Recent content by Omish

I got it completely thanks to your explanation and some more little experiments. Thank you so much. This was also very useful.

This could be the answer except one problem. In that way when the tube is completely empty, there's no need to be any ST (or as you say change in water sarface). Nevertheless the water is sucked from container when we put the tube in it. How do you explain this?

Please read the question carefully ! Seems you didn't get the point. First of all it doesn't act like friction forces, in other words F_capillary is not always equal to weight of column of water necessarily! (if it was equal, the water wouldn't be sucked up in the first place) Then we have h_1...

Here is a picture of it.

Yes they're in the same direction so they both help the water go up, but this actually won't happen. My question is why?!

Well, 1- wight 2- ST on the top side 3- ST on the bottom side If by the question you mean that the sum of first & third force cancle the 2nd force I think it's wrong. I believe that both STs are in the same direction (upwards) since the tube can hold more water while out of the container. I...

When we put an empty capillary tube in a water container, the water goes up a little bit by itself until the surface tension (ST) force is equal to its weight .This shows that unlike friction, this ST force acts individually . So if we take out the tube out of the container, and drain a little...

I'm sorry .I should have actually said "Total" and I corrected it. Total temperature is (if I'm not mistaken) Static + Dynamic temperature, and total temperature itself is defined like this: where gamma is the ratio of specific heats and M_a is Mach number.

What temperature does thermocouples show? Static or Total? And also in formulas for example Q(dot) = m(dot) * C_p * (T2 - T1) which temperature should be used precisely?

yes. I tried to use the centerline as my axis BC but Fluent gives errors and doesn't even run for 1 Iteration. The error is about diverging, but I'm pretty sure it's irrelevant; The cause I guess is that the axis is not straight but twisted because of U-shape. any other suggestions?

I finally found the problem ! So weird. for straight pipes the answer is wrong also UNLESS you model them as AXISYMMETRIC ! for my geometry (U-shaped pipe) is it possible to model it axisymmetric? if not what can I do now?

Viscos-Laminar model has been chosen all the time. And I think it is long enough in start and end. L_e=0.06*Re*D=0.06*190*0.01905=0.218 m My pipe geometry is exactly like this: 1 meter straight pipe, a 90 degree bend, 11 cm straight pipe, one more 90 degree bend, and 1 meter straight pipe again...

I found s.th about water test I had m I tried again with water. But I changed the velocity to make it laminar flow. Something new I noticed. First I set Re to about 2300 (a bit less) and the fault was 16 percent (theoric=18.92 , Fluent=22.02 both pa). I thought the problem is solved ! BUT then...

Yes. I'm sure about this.

Let me solve the model with water one more time and tell you the exact theoric and Fluent answers. So we won't have to worry about the material anymore.