scholarly journals Comparative analysis of different numerical models of a steel radial gate

2018 ◽  
Vol 219 ◽  
pp. 02008
Author(s):  
Krzysztof Brusewicz ◽  
Robert Jankowski
Keyword(s):  
Computational Analysis ◽  
Numerical Models ◽  
Point Of View ◽  
Dynamic Resistance ◽  
Hydro Power ◽  
Water Management System ◽  
Shell Elements ◽  
Potential Damage ◽  
Radial Gate ◽  
Mining Tremors

Hydrotechnical structures are important components in water management system and general flooding safety. Their reliability should be ensured since potential damage might lead to catastrophic consequences. Weir gates are considered to be highly vulnerable elements of each hydro power plant, with regard to its dynamic resistance. The aim of the paper is to compare different numerical models and their influence on the results of a computational modal analysis of a steel radial gate. The investigation has been conducted for models using beam and shell elements, while assuring the same geometry, material properties and boundary conditions. The results of the comparative computational analysis indicate that the eigenmode shapes are similar for both models, while the corresponding eigenfrequencies are considerably different. These differences are important from the point of view of dynamic analysis, especially that the first eigenfrequency falls within the energy range typical for earthquakes and mining tremors.

scholarly journals Established Numerical Techniques for the Structural Analysis of a Regional Aircraft Landing Gear

2018 ◽  
Vol 2018 ◽  
pp. 1-21 ◽  
Author(s):  
F. Caputo ◽  
A. De Luca ◽  
A. Greco ◽  
A. Marro ◽  
A. Apicella ◽  
...  
Keyword(s):  
Finite Elements ◽  
Numerical Models ◽  
Three Dimensional ◽  
Landing Gear ◽  
Point Of View ◽  
Fe Model ◽  
One Dimensional ◽  
Reaction Forces ◽  
Local Technique ◽  
Stick Model

Usually during the design of landing gear, simplified Finite Element (FE) models, based on one-dimensional finite elements (stick model), are used to investigate the in-service reaction forces involving each subcomponent. After that, the design of such subcomponent is carried out through detailed Global/Local FE analyses where, once at time, each component, modelled with three-dimensional finite elements, is assembled into a one-dimensional finite elements based FE model, representing the whole landing gear under the investigated loading conditions. Moreover, the landing gears are usually investigated also under a kinematic point of view, through the multibody (MB) methods, which allow achieving the reaction forces involving each subcomponent in a very short time. However, simplified stick (FE) and MB models introduce several approximations, providing results far from the real behaviour of the landing gear. Therefore, the first goal of this paper consists of assessing the effectiveness of such approaches against a 3D full-FE model. Three numerical models of the main landing gear of a regional airliner have been developed, according to MB, “stick,” and 3D full-FE methods, respectively. The former has been developed by means of ADAMS® software, the other two by means of NASTRAN® software. Once this assessment phase has been carried out, also the Global/Local technique has verified with regard to the results achieved by the 3D full-FE model. Finally, the dynamic behaviour of the landing gear has been investigated both numerically and experimentally. In particular, Magnaghi Aeronautica S.p.A. Company performed the experimental test, consisting of a drop test according to EASA CS 25 regulations. Concerning the 3D full-FE investigation, the analysis has been simulated by means of Ls-Dyna® software. A good level of accuracy has been achieved by all the developed numerical methods.

scholarly journals Effects of strong mining tremors, and assessment of the buildings' resistance to the dynamic impacts

2018 ◽  
Vol 36 ◽  
pp. 01003 ◽  
Author(s):  
Izabela Bryt-Nitarska
Keyword(s):  
Urban Areas ◽  
Land Development ◽  
Actual State ◽  
Dynamic Resistance ◽  
Traditional Structure ◽  
Resistance Assessment ◽  
Dynamic Impacts ◽  
Mining Tremors ◽  
The Impact

A particularly important element in the assessment of the actual state of the threats which is caused by conducting the mining exploitation of seams bumping under the urban areas is to diagnose the condition of the land development after hard shocks. In the buildings, for which the impact of the mining activities, including the tremors, is not taken into account at the stage of design and formulation of the strength and use conditions, conclusions from the structure behaviour under the tremor influence are an essential part of the assessment of the possibility for transferring the further dynamic impacts. The use of conclusions from the in situ research has its role in anticipating the behaviour of the buildings in case of the forecast of the mining tremors effects in the regions of their impacts. These conclusions should also provide ground for the assumptions to the scope of the building prevention necessary to be taken in case of forecasting the tremors with big intensity. Based on the analysis of effects which occurred in the land development after the highenergy mining tremors, the elements of the dynamic resistance assessment for the buildings with traditional structure were discussed.

Review—Numerical Models for Dilute Gas-Particle Flows

1982 ◽  
Vol 104 (3) ◽  
pp. 297-303 ◽  
Author(s):  
C. T. Crowe
Keyword(s):  
Numerical Models ◽  
Model Development ◽  
Point Of View ◽  
One Dimensional ◽  
Advantages And Disadvantages ◽  
Dilute Gas ◽  
Particle Flows ◽  
Gaseous Flows ◽  
Droplet Flows ◽  
Two Fluid

The rapidly increasing capability of computers has led to the development of numerical models for gaseous flows and, in turn, gas-particle and gas-droplet flows. This paper reviews the essential features of gas-particle flows from the point of view of model development. Various models that have appeared for one-dimensional and two-dimensional flows are discussed. The advantages and disadvantages of the trajectory and two-fluid models are noted.

