scholarly journals New Method for Analyzing the Flutter Stability of Hingeless Blades with Advanced Geometric Configurations in Hovering

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Si-wen Wang ◽  
Jing-long Han ◽  
Quan-long Chen ◽  
Hai-wei Yun ◽  
Xiao-mao Chen
Keyword(s):  
Structural Analysis ◽  
Usual Method ◽  
New Method ◽  
Analysis Tool ◽  
Fe Model ◽  
Beam Model ◽  
Lattice Method ◽  
Aspect Ratios ◽  
Strip Theory ◽  
Doublet Lattice Method

A new method used to analyze the aeroelastic stability of a helicopter hingeless blade in hovering has been developed, which is especially suitable for a blade with advanced geometric configuration. This method uses a modified doublet-lattice method (MDLM) and a 3-D finite element (FE) model for building the aeroelastic equation of a blade in hovering. Thereafter, the flutter solution of the equation is calculated by the V-g method, assuming blade motions to be small perturbations about the steady equilibrium deflection. The MDLM, which is suitable to calculate the unsteady aerodynamic force of nonplanar rotor blade in hovering, is developed from the doublet-lattice method (DLM). The structural analysis tool is the commercial software ANSYS. The comparisons of the obtained results against those in the literatures show the capabilities of the MDLM and the method of structural analysis. The flutter stabilities of swept tip blades with different aspect ratios are analyzed using the new method developed in this work and the usual method on the basis of the unsteady strip theory and beam model. It shows that considerable differences appear in the flutter rotational velocities with the decrease of the aspect ratio. The flutter rotational velocities obtained by the present method are evidently lower than those obtained by the usual method.

2D and 3D low frequency aerodynamics

2008 ◽  
Vol 112 (1136) ◽  
pp. 609-612
Author(s):  
L. H. van Zyl
Keyword(s):  
Three Dimensional ◽  
Low Frequency ◽  
Lattice Method ◽  
Panel Methods ◽  
Strip Theory ◽  
Doublet Lattice Method ◽  
2D And 3D ◽  
The Relationship ◽  
Aircraft Configurations ◽  
Theoretical Results

Abstract Unsteady aerodynamic loads on aircraft configurations are used for aeroelastic or flight dynamic analyses. The sources for deriving these loads include strip theory aerodynamics and three-dimensional panel methods. In some applications the behaviour of the unsteady air loads as the frequency approaches zero is important, and it is well known that the behaviour of strip theory aerodynamics employing the exact circulation function differs qualitatively from that of the three-dimensional panel methods such as the subsonic doublet lattice method (DLM). Theoretical results from an earlier study of the low frequency behaviour of the DLM are used here to show the relationship between the DLM and strip theory and the relationship is verified by a numerical example.

scholarly journals Influence of Pile Diameter and Aspect Ratio on the Lateral Response of Monopiles in Sand with Different Relative Densties

2021 ◽  
Vol 9 (6) ◽  
pp. 618
Author(s):  
Huan Wang ◽  
Lizhong Wang ◽  
Yi Hong ◽  
Amin Askarinejad ◽  
Ben He ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Large Diameter ◽  
Pressure Coefficient ◽  
Offshore Wind ◽  
Fe Model ◽  
Soil Pressure ◽  
Pile Diameter ◽  
Centrifuge Tests ◽  
Aspect Ratios ◽  
Wide Range

The large-diameter monopiles are the most preferred foundation used in offshore wind farms. However, the influence of pile diameter and aspect ratio on the lateral bearing behavior of monopiles in sand with different relative densities has not been systematically studied. This study presents a series of well-calibrated finite-element (FE) analyses using an advanced state dependent constitutive model. The FE model was first validated against the centrifuge tests on the large-diameter monopiles. Parametric studies were performed on rigid piles with different diameters (D = 4–10 m) and aspect ratios (L/D = 3–7.5) under a wide range of loading heights (e = 5–100 m) in sands with different relative densities (Dr = 40%, 65%, 80%). The API and PISA p-y models were systematically compared and evaluated against the FE simulation results. The numerical results revealed a rigid rotation failure mechanism of the rigid pile, which is independent of pile diameter and aspect ratio. The computed soil pressure coefficient (K = p/Dσ′v) of different diameter piles at same rotation is a function of z/L (z is depth) rather than z/D. The force–moment diagrams at different deflections were quantified in sands of different relative density. Based on the observed pile–soil interaction mechanism, a simple design model was proposed to calculate the combined capacity of rigid piles.

