Kinematic characteristics of longitudinal double folding wings

2021 ◽  
pp. 1-25
Author(s):  
L. Tiegang ◽  
C. Guoguang ◽  
L. Shuai
Keyword(s):  
Angular Velocity ◽  
Structural Model ◽  
Initial Conditions ◽  
Aerodynamic Force ◽  
Model Simulation ◽  
Lagrange Equation ◽  
Grid Method ◽  
Weapon Systems ◽  
Folding Wing ◽  
Double Folding

ABSTRACT A folding wing is a tactical missile launching device that needs to be miniaturised to facilitate storage, transportation, and launching; save missile and transportation space; and improve the combat capability of weapon systems. This study investigates the aeroelastic characteristics of the secondary longitudinal folding wing during the unfolding process. First, the Lagrange equation is used to establish the structural dynamics model of the folding wing, the kinematics characteristics during the deformation process are analysed, and the unfolding movement of the folding wing is obtained using the dynamic equations in the process. Then, the generalised unsteady aerodynamic force is calculated using the dipole grid method, and the multi-body dynamics equation of the folding wing is obtained. The initial angular velocity required for the deployment of the folding wing is analysed through structural model simulation, and the influence of the initial angular velocity on the opening process is studied. Finally, aeroelastic flutter analysis is performed on the folding wing, and the physical model of the folding wing verified experimentally. Results show that the type of aeroelastic response is sensitive to the initial conditions and the way the folding wing opens.

scholarly journals Estimating Changes in Temperature Distributions in a Large Ensemble of Climate Simulations Using Quantile Regression

2018 ◽  
Vol 31 (20) ◽  
pp. 8573-8588 ◽  
Author(s):  
Matz A. Haugen ◽  
Michael L. Stein ◽  
Elisabeth J. Moyer ◽  
Ryan L. Sriver
Keyword(s):  
Quantile Regression ◽  
Radiative Forcing ◽  
Initial Conditions ◽  
Model Simulation ◽  
Extreme Temperature ◽  
Single Model ◽  
New Approach ◽  
Temperature Distributions ◽  
Climate Simulations ◽  
Community Earth System Model

Understanding future changes in extreme temperature events in a transient climate is inherently challenging. A single model simulation is generally insufficient to characterize the statistical properties of the evolving climate, but ensembles of repeated simulations with different initial conditions greatly expand the amount of data available. We present here a new approach for using ensembles to characterize changes in temperature distributions based on quantile regression that more flexibly characterizes seasonal changes. Specifically, our approach uses a continuous representation of seasonality rather than breaking the dataset into seasonal blocks; that is, we assume that temperature distributions evolve smoothly both day to day over an annual cycle and year to year over longer secular trends. To demonstrate our method’s utility, we analyze an ensemble of 50 simulations of the Community Earth System Model (CESM) under a scenario of increasing radiative forcing to 2100, focusing on North America. As previous studies have found, we see that daily temperature bulk variability generally decreases in wintertime in the continental mid- and high latitudes (>40°). A more subtle result that our approach uncovers is that differences in two low quantiles of wintertime temperatures do not shrink as much as the rest of the temperature distribution, producing a more negative skew in the overall distribution. Although the examples above concern temperature only, the technique is sufficiently general that it can be used to generate precise estimates of distributional changes in a broad range of climate variables by exploiting the power of ensembles.

Prediction of Slamming Loads on Catamaran Wetdeck Using CFD

2015 ◽  
Author(s):  
Ahmed Swidan ◽  
Giles Thomas ◽  
Dev Ranmuthugala ◽  
Irene Penesis ◽  
Walid Amin ◽  
...  
Keyword(s):  
Model Simulation ◽  
Three Dimensional ◽  
Grid Method ◽  
Computationally Efficient ◽  
Overset Grid ◽  
Force Magnitude ◽  
Overset Grid Method ◽  
Drop Tests ◽  
Transient Velocity ◽  
Transient Velocity Profile

Wetdeck slamming is one of the principal hydrodynamic loads acting on catamarans. CFD techniques are shown to successfully characterise wetdeck slamming loads, as validated through a series of controlled-speed drop tests on a three-dimensional catamaran hullform model. Simulation of water entry at constant speed by applying a fixed grid method was found to be more computationally efficient than applying an overset grid. However, the overset grid method for implementing the exact transient velocity profile resulted in better prediction of slam force magnitude. In addition the splitting force concurrent with wetdeck slam event was quantified to be 21% of the vertical slamming force.

