scholarly journals Split-Flaps – a Way to Improve the Heel Stability of T-Foil Supported Craft

2021 ◽  
Vol 7 (01) ◽  
pp. 1-30
Author(s):  
N. S. S. Prabahar ◽  
A. Persson ◽  
L. Larsson
Keyword(s):  
Induced Resistance ◽  
Lift Force ◽  
Symmetry Plane ◽  
Ride Height ◽  
Prediction Program ◽  
Custom Made ◽  
Dynamic Velocity ◽  
Improved Stability ◽  
The Difference ◽  
Righting Moment

Abstract Horizontal T-foils allow for maximum lift generation within a given span. However, the lift force on a T-foil acts on the symmetry plane of the hull, thereby producing no righting moment. It results in a lack of transverse stability during foil-borne sailing. In this paper, we propose a system, where the height-regulating flap on the trailing edge of the foil is split into a port and a starboard part, whose deflection angles are adjusted to shift the centre of effort of the lift force. Similar to the ailerons which help in steering aircraft, the split-flaps produce an additional righting moment for stabilizing the boat. The improved stability comes, however, at a cost of additional induced resistance. To investigate the performance of the split-flap system a new Dynamic Velocity Prediction Program (DVPP) is developed. Since it is very important for the performance evaluation of the proposed system it is described in some detail in the paper. A complicated effect to model in the DVPP is the flow in the slot between the two flaps and the induced resistance due to the generated vorticity. Therefore, a detailed CFD investigation is carried out to validate a model for the resistance due to the slot effect. Two applications of the split-flap system: an Automated Heel Stability System (AHSS) and a manual offset system for performance increase are studied using a DVPP for a custom-made double-handed skiff. It is shown that the AHSS system can assist the sailors while stabilizing the boat during unsteady wind conditions. The manual offset enables the sailors to adjust the difference between the deflection angles of the two flaps while sailing, thus creating a righting moment whenever required. Such a system would be an advantage whilst sailing with a windward heel. Due to the additional righting moment from the manual offset system, the sails could be less depowered by the sailors resulting in a faster boat despite the additional induced resistance. It is shown in the paper that the control systems for the ride height and the heel stability need to be decoupled. The paper ends with a description of a mechanical system that satisfies this requirement.

scholarly journals Numerical tools to estimate the flux of a gas across the air–water interface and assess the heterogeneity of its forcing functions

Ocean Science ◽  
2013 ◽  
Vol 9 (2) ◽  
pp. 355-375 ◽  
Author(s):  
V. M. N. C. S. Vieira ◽  
F. Martins ◽  
J. Silva ◽  
R. Santos
Keyword(s):  
Atmospheric Stability ◽  
Water Interface ◽  
Co2 Fluxes ◽  
Gas Flux ◽  
Ria Formosa ◽  
Custom Made ◽  
Air Water Interface ◽  
Forcing Functions ◽  
Flux Model ◽  
The Difference

Abstract. A numerical tool was developed for the estimation of gas fluxes across the air–water interface. The primary objective is to use it to estimate CO2 fluxes. Nevertheless application to other gases is easily accomplished by changing the values of the parameters related to the physical properties of the gases. A user-friendly software was developed allowing to build upon a standard kernel a custom-made gas flux model with the preferred parameterizations. These include single or double layer models; several numerical schemes for the effects of wind in the air-side and water-side transfer velocities; the effects of atmospheric stability, surface roughness and turbulence from current drag with the bottom; and the effects on solubility of water temperature, salinity, air temperature and pressure. An analysis was also developed which decomposes the difference between the fluxes in a reference situation and in alternative situations into its several forcing functions. This analysis relies on the Taylor expansion of the gas flux model, requiring the numerical estimation of partial derivatives by a multivariate version of the collocation polynomial. Both the flux model and the difference decomposition analysis were tested with data taken from surveys done in the lagoon system of Ria Formosa, south Portugal, in which the CO2 fluxes were estimated using the infrared gas analyzer (IRGA) and floating chamber method, whereas the CO2 concentrations were estimated using the IRGA and degasification chamber. Observations and estimations show a remarkable fit.

scholarly journals High Froude Number Experimental Investigation of the 2 DOF Behavior of a Multihull Float in Head Waves

2021 ◽  
Vol 6 (01) ◽  
pp. 1-20
Author(s):  
Paul Kerdraon ◽  
Boris Horel ◽  
Patrick Bot ◽  
Adrien Letourneur ◽  
David David Le Touzé
Keyword(s):  
High Performance ◽  
Good Representation ◽  
Prediction Program ◽  
Modeling Approach ◽  
Head Waves ◽  
Wide Range ◽  
Dynamic Velocity ◽  
Velocity Prediction ◽  
High Froude Number ◽  
Stability Issues

