Measurements of Turbulence Generated by 60 Percent Solid Perforated Plates

1986 ◽  
Vol 108 (1) ◽  
pp. 55-63 ◽  
Author(s):  
M. D. Checkel
Keyword(s):  
Wind Tunnel ◽  
Perforated Plate ◽  
Spark Ignition Engine ◽  
Test Cell ◽  
Hot Wire ◽  
Mean Flow ◽  
Perforated Plates ◽  
Percent Solid ◽  
Decaying Turbulence ◽  
Good Agreement

Combustion experiments simulating spark-ignition engine conditions require generation and measurement of high intensity, rapidly decaying turbulence in a combustion test cell. Turbulence is generated by drawing various perforated plates across the test cell and is measured by hot-wire anemometry in the test cell and behind the same perforated plates in a steadily flowing wind tunnel. To correlate test cell and wind tunnel turbulence measurements, a simple statistical model of hot-wire anemometer response in turbulence with negligible mean flow is used. Good agreement between the two measurements tends to confirm the model for this case and demonstrates the value of perforated plate turbulence generators in producing controllable, measurable turbulence for confined combustion research.

Fluid Dynamic Aspects of Electrostatic Precipatators: Turbulence Characteristics in Scale Models

2003 ◽  
Vol 125 (4) ◽  
pp. 694-700 ◽  
Author(s):  
Aldo Coghe ◽  
Michele Mantegna ◽  
Giorgio Sotgia
Keyword(s):  
Fluid Dynamic ◽  
Perforated Plate ◽  
Hot Wire ◽  
Perforated Plates ◽  
Downstream Distance ◽  
Turbulence Decay ◽  
Scale Models ◽  
Electrostatic Precipitators ◽  
Semi Empirical ◽  
Good Agreement

The present work originated in an investigation on fluid dynamic aspects of electrostatic precipitators performed on scale models of an industrial apparatus. The experimental analysis of velocity and turbulence distribution, performed by hot-wire anemometry, confirmed that significant turbulence levels are found inside particle collectors. In fact, components used to spatially smooth the flow and lower its velocity peaks, such as hoods with wide divergence angles, turning vanes, and perforated plates, may also act as sources of turbulence and reduce the efficiency of electrostatic precipitators. These observations prompted a deeper analysis, both analytical and experimental, of the turbulence decay downstream perforated screens. A new simple semi-empirical model of turbulence decay is proposed, which has shown reasonably good agreement with experimental data, even at short downstream distance from the perforated plate, 50 to 250 hydraulic diameters.

scholarly journals On the Use of Hot-Wire Anemometers for Turbulence Measurements in Clouds

2007 ◽  
Vol 24 (6) ◽  
pp. 980-993 ◽  
Author(s):  
Holger Siebert ◽  
Katrin Lehmann ◽  
Raymond A. Shaw
Keyword(s):  
Wind Tunnel ◽  
Flow Velocity ◽  
Water Content ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Hot Wire ◽  
Mean Flow ◽  
Velocity Signal ◽  
Turbulence Measurements ◽  
Mean Flow Velocity

The use of a hot-wire anemometer for high-resolution turbulence measurements in a two-phase flow (e.g., atmospheric clouds) is discussed. Experiments in a small wind tunnel (diameter of 0.2 and 2 m in length) with a mean flow velocity in the range between 5 and 16 m s−1 are performed. In the wind tunnel a spray with a liquid water content of 0.5 and 2.5 g m−3 is generated. After applying a simple despiking algorithm, power spectral analysis shows the same results as spectra observed without spray under similar flow conditions. The flattening of the spectrum at higher frequencies due to impacting droplets could be reduced significantly. The time of the signal response of the hot wire to impacting droplets is theoretically estimated and compared with observations. Estimating the fraction of time during which the velocity signal is influenced by droplet spikes, it turns out that the product of liquid water content and mean flow velocity should be minimized. This implies that for turbulence measurements in atmospheric clouds, a slowly flying platform such as a balloon or helicopter is the appropriate instrumental carrier. Examples of hot-wire anemometer measurements with the helicopter-borne Airborne Cloud Turbulence Observation System (ACTOS) are presented.

