Supercavitating Foils With Flaps Beneath a Free Surface

1964 ◽  
Vol 86 (2) ◽  
pp. 197-204
Author(s):  
J. Auslaender
Keyword(s):  
Free Surface ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Cavitation Number ◽  
Operating Conditions ◽  
Mapping Technique ◽  
Moment Coefficient ◽  
Lift Curve ◽  
Flap Deflection ◽  
Drag Ratio

Linearized airfoil theory—in conjunction with a mapping technique—is applied to the calculation of the forces and moments acting on supercavitating hydrofoils operating near a free surface at very large Froude numbers and zero cavitation number. Only the effects of angle of attack and flap deflection are considered. The results—intended for engineering use—are presented primarily in the form of curves of flap effectiveness, lift curve slope, pitching and hinge moment coefficient, and flap loading versus flap-chord ratio, depth being introduced as a parameter. Lift-drag ratio and hinge moment coefficient as functions of lift coefficient are presented for typical operating conditions.

scholarly journals Study of board bending degree on hydrodynamic performances of a single-layer cambered otter-board

2019 ◽  
Vol 131 ◽  
pp. 01120
Author(s):  
Lei Wang ◽  
Lu Min Wang ◽  
Yong Li Liu ◽  
Wen Wen Yu ◽  
Guang Rui Qi ◽  
...  
Keyword(s):  
Center Of Pressure ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Angle Of Attack ◽  
Single Layer ◽  
Moment Coefficient ◽  
Pitch Moment ◽  
Engineering Models ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The effect of board bending degree on hydrodynamic performances of a single-layer cambered otter-board was investigated using engineering models in a wind tunnel. Three different bending degree boards were evaluated at a wind speed of 28 m/s. Parameters measured included: drag coefficient Cx, lift coefficient Cy, pitch moment coefficient Cm, center of pressure coefficient Cp , over a range of angle of attack (0° to 70°). These coefficients were used in analyzing the differences in the performance among the three otter-board models. Results showed that the bending of the board(No. 2, No. 3) increased the water resistance of the otter-board, and improved the lift coefficient of the otter-board in the small angle of attack (0°<α≤20 °) ; the maximum lift coefficients Cy of otter-board model (No. 1) was higher (1.680, α = 25°). the maximum lift–drag ratios of models (No. 1, No. 2 and No. 3) are 6.822 (α = 7.5 °), 6.533 (α = 2.5 °) and 6.384 (α = 5.0°), which showed that the board bending reduces the lift-to-drag ratio of the otter-board.The stability of the No. 3 model was better than those two models (No. 1, No. 2) in most range of attack angle, but No. 1 otter-board model had a better stability in roll of otter-board. The findings of this study can offer useful reference data for the structural optimization of otter-boards for trawling.

scholarly journals Aerodynamic and Vibration Characteristics of the Micro-Octocopter at Low Reynolds Number

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Xiaohua Zou ◽  
Mingsheng Ling ◽  
Wenzheng Zhai
Keyword(s):  
Reynolds Number ◽  
Load Capacity ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Aerodynamic Characteristics ◽  
Vibration Characteristics ◽  
Low Reynolds ◽  
Vibration Performance ◽  
Drag Ratio ◽  
Lift To Drag Ratio

With the development of flight technology, the need for stable aerodynamic and vibration performance of the aircraft in the civil and military fields has gradually increased. In this case, the requirements for aerodynamic and vibration characteristics of the aircraft have also been strengthened. The existing four-rotor aircraft carries limited airborne equipment and payload, while the current eight-rotor aircraft adopts a plane layout. The size of the propeller is generally fixed, including the load capacity. The upper and lower tower layout analyzed in this paper can effectively solve the problems of insufficient four-axis load and unstable aerodynamic and vibration performance of the existing eight-axis aircraft. This paper takes the miniature octorotor as the research object and studies the aerodynamic characteristics of the miniature octorotor at different low Reynolds numbers, different air pressures and thicknesses, and the lift coefficient and lift-to-drag ratio, as well as the vibration under different elastic moduli and air pressure characteristics. The research algorithm adopted in this paper is the numerical method of fluid-solid cohesion and the control equation of flow field analysis. The research results show that, with the increase in the Reynolds number within a certain range, the aerodynamic characteristics of the miniature octorotor gradually become better. When the elastic modulus is 2.5 E, the aircraft’s specific performance is that the lift increases, the critical angle of attack increases, the drag decreases, the lift-to-drag ratio increases significantly, and the angle of attack decreases. However, the transition position of the flow around the airfoil surface is getting closer to the leading edge, and its state is more likely to transition from laminar flow to turbulent flow. When the unidirectional carbon fiber-reinforced thickness is 0.2 mm and the thin arc-shaped airfoil with the convex structure has a uniform thickness of 2.5% and a uniform curvature of 4.5%, the aerodynamic and vibration characteristics of the octorotor aircraft are most beneficial to flight.

