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.

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.

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.

scholarly journals Study of decay characteristics of rectangular and elliptical supersonic jets

2017 ◽  
Vol 21 (6 Part B) ◽  
pp. 3001-3010 ◽  
Author(s):  
Prasanta Mohanta ◽  
B.T.N. Sridhar
Keyword(s):  
Total Pressure ◽  
Empirical Relation ◽  
Ambient Air ◽  
Supersonic Jets ◽  
Schlieren Image ◽  
Pressure Data ◽  
Image Study ◽  
Core Length ◽  
Circular Jets ◽  
Supersonic Core Length

Experiments were carried out to study the decay characteristics of non-circular supersonic jets issued from rectangular and elliptical nozzles, and results were compared with circular case. Numerical simulations and Schlieren image study were carried out to validate the experimental results obtained from total pressure data. The supersonic core lengths of the jets were found to be different for different exit shaped geometries and area ratio for those nozzles was same. To avoid the losses in divergent section, the shape of cross-section of throat was maintained same that of as the exit. The exit shape geometry played the important role to enhance the mixing of the jet with ambient air, without requiring secondary method to increase the mixing characteristics. The mixing with ambient air in case of non-circular jets was more intense when compared to that of circular jets, which resulted in reduction of supersonic core length. The behavior of supersonic core length had identical signature for both under-expanded and over-expanded operation. The supersonic core length was characterized by exit shape factor. In 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 correlations are barely available. While investigating experimentally, a new empirical relation was obtained which was the improved form of earlier correlations for supersonic core length. The current results obtained from three different methods (total pressure data, schlieren image and numerical simulation) had shown the reasonable agreement with the experimentally obtained relation.

Numerical Investigation on Effect of Aspect Ratio of Axisymmetric Circumferential Groove Casing Treatment Coupled to a Transonic Axial Flow Compressor Stage

2015 ◽  
Author(s):  
Nishit J. Mehta ◽  
Dilipkumar Bhanudasji Alone ◽  
Harish S. Choksi
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Flow Behavior ◽  
Geometrical Parameters ◽  
Compressor Stage ◽  
Casing Treatment ◽  
Transonic Compressor ◽  
Circumferential Groove ◽  
Aspect Ratios ◽  
The Impact

While the effects of axisymmetric casing treatment on performance of an axial compressor stage have been extensively studied numerically as well as experimentally, the major geometrical parameters which govern these effects have been identified. Studies are now focused on understanding how each of these parameters individually impacts the performance of a casing treatment. The present work aims to study the impact on performance of casing treatment geometry when aspect ratio of the grooves is varied in a circumferential groove casing treatment. The compressor geometry chosen for this study has design characteristics of a transonic compressor stage. Flow field solutions were derived for baseline model by solving steady state 3-D Reynolds-Averaged Navier-Stokes (RANS) equations for three grid densities and the grid independence was proved. The basic casing treatment geometry has 10 circumferential grooves of width 4mm and axial spacing of 2mm between each groove. The aspect ratio was varied by changing the depth of the grooves in each case. These casing treatment geometries were superimposed over the rotor domain with the grooves extending over the entire blade tip chord and flow field solutions were again obtained for various aspect ratios of grooves. These results depict improvement in the range of operation in terms of mass flow rate. Results also show that the aspect ratio of the grooves significantly influences the overall effectiveness of casing treatment on the performance of compressor stage. Improvement in overall compressor efficiency is noted with lower aspect ratio casing treatments when compared to those with higher aspect ratios, however, the range improvement is higher with higher aspect ratios. It is also observed that, after a certain depth of grooves is reached, there is no significant improvement in performance on further increasing the depth and hence the aspect ratio. Post processing results of the flow solutions are presented which confirm the trends and show that the flow behavior near rotor tip governs this effect.

scholarly journals Aspect Ratio Driven Relationship between Nozzle Internal Flow and Supersonic Jet Mixing

Aerospace ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 78
Author(s):  
Kalyani Bhide ◽  
Kiran Siddappaji ◽  
Shaaban Abdallah
Keyword(s):  
Boundary Layer ◽  
Aspect Ratio ◽  
Nozzle Exit ◽  
Supersonic Jet ◽  
Internal Flow ◽  
Shear Stresses ◽  
Loss Mechanism ◽  
Potential Core ◽  
Jet Mixing ◽  
Aspect Ratios

