scholarly journals Global Visualization of Compressible Swept Convex-Corner Flow Using Pressure-Sensitive Paint

Aerospace ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 106
Author(s):  
Kung-Ming Chung ◽  
Yi-Xuan Huang
Keyword(s):  
Boundary Layer Separation ◽  
Temperature Correction ◽  
Test Case ◽  
Separation Region ◽  
Pressure Sensitive Paint ◽  
Pressure Transducers ◽  
Convex Corner ◽  
Pressure Distributions ◽  
Pressure Sensitive ◽  
Corner Flow

This study used pressure-sensitive paint (PSP) and determined the surface pressure distributions for a compressible swept convex-corner flow. The freestream Mach numbers were 0.64 and 0.83. The convex-corner angle and swept angle were, respectively, 10–17° and 5–15°. Expansion and compression near the corner apex were clearly visualized. For the test case of shock-induced boundary layer separation, there were greater spanwise pressure gradient and curved shocks. The acquired PSP data agree with the experimental data measured using the Kulite pressure transducers for a subsonic expansion flow. For a transonic expansion flow, the discrepancy was significant. The assumption of a constant recovery factor is not valid in the separation region, and temperature correction for PSP measurements is required.

scholarly journals Micro-Vortex Generators on Transonic Convex-Corner Flow

Aerospace ◽  
2021 ◽  
Vol 8 (9) ◽  
pp. 268
Author(s):  
Kung-Ming Chung ◽  
Kao-Chun Su ◽  
Keh-Chin Chang
Keyword(s):  
Boundary Layer ◽  
Pressure Fluctuations ◽  
Boundary Layer Separation ◽  
Vortex Generators ◽  
Convex Corner ◽  
Pressure Distributions ◽  
Corner Flow ◽  
Favorable Pressure Gradient ◽  
Oil Flow ◽  
Shock Oscillation

A convex corner models the upper surface of a deflected flap and shock-induced boundary layer separation occurs at transonic speeds. This study uses micro-vortex generators (MVGs) for flow control. An array of MVGs (counter-rotating vane type, ramp type and co-rotating vane type) with a height of 20% of the thickness of the incoming boundary layer is installed upstream of a convex corner. The surface pressure distributions are similar regardless of the presence of MVGs. They show mild upstream expansion, a strong favorable pressure gradient near the corner’s apex and downstream compression. A corrugated surface oil flow pattern is observed in the presence of MVGs and there is an onset of compression moving downstream. The counter-rotating vane type MVGs produce a greater reduction in peak pressure fluctuations and the ramp type decreases the separation length. The presence of MVGs stabilizes the shock and shock oscillation is damped.

Unsteady Pressure Measurement on Oscillating Blade in Transonic Flow Using Fast-Response Pressure-Sensitive Paint

2017 ◽  
Author(s):  
Toshinori Watanabe ◽  
Toshihiko Azuma ◽  
Seiji Uzawa ◽  
Takehiro Himeno ◽  
Chihiro Inoue
Keyword(s):  
Surface Pressure ◽  
Transonic Flow ◽  
Aerodynamic Force ◽  
Fast Response ◽  
Pressure Sensitive Paint ◽  
Unsteady Pressure ◽  
Pressure Distributions ◽  
Pressure Sensitive ◽  
Unsteady Surface Pressure ◽  
Response Pressure

A fast-response pressure-sensitive paint (PSP) technique was applied to the measurement of unsteady surface pressure of an oscillating cascade blade in a transonic flow. A linear cascade was used, and its central blade was oscillated in a translational manner. The unsteady pressure distributions of the oscillating blade and two stationary neighbors were measured using the fast-response PSP technique, and the unsteady aerodynamic force on the blade was obtained by integrating the data obtained on the pressures. The measurements made with the PSP technique were compared with those obtained by conventional methods for the purpose of validation. From the results, the PSP technique was revealed to be capable of measuring the unsteady surface pressure, which is used for flutter analysis in transonic conditions.

ON HIGH-RESOLUTION PRESSURE AMPLITUDE AND PHASE MEASUREMENTS COMPARING FAST-RESPONSE PRESSURE TRANSDUCERS AND UNSTEADY PRESSURE-SENSITIVE PAINT

2021 ◽  
pp. 1-13
Author(s):  
Martin Bitter ◽  
Stephan Stotz ◽  
Reinhard Niehuis
Keyword(s):  
Second Harmonic ◽  
Measurement Techniques ◽  
Pressure Amplitude ◽  
Pressure Sensitive Paint ◽  
Simultaneous Application ◽  
Pressure Transducers ◽  
Unsteady Pressure ◽  
Flow Sensing ◽  
Pressure Sensitive ◽  
Perturbation Frequency

