Sound waves influencing particle streams.

Jet Stream Secrets: How Sound and Particles Shape Airflow

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Soraya Malik in Science & Nature August 2025 • 4 min read.

"Unlocking the science behind acoustic manipulation of two-phase jets: A guide for optimizing industrial processes and understanding fluid dynamics."


Two-phase flows, where gases and particles interact, are crucial in many applications like medical sprays, industrial processes, and even combustion engines. Understanding how these flows behave is essential for optimizing performance and efficiency. The dynamics between the dispersed phase (particles) and the continuous phase (gas or liquid) involve complex exchanges of mass, energy, and momentum.

One way to influence these flows is through acoustic forcing – essentially using sound waves to control turbulence and vortex shedding. Acoustic forcing offers a way to fine-tune the mixing of fluids and particles, enhance the ingestion of surrounding materials, and manage particle dispersion. This method provides a simplified, controllable environment for studying fluid-particle interactions.

New research explores an acoustically forced two-phase air jet, examining how different factors affect its structure. By comparing an unforced jet, a single-phase forced jet, and a two-phase forced jet, scientists have uncovered valuable insights into the effects of both acoustic forcing and particle load on the flow, paving the way for advancements in various technological fields.

Decoding the Experiment: Setup and Methodology

Sound waves influencing particle streams.

The experiment focuses on an air jet laden with tiny, transparent glass spheres, forced downwards through a pipe with a special nozzle at the end. This nozzle is designed to ensure a consistent, uniform exit velocity profile. The key here is precise control: the experimental setup is managed by a computer to maintain accuracy and long-term stability.

Measurements are taken using a two-color Phase-Doppler Anemometer (PDPA), an advanced instrument that captures the size, radial velocity, and axial velocity of particles as they pass through a measurement point. A trigger signal, synchronized with the sound waves, allows researchers to measure the arrival phase of each particle, providing a comprehensive picture of particle behavior throughout the forcing cycle.

  • Particle specifics: The experiment uses transparent glass spheres ranging from 2 to 50 micrometers in diameter, resulting in a Stokes number of approximately 1.
  • Acoustic parameters: A forcing frequency of 400 Hz is selected, which induces a powerful, periodic flow pattern.
  • Airflow control: The jet's exit velocity is carefully set to 15 meters per second, resulting in a Reynolds number of 11900.
Raw data is carefully processed to minimize bias caused by the forcing and the instrument itself, ensuring accurate mean values for the dispersed flow. This meticulous approach allows researchers to clearly distinguish the effects of acoustic forcing and particle load on the jet's behavior.

Key Findings and Future Applications

The study reveals how acoustic forcing and particle load dramatically influence the structure of a two-phase jet. The acoustic waves create organized, repeating patterns in the flow, while the presence of particles can either enhance or weaken these structures, depending on their size and concentration.

One significant observation is the formation of particle clusters due to the acoustic forcing, which could have implications for controlling material distribution in industrial processes. The researchers also found that acoustic forcing significantly enhances particle dispersion, widening the area over which particles spread.

This research opens doors for optimizing various applications, from improving the efficiency of fuel combustion to designing more effective drug delivery systems. By understanding and controlling the dynamics of two-phase flows, engineers and scientists can develop more advanced and efficient technologies.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1051/epjconf/20146702013, Alternate LINK

Title: An Accurate Quantification Of The Flow Structure Along The Acoustic Signal Cycle In A Forced Two-Phase Jet

Subject: General Medicine

Journal: EPJ Web of Conferences

Publisher: EDP Sciences

Authors: Esteban Calvo Bernad, Juan Antonio García Rodríguez, José Luis Santolaya Sáenz, Luis Adrián Aísa Miguel, J. Ignacio García Palacín

Published: 2014-01-01

Everything You Need To Know

1

What are two-phase flows, and why are they important?

Two-phase flows are crucial in many applications, such as medical sprays, industrial processes, and combustion engines, because they involve the interaction of gases and particles. Understanding the dynamics between the dispersed phase (particles) and the continuous phase (gas or liquid) is essential for optimizing performance and efficiency. This includes the complex exchanges of mass, energy, and momentum within these systems.

2

How does acoustic forcing work in this context?

Acoustic forcing utilizes sound waves to control turbulence and vortex shedding within a two-phase jet. By applying sound waves, researchers can fine-tune the mixing of fluids and particles, enhance the ingestion of surrounding materials, and manage particle dispersion. This method provides a simplified, controllable environment for studying fluid-particle interactions, allowing for precise adjustments and observations of flow behavior.

3

What is the experimental setup?

The experiment employs an air jet laden with transparent glass spheres, ranging from 2 to 50 micrometers in diameter, with an exit velocity of 15 meters per second and a Reynolds number of 11900. A two-color Phase-Doppler Anemometer (PDPA) is used to measure particle size, radial velocity, and axial velocity, synchronized with a forcing frequency of 400 Hz. This setup allows for precise control and measurement of the jet's behavior under acoustic forcing.

4

What is the significance of the Stokes number?

The Stokes number, approximately 1, represents the ratio of inertial forces to viscous forces experienced by the particles. A Stokes number of 1 suggests a balance between inertia and viscosity, indicating that the particles' movement is significantly influenced by both the flow's momentum and the viscous forces acting on them. This balance is critical in understanding how particles respond to acoustic forcing and how they interact with the surrounding gas.

5

What are the key findings and implications of the study?

Acoustic forcing and particle load significantly influence the structure of a two-phase jet. Acoustic waves create organized, repeating patterns in the flow. The presence of particles can either enhance or weaken these structures, depending on their size and concentration. These findings have implications for various technological fields, including pharmaceuticals and combustion technology, where precise control over fluid and particle mixing is crucial.

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