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This paper aims to consider the thrust force generated by two plunging and pitching plates in a tandem configuration in forward flight to find out the configuration that maximizes the propulsive efficiency with high-enough time-averaged lift force.

To that end, the Navier–Stokes equations for the incompressible and two-dimensional flow at Reynolds number $500 are solved. As the number of parameters is quite large, the case of constant separation between the plates (half their chord length), varying seven non-dimensional parameters related to the phase shift between the heaving motion of the foils, the phase lag between pitch and heave of each plate independently and the frequency and amplitude of the heaving and pitching motions are considered. This analysis complements some other recent studies where the separation between the foils has been used as one of the main control parameters.

It is found that the propulsive efficiency is maximized for a phase shift of 180° (counterstroking), when the reduced frequency is 2.2 and the Strouhal number based on half the plunging amplitude is 0.17, the pitching amplitude is 25° and when pitch leads heave by 135° in both the fore -plate and the hind plate. The propulsive efficiency is about 20 per cent, just a bit larger than that of an isolate plate with the same motion as the fore-plate, but the corresponding lift force is negligible for a single plate. The paper discusses this vortical flow structure in relation to other less efficient ones. Finally, the effect of the separation between the plates and the Reynolds number is also briefly discussed.

The kinematics of two flapping plates in tandem configuration that maximizes the propulsive efficiency are characterized discussing physically the associated vortical flow structures in comparison with less efficient kinematic configurations. A much larger number of parameters in the optimization procedure than in previous related works is considered.

Biomimetic study existing natural biological elements to produce engineering products with similar performance and abilities. The purpose of this paper is to highlight biomimetic studies to produce a new type of airplanes: adding remiges, bending ability and flapping mechanisms.

The used methodology was to thoroughly investigate the literature, to define the proper endurance and fatigue parameters, to perform a series of numerical studies and report improvement percentages relevant to defined parameters.

By adding remiges and the bending mechanism, the authors managed to reach – numerically – the preset desired structure goal. Efficiency increased using remiges with less drag force. In addition, with the help of the bending wing technique, the drag force was improved. The flapping mechanism showed high vibration rates. Last but not least, applying multiple winglets gave a better optimization of the endurance parameter.

Research is conducted at a university without any research facilities. No laboratories exist, and acquiring research papers is mostly difficult and costly.

The research study is original in the sense of its numerical investigation. Proposing biomimetic was at the heart of the airplane invention and cannot be stated as an original contribution. Rather the field has been recently abandoned, and performing this major literature review can be considered as original in a sense it summarizes recent to somewhat old advancement.

A quantitative study that can identify the primary aerodynamic forces and relate them to individual vortical structures is lacking. The paper aims to clarify the quantitative relationships between the aerodynamic forces and vortical structures.

The various contributions to the aerodynamic forces on the two-dimensional impulsively started plate are investigated from the perspective of the vorticity moment theorem. The angles of attacks are set to 45°, 58.5° and 72°, while the Reynolds number is 10,000 based on the chord length. Compared with the traditional pressure force analysis, this theorem not only tells us the total aerodynamic force during the motion, but also enables us to quantify the forces contributed from the fluid elements with non-zero vorticity.

It is found that the time-dependent force behaviors are dominated by the formations and evolutions of these vortical structures. The analysis of the time-averaged forces demonstrates that the lift contributed from the leading edge vortex (LEV) is nearly four times larger than the total lift and the drag contributed from the starting vortex (SV) is almost equal to the total drag when the angle of attack (AoA) increases to 72°, which means the LEV is “lift structure” whereas the SV is “drag structure”.

The present method provides a better perspective for flow control and drag reduction by relating the forces directly to the individual vorticity structures.

In this paper, the Vorticity Moment Theory is first used to study the quantitative relationships between the aerodynamic forces and the vortices.

