scholarly journals Hydraulic resistances of suspended flows in bedrooms with a moving bottom

2021 ◽  
Vol 264 ◽  
pp. 03017
Author(s):  
Kenesbay Baimanov ◽  
Gulmurat Shaniyazov ◽  
Torebek Uzakov ◽  
Ruslan Baimanov
Keyword(s):  
Boundary Layer ◽  
Hydraulic Resistance ◽  
Field Data ◽  
Experimental Studies ◽  
Alluvial Soils ◽  
Natural Conditions ◽  
Mixed Zone ◽  
Mobile Bed ◽  
Logarithmic Distribution ◽  
Mass Field

The results of some existing theoretical and experimental studies of hydraulic resistances of open flows in moving channels are considered. Possible reasons for the inconsistency of the results of various studies of hydraulic resistance in open channels with increased roughness are indicated. The analysis of mass field data on the Darcy (Shezi) coefficient of canals in alluvial soils and a sandy mobile bed is carried out. It was confirmed that the channels of these categories are characterized by a mixed zone of hydraulic resistance, and regularities were revealed that take into account the features of the real resistance zone of earthen channels. Based on the analysis of the smoothly varying flow of open flows and the corresponding theory of the boundary layer and the law of the logarithmic distribution of velocities, the calculated dependencies are obtained, making it possible to determine the resistance of open flows concerning natural conditions.

Effect of Boundary Layer Suction on Aerodynamic Performance of High-Turning Compressor Cascade

2013 ◽  
Author(s):  
Longxin Zhang ◽  
Shaowen Chen ◽  
Hao Xu ◽  
Jun Ding ◽  
Songtao Wang
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Experimental Studies ◽  
Aerodynamic Performance ◽  
Parameter Distribution ◽  
Compressor Cascade ◽  
Boundary Layer Suction ◽  
End Wall ◽  
Low Speed Wind Tunnel ◽  
Good Agreement

Compared with suction slots, suction holes are (1) flexible in distribution; (2) alterable in size; (3) easy to fabricate and (4) high in strength. In this paper, the numerical and experimental studies for a high turning compressor cascade with suction air removed by using suction holes in the end-wall at a low Mach numbers are carried out. The main objective of the investigation is to study the influence of different suction distributions on the aerodynamic performance of the compressor cascade and to find a better compound suction scheme. A numerical model was first made and validated by comparing with the experimental results. The computed flow visualization and exit parameter distribution showed a good agreement with experimental data. Second, the model was then used to simulate the influence of different suction distributions on the aerodynamic performance of the compressor cascade. A better compound suction scheme was obtained by summarizing numerical results and tested in a low speed wind tunnel. As a result, the compound suction scheme can be used to significantly improve the performance of the compressor cascade because the corner separation gets further suppressed.

scholarly journals How Embodied Cognitions Affect Judgments: Height-Related Attribution Bias in Football Foul Calls

2010 ◽  
Vol 32 (1) ◽  
pp. 3-22 ◽  
Author(s):  
Niels van Quaquebeke ◽  
Steffen R. Giessner
Keyword(s):  
Field Data ◽  
Experimental Studies ◽  
Attribution Bias ◽  
Consistent Support

Many fouls committed in football (called soccer in some countries) are ambiguous, and there is no objective way of determining who is the “true” perpetrator or the “true” victim. Consequently, fans as well as referees often rely on a variety of decision cues when judging such foul situations. Based on embodiment research, which links perceptions of height to concepts of strength, power, and aggression, we argue that height is going to be one of the decision cues used. As a result, people are more likely to attribute a foul in an ambiguous tackle situation to the taller of two players. We find consistent support for our hypothesis, not only in field data spanning the last seven UEFA Champions League and German Bundesliga seasons, as well as the last three FIFA World Cups, but also in two experimental studies. The resulting dilemma for refereeing in practice is discussed.

scholarly journals Experimental studies on particle emissions from cruising ship, their characteristic properties, transformation and atmospheric lifetime in the marine boundary layer

