Mach Number, Reynolds Number, Jet Spacing Variations: Full Array of Impinging Jets

Abstract

Presented are data that illustrate the effects of Mach number, Reynolds number, and hole spacing on surface Nusselt numbers produced by an array of jets impinging on a flat plate. Considered are Reynolds numbers ranging from 17,300 to 60,000 and Mach numbers from 0.1 to 0.45. Impingement hole spacings are 5D, 8D, and 12D in the streamwise and spanwise directions. Local spatially resolved and spatially averaged Nusselt numbers, measured using infrared thermography and energy balance techniques, show strong dependence on the impingement jet Reynolds number for each situation as the jet Mach number is maintained constant. Nusselt numbers show negligible variations between Ma = 0.1 and 0.2; however, data taken at Mach numbers greater than 0.2 (as the Reynolds number is held constant) show that Mach number has a significant impact on local and spatially averaged Nusselt numbers. This Mach number dependence changes with hole spacing, with greater Nusselt number increases with the less dense impingement arrays. These variations are described using new correlations, which account for the effects of Mach number for all three impingement hole spacings.