The Effect of the Nozzle Top Lip Thickness on a Two-Dimensional Wall Jet

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Rory McIntyre ◽  
Eric Savory ◽  
Hao Wu ◽  
David S.-K. Ting
Keyword(s):  
Reynolds Number ◽  
Maximum Velocity ◽  
Decay Rates ◽  
Wall Jet ◽  
Two Dimensional ◽  
Hot Wire ◽  
Nozzle Height ◽  
Flow Profiles ◽  
Velocity Decay ◽  
Jet Nozzle

The effect of the nozzle top lip thickness on a two-dimensional wall jet was examined experimentally in a wind tunnel using hot-wire anemometry. Lip thicknesses of 0.125b, 0.5b, 1b, and 2b, where b is the jet nozzle height, were considered at a Reynolds number of 30,700 based on the jet nozzle height and jet velocity. Noticeable differences in the flow profiles were observed at the jet outlet, but by 10b downstream these differences became insignificant. Different lip thicknesses resulted in different maximum velocity decay rates. The spread of the wall jet was found to be insensitive to the lip thickness.

PIV Study of Laminar Wall Jets of Non-Newtonian Fluids

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
K. F. K. Adane ◽  
M. F. Tachie
Keyword(s):  
Reynolds Number ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Reynolds Numbers ◽  
Newtonian Fluids ◽  
Jet Flows ◽  
Wall Jet ◽  
Fluid Type ◽  
Particle Image Velocimetry Technique ◽  
Velocity Decay

Three-dimensional laminar wall jet flows of shear-thinning non-Newtonian fluids have been studied using a particle image velocimetry technique. The non-Newtonian fluids were prepared from xanthan gum solutions of various concentrations. The velocity measurements were performed in various streamwise-transverse and streamwise-spanwise planes at various inlet Reynolds numbers. From these measurements, the maximum velocity decay, jet half-widths, and velocity profiles were obtained to study the effects of Reynolds number and fluid type on the characteristics of the wall jet flows. It was observed that the maximum velocity decay and jet half-widths depend on inlet Reynolds number and fluid but the similarity velocities profiles are independent of both Reynolds number and specific fluid type.

Mean Flow Downstream of Two-Dimensional Roughness Elements

1989 ◽  
Vol 111 (2) ◽  
pp. 149-153 ◽  
Author(s):  
E. Logan ◽  
P. Phataraphruk
Keyword(s):  
Reynolds Number ◽  
Cross Section ◽  
Pipe Flow ◽  
Rectangular Cross Section ◽  
Roughness Element ◽  
Two Dimensional ◽  
Hot Wire ◽  
Mean Flow ◽  
Roughness Elements ◽  
Three Stages

The response of a fully developed pipe flow to wall mounted roughness elements of rectangular cross section was investigated experimentally using a probe with a single hot-wire. Four heights of rectangular, ring-type elements were installed rigidly in a 63.5-mm diameter, smooth-walled, circular pipe in which air was flowing at a Reynolds number of 50,000. After passing over the roughness element, the flow recovery occurred in three stages. The three flow regions are delineated, and the velocity profiles for each are correlated.

Turbulence Measurements in the Corner Wall Jet

2014 ◽  
Author(s):  
Barrett Poole ◽  
Joseph W. Hall
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Wall Jet ◽  
Hot Wire ◽  
Turbulence Measurements ◽  
Vertical Growth ◽  
The Mean ◽  
Turbulent Flow Field

The corner wall jet is similar to the standard three-dimensional wall jet with the exception that one half of the surface has been rotated counter-clockwise by 90 degrees. The corner wall jet investigated here is formed using a long round pipe with a Reynolds number of 159,000. Contours of the mean and turbulent flow field were measured using hot-wire anemometry. The results indicate that the ratio of lateral to vertical growth in the corner wall jet is approximately half of that in a standard turbulent three-dimensional wall jet.

scholarly journals Numerical Study on Plane and Radial Wall Jets to Validate the 2D Assumption for an Idealized Downburst Outflow

