Abolfazl Shiri

Experimental Study of the Far Field of Incompressible Swirling Jets

The far field of an incompressible swirling jet has been studied using two-component laser Doppler anemometry. Three pairs of symmetric injectors were used to produce weak-to-moderate swirling jets. Velocity profiles of the mean and fluctuating streamwise and azimuthal velocity components were measured in jets with two swirl numbers (S = 0.15 and 0.25) at axial locations up to 50 jet exit diameters. The velocity and turbulence intensity profiles, centerline decay, and growth rates for the various swirling jets have been compared with those obtained in the same facility without swirl (S = 0). Like the previous observations for the near jet, there was no observable effect on the properly scaled far jet for the S = 0.15 case. The results were virtually identical to the non-swirling jet. For the S = 0.25 case, the only statistically significant effect was a shift in the virtual origin (from x/D* = 0.75 to -2.9). The recent predictions of equilibrium similarity theory were found to be in excellent agreement with the experimental results. In particular, the mean azimuthal component of velocity falls off as the inverse square of the downstream distance. By contrast, the mean stream-wise velocity and turbulence intensities fall off with the inverse of the downstream distance. As a consequence, the mean azimuthal equation uncouples from the rest, and so the asymptotic swirling jet behaves like the non-swirling jet.

An Experimental Study of the Far Field of Incompressible Swirling Jets

The far field of an incompressible swirling jet has been studied using two-component laser Doppler anemometry. Three pairs of symmetric injectors were used to produce weak-to-moderate swirling jets. Velocity profiles of the mean and fluctuating streamwise and azimuthal velocity components were measured in jets with two swirl numbers (S � 0:15 and 0.25) at axial locations up to 50 jet exit diameters. The velocity and turbulence intensity profiles, centerline decay, and growth rates for the various swirling jets have been compared with those obtained in the same facility without swirl (S � 0). Like the previous observations for the near jet, there was no observable effect on the properly scaled far jet for the S � 0:15 case. The results were virtually identical to the nonswirling jet. For the S � 0:25 case, the only statistically significant effect was a shift in the virtual origin (from x=D� � 0:75 to � 2:9). The recent predictions of equilibrium similarity theory were found to be in excellent agreement with the experimental results. In particular, the mean azimuthal component of velocity falls off as the inverse square of the downstream distance. By contrast, the mean streamwise velocity and turbulence intensities fall off with the inverse of the downstreamdistance.Asaconsequence,themeanazimuthalequationuncouplesfromtherest,andsotheasymptotic swirling jet behaves like the nonswirling jet.

TURBULENT NATURAL CONVECTION IN A DIFFERENTIALLY HEATED VERTICAL CHANNEL

The turbulence natural convection boundary layer inside a infinite vertical channel with differentially heated walls is analyzed based on a similarity solution methodology. The differences between mean temperature and velocity profiles in a boundary layer along a vertical flat plate and in a channel flow, make it necessary to introduce new sets of scaling parameters. In the limit as H* → ∞, two distinctive parts are considered: an outer region which dominates the core of the flow and inner constant heat flux region close to the walls. The proper inner scaling velocity is showed to be determined by the outer parameters due to momentum integral. The theory is contrasted with the one suggested by George & Capp (1), the deficiencies of which are identified.Copyright

Turbulent Flow Structure in the Similarity Region of Swirling Jet

Several previous investigations of the near field of swirling jets have shown that these jets grow at a faster rate than non-swirling jets and experience significant changes in the turbulence quantities (c.f.\ Gilchrist, Naughton). A recent study by Shiri et al., however, showed that the growth rate enhancement does not persist in the far-field of a swirling jet flow with moderate swirl numbers (0.15 and 0.25). The results were shown to be consistent with the equilibrium similarity theory of Ewing in which the mean swirl velocity was argued to decrease downstream as

Experimental Study of the Near Wall Region of a Natural Convection Driven Flow Next to a Vertical Cylinder

1/(x-x_o)^2

Turbulence Measurements in a Natural Convection Boundary Layer and a Swirling Jet

, while the mean stream-wise velocity decreased as

Evaluation of Closure Hypotheses Using Recent Experimental Data on the Similarity Region of Swirling Jet Flow

1/(x-x_o)

Turbulent Shear Flow Experiments: Design of Natural Convection Rig and LDA Measurement in Swirling Jets

. In fact the only statistically significant effect of the swirl on the mean velocity for even the highest swirl number was a shift in the virtual origin (to

An Experimental Study of the Far-Field of an Incompressible Swirling Jet

x/D_* = 0.75

Turbulence measurements in air near a heated vertical cylinder at high Raleigh number

from