scholarly journals Forward flight of birds revisited. Part 1: aerodynamics and performance

2014 ◽  
Vol 1 (2) ◽  
pp. 140248 ◽  
Author(s):  
G. Iosilevskii
Keyword(s):  
Flight Performance ◽  
Lattice Method ◽  
Method Performance ◽  
Entire Study ◽  
Vortex Lattice Method ◽  
Aerodynamic Model ◽  
High Speeds ◽  
The Difference ◽  
And Performance ◽  
Lifting Line

This paper is the first part of the two-part exposition, addressing performance and dynamic stability of birds. The aerodynamic model underlying the entire study is presented in this part. It exploits the simplicity of the lifting line approximation to furnish the forces and moments acting on a single wing in closed analytical forms. The accuracy of the model is corroborated by comparison with numerical simulations based on the vortex lattice method. Performance is studied both in tethered (as on a sting in a wind tunnel) and in free flights. Wing twist is identified as the main parameter affecting the flight performance—at high speeds, it improves efficiency, the rate of climb and the maximal level speed; at low speeds, it allows flying slower. It is demonstrated that, under most circumstances, the difference in performance between tethered and free flights is small.

Unsteady aerodynamics investigation of deploying tandem-wing with different methods

2018 ◽  
Vol 233 (10) ◽  
pp. 3714-3733 ◽  
Author(s):  
Hao Cheng ◽  
Hua Wang ◽  
Qingli Shi ◽  
Mengying Zhang
Keyword(s):  
Fore Wing ◽  
Vortex Lattice ◽  
Lift Coefficient ◽  
Unsteady Aerodynamics ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Induced Drag ◽  
Lifting Line ◽  
Lifting Line Method ◽  
Unsteady Lift

In the rapidly deploying process of the unmanned aerial vehicle with folding wings, the aerodynamic characteristics could be largely different owing to the effects of deformation rate and the aerodynamic interference. The investigation on the unsteady aerodynamics is of great significance for the stability analysis and control design. The lifting-line method and the vortex-lattice method are improved to calculate the unsteady aerodynamics in the morphing stage. It is validated that the vortex-lattice method predicts the unsteady lift coefficient more appropriately than the lifting-line method. Different tandem wing configurations with deployable wings are simulated with different deformation rates during the morphing stage by the vortex-lattice method. As results indicated, the unsteady lift coefficient and the induced drag of the fore wing rise with the deformation rate increasing, but it is reversed for the hind wing. Additionally, the unsteady lift coefficient of the tandem wing configuration performs well with a larger stagger, a larger magnitude of the gap and a larger wingspan of the fore wing; however, the total induced drag has a larger value for the configuration that the two lifting surfaces with the same wingspans are closer to each other.

A THREE-DIMENSIONAL INVERSE METHOD FOR THE DESIGN OF SAILS

2016 ◽  
Vol 158 (B2) ◽  
Author(s):  
J P Pilate ◽  
F C Gerhardt ◽  
S E Norris ◽  
R G J Flay
Keyword(s):  
Inverse Method ◽  
Three Dimensional ◽  
Differential Pressure ◽  
Analysis Approach ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Pressure Distributions ◽  
Target Loading ◽  
The Difference ◽  
Geometry Correction

This paper investigates an inverse process for the design of yacht sails. The method is described and then applied to the design of optimal sails for a specific yacht. The proposed inverse method generates the three-dimensional shapes of a headsail and mainsail from prescribed loading (i.e. differential pressure) distributions, accounts for the effect of the sea surface, and also simulates the twist and shear of the incoming flow. The uncoupled iterative routine solves a sequence of analysis steps so that the sail shapes are deformed in such a way that their updated loading distributions converge to the specified target distributions. During each iteration equations derived from two-dimensional Thin Aerofoil Theory, calculate a geometry correction from the difference between the current and target loading distributions. This correction is applied to the sail geometry, and a vortex lattice method code calculates the updated three-dimensional differential pressure distributions, which are again compared to the target distributions. Usually only five iterations are required to converge to sail shapes that have the target loading distributions. The inverse method has been validated by inverting the traditional way of analysing sails, i.e. a set of sails with known geometry has been analysed and the loading distributions on the headsail and mainsail were calculated. These distributions were then used as an input for the inverse code. It was found that the difference in camber between the original sails and the calculated geometry is less than 0.01% of camber at the mid-span of the sails. The second part of the paper presents two methods for the design of optimal sails for a yacht. One of the methods uses the more traditional analysis approach, while the other employs the inverse method described in this paper. The optimisation is performed for a Transpac 52 yacht in 12 knots (6.5 m/s) of true wind speed to obtain the best velocity made good. Results from both methods are presented and discussed and it is found that the results in terms of boat speed are similar although the trims differ slightly. However, the new inverse method is approximately nine times faster than the traditional analysis approach.