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Yongli Zhong ◽  
Zhitao Yan ◽  
Yan Li ◽  
Jie Luo ◽  
Hua Zhang
Keyword(s):  
Reynolds Number ◽  
Numerical Study ◽  
Critical Value ◽  
Plane Wall ◽  
Cloud Base ◽  
Jet Flows ◽  
Wall Jet ◽  
Wall Jets ◽  
Radial Wall ◽  
Velocity Decay

Turbulent radial and plane wall jets have been extensively investigated both experimentally and numerically over the past few decades. Previous studies mostly focused on the heat and mass transfers involved in jet flows. In this study, a comprehensive investigation was conducted on turbulent radial and plane wall jets, considering both jet spread and velocity decay for different parameters. The numerical results were compared with existing experimental measurements. The comparison focused on the velocity profile, jet spread, and velocity decay, and revealed that the Reynolds stress model (RSM) performs well in the simulation of both radial and plane wall jets. The results show that with a typical ratio of cloud base height to diameter for most downburst events, the effects of nozzle height and Reynolds number on the evolution of the radial wall jet are not significant. Both the jet spread and velocity decay exhibit a clear dependence on the Reynolds number below a critical value. Above this critical value, the plane wall jet becomes asymptotically independent of the Reynolds number. The co-flow was found to have a significant influence on the evolution of the plane wall jet. Comparatively, the jet spread and velocity of the radial wall jet were faster than those of the plane jet. For applications in civil engineering, it is valid to approximate the downburst outflow with a two-dimensional (2D) assumption from the perspective of longitudinal evolution of the flows.

Plane Turbulent Wall Jet Flow Development and Friction Factor

1963 ◽  
Vol 85 (1) ◽  
pp. 47-53 ◽  
Author(s):  
G. E. Myers ◽  
J. J. Schauer ◽  
R. H. Eustis
Keyword(s):  
Maximum Velocity ◽  
Velocity Profiles ◽  
Wall Jet ◽  
Shearing Stress ◽  
Integral Methods ◽  
Velocity Decay ◽  
Wall Jet Flow ◽  
Turbulent Wall ◽  
Momentum Integral ◽  
Wall Shearing Stress

An investigation of the jet development, the velocity profiles, and the wall shearing stress in a two-dimensional, incompressible, turbulent wall jet was undertaken. The maximum velocity decay, jet thickness, and the shearing stress are predicted analytically by momentum-integral methods. Experimental data concerning velocity profiles, velocity decay, and jet thickness agree well with previous investigators. The wall shearing stress was measured by a hot-film technique and the results help to resolve a wide divergence between the experimental values of other investigators.

The Stability of a Two-dimensional Wall Jet

1977 ◽  
Vol 28 (4) ◽  
pp. 235-246 ◽  
Author(s):  
Yutaka Tsuji ◽  
Yoshinobu Morikawa ◽  
Toshihiro Nagatani ◽  
Masaaki Sakou
Keyword(s):  
Reynolds Number ◽  
Neutral Curve ◽  
Stable Region ◽  
Wall Jet ◽  
Two Dimensional ◽  
Linear Region ◽  
Stability Calculation ◽  
Stable Curve ◽  
The Stability ◽  
Small Disturbances

SummaryThe stability of a two-dimensional wall jet was studied theoretically and experimentally. As a result of the linear stability calculation, it was found that one eigenmode is separated into two modes when the Reynolds number is large, and inside a neutral stable curve in the α, R-plane there exists another neutral curve enclosing a stable region. Experimental results of small disturbances were compared with calculated results; agreement between them was satisfactory. It was found, further, that subharmonics of a predominant disturbance velocity component appear in the non-linear region.

