4
$\begingroup$

enter image description here

Hi.. The question above is one of the tutorial question from fluid mechanics textbook. In the textbook solution for this question, the density of the methane gas stream at downstream was computed with the ideal gas law equation.

enter image description here

What I don't understand is it possible for us to compute the density of the methane stream at downstream with the equation on below provided we know the density of methane gas and mach number at downstream.

enter image description here

From datasheet, the density of methane gas = 0.678 kg/m^3 and Mach number at downstream, Ma= 0.4537

The answer from the textbook solution was 2.858 kg/m^3

Improve this question
$\endgroup$

1 Answer 1

Reset to default
2
$\begingroup$

static thermodynamic varibales before and after shockThe text book answer is correct. I think you missed to calculate the density of the downstream of the shock. the equation you entered is valid only in the region 1 or in region 2. means the isentropic relations are not valid across the shock. Across the shock you have to use normal shock relations. Then you would get the right answer

Improve this answer
$\endgroup$
2
  • $\begingroup$ If the correct answer given in the original post is 2.858 kg/m^3, how can you claim your answer is correct? $\endgroup$
    – Solar Mike
    Commented Nov 28, 2017 at 9:28
  • $\begingroup$ Hi Mike, probably the ratio of specific heats is different from my calculation. I have taken $k = 1.304$. apologies for not mentioning it. $\endgroup$
    – mustang
    Commented Nov 28, 2017 at 9:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.