An Extended Linearized Inverse Theory for Fully Cavitating Hydrofoil Section Design

1979 ◽  
Vol 23 (04) ◽  
pp. 260-271
Author(s):  
Blaine R. Parkin ◽  
Joe Fernandez
Keyword(s):  
Design Theory ◽  
Parametric Design ◽  
Lift Coefficient ◽  
Design Procedure ◽  
Cavitation Number ◽  
Inverse Theory ◽  
Cavity Surface ◽  
Moment Coefficient ◽  
Section Design ◽  
Cavity Thickness

A new design theory for fully cavitating hydrofoils is based upon a linearized inverse theory of two-dimensional cavity flows at arbitrary cavitation number. The cavity surfaces are assumed to originate at the leading and trailing edges of the wetted surface. This paper reviews and completes the basic theory, which leads to a parametric design technique. In the resulting design procedure, one specifies the design lift coefficient, the cavitation number and the upper cavity thickness at two points along the profile chord. A prescribed pressure distribution shape is also selected. These quantities determine the profilelesgn, which consists of the upper cavity and wetted surface contours, the design angle of attack, the cavity length, the drag coefficient, the moment coefficient and the lift-to-drag ratio. The chief new feature of the third design procedure is that the designer can now prescribe two points on the cavity surface instead of one as heretofore. Although the designer must observe certain constraints when he specifies these two values of cavity thickness, the new procedure is still found to be more general and more flexible than design procedures studied previously.

Stability Analysis of a Light Aircraft Configuration Using Computational Fluid Dynamics

2012 ◽  
Vol 225 ◽  
pp. 391-396 ◽  
Author(s):  
Mohammed Mahdi ◽  
Yasser A. Elhassan
Keyword(s):  
Numerical Simulation ◽  
Stokes Equations ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Rate Of Change ◽  
Navier Stokes ◽  
Rolling Moment ◽  
Moment Coefficient ◽  
Stability Derivatives ◽  
Lift And Drag

This work aims to simulate and study the flow field around SAFAT-01 aircraft using numerical solution based on solving Reynolds Averaged Navier-Stokes equations coupled with K-ω SST turbulent model. The aerodynamics behavior of SAFAT-01 aircraft developed at SAFAT aviation complex were calculated at different angles of attack and side slip angles. The x,y and z forces and moments were calculated at flight speed 50m/s and at sea level condition. Lift and drag curves for different angles of attack were plotted. The maximum lift coefficient for SAFAT-01 was 1.67 which occurred at angle of attack 16° and Maximum lift to drag ratio (L/D) was 14 which occurred at α=3°, and the zero lift drag coefficient was 0.0342. Also the yawing moment coefficient was plotted for different side slip angles as well as rolling moment. The longitudinal stability derivatives with respect to angle of attack, speed variation (u), rate of pitch (q) and time rate of change of angle of attack were calculated using obtained CFD results. Concerning lateral stability only side slips derivatives were calculated. To validate this numerical simulation USAF Digital DATCOM is used to analyze this aircraft; a comparison between predicted results for this aircraft and Digital DATCOM indicated that this numerical simulation has high ability for predicting the aerodynamics characteristics.