Improved Performance of a Radial Turbine Through the Implementation of Back Swept Blading

2008 ◽  
Author(s):  
Liam Barr ◽  
Stephen W. T. Spence ◽  
Paul Eynon
Keyword(s):  
Numerical Study ◽  
Numerical Models ◽  
Internal Flow ◽  
Turbine Rotor ◽  
Point Of View ◽  
Blade Angle ◽  
Element Analysis ◽  
Numerical Predictions ◽  
Radial Turbine ◽  
Optimum Velocity

This report details the numerical investigation of the performance characteristics and internal flow fields of an 86 mm radial turbine for a turbocharger application. A new blade was subsequently designed for the 86 mm rotor which departed from the conventional radial inlet blade angle to incorporate a 25° inlet blade angle. A comparative analysis between the two geometries is presented. Results show that the 25° back swept blade offers significant increases in efficiency while operating at lower than optimum velocity ratios (U/C). This enhanced efficiency at off-design conditions would significantly improve turbocharger performance where the turbine typically experiences lower than optimum velocity ratios while accelerating during engine transients. A commercial CFD code was used to construct single passage steady state numerical models. The numerical predictions show off-design performance gains of 2% can be achieved, while maintaining design point efficiency. Primary and secondary flow patterns are examined at various planes within the turbine blade passage and reasons for the increase in performance are discussed. A finite element analysis has been conducted to assess the stress implications of introducing a non-radial angle at turbine rotor inlet. A modal analysis was also carried out in order to identify the natural frequencies of the turbine geometry, thus calculating the critical speeds corresponding to the induction of the excitational frequencies from the stator vanes. Although the new blade design has resulted in stress increases in some regions, the numerical study has shown that it is feasible from both an aerodynamic and structural point of view to increase the performance characteristic of a radial turbine through the implementation of back swept blading.

Study on the collapse of tapered tubes subjected to oblique loads

2008 ◽  
Vol 222 (11) ◽  
pp. 2025-2039 ◽  
Author(s):  
P Hosseini-Tehrani ◽  
S Pirmohammad ◽  
M Golmohammadi
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Numerical Models ◽  
Point Of View ◽  
Finite Element Code ◽  
Energy Absorber ◽  
Explicit Finite Element ◽  
Bending Deformation ◽  
Oblique Loading

In this work, several antisymmetric tapered tubes with an inner stiffener under axial and oblique loading are studied and optimum dimensions of the tapered tube are derived from a crashworthiness point of view. The importance of detecting these dimensions is optimizing the weight while the crashworthiness of tube is not damaged. By using an internal stiffener, crashworthiness is improved against oblique loads, and the sensitivity of tubes with respect to oblique loads and bending deformation is diminished. The numerical models have been developed using the explicit finite element code LS-DYNA. The crashworthiness of the optimized tapered tube is compared with that of an octagonal-cross-section tube which is known as the best energy absorber model in the literature. It is shown that an optimized tapered tube has an average of 29.3 per cent less crushing displacement in comparison with octagonal-section tube when both tubes have the same weights and the same peaks of crushing load. Finally, the orientation of loading is changed and the best orientation is proposed.

A Numerical and Experimental Performance Comparison of an 86 MM Radial and Back Swept Turbine

2009 ◽  
Author(s):  
Liam Barr ◽  
Stephen Spence ◽  
David Thornhill ◽  
Paul Eynon
Keyword(s):  
Numerical Models ◽  
Performance Comparison ◽  
Point Of View ◽  
Blade Angle ◽  
Experimental Performance ◽  
Numerical Predictions ◽  
Radial Turbine ◽  
Optimum Velocity ◽  
Performance Results ◽  
Performance Gains

This report details the numerical and experimental investigation of the performance characteristics of a conventional radial turbine compared with a new back swept design for the same application. The blade geometry of an existing turbine from a turbocharger was used as a baseline. A new back swept blade was subsequently designed for the rotor, which departed from the conventional radial inlet blade angle to incorporate a 25° inlet blade angle. A comparative numerical analysis between the two geometries is presented. Results show that the 25° back swept blade offers significant increases in efficiency while operating at lower than optimum velocity ratios (U/C). Improvements in efficiency at off-design conditions could significantly improve turbocharger performance since the turbine typically experiences lower than optimum velocity ratios while accelerating during engine transients. A commercial CFD code was used to construct single passage steady state numerical models. The numerical predictions show off-design performance gains of 2% can be achieved, while maintaining design point efficiency. A finite element stress analysis was conducted to show that the nonradial inlet blade angle could be implemented without exceeding the acceptable stress levels for the rotor. A modal analysis was also carried out in order to identify the natural blade frequencies, showing that these were not significantly changed by the implementation of backswept blading. A prototype backswept rotor was produced and tested in a direct comparison with the baseline rotor geometry. Experimental performance results showed strong correlations with those obtained numerically, and verified the predicted performance gains at off-deign velocity ratios. This numerical and experimental study has shown that it is feasible from both an aerodynamic and structural point of view to improve the performance characteristic of a radial turbine at lower than optimum velocity ratios through the implementation of back swept blading.

