scholarly journals The influence of the structure of laminar flows on the characteristics of equipment

2021 ◽  
Vol 327 ◽  
pp. 05003
Author(s):  
Vasyl Arsirii ◽  
Oleg Kravchenko ◽  
Bohdan Savchuk ◽  
Olena Arsirii
Keyword(s):  
Velocity Distribution ◽  
Flow Structure ◽  
Flow Separation ◽  
Laminar Flows ◽  
Physical Models ◽  
Pulsation Velocity ◽  
Liquid Motion ◽  
Flow Paths ◽  
Transverse Structure ◽  
High Degree

The new method of visual diagnostics of liquid motion processes in physical models showed a high degree of the flow structure organization. Visual pictures made it possible to develop a hydraulic experiment to reveal the dimensions of the transverse structure in the form of layers and zones of flow separation from the channel walls. Visual diagnostics is the basis for comprehensive equipment design. Visual studies of the flow structure provide information for improving equipment by changing the geometry of the flow paths. Hydraulic studies show the change in the resistance of the equipment channels. Based on the results of visual and hydraulic studies, the wave character of the distribution of the pulsation velocity components was revealed. The regularities of the velocity distribution allow predicting the minimum or maximum values of the resistances of the flow paths of the equipment.

Flow Structure Formed by a Sweeping Jet Ejected Into a Main Flow

2018 ◽  
Author(s):  
Masaki Fuchiwaki ◽  
Surya Raghu
Keyword(s):  
Flow Control ◽  
Electric Power ◽  
Flow Structure ◽  
Flow Separation ◽  
High Velocity ◽  
Main Flow ◽  
Separation Control ◽  
Flow Separation Control ◽  
Fluidic Oscillator ◽  
Piv Measurement

Various methods of controlling flow separation have been proposed and many studies have been performed on active separation control in correspondence with the flow state. However, their efficiency has been hampered by the requirement of electric power for the added stream. Recently, an active flow separation control device based on a fluidic oscillator that does not require electric power has been reported. This device is able to generate a sweeping jet over a wide spatial range as well as fluid oscillations, and its internal structure eliminates the need for a drive unit. The studies of the flow separation control techniques using the fluidic oscillator have been reported. However, most of these results are mainly contribution of the dynamic forces from the viewpoint of the flow control and the study on the flow mechanism for the separation flow control using the fluidic oscillator have not been understood. Especially, it is not known the interaction between the sweeping jet from the fluidic oscillator and the main flow and the flow structure due to the interaction. In order to make a flow separation control devise with high efficiency using the fluidic oscillator, it is require to be understood the complex flow structure by the interaction between the sweeping jet from the fluidic oscillator and the main flow. The purpose of the present study is to investigate the flow structure by the interaction between the sweeping jet from the fluidic oscillator and the main flow quantitatively by the stereo PIV measurement. The sweeping jet ejected from a fluidic oscillator evidently disrupts the main flow at high velocity ratios, leading to a significant change in flow structure. A high-speed jet appears at the center part of the structure, accompanied by low-speed flow at the outside, producing a 3D distribution. The sweeping jet ejected from the fluidic oscillator maintains the spreading angleas a result of the interaction between the two flows at high velocity ratios.

scholarly journals Investigation of fluid flow structure in open type cavity under stationary and pulsatile flow conditions

Energetika ◽  
2016 ◽  
Vol 62 (1-2) ◽  
Author(s):  
Paulius Vilkinis ◽  
Mantas Valantinavičius ◽  
Nerijus Pedišius
Keyword(s):  
Fluid Flow ◽  
Velocity Distribution ◽  
Flow Structure ◽  
Cross Section ◽  
Middle Part ◽  
Pulsating Flow ◽  
Primary Vortex ◽  
Open Type ◽  
Micro Particle Image Velocimetry ◽  
Entire Height