Effect of Steady Rest in Cylindrical Traverse Grinding of Slender Workpiece

2020 ◽  
Author(s):  
Hidetaka Fujii ◽  
Takashi Onishi ◽  
Chinhu Lin ◽  
Moriaki Sakakura ◽  
Kazuhito Ohashi
Keyword(s):  
Elastic Deformation ◽  
Contact Point ◽  
Traverse Speed ◽  
Grinding Force ◽  
New Method ◽  
Beam Model ◽  
Shape Error ◽  
Form Error ◽  
Low Stiffness ◽  
Traverse Grinding

Abstract In the case of traverse grinding of a slender workpiece, the ground workpiece is easily deformed by the normal grinding force due to its low stiffness. To reduce the form error caused by the elastic deformation of the workpiece, a steady rest is widely used. Generally, a steady rest is set to push the ground area of the workpiece. However, the stepped shape error is generated at the contact point where a steady rest pushed the workpiece because the pushing force of a steady rest is decreased after the material of the contact point is removed. In this study, to reduce the stepped shape error of the ground workpiece, we proposed a new method to set a steady rest. In this method, the steady rest was set to push the area where was not ground. In addition, the traverse speed of the workpiece was adjusted to keep the elastic deformation of the workpiece constant. The suitable method to control the traverse speed was estimated by using a beam model that could simulate the elastic deformation of the workpiece during the grinding process. It was confirmed that the new method could improve the form accuracy of a slender workpiece through grinding experiments.

Comparison of flutter calculation methods based on ground vibration test result

2019 ◽  
Vol 91 (3) ◽  
pp. 466-476
Author(s):  
Wojciech Chajec
Keyword(s):  
Low Cost ◽  
Ground Vibration ◽  
Control Surface ◽  
Vibration Test ◽  
Problem Solution ◽  
Lattice Method ◽  
Mass Model ◽  
Content Type ◽  
Strip Theory ◽  
Flutter Analysis

PurposeA low-cost but credible method of low-subsonic flutter analysis based on ground vibration test (GVT) results is presented. The purpose of this paper is a comparison of two methods of immediate flutter problem solution: JG2 – low cost software based on the strip theory in aerodynamics (STA) and V-g method of the flutter problem solution and ZAERO I commercial software with doublet lattice method (DLM) aerodynamic model and G method of the flutter problem solution. In both cases, the same sets of measured normal modes are used. Design/methodology/approachBefore flutter computation, resonant modes are supplied by some non-measurable but existing modes and processed using the author’s own procedure. For flutter computation, the modes are normalized using the aircraft mass model. The measured mode orthogonalization is possible. The flutter calculation made by means of both methods are performed for the MP-02 Czajka UL aircraft and the Virus SW 121 aircraft of LSA category. FindingsIn most cases, both compared flutter computation results are similar, especially in the case of high aspect wing flutter. The Czajka T-tail flutter analysis using JG2 software is more conservative than the one made by ZAERO, especially in the case of rudder flutter. The differences can be reduced if the proposed rudder effectiveness coefficients are introduced. Practical implicationsThe low-cost methods are attractive for flutter analysis of UL and light aircraft. The paper presents the scope of the low-cost JG2 method and its limitations. Originality/valueIn comparison with other works, the measured generalized masses are not used. Additionally, the rudder effectiveness reduction was implemented into the STA. However, Niedbal (1997) introduced corrections of control surface hinge moments, but the present work contains results in comparison with the outcome obtained by means of the more credible software.

Coupling of a Reactor Analysis Code and a Lower Head Thermal Analysis Solver

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Hiroshi Madokoro ◽  
Alexei Miassoedov ◽  
Thomas Schulenberg
Keyword(s):  
Structural Analysis ◽  
Message Passing ◽  
Message Passing Interface ◽  
Severe Accident ◽  
Coupled Analysis ◽  
Accident Analysis ◽  
Analysis Tool ◽  
Lower Head ◽  
Calculation Results ◽  
Reactor Pressure

Due to the recent high interest on in-vessel melt retention (IVR), development of detailed thermal and structural analysis tool, which can be used in a core-melt severe accident, is inevitable. Although RELAP/SCDAPSIM is a reactor analysis code, originally developed for U.S. NRC, which is still widely used for severe accident analysis, the modeling of the lower head is rather simple, considering only a homogeneous pool. PECM/S, a thermal structural analysis solver for the reactor pressure vessel (RPV) lower head, has a capability of predicting molten pool heat transfer as well as detailed mechanical behavior including creep, plasticity, and material damage. The boundary condition, however, needs to be given manually and thus the application of the stand-alone PECM/S to reactor analyses is limited. By coupling these codes, the strength of both codes can be fully utilized. Coupled analysis is realized through a message passing interface, OpenMPI. The validation simulations have been performed using LIVE test series and the calculation results are compared not only with the measured values but also with the results of stand-alone RELAP/SCDAPSIM simulations.