scholarly journals Comparison of Modelling Strategies of R.C Walls for Seismic Analysis

2021 ◽  
Vol 1197 (1) ◽  
pp. 012067
Author(s):  
Syed Hamim Jeelani ◽  
Salim Akhtar ◽  
N Lingeshwaran ◽  
Durga Chaitanya Kumar Jagarapu ◽  
M A Mohammed Aslam ◽  
...  
Keyword(s):  
Seismic Analysis ◽  
Response Spectrum ◽  
Time History ◽  
Shell Element ◽  
Point Of View ◽  
Element Discretization ◽  
Shell Elements ◽  
Design Engineers ◽  
Equivalent Strut ◽  
Modelling Strategies

Abstract Reinforced concrete walls are being widely adopted as lateral load resisting systems for high rise structures. The current practice among design engineers for modelling of such walls is by idealizing the same as ‘wide’ columns, which is uncertain from safety as well as economy point of view. The most efficient modelling strategy of RC walls involves use of shell elements. Such an approach can be computationally much intensive, especially from a seismic analysis perspective. The present study utilizes an equivalent strut approach for modelling RC walls. The modelling strategy is demonstrated on a G + 15 storey residential apartment located in Calicut city. The proposed methodology will be compared with the traditional ‘wide’ column method as well as the one with shell element discretization. Comparison of modal properties such as frequencies and vibration modes from the various models are initially made to assess the model accuracy. Various seismic analyses viz. Equivalent static approach, Response spectrum approach and the assessment the storey shear, inter storey drifts as well as computation times using various models were performed using time history analysis. From preliminary results, it is understood that the modelling strategy could serve as an efficient alternative to more robust and computationally demanding scheme involving use of shell elements.

scholarly journals Numerical Evaluation of a 70-m Deep Hydro-Power Station Foundation Pit Dewatering

2021 ◽  
Author(s):  
Jianxiu Wang ◽  
Yansheng Deng ◽  
Xiaobo Wang ◽  
Xiaotian Liu ◽  
Nianqing Zhou
Keyword(s):  
Groundwater Level ◽  
Slope Failure ◽  
Numerical Models ◽  
Water Inrush ◽  
Cutoff Wall ◽  
Power Station ◽  
Foundation Pit ◽  
Hydro Power ◽  
Second Stage ◽  
Pumping Wells

Abstract The average depth of Yamansu hydropower station foundation pit is 70 m. The foundation pit was excavated with five-level slopes. The lowering of groundwater level is significant for excavation. Drainage and pumping were adopted in dewatering. Pumping tests were performed to reverse hydraulic parameters and calibrate numerical models. Numerical simulations were performed to evaluate the dewatering scheme. In the first stage, powerhouse tailrace canal was excavated and utilized as a drainage channel to lower the groundwater level. The drawdown and hydraulic gradient were evaluated to prevent potential water inrush, erosion, piping, and slope failure. In the second stage, cutoff wall and pumping wells were evaluated to lower the groundwater level. The influences of depth, permeability, and thickness of the cutoff wall were evaluated. Dewatering scheme was revised accordingly based on the evaluation. The optimized dewatering scheme, which can be referred by similar engineering, was performed and verified successfully.

scholarly journals Comparative Analyses between The Zero-Inertia and Fully Dynamic Models of the Shallow Waters Equations for Unsteady Overland Flow Propagation

2017 ◽  
Author(s):  
Costanza Aricò ◽  
Carmelo Nasello
Keyword(s):  
Overland Flow ◽  
Dynamic Models ◽  
Numerical Models ◽  
Nonlinear Partial Differential Equations ◽  
Computational Effort ◽  
Point Of View ◽  
Shallow Waters ◽  
Hyperbolic Model ◽  
Flow Routing ◽  
Inertial Terms

The shallow water equations are widely applied for the simulation of flow routing in rivers and floodplains, as well as for flood inundation mapping. From a mathematical point of view, they are a hyperbolic system of nonlinear partial differential equations, whose numerical integration is sometimes computationally burdensome. For this reason, the interest of many researchers has been focused on the study of simplified forms of the original set of equations, which requires less computational effort. One of the most commonly applied simplifications consists in neglecting the inertial terms, which changes the hyperbolic model to a parabolic one. The effects of such a choice on the outputs of the simulations of flooding events are controversial and an important topic of debate. In the present paper, two numerical models, recently proposed for the solution of the complete and zero-inertia forms of the shallow waters equations, are applied to several unsteady flow routing scenarios. We simulate synthetic and laboratory studies, starting from very simple geometries and moving towards complex topographies. Analyzing the role of the terms in the momentum equations, we try to understand the effect, on the computed results, of neglecting the inertial terms in the zero-inertia formulation. We analyze the computational costs.

Sign in / Sign up

Export Citation Format

Share Document