Effect of Vertical Canard Location on Skin Friction Drag

This study investigates the viscous skin friction drag generation due to the three different vertical canard locations on the mid winger un-swept aircraft scaled-down model by using boundary layer measurements in the wind tunnel. The N22 airfoil was selected for the canard and the modified S1223 airfoil was selected for the wing. The laser cutting technique was employed for the fabrication of the wing, and canard airfoils, which gave sufficient dimensional accuracy to the model. The canard, wing, and fuselage were fabricated by balsa wood and strengthened by Aluminum stripes. The assembled model is tested in an open subsonic wind tunnel a fixed chord Reynolds number 3.8*106. The boundary layers were measured at 70% of the chord and at three different wingspan locations i.e. 30%, 60%, and 90% with 00 incidence angle. The canards were positioned at three vertical positions one at fuselage reference line (FRL) and the remaining two locations at ± 0.16 c from the FRL. The results were compared with wing-body alone and with three canard locations and found that the high canard configuration outperformed the other two configurations and also wing-body alone configuration as it provides half of the total drag. However, the high canard produces 15% more drag than the wing-body alone at the wing tip (90%).The aerodynamic performance of the high canard configuration was found to be significantly promising for the future use in drones and other small aircrafts.

Effect of Speed and Boot Opening on Aerodynamics, Fuel Consumption, and CO2 Emission of Minibus

Overspeeding and overloading contribute to road accidents. In developing countries, overloading is often indicated by open boot due to commercial transporters’ motivation to carry an excess load to boost revenue. Therefore, there is a need to provide measures to control or eliminate the practice of overspeeding and overloading. This study aims to conduct a parametric study to determine the effect of vehicle speed and boot opening on the aerodynamics of airflow around a typical minibus, fuel consumption, and CO2 emission, and recommend optimum boot opening. Computational Fluid Dynamics is employed using the FLUENT™ program. Results show the existence of a wavy pattern for drag coefficient, fuel consumption, and CO2 emission concerning boot opening. Furthermore, two boot opening regions exist: and . The first region exhibits low prediction error (maximum of 7.25%) and better fit of regression model to FLUENT™ data. The first region also has lower susceptibility to exhibit handling instability. Therefore, boot opening around is recommended as the optimum boot opening, to ensure minimum fuel consumption and CO2 emissions, improve handling and safety. The developed regression models could inform regulatory bodies’ formulation and implementation of policies to mitigate road accidents. Keywords—Boot Opening, CO2 emission, Fuel Consumption, Pressure drag, Total Drag, Minibus, Viscous Drag

Coupled Fluid-Thermal Investigation on Drag and Heat Reduction of a Hypersonic Spiked Blunt Body with an Aerodisk

In the traditional investigations on the drag and heat reduction of hypersonic spiked models, only the aerodynamic calculation is performed, and the structural temperature cannot be obtained. This paper adopted the loosely coupled method to study its efficiency of drag and heat reduction, in which the feedback effect of wall temperature rise on aeroheating is considered. The aeroheating and structural temperature were obtained by the CFD and ABAQUS software respectively. The coupling analysis of the hypersonic circular tube was carried out to verify the accuracy of the fluid field, the structural temperature, and the coupled method. Compared with experimental results, the calculated results showed that the relative errors of stagnation heat flux and stagnation temperature were 1.34% and 4.95% respectively, and thus the effectiveness of the coupled method was verified. Installing a spike reduced the total drag of the forebody. The spiked model with an aerodisk reduced the aeroheating of the forebody, while the model without an aerodisk intensified the aeroheating. The spiked model with a planar aerodisk had the best performance on drag and heat reduction among all the models. In addition, increasing the length of the spike reduced the drag and temperature of the forebody. With the increase of the length, the change rates of drag, pressure, heat flux, and temperature decreased gradually. Increasing the diameter of the aerodisk also reduced the temperature of the forebody, while the efficiency of forebody drag reduction first increased and then decreased. In conclusion, the heat and drag reduction must be considered comprehensively for the optimal design of the spike.

