scholarly journals The Effect of Yaw Angle on a Compressible Rectangular Cavity Flow

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Kuan-Huang Lee ◽  
Kung-Ming Chung ◽  
Keh-Chin Chang
Keyword(s):  
Pressure Fluctuations ◽  
Open Cavity ◽  
Width Ratio ◽  
Lower Mode ◽  
Fluctuating Pressure ◽  
Sustained Oscillations ◽  
Power Spectral ◽  
The Mean ◽  
Mach Numbers ◽  
Yaw Angle

Experiments are performed to determine the characteristics of a compressible flow over yawed rectangular cavities for Mach numbers of 0.64, 0.70, and 0.83. The cavity’s length-to-depth ratio varies from 4.43 to 21.50 and the length-to-width ratio is unity. The yaw angle is 0°–45°. The upstream compression and downstream expansion near the front and rear corners of a cavity decrease when the value of the yaw angle increases. The amplitude of the fluctuating pressure is a maximum for an open cavity with a yaw angle of 15°. An increase in the yaw angle results in a reduction in the pressure fluctuations for both open and transitional cavities. In the span-wise direction, variations in the mean and fluctuating pressure are less significant than those in the chord-wise direction. The oscillating frequency of resonance varies slightly with the yaw angle, but the amplitudes for the power spectral density are significantly reduced when the yaw angle is larger than 30°. For lower Mach numbers, the lower mode plays an important role in self-sustained oscillations for an open cavity when there is an increase in the yaw angle.

Aerodynamic Forces on Multiple Unit Trains in Cross Winds

2009 ◽  
Vol 131 (10) ◽  
Author(s):  
Christopher J. Baker ◽  
Mark Sterling
Keyword(s):  
Pressure Fluctuations ◽  
Decomposition Analysis ◽  
Aerodynamic Characteristics ◽  
Scale Model ◽  
Fluctuating Pressure ◽  
Time Histories ◽  
Multiple Unit ◽  
The Mean ◽  
Proper Orthogonal ◽  
Natural Wind

This paper describes the results of wind tunnel tests that were carried out to measure the aerodynamic characteristics of an electrical multiple unit (EMU) vehicle in a cross wind. The measurements were made on a 1/30 scale model of the Class 365 EMU in a simulation of the natural wind. The time histories of surface pressures were measured at a large number of points over the vehicle from which the aerodynamic characteristics and force coefficients were determined. This paper describes the complex fluctuating pressure field over the vehicle, through a consideration of the mean and fluctuating pressure coefficients and their spectra, and through a proper orthogonal decomposition analysis, which identifies the major modes of this distribution. The mean, fluctuating, and extreme aerodynamic side and lift forces are also discussed. It is shown that the flow pattern around the vehicle is dominated by large windward roof corner pressure fluctuations.

Numerical and Experimental Studies of Pipe Vibration Generated by Elongated Orifice

2016 ◽  
Author(s):  
Wenjie Bai ◽  
Quan Duan ◽  
Zaoxiao Zhang
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Flow Rate ◽  
Vibration Response ◽  
Frequency Range ◽  
Fluctuating Pressure ◽  
Outlet Pressure ◽  
Wall Pressure Fluctuations ◽  
Power Spectral ◽  
Pipe Vibration

Hydraulic tests for elongated orifice-induced wall pressure fluctuations and vibration in pipeline have been carried out. The regulating modes of test system consist of maintaining outlet pressure to increase flow rate and maintaining flow rate to decrease outlet pressure. Both regulating modes would increase the possibility of cavitation within elongated orifice, which has been confirmed by numerical simulation in present study. Statistical characteristics of the fluctuating pressure and structure vibration response have been studied. The standard deviation analyses indicate that the amplitude of fluctuating pressure is mainly determined by flow rate. The power spectral density analyses show that the energy of the fluctuating pressure behind elongated orifice is concentrated in lower frequency range and it can be divided into two parts in this test: the pressure pulsation excited by plunger pump and the random fluctuating pressure produced by elongated orifice’s disturbance. The power spectral density of pipe vibration response shows that the lower frequency of pipe vibration response can be ascribed to the fluctuating pressure behind elongated orifice and the characteristic frequencies corresponding to cavitation within elongated orifice are in the higher frequency range.

