scholarly journals Influence of Non-Structural Parameters on Dual Parallel Jet Characteristics of Porous Nozzles

Micromachines ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 772
Author(s):  
Jin Zhang ◽  
Ruiqi Lv ◽  
Qifan Yang ◽  
Baolei Liu ◽  
Ying Li
Keyword(s):  
Energy Transport ◽  
Structural Parameters ◽  
Inlet Pressure ◽  
Starting Point ◽  
Spacing Ratio ◽  
Pressure Peak ◽  
Jet Characteristics ◽  
Pressure Nozzle ◽  
Jet Axis ◽  
Nozzle Spacing

As an important actuator of the dual parallel jet, the porous nozzle has some non-structural parameters (such as inlet pressure, nozzle spacing ratio, etc.) which have a significant influence on energy transport, chemical combustion and pollutant generation. The research on the microfluidic state of the porous nozzle dual parallel jet, however, remains insufficient because of its microjet pattern and complex intersection process. In this paper, the authors used numerical simulation and an experimental method to clarify the influence of porous nozzles’ non-structural parameters on dual parallel jet characteristics. The results show that the inlet pressure only changes the pressure peak value on the parallel jet axis; the starting point (SP) and peak point (PP) on the parallel jet axis, which are located at Xsp = 22 mm and Xpp = 75 mm, respectively, are not changed; and with the increase in the nozzle spacing ratio, the merging points (MPs) on the parallel jet axis are Xmp = 25 mm, 32 mm and 59 mm, respectively. The merging point and the combined point move to a farther distance and the inner deflection angle of the jet is weakened.

scholarly journals Experimental Investigation of Nozzle Spacing Effects on Characteristics of Round Twin Free Jets

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Andrew Laban ◽  
Seyed Sobhan Aleyasin ◽  
Mark Francis Tachie ◽  
Mike Koupriyanov
Keyword(s):  
Symmetry Plane ◽  
Shear Layers ◽  
Significant Rise ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Potential Core ◽  
Turbulent Statistics ◽  
Spacing Ratio ◽  
Stress Ratios ◽  
Nozzle Spacing

The objective of this paper is to investigate the effects of nozzle spacing on the mean velocity and higher-order turbulent statistics of free twin round jets produced from sharp contraction nozzles. The experiments were performed in an air chamber where four nozzle spacing ratios, S/d = 2.8, 4.1, 5.5, and 7.1, were investigated at a fixed Reynolds number of 10,000. A planar particle image velocimetry (PIV) system was used to conduct the velocity measurements. The results show that downstream of the potential core, a reduction in spacing ratio leads to an earlier and more intense interaction between the jets, indicated by enhanced half-velocity width spread rate in the inner shear layers and a significant rise of turbulent intensities and vorticity thickness along the symmetry plane. A reduction in spacing ratio, however, confines the ambient fluid entrainment along the inner shear layers leading to a reduced core jet velocity decay rate. The closer proximity of the jets also leads to the decrease of Reynolds stresses in the inner shear layers but not in the outer shear layers. The Reynolds stress ratios along the jet centerline reveal the highest anisotropy in the potential core region.

Damping Mechanisms in Cable-Harnessed Structures for Space Applications: Analytical Modeling

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Pranav Agrawal ◽  
Armaghan Salehian
Keyword(s):  
Structural Parameters ◽  
Analytical Models ◽  
Space Structures ◽  
Real Time Control ◽  
Space Applications ◽  
Time Control ◽  
Starting Point ◽  
Recent Developments ◽  
Damping Effects ◽  
Distributed Transfer Function

Abstract Recent developments in the aerospace industry have driven focus toward accurately modeling the effects of the cables and electronic cords on space structures. In the past, researchers have modeled the mass and stiffness effects of these cables but primarily overlooked their damping effects through careful analytical model developments. The objective of the current work is to present analytical models for cable-harnessed structures that also include the damping effects in their vibration response. Obtaining simple, low-order and high-fidelity models are highly advantageous in designing robust vibration real-time control algorithms for structures. Additionally, the analytical models are useful tools in providing insight into and better understanding of the dynamics of space structures as they are often difficult to be tested prior to launch due to their large size and at best only a few components may be tested. Motivated by the space applications, this work considers beam structures wrapped with cables which are modeled using beam and string theory assumptions. Two different damping models namely Kelvin–Voigt and hysteretic damping are considered. The homogenization approach is used as a starting point for structures of periodic wrapping patterns. Using the variational principle, the governing partial differential equation for the transverse coordinate of vibrations is found for three cable patterns and the results are compared to those from the distributed transfer function method (DTFM). Finally, the effects of several structural parameters are studied on the overall system damping.