Aerodynamic Performance Comparison of Airfoils by Varying Angle of Attack Using Fluent and Gambit

2014 ◽  
Vol 592-594 ◽  
pp. 1889-1896 ◽  
Author(s):  
G. Srinivas ◽  
B.P. Madhu Gowda
Keyword(s):  
Lift Coefficient ◽  
Flow Analysis ◽  
Angle Of Attack ◽  
Vital Role ◽  
Performance Comparison ◽  
Operating Conditions ◽  
Aircraft Wing ◽  
Flow Convergence ◽  
Fluent Software ◽  
Wind Tunnel Data

Any aircraft wing is the major component which will play vital role in the generation of lift and at different maneuvering moments throughout the flight. So to maintain this good maneuverability the aircraft wing has to undergo deferent deflections called angle of attack such that the high lift and low drag or vice versa can be settled in the flight. Taking this as the motivation the analysis was carried out on the standard wing airfoil comparing with new designed airfoil. Analyze the numerical simulation values like coefficient of lift, coefficient of Drag, Lift, Drag, and Energy parameters with wind tunnel data to predict accuracy for both the airfoils. Through the selected public literature standard airfoil data and designed airfoil data has been chosen, the geometry was created in the GAMBIT and also the meshing by selecting the suitable c-grid and rectangular grid for the better flow analysis in the FLUENT. The mesh file was imported into the FLUENT software there suitable boundary conditions and operating conditions are given for successful flow convergence. Finally analyzing these results are expecting to be best suitable for good aeromechanical features.

scholarly journals Effects of Geometrical Parameters of Internal Blown Flap and Its Optimal Design

2020 ◽  
Vol 38 (1) ◽  
pp. 58-67
Author(s):  
Rui Liu ◽  
Junqiang Bai ◽  
Yasong Qiu ◽  
Guozhu Gao
Keyword(s):  
Optimal Design ◽  
Design Method ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Chord Length ◽  
Geometrical Parameters ◽  
Design Constraint ◽  
Design Variables ◽  
Flap Deflection ◽  
Stall Angle

The internal blown flap was numerically simulated. Firstly, a parameterization method was developed, which can properly describe the shape of the internal blown flap according to such geometrical parameters as flap chord length, flap deflection, height of blowing slot and its position. Then the reliability of the numerical simulation was validated through comparing the pressure distribution of the CC020-010EJ fundamental generic circulation control airfoil with the computational results and available experiment results. The effects of the geometrical parameters on the aerodynamic performance of the internal blown flap was investigated. The investigation results show that the lift coefficient increases with the increase of flap chord length and flap deflection angle and with the decrease of height of blowing slot and its front position. Lastly, a method of optimal design of the geometrical parameters of the internal blown flap was developed. The design variables include flap chord length, flap deflection, height of blowing slot and its position. The optimal design is based on maximum lift coefficient, the angle of attack of 5 degrees and the design constraint of stall angle of attack of less than 9 degrees. The optimization results show that the optimal design method can apparently raise the lift coefficient of an internal blown flap up to 1.7.

The Aerodynamics Analysis on Cambered Fuselage Model

2014 ◽  
Vol 660 ◽  
pp. 492-497
Author(s):  
Mohd Zarif bin Md Shah ◽  
Mohd Ridh bin Abu Bakar ◽  
Bambang Basuno
Keyword(s):  
Cross Section ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Circular Cross Section ◽  
Pitching Moment ◽  
Line Thickness ◽  
Moment Coefficient ◽  
Definition Of

There various factors gives influence in determining the fuselage shapes, such as the payload, cockpit, wing and tail placements or in manner up and down loading the payload for a cargo aircraft. These factors may come up the fuselage is no longer as symmetrical fuselage but represent as a cambered fuselage. As results the lift coefficient as well as its pitching moment coefficient is no longer equal to zero as the angle of attack goes to zero. Basically the manner how to determine the fuselage aerodynamics characteristics for cambered fuselage can be done in similar way as in the case of symmetrical fuselage by simply replacing the angle of attack α term with (α-αL=0), where αL=0 represent the angle of attack at zero lift. The present work use a similar manner in determining the zero lift angle of attack as it had been used in DATCOM software. To investigate the effect of camber on the aerodynamics characteristic fuselage, the present work use a fuselage model with a circular cross section where the location of center of the circle placed along the fuselage’s camber line. The fuselage’s camber line defined according to the definition of camber line of NACA airfoils. Aerodynamics analysis on over various fuselage models indicate that the maximum camber line thickness and their position give a significant influent to the fuselage aerodynamics characteristics.