Rapid Distortion of Homogeneous Turbulence Between Cylinders

2004 ◽  
Author(s):  
Babak Emami ◽  
Rui Liu ◽  
David S.-K. Ting ◽  
M. David Checkel
Keyword(s):  
Wind Tunnel ◽  
Turbulent Flow ◽  
Closed Loop ◽  
Perforated Plate ◽  
Energy Dissipation Rate ◽  
Hot Wire ◽  
Mean Velocity ◽  
Length Scales ◽  
Turbulence Decay ◽  
The Mean

The effects of ‘half-full-half’ cylinders on the distortion of a turbulent flow are experimentally investigated. A single hot-wire anemometry unit is used to measure the stream-wise parameters of the flow. The cylinders are 15.2 cm (6 in) in diameter and 76.2 cm (30 in) in height installed in a closed loop wind tunnel with a 76.2 cm by 76.2 cm (30 in by 30 in) cross section. Turbulent flow with a nominal mean velocity of 7.6 m/s was generated by means of a perforated plate situated at the entrance of the wind tunnel. It was found that the mean velocity increases significantly as the flow passes through the contracting passage created by the cylinders, whereas the rms turbulence intensity decreases about 12% but shows an increase of up to 14% very close to the full cylinder. As the flow was distorted, the Kolmogorov length scales were elongated in the stream-wise direction, resulting in a decrease in the rate of turbulence decay which appears as a decrease in energy dissipation rate. The stream-wise integral length scales also increased due to the elongation of eddies in the stream-wise direction. Also, analysis of the turbulence fluctuating velocity in the frequency domain showed a redistribution of stream-wise turbulence kinetic energy from large to small scales during the distortion.

Constant temperature hot-wire measurements in a short duration supersonic wind tunnel

2001 ◽  
Vol 105 (1050) ◽  
pp. 435-450 ◽  
Author(s):  
J. Weiss ◽  
H. Knauss ◽  
S. Wagner ◽  
A. D. Kosinov
Keyword(s):  
Wind Tunnel ◽  
Short Duration ◽  
Constant Temperature ◽  
Dynamic Behaviour ◽  
Free Stream ◽  
Testing Time ◽  
Hot Wire ◽  
Supersonic Wind Tunnel ◽  
Wire Temperature ◽  
Good Agreement

AbstractA constant temperature hot-wire anemometer enabling automatic rapid scanning of the wire overheat was built to perform free stream disturbance measurements in the shock wind tunnel of the Institute for Aerodynamics and Gasdynamics at Stuttgart University. It is shown that such a system brings real advantages in terms of testing time. The change of bridge dynamic behaviour with wire temperature is taken into account by measuring the bridge frequency response with a very fast electrical test and postprocessing the data. The method of operation is validated in a supersonic suck down wind tunnel and a comparison with a commercial constant temperature bridge shows good agreement. Results of free stream disturbance measurements in a short duration supersonic wind tunnel of 120ms testing time are presented.

Decay of Turbulence in Axisymmetric Wakes

1966 ◽  
Vol 88 (1) ◽  
pp. 261-267 ◽  
Author(s):  
N. H. C. Hwang ◽  
L. V. Baldwin
Keyword(s):  
Wind Tunnel ◽  
Isotropic Turbulence ◽  
Hot Wire ◽  
Mean Flow ◽  
Disk Size ◽  
The Mean ◽  
Approximate Similarity ◽  
Low Speed Wind Tunnel ◽  
Mean Flow Velocity ◽  
Circular Disks

Turbulent wakes formed downstream of flat, circular disks were surveyed with hot-wire anemometers in a low-speed wind tunnel. Three regions were discernible in the wake. Between the disk and x = 50 disk diameters D downstream, the turbulence was highly anisotropic and new turbulence was generated locally. An approximate similarity region (100 ≲ x/D ≲ 400) existed where isotropic turbulence relations were adequate for estimating decay. The far downstream wake (x/D ≳ 400) was highly intermittent throughout; the decay rate lessened in this final period. Over a 4-fold range of disk size and a 7 1/2-fold range of mean flow velocity, Taylor’s microscale was correlated by the mean residence time x/U∞; this relation was independent of disk size.

Experimental and Theoretical Investigation of the Supersonic Boundary Layer Stability on the Swept Wing

2008 ◽  
Vol 3 (3) ◽  
pp. 34-38
Author(s):  
Sergey A. Gaponov ◽  
Yuri G. Yermolaev ◽  
Aleksandr D. Kosinov ◽  
Nikolay V. Semionov ◽  
Boris V. Smorodsky
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Leading Edge ◽  
Supersonic Boundary Layer ◽  
Mean Flow ◽  
Swept Wing ◽  
Wing Model ◽  
Dimensional Boundary ◽  
The Stability ◽  
Good Agreement

Theoretical and an experimental research results of the disturbances development in a swept wing boundary layer are presented at Mach number М = 2. In experiments development of natural and small amplitude controllable disturbances downstream was studied. Experiments were carried out on a swept wing model with a lenticular profile at a zero attack angle. The swept angle of a leading edge was 40°. Wave parameters of moving disturbances were determined. In frames of the linear theory and an approach of the local self-similar mean flow the stability of a compressible three-dimensional boundary layer is studied. Good agreement of the theory with experimental results for transversal scales of unstable vertices of the secondary flow was obtained. However the calculated amplification rates differ from measured values considerably. This disagreement is explained by the nonlinear processes observed in experiment