Design and analysis of a propulsion mechanism using modular umbrella-like wings

2018 ◽  
Vol 122 (1249) ◽  
pp. 349-368
Author(s):  
F. Gao ◽  
J. G. Lv ◽  
X. C. Zhang
Keyword(s):  
Structural Model ◽  
Aerodynamic Force ◽  
Inertial Force ◽  
Structure Design ◽  
Symmetrical Structure ◽  
Propulsion Mechanism ◽  
New Type ◽  
Practical Guidance ◽  
Mechanical Performances ◽  
Relationship Of

ABSTRACTThis article describes the design and evaluation of a new type of propulsion mechanism that uses modular umbrella-like wings oscillating symmetrically in counterphase to generate thrust. The principle of the propulsion and movement of the modular umbrella-like wings was first developed, and the mechanism used to implement the movement of the modular wings was subsequently designed. A structural model and the assembly relationship of the propulsion mechanism were developed for prototype fabrication. An experiment was established to measure the kinematic and mechanical performances of the propulsion mechanism for different reciprocating frequencies and travels. The results for the single umbrella-like wing indicate that either increasing the frequency or enlarging the travel can enhance the average aerodynamic force generated by the wing in one cycle. The results for the modular umbrella-like wings demonstrate that the inertial force generated by the mechanism can be balanced using a symmetrical structure. The average aerodynamic force would be markedly enhanced by increasing the percentage of the time that the outspread wing is moving downwards; e.g. the average aerodynamic force generated by the modular umbrella-like wings was increased by 85.84% compared to the value for a single umbrella-like wing for the same travel and frequency. This work provides practical guidance for optimising the structure design.

scholarly journals Interannual Variations of Summer Monsoons: Sensitivity to Cloud Radiative Forcing

1998 ◽  
Vol 11 (8) ◽  
pp. 1883-1905 ◽  
Author(s):  
O. P. Sharma ◽  
H. Le Treut ◽  
G. Sèze ◽  
L. Fairhead ◽  
R. Sadourny
Keyword(s):  
Optical Properties ◽  
Radiative Forcing ◽  
General Circulation ◽  
Initial Conditions ◽  
Model Simulation ◽  
Circulation Model ◽  
Interannual Variations ◽  
Radiative Effects ◽  
High Concentration ◽  
Sea Temperature

Abstract The sensitivity of the interannual variations of the summer monsoons to imposed cloudiness has been studied with a general circulation model using the initial conditions prepared from the European Centre for Medium-Range Forecasts analyses of 1 May 1987 and 1988. The cloud optical properties in this global model are calculated from prognostically computed cloud liquid water. The model successfully simulates the contrasting behavior of these two successive monsoons. However, when the optical properties of the observed clouds are specified in the model runs, the simulations show some degradation over India and its vicinity. The main cause of this degradation is the reduced land–sea temperature contrast resulting from the radiative effects of the observed clouds imposed in such simulations. It is argued that the high concentration of condensed water content of clouds over the Indian land areas will serve to limit heating of the land, thereby reducing the thermal contrast that gives rise to a weak Somali jet. A countermonsoon circulation is, therefore, simulated in the vector difference field of 850-hPa winds from the model runs with externally specified clouds. This countermonsoon circulation is associated with an equatorial heat source that is the response of the model to the radiative effects of the imposed clouds. Indeed, there are at least two clear points that can be made: 1) the cloud–SST patterns, together, affect the interannual variability; and 2) with both clouds and SST imposed, the model simulation is less sensitive to initial conditions. Additionally, the study emphasizes the importance of dynamically consistent clouds developing in response to the dynamical, thermal, and moist state of the atmosphere during model integrations.

