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This article examines the influence of centrifugal buoyancy on the hydrodynamic and thermal behaviour in fully developed flow through an orthogonally rotating duct of aspect ratio 2:1. A series of computations have been performed at rotation numbers ranging from 0 to 0.2, for constant‐density flows (no buoyancy) and also for different levels of outward and inward buoyancy. The resulting comparisons reveal that for a Reynolds number of 32,500, rotational buoyancy effects become significant at Rayleigh number values greater than 107. In outward flows, buoyancy is found to strengthen the effects of the Coriolis force on the mean motion and, by raising turbulence levels, buoyancy also enhances wall heat transfer along both the pressure and the suction side of the rotating duct. In inward flows, it is found that strong buoyancy can reverse the direction of the Coriolis‐induced secondary motion, which causes a strong rise in wall heat transfer along the suction side and a similarly significant fall in heat transfer along the pressure side. The computed effects on heat transfer are in qualitative agreement with the findings of a number of experimental studies. For both inward and outward flows, at a constant Reynolds number, the modifications of centrifugal buoyancy on the side‐averaged levels of heat transfer correlate reasonably well with the rotational Rayleigh number.

In‐plane vibration of a balanced helicopter rotor is caused by variations with azimuth of the in‐plane forces acting on individual blades. These forces may be summarized under three headings: ‘Induced forces’ caused by the inclination of elemental lift vectors relative to the axis of rotation. ‘Profile drag forces’: variations are caused by changes with azimuth angle of the angle and airspeed of the individual blade elements. ‘Coriolis forces’, which are caused by blade flapping, which brings about a variation of blade moment of inertia about the axis of rotation. Equations are developed in this paper for the resultant hub force due to each of these forces, on the assumptions of small flapping hinge offset. It is assumed that blades are linearly twisted and tapered, an assumption which in practice can be applied to any normal rotor. It is shown that by suitably inclining the mechanical axis it is possible to balance out the worst induced and profile drag vibrations by the coriolis one, which can be made to have opposite sign. If the mechanical axis is fixed in the fuselage, this suppression is fully effective for one flight condition only. In multi‐rotor helicopters, vibration suppression can be extended over a much wider range by varying the fuselage attitude. The logical result of this analysis is, for single rotor helicopters, a floating mechanical axis which can be adjusted or trimmed by the pilot. This would be quite simple to do on a tip‐driven rotor, and has already been achieved with a mechanical drive on the Doman helicopter. The more important causes of vibration from an unbalanced rotor are next con‐sidered, attention here being confined principally to fully articulated rotors, which are the most difficult to balance because the drag hinges tend to magnify all in‐accuracies in finish and balance. From a brief discussion of the vertical vibration of an imperfect rotor it is shown that some contemporary methods of ‘tracking’ are fundamentally wrong. Finally the vibration due to tip‐mounted power units is described. In discussing the effect of a vibratory force on a helicopter a simple response chart is developed, and it is thought that its use could well be accepted as a simple standard for general assessment purposes. In the development of equations for vibration the following points of general technical interest are put forward: An equation for induced torque is developed which includes a number of hitherto neglected parameters. A new form of equation for mean lift coefficient of a blade is suggested. The simple Hafner criterion for flight envelopes is shown to give rise to considerable error, and the use of Eq. (28) is suggested in its place. The variation of profile torque with forward speed is given, and the increase due to ? varying round the disk is expressed as an explicit equation, thus allowing considerable improvement in the present methods of allowing for this effect.

A finite element method based investigation is carried out for the determination of three‐dimensional turbulent flow structures and heat transfer rates of cooling ducts within turbine blades which rotate about an axis orthogonal to their own axis of symmetry. The effects of geometrical configurations, Coriolis forces and coolant inertias on the hydrodynamic and thermal characteristics have been systematically predicted and compared with experimental measurements.

The artificial compressibility method is used to analyze internal flows in rotating ducts having strong curvature. This study was concerned with the laminar flow of an incompressible Newtonian fluid having constant viscosity in circular and square ducts with a 908 bend. The emphasis of the present simulation is to determine the effect of rotation and through‐flow rate on the fluid physics and friction characteristics in the straight channel and in the curved geometric regions. The Reynolds numbers ranged from 100 to 790 and the Rossby numbers from 0 to 0.4. Coriolis forces arising from rotation produce a non‐symmetric secondary flow in the bend that increases the loss coefficient as compared with the values for non‐rotation. In addition, the wall friction losses in the straight outlet section are increased, and both effects are directly proportional to the Rossby number.

This paper aims to present the analytical investigation on an unsteady magneto-convective rotation of an electrically conducting non-Newtonian Casson hybrid nanoliquid past a vertical porous plate. The effects of thermal radiation, heat source/sink and hydrodynamic slip phenomenon are also taken into account. Ethylene glycol (EG) is adopted as a base Casson fluid. The Casson fluid model is accounted for to describe the rheological characteristics of non-Newtonian fluid. EG with copper and alumina nanoparticles is envisaged as a non-Newtonian Casson hybrid nanoliquid. The copper-alumina-ethylene glycol hybrid nanoliquid is considered as the regenerative coolant.

The perturbation method is implemented to develop the analytical solution of the modeled equations. Acquired solutions are used to calculate the shear stresses and the rate of heat transfer in terms of amplitudes and phase angles. Numerical results are figured out and tabled to inspect the physical insights of various emerging parameters on the pertinent flow characteristics.

