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.

scholarly journals Aerodynamic study of a suspension bridge deck by CFD simulations, wind tunnel tests and full-scale observations

2021 ◽  
Vol 1201 (1) ◽  
pp. 012007
Author(s):  
I. Kusano ◽  
E. Cheynet ◽  
J. B. Jakobsen ◽  
J. Snæbjörnsson
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Suspension Bridge ◽  
Aerodynamic Characteristics ◽  
Full Scale ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Wind Tunnel Tests ◽  
Long Span Bridges ◽  
Wide Range

Abstract Assessing the aerodynamic characteristics of long-span bridges is fundamental for their design. Depending on the terrain complexity and local wind conditions, episodes of large angles of attack (AoA) of 15° may be observed. However, such large AoAs ( above 10°) are often overlooked in the design process. This paper studies the aerodynamics properties of a flow around a single-box girder for a wide range of AoAs, from –20° to 20°, using numerical simulations. The simulations are based on a 2D unsteady Reynolds-averaged Navier–Stokes (URANS) approach using the k − ω SST turbulence model with a Reynolds number of 1.6 × 105. Numerically obtained aerodynamic static coefficients were compared to wind tunnel test data. The CFD results were generally in good agreement with the wind tunnel tests, especially for small AoAs and positive AoAs. More discrepancies were observed for large negative AoA, likely due to the limitation of modelling 3D railings with 2D simulations. The simulated velocity deficit downstream of the deck was consistent with the one measured in full-scale using short-range Doppler wind lidar instruments. Finally, the Strouhal number from the CFD simulations were in agreement with the value obtained from the full-scale data.

Enhanced Wind Tunnel and Full-Scale Sail Force Comparison

2007 ◽  
Author(s):  
Heikki Hansen ◽  
Peter J. Richards ◽  
Peter S. Jackson
Keyword(s):  
Wind Tunnel ◽  
Quantitative Agreement ◽  
Full Scale ◽  
Force Balance ◽  
Testing Procedures ◽  
Prediction Program ◽  
Surface Pressure Distribution ◽  
Velocity Prediction ◽  
The University ◽  
Scale Data

This paper presents a comparison between wind tunnel and full-scale aerodynamic sail force measurements using enhanced wind tunnel testing techniques to model the full-scale sailing conditions more accurately. The first comparison was conducted by Hansen et al., 2003a, in the Twisted Flow Wind Tunnel (TFWT) at The University of Auckland and followed standard testing procedures. Since then enhancements have been made and two aspects not considered in the original comparison are highlighted here. The interaction of the hull and sail forces is now considered and trim changes of the sails due to wind strength are included. For the enhanced comparison the interaction between the hull/deck and the sails is investigated by installing a secondary force balance inside the model to measure the hull/deck forces and by pressure tapping the hull/deck to determine the surface pressure distribution. It is found that the presence of the sails significantly affects the forces on hull/deck when sailing upwind, which should be accounted for consistently in comparisons of full-scale, wind tunnel, and computational fluid dynamics (CFD) data. In the original comparison the sails were trimmed in the wind tunnel to the aerodynamically optimal shape by maximizing the drive force. Trim variations due to wind strength were however noted in full-scale data so that depowering is considered in the enhanced comparison. The sails in the wind tunnel were trimmed based on the fullscale wind strength and the yacht performance by employing a Real-Time Velocity Prediction Program (VPP) to achieve realistically depowered sail shapes. Utilising the enhanced wind tunnel techniques a generally good qualitative and quantitative agreement with the full-scale data was achieved, but a conclusive judgment of the accuracy of the comparison cannot be made.

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.

Wind Tunnel to Full Scale Mapping of Winds and Loads for Launch-Vehicle Ground Wind Loads

2021 ◽  
Author(s):  
Thomas G. Ivanco ◽  
Donald F. Keller ◽  
Jennifer L. Pinkerton
Keyword(s):  
Wind Tunnel ◽  
Launch Vehicle ◽  
Full Scale ◽  
Wind Loads

Characterization of wind-induced pressure on membrane roofs based on full-scale wind tunnel testing

2021 ◽  
Vol 235 ◽  
pp. 112101
Author(s):  
Johnny Estephan ◽  
Changda Feng ◽  
Arindam Gan Chowdhury ◽  
Mauricio Chavez ◽  
Appupillai Baskaran ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Full Scale ◽  
Wind Tunnel Testing ◽  
Tunnel Testing