scholarly journals Solving a Problem of Rotary Motion for a Heavy Solid Using the Large Parameter Method

2020 ◽  
Vol 2020 ◽  
pp. 1-7 ◽  
Author(s):  
A. I. Ismail
Keyword(s):  
Angular Velocity ◽  
Small Parameter ◽  
Initial Conditions ◽  
Geometric Interpretation ◽  
Rigid Bodies ◽  
Parameter Method ◽  
Large Parameter ◽  
Small Parameter Method ◽  
Rotational Motions ◽  
The Stability

The small parameter method was applied for solving many rotational motions of heavy solids, rigid bodies, and gyroscopes for different problems which classify them according to certain initial conditions on moments of inertia and initial angular velocity components. For achieving the small parameter method, the authors have assumed that the initial angular velocity is sufficiently large. In this work, it is assumed that the initial angular velocity is sufficiently small to achieve the large parameter instead of the small one. In this manner, a lot of energy used for making the motion initially is saved. The obtained analytical periodic solutions are represented graphically using a computer program to show the geometric periodicity of the obtained solutions in some interval of time. In the end, the geometric interpretation of the stability of a motion is given.

scholarly journals Dynamic Analysis of Impact Model of Slipping Tramcar Prevention Equipment Based on an Energy Absorber

2016 ◽  
Vol 2016 ◽  
pp. 1-10
Author(s):  
Guiyun Xu ◽  
Shuo Hu ◽  
Xiaoguang Zhang ◽  
Jiazhou Zhu ◽  
Huipeng Zheng ◽  
...  
Keyword(s):  
Field Experiments ◽  
Initial Conditions ◽  
Lagrange Equation ◽  
Maximum Error ◽  
Key Factors ◽  
Energy Absorber ◽  
Safety Production ◽  
Braking Distance ◽  
Theoretical Results ◽  
Distance Formula

The protection equipment of slipping tramcar in inclined shaft is the important safety equipment to ensure safety production in mine transportation and equipment. The Slipping Tramcar Prevention Equipment is mainly composed of an intercepting door and a buffering system, in which an energy absorber is the key component. The braking dynamic model of the energy absorber is studied by establishing a Lagrange equation and simulating the braking progress by the software of Simulink. The braking simulation distances curves of the energy absorber are obtained under the different initial conditions of tramcar mass and velocity, which shows that the tramcar velocity and mass both have a significant influence on the braking distance. The analysis on variance and range is developed for further comparison on the two key factors implying that tramcar mass is of the most great importance. Moreover, a braking distance formula is built based on the analysis results. On the other hand, field experiments are conducted in Qishan Mine, and experiment results show that the maximum error between the braking distance formula value and the experiment value is 11.98%, and the minimum error is 2.72%. The experimental results are consistent with the theoretical results.

Multibody Modeling and Simulation of Monocopter Micro Air Vehicle

2015 ◽  
Vol 772 ◽  
pp. 401-409
Author(s):  
Mehrdad Ebrahimi Dormiyani ◽  
Afshin Banazadeh ◽  
Fariborz Saghafi
Keyword(s):  
Degrees Of Freedom ◽  
Initial Conditions ◽  
Model Simulation ◽  
Static Stability ◽  
Flight Simulation ◽  
Control Surface ◽  
Free Flight ◽  
Nonlinear Simulation ◽  
Multibody Model ◽  
Air Vehicle

In the current paper, seven degrees of freedom multibody model of a monocopter air vehicle is developed based on the Newton-Euler approach along with nonlinear simulation in different flight phases. Aerodynamic forces and moments are modeled using blade element momentum theory. The sole control surface is modeled like a conventional flap on a wing. Free flight simulation is performed in MATLAB Simulink environment to evaluate the behavior of the system and to demonstrate the effectiveness and applicability of the proposed model. Simulation results show harmonic oscillations in Euler angles, linear and angular velocities that are consistent with the physics and mathematical foundations. Static stability of the vehicle is evident in free flight by careful choice of initial conditions. The presented multibody model is useful for comparative study and design purposes.