Study on Heat Transfer Performance Affected by Structural Parameters of Multi-Channel Cylinder Dryer

2016 ◽  
Author(s):  
Yan Yan ◽  
Dong Jixian ◽  
Tang Wei ◽  
Feng Shiyuf
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Aspect Ratio ◽  
Transfer Coefficient ◽  
Heat Transfer Performance ◽  
Flow Characteristic ◽  
Structural Parameters ◽  
Transfer Performance ◽  
Spacing Ratio ◽  
Condensing Heat Transfer

An approach to design multi-channel cylinder dryer was proposed. The heat transfer performance and flow characteristic under various structural parameters were analyzed. First, an experiment was designed and set up to measure the condensing heat transfer coefficient and the pressure drop in order to verify the applicability of the Cavallini’s correlation. Then, the relationship among the count of channels, aspect ratio, spacing ratio, width, height and hydraulic diameter of a channel was given. Finally, the correlation of condensing heat transfer and the homogeneous model were introduced in order to observe the heat transfer performance and flow characteristic of the multi-channel cylinder dryer affected by different structures. The study reveals that the structural parameters including count of channels, aspect ratio, spacing ratio of a channel dramatically influence the condensation heat transfer coefficient and frictional resistance of the steam. Based on the selected paper machine, it is suggested that the overall performance of the multi-channel cylinder dryer is best if the count of channels is 150–200, the aspect ratio is 1:3 and the spacing ratio is 1:1–1:3.

The Lubrication Regime at Pin-Pulley Interface in Chain CVTs

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
G. Carbone ◽  
M. Scaraggi ◽  
L. Soria
Keyword(s):  
Pressure Distribution ◽  
High Pressures ◽  
Elastohydrodynamic Lubrication ◽  
Asperity Contact ◽  
Normal Stress Distribution ◽  
Lubrication Regime ◽  
Starting Point ◽  
High Fatigue ◽  
Variable Transmission ◽  
Pressure Peak

This paper deals with the strongly nonstationary squeeze of an oil film at the interface between the chain pin and pulley in chain belt continuously variable transmission. We concentrate on the squeeze motion as it occurs as soon as the pin enters the pulley groove. The duration time to complete the squeeze process compared with the running time the pin takes to cover the entire arc of contact is fundamental to understand whether direct asperity-asperity contact occurs between the two approaching surfaces to clarify what actually is the lubrication regime (elastohydrodynamic lubrication (EHL), mixed, or boundary) and to verify if the Hertzian pressure distribution at the interface can properly describe the actual normal stress distribution. The Hertzian pressure solution is usually taken as a starting point to design the geometry of the pin surface; therefore, it is of utmost importance for the designers to know whether their hypothesis is correct or not. Taking into account that the traveling time, the pin spends in contact with the pulley groove, is of about 0.01 s, we show that rms surface roughness less than 0.1 μm, corresponding to values adopted in such systems, guarantees a fully lubricated EHL regime at the interface. Therefore, direct asperity-asperity contact between the two approaching surfaces is avoided. We also show that the Hertzian solution does not properly represent the actual pressure distribution at the pin-pulley interface. Indeed, after few microseconds a noncentral annular pressure peak is formed, which moves toward the center of the pin with rapidly decreasing speed. The pressure peak can grow up to values of several gigapascals. Such very high pressures may cause local overloads and high fatigue stresses that must be taken into account to correctly estimate the durability of the system.

Urban transformations and changing patterns of local risk: lessons from the Mekong Region

2015 ◽  
Vol 6 (1) ◽  
pp. 30-43 ◽  
Author(s):  
Richard M. Friend ◽  
Pakamas Thinphanga ◽  
Kenneth MacClune ◽  
Justin Henceroth ◽  
Phong Van Gai Tran ◽  
...  
Keyword(s):  
Energy Transport ◽  
Multiple Scales ◽  
Practical Experience ◽  
Original Research ◽  
Rapid Urbanization ◽  
Content Type ◽  
Mekong Region ◽  
Urban Disaster ◽  
Starting Point ◽  
Local Risk

