larsa said:Why the interface between the jet and the surrounding air needs to be at the same velocity?
Thank you for your answerMarkJW said:Fluids are treated as continuum mechanics. The jet has to displace air in its path, right? So it is going to transfer some energy/momentum.
Jets entrain mass because of a phenomenon called entrainment. This occurs when a high-speed fluid, such as air in the case of jets, drags surrounding fluid along with it. When a jet moves through the air, it creates a low-pressure zone behind it. This low-pressure zone draws in air from the surrounding environment, causing the jet to entrain mass.
Several factors can affect the entrainment of mass in jets. These include the speed and size of the jet, the density and viscosity of the fluid it is moving through, as well as environmental factors such as temperature and pressure. The shape and design of the jet can also play a role in entrainment.
The entrainment of mass can have both positive and negative impacts on the performance of jets. On one hand, it can increase the thrust and lift generated by the jet, allowing it to fly faster and more efficiently. However, entrainment can also create drag and turbulence, which can decrease the jet's overall performance.
The entrainment of mass in jets is a variable phenomenon. It can vary depending on the speed and altitude of the jet, as well as the surrounding environmental conditions. Additionally, factors such as turbulence, air density, and the design of the jet can also affect the amount of mass entrained.
Yes, the entrainment of mass in jets can be controlled and manipulated through various means. For example, the shape and design of the jet can be optimized to reduce drag and increase efficiency. Additionally, technologies such as boundary layer control can be used to manipulate the airflow around the jet and reduce entrainment of mass.