TECHNICAL NOTE. SIGNIFICANCE OF THE BOUNDARY SHEAR STRESS/MOMENTUM FLUX RATIO.

Frequent floods around the globe including recent events in several states in Malaysia have damaged the residential properties, infrastructures and crops or even deaths. Clearing vegetations or trees on the floodplain has been pointed out as a contributing factor to the damages. Thus, the influence of floodplain vegetation on the river hydraulics during flooding must be better understood. The hydraulics of flood flows in non-erodible vegetated meandering channel was experimented in the laboratory where two-lined steel rods were installed along a riparian zone to simulate as trees. The stage-discharge relationship, flow resistance, depth-averaged velocity, streamwise vorticity and boundary shear stress patterns during shallow and deep flood inundations were studied. The findings showed that floodplain vegetation had increased the channel flow depth by 32% and its flow resistance. The velocity in vegetated zone was lowered and the shear stress reduced by 86.5% to 91% along the river meander. In addition, the trees also limit flow interaction between main channel and floodplain

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Volumetric Velocimetry Measurements of Film Cooling Jets

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4041206 ◽

2018 ◽

Vol 141 (3) ◽

Author(s):

Artur Joao Carvalho Figueiredo ◽

Robin Jones ◽

Oliver J. Pountney ◽

James A. Scobie ◽

Gary D. Lock ◽

...

Keyword(s):

Film Cooling ◽

Momentum Flux ◽

Three Dimensional ◽

Flux Ratio ◽

Quality Data ◽

Data Set ◽

Momentum Flux Ratio ◽

Jet In Crossflow ◽

Lift Off ◽

Induced Velocity

This paper presents volumetric velocimetry (VV) measurements for a jet in crossflow that is representative of film cooling. VV employs particle tracking to nonintrusively extract all three components of velocity in a three-dimensional volume. This is its first use in a film-cooling context. The primary research objective was to develop this novel measurement technique for turbomachinery applications, while collecting a high-quality data set that can improve the understanding of the flow structure of the cooling jet. A new facility was designed and manufactured for this study with emphasis on optical access and controlled boundary conditions. For a range of momentum flux ratios from 0.65 to 6.5, the measurements clearly show the penetration of the cooling jet into the freestream, the formation of kidney-shaped vortices, and entrainment of main flow into the jet. The results are compared to published studies using different experimental techniques, with good agreement. Further quantitative analysis of the location of the kidney vortices demonstrates their lift off from the wall and increasing lateral separation with increasing momentum flux ratio. The lateral divergence correlates very well with the self-induced velocity created by the wall–vortex interaction. Circulation measurements quantify the initial roll up and decay of the kidney vortices and show that the point of maximum circulation moves downstream with increasing momentum flux ratio. The potential for nonintrusive VV measurements in turbomachinery flow has been clearly demonstrated.

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Modelling boundary shear stress in highly sinuous meandering channels

ISH Journal of Hydraulic Engineering ◽

10.1080/09715010.2013.860733 ◽

2013 ◽

Vol 20 (2) ◽

pp. 161-168 ◽

Cited By ~ 1

Author(s):

M. Patnaik ◽

K.C. Patra ◽

K.K. Khatua ◽

L. Mohanty

Keyword(s):

Shear Stress ◽

Meandering Channels ◽

Boundary Shear ◽

Boundary Shear Stress

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Modeling effects of bank friction and woody bank vegetation on channel flow and boundary shear stress in the Rio Puerco, New Mexico

Journal of Geophysical Research Atmospheres ◽

10.1029/2005jf000322 ◽

2005 ◽

Vol 110 (F4) ◽

pp. n/a-n/a ◽

Cited By ~ 33

Author(s):

E. R. Griffin ◽

J. W. Kean ◽

K. R. Vincent ◽

J. D. Smith ◽

J. M. Friedman

Keyword(s):

Shear Stress ◽

New Mexico ◽

Channel Flow ◽

Boundary Shear ◽

Boundary Shear Stress

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Drop Size Characteristics of Forward Angled Injectors in Subsonic Cross Flows

ASME 2013 Gas Turbine India Conference ◽

10.1115/gtindia2013-3706 ◽

2013 ◽

Author(s):

