Rotational lift: something different or more of the same?

2002 ◽  
Vol 205 (24) ◽  
pp. 3783-3792 ◽  
Author(s):  
Jeffrey A. Walker
Keyword(s):  
Fluid Dynamic ◽  
Fruit Fly ◽  
Element Model ◽  
Drosophila Wing ◽  
Wing Model ◽  
Locomotor Control ◽  
Magnus Effect ◽  
Freely Moving ◽  
Attached Vortex ◽  
Blade Element

SUMMARYThis paper addresses the question, do the rotational forces in the hovering fruit fly Drosophila melanogaster reflect something different (the Magnus effect) or more of the same (circulatory-and-attached-vortex force)?The results of an unsteady blade-element model using empirically derived force coefficients from translating (root-oscillating) wings are compared with recent results derived from both the measured forces on a dynamically scaled Drosophila wing and the computational fluid dynamic (CFD)-modeled forces on a virtual Drosophila wing. The behavior of the forces in all three models during wing rotation supports the hypothesis that rotational lift is not a novel aerodynamic mechanism but is caused by the same fluid-dynamic mechanism that occurs during wing translation. A comparison of the unsteady model with a quasi-steady model that employs empirically derived rotational coefficients further supports the hypothesis that rotational forces are more of the same. Finally, the overall similarity of the results between the unsteady model, the physical wing model and the CFD model suggests that the unsteady model can be used to explore the performance consequences of kinematic variation and to investigate locomotor control in freely moving animals.

Evaluation of the CSR-H Sloshing Criterion Using Direct Fluid Structure Calculation

2015 ◽  
Author(s):  
Po-Wen Wang ◽  
Chi-Fang Lee ◽  
Yann Quéméner ◽  
Chien-Hua Huang
Keyword(s):  
Finite Element ◽  
Fluid Dynamic ◽  
Plate Thickness ◽  
Structural Response ◽  
Element Model ◽  
Dynamic Responses ◽  
Interaction Technique ◽  
Time Step ◽  
Fluid Structure ◽  
Structural Rules

The objective of this study was to clarify the theoretical basis of sloshing loads and required plate thickness formulations in the harmonized common structural rules. This study used computational fluid dynamic (CFD) to calculate sloshing loads and used finite element analyses (FEA) to evaluate structural response. The sensitivity of the CFD predictions to the time step and grid size was also investigated. Cargo oil tanks were then selected in a handy size oil tanker and a very large crude carrier to evaluate the longitudinal and transverse sloshing loads on the tank boundaries. The results showed that the sloshing pressures computed at four filling levels were mostly consistent with CSR-H. Afterward, the sloshing pressure produced by CFD was applied to the finite element model by using a fluid-structure interaction technique to obtain the dynamic response of the structure. The dynamic responses were investigated to validate the quasistatic approach for sloshing assessment.

A Theoretical and Experimental Comparison of Optimizing Angle of Twist Using BET and BEMT

2012 ◽  
Author(s):  
Timothy A. Burdett ◽  
Kenneth W. Van Treuren
Keyword(s):  
Experimental Testing ◽  
Element Model ◽  
Experimental Comparison ◽  
Speed Ratio ◽  
Small Scale ◽  
Blade Element Theory ◽  
Wind Speeds ◽  
Subsonic Wind Tunnel ◽  
Element Theory ◽  
Blade Element

Wind turbines are often designed using some form of Blade Element Model (BEM). However, different models can produce significantly different results when optimizing the angle of twist for power production. This paper compares the theoretical result of optimizing the angle of twist using Blade Element Theory (BET) and Blade Element Momentum Theory (BEMT) with a tip-loss correction for a 3-bladed, 1.15-m diameter wind turbine with a design tip speed ratio (TSR) of 5. These two theories have been chosen because they are readily available to small-scale designers. Additionally, the turbine was scaled for experimental testing in the Baylor Subsonic Wind Tunnel. Angle of twist distributions differed by as much as 15 degrees near the hub, and the coefficient of power differed as much as 0.08 for the wind speeds tested.