Microbiology of cerumen in patients with recurrent otitis externa and cases with open mastoidectomy cavities

2004 ◽  
Vol 118 (4) ◽  
pp. 260-262 ◽  
Author(s):  
Yavuz Selim Pata ◽  
Candan Öztürk ◽  
Yücel Akbaş ◽  
Murat Ünal ◽  
Kemal Görür ◽  
...  
Keyword(s):  
Staphylococcus Epidermidis ◽  
Otitis Externa ◽  
Chronic Otitis Media ◽  
Open Cavity ◽  
Microbial Flora ◽  
Microbial Count ◽  
Group A ◽  
The Common ◽  
The Mean ◽  
Group B

This study investigated the common flora of human cerumen in patients with recurrent otitis externa, and subjects who had been operated on and had an open mastoidectomy cavity from chronic otitis media.Cerumen samples were collected from three groups; group A (n = 20) consisted of patients with recurrent otitis externa, group B (n = 20) consisted of patients with an open cavity and group C (n = 30) consisted of healthy subjects.The mean of the microbial count was 3.4 × 104 in group A, 3.08 × 104 in group B and 2.48 × 104 in group C. The most commonly isolated microorganism from the three groups was Staphylococcus epidermidis. No growth was observed in five cases (25 per cent) in group A and in three cases (10 per cent) in group C. In groupB antimicrobial growth was observed in all samples. In 46 (65 per cent) of the cerumen samples,the isolates were monomicrobial and 24 (35 per cent) of the cerumen samples were polymicrobial. The isolates were polymicrobial in 65 per cent of group A, 20 per cent in group B and 23.3 per cent in group C.In the process of investigating the microbial flora of cerumen in all the three groups, microbial growth was observed from all the samples from patients with an open cavity, unlike the other groups, and it was determined that the group with recurrent external otitis had the most abundant microbial flora.

An Experimental Investigation of Flow-Induced Cavity Resonance

2001 ◽  
Author(s):  
Paul J. Zoccola ◽  
Theodore M. Farabee
Keyword(s):  
Experimental Investigation ◽  
Energy Production ◽  
Pressure Fluctuations ◽  
Cavity Resonance ◽  
Cavity Pressure ◽  
Novel Technique ◽  
Cavity Opening ◽  
The Mean ◽  
Marine Applications ◽  
Opening Phase

Abstract Excitation of cavity resonance by flow over an aperture is often a source of unwanted noise in aerospace, automotive, and marine applications. An experimental investigation of this phenomenon was conducted. Detailed measurements of the cavity pressure and the velocity field in the opening were performed in a quiet flow facility. Spectral data on cavity pressure fluctuations obtained for a variety of configurations were analyzed over a range of speeds to determine the behavior of both sheartones and cavity tones during non-resonant and resonant conditions. The mean and fluctuating velocity profiles as well as the cross-spectral properties between the velocity components and cavity pressure were also obtained within the cavity opening. Phase between the velocity components and the pressure was used to calculate the streamwise convection velocities across the opening. A novel technique used to measure vorticity allowed calculation of the measured energy production in the opening. The data support the finding that the resonant and non-resonant conditions are distinguished by the behavior of the convection velocity and by the distribution of energy production in the flow field.

On the Combined Effect of Mean Flow and Acoustic Excitation on Structural Response and Radiation

1997 ◽  
Vol 119 (3) ◽  
pp. 448-456 ◽  
Author(s):  
A. Frendi ◽  
L. Maestrello
Keyword(s):  
Mach Number ◽  
Response Spectrum ◽  
Structural Response ◽  
Harmonic Excitation ◽  
Two Dimensions ◽  
Physical Problem ◽  
Acoustic Excitation ◽  
Mean Flow ◽  
Power Spectral ◽  
The Mean