Dynamic Velocity Prediction Programs are taking an increasingly prominent role in high performance yacht design, as they allow to deal with seakeeping abilities and stability issues. Their validation is however often neglected for lack of time and data. This paper presents an experimental campaign carried out in the towing tank of the Ecole Centrale de Nantes, France, to validate the hull modeling in use in a previously presented Dynamic Velocity Prediction Program. Even though with foils, hulls are less frequently immersed, a reliable hull modeling is necessary to properly simulate the critical transient phases such as touchdowns and takeoffs. The model is a multihull float with a waterline length of 2.5 m. Measurements were made in head waves in both captive and semi-captive conditions (free to heave and pitch), with the model towed at constant yaw and speed. To get as close as possible to real sailing conditions, experiments were made at both zero and non-zero leeway angles, sweeping a wide range of speed values, with Froude numbers up to 1.2. Both linear and nonlinear wave conditions were studied in order to test the limits of the modeling approach, with wave steepness reaching up to 7% in captive conditions and 3.5% in semi-captive ones. The paper presents the design and methodology of the experiments, as well as comparisons of measured loads and motions with simulations. Loads are shown to be consistent, with a good representation of the sustained non-linearities. Pitch and heave motions depict an encouraging correlation which confirms that the modeling approach is valid.

Foot Macrodactyly Associated with Klippel-Trenaunay Syndrome

2021 ◽  
Vol 23 (5) ◽  
pp. 375-380
Author(s):  
Maurizio De Pellegrin ◽  
Désirée Moharamzadeh ◽  
Giacomo Placella ◽  
Vincenzo Salini
Keyword(s):  
Functional Outcome ◽  
Congenital Malformation ◽  
Patient’S Satisfaction ◽  
Length Difference ◽  
Custom Made ◽  
The Difference ◽  
The Right ◽  
Klippel Trenaunay Syndrome

Klippel-Trenaunay syndrome is a rare congenital malformation which may be associated with macrodactyly. The main problem is the need for custom-made shoes. We describe the case of a female newborn affected by Klippel-Trenaunay syndrome, with a larger and longer right foot; the difference increased progressively and, at 5 years of age, the right foot was 50% larger and 38% longer than the left one. Due to the progression of the deformity, reduction surgery was advised to reduce the foot’s width. Resection of the second ray and 2nd cuneiform was performed. The result was excellent and there were no complications during a 10-year follow-up period with a decrease of width and length difference to 10% and 4%, respectively, in comparison to the contralateral foot. There were no gait anomalies. Abnormal foot width and length represented the main problems and guided the surgical strategy. Second ray resection was effective, without complications and with a good long-term functional outcome. Possibility of wearing fashionable conventional shoes without insoles was achieved to the patient’s satisfaction

Upwind Sail Performance Prediction for a VPP including “Flying Shape” Analysis

2009 ◽  
Author(s):  
Brian Maskew ◽  
Frank DeBord
Keyword(s):  
Grid Point ◽  
Flow Simulation ◽  
Lattice Method ◽  
Prediction Program ◽  
Aerodynamic Pressure ◽  
Dynamic Velocity ◽  
Velocity Prediction ◽  
Coupled Structures ◽  
And Performance ◽  
Ultimate Objective

A coupled aerodynamic/structures approach is presented for predicting the flying shape and performance of yacht sails in upwind conditions. The method is incorporated in a flow simulation computer program, and is part of an ultimate objective for a simultaneous aeroelastic/hydro analysis in a Dynamic Velocity Prediction Program (DVPP), that will include a 6DOF motion solver, and at some point could include calculations in waves. The time-stepping aerodynamic module uses an advanced vortex lattice method for the sails and a panel method with special base separation treatment to represent the abovewater part of the hull and mast. A coupled inverse boundary layer analysis is applied on all surfaces including both sides of each sail membrane; this computes the skinfriction drag and the source displacement effects of the boundary layers and wakes, including bubble and leeside “trailing-edge” type separations. . At each step, the computed aerodynamic pressure and skin-friction loads are transferred to a coupled structures module that uses a network grid of tension “cords” in each sail membrane, each cord representing a collection of fiber “strings”. The solution of a structural equilibrium matrix provides the displacements needed to achieve balance between the aerodynamic and tension loads at each grid point as the shape iterations proceed. Details of the methodology used are presented and comparisons of predicted aerodynamic forces to wind tunnel results and an existing VPP sail model are provided. In addition, predictions are compared to some simple experiments to demonstrate the aerodynamic/structural coupling necessary to predict flying shape. Finally, an outline is given for incorporation of this methodology into the planned Dynamic Velocity Prediction Program.

