scholarly journals Prediction of Vertical Tail Buffet Using CFD/CSD Coupling Method

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Bing Han ◽  
Min Xu
Keyword(s):  
Vortex Breakdown ◽  
Peak Frequency ◽  
Basis Functions ◽  
Resonance Phenomenon ◽  
Structural Dynamic ◽  
Flexible Tail ◽  
Bending Mode ◽  
Tail Structure ◽  
Tail Buffet ◽  
Modal Coordinates

The vertical tail buffet induced by the vortex breakdown flow is numerically investigated. The unsteady flow is calculated by solving the RANS equations. The structural dynamic equations are decoupled in the modal coordinates. The radial basis functions (RBFs) are employed to generate the deformation mesh. The buffet response of the flexible tail is predicted by coupling the three sets of equations. The results show that the presence of asymmetry flow on the inner and outer surface of the tail forced the structural deflection offsetting the outboard. The frequency of the 2nd bending mode of the tail structure meets the peak frequency of the pressure fluctuation upon the tail surface, and the resonance phenomenon was observed. Therefore, the 2nd bending responses govern the flow field surrounding the vertical tail. Finally, the displacement of the vertical tail is small, while the acceleration with a large quantitation forces the vertical tail undergoing severe addition inertial loads.

A Rotor-Fixed Modal Simulation Model for Flexible Rotating Equipment

1974 ◽  
Vol 96 (2) ◽  
pp. 659-669 ◽  
Author(s):  
D. W. Childs
Keyword(s):  
Theory Of Elasticity ◽  
Rigid Bodies ◽  
Distributed Parameter ◽  
Flexible Rotor ◽  
Fixed Frame ◽  
Small Deflection ◽  
Bending Mode ◽  
Engine System ◽  
Typical Model ◽  
Modal Coordinates

A transient, flexible rotor formulation is derived on the basis of a representation previously employed to simulate the motion of flexible spinning spacecraft. The distributed parameter characteristics of the rotor are approximated by modeling the rotor as an elastically connected group of n rigid bodies. The elastic rotor deflections of the component rigid bodies are defined in terms of a rotor-fixed frame of reference; hence, during constant synchronous whirling the elastic deflections appear to be constant. The model is initially simplified by the traditional small deflection assumptions of the theory of elasticity, and is additionally simplified by the use of modal coordinates. Modal coordinates dramatically reduce the dimensionality of the model, and significantly clarify the dynamic analysis of the problem. Required data input to the model, and typical model output are demonstrated for the Mark 15-F turbopump of the Rocketdyne J-2 engine system. The model is shown to correctly demonstrate the form of unstable rotor whirling associated with internal hysteresis damping when operating above the first bending-mode critical speed.

Structural Dynamic and Aeroelastic Finite Element Simulation of an F-18 Tail Rudder: Impact of Adding a Control Surface

2005 ◽  
Author(s):  
Kevin R. Anderson ◽  
Kevin White ◽  
Wayne McEntire
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Control Surface ◽  
Maximum Pressure ◽  
Element Analysis ◽  
Structural Dynamic ◽  
Torsional Mode ◽  
Bending Mode ◽  
Aeroelastic Simulations ◽  
Bending Modes

This paper presents the findings of a Finite Element Analysis (FEA) based aeroelastic analysis performed on the F-18 tail rudder using MacNeal-Schwendler (MSC) suite of commercial FEA codes. The purpose of the study was to examine the stabilizing effects of adding a control surface to the tail wing, in this case the control surface is the tail rudder. MSC NASTRAN modal analysis and aeroelastic simulations were employed to carry out the investigation. Results are presented herein for the fundamental modes subject to a structural dynamics analysis and a series of supersonic 4G rolling maneuvers. Without a control surface, modal analysis yielded the following; 1st bending mode = 17.098 Hz, 1st torsional mode = 53.879 Hz, 2nd bending mode = 80.531 Hz, and 2nd torsional mode = 117.15 Hz. By adding the of rudder, the following is found; 1st bending mode = 17.797 Hz, 1st torsional mode = 48.266 Hz, 2nd torsional mode = 61.267 Hz, and 2nd bending mode = 81.142 Hz. Hence, adding the control surface, changes the precedence of the 2nd torsional and 2nd bending modes. Aeroelasticity predictions show that for a 100% increase in Mach number, the maximum pressure on the control surface increases by 93%.

