Investigation of a Light Boxplane Model Using Tuft Flow Visualization and CFD

In this paper, we addressed the flow patterns over a light boxplane scale model to explain the previously discovered disagreement between its predicted and experimental aerodynamic characteristics. By tuft flow and CFD visualization, we explored the causes yielding a large zero lift pitching moment coefficient, lateral divergence, difference in fore and aft elevator lift, and poor high lift performance of the aircraft. The investigation revealed that the discrepancy in the pitching moment coefficient and lateral stability derivatives can be attributed to insufficient accuracy of the used predictive methods. The difference in fore and aft elevator lift and poor high lift performance of the aircraft may occur due to the low local Reynolds number, which causes the early flow separation over the elevators and flaperons when deflected downward at angles exceeding 10°. Additionally, some airframe changes are suggested to alleviate the lateral divergence of the model.

Download Full-text

Experimental Investigation of the Ground Effect of WIG Craft—NEW1 Model

Proceedings ◽

10.3390/proceedings2019039017 ◽

2020 ◽

Vol 39 (1) ◽

pp. 17

Author(s):

Sakornsin ◽

Thipyopas ◽

Atipan

Keyword(s):

Lift Coefficient ◽

Ground Surface ◽

Ground Effect ◽

Aerodynamic Characteristics ◽

Scale Model ◽

Negative Slope ◽

Stream Velocity ◽

Longitudinal Stability ◽

Moment Coefficient ◽

The Moment

Navy Experimental Wing-in-Ground-Effect (WIG) craft namely as NEW1, is the first version of 2-seated WIG craft which has been designed and developed by Royal Thai Navy since 2017. This experimental research is a part of the NEW1 project which aims to investigate the aerodynamic characteristics and aspects of the flow passing through the WIG craft model when in ground effect. In the experiment, the WIG craft—NEW1 of 1:15 scale model is tested in a close circuit wind tunnel of 1 m × 1 m test section at Kasetsart University. The tests are conducted at the free stream velocity of 40 m/s or Reynolds number of 280,000, at angles of attack ranging from −9° to 21°, and at the wing to ground distances ranging from 5.0 C to 0.3 C. The measurement of 6-DoF of forces and moments and pressure distributions on the ground surface underneath the WIG craft model are made during the tests. The results show that the ground has significant effects on the aerodynamic characteristics of the WIG craft model when the wing to ground distance is less than its mean chord. It was found that when the model move from 5.0 C (out of ground effect) to 0.3 C, the lift coefficient increases up to 15.7%, the drag coefficient decreases up to 5.6%, and the lift to drag ratio increases 33.4%. The proximity of the model to the ground also affects the longitudinal stability of the model. The moment coefficient curves against angle of attack has negative slope for both in and out of ground effect indicating favorable longitudinal stability. However, it was found that the aerodynamic center move further aft toward the trailing edge when the model move closer to the ground.

Download Full-text

Calculation of aerodynamic characteristics of flying objects using Prodas and Fluent environments

Mechanik ◽

10.17814/mechanik.2017.7.82 ◽

2017 ◽

Vol 90 (7) ◽

pp. 591-593

Author(s):

Leszek Baranowski ◽

Michał Frant

Keyword(s):

Mach Number ◽

Experimental Method ◽

Drag Force ◽

Lift Force ◽

Incidence Angle ◽

Theoretical Method ◽

Aerodynamic Characteristics ◽

Pitching Moment ◽

Force Coefficient ◽

Moment Coefficient

The article presents the methodology of determining the basic aerodynamic characteristics using the Fluent theoretical method and the theoretical and experimental method using the Prodas program. Presented calculations were made for a 122 mm non-guided missile. In order to compare both methods, the results of calculations of coefficient of drag force, lift force coefficient and pitching moment coefficient as a function of incidence angle of attack and Mach number are shown in graphs.

Download Full-text

Numerical Investigation on Aerodynamic Characteristics of Damaged Infinite Wings With Variation in Penetration Angle

Journal of Aerospace Technology and Management ◽

10.5028/jatm.v12.1125 ◽

2020 ◽

Author(s):

Bahareh Yahyavi ◽

Mahmoud Mani ◽

Habibollah Naddaf

Keyword(s):

Negative Impact ◽

Numerical Study ◽

Aerodynamic Characteristics ◽

Aerodynamic Performance ◽

Hole Diameter ◽

Pitching Moment ◽

Surface Pressure Distribution ◽

Moment Coefficient ◽

Pass Through ◽

Good Agreement

Aerodynamic performance of a full span NACA 641-412 airfoil with a circular-shaped damage at various attack directions has been numerically investigated in this study. To assess the aerodynamic effects of different penetration angles in which threats such as projectiles can pass through the wings, attack directions of 30°, 60°, -30° and -60° relative to the normal axis of the chord line has been studied and compared with attack direction of 0°. To validate with published studies about damaged wing, the 200 mm chord airfoil was simulated with the damage hole diameter of 20% chord at the midspan and midchord location in Reynolds number of 500,000. Quantitative and qualitative results of this numerical study had a good agreement with published experimental data due to appropriate structured mesh and turbulence modelling. In addition to lift, drag and pitching moment coefficient, surface pressure distribution around the damage hole has been studied. Results show that, if the penetration angle becomes more negative, aerodynamics performance of the wing will be further decreased; therefore, attack directions of threat mechanisms such as “ahead and above” or “below from the rear” have severe negative impact than other directions on aerodynamic performance of the damaged infinite wing.

