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Various types of impinging jet flows are analytically modeled using inviscid free Gaussian jet solutions superimposed with experimentally fitted boundary layer models. Improved (more robust) and simplified solutions to existing models are defined. Velocity profiles, surface pressure distributions, and streamline plots are calculated for circular, plane, and annular impinging jets. The models show excellent agreement with existing experimental results in both laminar and turbulent conditions and for different Reynolds numbers. �DOI: 10.1115/1.2775502

Experiments were performed to characterize the development of the large-scale structures in the stagnation and wall-jet regions of a turbulent impinging jet with a nozzle-to-plate spacing of 2 diameters and a Reynolds number of 20000. In particular, the instantaneous pressure was measured at 137 points on the wall using 6 concentric rings of pressure taps located 0.25, 0.5, 1.0, 1.5, 2.0 and 2.5 pipe diameters from the jet centreline. The 6 rings respectively contained 8, 16, 16, 32, 32 and 32 equally spaced taps as well as a single pressure tap placed at the jet centerline. The fluctuating pressure was decomposed into azimuthal modes and it was found that a significant portion of the field was contained in azimuthal mode 0 associated with the axisymmetric ring structures and azimuthal mode 1, often associated with jet precessing. The instantaneous pressure was filtered so that only azimuthal modes 0, 1 and −1 remained, and the dynamics of the large-scale structures associated with these modes was examined. These structures were found to be convected radially outward, were highly intermittent, and found to not rotate in a preferred direction.

A cumulative frequency distribution fit method is presented for analyzing particle size distributions by minimizing the summation of the square of cumulative frequency errors. Compared to the frequency fit method, the cumulative frequency fit method yields a more accurate solution. Based upon this, a spreadsheet was developed for analyzing multi-modal particle size distribution. The motivation for the work presented in this article was the current interest in ultra-fine and nano-sized particle exhaust emissions from heavy-duty diesel engines. The new spreadsheet provides a quick and convenient way to conduct particle size distribution analysis.

An inviscid tornadolike vortex is analytically modeled using a free narrow jet solution combined with a modified Rankine vortex. An empirical and simplified solution to existing models is defined for flows similar to the ones simulated in Ward-type vortex chambers. Velocity profiles are calculated for a particular swirl ratio Sr=0.28. The model shows reasonable agreement with existing experimental measurements by Baker (1981, “Boundary Layers in Laminar Vortex Flows,” Ph.D. thesis, Purdue University, West Lafayette, IN) and the numerical simulation by Wilson and Rotunno (1986, “Numerical Simulation of a Laminar End-Wall Vortex and Boundary Layer,” Phys. Fluids, 29(12), pp. 3993–4005).