Muffler of High Quality and Efficiency Based on Structural Dynamic Optimization and the Modal Analysis

2013 ◽  
Vol 753-755 ◽  
pp. 1156-1160
Author(s):  
Xin Xiang Zhou ◽  
Da Meng Han ◽  
Xing Long Lei ◽  
Cheng Liu ◽  
Guang Yu Hu
Keyword(s):  
Modal Analysis ◽  
Dynamic Optimization ◽  
Noise Source ◽  
Peak Frequency ◽  
Optimization Method ◽  
Expansion Chamber ◽  
Structural Dynamic ◽  
Air Inlet ◽  
High Efficient ◽  
Inherent Frequency

According to the mechanism and spectrum characteristics of an oil-free air compressor noise source, determined the muffler installed at the air inlet. According to the characteristics of noise source, muffler is designed into type of expansion chamber, considering the structural dynamic parameters, by means of optimization method to determine the size, and the finite element modal analysis is conducted. By solving the muffler's inherent frequency and mode of vibration, knows weather each order natural frequency is away from the peak frequency, the structural dynamics of the muffler can be modification. Methods of structure modal analysis and dynamic optimization on the muffler provided reliable reference to design a high efficient new muffler.

scholarly journals Anomalous effect in Schumann resonance phenomena observed in Japan, possibly associated with the Chi-chi earthquake in Taiwan

2005 ◽  
Vol 23 (4) ◽  
pp. 1335-1346 ◽  
Author(s):  
M. Hayakawa ◽  
K. Ohta ◽  
A. P. Nickolaenko ◽  
Y. Ando
Keyword(s):  
Frequency Shift ◽  
Main Shock ◽  
Peak Frequency ◽  
Resonance Mode ◽  
Resonance Phenomenon ◽  
Meridian Plane ◽  
Schumann Resonance ◽  
Anomalous Effect ◽  
Arrival Angle ◽  
Small Magnitude

Abstract. The Schumann resonance phenomenon has been monitored at Nakatsugawa (near Nagoya) in Japan since the beginning of 1999, and due to the occurance of a severe earthquake (so-called Chi-chi earthquake) on 21 September 1999 in Taiwan we have examined our Schumann resonance data at Nakatsugawa during the entire year of 1999. We have found a very anomalous effect in the Schumann resonance, possibly associated with two large land earthquakes (one is the Chi-chi earthquake and another one on 2 November 1999 (Chia-yi earthquake) with a magnitude again greater than 6.0). Conspicuous effects are observed for the larger Chi-chi earthquake, so that we summarize the characteristics for this event. The anomaly is characterized mainly by the unusual increase in amplitude of the fourth Schumann resonance mode and a significant frequency shift of its peak frequency (~1.0Hz) from the conventional value on the By magnetic field component which is sensitive to the waves propagating in the NS meridian plane. Anomalous Schumann resonance signals appeared from about one week to a few days before the main shock. Secondly, the goniometric estimation of the arrival angle of the anomalous signal is found to coincide with the Taiwan azimuth (the unresolved dual direction indicates toward South America). Also, the pulsed signals, such as the Q-bursts, were simultaneously observed with the "carrier" frequency around the peak frequency of the fourth Schumann resonance mode. The anomaly for the second event for the Chia-yi earthquake on 2 November had much in common. But, most likely due to a small magnitude, the anomaly appears one day before and lasts until one day after the main shock, with the enhancement at the fourth Schumann resonance mode being smaller in amplitude than the case of the Chi-chi earthquake. Yet, the other characteristics, including the goniometric direction finding result, frequency shift, etc., are nearly the same. Although the emphasis of the present study is made on experimental aspects, a possible generation mechanism for this anomaly is discussed in terms of the ELF radio wave scattered by a conducting disturbance, which is likely to take place in the middle atmosphere over Taiwan. Model computations show that the South American thunderstorms (Amazon basin) play the leading role in maintaining radio signals, leading to the anomaly in the Schumann resonance.