This exploration discloses that the velocity profiles are strongly diminished by the slip parameter. Centrifugal and Coriolis forces caused by the plate rotation are found to significantly change the entire flow regime. The supplementation of nanoparticles is to lessen the amplitude of the heat transfer rate. A comparative study is carried out to understand the improvement of heat transfer characteristics of Casson hybrid nanoliquid and Casson nanoliquid. However, the Casson hybrid nanoliquid exhibits a lower rate of heat transfer than the usual Casson nanoliquid.

This proposed model would be pertinent in oceanography, meteorology, atmospheric science, power engineering, power and propulsion generation, solar energy transformation, thermoelectric and sensing material processing, tumbler in polymer manufacturing, etc. Motivated by such practical implications, the proposed study has been unfolded.

The novelty of this paper is to examine the simultaneous effects of the magnetic field, Coriolis force, suction/injection, slip condition and thermal radiation on non-Newtonian Casson hybrid nanoliquid flow past an oscillating vertical plate subject to periodically heating in a rotating frame of reference. A numerical comparison is also made with the existing published results under some limiting cases and it is found that the results are in good agreement with them. An in-depth review of the literature and the author’s best understanding find that such aspects of the problem have so far remained unexplored.

Deals with the flow reversal in a buoyancy‐opposed rotating duct that causes heat transfer deterioration. An active technique of trailing‐wall transpiration is adopted to check whether it can avoid the flow separation and subsequently improves the heat transfer deterioration. Finite‐difference method is employed to solve the three‐dimensional Navier‐Stokes equations and the energy equation. Periodic conditions are used between the entrance and exit of a typical two‐pass duct for the closure of the elliptic problem. The predicted results reveal that fluid withdrawal through the trailing wall can avoid the flow separation from the leading wall of the radial‐outward duct (ROD) and thus eliminate local hot spots. In addition, the trailing‐wall suction not only increases the peripherally averaged heat transfer but also reduces the friction loss in the ROD. In the radial‐inward duct (RID), both the peripherally averaged heat transfer and peripherally averaged friction factor are augmented by trailing‐wall injection and are degraded by the trailing‐wall suction.

Research and development of solid state gyroscopes has been, for a long time, ongoing within British Aerospace (Systems & Equipment) Ltd, (BASE). BASE, in order to be a leader in the supply of gyroscopes, has continued to research and develop new products. Future developments point to solid state devices supporting conventional gyroscopes.

This paper aims to present new technological approaches of manufacturing of micromechanical gyroscope ring-sensitive element based on the nanoporous anodic alumina instead of traditional silicon technology. Simulation and the operation analyses of such elements have been performed.

The design of gyroscope represents a sensitive element on a glass substrate; in the center of a ring, there is a permanent magnet in a steel box. The sensitive element is made of profiled nanoporous anodic alumina consisting of an octagonal frame which is connected to a ring in the center with eight N-shaped spokes. The technology of the sensitive element fabrication involves the electrochemical formation of nanoporous anodic alumina substrate given the thickness and porosity and its chemical etching on the element topology. The basic parameters and the operation principle of the nanoporous alumina-sensitive element have been defined by finite element simulation.

It is shown that the resonance frequencies of the sensitive element change as functions of the alumina porosity. The main parameters of the nanoporous alumina-sensitive element have been compared with parameters of a silicon-sensitive element. Calculations have shown that the mechanical deformations of the von Mises are approximately lower by two times in the nanoporous alumina-sensitive element.

High-precision angular rate measurement will be achieved by reducing mechanical and electrical noises practically to zero through careful designing of a ring magnetoelectric gyroscope

The ring resonator made of nanoporous anodic alumina will allow to increase the threshold of sensitivity and stability of micromechanical gyroscope characteristics owing to the high precision of geometric dimensions, the stability of the elastic properties and the quality factor.

Finite element based solution techniques have been developed to replace the conventional ‘wall functions’ in the ‘near wall zone’ of general confined turbulent flows. The technique is validated by application to the turbulent flow and associated heat transfer within a square/rectangular cross‐sectioned duct rotating about an axis orthogonal to its longitudinal axis. The predicted results are compared with those from experimental measurements and excellent agreement is obtained when using the advocated methodology.

The study aims to focus on rotation effects on a ribbed channel of gas turbine blades for internal cooling. The combination and interaction between secondary flows generated by angled rib geometry and Coriolis forces in the rotating channel are studied numerically.

A radially outward flow passage as an internal cooling test model with and without ribs is used to perform the investigation. Aspect ratio of the passage is 1:1. Square ribs with e/Dh = 0.1, p/e = 10 and four various rib angles of 90°, 75°, 60° and 45° are configured on both the leading and trailing surfaces along the rotating duct. The study covers a Reynolds number of 10,000 and Rotation number in the range of 0-0.15.

Nusselt numbers in the ribbed duct are 2.5 to 3.5 times those of a smooth square duct, depending on the Rotation number and rib angle. The maximum value is attained for the 45° ribbed surface. The synergy angle between the velocity and temperature gradients is improved by the angled rib secondary flows and Coriolis vortex. The decrease of the synergy angle is 8.9, 13.4, 12.1 and 10.1 per cent for the 90°, 75°, 60° and 45° ribbed channels with rotation, respectively. Secondary flow intensity is increased by rotation in the 90° and 75° ribbed ducts and is decreased in 45° and 60° ribbed cases for which the rib-induced secondary flow dominates.

The primary motivation behind this work is to investigate the possibility of heat transfer enhancement by vortex flow with developing turbulence in the view point of the field synergy principle and secondary flow intensity.