Signal Transit Velocities in a Turbulent Plane Jet

1976 ◽  
Vol 98 (3) ◽  
pp. 443-446
Author(s):  
A. K. Stiffler
Keyword(s):  
Nozzle Exit ◽  
Flow Direction ◽  
Turbulent Jet ◽  
Measured Signal ◽  
Centerline Velocity ◽  
Pressure Gradients ◽  
Periodic Pressure ◽  
Turbulent Plane ◽  
Plane Jet ◽  
Signal Time

A turbulent jet is perturbed transverse to the flow direction by periodic pressure gradients near the nozzle exit. Transit velocities are defined in terms of the measured signal time delay for stations 8, 12, 16 nozzle widths downstream of the nozzle exit. Excitation frequencies to 800 cps are considered. Transit velocities are found to be much less than the jet centerline velocity. The results are related to the convection velocity of turbulence.

Sinusoidal Excitation of a Free Turbulent Jet With Constant Amplitude Transverse Pressure Gradients Near the Nozzle Exit: Part I: Measurement of Mean Shear Velocities

1973 ◽  
Vol 95 (2) ◽  
pp. 167-173
Author(s):  
A. K. Stiffler ◽  
J. L. Shearer
Keyword(s):  
Nozzle Exit ◽  
Flow Direction ◽  
Excitation Frequency ◽  
Velocity Profiles ◽  
Turbulent Jet ◽  
Pressure Gradients ◽  
Mean Velocity ◽  
Effective Velocity ◽  
Gaussian Distribution Function ◽  
The Mean

A free turbulent jet is perturbed transverse to the flow direction by a sinusoidal pressure gradient near the nozzle exit. Velocities in the jet are determined by hot wire anemometer measurements. Moving effective mean velocity profiles are defined and reconstructed from the point-by-point stationary measurements of the mean velocity and of the harmonic content of the time varying signal. The effective velocity profiles are described by the Gaussian distribution function where the spread parameter decays as the cube of the product of the excitation frequency and the downstream location from the nozzle. These profile measurements and analysis of their characteristics lead to a better understanding of the factors determining the gain of a fluidic amplifier under conditions of high frequency operation.

Sinusoidal Excitation of a Free Turbulent Jet With Constant Amplitude Transverse Pressure Gradients Near the Nozzle Exit: Part II: An A-C Fluidic Model for the Jet Gain

1973 ◽  
Vol 95 (2) ◽  
pp. 174-179
Author(s):  
A. K. Stiffler ◽  
J. L. Shearer
Keyword(s):  
Pressure Gradient ◽  
Control Region ◽  
Input Signal ◽  
Nozzle Exit ◽  
Flow Direction ◽  
Turbulent Jet ◽  
Pressure Gradients ◽  
Constant Amplitude ◽  
Transverse Pressure ◽  
Sinusoidal Excitation

A free turbulent jet is perturbed transverse to the flow direction by a sinusoidal pressure gradient near the nozzle exit. An a-c model for the jet gain, based upon the control region dynamics and a uniform deflection of the jet downstream of this region, is generally verified in conjunction with attenuated mean shear velocities. A method is given to experimentally determine the effective amplitude of the input signal at the interface of the jet.

Acoustically Induced Enhancement of Widening and Fluctuation Intensity in a Two-Dimensional Turbulent Jet

1986 ◽  
Vol 108 (3) ◽  
pp. 331-337 ◽  
Author(s):  
F. O. Thomas ◽  
V. W. Goldschmidt
Keyword(s):  
Turbulent Jet ◽  
Flow Structures ◽  
Jet Flows ◽  
Underlying Structure ◽  
Detailed Data ◽  
Initial Region ◽  
Acoustic Disturbance ◽  
Fine Grained ◽  
Turbulent Plane ◽  
Plane Jet

The enhancement of widening rate and turbulence intensity in a turbulent plane jet, due to an acoustic disturbance are considered. Detailed data at a representative Strouhal number suggest a well organized symmetric structural array in the initial region of the flow. These highly organized flow structures act as efficient agents in the transport of energy to the fine-grained turbulence, leading to greater diffusivity, enhanced turbulence and an increase in widening. The data also suggest significant differences in the underlying structure of the natural and excited jet flows, hence putting in jeopardy any generalization of coherent motions especially excited to facilitate their study.

Influence of Plasma-Induced Flow Direction on the Instability of the Jet Boundary Layer

2019 ◽  
Author(s):  
Norimasa Miyagi ◽  
Motoaki Kimura
Keyword(s):  
Boundary Layer ◽  
Nozzle Exit ◽  
Flow Direction ◽  
Plasma Actuator ◽  
Main Flow ◽  
Duty Ratio ◽  
Centerline Velocity ◽  
Type B ◽  
Induced Flow ◽  
Jet Structure

Abstract In this study, the influence of the direction of the plasma-induced flow generated by a plasma actuator (PA) on the jet flow was investigated. Nozzles equipped with two types of PAs to generate forward (Type A) and backward (Type B) flows were used in this investigation. At a duty ratio was 50%, for both Types A and B, the fluctuation due to the plasma-induced flow yielded the most stable fluctuation near the nozzle exit. In the case of the Type B PA, the centerline velocity was increased by the contraction of the main flow near the nozzle exit due to the influence of the backflow. Additionally, the fluctuation of the jet boundary layer became stronger as the duty ratio was increased. From these factors, it is considered that the backflow by the plasma induced flow effectively works on the diffusion of the jet structure.

FLOW VISUALIZATION OF SUBMERGED JETS IN NARROW CHANNELS

2009 ◽  
Vol 23 (03) ◽  
pp. 377-380
Author(s):  
JIAN-HONG SUN ◽  
CHIN-TSAU HSU
Keyword(s):  
Reynolds Numbers ◽  
Narrow Channel ◽  
Laser Induced Fluorescence ◽  
Turbulent Jet ◽  
Narrow Channels ◽  
Submerged Jets ◽  
Flow Motion ◽  
Turbulent Plane ◽  
Plane Jet ◽  
Turbulent Water

In order to study the effect of wall on the flow pattern of a submerged turbulent water jet in narrow channels, the flow field was visualized by a laser-induced fluorescence (LIF) system at different Reynolds numbers. Those images showed that flow motion in a narrow channel is different from that of a turbulent plane jet without narrow channels. There are three flow patterns in narrow channels: stable impinging, stable jet with recirculation vortices and flapping turbulent jet.

Sign in / Sign up

Export Citation Format

Share Document