Effect of aft wall slope on cavity pressure oscillations in supersonic flows

2009 ◽  
Vol 113 (1143) ◽  
pp. 291-300 ◽  
Author(s):  
N. S. Vikramaditya ◽  
J. Kurian
Keyword(s):  
Experimental Study ◽  
Data Analysis ◽  
Acoustic Wave ◽  
Mode Switching ◽  
Pressure Measurements ◽  
Cavity Pressure ◽  
Pressure Oscillations ◽  
Stable Mode ◽  
Unsteady Pressure Measurements ◽  
Wall Slope

Abstract An experimental study of supersonic flow over wall mounted cavities with different aft wall angles is carried out. Unsteady pressure measurements were made on the walls and floor of the cavity. Data analysis was performed on the experimental results using statistical methods. In the case of higher angled cavities, the presence of an upstream traveling acoustic wave could be confirmed. For lower angled cavities (60 degrees and less) where the acoustic wave could not be identified, the flow inside the cavity was more or less stable. Mode switching occurring in higher angled cavities was confirmed by spectrogram studies.

Windmilling Characteristics of a Contra-Rotating Fan

2020 ◽  
Author(s):  
Manas MP ◽  
Arghya Karmakar ◽  
Pradeep A M
Keyword(s):  
Experimental Study ◽  
Total Pressure ◽  
Flow Coefficient ◽  
Pressure Measurements ◽  
Axial Fan ◽  
Stall Inception ◽  
Pressure Drops ◽  
Low Aspect Ratio ◽  
Flow Development ◽  
Unsteady Pressure Measurements

Abstract In the present experimental study, a low aspect ratio, low hub-tip ratio contra-rotating axial fan is investigated to understand its performance under windmilling conditions. Two configurations are tested; in the first configuration (event A), the front rotor of the contra-rotating fan is powered and the rear rotor is allowed to windmill; in the second configuration (event B), the rear rotor of the contra-rotating fan is powered and the front rotor is allowed to windmill. The spanwise distribution of the loading coefficient and the flow angles at different streamwise positions reveal the details of the flow development across the rotors. Though the average total pressure drops across the windmilling rotor for both the events, a small spanwise region behaves as a fan or a stirrer. Thus, a "neutral radius" on the windmilling rotor is identified for both events A and B. The neutral radius appears close to the tip for event A and it appears close to the hub for event B and the neutral radius shifts its position to a lower span location as the flow coefficient reduces. On the windmilling rotor, the span regions close to the tip for event A behaves as a fan and the span regions close to the hub for event B behaves as a stirrer. Further, the unsteady pressure measurements recorded at the casing captures the fundamental phenomena during the stall inception. The paper thus relates the similarities and unveils the contrasting features of the windmilling events A and B.

scholarly journals Solid-driven mechanism and experimental study based on surface acoustic wave microfluidic

AIP Advances ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 125116
Author(s):  
Tinghua Li ◽  
Qingyun Huang ◽  
Shoubo Li ◽  
Yijuan Xie ◽  
Junlong Han ◽  
...  
Keyword(s):  
Experimental Study ◽  
Acoustic Wave ◽  
Surface Acoustic Wave

scholarly journals Experimental Study on Dynamic Combustion Characteristics in Swirl-Stabilized Combustors

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1609
Author(s):  
Donghyun Hwang ◽  
Kyubok Ahn
Keyword(s):  
Experimental Study ◽  
Heat Release ◽  
Dynamic Pressure ◽  
Combustion Instability ◽  
Flame Structure ◽  
Pressure Sensors ◽  
Necessary Condition ◽  
Rayleigh Criterion ◽  
Pressure Oscillations ◽  
Geometric Conditions

An experimental study was performed to investigate the combustion instability characteristics of swirl-stabilized combustors. A premixed gas composed of ethylene and air was burned under various flow and geometric conditions. Experiments were conducted by changing the inlet mean velocity, equivalence ratio, swirler vane angle, and combustor length. Two dynamic pressure sensors, a hot-wire anemometer, and a photomultiplier tube were installed to detect the pressure oscillations, velocity perturbations, and heat release fluctuations in the inlet and combustion chambers, respectively. An ICCD camera was used to capture the time-averaged flame structure. The objective was to understand the relationship between combustion instability and the Rayleigh criterion/the flame structure. When combustion instability occurred, the pressure oscillations were in-phase with the heat release oscillations. Even if the Rayleigh criterion between the pressure and heat release oscillations was satisfied, stable combustion with low pressure fluctuations was possible. This was explained by analyzing the dynamic flow and combustion data. The root-mean-square value of the heat release fluctuations was observed to predict the combustion instability region better than that of the inlet velocity fluctuations. The bifurcation of the flame structure was a necessary condition for combustion instability in this combustor. The results shed new insight into combustion instability in swirl-stabilized combustors.

