Effect of flat wall length on decay and shock structure of a supersonic square wall jet

2021 ◽  
pp. 095441002110580
Author(s):  
Venkata Satya Manikanta Tammabathula ◽  
Venkata Sai Krishna Ghanta ◽  
Tharaka Narendra Sridhar Bandla
Keyword(s):  
Supersonic Jet ◽  
Leading Edge ◽  
Shock Structure ◽  
Wall Jet ◽  
Pressure Measurements ◽  
Maximum Enhancement ◽  
Flat Wall ◽  
Decay Behaviour ◽  
Core Length ◽  
Supersonic Core Length

Experiments were conducted to find the effect of wall length on the decay behaviour and shock structure of a supersonic wall jet issuing from c-d nozzle of the square-shaped exit. A straight flat wall of width same as the side length of the square was attached to the lip of the nozzle such that the leading edge of the wall and the side of the square aligned properly which allowed the supersonic jet to graze past the flat wall. Experiments were conducted with five different wall lengths, that is, [Formula: see text] = 0.5, 1, 2, 4 and 8. Wall pressure measurements were made from leading edge to the trailing edge of the wall along its centreline. Schlieren flow visualization of the jet flow over the wall for the different wall lengths revealed the shock pattern and the effect of the wall length on the shock structure. The shock structure and jet deflection were significantly affected due to the presence of the wall. There was an upward jet deflection for [Formula: see text] up to [Formula: see text] whereas a downward jet deflection was observed for [Formula: see text]. Noticeable changes in the shock structure were observed for the wall lengths up to 2 D h. The wall length also significantly affected the jet decay characteristics and supersonic core length. Maximum enhancement in jet decay and maximum reduction in supersonic core length resulted when the wall length was [Formula: see text]. However, when the wall length was increased to [Formula: see text], there was a significant reduction in jet decay and a recovery of [Formula: see text]. Presence of wall always resulted a reduction in Lsc irrespective of wall length. The wall effect was to induce a more precipitous pressure drop closer to the nozzle exit, and a more gradual drop farther from it for [Formula: see text] > [Formula: see text].

Study of Decay Characteristics of Hexagonal and Square Supersonic Jet

2017 ◽  
Vol 34 (2) ◽  
Author(s):  
Prasanta Kumar Mohanta ◽  
B. T. N. Sridhar
Keyword(s):  
Pressure Ratio ◽  
Supersonic Jet ◽  
Ambient Air ◽  
Hydraulic Diameter ◽  
Schlieren Image ◽  
Image Study ◽  
Jet Mixing ◽  
Core Length ◽  
Supersonic Core Length ◽  
The Impact

AbstractExperiments were carried on nozzles with different exit geometry to study their impact on supersonic core length. Circular, hexagonal, and square exit geometries were considered for the study. Numerical simulations and schlieren image study were performed. The supersonic core decay was found to be of different length for different exit geometries, though the throat to exit area ratio was kept constant. The impact of nozzle exit geometry is to enhance the mixing of primary flow with ambient air, without requiring tab, wire or secondary method to increase the mixing characteristics. The non-circular mixing is faster comparative to circular geometry, which leads to reduction in supersonic core length. The results depict that shorter the hydraulic diameter, the jet mixing is faster. To avoid the losses in divergent section, the cross section of throat was maintained at same geometry as the exit geometry. Investigation shows that the supersonic core region is dependent on the hydraulic diameter and the diagonal. In addition, it has been observed that number of shock cells remain the same irrespective of exit geometry shape for the given nozzle pressure ratio.