Numerical experiments in two dimensions are carried out in order to investigate the response of a typical aircraft structure to a mean flow and an acoustic excitation. Two physical problems are considered; one in which the acoustic excitation is applied on one side of the flexible structure and the mean flow is on the other side while in the second problem both the mean flow and acoustic excitation are on the same side. Subsonic and supersonic mean flows are considered together with a random and harmonic acoustic excitation. In the first physical problem and using a random acoustic excitation, the results show that at low excitation levels the response is unaffected by the mean flow Mach number. However, at high excitation levels the structural response is significantly reduced by increasing the Mach number. In particular, both the shift in the frequency response spectrum and the broadening of the peaks are reduced. In the second physical problem, the results show that the response spectrum is dominated by the lower modes (1 and 3) for the subsonic mean flow case and by the higher modes (5 and 7) in the supersonic case. When a harmonic excitation is used, it is found that in the subsonic case the power spectral density of the structural response shows a subharmonic (f/4) while in the supersonic case no subharmonic is obtained.

Identification of the State of a Magneto-Fluidized Bed by Pressure Fluctuations

2006 ◽  
Vol 4 (1) ◽  
Author(s):  
Sachin Dahikar ◽  
Ram Sonolikar
Keyword(s):  
Fluidized Bed ◽  
Autocorrelation Function ◽  
Pressure Fluctuations ◽  
Spectral Density Function ◽  
Functional Relationships ◽  
Power Spectral ◽  
Data Points ◽  
Instantaneous Pressure ◽  
Conventional Signal ◽  
Mutual Information Function

Local instantaneous pressure signals obtained through a magneto-fluidized bed have been analyzed using both classical and advanced signal analysis methods, which can deliver the necessary information about the presence of the bubbling and turbulent flow pattern. The conventional signal processing tool such as autocorrelation and cross correlation were used as preliminary tools to analyze the data. Evaluation of the dominant bubble frequency was completed using the autocorrelation function and power spectral density function. Mutual information function was used to identify the periodicity and the predictability of the local instantaneous pressure signals. Since it does not demand any particular functional relationships between the data points, it is a better method (compared to autocorrelation function) for measuring the predictability of nonlinear systems.

scholarly journals Toward Future Installations: Mutual Interactions of Short Intakes With Modern High Bypass Fans

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Nagabhushana Rao Vadlamani ◽  
Teng Cao ◽  
Rob Watson ◽  
Paul G. Tucker
Keyword(s):  
Pressure Fluctuations ◽  
Limiting Factors ◽  
Small Scale ◽  
Flow Distortion ◽  
Factors Affecting ◽  
Fan Performance ◽  
Shock Unsteadiness ◽  
Power Spectral ◽  
Order Of Magnitude ◽  
Underlying Mechanisms

In this paper, we investigate the coupled interaction between a new short intake design with a modern fan in a high-bypass ratio civil engine, specifically under the off-design condition of high incidence. The interaction is expected to be much more significant than that on a conventional intake. The performance of both the intake-alone and rotor-alone configurations are examined under isolation. Subsequently, a comprehensive understanding on the two-way interaction between intake and fan is presented. This includes the effect of fan on intake angles of attack (AoA) tolerance (FoI) and the effect of circumferential and radial flow distortion induced by the intake on the fan performance (IoF). In the FoI scenario, the rotor effectively redistributes the mass flow at the fan-face. The AoA tolerance of the short-intake design has increased by ≈4 deg when compared with the intake-alone configuration. Dynamic nature of distortion due to shock unsteadiness has been quantified. ST plots and power spectral density (PSD) of pressure fluctuations show the existence of a spectral gap between the shock unsteadiness and blade passing, with almost an order of magnitude difference in the corresponding frequencies. In the IoF scenario, both the “large” (O(360 deg)) and “small” scale distortion (O(10–60 deg)) induced by the intake results in a non-uniform inflow to the rotor. Sector analysis reveals a substantial variation in the local operating condition of the fan as opposed to its steady characteristic. Streamline curvature, upwash, and wake thickening are identified to be the three key factors affecting the fan performance. These underlying mechanisms are discussed in detail to provide further insights into the physical understanding of the fan-intake interaction. In addition to the shock-induced separation on the intake lip, the current study shows that shorter intakes are much more prone to the upwash effect at higher AoA. Insufficient flow straightening along the engine axis is reconfirmed to be one of the limiting factors for the short-intake design.

