Reynolds number 3600 jets exhausting into quiescent fluid are conducted. Physically realistic slot jet actuators are included in the simulation by adding localized body- 'force' terms to the governing equations. Three cases are considered in detail: a baseline unforced case and two case and two cases that are forced with flapping modes at Strouhal numbers 0.2 and 0.4 (St = 0.4 was found to be the most amplified frequency in the unforced case). Forcing at either frequency causes that the jet to expand rapidly in the plane with the actuators and to contract in the plane perpendicular to the actuators, as observed experimentally. It is found that the jet responds closer to the nozzle when forced at St = 0.4, but forcing at = 0.2 is more effective at spreading the jet further downstream. Several different measures of mixing (scalar dissipation, volume integrals of jet fluid mixture fraction, and point measurements of mixture fraction) are considered, and it is shown that by most, but not all, measures forcing at St = 0.2 is the more effective of the two at mixing.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 10, 2001
- Accession Number
- ADA396427
Entities
People
- Jonathan B. Freund
Organizations
- University of California, Los Angeles