Calculation of transonic dynamic stability parameters by an unsteady TSD theory (transonic small-disturbance flow)

1995 ◽  
Author(s):  
C Lan ◽  
Chialu Hsu ◽  
Tai-Hsing Sun
Keyword(s):  
Dynamic Stability ◽  
Small Disturbance ◽  
Stability Parameters

Experimental investigation on aircraft dynamic stability parameters

Meccanica ◽  
1993 ◽  
Vol 28 (1) ◽  
pp. 61-68 ◽  
Author(s):  
Francesco Fusco ◽  
Giorgio Guglieri
Keyword(s):  
Experimental Investigation ◽  
Dynamic Stability ◽  
Stability Parameters

Evaluation of Static and Dynamic Stability of Spinal Cord Injuries: What Are the Gaps

2020 ◽  
Vol 22 (1) ◽  
pp. 1-5
Author(s):  
Hussein Asiabi ◽  
Mokhtar Arazpour ◽  
Mahmoud Bahramizadeh ◽  
Mohammad Taghi Karimi
Keyword(s):  
Spinal Cord ◽  
Dynamic Stability ◽  
Normal Subjects ◽  
Assistive Devices ◽  
Quiet Standing ◽  
Stability Parameters ◽  
Cord Injury ◽  
Lesion Level ◽  
The Stability ◽  
Improve Stability

Background. Depending on the level of lesion, spinal cord injury (SCI) individuals have limited ability to stand and walk. They have to use various assistive devices to restore their abilities. The aim of this study was to evaluate the stability of SCI individuals during walking and quiet standing. Material and methods. Three groups: normal subjects and SCI individuals with complete and incomplete lesions, were enrolled. Stability of the subjects was evaluated based on center of pressure (COP) sways in quiet standing and spatiotemporal gait parameters in walking. The difference between the stability of normal and SCI subjects was determined by use of the two-sample t test. The correlation between the mean values of stability parameters in standing and walking and lesion level was determined by use of Pearson’s correlation. Results. The stability of SCI subjects during quiet standing was better than that of normal subjects. How­ever, their dynamic stability was significantly less than normal subjects. The dynamic stability of complete and incomplete SCI subjects did not differ significantly (P-value<0.05). There was no correlation between lesion level and stability parameters. Conclusion. 1. SCI individuals suffer mostly from lack of dynamic stability, which does not depend on their lesion levels. 2. It seems that this problem may be due to rehabilitation methods used to improve stability in these patients. 3. It is recommended that new methods of rehabilitation or assistive devices should be used to improve stability of these individuals.

scholarly journals Unsteady Vibration Aerodynamic Modeling and Evaluation of Dynamic Derivatives Using Computational Fluid Dynamics

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Xu Liu ◽  
Wei Liu ◽  
Yunfei Zhao
Keyword(s):  
Dynamic Stability ◽  
Time Domain ◽  
System Modeling ◽  
Aircraft Design ◽  
Experimental Simulation ◽  
Experimental Result ◽  
Calibration Model ◽  
Stability Parameters ◽  
Slender Body Theory ◽  
Vibration Model

Unsteady aerodynamic system modeling is widely used to solve the dynamic stability problems encountering aircraft design. In this paper, single degree-of-freedom (SDF) vibration model and forced simple harmonic motion (SHM) model for dynamic derivative prediction are developed on the basis of modified Etkin model. In the light of the characteristics of SDF time domain solution, the free vibration identification methods for dynamic stability parameters are extended and applied to the time domain numerical simulation of blunted cone calibration model examples. The dynamic stability parameters by numerical identification are no more than 0.15% deviated from those by experimental simulation, confirming the correctness of SDF vibration model. The acceleration derivatives, rotary derivatives, and combination derivatives of Army-Navy Spinner Rocket are numerically identified by using unsteady N-S equation and solving different SHV patterns. Comparison with the experimental result of Army Ballistic Research Laboratories confirmed the correctness of the SHV model and dynamic derivative identification. The calculation result of forced SHM is better than that by the slender body theory of engineering approximation. SDF vibration model and SHM model for dynamic stability parameters provide a solution to the dynamic stability problem encountering aircraft design.

Dynamic Stability Parameters Design for ITER Poloidal Field Converter

2014 ◽  
Vol 34 (3) ◽  
pp. 519-527 ◽  
Author(s):  
Zhiquan Song ◽  
Xing Zhang ◽  
Peng Fu ◽  
Lin Dong ◽  
Min Wang ◽  
...  
Keyword(s):  
Dynamic Stability ◽  
Poloidal Field ◽  
Stability Parameters ◽  
Iter Poloidal Field ◽  
Poloidal Field Converter

Hypersonic dynamic stability of wave riders

2017 ◽  
Vol 89 (3) ◽  
pp. 434-443
Author(s):  
Mahmood Khalid ◽  
Khalid A. Juhany
Keyword(s):  
Dynamic Stability ◽  
Design Method ◽  
Static Stability ◽  
Small Disturbance ◽  
Similarity Parameter ◽  
Content Type ◽  
Flat Surfaces ◽  
Stability Derivatives ◽  
Cone Type ◽  
Half Cone