Effects of Ice Thickness on the Aerodynamic Characteristics of Crescent Shape Iced Conductors

2012 ◽  
Vol 166-169 ◽  
pp. 2696-2703 ◽  
Author(s):  
Dong Yan ◽  
Wen Juan Lou ◽  
Ming Feng Huang ◽  
Wei Lin
Keyword(s):  
Lift Force ◽  
Aerodynamic Force ◽  
Wind Tunnel Test ◽  
Aerodynamic Characteristics ◽  
Ice Thickness ◽  
Force Curve ◽  
Force Coefficients ◽  
Variation Patterns ◽  
The Difference ◽  
Force Characteristics

Aerodynamic characteristics of iced conductors were investigated by the wind tunnel test. Under the homogeneous turbulence of 5% intensity, aerodynamic force coefficients of single and bundled conductors were obtained at wind angles of 0°~180°. The variation patterns of aerodynamic forces on the iced conductors with respect to wind angels of attack were systematically studied for the ice thickness of 0.25, 0.5, 0.75 and 1 times of the conductor diameter. The difference of aerodynamic force characteristics for single and bundled conductors were identified and discussed. Based on the Den Hartog and Nigol’s mechanisms of galloping, the wind angle ranges sensitive to galloping were analyzed. The results show that lift and torsion force coefficients reach peak values at wind angles of 15°~20°. For bundled conductors, lift force curve is approximately agreed with the curve of single conductor. Drag force coefficients were smaller than these of single conductor at some wind angles. There are noticeably differences of torsion coefficients existed between bundled conductors and single conductor. According to two classical galloping mechanisms, wind angles of 15°~30°are critical for the galloping of iced conductors with crescent shapes.

scholarly journals Force decay and dimensional changes of thermoplastic and novel thermoset elastomeric ligatures

2016 ◽  
Vol 86 (5) ◽  
pp. 818-825 ◽  
Author(s):  
Ahmed I. Masoud ◽  
Milena Bulic ◽  
Grace Viana ◽  
Ana K. Bedran-Russo
Keyword(s):  
Force Measurement ◽  
Rocky Mountain ◽  
Outer Diameter ◽  
Dimensional Changes ◽  
Time Points ◽  
Percent Change ◽  
Force Decay ◽  
Custom Made ◽  
The Difference ◽  
Student’S T

ABSTRACT Objectives:  To compare over a period of 8 weeks (1) the force decay and (2) the dimensional changes between thermoplastic (TP) and thermoset (TS) elastomeric ligatures. Materials and Methods:  TP and TS elastomeric ligatures were obtained from Rocky Mountain Orthodontics™. The TS ligatures were custom made specifically for this study. The sample included 72 clear TP and 72 clear TS elastomeric ligatures. The experiment was performed in a simulated oral environment (pH of 6.75) at 37°C. The remaining forces and the dimensional changes were measured at different time points over a period of 8 weeks. Results:  Student’s t-tests revealed significant differences in percent force loss, percent change in outer diameter, percent change in inner diameter, and percent change in wall thickness between TP and TS elastomeric ligatures across all time points (P < .001). The difference in percent change in width between TP and TS elastomeric ligatures was not significant at all time points (P > .05). The mean difference in force loss between TP and TS across all time points was 22.91%. The TP and TS specimens exhibited 93.04% and 77.41% force loss, respectively, at the 28th day. Conclusions:  This novel TS elastomeric ligature showed significantly less force decay and dimensional changes over time; therefore, it might be superior during initial leveling and aligning and during finishing stages. Using a transfer jig to prevent relaxation of the specimens before force measurement showed that force decay of commercially available elastomeric ligatures was greater than that described in previous publications.

scholarly journals Effect of Angle of Attack on Airfoil NACA 0012 Performance

2020 ◽  
Vol 5 (1) ◽  
pp. 35-40
Author(s):  
Ali Akbar
Keyword(s):  
Fluid Flow ◽  
Wind Speed ◽  
Wind Tunnel ◽  
Lift Force ◽  
Angle Of Attack ◽  
Lower Surface ◽  
Wind Tunnel Experiments ◽  
A Value ◽  
The Difference ◽  
Naca 0012

Airfoil is an aerodynamic form intended to produce a lift force with the smallest drag force. When an airfoil is passed through a fluid flow that causes interaction between the air flow and the surface, variations in velocity and pressure will occur along the top and bottom surfaces of the airfoil, as well as the front and back of the airfoil. The difference in pressure between the upper and lower surface of the airfoil is what causes the resultant force in the direction perpendicular to the direction of fluid flow, this force is called the lift force (lift). In this experiment NACA 0012 airfoil experiments have been carried out using simple wind tunnel. Experiments were conducted with the aim to determine the effect of the angle of attack on the performance of the NACA 0012 airfoil which then analyzed the lift force of the NACA 0012 airfoil. The variation of the angle of attack used was 0 °, 3 °, 6 °, 9 °, 12 °, and 15 ° and used wind speed of 21.5 m / s. The greatest lift force is obtained at an angle of attack of 9 ° with a value of 0.981 while the largest lifting coefficient with a value of 0.106. The greater the angle of attack the greater the airfoil lift force, but for symmetrical airfoil stall at an angle that is too large

scholarly journals Comparative Study of Construction/Flat Patterns and Grading Patterns Application in Clothing Making: A Case Study on Women’s Clothing Practices