2007 ◽  
Vol 7 (5) ◽  
pp. 15105-15154 ◽  
Author(s):  
A. Petzold ◽  
J. Hasselbach ◽  
P. Lauer ◽  
R. Baumann ◽  
K. Franke ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Particle Number ◽  
Marine Boundary Layer ◽  
Experimental Studies ◽  
Test Bed ◽  
Test Rig ◽  
Particle Emissions ◽  
Airborne Measurements ◽  
Emission Studies ◽  
Transformation Processes

Abstract. Particle emissions from ship engines and their atmospheric transformation in the marine boundary layer (MBL) were investigated in engine test bed studies and in airborne measurements of expanding ship plumes. During the test rig studies, detailed aerosol microphysical and chemical properties were measured in the exhaust gas of a serial MAN B{&amp;}W seven-cylinder four-stroke marine diesel engine under various load conditions. The emission studies were complemented by airborne aerosol transformation studies in the plume of a large container ship in the English Channel using the DLR aircraft Falcon 20 E-5. Observations from emission studies and plume studies combined with a Gaussian plume dispersion model yield a consistent picture of particle transformation processes from emission to atmospheric processing during plume expansion. Particulate matter emission indices obtained from plume measurements are 8.8±1.0×1015(kg fuel)−1 by number for non-volatile particles and 174±43 mg (kg fuel)−1 by mass for Black Carbon (BC). Values determined for test rig conditions between 85 and 110% engine load are of similar magnitude. For the total particle number including volatile compounds no emission index can be derived since the volatile aerosol fraction is subject to rapid transformation processes in the plume. Ship exhaust particles occur in the size range Dp<0.3 μm, showing a bi-modal structure. The combustion particle mode is centred at modal diameters of 0.05 μm for raw emissions to 0.10 μm at a plume age of 1 h. The smaller-sized volatile particle mode is centred at Dp≤0.02 μm. From the decay of ship exhaust particle number concentrations in an expanding plume, a maximum plume life time of approx. 24 h is estimated for a well-mixed marine boundary layer.

Wavenumber Spectra of High Magnitude Wall Pressure Events in a Numerically Simulated Turbulent Boundary Layer

1997 ◽  
Vol 119 (2) ◽  
pp. 281-288
Author(s):  
B. M. Abraham ◽  
W. L. Keith
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Fourier Transforms ◽  
Experimental Studies ◽  
Detection Algorithm ◽  
Wall Pressure ◽  
Negative Events ◽  
Discrete Fourier Transforms ◽  
High Magnitude ◽  
The Time Domain

A method for conditionally sampling the spatial field of the wall pressure beneath a turbulent boundary layer in order to search for high magnitude events and calculate the corresponding wavenumber spectrum is presented. The high magnitude events are found using a simple peak detection algorithm at a fixed instant in time and the wavenumber spectra are calculated using discrete Fourier transforms. The frequency of occurrence for high magnitude positive events is found to be approximately the same as for high magnitude negative events. The contribution of the high magnitude events to the rms wall pressure for various trigger levels is calculated and compared with results from similar experimental studies performed in the time domain. The high magnitude events are shown to occur infrequently and to contribute significantly to the rms wall pressure. Wavenumber spectra from the high magnitude positive and negative events are calculated and compared with the unconditionally sampled spectra. The high magnitude events contain energy focused around a particular stream-wise wavenumber and have high broadband spectral levels.