Download Full-text

Comparison of Aerodynamic Properties of Badminton Feather and Synthetic Shuttlecocks

Proceedings ◽

10.3390/proceedings2020049104 ◽

2020 ◽

Vol 49 (1) ◽

pp. 104

Author(s):

Kenichi Nakagawa ◽

Hiroaki Hasegawa ◽

Masahide Murakami

Keyword(s):

Wind Tunnel ◽

High Stability ◽

Angle Of Attack ◽

Pitching Moment ◽

Wind Tunnel Experiments ◽

Aerodynamic Stability ◽

Fluid Forces ◽

Moment Coefficient ◽

Aerodynamic Properties ◽

The Difference

The purpose of this study is to investigate the difference in aerodynamic properties between the feather shuttlecock and the synthetic shuttlecock. In particular, we focus on the aerodynamic stability of the two types of shuttlecock during impulsive change of an angle of attack (flip movement). Wind tunnel experiments are performed by using two types of the badminton shuttlecock (feather and synthetic shuttlecocks) to measure the fluid forces, and to visualize the flow fields around the shuttlecock. It is confirmed that the pitching moment coefficient at a near-zero angle-of-attack for feather shuttlecock is larger than that for synthetic shuttlecock. The results indicate that the feather shuttlecock demonstrates high stability in response to the flip phenomenon.

Download Full-text

The functional significance of nectridean tabular horns (Amphibia: Lepospondyli)

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1980.0110 ◽

1980 ◽

Vol 209 (1177) ◽

pp. 513-537 ◽

Cited By ~ 8

Keyword(s):

Wind Tunnel ◽

Flow Visualization ◽

Mouth Opening ◽

Ventral Side ◽

Scale Model ◽

Small Fish ◽

Angle Of Incidence ◽

Pitching Moment ◽

Plan View ◽

Moment Coefficient

The order Nectridea of the subclass Lepospondyli is of Palaeozoic age. Within this order, later members of the Keraterpetontidae developed hyper-extended tabular horns, so that in plan view the skull is boomerang shaped. Many unsuccessful attempts have been made to explain this shape in functional terms. The two genera that show the greatest development of these horns, Diplocaulus Cope and Diploceraspis Romer, are analysed experimentally in a low-speed wind-tunnel. Differences between the two genera include that of size: the former is about twice the size of the latter genus and it has a prominent, ventrally directed flange on the quadratojugal-squamosal region not seen to the same extent in Diploceraspis . In Diplocaulus the otic notch, which has come to lie on the ventral side of the skull, is large and extends proportionally further towards the tip of the horn than in Diploceraspis . The otic notches may have supported pharyngeal pouches, developed as accessory respiratory organs. A full-scale model of the Diplocaulus skull was made from information obtained from published illustrations and casts. It was mounted in the wind-tunnel so that angles of incidence varying from -10 to +25° were possible, and a fixed body was modelled so as to account for interference effects. The Diploceraspis condition was simulated by removing the prominent quadratojugal flange. Four conditions were investigated: (1) the Diplocaulus model; (2) the Diploceraspis model; (3) the investigation of the effect of roughness of the surface of the model, to simulate the labyrinthodont condition of the dermal bones; and (4) an investigation of the effect of mouth-opening on the behaviour of the model. In addition, a flow-visualization test was carried out. All the experiments were carried out at a speed corresponding to the animal moving at 1.65 m/s in water. Coefficients of lift, drag and pitching moment were measured, over the range -10 to +25°, at two degree intervals. The significance of the results lies in the behaviour of the lift and pitching moment coefficient curves. The position of the centre of pressure does not move with the change of these two parameters and therefore the point of action of the centre of lift is fixed with respect to the occipital condyles. Forces exerted on the head are proportional to the deflexion of the head. Small but significant differences are seen when the curves for the two genera are compared. In Diplocaulus the lift and pitching moment curves cross the zero-line very close to the origin, but in the other genus they cross considerably to the left of the origin. Roughening of the surface in two stages causes lift coefficients to be diminished and drag increased. It is concluded that the surface of the living animals was smooth or almost so. With the smooth model, it was noted that when the mouth was opened that neither lift nor drag coefficient was significantly altered. It is concluded that when taking prey these animals must have suffered little deceleration. The flow visualization tests show that two flow regimes operated on the upper surface of the Diplocaulus model. To begin with, the flow was streamlined and parallel to the midline over all the head area, but after a critical angle of incidence the central region of the head stalled and the flow over the horns became stabilized as laterally directed vortices. From all of the results it is believed that the Keraterpetontidae were active midwater feeders preying on small fish, larval amphibia, aquatic arthropods and gastropods. They used the unique physical properties of the head to effect steep climbing ascents from the lake or stream bed to attack their prey, before returning to the bottom. The differences between the two genera are related to their contrasting environments and the possible course of evolution giving rise to these extreme adaptations is considered. Dorso-ventral flattening is seen as an aid to an active mode of life in the two genera under discussion here, and the same possibly applies to the Labyrinthodontia as a whole.