Pressure and velocity measurements of an incompressible moderate Reynolds number jet interacting with a tangential flat plate

2015 ◽  
Vol 770 ◽  
pp. 247-272 ◽  
Author(s):  
A. Di Marco ◽  
M. Mancinelli ◽  
R. Camussi
Keyword(s):  
Reynolds Number ◽  
Flat Plate ◽  
Scaling Laws ◽  
Pressure Fluctuations ◽  
Wall Pressure ◽  
Theoretical Modelling ◽  
Wall Pressure Fluctuations ◽  
Moderate Reynolds Number ◽  
The Mean ◽  
Pressure And Velocity Measurements

The statistical properties of wall pressure fluctuations generated on a rigid flat plate by a tangential incompressible single stream jet are investigated experimentally. The study is carried out at moderate Reynolds number and for different distances between the nozzle axis and the flat plate. The overall aerodynamic behaviour is described through hot wire anemometer measurements, providing the effect of the plate on the mean and fluctuating velocity. The pressure field acting on the flat plate was measured by cavity-mounted microphones, providing point-wise pressure signals in the stream-wise and span-wise directions. Statistics of the wall pressure fluctuations are determined in terms of time-domain and Fourier-domain quantities and a parametric analysis is conducted in terms of the main geometrical length scales. Possible scaling laws of auto-spectra and coherence functions are presented and implications for theoretical modelling are discussed.

Spectral and Temporal Characteristics of Post-Stenotic Turbulent Wall Pressure Fluctuations

1979 ◽  
Vol 101 (2) ◽  
pp. 89-95 ◽  
Author(s):  
W. H. Pitts ◽  
C. F. Dewey
Keyword(s):  
Steady Flow ◽  
Pressure Fluctuations ◽  
Wall Pressure ◽  
Experimental Uncertainty ◽  
Flow Parameters ◽  
Wall Pressure Fluctuations ◽  
Power Spectral ◽  
Fluctuation Amplitude ◽  
Arterial Constriction ◽  
Turbulent Wall

The power spectral density of turbulent wall pressure fluctuations was measured in a tube downstream of a model arterial constriction. The flow parameters were varied from steady flow to conditions simulating human arterial pulsatile flow. Within the experimental uncertainty (±10 percent in characteristic turbulent frequency, fo, and ±25 percent in absolute rms pressure fluctuation amplitude), turbulent flow at the peak of systole produces wall pressure fluctuations identical to those of a steady flow at the same Reynolds number.

scholarly journals Numerical studies on aerodynamics of high-speed railway train subjected to strong crosswind

2019 ◽  
Vol 11 (11) ◽  
pp. 168781401988727
Author(s):  
Xu Wang ◽  
Yuanhao Qian ◽  
Zengshun Chen ◽  
Xiao Zhou ◽  
Huaqiang Li ◽  
...  
Keyword(s):  
Wind Speed ◽  
High Speed ◽  
Lift Coefficient ◽  
Aerodynamic Characteristics ◽  
Width Ratio ◽  
Force Coefficient ◽  
Rolling Moment ◽  
Side Force ◽  
Train Speed ◽  
Yaw Angle

Under the action of strong crosswind, the aerodynamic behavior of a rail vehicle at high speed will be changed significantly, which could directly affect the safe operation of the vehicle. With the help of the shape of train used in China, the aerodynamic characteristics of trains with scale of 1:1 is investigated using computational fluid dynamics numerical simulation method, which consists of the variation of aerodynamics force and moment with wind yaw angle, wind speed, train speed, and nose shape. After an initial validation against Baker’s results from wind tunnel test, the numerical model is then used to investigate the aerodynamic characteristics of the trains. The numerical results indicate that lift coefficient of the M train is slightly higher than TMC1 and TMC2 trains. Regardless of aerodynamics force coefficients, TMC1 reaches the maximum at a yaw angle of 75°. Aerodynamics force coefficient increases with both wind speed and train speed, but the change of which is not linear. Comparing aerodynamic force with different geometric dimensions of train nose, it is shown that height–width ratio is insensitive to side force and rolling moment, but sensitive to lift force from the yaw angle 0°–90°. The side force coefficient, as we most concern, is less than other results, when the length–width ratio is 1 and height–width is 0.87.

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