A cowl for an air‐cooled aircraft engine comprising a series of rearwardly‐extending plate‐like flaps entirely separate from the cowl, a pair of rearwardly‐extending arms associated with each flap one at each margin thereof, a pair of longitudinal flanges on the side of each arm adjacent the flap so as to form a groove between them of which grooves at least one is of greater width than the thickness of the margin of the flap which can thus slide in at least one of said grooves, said margins being supported within said grooves, the circumferential distance between the flanges on one arm and the flanges on the other arm being substantially less than the corresponding dimension of the flap at all operating positions of the arms and the circumferential distance between the base of the groove on one arm and the base of the groove on the other arm being greater than the corresponding dimension of the flap, whereby the flap is supported solely by the arms at all operating positions thereof despite its being entirely separate from the cowl, a pivot for each arm lying along an axis at right‐angles to a fore‐and‐aft central plane, and driving mechanism carried by a fixed part of the cowl and operatively connected to each said arm to rotate it about said pivotal axis.

AS far as we are concerned at present in England, there are only six types of German aeroplanes which are of any interest. These are:—

IT seems rather strange that while the general property of wing flaps of putting up both the lift and the drag of a wing at the same time has been known for many years, so little practical application of this result has been made until quite recently.

An aircraft or other vehicle in which a stream of air taken in from the surrounding atmosphere is passed through a duct to cool the cooling surfaces placed therein of the engine and in which stream a conversion of energy into pressure takes place before the cooling surfaces arc reached and a conversion of pressure into kinetic energy of the stream at its discharge is raised by transferring to the stream waste heat from the engine at a position behind the cooling surfaces and before further loss of pressure is sustained beyond that involved in passing the stream over the cooling surfaces. The above means are adapted to assist propulsion. In one form, an engine a is mounted in a wing b. Engine radiators bl, b2 are mounted in ducts b3, b1 the leading edges of which are in front or behind the leading edge of the wing. Exhaust manifolds c, c1 are provided with fins c0 and are mounted in the ducts to heat the stream. Hinged flaps c3 are provided at the rear of the ducts. In a modification the duct is situated beneath an engine disposed at the front end of the fuselage and a fan forces air through the duct. The invention may be applied to air‐cooled engines. Specification 447,283 is referred to.

SO much controversy has raged around the subject of newsrooms in the past two years, that librarians are, as a rule, utterly tired of it, and the appearance of still another article upon the subject is not calculated to tone down the general spirit of vexation. It requires no little courage to appear in the arena in this year of Grace, openly championing those departments of our institutions which were originally intended to convey the news of the day in the broadest manner.

Some recent effort showed that usage of Krueger flaps helps to maintain laminar flow in cruise flight. Such flaps are positioned higher relative to the chord to shield the leading edge from the insect contamination during take-off. The flap passes several through critical intermediate position during the deployment to its design position. The purpose of this paper is to analyse the aerodynamics.

To better understand such flow phenomena, the combined approach of computational fluid dynamics and experimental methods were used. Flow simulation was performed with in-house finite volume Navier–Stokes solver in fully turbulent unsteady RANS regime. The experimental data were obtained by means of force and pressure measurements and some areas of the flow field were examined with 2 C particle image velocimetry.

The airfoil with flap in critical position has a very limited maximum lift coefficient. The maximum achievable lift coefficient during the deployment is significantly affected by the vertical position of the trailing edge of the flap. The most unfavourable position during the deployment is not the flap perpendicular to the chord, but the flap inclined closer to it is the retracted position.

The flap movement was not simulated either in the simulation or in the experiment. Only intermediate static positions were examined.

A better understanding of aerodynamic phenomena connected with the deployment of a Krueger flap can contribute to the simpler and lighter of kinematics and also to decrease time-to-market.

Limited experimental and computational results of Krueger flap in critical positions during the deployment are published in the literature.

Combustible mixture is heated in a connection e. arranged between a carburetter or a supercharger and the induction manifold, by a stream‐lined pipe g through which hot lubricant passes, a shaft h, which extends therethrough, throwing the lubricant on to the inner walls of the pipe. The lubricant drains into the pipe through a ball bearing on the shaft.