Effects of magnetic field orientation and buoyancy on heat transfer and entropy generation in a circular–trapezoidal magneto-nanofluidic systemMohamed Bechir Ben Hamida, Anjan Bhunia, Dipak Kumar Mandal, Nirmal K. Manna, Nirmalendu Biswas and Nashmi AlrasheediEur. Phys. J. Spec. Top., 234 23 (2026) 7025-7050DOI: https://doi.org/10.1140/epjs/s11734-025-01877-5