On self-similar behaviour of the hysteresis loops in pitching motions

2004 ◽  
Vol 108 (1086) ◽  
pp. 427-434 ◽  
Author(s):  
M. R. Soltani ◽  
A. R. Davari
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Wind Tunnel ◽  
Standard Model ◽  
Hysteresis Loops ◽  
Similarity Parameter ◽  
Pitching Motion ◽  
Wind Tunnel Tests ◽  
Unsteady Aerodynamic ◽  
Self Similar

AbstractA new similarity parameter has been used for analyzing the unsteady aerodynamic behaviour of vehicles undergoing sinusoidal pitching motion. If this parameter is identical for two unsteady manoeuvres with different reduced frequencies and oscillation amplitudes, the corresponding hysteresis loops of the force and moment collapse on each other. To support and verify this, extensive unsteady wind tunnel tests have been conducted on a standard model, which is a well known fighter type configuration. The acquired data were used to train a certain type of neural network, called the Generalised Regression Neural Network (GRNN), to reduce the number of wind tunnel runs. The scheme, once proved to give the correct results for various conditions, was applied to extend the experimental data to other conditions that have not been tested in the tunnel. Both the predicted and acquired tunnel data were used to show the performance of the similarity parameter.

Validation of the AeroDyn Subroutines Using NREL Unsteady Aerodynamics Experiment Data

2002 ◽  
Author(s):  
David J. Laino ◽  
A. Craig Hansen ◽  
Jeff E. Minnema
Keyword(s):  
Wind Tunnel ◽  
Test Data ◽  
Complex Dynamics ◽  
Angle Of Attack ◽  
Unsteady Aerodynamics ◽  
Hysteresis Loops ◽  
Structural Vibration ◽  
Detailed Knowledge ◽  
Vibration Modes ◽  
Wind Tunnel Tests

Completion of the full-scale wind tunnel tests of the NREL Unsteady Aerodynamics Experiment (UAE) Phase VI allowed validation of the AeroDyn wind tuxbine aerodynamics software to commence. Detailed knowledge of the inflow to the UAE was the bane of prior attempts to accomplish any in-depth validation in the past. The wind tunnel tests permitted unprecedented control and measurement of inflow to the UAE rotor. The data collected from these UAE tests are currently under investigation as part of an effort to better understand wind turbine rotor aerodynamics in order to improve aero-elastic modeling techniques. Preliminary results from this study using the AeroDyn subroutines are presented, pointing to several avenues toward improvement. Test data indicate that rotational effects cause more static stall delay over a larger portion of the blades than predicted by current methods. Despite the relatively stiff properties of the UAE, vibration modes appear to influence the aerodynamic forces and system loads. AeroDyn adequately predicts dynamic stall hysteresis loops when appropriate steady, 2-D airfoil tables are used. Problems encountered include uncertainties in converting measured inflow angle to angle of attack for the UAE phase VI. Future work is proposed to address this angle of attack problem and to analyze a slightly more complex dynamics model that incorporates some of the structural vibration modes evident in the test data.

An investigation of lateral-directional departure behavior based on yawing–rolling coupled wind tunnel tests

2017 ◽  
Vol 232 (16) ◽  
pp. 2989-3000
Author(s):  
Lin Shen ◽  
Da Huang ◽  
Genxing Wu
Keyword(s):  
Wind Tunnel ◽  
Aerodynamic Characteristics ◽  
Flight Simulation ◽  
Wind Tunnel Tests ◽  
Unsteady Aerodynamic ◽  
Model Based ◽  
Aerodynamic Model ◽  
Data Prediction ◽  
Text Model ◽  
Departure Behavior

The traditional aerodynamic model based on the dynamic derivative tests and the [Formula: see text] model based on the yawing–rolling coupled motion tests are compared with respect to aerodynamic data, prediction of lateral-directional departure, and flight simulation. The study shows that the traditional model cannot fully reveal the unsteady aerodynamic characteristics and predict completely the departure behavior due to yaw–roll coupling. On the other hand, the [Formula: see text] model can reveal the departure behavior of an aircraft at some specific coupling ratios when the angle of attack reaches a critical value or more, using the aerodynamic data obtained from the yawing–rolling coupled wind tunnel tests. The comparison of flight simulation results shows that the lateral-directional departure is closely related to the coupling ratios, and for the investigated aircraft, the departure is mainly caused by the unsteady yawing and rolling moments at the coupling ratios showing unstable features.