Abstract This paper presents the simultaneous application of fastresponse pressure transducers and unsteady pressure-sensitive paint (unsteady PSP) for the precise determination of pressure amplitudes and phases up to 3,000 Hz. These experiments have been carried out on a low-pressure turbine blade cascade under engine-relevant conditions (Re, Ma, Tu) in the High-Speed Cascade Wind Tunnel. Periodic blade/vane interactions were simulated at the inlet to the cascade using a wake generator operating at a constant perturbation frequency of 500 Hz. The main goal of this paper is the detailed comparison of amplitude and phase distributions between both flow sensing techniques at least up to the second harmonic of the wake generator's fundamental perturbation frequency (i.e. 1,000 Hz). Therefore, a careful assessment of the key drivers for relative deviations between measurement results as well as a detailed discussion of the data processing is presented for both measurement techniques. This discussion outlines the mandatory steps which were essential to achieve the quality as presented down to pressure amplitudes of several pascal even under challenging experimental conditions. Apart from the remarkable consistency of the results, this paper reveals the potential of (unsteady) PSP as a future key flow sensing technique in turbomachinery research, especially for cascade testing. The results demonstrate that PSP was able to successfully sense pressure dynamics with very low fluctuation amplitudes down to 8 Pa.

scholarly journals Development of a Pressure-Sensitive Coating Using Platinum Octaethylporphyrin

Coatings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1093
Author(s):  
George Catalin Cristea ◽  
Sorina Ilina ◽  
George Pelin ◽  
Adriana Stefan ◽  
Cristina Elisabeta Pelin
Keyword(s):  
High Resolution ◽  
Surface Pressure ◽  
Measurement Technique ◽  
New Method ◽  
Optical Technique ◽  
Pressure Sensitive Paint ◽  
Image Capture ◽  
Pressure Distributions ◽  
Pressure Sensitive ◽  
Sensitive Coating

In recent years, researchers have developed a new method of measuring the pressure on the surface using sensitive paints. This is an optical technique for determining surface pressure distributions by measuring changes in the intensity, emitted by certain excited molecules. The main advantage of the method over traditional techniques is the high resolution of the information. The only limitation of the resolution of a global map generated by the PSP (pressure-sensitive paint) technique is given by the capabilities of the image capture device. This paper describes the development of a technology for obtaining pressure-sensitive paint, in laboratory conditions, as an advanced measurement technique. The method has an application in many fields such as automotive, aerospace, or even medical.

On High-Resolution Pressure Amplitude and Phase Measurements Comparing Fast-Response Pressure Transducers and Unsteady Pressure-Sensitive Paint

2020 ◽  
Author(s):  
Martin Bitter ◽  
Stephan Stotz ◽  
Reinhard Niehuis
Keyword(s):  
Fast Response ◽  
Pressure Amplitude ◽  
Pressure Sensitive Paint ◽  
Simultaneous Application ◽  
Pressure Transducers ◽  
Unsteady Pressure ◽  
Flow Sensing ◽  
Pressure Sensitive ◽  
Perturbation Frequency ◽  
Response Pressure

Abstract This paper presents the simultaneous application of fast-response pressure transducers and unsteady pressure-sensitive paint (unsteady PSP) for the precise determination of pressure amplitudes and phases up to 3,000 Hz. These experiments have been carried out on a low-pressure turbine blade cascade under engine-relevant conditions (Re, Ma, Tu) in the High-Speed Cascade Wind Tunnel. Periodic blade/vane interactions were simulated at the inlet to the cascade using a wake generator operating at a constant perturbation frequency of 500 Hz. The main goal of this paper is the detailed comparison of amplitude and phase distributions between both flow sensing techniques at least up to the second harmonic of the wake generator’s fundamental perturbation frequency (i.e. 1,000 Hz). Therefore, a careful assessment of the key drivers for relative deviations between measurement results as well as a detailed discussion of the data processing is presented for both measurement techniques. This discussion outlines the mandatory steps which were essential to achieve the quality as presented down to pressure amplitudes of several pascal even under challenging experimental conditions. Apart from the remarkable consistency of the results, this paper reveals the potential of (unsteady) PSP as a future key flow sensing technique in turbomachinery research, especially for cascade testing. The results demonstrate that PSP was able to successfully sense pressure dynamics with very low fluctuation amplitudes down to 8 Pa.

scholarly journals The Effect of Vortex Generators on Shock-Induced Boundary Layer Separation in a Transonic Convex-Corner Flow

Aerospace ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 157
Author(s):  
Kung-Ming Chung ◽  
Kao-Chun Su ◽  
Keh-Chin Chang
Keyword(s):  
Boundary Layer ◽  
Surface Pressure ◽  
Boundary Layer Separation ◽  
Vortex Generators ◽  
Streamwise Vorticity ◽  
Layer Separation ◽  
Convex Corner ◽  
Corner Flow ◽  
The Mean ◽  
Control Surfaces

