Saeed Mahjouri, Rasoul Shabani and Martin Skote
The first touchdown moment of aircraft tyres on a runway is the critical phase where maximum of the vertical and horizontal ground loads is produced. Some valuable drop tests have…
Abstract
Purpose
The first touchdown moment of aircraft tyres on a runway is the critical phase where maximum of the vertical and horizontal ground loads is produced. Some valuable drop tests have been performed at Langley research centre to simulate the touchdown and the spin-up dynamics. However, a long impact basin and a huge power source to accelerate and decelerate the landing gear mechanism have been used. Based on a centrifugal mechanism, the purpose of this paper is to propose the conceptual design of a new experimental setup to simulate the spin-up dynamics.
Design/methodology/approach
A schematic view of the proposed mechanism is presented, and its components are introduced. Operating condition of the system and the test procedure are discussed in detail. Finally, tyre spin-up dynamics of Boeing 747 is considered as a case study, and operating condition of the system and the related test parameters are extracted.
Findings
It is shown that the aircraft tyre spin-up dynamics can be simulated in a limited laboratory space with low energy consumption. The proposed setup enables the approach velocity, sink rate and vertical ground load to be adjusted by low power actuators. Hence, the proposed mechanism can be used to simulate the tyre spin-up dynamics of different types of aircraft.
Research limitations/implications
It is important to note that more details of the setup, including the braking and actuating mechanisms together with their control procedures, should be clarified in practice. In addition, the curved path introduced as the runway will cause errors in the results. Hence, a compromise should be made between the tyre pressure, path curvature, the induced error and the cost of the experimental setup.
Practical implications
The proposed experimental setup could be constructed in a limited space and at a relatively low cost. Low power actuators are used in the proposed system. Hence, in addition to the performance tests, fatigue tests of the landing gear mechanism will also be possible.
Originality/value
Based on a centrifugal mechanism, the conceptual design of a new experimental setup is presented for simulating the tyre spin-up dynamics of aircraft. Considering that the drag load developed during tyre spin-up following initial touchdown is an important factor governing the design of the landing gear mechanism and aircraft structure, the authors hope this paper encourages engineers to continuously make efforts to increase the transparency of the touchdown process, enabling optimisation of landing gear design.
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Saeed Mahjouri, Rasoul Shabani and Martin Skote
Due to the static condition of the wheels at touchdown, they skid on the runway, which may cause the tyres to burn and wear. This phenomenon occurs in a fraction of a second…
Abstract
Purpose
Due to the static condition of the wheels at touchdown, they skid on the runway, which may cause the tyres to burn and wear. This phenomenon occurs in a fraction of a second, known as the spin-up period. The purpose of this paper is to introduce a new strategy to reduce the horizontal force, tyre temperature and wear during the spin-up period.
Design/methodology/approach
First, the dynamics of two different phases of landing, namely, spin-up and breaking phases, are reviewed. Second, a strategy to prevent excessive temperature and wear of the tyre is presented.
Findings
It is found that using a lubricant and coolant, such as water, at the spin-up stretch of the runway is a simple and practical solution to prevent excessive temperature and wear of the tyre. It is revealed that, despite increasing the spin-up period, the rise of the tyre temperature is eliminated and the material properties are preserved for effective braking. A rough quantitative analysis demonstrates that the wetting of tyres in the spin-up phase decreases the loads and tyre wear effectively.
Practical implications
Wetting the touchdown region of the runway without significant areas of standing water is the most practical strategy with the technology available today.
Originality/value
A new strategy is presented for landing with reduced tyre wear. It is the hope that this paper can inspire continuous efforts to realize the implementation of the strategy.
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Martin Skote and Imran Halimi Ibrahim
The cylindrical wake flow is an important part of many engineering applications, including wake turbulence, acoustic noise, and lift/drag forces on bodies. The suppression of von…
Abstract
Purpose
The cylindrical wake flow is an important part of many engineering applications, including wake turbulence, acoustic noise, and lift/drag forces on bodies. The suppression of von Kármán vortex street (VKS) is an important goal for flow control devices. The paper aims to discuss these issues.
Design/methodology/approach
The linear plasma synthetic jet actuator (L-PSJA) is utilized as a flow control device to suppress the VKS formation. Different configurations of the device is studied numerically.
Findings
Of the 12 configurations that were investigated, five configurations were able to suppress the formation of the VKS.
