Development of aeroelastic analysis methods for turborotors and propfans, including mistuning

The NASA Lewis aeroelastic research program is focused on unstalled and stalled flutter, forced response, and whirl flutter of turborotors and propfans. The objectives are to understand the physical phenomena of cascade flutter and response including blade mistuning

Vibration, performance, flutter and forced response characteristics of a large-scale propfan and its aeroelastic model

An investigation of the vibration, performance, flutter, and forced response of the large-scale propfan, SR7L, and its aeroelastic model, SR7A, has been performed by applying available structural and aeroelastic analytical codes and then correlating measured and calculated results. Finite element models of the blades were used to obtain modal frequencies, displacements, stresses and strains. These values were then used in conjunction with a 3-D, unsteady, lifting surface aerodynamic theory for the subsequent aeroelastic analyses of the blades. The agreement between measured and calculated frequencies and mode shapes for both models is very good. Calculated power coefficients correlate well with those measured for low advance ratios. Flutter results show that both propfans are stable at their respective design points. There is also good agreement between calculated and measured blade vibratory strains due to excitation resulting from yawed flow for the SR7A propfan. The similarity of structural and aeroelastic results show that the SR7A propfan simulates the SR7L characteristics

Estimates of the level and growth effects of human capital in India

In the extended Solow growth model of Mankiw, Romer and Weil (1992) human capital has only permanent level and no growth effects. In the endogenous growth models human capital is a growth improving variable. Human capital may have both a permanent level and a permanent growth effect. We show, with data from India, that both the level and growth effects of human capital can be estimated with an extension to the Solow model.Solow model, Level and growth effects of human capital and India

Globalization and growth in the low Income African countries with the extreme bounds analysis

The relationship between globalization and economic growth, especially in the poorer developing countries, is controversial. Many previous studies have used single globalization indicators such as the ratio of exports plus imports to GDP. This paper uses a comprehensive measure of a globalization of Dreher (2006), which is based on measures of globalization of the economic, social and political sectors. Panel data estimates with data of 21 low income African countries show a small but significant positive permanent growth effects. The sensitivity of this growth effect is examined with the extreme bounds analysis (EBA). Contrary to the findings by Levine and Renelt (1992) that cross country growth relationships are fragile, the effects of globalization and some other determinants of the long run growth rate are found to be robust by EBA.Globalization, Economic growth, Solow model, Africa and Extreme bounds analysis.

The Determinants of Private Fixed Investment and the Relationship between Public and Private Capital Accumulation in Turkey

The purpose of this study is to analyse the determinants of private fixed investment spending in Turkey over the period 1970–96, which covers years of both financial repression and financial liberalisation. A reformulated neoclassical investment model and a reformulated flexible accelerator investment model have been tested for the Turkish economy. The results obtained support the accelerator principle and the crowding out hypothesis, that is, public and private sector investments have been found to be substitutes. Furthermore, the hypothesis that the volume of funds is as important as the cost of funds used in financing private fixed investment has been verified. On the other hand, the so-called McKinnon-Shaw hypothesis has not been completely verified because the effect of the medium-term real lending rate on private fixed investment has been found to be negative but statistically insignificant. Finally, the financial and liberalisation programmes that have been implemented since 1983 have not yet shown any noticeable positive effects on private investment.

Vibration and flutter characteristics of the SR7L large-scale propfan

An investigation of the vibration characteristics and aeroelastic stability of the SR7L Large-Scale Advanced Propfan was performed using a finite element blade model and an improved aeroelasticity code. Analyses were conducted for different blade pitch angles, blade support conditions, number of blades, rotational speeds, and freestream Mach numbers. A finite element model of the blade was used to determine the blade's vibration behavior and sensitivity to support stiffness. The calculated frequencies and mode shape obtained with this model agreed well with the published experimental data. A computer code recently developed at NASA Lewis Research Center and based on three-dimensional, unsteady, lifting surface aerodynamic theory was used for the aeroelastic analysis to examine the blade's stability at a cruise condition of Mach 0.8 at 1700 rpm. The results showed that the blade is stable for that operating point. However, a flutter condition was predicted if the cruise Mach number was increased to 0.9

Growth Effects of Globalization in the Low Income African Countries: A Systems GMM Panel Data Approach

The relationship between globalization and economic growth in the developing countries remains controversial. Liberals argue that globalization will lead to higher economic growth and prosperity. Skeptics contend the opposite, where globalization processes might lead to increased inequality and lower economic growth. Previous studies have examined this issue with single indicators such as trade openness or foreign direct investment (FDI) or aid etc. In this study we make use of a comprehensive measure of globalization developed by Dreher (2006), which measures globalization along three important dimensions viz., economic, political, and social fields to assess the pros and cons of globalization. Our panel data results with a systems based GMM (SGMM) method show a small but significant positive association between globalization and economic growth for a panel of 21 low income African countries for the period 1970 – 2005.: Globalization, Economic growth, Solow model, Africa

Semi-empirical model for prediction of unsteady forces on an airfoil with application to flutter

A semi-empirical model is described for predicting unsteady aerodynamic forces on arbitrary airfoils under mildly stalled and unstalled conditions. Aerodynamic forces are modeled using second order ordinary differential equations for lift and moment with airfoil motion as the input. This model is simultaneously integrated with structural dynamics equations to determine flutter characteristics for a two degrees-of-freedom system. Results for a number of cases are presented to demonstrate the suitability of this model to predict flutter. Comparison is made to the flutter characteristics determined by a Navier-Stokes solver and also the classical incompressible potential flow theory

Limnology and status of the fishery of Nelligudda Reservoir (Bangalore: India)

Nelligudda Reservoir (area: 80 ha, mean depth: 3.0 m) is a warm dimictic lake with stable thermal stratification for two extended periods (September-October and February-May) and with an intermittent period characterised by irregular circulation. Continuous mixing occurs during June-August. The water is well buffered, hard (mean alkalinity : 142.7 mg/1), moderately rich in electrolytes (mean conductivity : 373.4 uS/cm) and low in transparency (mean secchi depth : 51.3 cm). Clinograde distribution of oxygen, high sestonic carbon (mean : 5.0mg/l) and chlorophyll 'a' values (mean : 98.5 (ig/1) and high primary production rates (2.4 mg C/m2/d) suggest that the reservoir is productive . Despite low dissolved nutrient concentration (soluble reactive phosphorus <10 ug/1), high algal biomass implies internal cycling of nutrients. The reservoir harbours around 20 autochthonous fish species of which the exotic Oreochromis mossambicus contributes more than 80% to the commercial fishery. Growth overfishing has resulted in the decline of mean landing size of O. mossambicus to around 10cm. The importance of maintaining a minimum landing size of 20cm is discussed. The catch per unit effort showed two peaks with a major one in July and a minor one in March