A study of fluid flow in structured channels plays an important role in solving most fluid dynamics problems. The  knowledge of the  flow structure in separate cavities can be used to intensify mixing in microreactors and microelectrochemical systems (MEMS) as well as to increase heat transfer in heat sinks. Besides, knowledge about fluid flow in micro cavities could be useful to mitigate the symptoms of aneurysms. In this study, a 2D micro-particle image velocimetry (µPIV) system was used to investigate water flow in an open-type microcavity located in a straight, square cross-section (0.5  ×  0.5  mm2) microchannel. Two identical micro cavities of the  same cross-section as the  main channel and the  depth of 1  mm are oppositely located in the middle part of the channel. Because of symmetry, the flow structure of the primary vortex was investigated in only one cavity. Measurements were carried out in different planes over the entire height of the cavity at Reynolds number in the range from 100 to 3000. The flow in the channel was stationary and pulsating. Results indicate that flow in the cavity is three-dimensional. This is confirmed by velocity profile shape changes in its different transversal planes. In addition, it is determined that flow structure in the  cavity depends on flow regime and flow pulsation characteristics. Velocity distribution shows that in the transverse direction there is the minimum velocity zone corresponding to the centre of the primary vortex generated by the channel flow, also the same zone is observed along the cavity in its axial plane. At low Re, such velocity distribution occurs in pulsating flow earlier than in the case of stationary flow. With increasing Re, velocity distribution in pulsating flow flattens out also more. It means that disturbed flow in the channel accelerates the formation of a stable flow structure in the cavity.

scholarly journals A conceptual design and numerical analysis of the mixerless urea-SCR system

2021 ◽  
Author(s):  
Bartosz Kaźmierski ◽  
Krzysztof Górka ◽  
Łukasz Kapusta
Keyword(s):  
Catalytic Reduction ◽  
Film Deposition ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Flow Paths ◽  
Wall Film ◽  
Compact Design ◽  
Scr System ◽  
High Degree ◽  
Operating Points

In the present study, an innovative design of the urea-selective catalytic reduction (SCR) system without conventional mixing elements was developed. The aim was to obtain a high degree of urea decomposition, and uniform ammonia distribution at the inlet to the catalyst, while minimising the liquid film deposition and keeping the compact design. The concept of the design was based on creating high turbulences and elongating the flow paths of the droplets. The design was verified through a series of numerical simulations based on the Reynolds-averaged Navier–Stokes (RANS) approach and a discrete droplet model (DDM) spray representation. The analysis included various operating conditions as well as subcooled and superheated sprays. A uniform ammonia distribution was achieved regardless of the operating points and spray properties. Additionally, in the case of the flash-boiling injection, a further reduction of the wall film was observed.

Dynamic Convolution Modeling, a Hybrid Synthesis Strategy

2013 ◽  
Vol 37 (1) ◽  
pp. 44-51
Author(s):  
David Bessell
Keyword(s):  
Physical Modeling ◽  
Hybrid Approach ◽  
Synthesis Method ◽  
Physical Models ◽  
Synthesis Process ◽  
Spectral Features ◽  
Synthesis Strategy ◽  
Percussion Instruments ◽  
High Degree ◽  
Percussive Instruments

This article outlines a hybrid approach to the synthesis of percussion sounds. The synthesis method described here combines techniques and concepts from physical modeling and convolution to produce audio synthesis of percussive instruments. This synthesis method not only achieves a high degree of realism in comparison with audio samples but also retains some of the flexibility associated with waveguide physical models. When the results are analyzed, the method exhibits some interesting detailed spectral features that have some aspects in common with the behavior of acoustic percussion instruments. In addition to outlining the synthesis process, the article discusses some of the more creative possibilities inherent in this approach, e.g., the use and free combination of excitation and resonance sources from beyond the realms of the purely percussive examples given.

A High-Loaded Axial Compressor Bifurcate Stator Blade Aerodynamic Design and Vorticity Dynamics Diagnosis for Flow Structure

2017 ◽  
Author(s):  
Huanlong Chen ◽  
Menghan Yu ◽  
Linxi Li ◽  
Huaping Liu
Keyword(s):  
Pressure Gradient ◽  
Flow Structure ◽  
Flow Separation ◽  
Wake Flow ◽  
Flow Area ◽  
Blade Passage ◽  
Aerodynamic Loss ◽  
Gentle Pressure ◽  
Vorticity Dynamics ◽  
Layer Flow