Originality/value
For the first time, the L-PSJA has been shown (through numerical simulations) to be able to suppress VKS.
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Imran Halimi Bin Ibrahim and Martin Skote
For the past decade, plasma actuators have been identified as a subset in the realm of active flow control devices. As research into plasma actuators continues to mature…
Abstract
Purpose
For the past decade, plasma actuators have been identified as a subset in the realm of active flow control devices. As research into plasma actuators continues to mature, computational modelling is needed to complement the investigation of the actuators. This paper seeks to address these issues.
Design/methodology/approach
In this study, the Suzen‐Huang model is chosen because of its ability to simulate both the charge density and Lorentz body force. Its advantages and limitations have been identified with a parametric study of two constants used in the modelling: the Debye length (λD) and the maximum charge density value (ρc* ). By varying the two scalars, the effects of charge density, body force and induced velocity are examined.
Findings
The results show that the non‐dimensionalised body force (Fb*) is nonlinearly dependent on Debye length. However, a linear variation of Fb* is observed with increasing values of maximum charge density. The optimized form of the Suzen‐Huang model shows better agreement in the horizontal velocity profile but still points to inaccuracy when compared to vertical velocity profile.
Originality/value
The results indicate that the body force still has to be modelled more extensively above the encapsulated electrode, so that the horizontal and vertical components of induced velocities are accurately obtained.
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Martin Skote, Gustaf E. Mårtensson and Arne V. Johansson
A precise and rapid temperature cycling of a small volume of fluid is vital for an effective DNA replication process using the polymerase chain reaction (PCR). The purpose of this…
Abstract
Purpose
A precise and rapid temperature cycling of a small volume of fluid is vital for an effective DNA replication process using the polymerase chain reaction (PCR). The purpose of this paper is to study the velocity and temperature fields inside a rotating PCR‐tube during cooling of the enclosed liquid.
Design/methodology/approach
The velocity and temperature fields inside a rotating PCR‐tube during cooling of the enclosed liquid are studied. By using computational fluid dynamics, the time development of the flow can be investigated in detail. Owing to the rotation, the flow exhibits features which could never arise in a non‐rotating system.
Findings
An intricate azimuthal boundary layer flow is presented and explained. The inherent problem of stratification of the temperature is discussed, and different methods towards a remedy are presented. By analyzing the governing equations, some properties of the flow observed in the simulations are explained. It is shown that increasing the rate of rotation does not improve temperature homogenization.
Research limitations/implications
The simulations were performed for a limited number of temperature boundary conditions, as well as a specific simulation geometry.
Practical implications
The analytical and simulation results offer fundamental insight into the physics behind increased DNA duplication. Further simulations offer possible design improvements.
Originality/value
While many studies have probed the effects of buoyancy in rotating cylinders and the development of boundary layers in stratified flows in conical containers rotating around their axis of symmetry, little work has been specifically focused on the case where the axis of rotation is normal to the direction of the stratification, which is the case in the present study.
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Ahmet Enes Arık and Boğaç Bilgiç
The purpose of this paper is to control a landing gear system with an oleo-pneumatic shock absorber with the fuzzy controller.
Abstract
Purpose
The purpose of this paper is to control a landing gear system with an oleo-pneumatic shock absorber with the fuzzy controller.
Design/methodology/approach
The landing gear system with an oleo-pneumatic shock absorber is modeled mathematically. A fuzzy controller is designed for reducing aircraft vibrations. Stroke velocity and main mass velocity parameters were used to decide variable gas pressure with the fuzzy controller.
Findings
The fuzzy controller, designed according to stroke velocity and main mass velocity, reduces aircraft vibrations by the landing impacts. The controller can provide strong robustness because it shows similar good performance for different descent speeds.
Research limitations/implications
This study was carried out through simulations in a computer environment and has not been experimentally tested in a real environment. In addition, signal and measurement delays are not taken into account. In future models, the effects of these signal delays can be added, and the controller can be tested on a real model.
Originality/value
In this study, to the best of the authors’ knowledge, for the first time, the gas pressure for the landing gear system using an oleo-pneumatic shock absorber was controlled by a fuzzy controller that adjusts the stroke velocity and the main mass velocity. Although the oleo-pneumatic shock absorber model contains high nonlinearities, the designed fuzzy controller gave successful results as robust.