Download Full-text

Numerical Simulation of the Aerodynamic Influence of Aircrafts During Aerial Refueling with Engine Jet

International Journal of Aeronautical and Space Sciences ◽

10.1007/s42405-019-00212-2 ◽

2019 ◽

Vol 21 (1) ◽

pp. 15-24 ◽

Cited By ~ 1

Author(s):

Yi Li ◽

Yang Zhang ◽

Junqiang Bai

Keyword(s):

Stokes Equations ◽

Dynamic Pressure ◽

Lift Coefficient ◽

Jet Flow ◽

Aerodynamic Characteristics ◽

Navier Stokes ◽

Pitching Moment ◽

Aerial Refueling ◽

Rolling Moment ◽

Moment Coefficient

Abstract Aerial refueling technology has been widely applied in various fields and it is one of the hotspots but difficulties for the aeronautical technologies. DLR-F6 WBNP model is used as a tanker and a fighter model is used as a receiver. The flow field of Probe–Drogue refueling and Flying Boom refueling is numerically simulated using the Reynolds-averaged Navier–Stokes equations, and the effects of the jet flow and the aerodynamic characteristics of the receiver are taken into consideration. The results indicate that the effect of downwash of the tanker reduces the lift coefficient and decreases the pitching moment coefficient of the receiver. The jet flow of tanker increases the dynamic pressure while decreases the local angle of attack, which increases the pressure difference between the upper and lower surfaces of receiver. Compared with the results without jet, the jet flow can increase the lift and the drag of the receiver and reduces the pitching moment, and even cause the change of rolling moment direction. Therefore, engine jet is an important factor when simulating aerial refueling.

Download Full-text

Research on Aerodynamic Shape Design Scheme of a Distributed Propeller Transport Aircraft and Its Slipstream Effect

Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University ◽

10.1051/jnwpu/20193720361 ◽

2019 ◽

Vol 37 (2) ◽

pp. 361-368

Author(s):

Xiaochuan Yang ◽

Wei Li ◽

Yuntao Wang ◽

Hao Wang ◽

Hao Yue ◽

...

Keyword(s):

Electric Propulsion ◽

Aerodynamic Characteristics ◽

Small Scale ◽

Pitching Moment ◽

Disk Model ◽

Transport Aircraft ◽

Design Scheme ◽

The Difference ◽

Lift And Drag ◽

High Thrust

With the continuous development and widespread attention of electric propulsion technology in traditional transportation fields such as automobiles and trains, the distributed propeller propulsion technology applied to electric or hybrid electric medium and small scale aircrafts has become a new topic in aviation research. This paper presents a preliminary design scheme of a distributed propeller electric propulsion transport aircraft firstly. Then, based on Reynolds average N-S equations, combined with the SA turbulence model, and replaced the real distributed propellers with simplified disk model, the aerodynamic characteristics of the aircraft with and without slipstream under the condition of low speed and high thrust at low altitude are analyzed. Finally, the effects of pressure distribution, pitching moment characteristics and wing flow on distributed propellers are studied in detailed. The results show that the lift and drag of the aircraft with slipstream are both larger than without slipstream and with slipstream effect, the pitching moment of the wing decreases, the pitching moment of the tail increases. When the tail is far away or completely inside the region of slipstream, the difference of pitching moment of the tail with and without slipstream is little, and the difference is obvious as the tail is only partially in the region of slipstream; When the diameter of distributed propellers is far larger than the wing thickness, more propeller power is used to shove air flow away from the surface area of the wing, and resulting in an insignificant increase in the coefficient of lift.

Download Full-text

Aerodynamic Characteristics and Trajectory of Projectile with a Deflectable Nose

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.543-547.16 ◽

2014 ◽

Vol 543-547 ◽

pp. 16-19

Author(s):

Ji Feng Wei ◽

Xiong Li ◽

Shu Shan Wang ◽

Yu Xin Xu

Keyword(s):

Experimental Data ◽

Mach Number ◽

Drag Coefficient ◽

Aerodynamic Characteristics ◽

Pitching Moment ◽

Flight Trajectory ◽

Start Time ◽

Aerodynamic Efficiency ◽

Moment Coefficient ◽

Maximum Range

The basic experiment and detailed simulations are carried out to study the aerodynamic characteristics of projectile with deflectable nose. The parameters of computation are revised on the basis of experimental data. Further simulations show that the influence of mach number and deflectable angle on drag, lift, pitching moment and flight trajectory. The drag coefficient increases firstly and then decreases with the change of mach number, while drag coefficient and pitching moment coefficient grows exponentially. It can be seen that the ratio of lift to drag increases consistently, which means the aerodynamic efficiency of projectile would be improved with the increase of deflectable angle and mach number. The range is influenced by the start time of deflection. For the projectile with deflectable angle 10, the maximum range can be obtained if the forehead deflects at 3s.

Download Full-text