Getting the ducks in a row

Vessels – in the widest sense – travelling on a water surface continuously do work the water surrounding it, causing energy to be radiated in the form of surface waves. The concomitant resistance force, the wave resistance, can account for as much as half the total drag on the vessel, so reducing it to a minimum has been a major part of ship design research for many decades. Whether the ‘vessel’ is an ocean-going ship or a swimming duckling, the physics governing the V-shaped pattern of radiated waves behind it is in essence the same, and just as fuel economy is important for commercial vessels, it is reasonable to assume that also swimming waterfowl seek to minimise their energy expenditure. Using theory and methods from classic marine hydrodynamics, Yuan et al. (J. Fluid Mech., vol. 928, 2021, R2) consider whether, by organising themselves optimally, ducklings in a row behind a mother duck can reduce, eliminate or even reverse their individual wave resistance. They describe two mechanisms which they term ‘wave riding’ and ‘wave passing.’ The former is intuitive: the ducklings closest to the mother can receive a forward push by riding its mother's stern waves. The latter is perhaps a more striking phenomenon: when the interduckling distance is precisely right, every duckling in the row can, in principle, swim without wave resistance due to destructive wave interference. The phenomenon appears to be the same as motivates the recent US military research project Sea Train, a row of unmanned vehicles travelling in row formation.

Particle/wall electroviscous effects at the micron scale: comparison between experiments, analytical and numerical models.

We report a experimental study of the motion of 1μm single particles interacting with functionalized walls at low and moderate ionic strengths conditions. The 3D particle’s trajectories were obtained by analyzing the diffracted particle images (point spread function). The studied particle/wall systems include negatively charged particles interacting with bare glass, glass covered with polyelectrolytes and glass covered with a lipid monolayer. In the low salt regime (pure water) we observed a retardation effect of the short-time diffusion coefficients when the particle interacts with a negatively charged wall; this effect is more severe in the perpendicular than in the lateral component. The decrease of the diffusion as a function of the particle-wall distance h was similar regardless the origin of the negative charge at the wall. When surface charge was screened or salt was added to the medium (10mM), the diffusivity curves recover the classical hydrodynamic behavior. Electroviscous theory based on the thin electrical double layer (EDL) approximation reproduces the experimental data except for small h. On the other hand, 2D numerical solutions of the electrokinetic equations showed good qualitative agreement with experiments. The numerical model also showed that the hydrodynamic and Maxwellian part of the electroviscous total drag tend to zero as h → 0 and how this is linked with the merging of both EDL’s at close proximity.

Biomimetics Design Optimization and Drag Reduction Analysis for Indonesia N219 Seaplanes Catamaran Float

Design optimization on the Indonesia N219 seaplane catamaran is necessary to provide better service to rural islands of Indonesia. This research aims at decreasing drag using a design based on biomimicry by imitating the hydrodynamic characteristics of sailfish (Istiophorus platypterus) for pontoon floats. The design is then validated using a numerical fluid test using ANSYS Fluent to see the reduction in drag due to the change from a conventional or Wipeline® 13000 design to a biomimetics adaptation design. Next, further optimization was carried out based on the adaptation design based on trim tests, clearance tests, and deadrise angle dimensions suitable for biomimicry designs at Froude number speeds of 0.4 to 0.7. The design results with the adaptation of biomimicry show that a change in the design with this optimization affects a drag reduction that reaches 30% of the total drag generated by the conventional design.

