A study of free jet impingement. Part 2. Free jet turbulent structure and impingement heat transfer

Abstract

An experimental study of jet impingement is completed with the presentation of the measured turbulent characteristics of the circular subsonic jet and the heat transfer rates measured when this jet impinges normal to a flat plate. The data suggest that for impingement very close to the stagnation point, the heat transfer can be computed by applying a turbulent correction factor to the laminar value calculated for a flow having the same pressure distribution as that present in the impingement region. The correction factor is found to be a function of the axial distance and not of Reynolds number. Farther away, the measurements agree well with the heat transfer estimated using the method of Rosenbaum & Donaldson (1967). At large distances from the stagnation point, the heat transfer falls off in inverse proportion with the distance.The documentation of the turbulent jet flow field includes measurements of the radial and axial velocity fluctuations and their spectra, as well as the radial distribution of turbulent shear$\overline{w^{\prime}u^{\prime}}$. In addition, measurements of the turbulence near the stagnation point and the total pressure fluctuation at the stagnation point are presented.

The Effect of Impingement on Transitional Behavior in Underexpanded Jets

“…Impinging jet flows were studied extensively by Donaldson et al, 4,5 including pitot pressure surveys and surface pressure measurements. But the motivation behind these and many subsequent studies is almost universally cited as the study of rocket plumes impinging on the ground, or exhaust from the engine of a V/STOL (vertical/short takeoff and landing) vehicle.…”

Fluorescence Imaging Study of Impinging Underexpanded Jets

“…The impinging jet configurations in the present work, with the closest impingement distance being about 10.5 nozzle diameters and the furthest being 39.5 nozzle diameters, are all relatively far-field compared to the studies listed in Table 1 (with the exception of Stitt. 11 Note also that, even though the investigations of Donaldson and Snedeker 6,7 had some limited data at about 40 nozzle diameters, the vast majority of their data were within about 15 nozzle diameters). In rocket plume/ground interaction applications, ground erosion was a primary concern, and the near field was thus of greatest significance.…”

Fluorescence Imaging of Underexpanded Jets and Comparison with CFD

“…Such jets have been investigated extensively in the study of propulsive jets, rocket exhaust plumes, and vehicle control jets. [1][2][3][4][5][6][7] The present study was motivated by the NASA Shuttle Return to Flight (RTF) investigation into the effects of flow through vehicle wing breaches. Computational fluid dynamics (CFD) represents a vital tool for evaluating flight damage scenarios since no set of ground-based experiments could anticipate every potential vehicle damage scenario nor entirely replicate the high-energy flight environment.…”