2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/203986We develop a technique to study relativistic perturbations in the generalised brane cosmological scenario, which is a generalisation of the multi-fluid cosmological perturbations to brane cosmology. The novelty of the technique lies in the inclusion of a radiative bulk which is responsible for bulk-brane energy exchange, and in turn, modifies the standard perturbative analysis to a great extent. The analysis involves a geometric fluid -- called the Weyl fluid -- whose nature and role have been studied extensively both for the empty bulk and the radiative bulk scenario. Subsequently, we find that this Weyl fluid can be a possible geometric candidate for dark matter in this generalised brane cosmological framework.18 pages, 1 figure, accepted for publication in Phys.Rev.DGeneral Relativity and Quantum CosmologyAstrophysicsHigh Energy Physics - Theorytext