On the flow instability caused by large scale boundary-layer flow separation in highly loaded compressor/fan blade passage, a novel bifurcate compressor blade is designed based on pressure gradient control idea for blade passage flow, and a distinctive variable solidity bifurcate blade concept and three-dimensional blade design technology are integrated to achieve this design idea in this paper. The quantitative flow information for the bifurcate blade passage is obtained by numerical simulation method to investigate the separation flow structure and dynamic mechanism near the wall and in the wake flow area. Besides, the complex influence of vortex structure evolution and the dynamic mechanism of low energy fluid redistribution being controlled in boundary-layer flow area would be revealed by applying the vorticity dynamics theory. The variable law of design parameters is explored in order to decrease aerodynamic loss, to delay flow separation near the wall and corner for the blade surface, to restructure blade aerodynamic loading, to form gentle pressure gradient and to diminish wake flow loss. The results indicate that although extra aerodynamic loss is generated by the geometric mutation of bifurcate segment, the bifurcate blade effectively restrains the migration of high-entropy secondary flow fluid in the shroud corner area, thus substantially decreasing the loss near endwall/corner, which remarkably promotes the aerodynamic performance, particularly under the condition of positive incidence angle. Moreover, the bifurcate blade skillfully remolds the pressure gradient on the blade surface, and promotes total pressure as well as velocity for the wake area that would be beneficial for the downstream rotor blade. With the introduction of key physical concepts and flow parameters of vortex/vorticity dynamics, such as boundary vorticity flux, vorticity vector, skin-friction vector and tangential pressure gradient, the physical root source and mechanism of gentle pressure gradient formation, wake flow structure being weakened, and flow separation reduction for the endwall and corner are further revealed.

Laminar flow in rotating curved pipes

1996 ◽  
Vol 329 ◽  
pp. 373-388 ◽  
Author(s):  
Hiroshi Ishigaki
Keyword(s):  
Experimental Data ◽  
Laminar Flow ◽  
Friction Factor ◽  
Flow Structure ◽  
Flow Characteristics ◽  
Laminar Flows ◽  
Dean Number ◽  
Governing Parameter ◽  
Curved Pipes ◽  
Wide Range

When a curved pipe rotates about the centre of curvature, the fluid flowing in it is subjected to both Coriolis and centrifugal forces. Based on the analogy between laminar flows in stationary curved pipes and in orthogonally rotating pipes, the flow characteristics of fully developed laminar flow in rotating curved pipes are made clear and definite by similarity arguments, computational studies and using experimental data. Similarity arguments clarify that the flow characteristics in loosely coiled rotating pipes are governed by three parameters: the Dean number KLC, a body force ratio F and the Rossby number Ro. As the effect of Ro is negligible when Ro is large, computational results are presented for this case first, and then the effect of Ro is studied. Flow structure and friction factor are studied in detail. Variations of flow structure show secondary flow reversal at F ≈ −1, where the two body forces are of the same order but in opposite directions. It is also shown how the Taylor–Proudman effect dominates the flow structure when Ro is small. Computed curves of the friction factor for constant Dean number have their minimum at F ≈ −1. A composite parameter KL is introduced as a convenient governing parameter and used to correlate the characteristics. By applying KL to the analogy formula previously derived for two limiting flows, a semi-empirical formula for the friction factor is presented, which shows good agreement with the experimental data for a wide range of the parameters.

scholarly journals Wind Conditions at Pedestrian Level in Different Types of Residential Urban Development for a High Degree of Land Use Efficiency

2021 ◽  
Vol 13 (24) ◽  
pp. 13612
Author(s):  
Katarzyna Zielonko-Jung ◽  
Marta Poćwierz ◽  
Robert Idem
Keyword(s):  
Experimental Studies ◽  
Physical Models ◽  
Amplification Coefficient ◽  
Airflow Velocity ◽  
Housing Developments ◽  
Land Use Efficiency ◽  
Different Types ◽  
Use Efficiency ◽  
Family Housing ◽  
High Degree

This paper addresses wind conditions in urban building development at the pedestrian level. The article aimed to identify aerodynamic phenomena around three types of multi-family housing developments with different forms and the same urban parameters of building development density (high density was taken into account). The aim of the research was mainly to achieve qualitative results that would lead to understanding fundamental processes and phenomena. Wind tunnel experimental studies were conducted on physical models at a scale of 1: 400 using visualization and erosion methods. These experiments yielded data regarding the arrangement of airflow directions and changes in airflow velocity, expressed as the amplification coefficient (α), the occurrence of which was caused by the presence of buildings. An analysis was conducted concerning wind conditions that constitute pedestrian comfort and influence the possibility for ventilation of spaces between buildings for the three selected models. The research results were compared, and an attempt was made to assess the most beneficial and the least favorable building development types in this respect.

