ON JONES' CRITERION FOR THIN WINGS OF MINIMUM DRAG

1954 ◽  
Author(s):  
R. SEDNEY
Keyword(s):  
Minimum Drag ◽  
Jones Criterion

scholarly journals Effect of Cutting Ratio and Catch on Drag Characteristics and Fluttering Motions of Midwater Trawl Codend

2021 ◽  
Vol 9 (3) ◽  
pp. 256
Author(s):  
Wei Liu ◽  
Hao Tang ◽  
Xinxing You ◽  
Shuchuang Dong ◽  
Liuxiong Xu ◽  
...  
Keyword(s):  
Drag Force ◽  
Mesh Size ◽  
Current Speed ◽  
Midwater Trawl ◽  
Minimum Drag ◽  
Fish Catch ◽  
Spatial Geometry ◽  
By Catch ◽  
Trawl Fisheries ◽  
Crucial Part

The codend of a trawl net is the rearmost and crucial part of the net for selective fish catch and juvenile escape. To ensure efficient and sustainable midwater trawl fisheries, it is essential to better understand the drag characteristics and fluttering motions of a midwater trawl codend. These are generally affected by catch, cutting ratio, mesh size, and twine diameter. In this study, six nylon codend models with different cutting ratios (no cutting, 6:1, 5:1, 4:1, 7:2, and 3:1) were designed and tested in a professional flume tank under two conditions (empty codends and codends with catch) and five current speeds to obtain the drag force, spatial geometry, and movement trend. As the cutting ratio of empty codends decreased, the drag force decreased, and the drag coefficient increased. The unfolding degree of codend netting and the height of empty codends were found to be directly proportional to the current speed and inversely proportional to the cutting ratio. The positional amplitude of codend with cutting ratio 4:1 was the smallest for catch. The drag force of codends with catch increased as the current speed increased, and first decreased and then increased as the cutting ratio decreased. To ensure the best stability and minimum drag force of the codend, it is recommended to use the 4:1 cutting ratio codend.

scholarly journals First Integrals, Integrating Factors, and Invariant Solutions of the Path Equation Based on Noether and -Symmetries

2013 ◽  
Vol 2013 ◽  
pp. 1-15 ◽  
Author(s):  
Gülden Gün ◽  
Teoman Özer
Keyword(s):  
Governing Equation ◽  
First Integrals ◽  
Invariant Solutions ◽  
Group Invariant ◽  
Minimum Drag ◽  
Symmetry Properties ◽  
Group Invariant Solutions ◽  
Work First ◽  
Partial Lagrangian ◽  
Integrating Factors

We analyze Noether and -symmetries of the path equation describing the minimum drag work. First, the partial Lagrangian for the governing equation is constructed, and then the determining equations are obtained based on the partial Lagrangian approach. For specific altitude functions, Noether symmetry classification is carried out and the first integrals, conservation laws and group invariant solutions are obtained and classified. Then, secondly, by using the mathematical relationship with Lie point symmetries we investigate -symmetry properties and the corresponding reduction forms, integrating factors, and first integrals for specific altitude functions of the governing equation. Furthermore, we apply the Jacobi last multiplier method as a different approach to determine the new forms of -symmetries. Finally, we compare the results obtained from different classifications.

BODY DRAG, FEATHER DRAG AND INTERFERENCE DRAG OF THE MOUNTING STRUT IN A PEREGRINE FALCON,FALCO PEREGRINUS

1990 ◽  
Vol 149 (1) ◽  
pp. 449-468 ◽  
Author(s):  
VANCE A. Tucker
Keyword(s):  
The Body ◽  
Peregrine Falcon ◽  
Reference Area ◽  
Drag Coefficients ◽  
Minimum Drag ◽  
Body Drag ◽  
The Mean ◽  
The Difference ◽  
Parabuteo Unicinctus ◽  
Crosssectional Area