Computational Models for Prediction of Performance and Design of Tidal Turbines

2010 ◽  
Author(s):  
Spyros A. Kinnas ◽  
Wei Xu ◽  
Yi-Hsiang Yu
Keyword(s):  
Computational Models ◽  
Vortex Lattice ◽  
Design Procedure ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Tidal Turbines ◽  
Unsteady Wake ◽  
Tidal Turbine ◽  
Wake Alignment ◽  
Lifting Line

In this paper, the performance of a horizontal axis, 3-blade tidal turbine is predicted by a vortex lattice method, in which the fully unsteady wake alignment is utilized to model the trailing wake geometry. A blade design procedure, which combines a lifting line approach with the vortex lattice analysis method and a nonlinear optimization scheme, is proposed.

scholarly journals Typhoon: A vortex-lattice code for assessing dynamic stability characteristics of hydrofoil crafts

2021 ◽  
pp. 1-18
Author(s):  
Alec Bagué ◽  
Joris Degroote ◽  
Toon Demeester ◽  
Evert Lataire
Keyword(s):  
Stability Analysis ◽  
Dynamic Stability ◽  
Vortex Lattice ◽  
Theoretical Explanation ◽  
Surface Boundary ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Lattice Codes ◽  
Cheap Alternative ◽  
The Difference

In this paper an open-source implementation of the vortex-lattice method to perform a dynamic stability analysis for hydrofoil crafts is discussed. The difference with existing vortex-lattice codes is the addition of a free-surface boundary condition which is needed to analyse surface piercing foils. This code, called Typhoon, can be used to perform a dynamic stability analysis (DSA) on hydrofoil vessels. The goal of this code is to have an easy-to-use and cheap alternative to compare different designs in early design stages. This paper gives a brief background to all the concepts used, followed by a short theoretical explanation of the vortex-lattice method. The second part of this paper focuses on a practical example of how this code can be used on an example.

Aerodynamic model of propeller–wing interaction for distributed propeller aircraft concept

2019 ◽  
Vol 234 (10) ◽  
pp. 1688-1705 ◽  
Author(s):  
Baizura Bohari ◽  
Quentin Borlon ◽  
Murat Bronz ◽  
Emmanuel Benard
Keyword(s):  
Experimental Data ◽  
Vortex Lattice ◽  
Numerical Models ◽  
Aircraft Design ◽  
Computational Time ◽  
Nonlinear Prediction ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Blade Element Theory ◽  
Aerodynamic Model

The present investigation addresses two key issues in aerodynamic performance of a propeller–wing configuration, namely linear and nonlinear predictions with low-order numerical models. The developed aerodynamic model is targeted to be used in the preliminary aircraft design loop. First, the combination of selected propeller model, i.e. blade element theory with the wing model, i.e. lifting line theory and vortex lattice method is considered for linear aerodynamic model. Second, for the nonlinear prediction, a modified vortex lattice method is paired with the two-dimensional viscous effect of the airfoils to simplify and reduce the computational time. These models are implemented and validated with existing experimental data to predict the differences in lift and drag distribution. Overall, the predicted results show agreement with low percentage of error compared with the experimental data for various thrust coefficients and produced induced drag distribution that behaves as expected.

A Combined Vortex Lattice Lifting Line Method for Unsteady Propeller Calculations

2021 ◽  
Author(s):  
Andreas Büsken ◽  
Stefan Krüger
Keyword(s):  
Vortex Lattice ◽  
Suction Side ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Vortex Model ◽  
Coupling Strategy ◽  
Line Theory ◽  
Lifting Line ◽  
Oseen Vortex ◽  
Lifting Line Method

Abstract This paper presents a Combined Method for the calculation of propeller forces in inhomogeneous inflow. It consists of an extended Goldstein approach based on Lifting Line Theory and a Vortex Lattice Method. After a brief overview of both methods is given, the coupling strategy is described and the additional modifications are explained. A correction factor accounting for the vortex which develops under a separated and later reattached flow on the suction side of the propeller blade is implemented as the first modification. Further, the Lamb-Oseen vortex model is used for the vortices in the free vortex system of the propeller. Finally, some results achieved with the described method are presented and compared to measured values.