A numerical investigation of the Stokes boundary layer in the turbulent regime

2007 ◽  
Vol 570 ◽  
pp. 253-296 ◽  
Author(s):  
S. SALON ◽  
V. ARMENIO ◽  
A. CRISE
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Time Scale ◽  
Mixed Model ◽  
Experimental Studies ◽  
Outer Region ◽  
Transition To Turbulence ◽  
Turbulent Regime ◽  
Turbulent Statistics ◽  
Acceleration And Deceleration

The Stokes boundary layer in the turbulent regime is investigated by using large-eddy simulations (LES). The Reynolds number, based on the thickness of the Stokes boundary layer, is set equal to Reδ = 1790, which corresponds to test 8 of the experimental study of Jensen et al. (J. Fluid Mech. vol. 206, 1989, p. 265).Our results corroborate and extend the findings of relevant experimental studies: the alternating phases of acceleration and deceleration are correctly reproduced, as is the sharp transition to turbulence, observable at a phase angle between 30° and 45°, and its maximum between 90° and 105°. Overall, a very good agreement was found between our LES first- and second-order turbulent statistics and those of Jensen et al. (1989). Some discrepancies were observed when comparing turbulent intensities in the phases of the cycle characterized by a low level of turbulent activity.In the central part of the cycle, namely from the mid acceleration to the late deceleration phases, fully developed equilibrium turbulence is present in the flow field, and the boundary layer resembles that of a canonical, steady, wall-bounded flow. In those phases characterized by low turbulent activity, two separate regions can be detected in the flow field: a near-wall one, where the vertical turbulent kinetic energy varies much more rapidly than the other two components, thus giving rise to the formation of horizontal, pancake-like turbulence; and an outer region where both vertical and spanwise velocity fluctuations vary much faster than the streamwise ones, hence producing cigar-like turbulence.As a side result, the range of application of the plane-averaged dynamic mixed model was assessed based on the qualitative behaviour over the cycle of a significant parameter representing the ratio between a turbulent time scale and a free-stream time scale associated with the oscillatory motion.

scholarly journals Intensity of convective motions in marine atmospheric boundary layer retrieved from ocean surface radar imagery

2006 ◽  
Vol 13 (3) ◽  
pp. 303-308 ◽  
Author(s):  
M. I. Mityagina
Keyword(s):  
Boundary Layer ◽  
Aspect Ratio ◽  
Atmospheric Boundary Layer ◽  
Coherent Structures ◽  
Marine Atmospheric Boundary Layer ◽  
Natural Conditions ◽  
Radar Images ◽  
Radar Imagery ◽  
Convective Motions ◽  
Atmospheric Motion

Abstract. The paper focuses on the occurrence and development of coherent structures observed in the atmosphere above ocean under natural conditions. Microwave imaging radars are suggested as data take instruments. The phenomena of marine atmospheric cells and rolls onset, horizontal planform, aspect ratio and scaling phenomena are examined. Convective patterns manifested in radar images and information derived on the intensity of atmospheric motion are discussed.

scholarly journals Research of the hydraulic resistance of the granular filter of the sweeping mashnine

2019 ◽  
Vol 135 ◽  
pp. 01049
Author(s):  
Rashid Sharapov
Keyword(s):  
Hydraulic Resistance ◽  
Experimental Studies ◽  
Air Purification ◽  
Technological Parameters ◽  
Variable Parameters ◽  
Granular Filter ◽  
Modern Cities ◽  
Mathematical Expressions ◽  
Cleaning Equipment ◽  
Analytical Expressions

The article focuses on the need to improve the ecology in modern cities based on the development of new cleaning equipment. It is proposed to use a granular filter as a dust cleaning unit in sweeping machines. The advantages of granular filters over other types of filtering apparatus are given. The basic schemes of working equipment of sweepers are considered. To describe the processes during air purification in the proposed granular filter, mathematical expressions are proposed to determine the hydraulic resistance of the proposed filter. When developing analytical expressions, the structural and technological features of the proposed filter were taken into account. The results of calculating the hydraulic resistance of the proposed granular filter depending on its main structural and technological parameters are obtained. To confirm the obtained analytical expressions, experimental studies were carried out. The clinker of the Belgorod cement plant of a fraction of -10 + 5 mm was selected as the filtering material. During the experiment, cement was used as dust with a specific surface of various dispersion, determined by the parameter δ50. In addition, filtering speed and filtering time are accepted as variable parameters.

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