A simple and conservative unstructured sliding-mesh approach for rotor–fuselage aerodynamic interaction simulation

2016 ◽  
Vol 231 (1) ◽  
pp. 163-179 ◽  
Author(s):  
He-Yong Xu ◽  
Shi-Long Xing ◽  
Zheng-Yin Ye ◽  
Ming-Sheng Ma
Keyword(s):  
Interaction Model ◽  
Side Surface ◽  
Computational Domain ◽  
Sliding Mesh ◽  
Sliding Interface ◽  
Stationary Zone ◽  
Aerodynamic Interaction ◽  
On Line ◽  
Interaction Simulation ◽  
Institute Of Technology

A conservative unstructured sliding-mesh technique is developed for the rotor–fuselage aerodynamic interaction simulation. The computational domain is decomposed into a rotational zone and a stationary zone. The rotational zone contains the rotor blades that rotate with the zone, while the stationary zone contains the fuselage which keeps stationary during the simulation. The two zones are connected via a sliding interface, which is designed to be a cylindrical surface consisting of the top, bottom, and side surfaces. The top and bottom surfaces are paved with arbitrary triangles and the side surface is meshed by triangularizing equal-sized and right-angled quadrilaterals. The intersection information between the rotational and stationary sliding interface meshes, such as the number of intersection triangles and the area of each intersection polygon, is the key to the present conservative computation. For the top and bottom surfaces, the point-on-line cases are first identified and the point perturbation operation is carried out to eliminate the potential error due to the presence of a point-on-line case. The neighbor-to-neighbor searching algorithm is applied for efficient determination of the intersection triangles, and the intersection polygon areas are determined by enumerating all the possible intersection cases. For the side surface, the intersection relations and polygon areas can be easily determined based on the enumeration method due to the special triangularization. The present method is validated by simulating the GIT (Georgia Institute of Technology) rotor–fuselage interaction model, and comparing numerical results with experiment measurements. It is demonstrated that the present conservative sliding-mesh method is simple to implement, and is efficient for the prediction of complicated unsteady rotor–fuselage aerodynamic interaction.

scholarly journals Teaching Midwifery Face-to-Face or Via the Screen: The Impact of Flexible Delivery of Teaching on Student Engagement

2021 ◽  
Author(s):  
◽  
Tania Dawn Milne
Keyword(s):  
New Zealand ◽  
Student Engagement ◽  
Video Conferencing ◽  
Face To Face ◽  
New Curriculum ◽  
On Line ◽  
Flexible Delivery ◽  
Institute Of Technology ◽  
Quality Learning ◽  
The Impact

<p>The aim of this research was to describe how undergraduate midwifery students’ engagement with learning is impacted when they have teaching delivered by different methods of instruction. It asks the question: does flexible delivery of teaching impact on their ability to engage in their learning? This research describes the impact of different modes of flexible delivery of teaching within a new curriculum on students in a pre-registration midwifery undergraduate programme at Waikato Institute of Technology (Wintec), New Zealand. This new curriculum commenced in 2010 as a response to legislative and industry driven changes to midwifery education in New Zealand. The research used an on-line survey to ask students enrolled in years one and two of the programme and those who had exited the programme during the same timeframe, A range of questions about their learning experiences. Surveys were sent to 104 enrolled students and 15 students that had exited the BMid programme. Fifty two (50%) responses were received from the enrolled students and three (20%) from those that had exited the programme. There were three key findings of this research. Firstly the participants identified differences with their sense of belonging amongst their peers, tutors and the administration team outside of their regional learning hubs. The second key and unsurprising finding was that respondents across the board preferred face-to-face sessions to video conferencing sessions and thirdly that the demographic profile of the respondents from the regional learning hubs was different to those attending from the Hamilton city hub. The implications of these key findings are; · For tertiary institutions to acknowledge and consider the links between high quality learning, student engagement and outcomes. · To support the need for continuing training and education for both faculty and students with regards to flexible delivery of teaching and to provide professional development and relevant technology to support more interactive forms of learning if delivered via video conferencing or by online activities. · To further research the needs of Māori students and those who have exited the programme in order to discover what would need to change in order for them to continue with their studies.</p>

Modelling of the Toothed Gear Operations with the Application of the Analysis of the Gear Sliding Mesh Velocity Changes

2011 ◽  
Vol 180 ◽  
pp. 200-206 ◽  
Author(s):  
Jacek Dziurdź
Keyword(s):  
Diagnostic Methods ◽  
Actual Problem ◽  
Driving System ◽  
Sliding Mesh ◽  
Vibroacoustic Diagnostics ◽  
On Line ◽  
Velocity Changes ◽  
Harmonic Components ◽  
Toothed Gears ◽  
Vibroacoustic Signals

