Anyone proeficient with fluid dynamics here? Is it possible to determine the diameter of the urethra, based on the speed at which urine is expelled? From this data, can we obtain a rought estimate on girth as well as length of a penis? I was thinking of relating the sound of the urination to force and then size of a penis. Any help in this endeavor will be appreciated.
>Is it possible to determine the diameter of the urethra, based on the speed at which urine is expelled?
No, because the mass flow rate of urine is something in your control. If you use your pelvic muscles you can pee harder and if you completely relax, the pee will be weak. And because this value is not constant and can vary from person to person, you won't get any good estimates.
diameter is only one of the variables. you would also need the relative roughness of the urethra to calculate the reynolds number, which may or may not be a function of girth.
so, i suggest doing some research on all the variables and coming back.
This. The main thing that controls the speed at which urine is expelled is the pressure applied to the bladder, not the size of the urethra.
You don't need to go that far... water/urine can be treated as an incompressible, inviscid flow which reduces the (NS) equation down to Bernoulli's Principle.
In theory, yes... if you could ensure constant exertion applied during urination and the exact urinal shape and size, distance from pee stream, atmospheric conditions, and acoustic conditions. It would be very tough. Also depending on the sensitivity of the sound monitoring equipment, variability in dissolved solutes in urine samples will further fudge your data.
Well I've given it more thought since this post, and I actually don't think it would be impossible to create a function that could give a *rough* estimate of some artifact of urethral diameter -- whether or not this correlates at all to penis girth/length, I do not know. You would have to create some basic relationship of the sound water makes against a flat surface at fixed distance (oscilloscope should work nicely) and the diameter of the water outlet. Once you've established this, you could further study how two or three key variables influence the way sound interacts with the receiver and model it as some mathematical function -- where measurable constant values are applied for things like acoustic resonance with respect to volume of room, etc etc. to help normalize sound value. I'm also envisioning further mathematical analysis in the form of partial derivatives, like "change in sound magnitude with respect to changing applied pressure to the fluid at constant distance to toilet."