scholarly journals Physical models for classroom teaching in hydrology

2012 ◽  
Vol 16 (9) ◽  
pp. 3075-3082 ◽  
Author(s):  
A. Rodhe
Keyword(s):  
Hydraulic Properties ◽  
Groundwater Table ◽  
Physical Models ◽  
Classroom Teaching ◽  
Flow Paths ◽  
Contaminant Dispersion ◽  
Sand Aquifer ◽  
University Level ◽  
Tracer Experiments

Abstract. Hydrology teaching benefits from the fact that many important processes can be illustrated and explained with simple physical models. A set of mobile physical models has been developed and used during many years of lecturing at basic university level teaching in hydrology. One model, with which many phenomena can be demonstrated, consists of a 1.0-m-long plexiglass container containing an about 0.25-m-deep open sand aquifer through which water is circulated. The model can be used for showing the groundwater table and its influence on the water content in the unsaturated zone and for quantitative determination of hydraulic properties such as the storage coefficient and the saturated hydraulic conductivity. It is also well suited for discussions on the runoff process and the significance of recharge and discharge areas for groundwater. The flow paths of water and contaminant dispersion can be illustrated in tracer experiments using fluorescent or colour dye. This and a few other physical models, with suggested demonstrations and experiments, are described in this article. The finding from using models in classroom teaching is that it creates curiosity among the students, promotes discussions and most likely deepens the understanding of the basic processes.

scholarly journals Recovering the Pulsation Velocity Distribution on Stellar Surface

1998 ◽  
Vol 185 ◽  
pp. 383-384
Author(s):  
J. Hao
Keyword(s):  
Velocity Field ◽  
Velocity Distribution ◽  
Line Profile ◽  
Numerical Experiments ◽  
Doppler Imaging ◽  
Pulsation Velocity ◽  
Line Profiles ◽  
One Dimensional ◽  
The One ◽  
Nonradial Pulsation

The analytical expression between the line profile and its corresponding pulsation velocity field is derived by the assumption of Doppler Imaging (DI). Based on this approach, numerical experiments of the recovery of the one dimensional nonradial pulsation velocity distribution from the residual line profiles are presented.

Hydrostratigraphy of the Malmani Subgroup dolomites within the northeastern escarpment (Limpopo and Mpumalanga, South Africa)

2019 ◽  
Vol 122 (3) ◽  
pp. 283-298
Author(s):  
S.S.E. Mndaweni ◽  
S. Naicker ◽  
D. Blake
Keyword(s):  
Surface Water ◽  
Groundwater Flow ◽  
Water Discharge ◽  
Karst Aquifer ◽  
Groundwater Potential ◽  
Flow Paths ◽  
Discharge Rates ◽  
Management Area ◽  
Transvaal Supergroup ◽  
High Degree

Abstract The Late Archaean to Early Proterozoic Malmani Subgroup comprises of dolomites and limestones forming part of the Chuniespoort Group within the Transvaal Supergroup, outcropping as an arc structure east of the Pretoria Group along the Limpopo and Mpumalanga escarpment. These rocks form a fractured karst aquifer in the area and have a high degree of heterogeneity and anisotropy. The aquifers are unconfined to semi-confined, with compartmentalisation by dolerite dykes being a possible effect (if the dykes are large and extensive enough) due to the dykes acting as aquitards or barriers to groundwater flow. The contact zones between the dolomite formations and dolerite dykes are usually fractured however, and along with any other faults and fractures result in preferential dolomite dissolution and the development of groundwater flow paths in the area. Borehole yields ranges between 2 to 5 l/s and potentially >10 l/s per borehole in the vicinity of large regional fractures or dolerite intrusions. Groundwater from the Malmani Subgroup generally meets the drinking water quality standards for major constituents and it is of Mg-Ca-HCO3 nature. Groundwater development within this particular hydrostratigraphy is linked to potential well field target zones that take cognisance of various surface water-groundwater interaction affecting surface water discharge rates as well as groundwater over-abstraction concerns. Preliminary results have indicated that given a groundwater potential of 44 hm3/a, the aquifer will be able to support abstractions of up to 29 hm3/a if systematically developed adaptively and could be used and managed conjunctively with surface water to alleviate the pressure on the already stressed Olifants Water Management Area.

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