• Journal of Advanced Marine Engineering and Technology
• /
• v.34 no.5
• /
• pp.718-724
• /
• 2010

This paper studies the differences due to the wall effect in propeller open water(POW) characteristics tested in a towing tank and in a medium size cavitation tunnel(CT). When the advanced velocity of the propeller is defined as the flow velocity measured in the plane of propeller, POW characteristics resulting from CT has a better relationship with them of towing tank. To obtain the wall effect in the propeller plane, numerical computation using the lifting panel theory is performed with and without the wall around a propeller. Then, POW results in CT are corrected based on the wall effect from numerical results. The POW results obtained from this procedure show a better agreement with the experimental results in the towing tank.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.7
• /
• pp.509-515
• /
• 2013

In this study, the real-coded adaptive range multi-objective genetic algorithm code, which represents the global multi-objective optimization algorithm, was developed for an airfoil shape design. In order to achieve the better aerodynamic characteristics than reference airfoil at landing and cruise conditions, maximum lift coefficient and lift-to-drag ratio were chosen as object functions. Futhermore, the PARSEC method reflecting geometrical properties of airfoil was adopted to generate airfoil shapes. Finally, two airfoils, which show better aerodynamic characteristics than a reference airfoil, were chosen. As a result, maximum lift coefficient and lift-to-drag ratio were increased of 4.89% and 5.38% for first candidate airfoil and 7.13% and 4.33% for second candidate airfoil.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.7
• /
• pp.655-663
• /
• 2010

DUP (direct underside pressurization) is a device that can considerably increase lift, reduce take-off speed and minimize hump drag when a WIG effect vehicle takes off on the water surface. A 3-dimensional numerical investigation of a WIG effect vehicle with DUP is performed to analyze aerodynamic characteristics and the static height stability. The model vehicle, named Aircat, consists of a propeller in the middle of a fuselage, an air chamber under the fuselage, Lippisch-type wings and a large horizontal T-tail. The lift is mainly increased by the stagnation of the accelerated air coming into the air chamber through the channel in the middle of the fuselage. However, the accelerated air increases drag as well as reduces static height stability.

• Journal of the Society of Naval Architects of Korea
• /
• v.37 no.3
• /
• pp.57-68
• /
• 2000

The Power Augmented Ram(PAR) effect, which blows the down stream of the propellers into the underside of the wings and hence increases the pressure between the lower surface of the wings and the sea surface, is known significantly to enhance the performance of the WIG concept by reducing the take-off and landing speeds. The aerodynamic characteristics of a 20 passenger PARWIG are investigated by wind tunnel tests with the 1/20 scale model. The efflux of the forward mounted propellers are simulated by jet flows with a blower and duct system. The lift, drag, and pitch moment of the model with various ground clearances, angles of attack and flap angles are measured for the various jet velocities, jet nozzle angles, horizontal and vertical positions of the nozzle, and the nozzle diameters. The aerodynamic characteristics of the PARWIG due to these parametric changes are compared and pertinent discussions are included. It is shown that the proper use of the PAR can increase the lift coefficient of as much as up to 4.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.40 no.10
• /
• pp.846-852
• /
• 2012

The present paper is the preliminary study of the development of a morphing aircraft wing and investigates experimently the aerodynamic characteristics of a base airfoil and a morphing airfoil. The wind tunnel tests are conducted for a base Clark-Y airfoil, an airfoil with a mechanical flap, and a morphing airfoil. Lifts, drags, and pitching moments are measured by using a three-axis load cell and they are calibrated by considering solid blockage and wake blockage. The wind tunnel tests are conducted for various air speeds, Reynolds' numbers, and angles of attack. The experimental results show that the aerodynamic characteristics of the morphing airfoil in lift-drag and lift-pitching moment are better than those of the airfoil with a mechanical flap.

