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For flow around elongated bluff bodies, flow separations would occur over both leading and trailing edges. Interactions between these two separations can be established through acoustic perturbation. In this paper, the flow and the acoustic fields of a D-shaped bluff body (length-to-height ratio L/H = 3.64) are investigated at height-based Reynolds number Re = 23,000 by experimental and numerical methods. The purpose of this paper is to study the acoustic feedback in the interaction of these two separated flows.

The flow field is measured by particle image velocimetry, hotwire velocimetry and surface oil flow visualization. The acoustic field is modeled in two dimensions by direct aeroacoustic simulation, which solves the compressible Navier–Stokes equations. The simulation is validated against the experimental results.

Separations occur at both the leading and the trailing edges. The leading-edge separation point and the reattaching flow oscillate in accordance with the trailing-edge vortex shedding. Significant pressure waves are generated at the trailing edge by the vortex shedding rather than the leading-edge vortices. Pressure-based cross-correlation analysis is conducted to clarify the effect of the pressure waves on the leading-edge flow structures.

The understanding of interactions of separated flows over elongated bluff bodies helps to predict aerodynamic drag, structural vibration and noise in engineering applications, such as the aerodynamics of buildings, bridges and road vehicles.

This paper clarifies the influence of acoustic perturbations in the interaction of separated flows over a D-shaped bluff body. The contribution of the leading- and the trailing-edge vortex in generating acoustic perturbations is investigated as well.

This paper aims to shed light on how children's literature in Africa deserves to be studied because African writers “decolonize” the minds of African children and children and adults around the world.

This paper defines children's literature from an African perspective and the “decolonization of the mind.” This is done to examine how two African writers provide narratives for children inspired by their cultures. They deal with themes, characters and symbols that interest children and adults.

Achebe and Youssef crossed many borders: the world of children and adults, animals and humans, vice and virtue, supernatural and real. Their stories take the reader on journeys that involve enriching, engaging and inspiring adventures.

Youssef and Achebe are prolific writers. Providing a survey of what is available in Arabic and Nigerian literature for children, is beyond the scope of this paper.

This paper sends a message to those in charge of the curriculum in schools in Egypt, the Arab countries, Africa and the world at large: decolonize the syllabi in schools because the world is not black and white. Literature for children that encourages critical thinking is available by African writers in Egypt, Nigeria and elsewhere.

The works discussed show that African writers are creative, and their works inspire the African child with pride in his/her identity, culture and heritage.

To the best of the author’s knowledge, no one has compared Egyptian and Nigerian literature for children before. Youssef and Achebe provide evidence that “Good literature gives the child a place in the world … and the world a place in the child.” – Astrid Lindgren.