Abstract

Passive control of base pressure remains a critical technology for drag reduction in aerospace and automotive applications, offering simplicity and reliability without external energy input. While numerous techniques—including cavities, ribs, spikes, and boat-tailing— have been extensively studied, a synthesis that focuses on the unifying flow physics and the practical challenges of design integration is warranted. This review analyzes passive control methods through the lens of their interactions with key flow features: shear-layer dynamics, recirculation-zone structure, and vortex-shedding mechanisms. We categorize techniques based on their primary control mechanism: (1) Shear Layer Manipulation, (2) Recirculation Zone Modification, and (3) Wake Stabilization. Recent advances from 2020 to 2024 are incorporated to update the field’s state-of-the-art. The paper critically evaluates the efficacy of each method across different flow regimes (subsonic to supersonic) and applications (internal vs. external flows), highlighting performance trade-offs, optimal parameter ranges, and synergistic effects. We conclude by identifying persistent gaps in knowledge and proposing future research directions focused on hybrid passive systems, additive manufacturing for complex geometries, and application in next-generation highspeed vehicles.

Keywords

base drag, passive flow control, recirculation zone, shear layer, vortex dynamics, drag reduction, aerodynamic optimization