scholarly journals 3D Finite Element Model Simulating the Behaviour of Filling Soils Used to Set Up a New Placement Method for Separate Sewer Systems

2019 ◽  
Vol 8 (3) ◽  
pp. 87-98
Author(s):  
Alaa Abbas ◽  
Felicite Ruddock ◽  
Rafid Alkhaddar ◽  
Glynn Rothwell ◽  
Iacopo Carnacina ◽  
...  
Keyword(s):  
Finite Element ◽  
Soil Properties ◽  
Model Simulation ◽  
New Method ◽  
Traffic Load ◽  
Scale Model ◽  
Fe Model ◽  
Fe Method ◽  
Buried Pipes ◽  
The Impact

The use of a finite element (FE) method and selection of the appropriate model to simulate soil elastoplastic behaviour has confirmed the importance and sensitivity of the soil properties on the accuracy when compared with experimental data. The properties of the filling soil play a significant role in determining levels of deformation and displacement of both the soil and subterranean structures when using the FE model simulation. This paper investigates the impact of the traffic load on the filling soil deformation when using the traditional method, one pipe in a trench, and a new method, two pipes in a single trench one over the other, for setting up a separate sewer system. The interaction between the buried pipes and the filling soils has been simulated using an elastoplastic FE model. A modified Drucker–Prager cap constitutive model was used to simulate the stress-strain behaviours of the soil. A series of laboratory tests were conducted to identify the elastoplastic properties of the composite soil used to bury the pipes. The FE models were calibrated using a physical lab model for testing the buried pipes under applied load. This allows the FE model to be confidently upgraded to a full-scale model. The pipe-soil interactions were found to be significantly influenced by the soil properties, the method of placing the pipes in the trench and the diameters of the buried pipes. The deformation of the surface soil was decreased by approximately 10% when using the new method of setting up the separate sewer.

scholarly journals Design and Structural Analysis of a Rack System for Using in Agriculture

2018 ◽  
Vol 66 (3) ◽  
pp. 641-646
Author(s):  
Miroslav Blatnický ◽  
Ján Dižo ◽  
Dalibor Barta
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Structural Analysis ◽  
Fe Model ◽  
Steel Tubes ◽  
Shell Elements ◽  
Human Power ◽  
Construction Design ◽  
Pull Out ◽  
Pressure Pipeline

The paper deals with a construction design and structural analysis of the rack system which will be used for storage of steel tubes of pressure pipeline for fodder mixtures transportation in agricultural company. Structure of the designed equipment is made by the welding of steel parts and consists of the main framework and four pull-out racks on both sides. Racks move by means of human power through a rotating crank. Every individual pull-out racks is able to carries pipes of various dimensions, both length and diameter with total weight up to 3 tons with respect to customer requests. Since it is a prototype’s structure, we have designed main dimensions of it, material and technology for production and performed also structural analyses as the integral part of every engineering design. Structural analyses were conducted by means of numeric procedure known as finite element method. With respect to the used steel profiles shell elements were used for FE model. Analyses were performed for maximal loading cases in order to identify the level of safety in the most exposed locations of the structure.

Further Refinement of the Subsonic Doublet-Lattice Method

1998 ◽  
Vol 35 (5) ◽  
pp. 720-727 ◽  
Author(s):  
William P. Rodden ◽  
Paul F. Taylor ◽  
Samuel C. McIntosh
Keyword(s):  
Lattice Method ◽  
Doublet Lattice Method

scholarly journals Synthesis of α-CaSO4·0.5H2O from flue gas desulfurization gypsum regulated by C4H4O4Na2·6H2O and NaCl in glycerol-water solution

RSC Advances ◽  
2017 ◽  
Vol 7 (44) ◽  
pp. 27807-27815 ◽  
Author(s):  
Qing-Jun Guan ◽  
Wei Sun ◽  
Yue-Hua Hu ◽  
Zhi-Gang Yin ◽  
Chang-Ping Guan
Keyword(s):  
Phase Transition ◽  
Flue Gas ◽  
Water Solution ◽  
Flue Gas Desulfurization ◽  
New Method ◽  
Glycerol Water ◽  
Aspect Ratios

A brand new method to prepare α-CaSO4·0.5H2O with low aspect ratios from flue gas desulfurization gypsum in glycerol-water solution was presented, in which NaCl was used as the phase transition accelerator and C4H4O4Na2·6H2O as the crystal modifier.

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