This work attempts to connect internal flow to the exit flow and supersonic jet mixing in rectangular nozzles with low to high aspect ratios (AR). A series of low and high aspect ratio rectangular nozzles (design Mach number = 1.5) with sharp throats are numerically investigated using steady state Reynolds-averaged Navier−Stokes (RANS) computational fluid dynamics (CFD) with k-omega shear stress transport (SST) turbulence model. The numerical shadowgraph reveals stronger shocks at low ARs which become weaker with increasing AR due to less flow turning at the throat. Stronger shocks cause more aggressive gradients in the boundary layer resulting in higher wall shear stresses at the throat for low ARs. The boundary layer becomes thick at low ARs creating more aerodynamic blockage. The boundary layer exiting the nozzle transforms into a shear layer and grows thicker in the high AR nozzle with a smaller potential core length. The variation in the boundary layer growth on the minor and major axis is explained and its growth downstream the throat has a significant role in nozzle exit flow characteristics. The loss mechanism throughout the flow is shown as the entropy generated due to viscous dissipation and accounts for supersonic jet mixing. Axis switching phenomenon is also addressed by analyzing the streamwise vorticity fields at various locations downstream from the nozzle exit.

scholarly journals Indentation of an S2 Floating Ice Sheet in the Brittle Range

1983 ◽  
Vol 4 ◽  
pp. 180-187 ◽  
Author(s):  
B. Michel ◽  
D. Blanchet
Keyword(s):  
Aspect Ratio ◽  
Research Work ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Theory Of Elasticity ◽  
Maximum Pressure ◽  
Shear Cracks ◽  
Aspect Ratios ◽  
Two Parameters ◽  
The Impact

The problem of a floating ice sheet hitting a structure with a vertical face appears to be a simple one but, in fact, has only been solved for a limited number of cases. Research work on this question usually reports on an indentation coefficient which relates the average pressure on the indenter to the uniaxial crushing strength of the ice. Very few tests have been made in the brittle range of ice failure. In this particular area of study, this paper reports on 27 tests that were conducted in a cold-room water basin where controlled S2floating ice sheets were produced with a surface area of 4 × 4 m, three sides being fully restrained and the other, freely float! no, being submitted to the impact of the moving indenter. All tests were carried out at computed indentation rates varying from 0.017 to 0.34 s-1. In this range this ice would normally be considered to act as a brittle material. The thickness of the ice sheets varied from 1.2 to 9.0 cm and the indenter width from 5 cm to 1 m. Overall, the aspect ratio relating these two parameters could be varied from 0.5 to 83.Results have shown that for aspect ratios <5, there was an important oscillatory effect which caused the formation of pi asti fi ed triangles in front of the indenter, increasing its resistance as it would under ductile conditions. Because of this plastification, an extrusion effect appeared in front of the indenter as the broken ice crystals were blown up and down in front of the fast-moving indenter. The theory of plasticity which gives an indentation coefficient of 2.97 seems to apply in this case. Another mode of failure which occurred with aspect ratios 5 was cleavage in the plane of the ice sheet which also gives a higher indentation coefficient for S2ice, but of the same order of magnitude as previously.For intermediate values of the aspect ratio, between 5 and 20, the theory of elasticity used by Michel (1978) seems to apply well. Shear cracks are first formed on both sides of the square indenter and control the maximum pressure when they propagate inside forming big triangles in front of it.Finally, for aspect ratios ~>20, buckling of the ice occurs, either after or at the same time as the formation of wedges, together with a reduction in the indentation coefficient to a value close to that given by the theory of buckling of a truncated 45° wedge with a hinged edge.

Geometrical Effects of Cabinet Size and Aspect Ratio on Heat and Mass Transfer During Open Door Conditions

2005 ◽  
Author(s):  
W. Terrell
Keyword(s):  
Mass Transfer ◽  
Aspect Ratio ◽  
Heat And Mass Transfer ◽  
Ambient Air ◽  
Open Door ◽  
Nusselt Numbers ◽  
Aspect Ratios ◽  
Mass Fluxes ◽  
Geometrical Effects ◽  
Aluminum Plates

The goal of this paper is to examine the effects of size and aspect ratio (H/L) of open cavities on heat and mass transfer during open door conditions of refrigerator cabinets. An experimental investigation was conducted using test cavities constructed from foam board insulation and interior covered with aluminum plates acting as calorimeters. Various size cavities with heights of 15.24 cm, 30.48 cm, and 45.72 cm along with aspect ratios of 0.5, 1.0, and 2.0 were tested. Cavities were heated to an initial temperature of 50°C, 60°C, 70°C, and 80°C before being exposed to the ambient air. In addition, tests were conducted in which the cavities were cooled before being exposed to the ambient. The relative humidity was varied from 60% to 75% and initial temperatures varied from 5°C, 1°C, and −5°C. The cavity mass fluxes were measured to validate the heat/mass transfer analogy for the tests. Experimental results were also presented for Rayleigh numbers from 5.88 × 106 to 2.21 × 108 with Nusselt numbers ranging from 15.48 to 53.51. The Nusselt numbers for cavities with an aspect ratio of one and two were in good agreement with each other. The Nusselt numbers for the cavity with an aspect ratio of 0.5 were slightly lower than the other cavities at given Rayleigh values.

scholarly journals Characterization of Stereolithography Printed Soft Tooling for Micro Injection Molding