• Journal of the Society of Naval Architects of Korea
• /
• v.34 no.1
• /
• pp.60-67
• /
• 1997

This paper presents the results of 3rd wind tunnel test for the wings of WIG R/C test models, 'Hanjin-1' & 'Hanjin-2'. We made 'Hanjin-1' in last May 1995 and had a success in test flight. And in order to grasp the aerodynamic characteristics of wings in ground effect, the measurements of lift and drag were carried out for the various kinds of wing. It was shown that lift and lift-drag ratio increase with decrease of the clearance, but the feature was considerably depended on the shape of wing section. In this case we select the three kind of wing. section, and then compare their characteristics especially for a stability in longitudinal motion. They are NACA6409 for 'Hanjin-1' and the two kinds of DHMTU for ekranoplans of Russia. Experimental results show that the pitching moments of DHMTU wing sections are smaller than NACA6409.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.11
• /
• pp.978-983
• /
• 2015

A study on the speed limit and sizing of auxiliary fixed-wing of compound gyroplane was performed. The performance of the plane that uses the same rotor system and power of BO-105 helicopter was compared with that of BO-105 helicopter. The wing area which is used to compensate in lift, was calculated considering the aerodynamic characteristics and lift sharing ratio of the rotor. Achievable flight speeds were observed for two types of fuselage; BO-105 and streamlined bodies. The study showed that the autorotating rotor can share 1/2 of lift at high speed and the parasite power of compound gyroplane having streamlined body and small wing can be minimized, accordingly it can fly faster than helicopter with airspeed more than twice.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.36 no.1
• /
• pp.20-36
• /
• 2024

In this study, probabilistic models for the wave- and lifting forces were derived directly from long-term in-situ wave data embedding the Korean marine environment characteristics varying from sea to sea based on the Three-Parameter Weibull distribution. Korean marine environment characteristics varying from sea to sea carved out their presence on the probability coefficients of probabilistic models for wave- and lifting forces. Energetic wave conditions along the southern coast of Korea distinguish themselves from the others with a relatively large scale coefficient, small location coefficient, and shape coefficient around 1.3. On the other hand, mild marine environment along the western coast has a small variability, leading to small scale-coefficient, large location coefficient and shape coefficient around 2.0. In the sea off Mokpo, near the boundary between the South- and West Seas, marine environment was characterized by small scale-coefficient, large location coefficient, and shape coefficient around 1.2, implying that marine environments characteristics of the South-and West Sea coexist in the sea off Mokpo.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.3
• /
• pp.6-13
• /
• 2006

Aerodynamic characteristics for two-dimensional cyclic motion profile of flapping airfoil in low Reynolds number flows are investigated. Plunging motion and lead-lag motion in the two dimensional space with different plunging and lead-lag amplitudes are combined to cyclic motion profile and the flow around the airfoil is simulated. Present result shows that the improved aerodynamic efficiencies for a given flapping airfoil by adding periodic lead-lag motion of airfoil rather than the pure plunging case. The thrust coefficient and lift coefficient are compared with each cycle during the flapping period and aerodynamic characteristics are obtained on upstroke motion and downstroke motion.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.5
• /
• pp.390-396
• /
• 2007

In the present study, we have developed a flapping wing using a smart material to mimic the nature's flyers, birds. The wing consists of composite frames, a flexible PVC film and a surface actuator, and the main wing motions are flapping, twisting and camber motions. To change the camber, a Macro-Fiber Composite(MFC) is used as the surface actuator, and it's structural response is analyzed by the use of piezoelectric-thermal analogy. To measure the lift and thrust simultaneously, a test stand consisting of two load cells is manufactured. Some aerodynamic tests are performed for the wing in a subsonic wind tunnel to evaluate the dynamic characteristics. Experimental results show that the main lift is mostly affected by the forward velocity and the pitch angle, but the thrust is mostly affected by the flapping frequency. The effect of the camber generated by the MFC actuator can produce the sufficient lift increment of up to 24.4% in static condition and 20.8% in dynamic condition.