Added mass effect and an extended unsteady blade element model of insect hovering

2011 ◽  
Vol 8 (4) ◽  
pp. 387-394 ◽  
Author(s):  
Xingyao Yan ◽  
Shanan Zhu ◽  
Zhongdi Su ◽  
Hongjun Zhang
Keyword(s):  
Mass Effect ◽  
Element Model ◽  
Added Mass ◽  
Blade Element

scholarly journals Wind tunnel testing of a swept tip shape and comparison with multi-fidelity aerodynamic simulations

2021 ◽  
Vol 6 (5) ◽  
pp. 1311-1324
Author(s):  
Thanasis Barlas ◽  
Georg Raimund Pirrung ◽  
Néstor Ramos-García ◽  
Sergio González Horcas ◽  
Robert Flemming Mikkelsen ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Pressure Sensors ◽  
Experimental Tests ◽  
Element Model ◽  
Design Solution ◽  
Power Performance ◽  
Tunnel Wall ◽  
Wind Speeds ◽  
Numerical Tests ◽  
Blade Element

Abstract. One promising design solution for increasing the efficiency of modern horizontal axis wind turbines is the installation of curved tip extensions. However, introducing such complex geometries may move traditional aerodynamic models based on blade element momentum (BEM) theory out of their range of applicability. This motivated the present work, where a swept tip shape is investigated by means of both experimental and numerical tests. The latter group accounted for a wide variety of aerodynamic models, allowing us to highlight the capabilities and limitations of each of them in a relative manner. The considered swept tip shape is the result of a design optimization, focusing on locally maximizing power performance within load constraints. For the experimental tests, the tip model is instrumented with spanwise bands of pressure sensors and is tested in the Poul la Cour wind tunnel at the Technical University of Denmark (DTU). The methods used for the numerical tests consisted of a blade element model, a near-wake model, lifting-line free-wake models, and a fully resolved Navier–Stokes solver. The comparison of the numerical and the experimental test results is performed for a given range of angles of attack and wind speeds, which is representative of the expected conditions in operation. Results show that the blade element model cannot predict the measured normal force coefficients, but the other methods are generally in good agreement with the measurements in attached flow. Flow visualization and pressure distribution compare well with computational fluid dynamics (CFD) simulations. The agreement in the clean case is better than in the tripped case at the inboard sections. Some uncertainties regarding the effect of the boundary layer at the inboard tunnel wall and the post-stall behavior remain.

scholarly journals Complete neuroanatomy and sensor maps of Odonata wings for fly-by-feel flight control

2021 ◽  
Author(s):  
Joseph Fabian ◽  
Igor Siwanowicz ◽  
Myriam Uhrhan ◽  
Masateru Maeda ◽  
Richard Bomphrey ◽  
...  
Keyword(s):  
State Estimation ◽  
Flight Control ◽  
Sensory System ◽  
Distribution Patterns ◽  
Element Model ◽  
Sensory Systems ◽  
The Body ◽  
Dynamic State ◽  
Dynamic Strain ◽  
Wing Model

Fly-by-feel describes how flying animals capture aerodynamic information via their wings' sensory system to implement or enhance flight control. Traditional studies on animal flight emphasized controlling body stability via visual or inertial sensory inputs. In line with this, it has been demonstrated that wing sensory systems can provide inertial state estimation for the body. What about the state estimation of the wings themselves? Little is known about how flying animals utilize their wing sensory systems to monitor the dynamic state of their highly deformable wings. This study is a step toward a comprehensive investigation of how a flying animal senses aerodynamic and aeroelastic features of the wings relevant to flight control. Odonates: dragonflies and damselflies, are a great model for this because they have excellent flight performance and their wing structure has been extensively studied. Here, we developed a strategy to map the entire sensory system of Odonata wings via confocal microscopy. The result is the first complete map of a flying animal's wing sensory system, including both the external sensor morphologies and internal neuroanatomy. This complete search revealed over 750 sensors on each wing for one of the smallest dragonfly species and roughly half for a comparable size damselfly. We found over eight morphological classes of sensors, most of which resembled mechanosensors. Most sensors were innervated by a single neuron with an innervation pattern consistent with minimising wiring length. We further mapped the major veins of 13 Odonate species across 10 families and identified consistent sensor distribution patterns, with sensor count scaling with wing length. To explain the strain sensor density distribution along the major veins, we constructed a high-fidelity finite element model of a dragonfly wing based on micro-CT data. This flapping wing model revealed dynamic strain fields and suggested how increasing sensor count could allow encoding of different wing states. Taken together, the Odonate wing sensory system is well-equipped to implement sophisticated fly-by-feel flight control.