Searching for effective diagnostic methods of basic elements of driving systems is still the actual problem. The most often the vibroacoustic diagnostics based on the analysis of vibrations and noises generated by the working system is applied. Driving systems of vehicles are rather complicated. They consist, among others, of various types of toothed gears. Within the vibroacoustic signals recorded during their operation not only harmonic components – being the effect of these gears operations - are present, but also components generated by other elements. Due to this, there is a necessity of the development of models of the vibroacoustic signals generation by the main elements of the driving system. Such models will allow to identify – within the recorded signals – the harmonic components related to processes occurring during the gear operation. These models should be relatively simple due to the possibility of their application in diagnostic devices operating in the ‘on line’ mode. Modelling of the single-stage toothed gear, with the application of the analysis of the gear sliding mesh velocity changes, is presented in the hereby paper.

Gas Turbine Temperature Prediction Using Unsteady CFD and Realistic Non-Uniform 2D Combustor Exit Properties

2008 ◽  
Author(s):  
Fre´de´ric N. Felten ◽  
Semir Kapetanovic ◽  
D. Graham Holmes ◽  
Michael Ostrowski
Keyword(s):  
Boundary Conditions ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Computational Cost ◽  
Computational Domain ◽  
Two Dimensional ◽  
Gas Temperature ◽  
Sliding Mesh ◽  
Flow Gradients ◽  
The Impact

Typical Computational Fluid Dynamics (CFD) studies performed on High Pressure Turbines (HPT) do not include the combustor domain in their analyses. Boundary conditions from the combustor exit have to be prescribed at the inlet of the computational domain for the first HPT nozzle. It is desirable to include the effect of combustor non-uniformities and flow gradients in order to enhance the accuracy of the aerodynamics and heat transfer predictions on the nozzle guide vanes and downstream turbine blades. The present work is the continuation of steady and quasi-unsteady studies performed previously by the authors. A fully unsteady nonlinear approach, also referred to as sliding mesh, is now used to investigate a first HPT stage and the impact of realistic non-uniformities and flow gradients found along the exit plane of a gas turbine combustor. Two Turbine Inlet Boundary Conditions (TIBC) are investigated. Simulations using a two-dimensional TIBC dependant on both the radial and circumferential directions are performed and compared to baseline analyses, where the previous two-dimensional TIBC is circumferentially averaged in order to generate inlet boundary conditions dependant only on the radial direction. The two elements included in the present work, combustor pitchwise non-uniformities and full unsteady blade row interactions are shown to: (1) alter the gas temperature profile predictions up to ±5%; (2) modify the surface temperature predictions by ±8% near the trailing edge of the vane suction side; (3) increase the overall pressure losses by roughly 1%, and (4) modified the ingestion behavior of the purge cavity flow. In addition, keeping in mind the tradeoff between improved predictions and computational cost, the use of an unsteady sliding mesh formulation, instead of a quasiunsteady frozen gust, reveals the importance of the two-way unsteady coupling between adjacent blade rows for temperature and pressure predictions.

scholarly journals Automatic Modeling of Frequent Behaviors of Avatars and Players in a On Line Game

2011 ◽  
Vol 10 (1) ◽  
pp. 5-11
Author(s):  
Chih-Ming Chiu ◽  
Shao-Shin Hung ◽  
Jyh-Jong Tsay
Keyword(s):  
Data Stream ◽  
Behavior Pattern ◽  
Interaction Model ◽  
Limited Resources ◽  
Good Prediction ◽  
Future Prediction ◽  
On Line ◽  
Data Extracting ◽  
Interesting Behavior ◽  
Processing Period

Millions of people now participate in on line games, placing tremendous and often unpredictable maintenance burdens on their operators. Thus, understanding the dynamic behaviors of a player is critical for the systems, network, and designers. To the best of our knowledge, little work builds character interaction model based on the data stream mining. This work improves our understanding the behaviors of avatar/player in a on line game by collecting the behavior data, extracting frequent behavior patterns, learning the hidden hints and making good prediction on responses to the unexpected impacts. Besides, we develop two efficient approaches for mining the behavior data to find the interesting behavior pattern for future prediction on responses of opponents. Our novel findings include the following: One, due to the constraints of limited resources of time, memory, and sample size, MSS-MB was proposed to meet these conditions; the other, due to the constraints of real-time and on-line, there may have some errors occurred in the processing period, MSS-BE was proposed to control the errors as needed. Finally, based on the experimental results, we can predict the responses of opponents efficiently in the on line game.

scholarly journals Teaching Midwifery Face-to-Face or Via the Screen: The Impact of Flexible Delivery of Teaching on Student Engagement