Ultrastructure of Cercarial Tails

1974 ◽  
Vol 32 ◽  
pp. 180-181
Author(s):  
Richard S. Demaree ◽  
Donald M. Wootton
Keyword(s):  
Schistosoma Japonicum ◽  
Intermediate Hosts ◽  
Suitable Host ◽  
Ultrastructural Studies ◽  
Tail Structure

Cercariae (juvenile trematodes with tails) emerge from mollusk intermediate hosts and swim toward definitive hosts or encystment objects. The locomotor power is furnished by the tail. Upon reaching a suitable host or encystment object, the tail is cast off and the cercariae penetrate and/or encyst. Ultrastructural studies of cercariae are sparse. There is even lessUltrastructural studies of cercariae are sparse. There is even less information about the tail structure; and body-to-tail morphology has been documented only for Acanthatrium oregonense and Schistosoma japonicum.

Spectral analysis with a minimal basis functions approach for quantification of ligand-receptor dynamic PET study

2005 ◽  
Vol 25 (1_suppl) ◽  
pp. S634-S634 ◽  
Author(s):  
Yun Zhou ◽  
Weiguo Ye ◽  
James R Brasic ◽  
Mohab Alexander ◽  
John Hilton ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Basis Functions ◽  
Dynamic Pet ◽  
Minimal Basis

Estimation of Competitiveness of Single-Industry Towns of the Samara Region

2020 ◽  
pp. 67-81
Author(s):  
Julia Rishatovna Kuzhanbaeva ◽  
Rustam Taufihovich Kuzhanbaev ◽  
Maria S. Guseva
Keyword(s):  
Social Services ◽  
System Analysis ◽  
Objective Assessment ◽  
Practical Interest ◽  
Federal District ◽  
Social Consequences ◽  
Statistical Parameters ◽  
Structural Dynamic ◽  
Single Industry ◽  
Integral Indicator

In order to prevent negative socio-economic trends, to predict the social consequences of decisions on the implementation of state policy in the development of single-industry territories, public authorities monitor the socio-economic situation in single-industry towns based on an assessment of a number of statistical indicators. Such a differentiated assessment of statistical parameters does not allow a comprehensive assessment of the level of development and competitiveness of a single-industry town by territory, which is of particular relevance in modern conditions of glocalization. Of particular scientific and practical interest is a comparative analysis of the level of development of single-industry towns on the basis of an integral indicator that takes into account aspects of various spheres of life of the population and allows an objective assessment of the competitive positions of single-industry territories, which is currently not used by state authorities for monitoring. The purpose of the work is to assess and justify the conditions and development trends of single-industry towns of the Samara region on the basis of calculating the integral indicator of competitiveness, taking into account the level of development of the economy, finance, employment, social security and demography, as well as the mono-profile level of territories. In this study, we used the methods of system analysis, the method of comparisons and analogies, the method of generalization, the methods of dialectic and statistical analysis, the method of expert estimates, the method of retrospective estimates and structural-dynamic analysis. The paper provides an overview of the single-industry towns of the regions of the Volga Federal District; the results of testing the methodology for assessing the competitiveness of single-industry towns of the Samara region on the basis of an integral indicator are presented and trends in its change in the period 2013–2017 are identified. The study involved four single-industry towns of the Samara region: Oktyabrsk, Pohvistnevo, Tolyatti, Chapaevsk. The calculations showed that For five years Oktyabrsk was an outsider in four of the six areas under study (economics, labor, social services, demography), which led to the lowest competitiveness index and allowed us to identify the competitiveness of a single-industry town as “below average”. In relatively equal socio-economic conditions, there were Pohvistnevo, Togliatti and Chapaevsk, the level of competitiveness of which is “above average”.

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