Numerical Investigation on the Vibration of Steam Turbine Main Inlet Control Valves Considering Fluid Force Effects

2019 ◽  
Author(s):  
Yueyue Li ◽  
Sihua Xu ◽  
Jin He ◽  
Zhiqiang Hu ◽  
Lei Xiao
Keyword(s):  
Nuclear Power ◽  
Fluid Dynamic ◽  
Control Valve ◽  
Element Model ◽  
Test Results ◽  
Dynamic Flow ◽  
Cfd Simulations ◽  
Warm Up ◽  
Control Valves ◽  
Eigen Frequencies

Abstract In this paper, a finite element model (FEM) for inlet control valve was built and the structural modal analysis was performed to get the Eigen-frequencies of the valve. The valve plug as well as the stem together with piston rod and spring block were analyzed separately. Some peak frequencies of the main inlet control valves were obtained at the 2% lift case during warm-up stage on a nuclear power plant. The dynamic flow field as well as the steam forces were obtained by computational fluid dynamic (CFD) calculations with DES turbulence model. In order to clarify the cause of the valve vibration, the natural frequencies were compared with the test data to indicate that the frequency of certain rocking modes may coincided with the test results. What’s more, the peak frequencies of the dynamic steam forces from CFD simulations were also compared with the rocking modes of control valve to identify the mechanism that cause the vibration at certain frequencies.

Direct Strength Analysis of Semi-Submersible Platform Structures

2004 ◽  
Author(s):  
Haibin Zhang ◽  
Huilong Ren ◽  
Yangshan Dai
Keyword(s):  
Finite Element ◽  
Interpolation Method ◽  
Fluid Dynamic ◽  
Dynamic Pressure ◽  
Three Dimensional ◽  
Element Model ◽  
Strength Analysis ◽  
Wave Load ◽  
Element Analysis ◽  
Wet Surface

A kind of direct strength analysis method of semi-submersible platform structures is presented in this paper. With the differences in shape of pontoon, column and beam being considered, the method of accumulative chord length cubic parameter spline function combined with analytic expression is adopted to generate the mesh of platform wet surface. The hydrodynamic coefficients of the platform are calculated by the three-dimensional potential flow theory of the linear hydrodynamic problem for platforms with low forward speed. The equations of platform motions are established and solved in frequency domain, and the responses of wave-induced loads on the platforms are calculated. According to the mesh of hydrodynamic computation, the fluid dynamic pressure field of platform wet surface is built, and the pressure loads on shell elements in the finite element model of the structure are calculated by the interpolation method. The calculation conditions and loads in the finite element analysis (FEA) of the platform structures are determined according to the design wave analysis approach. A computer program based on this method has been developed, and a calculation example of semi-submersible platform is illustrated. Analysis results show that this method is a satisfying approach for wave load computation and direct strength analysis of the semi-submersible platforms.

A Study on Vibration-Based Damage Detection and Location in an Aircraft Wing Scaled Model

2006 ◽  
Vol 3-4 ◽  
pp. 309-314 ◽  
Author(s):  
Irina Trendafilova
Keyword(s):  
Damage Detection ◽  
Natural Frequencies ◽  
Element Model ◽  
Vibration Response ◽  
Mode Shapes ◽  
Aircraft Wing ◽  
Scaled Model ◽  
Damage Location ◽  
Wing Model ◽  
Simplified Finite Element Model

This study investigates the possibilities for damage detection and location using the vibration response of an aircraft wing. A simplified finite element model of an aircraft wing is used to model its vibration response. The model is subjected to modal analysis- its natural frequencies are estimated and the mode shapes are determined. Two types of damage are considered - localised and distributed. The wing model is divided into a number of volumes. The goal of the study is to investigate the possibility to use the vibration response of an aircraft wing and especially its modal characteristics for the purposes of damage detection. So we’ll be trying to find suitable features, which can be used to detect damage and restrict it to one of the introduced volumes. The sensitivity of the modal frequencies of the model to damage in different locations is studied. Some general trends in the behaviour of these frequencies with change of the damage location are investigated. The utilization of the modal frequencies for detecting damage in a certain part of the wing is discussed

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