Coupled Thermo-Hydro-Geochemical Models of Engineered Barrier Systems: The Febex Project

2000 ◽  
Vol 663 ◽  
Author(s):  
J. Samper ◽  
R. Juncosa ◽  
V. Navarro ◽  
J. Delgado ◽  
L. Montenegro ◽  
...  
Keyword(s):  
Large Scale ◽  
Reference Model ◽  
Numerical Models ◽  
Full Scale ◽  
Small Scale ◽  
Model Parameters ◽  
In Situ Test ◽  
Wide Range ◽  
Engineered Barrier

ABSTRACTFEBEX (Full-scale Engineered Barrier EXperiment) is a demonstration and research project dealing with the bentonite engineered barrier designed for sealing and containment of waste in a high level radioactive waste repository (HLWR). It includes two main experiments: an situ full-scale test performed at Grimsel (GTS) and a mock-up test operating since February 1997 at CIEMAT facilities in Madrid (Spain) [1,2,3]. One of the objectives of FEBEX is the development and testing of conceptual and numerical models for the thermal, hydrodynamic, and geochemical (THG) processes expected to take place in engineered clay barriers. A significant improvement in coupled THG modeling of the clay barrier has been achieved both in terms of a better understanding of THG processes and more sophisticated THG computer codes. The ability of these models to reproduce the observed THG patterns in a wide range of THG conditions enhances the confidence in their prediction capabilities. Numerical THG models of heating and hydration experiments performed on small-scale lab cells provide excellent results for temperatures, water inflow and final water content in the cells [3]. Calculated concentrations at the end of the experiments reproduce most of the patterns of measured data. In general, the fit of concentrations of dissolved species is better than that of exchanged cations. These models were later used to simulate the evolution of the large-scale experiments (in situ and mock-up). Some thermo-hydrodynamic hypotheses and bentonite parameters were slightly revised during TH calibration of the mock-up test. The results of the reference model reproduce simultaneously the observed water inflows and bentonite temperatures and relative humidities. Although the model is highly sensitive to one-at-a-time variations in model parameters, the possibility of parameter combinations leading to similar fits cannot be precluded. The TH model of the “in situ” test is based on the same bentonite TH parameters and assumptions as for the “mock-up” test. Granite parameters were slightly modified during the calibration process in order to reproduce the observed thermal and hydrodynamic evolution. The reference model captures properly relative humidities and temperatures in the bentonite [3]. It also reproduces the observed spatial distribution of water pressures and temperatures in the granite. Once calibrated the TH aspects of the model, predictions of the THG evolution of both tests were performed. Data from the dismantling of the in situ test, which is planned for the summer of 2001, will provide a unique opportunity to test and validate current THG models of the EBS.

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.

A New Method of Modeling Underexpanded Exhaust Plumes for Wind Tunnel Aerodynamic Testing

1989 ◽  
Vol 111 (4) ◽  
pp. 748-754
Author(s):  
V. Salemann ◽  
J. M. Williams
Keyword(s):  
Wind Tunnel ◽  
Free Stream ◽  
Dynamic Pressure ◽  
Pressure Ratio ◽  
Area Ratio ◽  
Full Scale ◽  
New Method ◽  
Thrust Coefficient ◽  
Model Scale ◽  
Exhaust Plumes

A new method for modeling hot underexpanded exhaust plumes with cold model scale plumes in aerodynamic wind tunnel testing has been developed. The method is applicable to aeropropulsion testing where significant interaction between the exhaust and the free stream and aftbody may be present. The technique scales the model and nozzle external geometry, including the nozzle exit area, matches the model jet to free-stream dynamic pressure ratio to full-scale jet to free-stream dynamic pressure ratio, and matches the model thrust coefficient to full-scale thrust coefficient. The technique does not require scaling of the internal nozzle geometry. A generalized method of characteristic computer code was used to predict the plume shapes of a hot (γ = 1.2) half-scale nozzle of area ratio 3.2 and of a cold (γ = 1.4) model scale nozzle of area ratio 1.3, whose pressure ratio and area ratio were selected to satisfy the above criteria and other testing requirements. The plume shapes showed good agreement. Code validity was checked by comparing code results for cold air exhausting into a quiescent atmosphere to pilot surveys and shadowgraphs of model nozzle plumes taken in a static facility.

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