Changes in Returns to Education in India, 1983-94: By Gender, Age-Cohort and Location

There is hardly any estimate of the returns to schooling in India based on a national level representative data for the recent period. This paper provides estimates of the returns to education in India by gender, age cohort and location (by rural-urban) for the most recent period 1993/4, and also evaluates the changes in returns over a period of time from 1983-94 using a large national level household survey data. The data show that the returns to education increases up to the secondary level and declines thereafter. There is evidence of substantial gender and rural-urban differences in the returns to schooling. The returns to women's education for the primary and middle levels have declined while those for secondary and college levels have increased during the decade 1983-94.Rate of return, human capital, India

Child Schooling and Child Work in India

In India, about 62 percent of the children in the age group of 5-14 are currently enrolled in schools, and 4 percent of children are reported to be working. The remaining 34 percent of children in this age group are neither enrolled in school nor reported as participating in work. The twin problems of child schooling and child work in India have not been adequately addressed in the literature. Another important dimension to this problem is the gender disparity in school enrollment. Available data indicate that the enrollment rate of girls is 12 percent below that of boys. This paper investigates the determinants of schooling and work participation of boys and girls using a large scale national level survey data, 1994, of the NCAER. The main contribution of this paper lies in integrating the child schooling and work participation decisions and bringing the third category of children referred to as the 'invisible' children into the rigorous econometric analysis. The widely used household demand model is applied in this study to analyze the family's decisions concerning the schooling and work participation of their children. These decisions are formulated in a dichotomous and a trichotomous choice framework and empirically estimated using maximum likelihood probit and multinomial logit methods. The likelihood ratio test suggests that the trichotomous model is the preferred formulation of the family's decisions on children's schooling and work participation. The empirical estimates based on both the models point to certain interesting findings. Parental education, and family income significantly increase the probability of children's school attendance and reduce the likelihood of children participating in work. Mother's education exerts a much stronger effect of increasing school enrollment and reducing child labor. Availability of middle schools within the village increases the school attendance and reduces child labor. The estimates of the gender specific differences in the determinants of schooling and work participation of children suggest that maternal education increases more the likelihood of a girl child's school enrollment than boys and also reduces more the work participation of girls over boys.

Evolution of isolated turbulent trailing vortices

In this work, the temporal evolution of a low swirl-number turbulent Batchelor vortex is studied using pseudospectral direct numerical simulations. The solution of the governing equations in the vorticity-velocity form allows for accurate application of boundary conditions. The physics of the evolution is investigated with an emphasis on the mechanisms that influence the transport of axial and angular momentum. Excitation of normal mode instabilities gives rise to coherent large scale helical structures inside the vortical core. The radial growth of these helical structures and the action of axial shear and differential rotation results in the creation of a polarized vortex layer. This vortex layer evolves into a series of hairpin-shaped structures that subsequently breakdown into elongated fine scale vortices. Ultimately, the radially outward propagation of these structures results in the relaxation of the flow towards a stable high-swirl configuration. Two conserved quantities, based on the deviation from the laminar solution, are derived and these prove to be useful in characterizing the polarized vortex layer and enhancing the understanding of the transport process. The generation and evolution of the Reynolds stresses is also addressed

