Archive of Mechanical Engineering

Flow control is studied to improve the aerodynamic performance of an aerofoil. A strategy for maintaining the near-wall flow structure with a given spatial scale, developed within the framework of interdisciplinary research, is used. The proposed active flow control method is based on the application of spanwise arrays of mechanical, thermal, or plasma vortex generators. The latter are found most versatile and efficient for the formulated goal. Aerodynamic coefficients measured in the specified wind tunnel are discussed for the 12.5% supercritical airfoil model. The model is controlled by the spanwise array of pulsating high-voltage plasma discharges. This multi-actuator system provides a sufficient number of control parameters such as pulse duration and repetition rate, the distance between the neighboring actuators (space scale of generated disturbances), and the plasma array location along the airfoil chord. Measurements in a range of Reynolds numbers of Rec=(3-7)x105 showed growth of a maximal lift coefficient CLmax up to 10% and the stall angle by 1.5°-3.5° accompanied by drag reduction up to 7%.

Nina Yurchenko

Pavlo Vynogradskyy

Roman Pavlovskyy

Improvement of the airfoil lift and drag characteristics using plasma-efficient flow control

利用等离子体高效流动控制改善翼型升力和阻力特性

Exoskeletons of lower extremities are used mainly for gait treatment in physical rehabilitation. However, they are also capable of being involved in other types of exercises. Nevertheless, their structure needs to be adequately adjusted for such applications. To analyse approaches to that, this review paper investigates the mechanical designs of rehabilitation exoskeletons for lower extremities. The study seeks to identify best practices in designing and implementing these devices by analysing fifty-two articles. It covers aspects such as kinematic structures, materials used, types of drives, and the range of exercises. Standard design features include multiple degrees of freedom, primarily at the hip, knee, and ankle joints, and using lightweight materials to enhance mobility and reduce power consumption. The review also discusses the advantages of different driving systems. The findings provide valuable insights for developing effective and safe rehabilitation exoskeletons, contributing to improved patient outcomes in physiotherapy and rehabilitation settings.

Krzysztof Zawalski

Mehmet Emin Aktan

Piotr Falkowski

Maciej Mazowiec

Jan Oleksiuk

Bazyli Leczkowski

Zbigniew Pilat

Michał Jarek

Erhan Akdogan

Paweł Niedbalski

Vasfi Emre Omurlu

Mateusz Wawrzyniak

Systematic review of mechanical designs of rehabilitation exoskeletons for lower-extremity

下肢康复外骨骼机械设计的系统综述

Abstract In offshore pedestal cranes one may distinguish three components of considerable length: a pedestal, a boom and a frame present in some designs. It is often necessary in dynamical analyses to take into account their flexibility. A convenient and efficient method for modelling them is the rigid finite element method in a modified form. The rigid finite element method allows us to take into account the flexibility of the beam system in selected directions while introducing a relatively small number of additional degrees of freedom to the system. This paper presents a method for modelling the pedestal, the frame and the boom of an offshore column crane, treating each of these components in a slightly different way. A custom approach is applied to the pedestal, using rigid finite elements of variable length. Results of sample numeric computations are included.

Jerzy Krukowski

Andrzej Maczynski

Application of the Rigid Finite Element Method for Modelling an Offshore Pedestal Crane

海上基座起重机建模的刚性有限元法应用

Textile composites can be manufactured utilizing both synthetic and natural fibers, such as Corypha gebanga fiber, being a viable option. The weaving of Corypha gebanga fiber with cotton thread in a plain weave configuration enables its application as a reinforcement material in textile composites involving a resin matrix. This research aims to investigate the mechanical characteristics of plain woven Corypha gebanga fiber textile fabric-reinforced polymer hybrid composites made from epoxy resin. This study utilized four different variations: a control group without any treatment, and three treatment groups using solutions with NaOH concentrations of 2.5%, 5%, and 7.5%. The result showed that NaOH concentrations above 2.5% seem to have a detrimental effect, as indicated by the gradual decrease in mechanical performance observed in the 5% and 7.5% NaOH-treated specimens. The decrease in tensile strength suggests that prolonged exposure to alkaline conditions leads to permanent alterations in the cellulose structure and morphology. The optimal concentration of NaOH for maximum mechanical performance enhancement is found to be 5%, which balances the removal of impurities and the avoidance of excessive fiber damage. Microscopy image analysis showed that fiber pullout occurred in all specimens tested that were cut in the direction of the warp during tensile testing. The onset of fracture was characterized by the resin breaking initially, followed by the fibers stretching and ultimately breaking.

