Learning Forum

[Jason Sum]

NA

[Rob]

That looks like the flow didn't develop very well. Can you post the velocity contour so we can see what's going on? As an aside the angle and shape of these sorts of valves is very important, small deviations can have significant effects on the results: power fluidic devices use this to control flow. 

[Jason Sum]

My trial on this T45 single-stage tesla valve is just for myself to understand the flow physics behind when there is pressure difference driving the inflow. 

Below are result of transient velocity and pressure contour plots under convergence:

My concern is, the passive scalar of incoming air shown in previous comment gradually filling up the valve, but not similar to the result from the Holzman CFD Youtube video (only "concentration/portion" of incoming air tracing). I would like to know is sth wrong about my setup of UDS. Thank you!

[Rob]

Is this for water, and what is the scalar diffusivity? 

[Jason Sum]

It is air flowing from inlet of the valve (single phase). I set scalar diffusivity as 1, following some online videos on setting, not sure if it is not making sense. I would like to know the way to obtain the visualised result like the one from Holzman CFD Youtube video as shown above. Thanks for the guidance!!!

[Rob]

Ah, that'll explain it. The scalar is diffusing far too much. Treat the scalar like a species, and divide the typical value for that species diffusivity by the fluid density (scalars don't really have units). Liquids will be diffusivity of 1e-9 to 1e-10 or so - look it up as I usually have to.