Hydrodynamic Trends from a Generalized Design Procedure for Fully Cavitating Hydrofoil Sections

1979 ◽  
Vol 23 (04) ◽  
pp. 272-283
Author(s):  
Blaine R. Parkin ◽  
Joe Fernandez
Keyword(s):  
Parametric Design ◽  
Lift Coefficient ◽  
Design Procedure ◽  
Feasibility Studies ◽  
Cavitation Number ◽  
Hydrodynamic Performance ◽  
Cavity Surface ◽  
Cavity Flows ◽  
Moment Coefficient ◽  
Cavity Thickness

An extended design procedure for fully cavitating hydrofoils is based upon a linearized inverse theory of two-dimensional cavity flows at arbitrary cavitation number. The cavity surfaces are assumed to originate at the leading and trailing edges of the wetted surface. This paper completes the basic theory and gives detailed examples obtained from the resulting parametric design technique. In this procedure, one specifies the design lift coefficient, the cavitation number and the upper cavity thickness at two points along the profile chord. A prescribed pressure distribution shape is also selected. These quantities determine the profile design, which consists of the upper cavity and wetted surface contours, the design angle of attack, the cavity length, the drag coefficient, the moment coefficient and the lift-to-drag ratio. The method also includes off-design calculations in accordance with the direct theory of cavity flows, which determines the flow states for which interference can occur between the upper surface of the cavity and the upper nonwetted surface of the profile. The hydrodynamic performance of specific "point designs" is also given by these direct calculations. The chief new feature of the generalized design procedure is that it gives a designer the ability to prescribe two points on the cavity surface instead of one as heretofore. Although certain constraints must be observed by the designer when specifying these two values of cavity thickness, the third procedure is found to be more general and more flexible than design procedures studied previously. The necessary constraints are incorporated in the computer logic for the method. The fact that linearized theory is used tends to limit the applicability of the method to conceptual design and feasibility studies. The computer program for the procedure has been found to be economical and well suited for its intended purpose.

Analysing and Optimizing the Aerodynamic Performance of Wind Turbine Blades Using Injected-Air Jets at Variable Frequency and Amplitude for Flow Control

2005 ◽  
Vol 29 (4) ◽  
pp. 331-339 ◽  
Author(s):  
Liu Hong ◽  
Huo Fupeng ◽  
Chen Zuoyi
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Suction Surface ◽  
Air Jet

Optimum aerodynamic performance of a wind turbine blade demands that the angle of attack of the relative wind on the blade remains at its optimum value. For turbines operating at constant speed, a change in wind speed causes the angle of attack to change immediately and the aerodynamic performance to decrease. Even with variable speed rotors, intrinsic time delays and inertia have similar effects. Improving the efficiency of wind turbines under variable operating conditions is one of the most important areas of research in wind power technology. This paper presents findings of an experimental study in which an oscillating air jet located at the leading edge of the suction surface of an aerofoil was used to improve the aerodynamic performance. The mean air-mass flowing through the jet during each sinusoidal period of oscillation equalled zero; i.e. the jet both blew and sucked. Experiments investigated the effects of the frequency, momentum and location of the jet stream, and the profile of the turbine blade. The study shows significant increase in the lift coefficient, especially in the stall region, under certain conditions. These findings may have important implications for wind turbine technology.

A Bat-Wing Aircraft Using the Smart Joint Mechanism

2008 ◽  
Vol 58 ◽  
pp. 41-46 ◽  
Author(s):  
Emily Leylek ◽  
Justin Manzo ◽  
Ephrahim Garcia
Keyword(s):  
Lift Coefficient ◽  
Angle Of Attack ◽  
Joint Mechanism ◽  
Bat Wing ◽  
Drag Ratio ◽  
Lifting Line ◽  
Lift To Drag Ratio ◽  
Line Analysis

A bat-like aircraft is proposed, using a smart joint mechanism to actuate the morphing of the wings. The smart joint stays in its deformed shape after cooling, which can be up to 5% of 25 mm length joint. The morphing of the wing shapes of three different bat species is evaluated using a planar lifting line analysis. The morphing improves the lift coefficient over 1000% and the lift to drag ratio over 300% at an angle of attack of 0.6°. The results compare well with what is expected from the type of flight and morphology that has been documented for the bats.

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