# Inlet option

Hello,

I'm using the inlet quite often. The problem I encounter is that I have no simple way to impose a flow rate.

Right now I must import my geometry and launch the simulation once in order to know the number of inlet points, then I can calculate the velocity I impose for the inlet and finally launch my simulations.

Maybe I missed the option ? Is anybody else wishing that such an option would exist ?

Kind regards

• Hi TPouzol,

The option to assign a flow rate is not currently implemented in v5.0 (that I know of), so you cannot directly impose Q`dot` or m`dot`.

However, I don't understand why you can't simply calculate your U`avg` from the desired flow rate and apply that to inlet particles? I suppose you know the dimensions of your inlet area since you are using a CAD file. It's certainly not ideal due to the no-slip condition not being satisfied at the inlet near the walls, but if you let sufficient length flow wise, the flow should develop.

Another more advanced option I could think of is to extrapolate a velocity profile either analytically or by running a simulation just for this the way I described above, then use the fitted function to initialize your inlet velocities. Basically a v(x,y,z) or v(r,theta,phi) that depends on the position of the inlet particles. This way you would only have to place inlet particles correctly, and need not worry about calculating the velocity to impose. However, this would require small code implementations.

Best,

Angelo Tafuni

• Thanks @taffo

About calculate the Uavg, it's basiccaly what I'm doing. But in the problem is to estimate the number of points of the inlet. I'm importing rectangular inlet, so I have a uncertainty of 2 raws in both dimensions of the rectangle. It's feasible and actually retrieving the number of points by launching a dummy simulation is what I do and this way I have no doubts.

However, if you are really after imposing a flow rate, then it is not ideal. I though of this suggestion because it is what has been done to define the density of floatings: you give a total mass rather than a density. This way you are not sensitive to resolution of last minute geometry change. And it is easier to lauch a simulation

Best regards,

Tanguy Pouzol