I was attempting a homework question from my Fluid Mechanics theory course. And the doubt I am asking here is not related to solving this equation using conservation of mass and ideal gas law but rather how to do it in Fluent.
I have this feeling that the slope of the nozzle wall with the centreline (which is unknown here) affects the value V2 but my professor says it won't. Then I felt like simulating it using Ansys Fluent to check whether he was correct.
So, I turned on inviscid and ideal gas governing equations as the question suggests them only. But then, when I tried to input the pressure and velocity at the inlet together using velocity inlet, I found that such an option was not there. There was something named "Supersonic/Initial Gauge Pressure", but I don't know whether that is relevant. When I tried using the pressure inlet, the velocity was entirely missing from the settings. Does this mean that the conditions given in this question are overconstrained?! Or is there a way to assign the given bc to this problem? Please help me.
I've written a code to solve inviscid Burgers's equation with Lax-Wendroff method. My professor has asked me to analize the equation with Von Neumann stability analysis. I have a problem beacouse of non-linearity. Can anyone help me or send me some references?
My question comes from the most basic scenarios of Fluid mechanics i.e.inviscid flow past a cylinder with no circulation. In that case, I see no reason why the flow should continue to trace the outline of the cylinder past the 90 and -90 mark. There is no force to the flow in that direction.
Can anyone please explain why the flow merges to meet again?
Hey guys,
i was wondering if axial/radial pump would be able to build up pressure when the fluid is inviscid. Forces can be transfered to the fluid by either pressure or shear. How is that in pumps? When I cant transfer a shear force to the fluid, can the rotor still build up pressure?
I'm having an issue with the easiest example of a nonlinear 1D PDE, the (inviscid) burgers' equation:
u_t + uu_x = 0, (1)
which can be rewritten as some convection equation
u_t + f(u)_x = 0
with flux f(u) = (0.5*u)^2. In this easiest case I use a semidiscrete method to solve (1) with periodic boundary conditions. I use upwinding in space and euler forward in time, overall resulting in a first order scheme. To test for convegence, I use the method of manufactured solutions:
For some initial conditions u(x,t), u(x,t) is a solution of
u_t + uu_x = r(x,t),
where the residual r(x,t) is the result of u(x,t) plugged into (1). Since upwinding requires positive advection speeds, and the speed is determined by the solution, u, I chose
u(x,t) = 5 + sin(2*pi*(x-t)), x in [0,1], t in [0,0.5]
as initial solution.
u_t = -2*pi*cos(2*pi*(x-t)),
u_x = 2*pi*cos(2*pi*(x-t)),
so my residual is r(x,t) = 2*pi*cos(2*pi*(x-t))*(4 + sin(2*pi*(x-t))). The residual is handled as some source term and added to the update term, after upwinding was computed.
Since - per construction - the solution should be u(x,t) for every t in [0,infty] and x in [0,1] I must be missing something obvious. Or is there a general problem with finite differences and this equation? I have an old finite volume code for reference and it works just fine.
I attach plots of both the initial solution and the solution at t=0.25.
Since matlab code is as close to pseudo code as it can get, here's the code:
clc
format long
N = 20; % Number of Points
cfl = 0.5; %
adv = 2.0; % Linear Advection speed
t_start = 0;
t_end = 0.25;
% EQ type
% type = "linear_advection";
type = "burgers";
% fd type
fd = "upwind";
% fd = "downwind";
% fd = "central";
% Initial Conditions
IC = "default";
% IC = "resi_test_const";
% switch to plot immediately
plot_immediate = true;
% Initial solution and resdiduals
if type == "burgers"
if IC == "resi_test_const"
sol = @(x,t) 5 + sin(2*pi*x);
r = @(x,t) sin(2*pi*x)*2*pi.*cos(2*pi*x);
else
sol = @(x,t) 5 + sin(2*pi*(x-t));
r = @(x,t) 2*pi*cos(2*pi*(x-t)).*(4 + sin(2*pi*(x-t)));
end
elseif type == "linear_advection"
if IC == "resi_test_const"
sol = @(x,t) sin(2*pi*x);
r = @(x,t) adv*2*pi*cos(Hi all! I'm relatively new to CFD and I have a question. I've been reading a paper https://arxiv.org/abs/1603.02652 and in the paper is plotted an "exact" solution to the inviscid Burger's equation with periodic boundary conditions and initial condition u(x,0) = mu*|sin(2x)| + 0.1. From my literature review, there seems to be a lot on numerical solvers for Burger's and I recall seeing one reference saying that there is no exact solution for when u(x,0) = sin(x). Furthermore, I have found that there is a solution of the form, for the initial condition u(x,0) = sin(x), u(x,t) = sin(x - u(x,t)*t) which again needs to be approximated numerically.
So my question is, is there an exact solution to this equation? Or is the word "exact" sometimes used to refer to when an accurate numerical solver is utilized?
Hi, does anyone know where I can find data relating to a NACA 0012 airfoil? I am doing a simulation on it but I am told not to trust my solutions until I compare it with real results. My problem is inviscid with M=0.8. When googling, it seems that all the data is viscous flow with with a reynold's number. Is there a good place to find data relating to my case or is there another way I can verify that my solution is correct?
