Nozzle loss coefficient that increases with Reynolds number?

In summary, the conversation discusses the drag coefficient of a sphere at high Reynolds number and the potential for an "increasing loss coefficient" in an inlet flow nozzle at a Reynolds number of around 1e5. The person suggests that this may occur after the nozzle throat and references the concept of a "cavitating venturi." They also mention a search term for further information and provide a graph showing results for square edge orifices.
  • #1
bemortu
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0
TL;DR Summary
Is it possible to design an inlet nozzle (subsonic, turbulent) with a loss coefficient that increases with Reynolds number?
Hi,
I started to think about the drag coefficient of a sphere. At high Reynolds number Cd drops of suddenly when the boundary layer separates. If the Reynolds number is increased further, Cd increases with increasing Re. (I'm thinking about what is referred to as "post critical separated flow").

Does anybody know if something similar can be achieved for internal flows? Specifically in an inlet flow nozzle. I would like to have an increasing loss coefficient of the nozzle when Reynolds number increases. I'm dealing with incompressible flow (i.e. subsonic). Reynolds number around 1e5 (order of magnitude).
 
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  • #2
I would think that, if something like this happened, it would occur after the throat of the nozzle, rather than before.
 
  • #3
cavitating venturi?
 
  • #4
Search term orifice coefficient vs reynolds number found many good hits. Here's a graph from one of them for square edge orifices:
Orifice.jpg

You are up against the fluid dynamics of inlet flows. Smooth rounded inlets have much different curves.
 

FAQ: Nozzle loss coefficient that increases with Reynolds number?

What is a nozzle loss coefficient?

A nozzle loss coefficient is a dimensionless parameter that represents the energy loss in a fluid flow through a nozzle. It takes into account factors such as friction, turbulence, and expansion.

How does the nozzle loss coefficient vary with Reynolds number?

The nozzle loss coefficient typically increases with Reynolds number, which is a dimensionless parameter that represents the ratio of inertial forces to viscous forces in a fluid flow. As Reynolds number increases, the flow becomes more turbulent and the energy loss in the nozzle increases.

What is the significance of the nozzle loss coefficient increasing with Reynolds number?

The increase in nozzle loss coefficient with Reynolds number indicates that the flow is becoming more turbulent and less efficient. This can result in higher energy losses and reduced performance of the nozzle.

What factors influence the nozzle loss coefficient at different Reynolds numbers?

The nozzle geometry, surface roughness, fluid properties, and flow conditions can all affect the nozzle loss coefficient at different Reynolds numbers. Changes in these factors can alter the amount of energy lost in the nozzle and the resulting increase in the coefficient.

How can the nozzle loss coefficient be minimized?

To minimize the nozzle loss coefficient, the nozzle can be designed with smooth surfaces and a carefully chosen geometry that promotes laminar flow. Additionally, reducing the Reynolds number by decreasing the flow velocity can also help to decrease the nozzle loss coefficient.

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