COMPARISON OF DIFFERENT EXPERIMENTAL DESIGNS, SAMPLE SIZES AND TECHNIQUES APPLIED TO METAMODELING THE INDUCED DRAG COEFFICIENT OF A BOX-WING AIRCRAFT

2018 ◽  
Author(s):  
Luiz Fernando Tibério Fernandez ◽  
Guilherme Barufaldi ◽  
Adson De Paula ◽  
Luiz Carlos Sandoval
Keyword(s):  
Drag Coefficient ◽  
Experimental Designs ◽  
Sample Sizes ◽  
Induced Drag

scholarly journals Sample Size Determination and Optimal Design of Simple Pretest-Posttest Experimental Designs: Introduction, Software, and Illustrations

2021 ◽  
Author(s):  
Metin Bulus
Keyword(s):  
Optimal Design ◽  
Sample Size ◽  
Small Sample ◽  
Experimental Designs ◽  
Sample Size Determination ◽  
Size Determination ◽  
Sample Sizes ◽  
Control Groups ◽  
Small Sample Sizes ◽  
And Control

A recent systematic review of experimental studies conducted in Turkey between 2010 and 2020 reported that small sample sizes had been a significant drawback (Bulus and Koyuncu, 2021). A small chunk of the studies were small-scale true experiments (subjects randomized into the treatment and control groups). The remaining studies consisted of quasi-experiments (subjects in treatment and control groups were matched on pretest or other covariates) and weak experiments (neither randomized nor matched but had the control group). They had an average sample size below 70 for different domains and outcomes. These small sample sizes imply a strong (and perhaps erroneous) assumption about the minimum relevant effect size (MRES) of intervention before an experiment is conducted; that is, a standardized intervention effect of Cohen’s d < 0.50 is not relevant to education policy or practice. Thus, an introduction to sample size determination for pretest-posttest simple experimental designs is warranted. This study describes nuts and bolts of sample size determination, derives expressions for optimal design under differential cost per treatment and control units, provide convenient tables to guide sample size decisions for MRES values between 0.20 ≤ Cohen’s d ≤ 0.50, and describe the relevant software along with illustrations.

Experimental investigation on the structures and induced drag of wingtip vortices for different wingtip configurations

2020 ◽  
pp. 095441002094791
Author(s):  
Ze-Peng Cheng ◽  
Yang Xiang ◽  
Hong Liu
Keyword(s):  
Growth Rate ◽  
Form Factor ◽  
Drag Coefficient ◽  
Particle Image ◽  
Vortex Center ◽  
Streamwise Location ◽  
Induced Drag ◽  
Wingtip Vortex ◽  
Image Velocimetry ◽  
Drag And Lift

As an effective method to reduce induced drag and the risk of wake encounter, the winglet has been an essential device and developed into diverse configurations. However, the structures and induced drag, as well as wandering features of the wingtip vortices ( WTVs) generated by these diverse winglet configurations are not well understood. Thus, the WTVs generated by four typical wingtip configurations, namely the rectangular wing with blended/raked/split winglet and without winglet (Model BL/ RA/ SP/NO for short), are investigated in this paper using particle image velocimetry technology. Comparing with an isolated primary wingtip vortex generated by Model NO, multiple vortices are twisted coherently after installing the winglets. In addition, the circulation evolution of WTVs demonstrates that the circulation for Model SP is the largest, while Model RA is the smallest. By tracking the instantaneous vortex center, the vortex wandering behavior is observed. The growth rate of wandering amplitude along with the streamwise location from the quickest to the slowest corresponds to Model SP, Model NO, Model BL, Model RA in sequence, implying that the WTVs generated by model SP exhibit the quickest mitigation. Considering that the induced drag scales as the lift to power 2, the induced drag and lift are estimated based on the wake integration method, and then the form factor λ, defined by [Formula: see text], is calculated to evaluate the aerodynamic performance. Comparing with the result of Model NO, the form factor decreases by 7.99%, 4.80%, and 2.60% for Model RA, Model BL, Model SP, respectively. In sum, Model RA and BL have a smaller induced drag coefficient but decay slower; while Model SP has a larger induced drag coefficient but decays quicker. An important implication of these results is that reducing the strength of WTVs and increasing the growth rate of vortex wandering amplitude can be the mutual requirements for designing new winglets.