Aerodynamic response of a hovering rotor to ramp change in pitch input

Under transient conditions, a helicopter rotor generates a complex, time-dependent pattern of shed and trailed vorticity in its wake that has profound effects on its loading. To examine these effects, the response of a two-bladed hovering rotor to a ramp change in collective pitch is investigated using three different computational approaches. Solutions obtained using a Compressible Reynolds Averaged Navier-Stokes approach are compared to results obtained from lifting-line theory coupled to an Eulerian Vorticity Transport Model, and from a simple single-state dynamic inflow model. The different numerical approaches yield very similar predictions of the thrust response of the rotor to ramp changes in collective pitch, as long as the ramp rates are small. This suggests that the basic underlying flow physics is properly represented by all the approaches. For more rapid ramp rates, an additional delay in the aerodynamic response of the rotor, that is related to the finite extent of the wake during its early history, is predicted by the Navier-Stokes and Vorticity Transport approaches. Even though the evolution of the wake of the rotor is strongly three dimensional and highly unsteady, the predictions of the Navier-Stokes and lifting-line models agree very closely as long as the blades of the rotor do not stall. In the pre-stall regime, a quasi two-dimensional representation of the blade aerodynamics thus appears adequate for predicting the performance of such systems even under highly transient conditions. When flow separation occurs, the resulting three dimensionality of the blade aerodynamics forces the predictions of the Navier-Stokes and lifting-line approaches to diverge, however. The characterization of the wake interactions and stall propagation mechanisms that are presented in this study offers some insight into the fundamental fluid dynamic mechanisms that govern the transient aerodynamic response of a rotor to control inputs, and provides some quantication of the limits of applicability of some popular current approaches to rotor aerodynamic analysis

Aerodynamic Response of a Hovering Rotor to Ramp Changes in Pitch Input

Under transient conditions, a helicopter rotor generates a complex, time-dependent pattern of shed and trailed vorticity in its wake that has profound eects on its loading. To examine these eects, the response of a two-bladed hovering rotor to a ramp change in collective pitch is investigated using three dierent computational approaches. Solutions obtained using a Compressible Reynolds Averaged Navier{Stokes ap- proach are compared to results obtained from lifting-line theory coupled to an Eulerian Vorticity Transport Model, and from a simple single-state dynamic in ow model. The dierent numerical approaches yield very similar predictions of the thrust response of the rotor to ramp changes in collective pitch, as long as the ramp rates are small. This suggests that the basic underlying ow physics is properly represented by all the approaches. For more rapid ramp rates, an additional delay in the aerodynamic response of the rotor, that is related to the nite extent of the wake during its early history, is predicted by the Navier{Stokes and Vorticity Transport approaches. Even though the evolution of the wake of the rotor is strongly three dimensional and highly unsteady, the predictions of the Navier{Stokes and lifting-line models agree very closely as long as the blades of the rotor do not stall. In the pre-stall regime, a quasi two-dimensional representation of the blade aerodynamics thus appears adequate for predicting the performance of such systems even under highly transient conditions. When ow separation occurs, the resulting three dimen- sionality of the blade aerodynamics forces the predictions of the Navier{Stokes and lifting-line approaches to diverge, however. The characterization of the wake interactions and stall propagation mechanisms that are presented in this study oers some insight into the fundamental uid dynamic mechanisms that govern the transient aerodynamic response of a rotor to control inputs, and provides some quantication of the limits of applicability of some popular current approaches to rotor aerodynamic analysis

High resolution computation of the aerodynamics and acoustics of blade vortex interaction

In the present work, high resolution CFD simulations have been performed on an idealised problem of the interaction of an independently generated vortex with a rotor blade, including a case where the vortex directly impacts on the blade. The resulting blade pressures and acoustics are comprehensively compared against experimental measurements. Two different modelling approaches are used: the first is to impose the vortex as a perturbation to the velocity field, and the second is to fully resolve the vortex formation, evolution and its interaction with the blade. For a case in which the vortex passes near the blade surface, the the fully resolved approach is confirmed to accurately preserve the vortex structure. The far field acoustic predictions offered by the fully resolved approach are seen to be very accurate and definite improvements are observed in the computed blade pressures and acoustics over the imposed vortex approach and other similar works in the literature. For a case in which the vortex axis passes through the blade, the shape and width of the acoustic pulse in the far field is accurately represented by the fully resolved approach, while the magnitude is slightly underpredicted. The improvement in prediction offered by the fully resolved approach is because this method allows for a more realistic representation of phenomena, such as dynamic change in vortex structure and trajectory due to the blade passage, that become important when the vortex miss-distance becomes small