Exploratory study of turbulent structure of a compressible shear layer using fluctuating pitot pressure measurements

1992 ◽  
Vol 12-12 (4-5) ◽  
pp. 293-306 ◽  
Author(s):  
Y. R. Shau ◽  
D. S. Dolling
Keyword(s):  
Shear Layer ◽  
Exploratory Study ◽  
Turbulent Structure ◽  
Pressure Measurements ◽  
Pitot Pressure

Effects of Density and Blowing Ratios on the Turbulent Structure and Effectiveness of Film-Cooling

2018 ◽  
Author(s):  
Zachary T. Stratton ◽  
Tom I-P. Shih
Keyword(s):  
Shear Layer ◽  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Turbulent Structure ◽  
Reverse Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Turbulent Fluctuations

Large eddy simulations (LES) were performed to investigate film cooling of a flat plate, where the cooling jets issued from a plenum through one row of circular holes of diameter D and length 4.7D that are inclined at 35° relative to the plate. The focus is on understanding the turbulent structure of the film-cooling jet and the film-cooling effectiveness. Parameters studied include blowing ratio (BR = 0.5 and 1.0) and density ratio (DR = 1.1 and 1.6). Also, two different boundary layers (BL) upstream of the film-cooling hole were investigated — one in which a laminar BL was tripped to become turbulent from near the leading edge of the flat plate, and another in which a mean turbulent BL is prescribed directly. The wall-resolved LES solutions generated were validated by comparing its time-averaged values with data from PIV and thermal measurements. Results obtained show that having an upstream BL that does not have turbulent fluctuations enhances the cooling effectiveness significantly at low velocity ratios (VR) when compared to an upstream BL that resolved the turbulent fluctuations. However, these differences diminish at higher VRs. Instantaneous flow reveals a bifurcation in the jet vorticity as it exits the hole at low VRs, one branch forming the shear-layer vortex, while the other forms the counter-rotating vortex pair. At higher VRs, the shear layer vorticity is found to reverse direction, changing the nature of the turbulence and the heat transfer. Results obtained also show the strength and structure of the turbulence in the film-cooling jet to be strongly correlated to VR.

Pitot pressure measurements in a supersonic steam jet

2014 ◽  
Vol 58 ◽  
pp. 56-61 ◽  
Author(s):  
Ghassan Al-Doori ◽  
David R. Buttsworth
Keyword(s):  
Pressure Measurements ◽  
Pitot Pressure

scholarly journals Effect of the Pitot Tube on Measurements in Supersonic Axisymmetric Underexpanded Microjets

Micromachines ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 235 ◽  
Author(s):  
Sergey Mironov ◽  
Vladimir Aniskin ◽  
Tatiana Korotaeva ◽  
Ivan Tsyryulnikov
Keyword(s):  
Wave Structure ◽  
Pitot Tube ◽  
Pressure Measurements ◽  
Turbulent Transition ◽  
Gas Dynamic ◽  
Pitot Pressure ◽  
Supersonic Core Length ◽  
Pitot Microtube ◽  
Unsteady Jet ◽  
Jet Axis

This paper describes the results of methodical investigations of the effect of the Pitot tube on measurements of gas-dynamic parameters of supersonic axisymmetric underexpanded real and model microjets. Particular attention is paid to distortions of Pitot pressure variations on the jet axis associated with the wave structure of the jet and to distortions of the supersonic core length. In experiments with model jets escaping from nozzles with diameters ranging from 0.52 to 1.06 mm into the low-pressure chamber, the measurements are performed by the Pitot tubes 0.05 to 2 mm in diameter. The results are analyzed together with the earlier obtained data for real microjets escaping from nozzles with diameters ranging from 10 to 340 µm where the parameters of real microjets were determined by the Pitot microtube 12 µm in diameter. Interaction of the Pitot tube with an unsteady jet in the laminar-turbulent transition region is investigated; the influence of this interaction on Pitot pressure measurements is determined, and a physical interpretation of this phenomenon is provided.

