Prediction of Dynamic Stall Onset for Oscillatory Low-Speed Airfoils

2008 ◽  
Vol 130 (10) ◽  
Author(s):  
W. Sheng ◽  
R. A. McD. Galbraith ◽  
F. N. Coton
Keyword(s):  
Measured Data ◽  
Oscillatory Motion ◽  
Dynamic Stall ◽  
The Public ◽  
Common Features ◽  
Reduced Frequency ◽  
Public Data ◽  
The Mean ◽  
Parameter Problem ◽  
Onset Angle

This research presents some common features of oscillatory airfoils, and the method for indicating dynamic stall onset for the unsteady process. Under deep stall conditions, the stall-onset angle in oscillation is independent of the mean angle of the oscillatory motion, and by combining the reduced frequency and the amplitude of the oscillatory motion, the equivalent reduced pitch rate is an analog of this motion to the constant reduced pitch rate of the ramp-up motion. By correlating with the measured data, and with the ramp-up results, the equivalent reduced pitch rate can be defined as a representation for the oscillatory motion. Accordingly, the triple-parameter problem of an oscillation (mean angle, reduced frequency, and amplitude) degrades into the single-parameter problem (equivalent reduced pitch rate). Based on these foundations, an extension of the stall-onset criterion is then made for oscillatory airfoils: a method of extracting the stall-onset parameters directly from oscillatory test data, and an indication of stall onset for the oscillatory airfoils. The results from the new proposed method have shown the consistency with the data of Glasgow University and the public data.

scholarly journals Physics of Dynamic Stall Vortex During Pitching Oscillation of Dynamic Airfoil

2021 ◽  
Author(s):  
Binbin Wei ◽  
Yongwei Gao ◽  
Dong Li
Keyword(s):  
Leading Edge ◽  
Frequency Characteristics ◽  
Dynamic Stall ◽  
Unsteady Pressure ◽  
Reduced Frequency ◽  
Aerodynamic Performances ◽  
The Mean ◽  
Motion Characteristics ◽  
Time Accuracy ◽  
Near Wall

AbstractDynamic stall, which has a significant effect on the aerodynamic performances of dynamic airfoils, is closely related to the physics of the dynamic stall vortex (DSV). The physics of the DSV on the NACA 0012 airfoil was experimentally studied using unsteady pressure measurements with high time accuracy. The experimental Reynolds number was Re = 1.5 × 106, and the reduced frequency was k = 0.069. The propagation of the unsteady pressure field during the dynamic stall process was analyzed in detail. The motion characteristics of the DSV were examined, including its near-wall development characteristics and near-wall evolution velocity. Moreover, the frequency characteristics of the near-wall DSV were studied using wavelet analysis combined with proper orthogonal decomposition (POD) technology. In addition, the effects of the mean angle of attack (AoA) and the amplitude on the DSV motion and frequency characteristics were examined in detail. The effects of the mean AoA on the near-wall DSV strength and the propagation velocity were linear, while the effects of amplitude were nonlinear. The mean AoA and amplitude had a significant influence on the frequency of the leading-edge vortex (LEV) at the initial stage of the DSV development (x/c = 0.10–0.20). This work allows the DSV physics to be understood more deeply. Graphic abstract

scholarly journals A Mathematical Model for the COVID-19 Outbreak and Its Applications

Symmetry ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 990
Author(s):  
Roman Cherniha ◽  
Vasyl’ Davydovych
Keyword(s):  
Mathematical Model ◽  
Exact Solutions ◽  
Quantitative Description ◽  
Measured Data ◽  
Nonlinear Ordinary Differential Equations ◽  
The Novel ◽  
The Public ◽  
Public Data ◽  
Novel Coronavirus ◽  
Good Agreement

A mathematical model based on nonlinear ordinary differential equations is proposed for quantitative description of the outbreak of the novel coronavirus pandemic. The model possesses remarkable properties, such as as full integrability. The comparison with the public data shows that exact solutions of the model (with the correctly specified parameters) lead to the results, which are in good agreement with the measured data in China and Austria. Prediction of the total number of the COVID-19 cases is discussed and examples are presented using the measured data in Austria, France, and Poland. Some generalizations of the model are suggested as well.

