Recent content by MARECHAL

Probably due to the placement of the two points of measurement of pressure, I put them inside the tube but at the periphery of the internal section, so I take measure of pressure at the points where the speed is low instead of at the center of the tube where the speed is more important. With the...

Chet, Thank's for your reply, sincerely. Yes sorry, Δp is in Pa, I found a mistake in my data since I wrote my reply, the value of L is 13 mm ; I must reviewing all calculation, it is not the only one error : the results I gave are not k but 1/k :oldfrown:. Since I am on PF, I do any mistake...

Here :

Good Afternoon, I'm a little bit disappointed by my calculation, sure I made a mistake, but where? By experimentation k is not constant ; from 0,16 @ 0,52 m/s to 0,07 @ 6,88 m/s and with calculation k is 1,3e5... something is wrong. Please see my (bad) calculation in this upload file :

Chet, Oops! Ok... the conductivity of the fluid... By analogy to electrical resistors, it is a good "picture" for me to understand the permeability. I'm going to take my calculator and calculate now. Next week, I will try to measure ∆P with an instrument and compare it to the anemometer, with...

Chet, I stop my calculation few minutes ago and post this reply, I'm afraid to make you angry with my difficulties to understand, but, I have a doubt again, If K= k/2 (K = two honeycomb in series, and k = one honeycomb) why taking L for one honeycomb? in the formula : Q = (K.A.∆P) / (μ.L) If I...

Chet, I'm confused of course. I was proud of my calculation. I ready to review them and come back here again for correction or not. This wind tunnel is very long... How can I thank you for your patience?

Hello, I do that for memory before experimentation and before verification between theoretical and physical. Could you saw it and tell me if it is ok ? I have a doubt about the theoretical results it seem to be strange, but I have no experience in this kind of physic. Nice week end, and thank's.

Yes I try this and gave the results later. Now I have all I was looked for. I must do some modifications on the bench to try what you propose, I will not missing to gave results of the experiment and calculation. Have a nice day and great thank's again.

Chet, What add to this... With your help it is clear... When I'm alone in front front of my paper, it is big headache and a brain storming. I understand my mistake, I considered six equilaterals triangular in each straw with a side of D/2 and then the black out. If I can go too far with you...

Chet, If the nominal diameter of the straw is 4 mm, I can deduce the area of each equilateral triangular is : A = ((2.2). √3) / 4 so A = √3 = 1,732 mm2. But after I don't know how to determine what you name by total cross sectional area. Could you suppose that each straws is composed with six...

To Chet, I need to read and re-read to understand your last post before answering you (if I can), I must tell you my level in geometry is very bad amplified by my precarious English vocabulary. Let me have a little reflexion about your explanation.

To MrAnchovy: Yes this bench is home made and currently existing. Because of the too high air speed of the fan at it minimum voltage, I looked for having around 0,2 m/s at the minimum voltage of the fan, I had the idea to put this filter, this screen, between the two sets of straws only for...

Hi Chet, Hoping I understand you : Straws are laid out in an kind of hexagon for some of there, and cylinder for other, yes I can neglect the flow between the straws. I do not be able to translate your question " total cross sectional area,..., assigned to each straws". Yes I saw Poiseulle law...

To Mister Anchovy : Because the anemometer is a mechanical system, even if it is currently accurate, I'm not sure it was steady in time (dust and usury of bearing). Because with my project I will have two "source" of measurements of air speed in the tube, I will know with more insurance...