I Gusti Ngurah Nitya Santhiarsa

I Gusti Bagus Wijaya Kusuma

I Putu Lokantara

Ni Made Dwidiani

Si Putu Gede Gunawan Tista

I Gede Artha Negara

The influence of NaOH concentration on the mechanical properties of Corypha gebanga fiber-reinforced composites

NaOH浓度对Corypha gebanga纤维增强复合材料力学性能的影响

The paper presents experimental investigations of pressure fluctuations near the tip clearance region of the rotor blades of the axial-flow low-speed compressor stage in stable and unstable parts of the overall performance characteristic.In this investigation, unsteady pressure was measured with the use of high frequency pressure transducers mounted on the casing wall of rotor passage.The pressure signals and their frequency characteristics were analyzed during the steady-state processes, before the rotating stall, during the transition from the steady-state process to the rotating stall, and during a stabilized phenomenon of low-frequency rotating stall.As the operating point moves to the unstable region of flow characteristic, an inception of the rotating stall can be observed, which rotates with a speed of about 41.4% of the rotor speed.The results of this study confirm that in the low-speed axial compressor stage operating in a rotating stall regime there appears one stall cell that spreads over to adjacent rotor blade channels.As the flow rate is reduced further, the frequency of the rotating stall decreased to 34.8% of the rotor speed and the number of blade channels with the stall cell increases.

Andrzej Witkowski

Marcin Ziach

Mirosław Majkut

Michał Strozik

Experimental investigations of the flow phenomena in the rotor blades of the axial flow low speed compressor stage at the unstable part of the overall performance characteristic

轴流低速压气机级转子叶片在整体性能特性不稳定部分的流动现象实验研究

The impact of a simple trailing-edge plain flap on the aerodynamics of the SD7037 airfoil have been studied in this paper using computational fluid dynamics at Reynolds number of 3×105 across various low angles of attack and flap deflection angles. The computational model was evaluated by using Star CCM+ software with κ--ω SST turbulence and gamma transition model to solve Navier-Stokes equations. The accuracy of the computational model has been confirmed through comparison with experimental data, showing a high level of agreement at low angles of attack. The findings revealed that specific combinations of angles of attack and flap deflection angles could increase the lift-to-drag ratio by over 70% compared to baseline conditions, benefiting airfoil performance, particularly during takeoff. Some combinations, however, resulted in decreased performance and should be avoided. The results also showed that with the increase of either the angle of attack or the flap deflection angle, the pitching moment increased.

Ahmed Tawfeeq Mustafa Ali Abed

Computational analysis of SD7037 airfoil with plain flap

SD7037翼型带简单襟翼的计算分析

In this paper, a novel analytical approach is proposed to predict the performance and onset criteria of a three-stage double-acting thermoacoustic Stirling oscillator (TDTASO). First, a coupled dynamic-thermodynamic model justifying the behavior of TDTASO is presented, taking into account Schmidt's theory assumptions. Subsequently, the manipulation of the obtained governing equations reveals that the considered Stirling oscillator is a physical regulator system. Thus, the onset criteria, which are the necessary conditions for designing such oscillators, are assessed based on a new analytical method resulting from a regulator-like model. Accordingly, the onset temperature difference is predicted corresponding to different dimensions of the resonator section in the TDTASO. Next, the sensitivity of the TDTASO to the inconsistency of resonators' dimensions is investigated. The results show that increasing the length of the mismatched water column results in a higher frequency. Finally, a prototype TDTASO is constructed and experimentally evaluated. Accordingly, the oscillator frequency is measured 3.14 Hz corresponding to the onset temperature of 163 C and the resonator length of 0.52 m. The experimental data demonstrate the effectiveness of the proposed analytical scheme in predicting the necessary conditions for designing the TDTASO.

Mohammad Hossein Sangdani

Alireza Tavakolpour-Saleh

Predicting performance and onset criteria of a three-stage double-acting thermoacoustic Stirling oscillator: Analysis and experiment

预测三阶段双作用热声斯特林振荡器的性能和起振准则：分析与实验

Abbreviation	Arch. Mech. Eng.
Journal Impact	1.30
Quartiles(Global)	ENGINEERING, MECHANICAL(Q3)

ISSN	0004-0738, 2300-1895
h-index	18

Publication Information	Publisher: Polish Academy of Sciences, Committe of Machine Design，Publishing cycle: ，Journal Type: journal，Open Access Journals: No
Basic data	Year of publication: 2010，Proportion of original research papers: 100.00%，Self Citation Rate:8.30%， Gold OA Rate: 98.81%
Average review cycle	网友分享经验：15 Weeks

Archive of Mechanical Engineering

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Improvement of the airfoil lift and drag characteristics using plasma-efficient flow control

Systematic review of mechanical designs of rehabilitation exoskeletons for lower-extremity

Application of the Rigid Finite Element Method for Modelling an Offshore Pedestal Crane

The influence of NaOH concentration on the mechanical properties of Corypha gebanga fiber-reinforced composites

Experimental investigations of the flow phenomena in the rotor blades of the axial flow low speed compressor stage at the unstable part of the overall performance characteristic

Systematic review of mechanical designs of rehabilitation exoskeletons for lower-extremity

The influence of NaOH concentration on the mechanical properties of Corypha gebanga fiber-reinforced composites

Computational analysis of SD7037 airfoil with plain flap

Improvement of the airfoil lift and drag characteristics using plasma-efficient flow control

Predicting performance and onset criteria of a three-stage double-acting thermoacoustic Stirling oscillator: Analysis and experiment