A Note on the Induced Drag of Jet-Flapped Wings

1960 ◽  
Vol 64 (593) ◽  
pp. 290-291
Author(s):  
G. K. Korbacher ◽  
K. Sridhar
Keyword(s):  
Aspect Ratio ◽  
Drag Coefficient ◽  
Apparent Discrepancy ◽  
General Flow ◽  
Induced Drag ◽  
Jet Blowing

The main purpose of this note is to explain the apparent discrepancy which arises when the change in effective aspect ratio due to blowing, as predicted by the theoretically derived expression for the induced drag coefficient, is compared with what one intuitively expects from the general flow picture. If the jet sheet is considered as a chordwise extension of the wing (mechanical flap analogy), the general flow picture suggests that the effective aspect ratio of a wing without blowing is reduced by blowing. Maskell and Spence's relation for the induced drag coefficient, however, indicates that the effect of jet blowing is to increase the effective aspect ratio.

scholarly journals The estimation of applicability concerning the methods for calculation of asimple wing with wingtips inductive resistance during the flight near the earth surface

2020 ◽  
pp. 58-69
Author(s):  
Andrey N. Luchkov ◽  
Evgeny V. Zhuravlev ◽  
Egor Y. Cheban
Keyword(s):  
Drag Coefficient ◽  
Earth Surface ◽  
Drag Coefficients ◽  
End Plate ◽  
Induced Drag ◽  
The Earth ◽  
Wing Profile

One of the problems in the hovercrafts design is to dtermine the aerodynamic charactreistics of the wing near the earth surface. In this article, 4 methods for calculating the induced drag coefficient Cxi of a simple airfoil with an end plate at different relative heights were considered. Four methods of induced drag coefficient determination were considered for different relative flight’s heights. Calculations were performed according to the Phillips, Wieselsberge, Panchenkov-Surzhik, Mantle methods for the TsAGI-876 wing profile. The calculated values of induced drag coefficients were compared with the experimental wind tunnel’s data at the Central Aerohydrodynamic Institute.

scholarly journals Control of Gliding Angle in RÜppell'S Griffon Vulture Gyps RÜppellii

1971 ◽  
Vol 55 (1) ◽  
pp. 39-46 ◽  
Author(s):  
C. J. PENNYCUICK
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
The Body ◽  
Sectional Area ◽  
Wing Area ◽  
Cross Sectional ◽  
Griffon Vulture ◽  
Speed Increase ◽  
Induced Drag ◽  
Low Speeds

1. The drag of the frozen, wingless body of a Rüppell's griffon vulture was measured in a wind tunnel with a simple drag balance. The drag coefficient with feet and neck retracted was 0.43, based on the greatest cross-sectional area of the body. 2. The drag of the body was trebled by fully lowering the feet, and more than quadrupled when the tail was lowered as well, apparently owing to separation of the flow over the back. The drag coefficient of the legs and feet, based on their frontal area, varied from 0.89 to 1.08 in different positions. 3. At low speeds the use of the feet alone should reduce the glide ratio from about 15 to 10, but the airbrake effect becomes progressively more marked at higher speeds. At lower speeds reduction of the wing area produces a greater steepening of the gliding angle, but at the expense of increasing the minimum speed. Increase of induced drag would provide a highly effective gliding angle control at very low speeds, and it is suggested that this is achieved by raising the secondary feathers, which would alter the spanwise lift distribution by transferring a greater proportion of the lift to the primaries.

Gliding Flight of the Andean Condor in Nature

1973 ◽  
Vol 58 (1) ◽  
pp. 225-237
Author(s):  
JERRY McGAHAN
Keyword(s):  
Drag Coefficient ◽  
Field Data ◽  
Lift Coefficient ◽  
Vertical Component ◽  
Induced Drag ◽  
Gliding Flight ◽  
Black Vulture ◽  
Air Speed ◽  
Andean Condor ◽  
Turkey Vultures

1. Derived in a vector analysis with measurements of wind velocity and ground velocity of the bird, the following mean air speeds were obtained for birds crossing a Peruvian beach: 15 m/sec for 15 gliding Andean condors, 14 m/sec for 42 condors that flapped during the crossing, and 10 m/sec for five turkey vultures that flapped. For the 15 gliding condors a mean lift coefficient of 0.7 and a mean induced drag force of 3 N were computed. 2. Implausibly low values derived for parasite drag coefficient of the condor appeared to be due to (a) unmeasured forces of deceleration and (b) an undetected vertical component of the wind at the level of the flight path. Field data, adjusted by introducing a coefficient of parasite drag determined for the black vulture in a windtunnel study provided corrected estimates of drag. I secured an adjusted value of 14 for the L/D ratio of a condor gliding with wings fully extended. 3. A moderate flexion of the wings reducing the span by 20% is estimated to increase the optimum air speed from 13.9 to 15.2 m/sec for an adult male condor and from 12.6 to 13.8 m/sec for an adult female.