Performance of Galloping Piezoelectric Energy Harvesters With Square Bluff Body

2013 ◽  
Author(s):  
Felix Ewere ◽  
Gang Wang
Keyword(s):  
Experimental Data ◽  
Wind Tunnel ◽  
Mechanical Model ◽  
Bluff Body ◽  
Energy Harvester ◽  
Approximate Solutions ◽  
Wind Tunnel Tests ◽  
Energy Harvesters ◽  
Piezoelectric Energy ◽  
Physical Insight

In this paper, we investigate a galloping piezoelectric energy harvester (GPEH) with a square bluff body. Comprehensive wind tunnel tests are conducted and experimental data are used to validate our analytical approximate solutions, which are derived from a coupled aero-electro-mechanical model. In addition, the effects of impact disturbances using a bump are investigated. The goal is to improve the performance of baseline GPEH. We expect to collect physical insight to design an optimal nonlinear GPEH configuration by placing bumps accordingly. Lessons learnt from this study will be used to improve the performance of future nonlinear GPEHs and lead to a practical device.

Effects of Rectangular Column Flanges in Steel Structures on Motion-Induced Vortex Vibration

2019 ◽  
Author(s):  
Kazutoshi Matsuda ◽  
Kusuo Kato ◽  
Kazufumi Ejiri ◽  
Nade Cao
Keyword(s):  
Wind Tunnel ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Wind Tunnel Test ◽  
Steel Structures ◽  
Wind Tunnel Tests ◽  
Unsteady Aerodynamic ◽  
Smoke Flow ◽  
Flow Visualizations ◽  
Aerodynamic Lift

Abstract A spring-supported test for a rectangular cross section with the side ratio of B/D = 1.18 (B: along-wind length, D: cross-wind length) was conducted to simulate the phenomenon in a closed circuit wind tunnel at Kyushu Institute of Technology. A new finding was that vibrations were confirmed in the neighborhoods of reduced wind speeds Vr = V/fD = 2 and Vr = 8 (V: wind speed (m/s), f: natural frequency (Hz)). Because the reduced wind speed in motion-induced vortex vibration is calculated as Vr = 1.67 × B/D = 1.67 × 1.18 = 2.0, vibrations around Vr = 2 were considered to be motion-induced vortex vibration. On the other hand, vibrations around Vr = 8 were considered to be Kármán vortex-induced vibrations, because Vr = 1/St = 8.1. St has a Strouhal number of 0.124 measured by wind tunnel test using a rectangular cross section of B/D = 1.18. In this paper, the authors focused on the wind tunnel model configuration. Rectangular column flanges in steel structures have not usually been taken into account when manufacturing wind tunnel test models. Wind tunnel tests were carried out in order to clarify the effects of rectangular column flanges in steel structures on motion-induced vortex vibration. Spring-supported tests, smoke flow visualizations and measurements of Strouhal number and unsteady aerodynamic lift were performed with or without flanges changing angle of attack. Models were forced-oscillating in smoke flow visualizations and unsteady aerodynamic lift measurements. All wind tunnel tests were conducted in a smooth flow. As a result, it was found that it could be very important to model rectangular column flanges in steel structures for wind tunnel tests, especially bracing members of long-spanned truss bridges from a wind engineering point of view.

