An Aerodynamic Analysis of the U.S. Brig Niagara

2007 ◽  
Author(s):  
William C. Lasher ◽  
Terrence D. Musho ◽  
Kent C. McKee ◽  
Walter Rybka
Keyword(s):  
At Risk ◽  
Stability Analysis ◽  
Wind Tunnel ◽  
Full Scale ◽  
Conventional Wisdom ◽  
Aerodynamic Forces ◽  
Wind Speeds ◽  
The Stability ◽  
The U.S ◽  
Heeling Moment

A CFD-based model has been developed for predicting the aerodynamic forces on the rig and sails of the U.S. Brig Niagara. Wind tunnel tests and full-scale experiments were performed to validate the model. The model was then used to predict both the optimum sail trim for various points of sail, as well as the heel angle for different wind speeds. The results show that the optimum bracing (or trim) angle for square sails when sailing off the wind differs significantly from conventional wisdom. The stability analysis shows that the maximum heeling moment occurs when the apparent wind is approximately 80° from the bow, and that with a typical heavy weather sail configuration Niagara would be at risk of capsize in about 40 knots of wind. These results are useful for learning about square rig sailing as well as providing guidance to the Niagara’s officers regarding survivability of the ship.

Model Test Techniques Developed to Investigate the Wind Heeling Characteristics of Sailing Vessels and Their Response to Gusts

1991 ◽  
Author(s):  
Barry Deakin
Keyword(s):  
Wind Tunnel ◽  
Model Test ◽  
Wind Tunnels ◽  
Stability Assessment ◽  
Tunnel Floor ◽  
The Stability ◽  
Scaled Models ◽  
Scale Data ◽  
Heeling Moment ◽  
Gust Response

During the development of new stability regulations for the U.K. Department of Transport, doubt was cast over many of the assumptions made when assessing the stability of sailing vessels. In order to investigate the traditional methods a programme of work was undertaken including wind tunnel tests and full scale data acquisition. The work resulted in a much improved understanding of the behaviour of sailing vessels and indeed indicated that the conventional methods of stability assessment are invalid, the rules now applied in the U.K. being very different to those in use elsewhere. The paper concentrates on the model test techniques which were developed specifically for this project but which will have implications to other vessel types. The tests were of two kinds: measurement of the wind forces and moments on a sailing vessel; and investigation of the response of sailing vessels to gusts of wind. For the force and moment measurements models were mounted in a tank of water on a six component balance and tested in a large boundary layer wind tunnel. Previous tests in wind tunnels have always concentrated on performance and the heeling moments have not normally been measured correctly. As the measurements of heeling moment at a range of heel angles was of prime importance a new balance and mounting system was developed which enabled the above water part of the vessel to be modelled correctly, the underwater part to be unaffected by the wind, and the interface to be correctly represented without interference. Various effects were investigated including rig type, sheeting, heading, heel angle and wind gradient. The gust response tests were conducted with Froude scaled models floating in a pond set in the wind tunnel floor. A mechanism was installed in the tunnel which enabled gusts of various characteristics to be generated, and the roll response of the models was measured with a gyroscope. These tests provided information on the effects of inertia, damping, rolling and the characteristics of the gust. Sample results are presented to illustrate the uses to which these techniques have been put.

scholarly journals Prediction of the hub vortex instability in a wind turbine wake: stability analysis with eddy-viscosity models calibrated on wind tunnel data

2014 ◽  
Vol 750 ◽  
Author(s):  
F. Viola ◽  
G. V. Iungo ◽  
S. Camarri ◽  
F. Porté-Agel ◽  
F. Gallaire
Keyword(s):  
Stability Analysis ◽  
Wind Tunnel ◽  
Wind Turbine ◽  
Eddy Viscosity ◽  
General Interest ◽  
Mean Velocity ◽  
Vortex Instability ◽  
Viscosity Models ◽  
Wind Tunnel Data ◽  
The Stability

AbstractThe instability of the hub vortex observed in wind turbine wakes has recently been studied by Iungo et al. (J. Fluid Mech., vol. 737, 2013, pp. 499–526) via local stability analysis of the mean velocity field measured through wind tunnel experiments. This analysis was carried out by neglecting the effect of turbulent fluctuations on the development of the coherent perturbations. In the present paper, we perform a stability analysis taking into account the Reynolds stresses modelled by eddy-viscosity models, which are calibrated on the wind tunnel data. This new formulation for the stability analysis leads to the identification of one clear dominant mode associated with the hub vortex instability, which is the one with the largest overall downstream amplification. Moreover, this analysis also predicts accurately the frequency of the hub vortex instability observed experimentally. The proposed formulation is of general interest for the stability analysis of swirling turbulent flows.

An Improved Upwind Sail Model For VPP's

2001 ◽  
Author(s):  
Peter Jackson
Keyword(s):  
Wind Tunnel ◽  
Full Scale ◽  
Original Solution ◽  
Wide Range ◽  
Velocity Prediction ◽  
Improved Model ◽  
Heeling Moment

In velocity prediction programs for yachts the problem of modelling sail forces is greatly complicated by the fact that the sail shapes are not fixed. For a given sail plan, alterations in sail trim produce a wide range of combinations of lift, drag and heeling moment. While the original solution to this problem using the well-known parameters flat and reef has been very successful, it has some obvious defects. In particular, it does not correctly model the practice of twisting a sail to reduce heeling moment. This paper therefore sets out an improved model which satisfies the essential requirements for upwind sails; namely that the model is based upon fundamental aerodynamic principles, allows all the unknowns to be determined from tests (full scale or wind tunnel) and permits the best sail trim to be selected for optimization of performance. The essential new step is to introduce a new trim parameter twist which correctly accounts for the practice of allowing the head of a sail to twist off in order to reduce heeling moment.

