# Aeroacoustics and psychoacoustics characterization of a boundary layer ingesting ducted fan

## TL;DR

This study explores how a ducted fan interacts with turbulent airflow to generate and transmit noise, and how this affects human perception.

## Contribution

The paper introduces a novel integrated aeroacoustic and psychoacoustic analysis of boundary layer ingesting ducted fans under varying thrust regimes.

## Key findings

- High-thrust operation increases boundary layer turbulence ingestion, leading to pronounced fan haystacking and noise amplification.
- Low-thrust operation results in duct-dominated noise with reduced suction effects and less boundary layer alteration.
- Both fan and duct haystacking contribute to higher perceived noise in high- and low-thrust regimes, respectively.

## Abstract

A comprehensive wind tunnel investigation was conducted to analyze noise generation, propagation, and perception mechanisms in a boundary layer ingesting (BLI) ducted fan through integrated aeroacoustic and psychoacoustic assessments. The study examines interactions between an incoming adverse pressure gradient turbulent boundary layer flow, developed over a curved wall, and the ducted fan. The fundamental investigation confirms that the fan thrust regime influences aerodynamic, aeroacoustic, and psychoacoustic characteristics, exhibiting various haystacking phenomena. High-thrust operation induces a pronounced upstream suction effect, accelerating the boundary layer flow, amplifying bulk momentum, and intensifying turbulence ingestion, leading to fan aeroacoustics and associated fan haystacking in noise spectrum. In contrast, low-thrust operation minimally alters the boundary layer flow, with reduced suction and noise dominated by duct aeroacoustics and the associated duct haystacking due to interactions between ingested turbulence and the duct’s acoustic field. The psychoacoustic assessments indicate that both fan and duct haystacking contribute to higher perceived noise in the high- and low-thrust regime, respectively.