Effect of Co-Flow on Near Field Shock Structure

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
T. Srinivasarao ◽  
P. Lovaraju ◽  
E. Rathakrishnan
Keyword(s):  
Near Field ◽  
Shock Structure ◽  
Experimental Results ◽  
Underexpanded Jets ◽  
Core Length ◽  
Central Nozzle ◽  
Supersonic Core Length ◽  
Expansion Level

This paper presents the experimental results of underexpanded jets delivered from a central nozzle surrounded by a co-flow. The co-flow is found to be effective in elongating the supersonic core length of the central jet, at all levels of underexpansion. However, the expansion level of the central jet dictates the elongation caused by the co-flow.

scholarly journals Effect of Hydraulic Diameter on Potential Core Decay of Supersonic Jets

2020 ◽  
Vol 12 (1) ◽  
pp. 119-126
Author(s):  
Prasanta Kumar MOHANTA ◽  
B. T. N. SRIDHAR
Keyword(s):  
Supersonic Jet ◽  
Supersonic Jets ◽  
Hydraulic Diameter ◽  
Potential Core ◽  
Core Length ◽  
Empirical Relations ◽  
Experimental Correlation ◽  
Supersonic Core Length ◽  
Decay Pattern ◽  
Shaped Nozzle

Various studies dealing with decay characteristics of circular and noncircular supersonic jets were conducted by previous researchers. But in these studies due emphasis was not given to the hydraulic diameter (Dh), shape factor (ζ) & the nozzle lip parameters which have significant impact on the characteristics of noncircular supersonic jet. In this study, it has been shown that these parameters played a significant role on supersonic core decay characteristics [2, 3, 6] of the jet. The scope of this study included supersonic core length (Lc), decay pattern, due to noncircular shaped nozzle. In the literature, the supersonic jet characterization and the related experimental correlation are available for optimum expansion conditions whereas for other expansion (under and over) conditions the experimental correlation is barely available. While investigating experimentally, new empirical relations were obtained which were the improved forms of earlier correlations for supersonic core length [4]. For experiments, six different types of nozzles (circular, hexagon, square, triangular, elliptical and rectangular) with the same exit to throat area ratio, convergent length and divergent length were used. The results obtained from the experimentally developed correlations were coherent with numerical results, experimental data and flow visualization.

scholarly journals Scaling law for supersonic core length in circular and elliptic free jets

2021 ◽  
Vol 33 (5) ◽  
pp. 051707
Author(s):  
Arun Kumar Perumal ◽  
Ethirajan Rathakrishnan
Keyword(s):  
Scaling Law ◽  
Free Jets ◽  
Core Length ◽  
Supersonic Core Length

Influence of nozzle exit geometrical parameters on supersonic jet decay

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Prasanta Kumar Mohanta ◽  
B. T. N. Sridhar ◽  
R. K. Mishra
Keyword(s):  
Aspect Ratio ◽  
Nozzle Exit ◽  
Ambient Air ◽  
Schlieren Image ◽  
Geometrical Parameters ◽  
Image Study ◽  
Aspect Ratios ◽  
Core Length ◽  
Supersonic Core Length ◽  
The Impact

Abstract Experiments and simulations were carried on C-D nozzles with four different exit geometry aspect ratios to investigate the impact of supersonic decay characteristics. Rectangular and elliptical exit geometries were considered for the study with various aspect ratios. Numerical simulations and Schlieren image study were studied and found the agreeable logical physics of decay and spread characteristics. The supersonic core decay was found to be of different length for different exit geometry aspect ratio, though the throat to exit area ratio was kept constant to maintain the same exit Mach number. The impact of nozzle exit aspect ratio geometry was responsible to enhance the mixing of primary flow with ambient air, without requiring a secondary method to increase the mixing characteristics. The higher aspect ratio resulted in better mixing when compared to lower aspect ratio exit geometry, which led to reduction in supersonic core length. The behavior of core length reduction gives the identical signature for both under-expanded and over-expanded cases. The results revealed that higher aspect ratio of the exit geometry produced smaller supersonic core length. The aspect ratio of cross section in divergent section of the nozzle was maintained constant from throat to exit to reduce flow losses.