Pembangunan Web Service Data Masyarakat Menggunakan REST API dengan Access Token

2018 ◽  
Vol 10 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Muhammad Iqbal Perkasa ◽  
Eko Budi Setiawan
Keyword(s):  
Web Service ◽  
Job Search ◽  
Population Data ◽  
The Public ◽  
Public Data ◽  
Community Data ◽  
The Government ◽  
Rest Api ◽  
Service Application ◽  
Service Data

Data is one of the most important things in this information and information technology era that evolving now. Currently, the government still has not used the public data maximally for administrative purposes. Utilization of this big population data is the creation of a web service application system with REST API where this data will be open and accessible to those who have access. One of the institutions that use this service is the Manpower and Transmigration Service where this system can make the Dinas staff more efficient to create and register job search cards using available community data. This application is able to provide and facilitate many parties, such as data administrators to monitor data usage, registration employee in input data, and people able to register independently. Index Terms—Web service, API, Rest api, People data

How Good Is the Public Data on Sovereign Bond Contracts?

2018 ◽  
Author(s):  
Andrea Kropp ◽  
Gaurang Mitu Gulati ◽  
Mark C. Weidemaier
Keyword(s):  
The Public ◽  
Sovereign Bond ◽  
Public Data

Health Care

2018 ◽  
Author(s):  
Pierre Pestieau ◽  
Mathieu Lefebvre
Keyword(s):  
Health Care ◽  
Technological Progress ◽  
Health Care Systems ◽  
Third Party ◽  
Medical Expenditure ◽  
Public Health Care ◽  
The Public ◽  
Common Features ◽  
Care Systems

This chapter reviews the public health care systems as well as their challenges. It first shows how expenditure on health care has evolved in previous decades and deals with the reasons for the growth observed in almost every European country. It emphasizes the role of technological progress as a main explanatory factor of the increase in medical expenditure but also points to the challenges facing cost-containment policies. Especially, the main common features of health care systems in Europe, such as third-party payment, single provider approach and cost-based reimbursement are discussed. Finally the chapter shows that although inequalities in health exist in the population, health care systems are redistributive. Reforms are thus needed but the trade-off between budgetary efficiency and equity is difficult.

scholarly journals The Problems and Needs of Patients Diagnosed with Cancer and Their Caregivers

2020 ◽  
Vol 18 (1) ◽  
pp. 87
Author(s):  
Anna Lewandowska ◽  
Grzegorz Rudzki ◽  
Tomasz Lewandowski ◽  
Sławomir Rudzki
Keyword(s):  
Cancer Patients ◽  
Medical Information ◽  
Unmet Needs ◽  
Public Healthcare ◽  
Literature Analysis ◽  
The Public ◽  
The Mean ◽  
High Level ◽  
Patients Experience

(1) Background: As the literature analysis shows, cancer patients experience a variety of different needs. Each patient reacts differently to the hardships of the illness. Assessment of needs allows providing more effective support, relevant to every person’s individual experience, and is necessary for setting priorities for resource allocation, for planning and conducting holistic care, i.e., care designed to improve a patient’s quality of life in a significant way. (2) Patients and Methods: A population survey was conducted between 2018 and 2020. Cancer patients, as well as their caregivers, received an invitation to take part in the research, so their problems and needs could be assessed. (3) Results: The study involved 800 patients, 78% women and 22% men. 66% of the subjects were village residents, while 34%—city residents. The mean age of patients was 62 years, SD = 11.8. The patients received proper treatment within the public healthcare. The surveyed group of caregivers was 88% women and 12% men, 36% village residents and 64% city residents. Subjects were averagely 57 years old, SD 7.8. At the time of diagnosis, the subjects most often felt anxiety, despair, depression, feelings of helplessness (46%, 95% CI: 40–48). During illness and treatment, the subjects most often felt fatigued (79%, 95% CI: 70–80). Analysis of needs showed that 93% (95% CI: 89–97) of patients experienced a certain level of need for help in one or more aspects. (4) Conclusions: Patients diagnosed with cancer have a high level of unmet needs, especially in terms of psychological support and medical information. Their caregivers also experience needs and concerns regarding the disease. Caregivers should be made aware of the health consequences of cancer and consider appropriate supportive care for their loved ones.

