And now for something completly different....

I should apologise for the lack of posts over the last few weeks, I am in the middle of my fourth year exams and the last few weeks before the semester finished I was run off my feet with a never ending list of coursework and reports. One of the modules had me doing some interesting programming of the vortex sheet produced by a wing to investigate the wing tip vortices's to see if the wake interfered with the tailplane. So while I have a few days between exams thought I'd write up a bit on this because having researched this topic, I know how tricky it was to model. The code is written in Matlab and a link to the scripts will be given at the bottom of the page. The mathematics behind computation of the vortical wake produced by a wing is too long for me to delve into for this mid-exam blog post, if there is enough interest I am more than happy to cover this in a future blog, but for now I will just gloss over the details and show the pretty pictures. After the last few weeks of non-stop revision digging out my notes and writing what would amount to another small report is the last thing on my mind. Besides, the UK is in the grip of a heatwave at the moment, it is nearly 28`C outside which reduces my desire to write up my derivations even more! For those of you who are reading this from sunnier climates it might sound like an average day for you, but for us it is almost unheard of on this rain drenched island.

Here is the classic NASA video of an experiment to show the vortex produced by the wing of an aircraft. These wing vortices's can interact with the empannage of the aircraft producing unpleasant effects as well as interfering with the behaviour of other aircraft. This is a well known phenomenon among large aircraft and most people know there are separation limits that govern take off and landings for commercial aircraft, but this video shows that the vortex sheet produced by an microlight aircraft is enough to interfere with a second microlight.

Here are a couple of screen shots from the my wake code that predicts the wake produced by a small aerobatic trainer type, aircraft which myself and several of my classmates designed for one of our uni modules. After finding the wake, the Matlab code will also plot the wing, fin and tailplane geometries to see if the wake produced any undesirable effects on the tail surfaces. 

The two files at the end of this post are the script 'wingwake.m' and function file 'vortex.m' for the wing vortex model. You'll need to download both into the same destination folder but only the 'wingwake.m' file needs to be run, and you will also of course, need a copy of Matlab. I will one day modify the code to add in the effects of flap deployment and tidy it up with a GUI, but I don't have the time yet. I never have the time for anything these days least of all the interesting projects. I haven't touched my gas turbine dashboard for a while and I'm itching to get back to it. 

Talking of interesting projects, fingers crossed I will start a PhD in a few weeks looking at CFD of ships with a view to improving the design process with respect to the handling qualities of a helicopter during deck operations.. I can't wait!

WingWake.m
Vortex.m

Wild goose chase.

It is Tuesday night, three days ago, the night before an exam... This happens, true story..
My four year old niece decides she wants to play with the quails. I had bought my mother a pair as part of her suburban dream of starting some kind of farm in her garden. Anyway my niece inadvertently releases a quail into the garden which then takes an instant dislike to any efforts to catch it, and hops the eight foot high wall into the neighbours garden. My brother, father of the now crying child jumps the over the wall, meanwhile the quail finds his new garden is not suitable for its taste, probably a lack of storage and decides to fly, magnificently for a quail, the twenty feet over the alleyway into another garden which is perfect quail habitat. Four foot high weeds, brambles, nettles, grass, bricks and an outdoor toilet that would look good in trainspotting. Que an hour later after much careful poking, swearing, scratching, shaking twigs and false alarms, where I stalked and caught a dried up plant that looked suspiciously like a quail. Dammit.
All hope had faded until my brother poked the quail up its bum and it took off again, clearing another eight foot high brick wall and into another garden. I started to sense a pattern developing here that quails can fly and they can fly better than I can climb walls in my bare feet. Within seconds we are perched on top of the wall trying to see where it went, at which point the neighbours two dogs appear. They are mental, they are angry. So angry that my bottom hole relaxes slightly. Oh fiddlesticks, that's going to be one tasty quail sized snack for a dog.. Then a woman appeared and visions of having to explain myself to the police flashed through my mind. Surprisingly the woman who lived there didn't appear to be alarmed by one guy stood on her wall brandishing a children's rock pool net and another waving a broom and gibbering nonsensically with what only can be described as a gingery-brown afro, (I had washed my hair earlier that day, but didn't condition it, and now I'm paying for that with a beautiful, but inexplicable hairstyle, but I digress)... Two minutes later and the quail found himself in the back of the net and back in the run, the niece was suitably shouted at and I'm left with an arm full of scratches, an afro full of twigs and one pissed off quail...