Purpose – This paper aims to fill a conceptual gap in the understanding of rapidly changing characteristics of local risk, addressing how the notion of the local might be reframed, and how opportunities for multi-scale interventions for disaster risk reduction might be identified. Design/methodology/approach – The paper illustrates the significance of the systems and services on which urbanization depends – water, food, energy, transport and communications – to consider the cascading impacts at multiple scales often beyond the administrative boundaries of cities, and how vulnerabilities and risks are distributed unevenly across different groups of people. Findings – The process of rapid urbanization in the Mekong Region represents a fundamental transformation of ecological landscapes, resource flows, livelihoods and demographics. In addition to the location of urbanization, it is these transformative processes and the critical dependence on inter-linked systems that shape the overall picture of urban disaster and climate vulnerability. Research limitations/implications – By drawing on research and practical experience in two of the most rapidly urbanizing countries in the world, Thailand and Vietnam, the approach and findings have implications for understanding global patterns of urbanization. Practical implications – The paper contributes to considering practical actions whether in terms of policy or project implementation for both the assessment of disaster and climate risk, and for actions to reduce vulnerability and promote resilience. Social implications – The paper draws largely from social science perspectives, highlighting the dynamism of social organization in urbanizing contexts, and the implications for risk and vulnerability. Originality/value – The paper draws on original research in Thailand and Vietnam that takes urbanization as the starting point for assessing vulnerability and risk.

scholarly journals A standardised, holistic framework for concept-map analysis combining topological attributes and global morphologies

2015 ◽  
pp. 20-35
Keyword(s):  
Structural Analysis ◽  
Concept Maps ◽  
Systematic Approach ◽  
Structural Parameters ◽  
Concept Map ◽  
Degree Sequence ◽  
Original Form ◽  
Starting Point ◽  
Balanced Tree ◽  
Map Analysis

Motivated by the diverse uses of concept maps in teaching and educational research, we have developed a systematic approach to their structural analysis. The basis for our method is a unique topological normalisation procedure whereby a concept map is first stripped of its content and subsequently geometrically re-arranged into a standardised layout as a maximally balanced tree following set rules. This enables a quantitative analysis of the normalised maps to read off basic structural parameters: numbers of concepts and links, diameter, in- and ex-radius and degree sequence and subsequently calculate higher parameters: cross-linkage, balance and dimension. Using these parameters, we define characteristic global morphologies: ‘Disconnected’, ‘Imbalanced’, ‘Broad’, ‘Deep’ and ‘Interconnected’ in the normalised map structure. Our proposed systematic approach to concept-map analysis combining topological normalisation, determination of structural parameters and global morphological classification is a standardised, easily applicable and reliable framework for making the inherent structure of a concept map tangible. It overcomes some of the subjectivity inherent in analysing and interpreting maps in their original form while also avoiding the pitfalls of an atomistic analysis often accompanying quantitative concept-map analysis schemes. Our framework can be combined and cross-compared with a content analysis to obtain a coherent view of the two key elements of a concept map: structure and content. The informed structural analysis may form the starting point for interpreting the underlying knowledge structures and pedagogical meanings.

scholarly journals Plunging jets from orifices of different geometry

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Giorgio Moscato ◽  
Giovanni Paolo Romano
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Air Bubbles ◽  
Natural Processes ◽  
Water Jets ◽  
Starting Point ◽  
Air Water Interface ◽  
Plunging Jets ◽  
Small Reynolds Numbers ◽  
Jet Characteristics

Plunging jets are used in many industrial and civil applications, as for example in sewage and water treatment plants, in order to enhance aeration and mass transfer of volatile gases. They are also observed in natural processes as rivers self-purification, waterfalls and weirs. Many investigations dealt with the plunging jets in different configurations, but the dependence on Reynolds number and jet geometry were still not sufficiently addressed. For example, Mishra et al. (2020) studied an oblique submerged water impinging jet at different nozzle-to-plate distances and impingement angles, but only at a rather small Reynolds numbers (2600). On the other hand, different jet geometries have been extensively considered, but not for the plunging jet configuration (Mi, 2000; Hashiehbaf &Romano, 2013). In this work, plunging water jets issuing in air from orifices of different shape are considered. The aim of the work is to detail and compare jet behaviors in terms of velocity fields generated after impacting the air-water interface, as a function of Reynolds number and orifice geometry. However, air bubbles entrainment is mainly avoided in order to study the jet characteristics in a simpler case and use it as a reference starting point for future works.