Purpose The purpose of this paper is to obtain close form expressions for the dynamic stability of conical wave riders with flat surfaces which could be equipped with lifting surfaces on its plain flat surface. Numerical simulation would require very large meshes to resolve flows at subscale level and the experimental evaluations would be equally difficult, requiring expensive measurement facilities with challenging procedures to secure such vehicles in confined test sections to obtain satisfactory wind on and wind off oscillations. Design/methodology/approach The design method uses appropriate pressure fields using small disturbance theory, which, in turn, is perturbed using the unsteady shock expansion theory to recover suitable expressions for the dynamic stability behaviour. Findings It was observed that the dynamic stability of the standard half-cone-type wave riders with flat upper surfaces deteriorates with the axis position measured from the pointed apex reaching a minimum at around x/co = 0.666. The half-cone wave rider with flat upper surfaces is dynamically less stable than a pure cone. Research limitations/implications The method is typically less accurate when the similarity parameter M∞θ ≤ 1 = 1 or if the angle of attack is not small. Practical implications With renewed interest in hypersonic, future hypersonically would be designed as fast lifting bodies whose shapes would be close to the configurations of hypersonic wave riders, especially if they are designed to operate at upper atmosphere altitudes. Originality/value The analytic approach outlined in this paper for the evaluation of dynamic and static stability derivatives is original, drawing from the strengths of the small disturbance theory and shock expansion techniques. The method is particularly important, as there are no reported theoretical, numerical or experimental results in the literature.

scholarly journals Leg Length Discrepancy: Dynamic Balance Response during Gait

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Nurul Azira Azizan ◽  
Khairul Salleh Basaruddin ◽  
Ahmad Faizal Salleh ◽  
Abdul Razak Sulaiman ◽  
Muhamad Juhairi Aziz Safar ◽  
...  
Keyword(s):  
Dynamic Stability ◽  
Dynamic Balance ◽  
Force Plate ◽  
Daily Basis ◽  
Leg Length Discrepancy ◽  
Leg Length ◽  
Stability Parameters ◽  
Length Discrepancy ◽  
Risk Of Fall ◽  
The Right

Balance in the human body’s movement is generally associated with different synergistic pathologies. The trunk is supported by one’s leg most of the time when walking. A person with poor balance may face limitation when performing their physical activities on a daily basis, and they may be more prone to having risk of fall. The ground reaction forces (GRFs), centre of pressure (COP), and centre of mass (COM) in quite standing posture were often measured for the evaluation of balance. Currently, there is still no experimental evidence or study on leg length discrepancy (LLD) during walking. Analysis of the stability parameters is more representative of the functional activity undergone by the person who has a LLD. Therefore, this study hopes to shed new light on the effects of LLD on the dynamic stability associated with VGRF, COP, and COM during walking. Eighteen healthy subjects were selected among the university population with normal BMIs. Each subject was asked to walk with 1.0 to 2.0 ms−1 of walking speed for three to five trials each. Insoles of 0.5 cm thickness were added, and the thickness of the insoles was subsequently raised until 4 cm and placed under the right foot as we simulated LLD. The captured data obtained from a force plate and motion analysis present Peak VGRF (single-leg stance) and WD (double-leg stance) that showed more forces exerted on the short leg rather than long leg. Obviously, changes occurred on the displacement of COM trajectories in the ML and vertical directions as LLD increased at the whole gait cycle. Displacement of COP trajectories demonstrated that more distribution was on the short leg rather than on the long leg. The root mean square (RMS) of COP-COM distance showed, obviously, changes only in ML direction with the value at 3 cm and 3.5 cm. The cutoff value via receiver operating characteristic (ROC) indicates the significant differences starting at the level 2.5 cm up to 4 cm in long and short legs for both AP and ML directions. The present study performed included all the proposed parameters on the effect of dynamic stability on LLD during walking and thus helps to determine and evaluate the balance pattern.

Evaluation of Static and Dynamic Stability of Spinal Cord Injuries: What Are the Gaps?

2020 ◽  
Vol 22 (1) ◽  
pp. 1-6
Author(s):  
Hussein Asiabi ◽  
Mokhtar Arazpour ◽  
Mahmoud Bahramizadeh ◽  
Mohammad Taghi Karimi
Keyword(s):  
Spinal Cord ◽  
Dynamic Stability ◽  
Normal Subjects ◽  
Assistive Devices ◽  
Quiet Standing ◽  
Stability Parameters ◽  
Cord Injury ◽  
Lesion Level ◽  
The Stability ◽  
Improve Stability

Summary Background. Depending on the level of lesion, spinal cord injury (SCI) individuals have limited ability to stand and walk. They have to use various assistive devices to restore their abilities. The aim of this study was to evaluate the stability of SCI individuals during walking and quiet standing. Material and methods. Three groups: normal subjects and SCI individuals with complete and incomplete lesions, were enrolled. Stability of the subjects was evaluated based on center of pressure (COP) sways in quiet standing and spatiotemporal gait parameters in walking. The difference between the stability of normal and SCI subjects was determined by use of the two-sample t test. The correlation between the mean values of stability parameters in standing and walking and lesion level was determined by use of Pearson’s correlation. Results. The stability of SCI subjects during quiet standing was better than that of normal subjects. How­ever, their dynamic stability was significantly less than normal subjects. The dynamic stability of complete and incomplete SCI subjects did not differ significantly (P-value<0.05). There was no correlation between lesion level and stability parameters. Conclusions. 1. SCI individuals suffer mostly from lack of dynamic stability, which does not depend on their lesion levels. 2. It seems that this problem may be due to rehabilitation methods used to improve stability in these patients. 3. It is recommended that new methods of rehabilitation or assistive devices should be used to improve stability of these individuals.

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