2020 ◽  
Vol 2 (12) ◽  
Author(s):  
Marniati Marniati
Keyword(s):  
Design Education ◽  
Research Subjects ◽  
Study Program ◽  
Significance Level ◽  
Factorial Anova ◽  
Women's Clothing ◽  
Undergraduate Study ◽  
Custom Made ◽  
Speed Up ◽  
The Difference

This study aimed to measure the implementation of the practice in the women’s clothing course in terms of the skill variable making construction/flat clothing patterns, applying the grading pattern and making women’s clothing. This study used a quantitative approach. The research subjects were all students who programmed the women’s clothing course. 43 students of the UNESA Fashion Design Education undergraduate study program. Data analysis used 2x4 factorial ANOVA followed by a comparison of the mean using SPSS software. The honest real difference test (Tukey test) was used to test the difference between the two data at the 5% significance level. Observations were made on two things, namely the length of time for making patterns and clothes, on industrial and custom-made clothing. Industrial clothing consists of one-pieces, blouses/tunics, skirts, and pants, while costume-made clothing consists of deuce pieces, long dresses, short dresses, and modern kebaya. The method of making patterns reads into two ways, namely flat and grading. The results showed that the grading method can speed up the time for making industrial and custom-made clothing patterns. The manufacture of one-piece industry clothing takes longer than others. Meanwhile, the long costume-made dress takes longer than the others

Improving folding properties of computationally designed proteins

2019 ◽  
Vol 32 (3) ◽  
pp. 145-151
Author(s):  
Benjamin Bjerre ◽  
Jakob Nissen ◽  
Mikkel Madsen ◽  
Jūratė Fahrig-Kamarauskaitė ◽  
Rasmus K Norrild ◽  
...  
Keyword(s):  
Amino Acid ◽  
Protein Design ◽  
Genetic Selection ◽  
Single Amino Acid ◽  
Structured Design ◽  
Designed Proteins ◽  
Improved Stability ◽  
The Difference ◽  
Essential Enzyme ◽  
Selection Of

Abstract While the field of computational protein design has witnessed amazing progression in recent years, folding properties still constitute a significant barrier towards designing new and larger proteins. In order to assess and improve folding properties of designed proteins, we have developed a genetics-based folding assay and selection system based on the essential enzyme, orotate phosphoribosyl transferase from Escherichia coli. This system allows for both screening of candidate designs with good folding properties and genetic selection of improved designs. Thus, we identified single amino acid substitutions in two failed designs that rescued poorly folding and unstable proteins. Furthermore, when these substitutions were transferred into a well-structured design featuring a complex folding profile, the resulting protein exhibited native-like cooperative folding with significantly improved stability. In protein design, a single amino acid can make the difference between folding and misfolding, and this approach provides a useful new platform to identify and improve candidate designs.

Comparisons Between Prediction and Experiment for Lift Force and Heel Moment for a Planing Hull

2013 ◽  
Vol 29 (01) ◽  
pp. 36-46
Author(s):  
Carolyn Q. Judge
Keyword(s):  
High Speed ◽  
Lift Force ◽  
Forward Speed ◽  
Dynamic Effects ◽  
Planing Craft ◽  
Underwater Photography ◽  
Calm Water ◽  
Transverse Stability ◽  
The Relationship ◽  
Righting Moment

Even in calm water, high-speed vessels can display unstable behaviors such chine walking, sudden large heel, and porpoising. Large heel results from the loss of transverse stability at high forward speed. When a planing craft begins to plane, the hydrodynamic lift forces raise the hull out of the water. The available righting moment resulting from the hydrostatic buoyancy is, therefore, reduced. As the righting moment resulting from hydrostatic buoyancy is reduced, the righting moment resulting from dynamic effects becomes important. These hydrodynamic righting effects are related to the hydrodynamic lift. This article explores the relationship between the hydrostatic lift and righting moment, the hydrodynamic lift and righting moment, and the total lift and heel-restoring moment of a planing craft operating at planing speeds. A series of tow tests using a prismatic hull with a constant deadrise of 20 measured the lift force and righting moment at various angles of heel and at various model velocities. The model was completely constrained in surge, sway, heave, roll, pitch, and yaw. The underwater volume is determined from the known hull configuration and the underwater photography of the keel and chine wetted lengths. The results presented include the total lift and righting moment with the hydrostatic and hydrodynamic contributions for various model speeds at two model displacements.

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