An experimental investigation of the instability of a two-dimensional jet at low Reynolds numbers

1964 ◽  
Vol 20 (2) ◽  
pp. 337-352 ◽  
Author(s):  
Hiroshi Sato ◽  
Fujihiko Sakao
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Maximum Velocity ◽  
Reynolds Numbers ◽  
Two Dimensional ◽  
Low Reynolds Numbers ◽  
Laminar Jet ◽  
Artificial Disturbance ◽  
Low Reynolds ◽  
The Stability

An experimental investigation was made of the stability of a two-dimensional jet at low Reynolds numbers with extremely small residual disturbances both in and around the jet. The velocity distribution of a laminar jet is in agreement with Bickley's theoretical result. The stability and transition of a laminar jet are characterized by the Reynolds number based on the slit width and the maximum velocity of the jet. When the Reynolds number is less than 10, the whole jet is laminar. When the Reynolds number is between 10 and around 50, periodic velocity fluctuations are found in the jet. They die out as they travel downstream without developing into irregular fluctuations. When the Reynolds number exceeds about 50, periodic fluctuations develop into irregular, turbulent fluctuations. The frequency of the periodic fluctuation is roughly proportional to the square of the jet velocity.The stability of the jet against an artificially imposed disturbance was also investigated. Sound was used as an artificial disturbance. The disturbance is either amplified or damped in the jet depending on its frequency. The conventional stability theory was modified by considering the streamwise increase of Reynolds number. The experimental results are in agreement with the theoretical results.

Reynolds Number Effects on the Characteristics of Twin Jets Interacting With a Free Surface

2016 ◽  
Author(s):  
M. S. Rahman ◽  
E. M. Nabess ◽  
M. F. Tachie
Keyword(s):  
Reynolds Number ◽  
Free Surface ◽  
Maximum Velocity ◽  
Mean Velocity ◽  
Free Jet ◽  
Turbulent Characteristics ◽  
Reynolds Number Effects ◽  
Velocity Decay ◽  
Twin Jets ◽  
Velocity Measuring

The effects of Reynolds number on the turbulent characteristics of surface attaching twin jet were investigated experimentally. Particle image velocimetry was used as the velocity measuring technique. Twin jets were produced using square orifice nozzle pair. The Reynolds numbers based on the jet exit velocity and the nozzle width were varied from 2620 to 7900. The offset height ratio was fixed at 2 during the experiments. The jet reattached to the free surface and the reattachment length decreased with increase of Reynolds number. Free surface showed significant effect on the maximum velocity decay, jet spread, streamwise mean velocity distribution, Reynolds shear and normal stresses in the upper jet. The decay and spread rate of the lower jet was comparable to free jet due to less confinement effect. The mean and turbulent quantities reported herein were nearly independent of Reynolds number. Proper orthogonal decomposition was performed to reveal the dynamic role of the energetic structures embedded within the flow.

scholarly journals Two-dimensional energy spectra in high-Reynolds-number turbulent boundary layers

2017 ◽  
Vol 826 ◽  
Author(s):  
Dileep Chandran ◽  
Rio Baidya ◽  
Jason P. Monty ◽  
Ivan Marusic
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Reynolds Numbers ◽  
Streamwise Velocity ◽  
Spatial Spectrum ◽  
Two Dimensional ◽  
Hot Wire ◽  
Self Similarity ◽  
Low Reynolds Numbers ◽  
High Reynolds

Here, we report the measurements of two-dimensional (2-D) spectra of the streamwise velocity ($u$) in a high-Reynolds-number turbulent boundary layer. A novel experiment employing multiple hot-wire probes was carried out at friction Reynolds numbers ranging from 2400 to 26 000. Taylor’s frozen turbulence hypothesis is used to convert temporal-spanwise information into a 2-D spatial spectrum which shows the contribution of streamwise ($\unicode[STIX]{x1D706}_{x}$) and spanwise ($\unicode[STIX]{x1D706}_{y}$) length scales to the streamwise variance at a given wall height ($z$). At low Reynolds numbers, the shape of the 2-D spectra at a constant energy level shows$\unicode[STIX]{x1D706}_{y}/z\sim (\unicode[STIX]{x1D706}_{x}/z)^{1/2}$behaviour at larger scales, which is in agreement with the existing literature at a matched Reynolds number obtained from direct numerical simulations. However, at high Reynolds numbers, it is observed that the square-root relationship tends towards a linear relationship ($\unicode[STIX]{x1D706}_{y}\sim \unicode[STIX]{x1D706}_{x}$), as required for self-similarity and predicted by the attached eddy hypothesis.

Sign in / Sign up

Export Citation Format

Share Document