Tilt and Interfacial Fluid Pressure Measurements of a Disk Sliding on a Polymeric Pad

2005 ◽  
Vol 127 (1) ◽  
pp. 198-205 ◽  
Author(s):  
Sum Huan Ng ◽  
Len Borucki ◽  
C. Fred Higgs ◽  
Inho Yoon ◽  
Andre´s Osorno ◽  
...  
Keyword(s):  
Negative Pressure ◽  
Reynolds Equation ◽  
Fluid Pressure ◽  
Leading Edge ◽  
Dominant Factor ◽  
Pressure Measurements ◽  
Capacitive Sensing ◽  
One Dimensional ◽  
Pressure Mapping ◽  
Pressure Region

Previous experimental work has shown that negative fluid pressure does develop at the disk/pad interface during chemical mechanical polishing. However, these studies dealt with one-dimensional measurement and modeling. To better understand the problem, two-dimensional pressure mapping is carried out. In addition, the orientation of the disk is measured with a capacitive sensing technique. Results reveal a large negative pressure region at the disk/pad interface that is skewed toward the leading edge of the disk. The disk is also found to be leaning down toward the leading edge and toward the center of the pad. A mixed-lubrication model based on the Reynolds equation and taking into account the disk orientation angles has been developed. Modeling and experimental results show similar trends, indicating the tilting of the disk as a dominant factor in causing the negative pressure phenomenon.

Buoyant convection from horizontal surfaces at const ant pressure

1975 ◽  
Vol 68 (3) ◽  
pp. 609-624 ◽  
Author(s):  
S. C. Traugott
Keyword(s):  
Pressure Gradient ◽  
Boundary Layers ◽  
Line Source ◽  
Leading Edge ◽  
Wall Jet ◽  
Two Dimensional ◽  
Buoyant Plume ◽  
Grashof Number ◽  
Buoyancy Driven Flows ◽  
Streamwise Pressure Gradient

A two-dimensional horizontal flow is discussed, which is induced by other, buoyancy-driven flows elsewhere. It is an adaptation of the incompressible wall jet, which is driven by conditions a t the leading edge and has no streamwise pressure gradient. The relation of this flow to the classical buoyancy-driven boundary layers on inclined and horizontal surfaces is investigated, as well as its possible connexion with a two-dimensional buoyant plume driven by a line source of heat. Composite flows are constructed by patching various such solutions together. The composite flows exhibit$Gr^{\frac{1}{4}}$scaling (Grbeing the Grashof number).

scholarly journals Interpreting Aerodynamics of a Transonic Impeller from Static Pressure Measurements

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Fangyuan Lou ◽  
John Charles Fabian ◽  
Nicole Leanne Key
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Pressure Measurements ◽  
High Loss ◽  
Supersonic Inlet ◽  
Mach Numbers ◽  
Inlet Conditions

This paper investigates the aerodynamics of a transonic impeller using static pressure measurements. The impeller is a high-speed, high-pressure-ratio wheel used in small gas turbine engines. The experiment was conducted on the single stage centrifugal compressor facility in the compressor research laboratory at Purdue University. Data were acquired from choke to near-surge at four different corrected speeds (Nc) from 80% to 100% design speed, which covers both subsonic and supersonic inlet conditions. Details of the impeller flow field are discussed using data acquired from both steady and time-resolved static pressure measurements along the impeller shroud. The flow field is compared at different loading conditions, from subsonic to supersonic inlet conditions. The impeller performance was strongly dependent on the inducer, where the majority of relative diffusion occurs. The inducer diffuses flow more efficiently for inlet tip relative Mach numbers close to unity, and the performance diminishes at other Mach numbers. Shock waves emerging upstream of the impeller leading edge were observed from 90% to 100% corrected speed, and they move towards the impeller trailing edge as the inlet tip relative Mach number increases. There is no shock wave present in the inducer at 80% corrected speed. However, a high-loss region near the inducer throat was observed at 80% corrected speed resulting in a lower impeller efficiency at subsonic inlet conditions.

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