Addressing common errors and misconceptions in integral calculus with clickers and classroom voting

2019 ◽  
Vol 39 (2) ◽  
pp. 71-85
Author(s):  
Kelly Cline ◽  
Holly Zullo ◽  
David A Huckaby
Keyword(s):  
Correct Answer ◽  
Group Discussion ◽  
Multiple Choice ◽  
Small Group Discussion ◽  
Multiple Choice Questions ◽  
Integral Calculus ◽  
Common Features ◽  
Incorrect Answer ◽  
The Common ◽  
The Mean

Abstract Common student errors and misconceptions can be addressed through the method of classroom voting, in which the instructor presents a multiple-choice question to the class, and after a few minutes for consideration and small-group discussion, each student votes on the correct answer, using a clicker or a phone. If a large number of students have voted for one particular incorrect answer, the instructor can recognize and address the issue. In order to identify multiple-choice questions that are especially effective at provoking common errors and misconceptions, we recorded the percentages of students voting for each option on each question used in 25 sections of integral calculus, taught by 7 instructors, at 4 institutions, over the course of 12 years, on a collection of 172 questions. We restricted our analysis to the 115 questions which were voted on by at least 5 different classes. We present the six questions that caused the largest percentages of students to vote for a particular incorrect answer, discuss how we used these questions in the classroom, and examine the common features of these questions. Further, we look for correlations between question characteristics and the mean percentage of students voting for common errors on these questions, and we find that questions based on general cases have higher percentages of students voting for common errors.

Dynamic Stall Simulation of Flow Over NACA0012 Airfoil at 1 Million Reynolds Number

2015 ◽  
Author(s):  
Venkata Ravishankar Kasibhotla ◽  
Danesh Tafti
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Dynamic Stall ◽  
Sharp Drop ◽  
Airfoil Surface ◽  
Naca0012 Airfoil ◽  
Reduced Frequency ◽  
Edge Vortex

The paper is concerned with the prediction and analysis of dynamic stall of flow past a pitching NACA0012 airfoil at 1 million Reynolds number based on the chord length of the airfoil and at reduced frequency of 0.25 in a three dimensional flow field. The turbulence in the flow field is resolved using large eddy simulations with the dynamic Smagorinsky model at the sub grid scale. The development of dynamic stall vortex, shedding and reattachment as predicted by the present study are discussed in detail. This study has shown that the downstroke phase of the pitching motion is strongly three dimensional and is highly complex, whereas the flow is practically two dimensional during the upstroke. The lift coefficient agrees well with the measurements during the upstroke. However, there are differences during the downstroke. The computed lift coefficient undergoes a sharp drop during the start of the downstroke as the convected leading edge vortex moves away from the airfoil surface. This is followed by a recovery of the lift coefficient with the formation of a secondary trailing edge vortex. While these dynamics are clearly reflected in the predicted lift coefficient, the experimental evolution of lift during the downstroke maintains a fairly smooth and monotonic decrease in the lift coefficient with no lift recovery. The simulations also show that the reattachment process of the stalled airfoil is completed before the start of the upstroke in the subsequent cycle due to the high reduced frequency of the pitching cycle.

Detection and Analysis of Rats’ Bioelectromagnetic Signal

2014 ◽  
Vol 536-537 ◽  
pp. 13-17
Author(s):  
Hong Long Cao ◽  
Fen Ju Qin ◽  
Xue Guan Liu ◽  
He Ming Zhao
Keyword(s):  
Standard Deviation ◽  
Automatic System ◽  
Measurement Method ◽  
Measurement Accuracy ◽  
Biological Activities ◽  
Measurement Data ◽  
Measured Data ◽  
The Mean ◽  
Frequency Window ◽  
Window Effects

In this paper, we designed an automatic system and automatic test software, and they can carry out Kunming rats bioelectromagnetic measurement in standard status and anesthesia automatically in anechoic chamber where the electromagnetic field outside is shielded, the reflection wave is absorbed, and the measurement accuracy will be improved. We get a great number of measurement data with frequency-sweep measurement method. The mean and standard deviation of amplitudes vs. frequencies is calculated and analyzed. The results show the measurement method is feasible. We have plotted the means of measured data as multiple sets of Y values in a series of bars with standard deviations bars included and distributed in the frequency axis of X. It is found that the fluctuation of the mean and standard deviation in some frequencies is not evident which may explain frequency window effects, while in other frequencies, such a fluctuation can be obviously observed, which may suggest that bioelectromagnetic signal is influenced by biological activities (standard and anaesthesia status) in these frequency points.

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