Interference Drag of a Turbulent Junction Vortex

1990 ◽  
Vol 112 (4) ◽  
pp. 441-446 ◽  
Author(s):  
F. J. Pierce ◽  
S. K. Nath
Keyword(s):  
Drag Coefficient ◽  
Flat Plate ◽  
Vortex Flow ◽  
Control Volume ◽  
Cylindrical Body ◽  
Quality Data ◽  
High Quality Data ◽  
Pressure Losses ◽  
Induced Drag ◽  
Control Volume Approach

The interference drag identified with the junction of a streamlined cylindrical body and a flat plate was investigated. The junction drag was calculated from a set of detailed, self consistent, high quality data using a control volume approach. The drag for the isolated flat plate and streamlined cylinder making up the junction was calculated using boundary-layer solvers together with surface pressure measurements. For the particular and relatively thick body under consideration, the results show a significant increase in drag due to the junction. These and other available results indicate that the interference drag has a systematic dependence on the thickness to chord ratio. The junction vortex wake increases the downstream flat plate drag significantly. Because of this effect, a unique value for the drag force, drag coefficient, or induced drag coefficient for a junction vortex flow would require that the geometry be specified in detail. The induced drag and the total pressure losses identified with the junction are also reported.

SOCIAL PHOBIA: COMMENTS ON THE VIABILITY AND VALIDITY OF AN ANALOGUE RESEARCH STRATEGY AND BRITISH NORMS FOR THE FEAR OF NEGATIVE EVALUATION QUESTIONNAIRE

2001 ◽  
Vol 29 (4) ◽  
pp. 423-430 ◽  
Author(s):  
Lusia Stopa ◽  
David M. Clark
Keyword(s):  
Social Phobia ◽  
Research Design ◽  
North American ◽  
Research Strategy ◽  
Negative Evaluation ◽  
Fear Of Negative Evaluation ◽  
Experimental Designs ◽  
Sample Sizes ◽  
Evaluation Questionnaire ◽  
Analogue Research

This paper discusses the viability of an analogue research design for studying key processes in social phobia by comparing individuals who score high and low on the Fear of Negative Evaluation Scale (FNE: Watson & Friend, 1969). Research indicates remarkable consistency in the processes that distinguish patients with social phobia from controls and high FNE volunteers from low FNE volunteers. Unfortunately, all existing FNE norms are based on North American populations. The present paper presents British student norms and suggests possible cut-off points for defining groups for analogue research. Advantages of the analogue strategy include rapid piloting of new paradigms and the use of more complex experimental designs that require substantial sample sizes. Limitations of analogue research are also highlighted.

scholarly journals Optimal Sample Sizes in Experimental Designs With Individuals Nested Within Clusters

2003 ◽  
Vol 2 (3) ◽  
pp. 151-175 ◽  
Author(s):  
Mirjam Moerbeek ◽  
Gerard J. P. Van Breukelen ◽  
Martijn P. F. Berger ◽  
Marlein Ausems Marlein Ausems
Keyword(s):  
Experimental Designs ◽  
Sample Sizes ◽  
Optimal Sample

scholarly journals Can social robots help children in healthcare contexts? A scoping review

2019 ◽  
Vol 3 (1) ◽  
pp. e000371 ◽  
Author(s):  
Julia Dawe ◽  
Craig Sutherland ◽  
Alex Barco ◽  
Elizabeth Broadbent
Keyword(s):  
Conference Proceedings ◽  
Scoping Review ◽  
Controlled Trial ◽  
Feasibility Studies ◽  
Health Condition ◽  
Social Robots ◽  
Small Sample ◽  
Experimental Designs ◽  
Sample Sizes ◽  
Eligibility Criteria

ObjectiveTo review research on social robots to help children in healthcare contexts in order to describe the current state of the literature and explore future directions for research and practice.DesignScoping review.Data sourcesEngineering Village, IEEE Xplore, Medline, PsycINFO and Scopus databases were searched up until 10 July 2017. Only publications written in English were considered. Identified publications were initially screened by title and abstract, and the full texts of remaining publications were then subsequently screened.Eligibility criteriaPublications were included if they were journal articles, conference proceedings or conference proceedings published as monographs that described the conceptualisation, development, testing or evaluation of social robots for use with children with any mental or physical health condition or disability. Publications on autism exclusively, robots for use with children without identified health conditions, physically assistive or mechanical robots, non-physical hardware robots and surgical robots were excluded.ResultsSeventy-three publications were included in the review, of which 50 included user studies with a range of samples. Most were feasibility studies with small sample sizes, suggesting that the robots were generally accepted. At least 26 different robots were used, with many of these still in development. The most commonly used robot was NAO. The evidence quality was low, with only one randomised controlled trial and a limited number of experimental designs.ConclusionsSocial robots hold significant promise and potential to help children in healthcare contexts, but higher quality research is required with experimental designs and larger sample sizes.

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