1. The mean, minimum drag coefficients (CD,B) of a frozen, wingless peregrine falcon body and a smooth-surfaced model of the body were 0.24 and 0.14, respectively, at air speeds between 10.0 and 14.5 ms−1. These values were measured with a drag balance in a wind tunnel, and use the maximum crosssectional area of the body as a reference area. The difference between the values indicates the effect of the feathers on body drag. Both values for CD,B a r e lower than those predicted from most other studies of avian body drag, which yield estimates of CD,B up to 0.41. 2. Several factors must be controlled to measure minimum drag on a frozen body. These include the condition of the feathers, the angle of the head and tail relative to the direction of air flow, and the interference drag generated by the drag balance and the strut on which the body is mounted. 3. This study describes techniques for measuring the interference drag generated by (a) the drag balance and mounting strut together and (b) the mounting strut alone. Corrections for interference drag may reduce the apparent body drag by more than 20%. 4. A gliding Harris' hawk (Parabuteo unicinctus), which has a body similar to that of the falcon in size and proportions, has an estimated body drag coefficient of 0.18. This value can be used to compute the profile drag coefficients of Harris' hawk wings when combined with data for this species in the adjoining paper (Tucker and Heine, 1990).

scholarly journals A Novel Control Allocation Method for Yaw Control of Tailless Aircraft

Aerospace ◽  
2020 ◽  
Vol 7 (10) ◽  
pp. 150
Author(s):  
Thomas R. Shearwood ◽  
Mostafa R. A. Nabawy ◽  
William J. Crowther ◽  
Clyde Warsop
Keyword(s):  
Control Allocation ◽  
Rolling Moment ◽  
Aerodynamic Efficiency ◽  
Yaw Control ◽  
Induced Drag ◽  
Minimum Drag ◽  
Allocation Method ◽  
Control Authority ◽  
And Control ◽  
Tailless Aircraft

Tailless aircraft without vertical stabilisers typically use drag effectors in the form of spoilers or split flaps to generate control moments in yaw. This paper introduces a novel control allocation method by which full three-axis control authority can be achieved by the use of conventional lift effectors only, which reduces system complexity and control deflection required to achieve a given yawing moment. The proposed method is based on synthesis of control allocation modes that generate asymmetric profile and lift induced drag whilst maintaining the lift, pitching moment and rolling moment at the trim state. The method uses low order models for aerodynamic behaviour characterisation based on thin aerofoil theory, lifting surface methodology and ESDU datasheets and is applied to trapezoidal wings of varying sweep and taper. Control allocation modes are derived using the zero-sets of surrogate models for the characterised aerodynamic behaviours. Results are presented in the form of control allocations for a range of trimmed sideslip angles up to 10 degrees optimised for either maximum aerodynamic efficiency (minimum drag for a specific yawing moment) or minimum aggregate control deflection (as a surrogate observability metric). Outcomes for the two optimisation objectives are correlated in that minimum deflection solutions are always consistent with efficient ones. A configuration with conventional drag effector is used as a reference baseline. It is shown that, through appropriate allocation of lift based control effectors, a given yawing moment can be produced with up to a factor of eight less aggregate control deflection and up to 30% less overall drag compared to use of a conventional drag effector.

Centre of Pressure of Cowl Shapes Having Minimum Drag in Supersonic Flow

1965 ◽  
Vol 69 (657) ◽  
pp. 636-637
Author(s):  
D. J . Carey
Keyword(s):  
Supersonic Flow ◽  
Close Correlation ◽  
Centre Of Pressure ◽  
Newtonian Flow ◽  
Pressure Distributions ◽  
Minimum Drag

Formulae are presented giving the centre of pressure of axi-symmetric bodies at zero incidence having profiles for which the drag is a minimum in Newtonian flow.Boyd has suggested that a close correlation may exist between such profiles, and profiles derived from exact pressure distributions, in supersonic flow.

Sign in / Sign up

Export Citation Format

Share Document