scholarly journals Manufactured solutions and the verification of three-dimensional Stokes ice-sheet models

2013 ◽  
Vol 7 (1) ◽  
pp. 19-29 ◽  
Author(s):  
W. Leng ◽  
L. Ju ◽  
M. Gunzburger ◽  
S. Price
Keyword(s):  
Computational Models ◽  
Analytic Solution ◽  
Initial Conditions ◽  
Model Simulation ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Solution Technique ◽  
Order Partial Differential Equation ◽  
Manufactured Solutions ◽  
Manufactured Solution

Abstract. The manufactured solution technique is used for the verification of computational models in many fields. In this paper, we construct manufactured solutions for the three-dimensional, isothermal, nonlinear Stokes model for flows in glaciers and ice sheets. The solution construction procedure starts with kinematic boundary conditions and is mainly based on the solution of a first-order partial differential equation for the ice velocity that satisfies the incompressibility condition. The manufactured solutions depend on the geometry of the ice sheet, basal sliding parameters, and ice softness. Initial conditions are taken from the periodic geometry of a standard problem of the ISMIP-HOM benchmark tests. The upper surface is altered through the manufactured solution procedure to generate an analytic solution for the time-dependent flow problem. We then use this manufactured solution to verify a parallel, high-order accurate, finite element Stokes ice-sheet model. Simulation results from the computational model show good convergence to the manufactured analytic solution.

Simulation of Oscillation Response of Free-Standing Object under Earthquakes

2011 ◽  
Vol 105-107 ◽  
pp. 417-422
Author(s):  
Qian Zhou ◽  
Wei Ming Yan
Keyword(s):  
Friction Coefficient ◽  
Simulation Analysis ◽  
Initial Conditions ◽  
Model Simulation ◽  
Dynamic Balance ◽  
Earthquake Intensity ◽  
Free Standing ◽  
Motion Equations ◽  
Object A ◽  
Simulink Model

To protect free-standing object,a rectangular object is taken as example and by SIMULINK technique its oscillation response under earthquakes were studied.Based on static and dynamic balance theories,oscillation conditions as well as motion equations of the free-standing object under earthquakes were deduced;Based on SIMULINK model,simulation analysis on the object under both level and vertical earthquakes were carried out,parameters such as initial conditions,earthquake intensity and ratio of width of the object against its height (B/H) and so on were discussed.Results show that under earthquakes oscillation conditions of the object relate closely to B/H,earthquake intensity and friction coefficient between object and its base;Under earthquakes oscillation response of the object is sensitive to initial conditions,and the response becomes more serious under less B/H or larger earthquake intensity conditions.Besides, SIMULINK technique can effectively simulate oscillation response of free-standing object under earthquakes,which proves the technique useful.

Modeling and Test of Aerodynamic Force for a Piezoelectric Transducer Drive Mechanism

2014 ◽  
Vol 631-632 ◽  
pp. 610-613
Author(s):  
Jing Lu ◽  
Yan Fang Hang ◽  
Ying Jun Hu
Keyword(s):  
Piezoelectric Transducer ◽  
Aerodynamic Force ◽  
Model Simulation ◽  
Aerodynamic Characteristics ◽  
System Model ◽  
Force Model ◽  
Initial Angle ◽  
Drive Mechanism ◽  
Force Mode ◽  
Comparison Of The Results

To reduce the complexity structure of a flapping rotor, a piezoelectric transducer drive mechanism is designed to achieve active flapping and passive rotary motion. Then, its aerodynamic force model is built by using Theodorsen's theory in order to analyze the aerodynamic characteristics of this system. Model simulation and experimental results show that flapping amplitude, flapping frequency and initial angle of attack make a significant role for aerodynamic characteristics. The effectiveness of aerodynamic force mode also can be seen from the comparison of the results.

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