A gun tunnel investigation of hypersonic free shear layers in a planar duct

1995 ◽  
Vol 299 ◽  
pp. 133-152 ◽  
Author(s):  
D. R. Buttsworth ◽  
R. G. Morgan ◽  
T. V. Jones
Keyword(s):  
Mach Number ◽  
High Speed ◽  
Mixing Layer ◽  
Spreading Rate ◽  
Shear Layers ◽  
Pressure Measurements ◽  
Rate Asymmetry ◽  
Pitot Pressure ◽  
Free Shear Layers ◽  
Mach 3

An experimental investigation of high Mach number free shear layers has been undertaken. The experiments were performed using a Mach 7 gun tunnel facility and a planar duct with injection from the base of a central strut producing a Mach 3 flow parallel to the gun tunnel stream. This configuration is relevant to the development of efficient scramjet propulsion, and the gun tunnel Mach number is significantly higher than the majority of previous supersonic turbulent mixing layer investigations reported in the open literature. Schlieren images and Pitot pressure measurements were obtained at four different convective Mach numbers ranging from 0 to 1.8. Only small differences between the four cases were detected, and the relatively large high-speed boundary layers at the trailing edge of the struct injector appear to strongly influence the shear layer development in each case. The Pitot pressure measurements indicated that, on average, the free shear layers all spread into the Mach 3 stream at an angle of approximately 1.4°, while virtually no spreading into the Mach 7 stream was detected until all of the low-speed stream was entrained. The free shear layers were simulated using a PNS code; however, the experimentally observed degree of spreading rate asymmetry could not be fully predicted with the k−ε turbulence model, even when a recently proposed compressibility correction was applied.

Effects of Density and Blowing Ratios on the Turbulent Structure and Effectiveness of Film Cooling

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Zachary T. Stratton ◽  
Tom I-P. Shih
Keyword(s):  
Shear Layer ◽  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Turbulent Structure ◽  
Reverse Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Turbulent Fluctuations

Large eddy simulations (LES) were performed to investigate film cooling of a flat plate, where the cooling jets issued from a plenum through one row of circular holes of diameter D and length 4.7D that are inclined at 35 deg relative to the plate. The focus is on understanding the turbulent structure of the film-cooling jet and the film-cooling effectiveness. Parameters studied include blowing ratio (BR = 0.5 and 1.0) and density ratio (DR = 1.1 and 1.6). Also, two different boundary layers (BL) upstream of the film-cooling hole were investigated—one in which a laminar BL was tripped to become turbulent from near the leading edge of the flat plate, and another in which a mean turbulent BL is prescribed directly. The wall-resolved LES solutions generated were validated by comparing its time-averaged values with data from PIV and thermal measurements. Results obtained show that having an upstream BL that does not have turbulent fluctuations enhances the cooling effectiveness significantly at low velocity ratios (VR) when compared to an upstream BL that resolved the turbulent fluctuations. However, these differences diminish at higher VRs. Instantaneous flow reveals a bifurcation in the jet vorticity as it exits the hole at low VRs, one branch forming the shear-layer vortex, while the other forms the counter-rotating vortex pair (CRVP). At higher VRs, the shear layer vorticity is found to reverse direction, changing the nature of the turbulence and the heat transfer. Results obtained also show the strength and structure of the turbulence in the film-cooling jet to be strongly correlated to VR.

The expansion of a hypersonic turbulent boundary layer at a sharp corner

1975 ◽  
Vol 67 (4) ◽  
pp. 647-655 ◽  
Author(s):  
A. W. Bloy
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Wall Pressure ◽  
Pressure Measurements ◽  
Sharp Corner ◽  
Transfer Theory ◽  
Heat Transfer Theory ◽  
Surface Data ◽  
Pitot Pressure

A sharp wedge expansion flap was tested in the von Kámán Institute Long-shot tunnel at Mach 16 and data on the wall pressure and heat transfer were obtained. Pitot pressure measurements in the boundary layer just ahead of the expansion flap were also made. The surface data are compared with predictions from a characteristics solution for the boundary-layer expansion and from a simple heat-transfer theory.

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