Mixing and Frequency Analysis of a Forced Jet in Cross Flow

Abstract

The frequency interactions and mixing of a subsonic perpendicular jet in cross flow problem is solved numerically. Thirteen different cases are solved ranging from steady state cases to fully modulated forced jet in forced cross flow with high frequency sinusoidal waveforms. The frequency analysis shows that in the ca se of a forced jet in cross flow, or jet into a forced cross flow, the obtained frequencies are the imposed frequency and its harmonics. In the case of a forced jet in forced cross flow case, the frequencies driving the problem include the input frequenci es as well as the difference between them and their harmonics. For some variables in jet penetration region, the dominant frequency value is the difference between the input frequencies. In the case of a fully modulated jet sine waveform, the results sho w an increase in jet penetration of 41 % more compared with the steady state case when the jet -to -crossflow momentum flux ratio (J) equals 9, and about a 30% increase in mixedness in the far field is achieved. A correlation is given and tested to estimate the jet trajectories of the forced jet in cross flow with different amplitudes from the steady state trajectory. Nomenclature