Micromachines ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 819 ◽  
Author(s):  
Daniel Dempsey ◽  
Sean McDonald ◽  
Davide Masato ◽  
Carol Barry
Keyword(s):  
Aspect Ratio ◽  
Injection Molding ◽  
Raw Materials ◽  
Tool Material ◽  
Mold Temperature ◽  
Micro Injection Molding ◽  
Digital Light Processing ◽  
Electron Microscopies ◽  
Aspect Ratios ◽  
The Impact

The use of microfeature-enabled devices, such as microfluidic platforms and anti-fouling surfaces, has grown in both potential and application in recent years. Injection molding is an attractive method of manufacturing these devices due to its excellent process throughput and commodity-priced raw materials. Still, the manufacture of micro-structured tooling remains a slow and expensive endeavor. This work investigated the feasibility of utilizing additive manufacturing, specifically a Digital Light Processing (DLP)-based inverted stereolithography process, to produce thermoset polymer-based tooling for micro injection molding. Inserts were created with an array of 100-μm wide micro-features, having different heights and thus aspect ratios. These inserts were molded with high flow polypropylene to investigate print process resolution capabilities, channel replication abilities, and insert wear and longevity. Samples were characterized using contact profilometry as well as optical and scanning electron microscopies. Overall, the inserts exhibited a maximum lifetime of 78 molding cycles and failed by cracking of the entire insert. Damage was observed for the higher aspect ratio features but not the lower aspect ratio features. The effect of the tool material on mold temperature distribution was modeled to analyze the impact of processing and mold design.

Modeling squirt dispersion and attenuation in fluid-saturated rocks using pressure dependency of dry ultrasonic velocities

Geophysics ◽  
2012 ◽  
Vol 77 (3) ◽  
pp. WA157-WA168 ◽  
Author(s):  
Osni Bastos de Paula ◽  
Marina Pervukhina ◽  
Dina Makarynska ◽  
Boris Gurevich
Keyword(s):  
Aspect Ratio ◽  
Elastic Properties ◽  
Elastic Moduli ◽  
Pore Space ◽  
Geometrical Parameters ◽  
Laboratory Measurements ◽  
Significant Linear Trend ◽  
Aspect Ratios ◽  
Pressure Dependency ◽  
Dispersion And Attenuation

Modeling dispersion and attenuation of elastic waves in fluid-saturated rocks due to squirt flow requires the knowledge of a number of geometrical parameters of the pore space, in particular, the characteristic aspect ratio of the pores. These parameters are usually inferred by fitting measurements on saturated rocks to model predictions. To eliminate such fitting and thus make the model more predictive, we propose to recover the geometrical parameters of the pore space from the pressure dependency of elastic moduli on dry samples. Our analysis showed that the pressure dependency of elastic properties of rocks (and their deviation from Gassmann’s prediction) at ultrasonic frequencies is controlled by the squirt flow between equant, stiff, and so-called intermediate pores (with aspect ratios between [Formula: see text]). Such intermediate porosity is expected to close at confining pressures of between 200 and 2000 MPa, and thus cannot be directly obtained from ultrasonic experiments performed at pressures below 50 MPa. However, the presence of this intermediate porosity is inferred from the significant linear trend in the pressure dependency of elastic properties of the dry rock and the difference between the bulk modulus of the dry rock computed for spherical pores and the measured modulus at 50 MPa. Moreover, we can infer the magnitude of the intermediate porosity and its characteristic aspect ratio. Substituting these parameters into the squirt model, we have computed elastic moduli and velocities of the water-saturated rock and compared these predictions against laboratory measurements of these velocities. The agreement is good for a number of clean sandstones, but not unexpectedly worse for a broad range of shaley sandstones. Our predictions showed that dispersion and attenuation caused by the squirt flow between compliant and stiff pores may occur in the seismic frequency band. Confirmation of this prediction requires laboratory measurements of elastic properties at these frequencies.

Nozzle Aspect Ratio Effect on Supersonic Elliptic Jet Mixing

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
S. M. Aravindh Kumar ◽  
E. Rathakrishnan
Keyword(s):  
Aspect Ratio ◽  
Nozzle Exit ◽  
Pressure Gradients ◽  
Ratio Effect ◽  
Jet Mixing ◽  
Free Jet ◽  
Aspect Ratios ◽  
Nozzle Pressure ◽  
Axis Switching ◽  
The Waves

Nozzle aspect ratio effect on the mixing of Mach 2 elliptic free jet, issuing from convergent–divergent elliptic nozzles of aspect ratios 2, 3, and 4, in the presence of adverse and marginally favorable pressure gradients at the nozzle exit has been studied experimentally. The results show that AR4 jet enjoys better mixing than AR2 and AR3 jets at all nozzle pressure ratios. The AR2 and AR3 jets displayed axis switching, whereas there is no axis switching for AR4 jet. The shadowgraph shows that the waves in AR4 jet are weaker than those in AR2 and AR3 jets.

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