Venkat S. Iyengar ◽

Sathiyamoorthy Kumarasamy ◽

Srinivas Jangam ◽

Manjunath Pulumathi

Keyword(s):

Gas Turbine ◽

Test Section ◽

Momentum Flux ◽

Drop Size ◽

Cross Flow ◽

Flux Ratio ◽

Liquid Jet ◽

Axial Distance ◽

Momentum Flux Ratio ◽

Spray Plume

Cross flow fuel injection is a widely used approach for injecting liquid fuel in gas turbine combustors and afterburners due to the higher penetration and rapid mixing of fuel and the cross flowing airstream. Because of the very limited residence time available in these combustors it is essential to ensure that smaller drop sizes are generated within a short axial distance from the injector in order to promote effective mixing. This requirement calls for detailed investigations into spray characteristics of different injector configurations in a cross-flow environment for identifying promising configurations. The drop size characteristics of a liquid jet issuing from a forward angled injector into a cross-flow of air were investigated experimentally at conditions relevant to gas turbine afterburners. A rig was designed and fabricated to investigate the injection of liquid jet in subsonic cross-flow with a rectangular test section of cross section measuring 50 mm by 70 mm. Experiments were done with a 10 degree forward angled 0.8 mm diameter plain orifice nozzle which was flush mounted on the bottom plate of test section. Laser diffraction using Malvern Spraytec particle analyzer was used to measure drops size and distributions in the near field of the spray. Measurements were performed at a distance of 70 mm from the injector at various locations along the height of the spray plume for a reasonable range of liquid flow rates as in practical devices. The sprays were characterized using the non dimensional parameters such as the Weber number and the momentum flux ratio and drop sizes were measured at three locations along the height of the spray from the bottom wall. The momentum flux ratio was varied from 5 to 25. Results indicate that with increase in momentum flux ratio the SMD reduced at the specific locations and an higher overall SMD was observed as one goes from the bottom to the top of the spray plume. This was accompanied by a narrowing of the drop size distribution.

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Liquid Jets in Subsonic Air Crossflow at Elevated Pressure

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4028565 ◽

2014 ◽

Vol 137 (4) ◽

Cited By ~ 22

Author(s):

Jinkwan Song ◽

Charles Cary Cain ◽

Jong Guen Lee

Keyword(s):

Weber Number ◽

Momentum Flux ◽

Drop Size ◽

Density Ratio ◽

Flux Ratio ◽

Mie Scattering ◽

Air Pressure ◽

Scattering Intensity ◽

Nozzle Orifice ◽

Momentum Flux Ratio

The breakup, penetration, droplet size, and size distribution of a Jet A-1 fuel in air crossflow has been investigated with focus given to the impact of surrounding air pressure. Data have been collected by particle Doppler phased analyzer (PDPA), Mie-scattering with high speed photography augmented by laser sheet, and Mie-scattering with intensified charge-coupled device (ICCD) camera augmented by nanopulse lamp. Nozzle orifice diameter, do, was 0.508 mm and nozzle orifice length to diameter ratio, lo/do, was 5.5. Air crossflow velocities ranged from 29.57 to 137.15 m/s, air pressures from 2.07 to 9.65 bar, and temperature held constant at 294.26 K. Fuel flow provides a range of fuel/air momentum flux ratio (q) from 5 to 25 and Weber number from 250 to 1000. From the results, adjusted correlation of the mean drop size has been proposed using drop size data measured by PDPA as follows: (D0/D32)=0.267Wea0.44q0.08(ρl/ρa)0.30(μl/μa)-0.16. This correlation agrees well and shows roles of aerodynamic Weber number, Wea, momentum flux ratio, q, and density ratio, ρl/ρa. Change of the breakup regime map with respect to surrounding air pressure has been observed and revealed that the boundary between each breakup modes can be predicted by a transformed correlation obtained from above correlation. In addition, the spray trajectory for the maximum Mie-scattering intensity at each axial location downstream of injector is extracted from averaged Mie-scattering images. From these results, correlations with the relevant parameters including q, x/do, density ratio, viscosity ratio, and Weber number are made over a range of conditions. According to spray trajectory at the maximum Mie-scattering intensity, the effect of surrounding air pressure becomes more important in the farfield. On the other hand, effect of aerodynamic Weber number is more important in the nearfield.

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