Methods for Reducing Aerodynamic Drag on Cargo Carrying Railcars

2014 ◽  
Author(s):  
Robert Condie ◽  
Daniel Maynes
Keyword(s):  
Experimental Data ◽  
Wind Tunnel ◽  
Diesel Fuel ◽  
Aerodynamic Drag ◽  
Void Space ◽  
Wind Tunnel Tests ◽  
Large Void ◽  
Roof Structure ◽  
Shipping Costs ◽  
The Cost

In recent years the cost of diesel fuel has increased sharply and this has led to an interest in reducing shipping costs by train. Current manufacturing practices of railcars provide an opportunity for research in methods that reduce the aerodynamic drag. This paper reports on a study which involved collecting experimental data from wind tunnel tests using 1/29 scale train models. Two cargo carrying railcar types were studied. The first were coal carrying railcars and the second were auto carrying railcars. Different features of the railcars were investigated. The largest contributor to drag on the coal cars is the large void space of an empty car. The research investigates several roof structures that cover this space and act to reduce drag. From these structures it is determined that the drag can potentially be reduced by nominally 46%. Similarly, profile features of the auto carrying railcars are also investigated. This research reviewed the roof structure, side panels and chassis structure. From the data, it was determined that drag could be reduced by modifying or covering the roof, side panels and chassis structure by nominally 20%, 5% and 15% respectively.

scholarly journals Development of the Wind Tunnel CFD Model for Clarifying Rotor Blade Airfoil Unsteady Aerodynamic Researches

TEM Journal ◽  
2021 ◽  
pp. 554-562
Author(s):  
Oleg E. Kirillov ◽  
Ruslan M. Mirgazov ◽  
Yuri M. Ignatkin ◽  
Sergey G. Konstantinov ◽  
Pavel V. Makeev ◽  
...  
Keyword(s):  
Experimental Data ◽  
Wind Tunnel ◽  
Aerodynamic Characteristics ◽  
Individual Characteristics ◽  
Helicopter Blade ◽  
Unsteady Aerodynamic ◽  
Wing Section ◽  
Flow Features ◽  
The Individual ◽  
Experimental Rig

A computational model of a wind tunnel (WT) with a special experimental rig has been developed directly for studying unsteady aerodynamic characteristics of a wing section with a helicopter blade profile. The model was constructed using CFD (Computational Fluid Dynamics) methods based on the URANS approach (Unsteady Reynolds Averaged Navier Strokes Equations). Therefore, the aerodynamic characteristics of the airfoil can be determined, taking into account influence of the WT walls such as walls perforation and various configurations of the experimental rig. Simulation of the flow around the wing section with the SC1095 airfoil in steady and unsteady settings is performed. The flow features in the working section of the WT and the experimental rig are analyzed. For a particular case, the calculation method was validated in a 2D formulation on the basis of available experimental data. The developed model can be used to refine the methods of processing experimental data, taking into account the individual characteristics of the WT and the experimental rig configuration.

A fuzzy neural network approach for modeling the growth kinetics of FeB and Fe2B layers during the boronizing process

2018 ◽  
Vol 106 (6) ◽  
pp. 603 ◽  
Author(s):  
Bendaoud Mebarek ◽  
Mourad Keddam
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Fuzzy Neural Network ◽  
Treatment Time ◽  
Calculation Model ◽  
Average Error ◽  
Network Approach ◽  
Neural Network Approach ◽  
Fuzzy Neural ◽  
Kinetics Of

In this paper, we develop a boronizing process simulation model based on fuzzy neural network (FNN) approach for estimating the thickness of the FeB and Fe2B layers. The model represents a synthesis of two artificial intelligence techniques; the fuzzy logic and the neural network. Characteristics of the fuzzy neural network approach for the modelling of boronizing process are presented in this study. In order to validate the results of our calculation model, we have used the learning base of experimental data of the powder-pack boronizing of Fe-15Cr alloy in the temperature range from 800 to 1050 °C and for a treatment time ranging from 0.5 to 12 h. The obtained results show that it is possible to estimate the influence of different process parameters. Comparing the results obtained by the artificial neural network to experimental data, the average error generated from the fuzzy neural network was 3% for the FeB layer and 3.5% for the Fe2B layer. The results obtained from the fuzzy neural network approach are in agreement with the experimental data. Finally, the utilization of fuzzy neural network approach is well adapted for the boronizing kinetics of Fe-15Cr alloy.

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