Thanks!
Im having to compare the difference between an inviscid flow and viscous flow over a wing. Specifically looking at the amount of lift generated in both and by association the drag.
What im struggling to understand is why a inviscid flow still produces vortexing; if its inviscid its perfectly smooth right? So why should any vortex or flow seperation take place?
My main question is which flow over identical airfoils/wings would produce more lift/drag and how will the results vary?
Assuming that vortexing occurs in inviscid BUT seperation doesnt i would assume that inviscid produces more lift and less drag?
Also, for viscous flow, why not just use a pressure difference along a section of a pipe to determine the pressure drop from viscosity and then calculate the flow rate?
I'm trying to run a simulation for an RAE2822 airfoil with M=0.729, Re=6.5E6, and angle of attack at 2.31 deg. I want to run an inviscid simulation in STAR-CCM+, but if I just use the defaults in the physics settings I am using (steady, 2D, ideal gas, coupled energy, coupled flow, inviscid) I don't get a converged solution. Has anyone had a similar problem or know how I might fix this? If I use a 1st order method then I get a solution that is more stable, but my lift coefficient is too low.
Thanks!
shocksInBurgersEquation is the code I have written to find shocks given an initial continuous function to the Burger's inviscid equation. It's by no means perfect, and constructive criticism is welcome. (Also, the shocks themselves seem to be offset by some amount of time, if anyone has any advice on how to fix this, I'd love to know).
With an air cannon (a toy made of a barrel that has a round opening on one side and a membrane on the other), you can create a vortex when you hit the membrane.
I have problems understanding the process of creation of the vortex after the air exits the opening of the barrel. Many Internet sources claim that the formation of the vortex is due to the Bernoulli effect, others blame it on the Coanda effect.
Could you explain which is true and why? Thank you!
(As far as I understand, the edge of the outlet opening of the barrel slows down the outer air particles of the outflowing air. The inner air particles retain their high velocity, dragging the outer, slower particles along by internal friction. This entrainment creates a negative pressure at the area around the opening of the barrel (Coanda effect). Air particles from the inner area of the air stream flow into this area to compensate for the pressure differences. This creates the vortex.)
Do your worst!
It really does, I swear!
For context I'm a Refuse Driver (Garbage man) & today I was on food waste. After I'd tipped I was checking the wagon for any defects when I spotted a lone pea balanced on the lifts.
I said "hey look, an escaPEA"
No one near me but it didn't half make me laugh for a good hour or so!
Edit: I can't believe how much this has blown up. Thank you everyone I've had a blast reading through the replies π
Theyβre on standbi
Buenosdillas
Pilot on me!!
These documents are considered to be fakes but some such as Stanton Friedman have always contested that. I am not going to go into the arguments as to whether the documents are real or not here because it is more detective work than science. If you are convinced that they're bogus then feel free to ignore this post.
I however find the scientific descriptions of the alleged UFO characteristics to be intriguing for two reasons. Firstly because surprisingly there is no woo-woo, it is all grounded in mundane aerodynamics which is unusual for a UFO hoax. Secondly everything I can understand appears to make sense and is too obscure for a random hoaxer to have known or gone to the effort to research. Whoever wrote it would have had to have had some background in aeronautical engineering.
In this document https://majesticdocuments.com/pdf/rdlab_analyticalrpt2sept47.pdf it claims that the lack of rivets and visible joins is to reduce drag. This makes sense. I don't understand what c.) is trying to say in regard to Bernoulli's theorem however. d.) makes reference to NACA aerofoils which are a real and widely used family of aerofoils. Interestingly the NACA 23015 aerofoil looks similar to the profile of a B-2 (it's actual aerofoil is probably classified). Again the reduction of parasitic drag by removing protuberances is mentioned. "The induced drag lessens with the circular span inversely with the low aspect-ratio of the wing" appears to be stating that a circular wing has reduced induced drag (true) but induced drag is inverse to the aspect ratio (also true). Again. whoever wrote this clearly knows the difference between different forms of drag and what causes them.
in section e.) I don't know anything about seaplanes but it seems to go into a lot of detail about similarities to that. Of concern is the mention of computer controlled flight. Did they have any clue of such possibilities in the 1940s? Was the word computer even in use?
This document https://majesticdocuments.com/pdf/cia_oscurapeak.pdf Again reads like a standard aerodynamic research document. The assumptions made in their alleged attempts to come up with a hypersonic UFO model are pretty standard when setting up a potential flow mathematical model. "the viscosity of the fluid flow can be neglected", i.e inviscid flow. The flow is vortexless i.e irrotational and so forth. The Helmholtz laws are real, https://en.wikipedia.org/wiki/Helmholtz%27s_theorems I assume they are referencing the third the
... keep reading on reddit β‘
Dad jokes are supposed to be jokes you can tell a kid and they will understand it and find it funny.
This sub is mostly just NSFW puns now.
If it needs a NSFW tag it's not a dad joke. There should just be a NSFW puns subreddit for that.
Edit* I'm not replying any longer and turning off notifications but to all those that say "no one cares", there sure are a lot of you arguing about it. Maybe I'm wrong but you people don't need to be rude about it. If you really don't care, don't comment.
