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Fluid flows in pipes whose cross-sectional area are increasing in the stream-wise direction are prone to separation of the recirculation region. This paper aims to investigate such fluid flow in expansion pipe systems using direct numerical simulations. The flow in circular diverging pipes with different diverging half angles, namely, 45, 26, 14, 7.2 and 4.7 degrees, are considered. The flow is fed by a fully developed laminar parabolic velocity profile at its inlet and is connected to a long straight circular pipe at its downstream to characterise recirculation zone and skin friction coefficient in the laminar regime. The flow is considered linearly stable for Reynolds numbers sufficiently below natural transition. A perturbation is added to the inlet fully developed laminar velocity profile to test the flow response to finite amplitude disturbances and to characterise sub-critical transition.

Direct numerical simulations of the Navier–Stokes equations have been solved using a spectral element method.

It is found that the onset of disordered motion and the dynamics of the localised turbulence patch are controlled by the Reynolds number, the perturbation amplitude and the half angle of the pipe.

The authors clarify different stages of flow behaviour under the finite amplitude perturbations and shed more light to flow physics such as existence of Kelvin–Helmholtz instabilities as well as mechanism of turbulent puff shedding in diverging pipe flows.

This article aims to analyze the workers' probabilities of following their parents’ occupational legacy and whether these individuals are paid differently compared to those who opted for occupations different from their parents, in Brazil.

To that end, the occupational legacy probability equation was estimated as the quantile wage equations with sample selection bias correction and the wage decomposition for Brazil from the microdata of the National Household Sample Survey (PNAD) of 2014. It was found that families have a strong influence on the process of choosing the careers of their children. The average probability of a young person following the occupational legacy of their parents was 41.63%. This percentage is different when analyzing different groups of individuals, such as being male or female, being in a traditional or single parent family, being in an income household lower or higher per capita.

The results also confirm the hypothesis that workers who tend to follow the occupational legacy have lower wages than individuals who choose other occupations and that this may cause a “poverty trap” since the lower the salary quantile, the stronger the “trap” as economically disadvantaged young people tend to follow in their parents' footsteps and to contribute to family income they face a tradeoff, opt between work or study, which ends up disrupting their education and forcing young people to entering the job market early, performing secondary occupations with lower income and arduous work, generating a “vicious cycle of poverty”.

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This is the first work on Latin American problem of occupational legacy.

This is the first work on Latin American problem of occupational legacy.