Preliminary Evaluation of Turbulence Level Influence in Heat Transfer Measurements

2004 ◽  
Author(s):  
Carlo Carcasci ◽  
Luca Innocenti ◽  
Marco Surace
Keyword(s):  
Heat Transfer ◽  
Initial Level ◽  
Measurement Techniques ◽  
Preliminary Evaluation ◽  
Turbulence Level ◽  
Hot Wire ◽  
Aluminum Foams ◽  
Transfer Coefficients ◽  
Perforated Plates ◽  
Heat Transfer Coefficients

Heat transfer coefficients have often been experimentally measured, taking into account Nusselt number as a function of Reynolds and Prandtl number. Most experimenters spend their effort to control turbulence level, set it to different values, or keep it unchanged during the tests, as it’s not easy to predict how its initial level may change final results. The aim of this work is to add some comprehension on how different turbulence incoming levels may affect heat transfer measurements, and when it’s possible or not to neglect such effects. Experimental setup features different duct geometries, and thermocromic liquid crystals coupled with hot-wire anemometers are used as main measurement techniques. Tests were performed for Reynolds number from 10000 to 50000 and turbulence level from 3% to 12%. Several turbulence manipulators were adopted, including aluminum foams and multi-perforated plates, and results show some interesting dependences of heat transfer from both turbulence level and grid features.

High Speed Flow through Perforated Plates

1960 ◽  
Vol 64 (590) ◽  
pp. 103-105
Author(s):  
P. G. Morgan
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Perforated Plate ◽  
Wire Mesh ◽  
Flow Conditions ◽  
High Speed Flow ◽  
Perforated Plates ◽  
Speed Flow ◽  
Flow Through ◽  
Points Of View

The flow through porous screens has been widely studied from both the theoretical and experimental points of view. The most widely used types of screen are the wire mesh and the perforated plate, and the majority of the literature has been concerned with the former. Several attempts have been made to correlate the parameters governing the flow through such screens, i.e. the pressure drop, the flow conditions and the geometry of the mesh.

scholarly journals Stability and Sensitivity Analysis of Hydrodynamic Instabilities in Industrial Swirled Injection Systems

2017 ◽  
Author(s):  
Thomas L. Kaiser ◽  
Thierry Poinsot ◽  
Kilian Oberleithner
Keyword(s):  
Stability Analysis ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
Vortex Core ◽  
Large Eddy Simulations ◽  
Mode Shapes ◽  
Mean Flow ◽  
Precessing Vortex Core ◽  
Large Eddy ◽  
Good Agreement

The hydrodynamic instability in an industrial, two-staged, counter-rotative, swirled injector of highly complex geometry is under investigation. Large eddy simulations show that the complicated and strongly nonparallel flow field in the injector is superimposed by a strong precessing vortex core. Mean flow fields of large eddy simulations, validated by experimental particle image velocimetry measurements are used as input for both local and global linear stability analysis. It is shown that the origin of the instability is located at the exit plane of the primary injector. Mode shapes of both global and local linear stability analysis are compared to a dynamic mode decomposition based on large eddy simulation snapshots, showing good agreement. The estimated frequencies for the instability are in good agreement with both the experiment and the simulation. Furthermore, the adjoint mode shapes retrieved by the global approach are used to find the best location for periodic forcing in order to control the precessing vortex core.

scholarly journals THE STUDY OF ACOUSTIC CHARACTERISTICS OF THE PERFORATED AND HOMOGENOUS PLATES WITH SIMILAR GEOMETRICAL DIMENSIONS

Akustika ◽  
2019 ◽  
Vol 32 ◽  
pp. 79-82
Author(s):  
Valery Kirpichnikov ◽  
Lyudmila Drozdova ◽  
Alexei Koscheev ◽  
Ernst Myshinsky
Keyword(s):  
Resonant Frequency ◽  
Acoustic Radiation ◽  
Perforated Plate ◽  
Acoustic Characteristics ◽  
Resonant Frequencies ◽  
Perforated Plates ◽  
Resonance Frequencies ◽  
Flexural Vibrations ◽  
Geometrical Dimensions

The resonance frequencies of the flexural vibrations, input vibration excitability and acoustic radiation of the homogeneous and perforated plates were investigated. It is established that the average reduction range of the lower resonant frequency of flexural vibrations of the tested plates with the holes virtually coincides with the predictive estimate. The levels of the input vibration excitability of the perforated plate at the lower resonant frequencies exceeded the levels at the corresponding frequencies of the homogeneous plates greater than the calculated value. The levels of resonance acoustic radiation of the perforated plate were significantly less than of the homogeneous one.

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