Bubbly Water Shielding for Jet Noise Reduction
Abstract
The purpose of this action is to provide FY25 CR2 funds in the amount of $20K.---Approved for Public Release: A sheet of water-air mixture is used successfully in undersea work to attenuate the speed and intensity of underwater noises. We propose here to explore the use of such water-air mixture or just a water shield to reduce jet noise. We will consider three possible physical scenarios: A) A water-air mixture, B) A water curtain with air bubbles, and C) A water-only shield (wall of water). The proposed work is composed of two approaches. In The first approach in part I, we conduct direct LES of the jet and the water shield to find out the effect of the shield in noise reduction. This can address the three physical scenarios aforementioned: A, B, and C. In the second approach, Part II, we assume that the jet flow is given, and we focus on calculating the perturbation equations of acoustic waves passing through the air-water mixture on the sides of the jet flow. To demonstrate the benefit of solving the perturbation equations we consider here the case of suspended water droplets with zero incoming flow and assume that the Volume of Fraction (VOF) is <<1. The analytical solution shows how noise reduction is dependent on the volume of a fraction of the water, the diameter of the droplets, the sound frequency, and the thickness of the sheet. With confidence established, we will be solving the full perturbation equations for an incoming flow, with no restriction on the VOF, and conduct parametric studies that will be verified against LES and experimental observations. We will evaluate the effectiveness of each of the proposed configurations (A, B &C) and make recommendations. The sheet of water/air mixture, or the full water, can thus help protect personnel on aircraft carriers from jet noise. The proposed system can take advantage of several noise reduction mechanisms without affecting the engine thrust.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 12, 2025
- Source ID
- N000142512199
Entities
People
- Reda R. Mankbadi
Organizations
- Embry–Riddle Aeronautical University
- Office of Naval Research
- United States Navy