Study of the Influence Rules between Structural Parameters and Jet Characteristics of a Liquamatic Fire Water Monitor with Self-Swinging Device

2010 ◽  
Vol 37-38 ◽  
pp. 1254-1258 ◽  
Author(s):  
Guo Liang Hu ◽  
Ai Min Hu ◽  
Ju Xing Liang
Keyword(s):  
Structural Parameters ◽  
Internal Flow ◽  
The Self ◽  
Cross Sectional ◽  
Fluent Software ◽  
Working Principle ◽  
Sectional Shape ◽  
In Fire ◽  
Four Bar Linkage ◽  
Jet Characteristics

Fire water monitor is one of the most commonly used equipments in fire fighting. A liquamatic fire water monitor with self-swinging device was designed. The mechanism of an impeller driving four bar linkage was applied as the self-swinging device. The working principle of the liquamatic fire water monitor was introduced. The internal flow performance was simulated using Fluent software; and the influence rules on jet characteristics were analyzed by changing the cross-sectional shape and diameters of the monitor body, inlet pressure and drive set of the self-swinging device. These analyses led to the optimal structural parameters of flow channel. These simulation results will provide useful theoretical guidance for design of other types of fire water monitor.

scholarly journals Molecular structure of a U•A-U-rich RNA triple helix with 11 consecutive base triples

2020 ◽  
Vol 48 (6) ◽  
pp. 3304-3314 ◽  
Author(s):  
Agnieszka Ruszkowska ◽  
Milosz Ruszkowski ◽  
Jacob P Hulewicz ◽  
Zbigniew Dauter ◽  
Jessica A Brown
Keyword(s):  
Triple Helix ◽  
Double Helix ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Accurate Estimation ◽  
Dna And Rna ◽  
Double Helices ◽  
Starting Point ◽  
Triple Helices ◽  
Rna Triple Helix

Abstract Three-dimensional structures have been solved for several naturally occurring RNA triple helices, although all are limited to six or fewer consecutive base triples, hindering accurate estimation of global and local structural parameters. We present an X-ray crystal structure of a right-handed, U•A-U-rich RNA triple helix with 11 continuous base triples. Due to helical unwinding, the RNA triple helix spans an average of 12 base triples per turn. The double helix portion of the RNA triple helix is more similar to both the helical and base step structural parameters of A′-RNA rather than A-RNA. Its most striking features are its wide and deep major groove, a smaller inclination angle and all three strands favoring a C3′-endo sugar pucker. Despite the presence of a third strand, the diameter of an RNA triple helix remains nearly identical to those of DNA and RNA double helices. Contrary to our previous modeling predictions, this structure demonstrates that an RNA triple helix is not limited in length to six consecutive base triples and that longer RNA triple helices may exist in nature. Our structure provides a starting point to establish structural parameters of the so-called ‘ideal’ RNA triple helix, analogous to A-RNA and B-DNA double helices.

Whole-profile structure solution from powder diffraction data using simulated annealing

2000 ◽  
Vol 33 (3) ◽  
pp. 899-908 ◽  
Author(s):  
A. A. Coelho
Keyword(s):  
Simulated Annealing ◽  
Least Squares ◽  
Structural Parameters ◽  
Real Space ◽  
Penalty Functions ◽  
Asymmetric Unit ◽  
Linear Least Squares ◽  
Space Groups ◽  
Starting Point ◽  
Non Linear

Techniques and methods to facilitate the solution of structures by simulated annealing have been developed from the starting point of a space group and lattice parameters. The simulated-annealing control parameters have been systematically investigated and optimum values characterized and determined. Most significant is the inclusion of electrostatic-potential penalty functions in a non-linear least-squares Rietveld refinement procedure. The long-range electrostatic potentials are calculated using a general real-space summation which can be used for all space groups. In addition, a general weighting scheme for penalty functions negates the need to determine weighting schemes experimentally. Also investigated and improved is the non-linear least-squares minimization procedure used in the refinement of structural parameters. The behaviour and success of the techniques have been tested on X-ray diffraction powder data against the known structures of AlVO4inP1 with 18 atoms in the asymmetric unit, K2HCr2AsO10inP31with 15 atoms in the asymmetric unit excluding hydrogen, and [Co(NH3)5CO3]NO3.H2O inP121with 15 atoms in the asymmetric unit excluding hydrogen.

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