Open Access

ARTICLE

Influence of Cavity Position on Flow Control at Large Mach Numbers: A CFD Analysis

Sher Afghan Khan¹, Ridwan¹, Abdul Aabid^2,*, Khizar Ahmed Pathan³, Muneer Baig²

1 Affiliation Mechanical and Aerospace Engineering Department, Faculty of Engineering, International Islamic University, Kuala Lumpur, Malaysia
2 Department of Engineering Management, College of Engineering, Prince Sultan University, Riyadh, Saudi Arabia
3 Department of Mechanical Engineering, CSMSS Chh. Shahu College of Engineering, Aurangabad, Maharashtra, India

* Corresponding Author: Abdul Aabid. Email:

(This article belongs to the Special Issue: Analysis of High-Speed Flows using Advanced Computational Methods)

Fluid Dynamics & Materials Processing 2026, 22(8), 2 https://doi.org/10.32604/fdmp.2026.084998

Received 03 May 2026; Accepted 28 August 2026; Issue published 04 September 2026

Abstract

This study investigates the influence of a passive cavity flow-control strategy on base pressure in suddenly expanded supersonic flows through computational fluid dynamics (CFD) simulations. The flow configuration consists of a convergent-divergent (CD) nozzle discharging into an enlarged duct with an area ratio of 2.89. Simulations were performed for Mach numbers of 1.2, 1.4, 1.6, and 1.8, while the cavity was positioned upstream of the expansion at cavity locations corresponding to length-to-diameter ratios (L/D) ranging from 0.5 to 2.0 in increments of 0.5. The effects of nozzle pressure ratio (NPR), Mach number, duct length-to-diameter ratio, and cavity placement on base pressure were systematically examined. The results demonstrate that the cavity significantly enhances base pressure under the investigated operating conditions without adversely affecting the flow field. Base pressure is strongly influenced by Mach number, NPR, duct geometry, and cavity location. Among the configurations considered, the cavity positioned at 0.5D from the nozzle exit consistently provides the most effective pressure recovery across the range of Mach numbers, NPRs, and L/D ratios investigated. Furthermore, increasing NPR promotes stronger under-expanded jet conditions, with highly under-expanded flows observed at NPR = 6 and 8, leading to a corresponding increase in base pressure. These findings highlight the potential of cavity-based passive control for regulating base pressure in suddenly expanded supersonic flows.

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Keywords

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