2021 ◽  
Author(s):  
◽  
Tania Dawn Milne
Keyword(s):  
New Zealand ◽  
Student Engagement ◽  
Video Conferencing ◽  
Face To Face ◽  
New Curriculum ◽  
On Line ◽  
Flexible Delivery ◽  
Institute Of Technology ◽  
Quality Learning ◽  
The Impact

<p>The aim of this research was to describe how undergraduate midwifery students’ engagement with learning is impacted when they have teaching delivered by different methods of instruction. It asks the question: does flexible delivery of teaching impact on their ability to engage in their learning? This research describes the impact of different modes of flexible delivery of teaching within a new curriculum on students in a pre-registration midwifery undergraduate programme at Waikato Institute of Technology (Wintec), New Zealand. This new curriculum commenced in 2010 as a response to legislative and industry driven changes to midwifery education in New Zealand. The research used an on-line survey to ask students enrolled in years one and two of the programme and those who had exited the programme during the same timeframe, A range of questions about their learning experiences. Surveys were sent to 104 enrolled students and 15 students that had exited the BMid programme. Fifty two (50%) responses were received from the enrolled students and three (20%) from those that had exited the programme. There were three key findings of this research. Firstly the participants identified differences with their sense of belonging amongst their peers, tutors and the administration team outside of their regional learning hubs. The second key and unsurprising finding was that respondents across the board preferred face-to-face sessions to video conferencing sessions and thirdly that the demographic profile of the respondents from the regional learning hubs was different to those attending from the Hamilton city hub. The implications of these key findings are; · For tertiary institutions to acknowledge and consider the links between high quality learning, student engagement and outcomes. · To support the need for continuing training and education for both faculty and students with regards to flexible delivery of teaching and to provide professional development and relevant technology to support more interactive forms of learning if delivered via video conferencing or by online activities. · To further research the needs of Māori students and those who have exited the programme in order to discover what would need to change in order for them to continue with their studies.</p>

scholarly journals Suppression mechanism study of attached apex drogue on undesirable inflation phenomena

2018 ◽  
Vol 69 (02) ◽  
pp. 128-132
Author(s):  
LI JUN ◽  
CHENG HAN ◽  
YANG JING
Keyword(s):  
Interaction Model ◽  
Computational Domain ◽  
Analysis Model ◽  
Mechanism Study ◽  
Deformation Method ◽  
Explicit Finite Element ◽  
Suppression Effect ◽  
Contact Algorithm ◽  
Structure Interaction ◽  
Suppression Mechanism

At present, the studies of suppression effect of attached apex drogue on undesirable inflation were seriously dependent on experiments. The experiments were difficult to reveal the suppression mechanism due to the difficulty of data collection. In this paper, a FSI (Fluid Structure Interaction) model based on explicit finite element method was proposed to study the suppression mechanism. The graphical deformation method was used to realize the movement of computational domain. At the same time, the velocity conditions were applied on the boundaries of computational domain, which was used to simulate the external wind field. The coupling between the fluid and structure described by Lagrangian meshes was realized by contact algorithm. Finally, an extra-large parachute was taken as the research object, and the suppression mechanism of attached apex drogue was analyzed according to the numerical results. The effect of different attached apex drogues with different resistance characteristics also was analyzed by the above FSI model. The analysis model and method proposed in this paper could provide the design basis of extra-large parachute.

scholarly journals Transition in an infinite swept-wing boundary layer subject to surface roughness and free-stream turbulence

2021 ◽  
Vol 931 ◽  
Author(s):  
Luca De Vincentiis ◽  
Dan S. Henningson ◽  
Ardeshir Hanifi
Keyword(s):  
Boundary Layer ◽  
Free Stream ◽  
Flow Instability ◽  
Transition To Turbulence ◽  
Computational Domain ◽  
Swept Wing ◽  
Free Stream Turbulence ◽  
Roughness Elements ◽  
Layer Flow ◽  
Institute Of Technology

The instability of an incompressible boundary-layer flow over an infinite swept wing in the presence of disc-type roughness elements and free-stream turbulence (FST) has been investigated by means of direct numerical simulations. Our study corresponds to the experiments by Örlü et al. (Tech. Rep., KTH Royal Institute of Technology, 2021, http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291874). Here, different dimensions of the roughness elements and levels of FST have been considered. The aim of the present work is to investigate the experimentally observed sensitivity of the transition to the FST intensity. In the absence of FST, flow behind the roughness elements with a height above a certain value immediately undergoes transition to turbulence. Impulse–response analyses of the steady flow have been performed to identify the mechanism behind the observed flow instability. For subcritical roughness, the generated wave packet experiences a weak transient growth behind the roughness and then its amplitude decays as it is advected out of the computational domain. In the supercritical case, in which the flow transitions to turbulence, flow as expected exhibits an absolute instability. The presence of FST is found to have a significant impact on the transition behind the roughness, in particular in the case of a subcritical roughness height. For a height corresponding to a roughness Reynolds number $Re_{hh}=461$ , in the absence of FST the flow reaches a steady laminar state, while a very low FST intensity of $Tu =0.03\,\%$ causes the appearance of turbulence spots in the wake of the roughness. These randomly generated spots are advected out of the computational domain. For a higher FST level of $Tu=0.3\,\%$ , a turbulent wake is clearly visible behind the element, similar to that for the globally unstable case. The presented results confirm the experimental observations and explain the mechanisms behind the observed laminar–turbulent transition and its sensitivity to FST.