Characteristics of Separation and Induced Drag in the Use of Swept-back Wing Unmanned Aerial Vehicle

The swept-back wing has been used in almost all aircraft wings. This is necessary to reduce the pressure drag from the wings so that there is an increase in aerodynamic performance. The aerodynamic performance is the ratio between the total drag coefficient and the lift coefficient. This research attempts to explain the swept-back wing phenomenon in unmanned aerial vehicles (UAV) on Eppler 562 airfoil. The numerical simulation uses the k-ε turbulent model at Reynolds number (Re) = 2.34 x 104. Variation of backward swept angle Λ = 0°, 15°, and 30°. The separation growth Λ = 0° occurred more on the wing root, while Λ = 15° and Λ = 30° occurred more on the wingtip. At Λ = 15°, as the angle of attack increases, the area of the separation increases, and the area of the transition towards the separation decreases. The reattach area also has an increase in the area of the trailing edge. At Λ = 30°, with an increase in the angle of attack, there is a shift from the wingtip area to the mid-span. The area of separation and transition to separation has increased significantly. The re-attach area at α = 8o has not been seen, so at α = 12o it has been seen significantly. The vorticity on the x-axis shows Λ = 15°, and Λ = 30° has a wider area while on the z-axis, Λ = 15°, and Λ = 30° have stronger vortex strength. However, in the mid-span, Λ = 0° has a stronger result.

Numerical Analysis of Drag Reduction Characteristics of Biomimetic Puffer Skin: Effect of Spinal Height and Tilt Angle

Based on the migratory phenomenon of the puffer and the cone-shaped structures on its skin, the effects of spinal height and tilt angle on the drag reduction characteristics is presented by numerical simulation in this paper. The results show that the trend of total drag reduction efficiency changes from slow growth to a remarkable decline, while the viscous drag reduction efficiency changes from an obvious increase to steady growth. The total and viscous drag reduction efficiencies are 19.5% and 31.8%, respectively. In addition, with the increase in tilt angle, the total drag reduction efficiency decreases gradually; the viscous drag reduction efficiency first increases and then decreases, finally tending to be stable; and the total and viscous drag reduction efficiency reaches 20.7% and 26.7%, respectively. The flow field results indicate that the pressure drag mainly originates at the front row of the spines and that the total pressure drag can be effectively controlled by reducing the former pressure drag. With the increase in low-speed fluid and the reduction in the near-wall fluid velocity gradient, the viscous drag can be weakened. Nevertheless, the drag reduction effect is achieved only when the decrement of viscous drag is greater than the increment of pressure drag. This work can serve as a theoretical basis for optimizing the structure and distribution parameters of spines on bionic non-smooth surfaces.

Theoretical grounds for determining optimal trim of river-sea vessels

The article presents the theoretical substantiation of using the optimal trim of “river- sea” vessels in order to improve the propulsion of vessels of various types and purposes navigating on seas and rivers. There has been carried out the analysis of the optimal trim for different types of ships in operation. The given calculations prove the possibility of designing new ships with improved sailing characteristics. The scheme of damping the bow shear wave coming from the stem of the “river-sea” vessel is illustrated using the shear wave coming from the bow bulb, with a differential to the bow. It is proved that trimming of a “river-sea” vessel without a bow bulb is effective for slow-moving and high-speed vessels due to the reduction of components and total drag, compared to the resistance to the movement of a vessel with a conventional trim. An integral similar to Mitchell integral for the wave drag of a vessel with a bow bulb is proposed, by means of which the conditions for damping a bow shear wave (coming from the stem) using the bow bulb of a “river-sea” vessel are determined. The elements composing resistance to the vessel propulsion are investigated in detail: total resistance of the medium to the movement of the vessel, resistance of friction, shape, protruding parts, wave, and aerodynamic resistance. There are considered the criteria of the optimal bow draft of the vessel and optimal trim of the vessel, the criteria of the efficient use of the optimal trim for the “river-sea” vessels on the sea sections. An equation is given that determines the value of the optimal length of the wave-forming part of the bow bulb or the condition for the optimal trim. The pictures illustrating a sea vessel bulb, the bow of which is capable of effectively forming a shear wave at a given differential are shown. Conclusions are made about the possibility of using the optimal trim for river-sea vessels on river and sea sections, recommendations are given that contribute to saving fuel and time, increasing the speed to two knots while reducing the total resistance by up to 20%.