Recent content by obad

Yes I am considering x-momentum over that part of the control volume.

Alright, thanks for telling me the difference ;) In fact I calculated the inflow and outflow stream thrust as well as the nozzle surface force both with your definition of absolute pressure (my static pressure) and gauge pressure. However, in terms of error it doesn't really make a difference...

I'm using static pressure. I guess that's what you mean with gauge pressure.

Hi, I calculate the stream thrust in x-direction (nozzle axis) as: I = m_dot*u_x + p*A_x So what I first did is calculating the inflow stream thrust I_in and the surface force F_nozzle. Then I can calculate the stream thrust at the outlet: I_out = F_nozzle - I_in. In this way I don't need to...

Hi guys, I need to determine the performance of a single expansion ramp nozzle (SERN) from CFD results with different nozzle pressure ratios (NPR). For some NPR the nozzle is overexpanded and for some underexpanded. Now the impact of the control volume definition on especially the axial thrust...

Hi guys, I'm struggling to understand why an increase of entropy is directly linked with a decrease of total (stagnation) pressure. I have an idea, but I'm not sure if this is right. My understanding of the problem is as follows: Shear stress (friction) is a part of the entropy production term...

Hi Jack, I had a look at Equation (4.31) since it is used for the derivation of Equation (4.46). This equation is used in the derivation of the equations that describe Fanno Flow. I inserted wall shear into the energy equation as the author suggests it in the footnote by adding \tau_w L...

Hello everyone, I would like to refresh this thread with some new thoughts. I'm still not completely satisfied with the way viscosity effects the flow through a duct. I understand that viscosity does not represent an energy source or sink, but only converts kinetic energy to thermal energy. So...

Thank you Jack for your answer! Your answer is logical. Viscous heating is simply the conversion of kinetic energy to heat. To recap, if we get back to the simplifications that I made in my first post, we would also have to cancel the integral that sums up the energy that enters and leaves the...

Hi guys, I have a question to you that has been bothering me for a while now. It is about adiabatic flow in a duct or more specifically in the air intake of a jet engine. In lectures and textbooks it is always stated that the total temperature in an adiabatic flow does not change. Hence the...

Hi Doug, thanks for replying! Ok, so my initial thoughts were not too far off of what's happening. So the velocity v of a fluid parcel would then be the average velocity of all the molecules together, right? Which means that if my fluid parcel is moving parallel to a wall less molecules will...

Hi everyone, I'm new here and I have a question to all the physicists out here in the forum. I'm an aerospace engineering student and there is something that has been bothering me for quite a while. That is: Why does the static pressure of a fluid in motion change? Don't get me wrong, I'm...