scholarly journals Reconceptualising the Role of the Visiting Lecturer: Using Educational Technology to Enable Practicum Placements In The ‘New Normal’

2021 ◽  
Vol 3 (1) ◽  
pp. 21
Author(s):  
Sarah Probine ◽  
Jo Perry
Keyword(s):  
Cell Phone ◽  
Traditional Model ◽  
Practice Setting ◽  
New Normal ◽  
On Line ◽  
Communication Software ◽  
Virtual Meetings ◽  
Institute Of Technology ◽  
Survey Responses

The international pandemic and the national lockdown during semester one of 2020 meant the Manukau Institute of Technology Early Childhood teams needed to revisit the existing requirements of their programmes and particularly in terms of practicum. In response, the teams developed ‘virtual’ meetings to replace the usual observation visit by a visiting lecturer. In this revised approach, the students and lecturers engaged in weekly conversations and in these meetings the role of the Visiting Lecturer was significantly changed.  By using communication software (Microsoft Teams with cell phone back up) the student and Visiting Lecturer engaged in critically reflective conversations that mentored the student in thinking about their practice, setting goals to work on and articulating their learning.  By using the software in this way, the Visiting Lecturers changed their role from merely assessor of practice to firstly, mentor and guide.  In the online triadic meetings (also using Microsoft Teams and cell phone back-up) it became clear that the traditional model of the student being told how the assessor felt they had met the practicum criteria was replaced with one where the student was able to articulate for themselves.  At the end of the semester, students and lecturers were invited to give feedback via a survey. The responses focused on the deep learning experienced, ownership of learning, and the confidence the students felt at the on-line triadic. Much more unexpected was the correlation between survey responses and much of the literature. Drawing on these findings, this presentation poses some possibilities for what both the practicum and a reconceptualised relationship between visiting lecturer, associate teacher and students could look like in the ‘new normal’. 

scholarly journals Self-Selection Bias In On-Line Accounting Courses: Student Characteristics

2011 ◽  
Vol 1 (8) ◽  
Author(s):  
Thomas T. Amlie
Keyword(s):  
New York ◽  
Faculty Member ◽  
Selection Bias ◽  
A Priori ◽  
Work Load ◽  
Font Size ◽  
Self Selection ◽  
Ex Post ◽  
On Line ◽  
Institute Of Technology

<p class="MsoNormal" style="text-align: justify; margin: 0in 0.5in 0pt; mso-pagination: none;"><span style="font-size: 10pt;"><span style="font-family: Times New Roman;">Over the past several years one of my responsibilities as a faculty member of the State University of New York Institute of Technology has been to teach both graduate and undergraduate classes over the internet via the SUNY Learning Network (SLN).<span style="mso-spacerun: yes;">&nbsp; </span>Although the work load for a faculty member teaching an on-line course can be substantial, there is evidence that there are unexpected rewards in terms of the caliber of the students who takes such courses.<span style="mso-spacerun: yes;">&nbsp; </span>Although the characteristics of the students comprising the initial enrollment of the class mirror those of standard &ldquo;in-person&rdquo; classes, there seems to be substantial initial attrition among those students who are less motivated to devote the necessary time to the study of the material.<span style="mso-spacerun: yes;">&nbsp; </span>Additionally, the additional responsibility for &ldquo;active learning&rdquo; on the part of students appears to motivate many students to a higher level of effort.</span></span></p><p class="MsoNormal" style="text-align: justify; margin: 0in 0.5in 0pt; mso-pagination: none;"><span style="font-size: 10pt;"><span style="font-family: Times New Roman;">&nbsp;</span></span></p><p class="MsoNormal" style="text-align: justify; margin: 0in 0.5in 0pt; mso-pagination: none;"><span style="font-size: 10pt;"><span style="font-family: Times New Roman;">This paper provides evidence via ex-post and a-priori surveys, as well as through an analysis of the students&rsquo; final grades, that there is a self-selection bias among students that can lead to an overall increase in the caliber of the on-line class relative to the conventional on-campus class.</span></span></p>

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