Instability of Liquid Jets: Incorporating a forcing function

In summary, the conversation revolves around the instability theory in liquid jet breakup and the equations used to describe the growth rate of disturbances. The person is working with a droplet generation system that uses a periodic disturbance to break up the liquid jet into droplets. They mention articles by Savart, Plateau, Rayleigh, and Weber that have investigated this subject and developed equations for the disturbance growth rate. The person is unsure about the derivation of these equations and whether a forcing function should be incorporated. They also question whether using a series of identical disturbances, as opposed to one disturbance, would alter the predicted breakup and growth rate equations. They are seeking insight and help in finding the correct equations for their experiment.
  • #1
undergrad25
1
0
Hi, I am working with a droplet generation system that is designed to produce monodisperse droplets. A periodic disturbance of appropriate frequency (kHz) is applied to a piezoelectric ceramic, transferred to an orifice disk (fitted within the ceramic by means of a Teflon O-ring), then sent to the liquid jet. The disturbance then breaks up the jet into droplets.

My question is in trying to understand the instability theory in liquid jet breakup. There are a number of articles that have investigated this subject, among them Savart(1833), Plateau(1873), Rayleigh(1878), and Weber(1931). Equations about the disturbance growth rate have been developed by Rayleigh and Weber for inviscid and viscous flow, respectively.
I do not fully understand the derivation of these equations, but to my understanding, the disturbance they consider is one without a forcing function. I have also looked at other articles that used the disturbance growth rate equations to investigate their experiment involving a monodisperse droplet generator, but they do not mention anything about incorporating a forcing function in the derivation of the equations.

Can anyone give me some insight on this? Shouldn't a forcing function be used to describe the disturbance that is being sent from a function generator to the piezoelectric ceramic, causing the orifice disk to vibrate, and creating droplet breakup? To my understanding Weber sent one disturbance to the jet, whereas I am sending a series of identical disturbances by means of a function generator. Wouldn't this alter the breakup predicted by Weber and thus change the growth rate equation developed by Weber?
 
Engineering news on Phys.org
  • #2
I am having a hard time trying to come up with the correct equations to describe the droplet breakup in my experiment, so any help would be greatly appreciated.
 

1. What is the purpose of incorporating a forcing function in the study of liquid jet instability?

The purpose of incorporating a forcing function in the study of liquid jet instability is to simulate real-world conditions and better understand the behavior of liquid jets in practical applications. The forcing function can mimic external disturbances or variations in the jet's initial conditions, allowing for more accurate predictions and insights into the dynamics of the jet.

2. How does the inclusion of a forcing function affect the stability of liquid jets?

The inclusion of a forcing function can either stabilize or destabilize the liquid jet, depending on the type and magnitude of the forcing. In some cases, the forcing may cause the jet to break up into smaller droplets, while in others it may lead to the formation of more organized structures. The specific impact of the forcing function will depend on the parameters of the jet and the nature of the forcing.

3. What types of forcing functions are commonly used in the study of liquid jet instability?

There are several types of forcing functions that can be used in the study of liquid jet instability. These include external disturbances such as acoustic vibrations or air currents, as well as variations in the jet's initial conditions such as changes in the jet velocity or surface tension. Additionally, researchers may also incorporate a forcing function by varying the properties of the liquid itself, such as its viscosity or density.

4. How do researchers determine the appropriate forcing function to use in their experiments?

The choice of forcing function will depend on the specific research goals and the properties of the liquid jet being studied. Researchers may conduct preliminary experiments to identify the most relevant external disturbances or variations in initial conditions for a particular jet system. Alternatively, theoretical models or numerical simulations can also help guide the selection of an appropriate forcing function.

5. What are some potential applications of studying liquid jet instability with a forcing function?

Understanding and controlling the instability of liquid jets is crucial in many industrial processes, such as fuel injection in engines, inkjet printing, and spray coating. By incorporating a forcing function, researchers can gain insights into the mechanisms behind jet breakup and develop strategies to improve the performance and efficiency of these applications. Additionally, studying the behavior of liquid jets with a forcing function can also have implications for fundamental research in fluid dynamics and non-linear dynamics.

Similar threads

Is my fictional Solar System stable and realistic?
    • Sci-Fi Writing and World Building
Replies
21
Views
1K

Hot Threads

Recent Insights

Back
Top