scholarly journals An Experimental Investigation of the Effect of Bluff Body Bluntness Factor on Wake-vortex Noise Generation

2018 ◽  
Author(s):  
Weam Elsahhar ◽  
Syamir A. Showkat Ali ◽  
Raf Theunissen ◽  
Mahdi Azarpeyvand
Keyword(s):  
Experimental Investigation ◽  
Bluff Body ◽  
Wake Vortex ◽  
Noise Generation

Experimental investigation of isothermal and reacting flow characteristics downstream of axisymmetric bluff body stabilizers under stratified or fully premixed inlet mixture conditions

2020 ◽  
Author(s):  
Γεώργιος Πατεράκης
Keyword(s):  
Experimental Investigation ◽  
Turbulent Flow ◽  
Bluff Body ◽  
Operating Conditions ◽  
Reacting Flow ◽  
Wide Range ◽  
Flow Features ◽  
Air Mixing ◽  
The Impact ◽  
Stratified Flames

The current work describes an experimental investigation of isothermal and turbulent reacting flow field characteristics downstream of axisymmetric bluff body stabilizers under a variety of inlet mixture conditions. Fully premixed and stratified flames established downstream of this double cavity premixer/burner configuration were measured and assessed under lean and ultra-lean operating conditions. The aim of this thesis was to further comprehend the impact of stratifying the inlet fuelair mixture on the reacting wake characteristics for a range of practical stabilizers under a variety of inlet fuel-air settings. In the first part of this thesis, the isothermal mean and turbulent flow features downstream of a variety of axisymmetric baffles was initially examined. The effect of different shapes, (cone or disk), blockage ratios, (0.23 and 0.48), and rim thicknesses of these baffles was assessed. The variations of the recirculation zones, back flow velocity magnitude, annular jet ejection angles, wake development, entrainment efficiency, as well as several turbulent flow features were obtained, evaluated and appraised. Next, a comparative examination of the counterpart turbulent cold fuel-air mixing performance and characteristics of stratified against fully-premixed operation was performed for a wide range of baffle geometries and inlet mixture conditions. Scalar mixing and entrainment properties were investigated at the exit plane, at the bluff body annular shear layer, at the reattachment region and along the developing wake were investigated. These isothermal studies provided the necessary background information for clarifying the combustion properties and interpreting the trends in the counterpart turbulent reacting fields. Subsequently, for selected bluff bodies, flame structures and behavior for operation with a variety of reacting conditions were demonstrated. The effect of inlet fuel-air mixture settings, fuel type and bluff body geometry on wake development, flame shape, anchoring and structure, temperatures and combustion efficiencies, over lean and close to blow-off conditions, was presented and analyzed. For the obtained measurements infrared radiation, particle image velocimetry, laser doppler velocimetry, chemiluminescence imaging set-ups, together with Fouriertransform infrared spectroscopy, thermocouples and global emission analyzer instrumentation was employed. This helped to delineate a number of factors that affectcold flow fuel-air mixing, flame anchoring topologies, wake structure development and overall burner performance. The presented data will also significantly assist the validation of computational methodologies for combusting flows and the development of turbulence-chemistry interaction models.

Surface Topography and Noise Emission in Gearboxes

1997 ◽  
Author(s):  
Naser Amini ◽  
B. G. Rosén
Keyword(s):  
Experimental Investigation ◽  
Total Energy ◽  
Surface Topography ◽  
Noise Generation ◽  
Test Rig ◽  
Noise Emission ◽  
Applied Torque ◽  
Surface Topographies ◽  
Before And After ◽  
Noise Assessment

Abstract This paper, by the experimental investigation, deals with the effect of different surface topographies on noise generation in gears. Results from the noise assessment of one gear before and after honing are discussed. The honing operation was applied to the gear after the grinding. The gear was tested in an actual gearbox, operated in a test rig. Running conditions were systematically changed during the test; however, the same conditions were utilized for the gear before and after honing. The aim of the study was to identify the mechanism of the expected noise reduction, with surfaces being evaluated in 3D. The following results have been obtained: The total energy in the noise decreases significantly. The magnitude of the tooth-mesh frequency dose not change, but the level of its higher harmonics decreases significantly. These reductions are especially significant, when running at higher rotational speeds or when the applied torque is increased.

A Note on the Estimation of Average Pressures from Instantaneous Velocities in Unsteady Flow

1967 ◽  
Vol 71 (678) ◽  
pp. 440-440
Author(s):  
C. J. Wood
Keyword(s):  
Unsteady Flow ◽  
Boundary Layers ◽  
Data Reduction ◽  
Bluff Body ◽  
Wake Vortex ◽  
Two Dimensional ◽  
Experimental Check ◽  
Velocity Measurements ◽  
Periodic Disturbance ◽  
Oncoming Stream

In a recent paper, the author described some experiments in which the average base pressure on a two-dimensional bluff body was estimated from a random sample of instantaneous velocity measurements taken in the irrotational flow outside the separating boundary layers at the trailing edge. Although the oncoming stream was steady, the flow near the model was subject to a periodic disturbance emanating from the wake vortex street. An experimental check showed that the pressure estimates obtained by using the steady Bernouilli equation were reasonably accurate. This note points out that the method of data reduction used in ref. 1 is not an approximation; it is exact.

Experimental investigation of wake vortex in a water towing tank

2012 ◽  
Author(s):  
Yue Liu ◽  
Junwei Wang ◽  
Zhirong Liu ◽  
Feng Bao
Keyword(s):  
Experimental Investigation ◽  
Wake Vortex ◽  
Towing Tank
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