Flutter parametric studies of cantilevered twin-engine transport type wing with and without winglet. Volume 2: Transonic and density effect investigations

Flutter characteristics of a cantilevered high aspect ratio wing with winglet were investigated. The configuration represented a current technology, twin engine airplane. Compressibility effects through transonic Mach numbers and a wide range of mass-density ratios were evaluated on a low speed and high speed model. Four flutter mechanisms were obtained from test, and analysis from various combinations of configuration parameters. It is shown that the coupling between wing tip vertical and chordwise motions have significant effect under some conditions. It is concluded that for the flutter model configurations studied, the winglet related flutter is amenable to the conventional flutter analysis techniques. The low speed model flutter and the high-speed model flutter results are described

Effects of winglet on transonic flutter characteristics of a cantilevered twin-engine-transport wing model

A transonic model and a low-speed model were flutter tested in the Langley Transonic Dynamics Tunnel at Mach numbers up to 0.90. Transonic flutter boundaries were measured for 10 different model configurations, which included variations in wing fuel, nacelle pylon stiffness, and wingtip configuration. The winglet effects were evaluated by testing the transonic model, having a specific wing fuel and nacelle pylon stiffness, with each of three wingtips, a nonimal tip, a winglet, and a nominal tip ballasted to simulate the winglet mass. The addition of the winglet substantially reduced the flutter speed of the wing at transonic Mach numbers. The winglet effect was configuration-dependent and was primarily due to winglet aerodynamics rather than mass. Flutter analyses using modified strip-theory aerodynamics (experimentally weighted) correlated reasonably well with test results. The four transonic flutter mechanisms predicted by analysis were obtained experimentally. The analysis satisfactorily predicted the mass-density-ratio effects on subsonic flutter obtained using the low-speed model. Additional analyses were made to determine the flutter sensitivity to several parameters at transonic speeds

Machine Foundations in Power Plant and Other Industries- Case Studies

Studies on dynamic behaviour of turbo-generator foundations of various ratings have been carried out. Salient response parameters have been identified, Field vibration measurements taken on a 200 MW T.G. foundation have been reported. Measurements taken under intermittent coast-up and constant speed conditions have been analysed using FFT analyser and the frequency response thus obtained has been presented and discussed. From the signature analysis, high vibration peaks associated with the soil vibration modes have been observed. Analytical study carried out for 200 MW TG foundation also indicated the significance of soil structure interaction effect on the dynamic response. Based on the results of the analytical and experimental studies, recommendations have been made to include the soil structure interaction effect for dynamic response calculations

Soil Structure Interaction Effects on the Response of 210 MW T.G. Frame Foundations

The Design Office practice for the analysis and design of frame foundation generally ignores the soil structure interaction effects on the response of the frame foundation. A 210 MW T.G. frame foundation is analyzed using various standard approaches as well as using 3-0 finite element analysis. The analysis is carried out for fixed base as well as for elastic base conditions. Linear and rotational soil springs are considered to include the effect of base elasticity. The results of the analysis are presented. The analysis reveals that the soil structure interaction effects are significant both on the dynamic response parameters as well as on the strength parameters

A computer program for automated flutter solution and matched point determination

The use of a digital computer program (MATCH) for automated determination of the flutter velocity and the matched-point flutter density is described. The program is based on the use of the modified Laguerre iteration formula to converge to a flutter crossing or a matched-point density. A general description of the computer program is included and the purpose of all subroutines used is stated. The input required by the program and various input options are detailed, and the output description is presented. The program can solve flutter equations formulated with up to 12 vibration modes and obtain flutter solutions for up to 10 air densities. The program usage is illustrated by a sample run, and the FORTRAN program listing is included

Seismic Qualification of Mechanical Systems

Seismic qualification of large and complex mechanical systems is a tedious task in itself. It not only involves high computational cost, but also becomes cost ineffective in case repeated runs are required from safety considerations. Seismic analysis of one bank of Main PHT System of a typical Nuclear Power Plant has been attempted. Besides analysing the complete system, an attempt has also been made to divide the complete system into logical subsystems and analyse the same for the prescribed seismic loads. The results thus obtained have been compared with those of the complete system and a fairly good degree of agreement has been achieved. The subsystem approach has resulted in substantial reduction of the computational cost

No Tension Approach to Define Failure Phenomena for Rockfill Dam Subjected to Earthquake Loading

It has been observed that actual behavior of Rockfill dams during earthquake is much different than that obtained by elastic analysis. No tension approach has thus been developed to overcome the shortfalls of elastic analysis. Using no tension approach redistribution of stresses are obtained which help in defining the failure pattern of the dam\u27 subjected to a given seismic acceleration or in other words the failure acceleration is obtained for a given dam subjected to earthquake forces. Various dam models having different upstream and downstream slopes are analyzed using finite element technique. The input earthquake motion has been considered as an equivalent static force. Anisotropy of the rockfill material has been considered. The failure acceleration level for various dam models having different upstream and downstream slopes are thus evaluated. The results are compared with those obtained experimentally and show a good agreement