# Engineering - fluid mechanics

1. Sep 10, 2014

### Edson_arantes

I have a question about fluid mechanics. I know it's not completely physics, but in the end, it involves physics:

Suppose you are computing the blood flow in an artery segment with length 3 cm and diameter 3 mm. The artery has a constant cross section and its positioned horizontally in your computation. Assume the density of the blood to be 1,000 kg/m3. Blood is incompressible. At some point in your computation, in a time period of 0.025 s, the average flow velocity you specify at the artery inlet changes from 0.2 m/s to 0.6 m/s. Based on the Bernoulli's equation, at the middle of that time period, what do you estimate/expect the blood pressure difference between the artery inlet and outlet ?

Thanks

2. Sep 10, 2014

### Staff: Mentor

Hi Edson_arantes. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

These forums require that along with quoting the textbook question you also write the applicable equations, and that you include your attempt at the solution. Your effort here is somewhat lacking. Please remedy this.

Last edited by a moderator: May 6, 2017
3. Sep 10, 2014

### Edson_arantes

So, I used the Bernoulli's equation for unstedy flow, then I assumed that the acceleration is uniform (but i think it's wrong). Taking the constant acceleration, I measured the distance the blood traveled in the middle of the time (0.0125s) and the velocity in the beginning and at t = 0.0125s. Then, I just substituted in the formula. The problem is that I don't think it's this simple, because the blood velocity may not vary linearly.

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