Effect of back pressure and freestream dynamic pressure on a typical Ramjet engine duct under realistic supersonic inlet condition

2017 ◽  
Vol 122 (1247) ◽  
pp. 83-103 ◽  
Author(s):  
R. Saravanan ◽  
S.L.N. Desikan ◽  
T.M. Muruganandam
Keyword(s):  
Dynamic Pressure ◽  
Back Pressure ◽  
Flow Visualisation ◽  
Pressure Measurements ◽  
Shock Train ◽  
Unsteady Pressure ◽  
Expansion Waves ◽  
Ramjet Engine ◽  
Flap Deflection ◽  
Unsteady Pressure Measurements

ABSTRACTThe present study investigates the behaviour of the shock train in a typical Ramjet engine under the influence of shock and expansion waves at the entry of a low aspect ratio (1:0.75) rectangular duct/isolator at supersonic Mach number (M = 1.7). The start/unstart characteristics are investigated through steady/unsteady pressure measurements under different back and dynamic pressures while the shock train dynamics are captured through instantaneous Schlieren flow visualisation. Two parameters, namely pressure recovery and the pressure gradient, is derived to assess the duct/isolator performance. For a given back pressure, with maximum blockage (9% above nominal), the duct/isolator flow is established when the dynamic pressure is increased by 23.5%. The unsteady pressure measurements indicate different scales of eddies above 80 Hz (with and without flap deflection). Under the no flap deflection (no back pressure) condition, the maximum fluctuating pressure component is 0.01% and 0.1% of the stagnation pressure at X/L = 0.03 (close to the entry of the duct) and X/L = 0.53 (middle of the duct), respectively. Once the flap is deflected (δ = 8°), decay in eddies by one order is noticed. Further increase in back pressure (δ ≥ 11°) leads the flow to unstart where eddies are observed to be disappeared.

Unsteady Pressure Measurements in a Heated Rotating Cavity

2021 ◽  
Author(s):  
Richard W. Jackson ◽  
Hui Tang ◽  
James A. Scobie ◽  
Oliver J. Pountney ◽  
Carl M. Sangan ◽  
...  
Keyword(s):  
Vortex Pair ◽  
Practical Significance ◽  
Pressure Measurements ◽  
Rotating Disc ◽  
Frequency Spectra ◽  
Paper Properties ◽  
Unsteady Pressure ◽  
Rotating Cavity ◽  
Buoyancy Forces ◽  
Unsteady Pressure Measurements

Abstract The flow in the heated rotating cavity of an aero-engine compressor is driven by buoyancy forces, which result in pairs of cyclonic and anticyclonic vortices. The resultant cavity flow field is three-dimensional, unsteady and unstable, which makes it challenging to model the flow and heat transfer. In this paper, properties of the vortex structures are determined from novel unsteady pressure measurements collected on the rotating disc surface over a range of engine-representative parameters. These measurements are the first of their kind with practical significance to the engine designer and for validation of computational fluid dynamics. One cyclonic/anticyclonic vortex pair was detected over the experimental range, despite the measurement of harmonic modes in the frequency spectra at low Rossby numbers. It is shown that these modes were caused by unequal size vortices, with the cyclonic vortex the larger of the pair. The structures slipped relative to the discs at a speed typically around 10% to 15% of that of the rotor, but the speed of precession was often unsteady. The coherency, strength and slip of the vortex pair increased with the buoyancy parameter, due to the stronger buoyancy forces, but they were largely independent of the rotational Reynolds number.

scholarly journals Detailed Pressure Measurements During the Transition to Rotating Stall in an Axial Compressor: Influence of the Throttling Process