Deflected control surfaces can be used as variable camber control in different flight conditions, and a convex corner resembles a simplified configuration for the upper surface. This experimental study determines the presence of passive vortex generators, VGs (counter-rotating vane type), on shock-induced boundary layer separation for transonic convex-corner flow. The mean surface pressure distributions in the presence of VGs for h/δ = 0.2 and 0.5 are similar to those for no flow control. If h/δ = 1.0 and 1.5, there is an increase in the amplitude of the mean surface pressure upstream of the corner’s apex, which corresponds to greater device drag and less downstream expansion. There is a decrease in peak pressure fluctuations as the value of h/δ increases, because there is a decrease in separation length and the frequency of shock oscillation. The effectiveness of VGs also depends on the freestream Mach number. For M = 0.89, there is an extension in the low-pressure region downstream of a convex corner, because there is greater convection and induced streamwise vorticity. VGs with h/δ ≤ 0.5 are preferred if deflected control surfaces are used to produce lift.

scholarly journals Dynamic-stall measurements using time-resolved pressure-sensitive paint on double-swept rotor blades

2021 ◽  
Vol 63 (1) ◽  
Author(s):  
Armin Weiss ◽  
Reinhard Geisler ◽  
Martin M. Müller ◽  
Christian Klein ◽  
Ulrich Henne ◽  
...  
Keyword(s):  
Measurement System ◽  
Transient Flow ◽  
Fast Response ◽  
Rotor Blades ◽  
Dynamic Stall ◽  
Test Facility ◽  
Pressure Sensitive Paint ◽  
Detached Eddy Simulation ◽  
Pressure Transducers ◽  
Pressure Sensitive

Abstract The study presents an optimized pressure-sensitive paint (PSP) measurement system that was applied to investigate unsteady surface pressures on recently developed double-swept rotor blades in the rotor test facility at the German Aerospace Center (DLR) in Göttingen. The measurement system featured an improved version of a double-shutter camera that was designed to reduce image blur in PSP measurements on fast rotating blades. It also comprised DLR’s PSP sensor, developed to capture transient flow phenomena (iPSP). Unsteady surface pressures were acquired across the outer 65% of the rotor blade with iPSP and at several radial blade sections by fast-response pressure transducers at blade-tip Mach and Reynolds numbers of $$\mathrm {M}_\mathrm{tip} = 0.282-0.285$$ M tip = 0.282 - 0.285 and $$\mathrm {Re}_\mathrm{tip}= 5.84-5.95 \times 10^5$$ Re tip = 5.84 - 5.95 × 10 5 . The unique experimental setup allowed for scanning surface pressures across the entire pitch cycle at a phase resolution of $${0.225}\,{\mathrm{deg}}$$ 0.225 deg azimuth for different collective and cyclic-pitch settings. Experimental results of both investigated cyclic-pitch settings are compared in detail to a delayed detached eddy simulation using the flow solver FLOWer and to flow visualizations from unsteady Reynolds-averaged Navier–Stokes (URANS) computations with DLR’s TAU code. The findings reveal a detailed and yet unseen insight into the pressure footprint of double-swept rotor blades undergoing dynamic stall and allow for deducing “stall maps”, where confined areas of stalled flow on the blade are identifiable as a function of the pitch phase. Graphical abstract

Unsteady Pressure Measurement on Oscillating Blade in Transonic Flow Using Fast-Response Pressure-Sensitive Paint

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Toshinori Watanabe ◽  
Toshihiko Azuma ◽  
Seiji Uzawa ◽  
Takehiro Himeno ◽  
Chihiro Inoue
Keyword(s):  
Surface Pressure ◽  
Transonic Flow ◽  
Aerodynamic Force ◽  
Fast Response ◽  
Pressure Sensitive Paint ◽  
Unsteady Pressure ◽  
Pressure Distributions ◽  
Pressure Sensitive ◽  
Unsteady Surface Pressure ◽  
Response Pressure

A fast-response pressure-sensitive paint (PSP) technique was applied to the measurement of unsteady surface pressure of an oscillating cascade blade in a transonic flow. A linear cascade was used, and its central blade was oscillated in a translational manner. The unsteady pressure distributions of the oscillating blade and two stationary neighbors were measured using the fast-response PSP technique, and the unsteady aerodynamic force on the blade was obtained by integrating the data obtained on the pressures. The measurements made with the PSP technique were compared with those obtained by conventional methods for the purpose of validation. From the results, the PSP technique was revealed to be capable of measuring the unsteady surface pressure, which is used for flutter analysis in transonic conditions.

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