Effect of Wake Alignment on Turbine Blade Loading Distribution and Power Coefficient

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
David H. Menéndez Arán ◽  
Ye Tian ◽  
Spyros A. Kinnas
Keyword(s):  
Optimization Method ◽  
Power Coefficient ◽  
Viscous Drag ◽  
Lattice Method ◽  
Blade Loading ◽  
Vortex Lattice Method ◽  
Abrupt Changes ◽  
Alignment Model ◽  
Wake Alignment ◽  
Lifting Line

This paper describes the use of a lifting line model in order to determine the optimum loading on a marine turbine's blades. The influence of the wake and its geometry is represented though the use of a full wake alignment model. The effects of viscous drag are included through a drag-to-lift ratio. Results for different number of blades and tip speed ratios are presented. Various types of constraints are imposed in the optimization method in order to avoid abrupt changes in the designed blade shape. The effect of the constraints on the power coefficients of the turbines is studied. Once the optimum loading has been determined, the blade geometry is generated for a given chord and camber distributions. Finally, a vortex-lattice method is used to verify the power coefficient of the designed turbines.

A Modification of the Payne-Jones Method of Identifying Abnormal Differences in WISC-R Performance and Verbal IQ's

1996 ◽  
Vol 12 (1) ◽  
pp. 27-32 ◽  
Author(s):  
Louis M. Hsu
Keyword(s):  
Full Scale ◽  
True Score ◽  
Verbal Iq ◽  
Score Difference ◽  
The Difference ◽  
And Performance

The difference (D) between a person's Verbal IQ (VIQ) and Performance IQ (PIQ) has for some time been considered clinically meaningful ( Kaufman, 1976 , 1979 ; Matarazzo, 1990 , 1991 ; Matarazzo & Herman, 1985 ; Sattler, 1982 ; Wechsler, 1984 ). Particularly useful is information about the degree to which a difference (D) between scores is “abnormal” (i.e., deviant in a standardization group) as opposed to simply “reliable” (i.e., indicative of a true score difference) ( Mittenberg, Thompson, & Schwartz, 1991 ; Silverstein, 1981 ; Payne & Jones, 1957 ). Payne and Jones (1957) proposed a formula to identify “abnormal” differences, which has been used extensively in the literature, and which has generally yielded good approximations to empirically determined “abnormal” differences ( Silverstein, 1985 ; Matarazzo & Herman, 1985 ). However applications of this formula have not taken into account the dependence (demonstrated by Kaufman, 1976 , 1979 , and Matarazzo & Herman, 1985 ) of Ds on Full Scale IQs (FSIQs). This has led to overestimation of “abnormality” of Ds of high FSIQ children, and underestimation of “abnormality” of Ds of low FSIQ children. This article presents a formula for identification of abnormal WISC-R Ds, which overcomes these problems, by explicitly taking into account the dependence of Ds on FSIQs.

Generalized vortex lattice method for planar supersonic flow

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 1230-1233
Author(s):  
Paulo A. O. Soviero ◽  
Hugo B. Resende
Keyword(s):  
Supersonic Flow ◽  
Vortex Lattice ◽  
Lattice Method ◽  
Vortex Lattice Method

scholarly journals Static Aeroelastic Characteristics of Morphing Trailing-Edge Wing Using Geometrically Exact Vortex Lattice Method

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Sen Mao ◽  
Changchuan Xie ◽  
Lan Yang ◽  
Chao Yang
Keyword(s):  
Vortex Lattice ◽  
Deflection Angle ◽  
Aircraft Design ◽  
Analysis Method ◽  
Lattice Method ◽  
Trailing Edge ◽  
Vortex Lattice Method ◽  
Analysis And Design ◽  
Aeroelastic Analysis ◽  
Typical Model

A morphing trailing-edge (TE) wing is an important morphing mode in aircraft design. In order to explore the static aeroelastic characteristics of a morphing TE wing, an efficient and feasible method for static aeroelastic analysis has been developed in this paper. A geometrically exact vortex lattice method (VLM) is applied to calculate the aerodynamic forces. Firstly, a typical model of a morphing TE wing is chosen and built which has an active morphing trailing edge driven by a piezoelectric patch. Then, the paper carries out the static aeroelastic analysis of the morphing TE wing and corresponding simulations were carried out. Finally, the analysis results are compared with those of a traditional wing with a rigid trailing edge using the traditional linearized VLM. The results indicate that the geometrically exact VLM can better describe the aerodynamic nonlinearity of a morphing TE wing in consideration of geometrical deformation in aeroelastic analysis. Moreover, out of consideration of the angle of attack, the deflection angle of the trailing edge, among others, the wing system does not show divergence but bifurcation. Consequently, the aeroelastic analysis method proposed in this paper is more applicable to the analysis and design of a morphing TE wing.

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