Self-similarity of confined flow past a bluff body

Evidence has been gathered from studying the experimental data available in the literature to reveal invariance of the confined flow past an inclined flat plate and a circular cylinder at sub-critical Reynolds numbers. A theoretical wake width is proposed such that the Strouhal number based on it and the velocity at flow separation is independent of blockage effect. By incorporating the proposed wake width and the momentum equation for confined flow into a free-streamline model for unconfined flow, the pressure at separation and the form drag are found as functions of blockage ratio. The predictions are in reasonable agreement with experimental data and comparable with other theoretical methods. The present study also provides a means of deriving the linear relationship between the drag and the base pressure observed empirically. Such a relationship has found applications in various bluff-body flows.