Computational Fluid Dynamics
Discussion
Here's an interesting little wab based app, you can draw a shape and place it in a virtual wind tunnel.
I tried creating a high downforce wing, then I added a gurney flap to see the difference.
I hadn't realised that vortices detach at regular intervals, can any aeronautics guys confirm that actually happens?
I tried creating a high downforce wing, then I added a gurney flap to see the difference.
I hadn't realised that vortices detach at regular intervals, can any aeronautics guys confirm that actually happens?
Anyone interested in race car aerodynamics and with a lot of time on their hands will probably find this interesting.
http://eprints.soton.ac.uk/42969/1/GetPDFServlet.p...
http://eprints.soton.ac.uk/42969/1/GetPDFServlet.p...
I'm coming to the end of my PhD now and have spent the last three years using CFD to generate simulations of ship airwakes. Most of my work has involved the new Type 26 frigate but I've done work on a number of different ships now. I mainly create airwakes that are then used to provide realistic environments in our full motion base flight simulator. We have a number of fixed base and motion based flight sims at Liverpool uni. We've even got the front end of a Nimrod that will be used for wide body flight simulation, but my research area uses a three seat, 6DOF flight sim that's configured to represent rotorcraft.
Video
A CFD simulation of a ship creates huge data sets, nearly half a terabyte of data per 45 seconds of unsteady simulation. This is just for an average frigate sized ship, a sister project to mine is looking at the QEC which is three times the length of an average frigate and will create a few terabytes of data for each wind angle simulated. Most of the students, (and to some extent engineers in general), will have preconceived ideas that CFD is simple to do, can be done in a few days... Those 45 seconds of data require a lot of cores on a supercomputer and takes nearly a week to compute.
Once we have the data the unsteady air velocities created in the CFD can imposed onto a flight mechanics model of a helicopter, this then alters the helicopter's lift, drag, yaw, vibrational loads, engine requirements etc. Meaning the pilots get a high fidelity simulation of landing a helicopter to a moving ship, at sea. We can even alter the weather and lighting to make it really hard if test pilots get cocky.
It's not just the airwake aerodynamics either, I've also simulated the hot exhaust gas from ships and their interaction with the airwake within CFD. Looking at potential problems on both the aerodynamic impact on the helicopter and the the implications of widely fluctuating temperatures ingested into the engine.
Anyway here are some pretty CFD pictures of ships, most people are bored stupid by CFD and only really show interest when the pictures come out, if I started waffling about the applicability of Strouhal Scaling of bluff body aerodynamics, above a Reynolds Numbers of..... You'd all lose the will to live, believe me
Streamlines showing recirculation behind the bow on a small patrol vessel.
Turbulence contours for the Type 23 frigate for a 40 knot wind.
Video
A CFD simulation of a ship creates huge data sets, nearly half a terabyte of data per 45 seconds of unsteady simulation. This is just for an average frigate sized ship, a sister project to mine is looking at the QEC which is three times the length of an average frigate and will create a few terabytes of data for each wind angle simulated. Most of the students, (and to some extent engineers in general), will have preconceived ideas that CFD is simple to do, can be done in a few days... Those 45 seconds of data require a lot of cores on a supercomputer and takes nearly a week to compute.
Once we have the data the unsteady air velocities created in the CFD can imposed onto a flight mechanics model of a helicopter, this then alters the helicopter's lift, drag, yaw, vibrational loads, engine requirements etc. Meaning the pilots get a high fidelity simulation of landing a helicopter to a moving ship, at sea. We can even alter the weather and lighting to make it really hard if test pilots get cocky.
It's not just the airwake aerodynamics either, I've also simulated the hot exhaust gas from ships and their interaction with the airwake within CFD. Looking at potential problems on both the aerodynamic impact on the helicopter and the the implications of widely fluctuating temperatures ingested into the engine.
Anyway here are some pretty CFD pictures of ships, most people are bored stupid by CFD and only really show interest when the pictures come out, if I started waffling about the applicability of Strouhal Scaling of bluff body aerodynamics, above a Reynolds Numbers of..... You'd all lose the will to live, believe me
Streamlines showing recirculation behind the bow on a small patrol vessel.
Turbulence contours for the Type 23 frigate for a 40 knot wind.
Fugazi said:
stuff
Hi Fugazi, you must know Roy then, the chap that looks after and programs all the sims in the engineering dept. He gave me a tour round once, some of the stuff look fascinating and I could have spent hours playing with the Nimrod.....Do you know he manages a collection of real aircraft down at the airport too? He's always trying to get his students involved with it
I've been here since 2007, did an aerospace MEng degree here, then jumped straight on the PhD so I know the people and dept well. Roy is a Godsend, my desktop has a huge amount of RAM (64Gb and an I7 processor) so it can be very temperamental running the awful in house Windows build, which means Roy can get a lot of phone calls ...
I've been down to the open days at Speke. I'd like to get involved and was a welder/fabricator in my previous life before uni so I know my way around a toolbox, but I hardly have any free time these days. There is a student simulation group who are trying to rebuild and configure an old BAE fast jet cockpit training simulator with Roy's help too.
... I've been down to the open days at Speke. I'd like to get involved and was a welder/fabricator in my previous life before uni so I know my way around a toolbox, but I hardly have any free time these days. There is a student simulation group who are trying to rebuild and configure an old BAE fast jet cockpit training simulator with Roy's help too.
Edited by Fugazi on Monday 19th January 19:11
ianrb said:
ChemicalChaos said:
Anyone ever wondered how aerodynamic a cow is? 
But they usually stand arse first into the wind.
Fugazi said:
Stuff
Presumably your work has been outside of this requirement?http://www.legislation.gov.uk/ukpga/1989/6/content...
Ali G said:
Presumably your work has been outside of this requirement?
http://www.legislation.gov.uk/ukpga/1989/6/content...
It does, although most of my work falls under some sort of restriction, none of it comes under the OSA. The images shown in my post are based on CAD geometries freely available in the public domain and formed part of academic studies rather than consultancy work. Even then there's not much you can glean from these kind of images other than they look good in presentations http://www.legislation.gov.uk/ukpga/1989/6/content...
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