Using Wind Tunnel Tests for Slung-Load Clearance, Part 1: The CONEX Cargo Container

2014 ◽  
Vol 59 (4) ◽  
pp. 1-12
Author(s):  
Reuben Raz ◽  
Aviv Rosen ◽  
Luigi S. Cicolani ◽  
Jeffery Lusardi
Keyword(s):  
Wind Tunnel ◽  
Center Of Gravity ◽  
Full Scale ◽  
Wind Tunnel Tests ◽  
Cargo Container ◽  
The Stability ◽  
Container Model

Previously, the authors showed that dynamic wind tunnel tests of a suspended CONEX cargo container model exhibited encouraging levels of success in predicting the stability characteristics and speed envelope of the full-scale load. The present study includes further use of the UH-60/CONEX system to investigate effects that were observed previously, but not fully addressed. These effects include the influence of pilot inputs and helicopter motions on the coupled pilot/helicopter/slung-load dynamics, the influence of center of gravity offset of the slung load, and the behavior of a load when a yaw swivel is not used in the suspension. It is shown that all three effects are important and affect the slung-load dynamics. The capability of wind tunnel tests to predict the behavior of slung loads in flight is shown for these effects.

The Spinning of Aeroplanes

1927 ◽  
Vol 31 (199) ◽  
pp. 619-688 ◽  
Author(s):  
L. W. Bryant ◽  
S. B. Gates
Keyword(s):  
Wind Tunnel ◽  
Preliminary Report ◽  
Full Scale ◽  
Wind Tunnel Experiments ◽  
Research Committee ◽  
Stability And Control ◽  
The Subject ◽  
Ready Access ◽  
The Stability ◽  
And Control

We should like to preface our essay on the subject of spinning by mentioning the circumstances under which our investigations were carried out and the sources of our information. The Panel of the Aeronautical Research Committee which has been appointed to deal with all questions connected with the stability and control of aeroplanes was requested in 1924 to consider the urgent problems connected with the alarming accidents due to certain machines failing to retover from a spin. After the issue of a preliminary report on the situation by the Panel, the writers of this paper were asked to go into the whole question as far as existing information from full-scale and wind tunnel experiments would permit. We have had ready access to all available data, coming chiefly from Farnborough on the full-scale side, and from the N.P.L. on the model side.

An Automatic Variable Pitch Airscrew

1932 ◽  
Vol 36 (254) ◽  
pp. 111-126 ◽  
Author(s):  
H. C. H. Townend
Keyword(s):  
Wind Tunnel ◽  
Full Scale ◽  
Wind Tunnel Experiments ◽  
Aerodynamic Forces ◽  
Variable Pitch ◽  
Minimum Drag ◽  
Air Density ◽  
Resultant Effect ◽  
Engine Failure

Some wind tunnel experiments have been made on a variable pitch airscrew which shall change its pitch automatically as V/nD changes. The change in pitch is operated by the resultant effect of centrifugal and aerodynamic forces.Reduction in air density, e.g., due to increase in height, causes an increase in pitch.In the event of engine failure the blades assume the position of minimum drag.A tentative design for a model screw, together with tests thereon, are described, and it appears that if the friction in the bearings about which the change in pitch occurs can be made reasonably small, it should be possible to construct a satisfactory full-scale screw.

scholarly journals Nonlinear Aeroelastic Simulations and Stability Analysis of the Pazy Wing Aeroelastic Benchmark

Aerospace ◽  
2021 ◽  
Vol 8 (10) ◽  
pp. 308
Author(s):  
Jonathan Hilger ◽  
Markus Raimund Ritter
Keyword(s):  
Stability Analysis ◽  
Wind Tunnel ◽  
Vortex Lattice ◽  
Structural Model ◽  
State Space Model ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Aeroelastic Simulations ◽  
The Stability ◽  
German Aerospace

The Pazy wing aeroelastic benchmark is a highly flexible wind tunnel model investigated in the Large Deflection Working Group as part of the Third Aeroelastic Prediction Workshop. Due to the design of the model, very large elastic deformations in the order of 50% span are generated at highest dynamic pressures and angles of attack in the wind tunnel. This paper presents static coupling simulations and stability analyses for selected onflow velocities and angles of attack. Therefore, an aeroelastic solver developed at the German Aerospace Center (DLR) is used for static coupling simulations, which couples a vortex lattice method with the commercial finite element solver MSC Nastran. For the stability analysis, a linearised aerodynamic model is derived analytically from the unsteady vortex lattice method and integrated with a modal structural model into a monolithic aeroelastic discrete-time state-space model. The aeroelastic stability is then determined by calculating the eigenvalues of the system’s dynamics matrix. It is shown that the stability of the wing in terms of flutter changes significantly with increasing deflection and is heavily influenced by the change in modal properties, i.e., structural eigenvalues and eigenvectors.

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