2018 ◽  
Author(s):  
Gabriel Margalida ◽  
Antoine Dazin ◽  
Pierric Joseph ◽  
Olivier Roussette
Keyword(s):  
Axial Compressor ◽  
Warning Signal ◽  
Rotating Stall ◽  
Pressure Measurements ◽  
Pressure Signal ◽  
Instability Development ◽  
Stable Operating ◽  
Instantaneous Pressure ◽  
Reference Pressure ◽  
Unsteady Pressure Measurements

This paper presents experimental unsteady pressure measurements gathered on a single stage axial compressor during pre-stall and transition to stall operations. The aim of this study is to analyze the transition from a stable operating point to the fully developed rotating stall regime, and more specifically, the effect of the throttling process on the development of the instabilities. To do so, experiments have been repeated leading the compressor to stall operations with various throttling speed. On one hand, this paper analyses the effect of the throttling speed on the dynamic of the instability development from the first detection of spike type precursors to completely developed rotating stall. On the other hand, a stall warning signal based on the correlation of the instantaneous pressure signal with a reference pressure signal is built. The influence of the location of the pressure transducer used for the warning signal is first analyzed. Then an analysis of the effect of the throttling process on the time between the warning signal and the effective stall development is proposed.

scholarly journals The Effect Of Rajalele Probiotic On Survival Rate Of Fish Juvenile Pangasius pangasius, Oreochromis niloticus, Cyprinus carpio

2020 ◽  
Vol 6 (1) ◽  
pp. 88-95
Author(s):  
Marlina Doloksaribu ◽  
Robert Martua Simanjuntak ◽  
Ied Hidayani Parinduri
Keyword(s):  
Social Sciences ◽  
Experimental Study ◽  
Data Analysis ◽  
Survival Rate ◽  
Cyprinus Carpio ◽  
Oreochromis Niloticus ◽  
Fish Farming ◽  
Randomized Design ◽  
The Social ◽  
Completely Randomized Design

The use of probiotics is certainly one of the solutions in overcoming the problem of increasing seed in fish farming. One of them is the use of probiotic king catfish, in this study tested on catfish, tilapia and goldfish. This research is an experimental study. The design used in this study was a Completely Randomized Design with 4 treatments 3 replications. Data analysis used Statistical Package for the Social Sciences version 15. The results of the analysis of the highest seed survival rate were obtained on Pangasius pangasius (95%), on Oreochromis niloticus (83,33 %), and Cyprinus carpio (80%). The treatment of Rajalele probiotics has a very significant effect (very significant) Fanalysis (23.01) > Ftable 0.01 (7.59) on the graduation of Pangasius pangasius, Oreochromis niloticus, and Cyprinus carpio. The conclusion of this study shows that the survival rate the highest in Pangasius pangasius

scholarly journals PENGARUH LATIHAN SMASH TANPA BOLA DAN LATIHAN SMASH BOLA DIAM TERHADAP KEMAMPUAN SMASH BOLAVOLI

2020 ◽  
Vol 11 (2) ◽  
pp. 72
Author(s):  
Resa Sukardi Massa ◽  
Suprianto Kadir
Keyword(s):  
Experimental Study ◽  
Data Analysis ◽  
Research Groups ◽  
Study Program ◽  
Coaching Education ◽  
Significant Difference ◽  
Education Study ◽  
The Difference ◽  
Sports Coaching ◽  
Paired T Test

This research is a field experimental study that aims to find out the difference between the effects of non-ball smash exercises and silent ball smash exercises on the ability of volleyball smash on students of the FOK UNG Sports Coaching Education Study Program. The population and sample involved in this study were 60 students of the FOK UNG Sports Coaching Education Study Program. However, in accordance with the research design, two research groups were formed which consisted of ball-free smash exercises and silent ball smash exercises. The research was carried out for six weeks with frequency of exercise 3 times a week. Based on the results of data analysis using the paired t-test formula and the unpaired ttest at a significant level of 95%, it can be concluded as follows: There is a significant effect of smash training without the ball on the ability to do volleyball smash (to = 8,869> tt = 2,045 ). There is a significant effect of the silent ball smash exercise on the ability to do volleyball smash (to = 13,535> tt = 2,045). There is a significant difference in the effect between the smash ball practice without the ball and the silent ball smash exercise on the ability to do volleyball smash (to = 8,259> tt = 2,000)

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