There is an old story from an unknown Native American tribe. A wise grandfather tells his grandson that there are two wolves battling inside him. One good and one bad. The grandson asks,
"Grandfather, which wolf wins?".
The careful reply is,
"The wolf I feed."
Which wolf are you feeding?
This note is written in the time of the Corona virus (2020). You are probably at home. You may even be newly graduated engineering PhD or BS but without a job. Right?
Wrong, you already have a full-time job: You. Your full time job should start to later than 8:00am and end no later than 6:00pm every workday. Give yourself Sunday to rest; you will need it.
Your job search is a priority. Somebody is hiring; you just don’t known them. They don’t know you. You have a unique opportunity to impress. Make a list of engineering skills that you can learn, improve, or teach. Start with these:
Learn how to use CATIA. Get a student license for $100. This is an essential communications skill.
Start a website detailing your skills and capabilities
Teach a short course and post on Youtube. Break into 15 minute segments and use a screen capturing program to show the process.
Learn how to use rendering software. This skill allows you to make compelling proposal and project graphics.
Volunteer to be a journal reviewer
Learn how to simulate electrical systems with LTspice
Learn how to simulate structural or fluid systems. Example ANSYS.
Learn how to use Simulink in Matlab
Join an association outside of your area of expertise. Do a deep-dive into the association’s library of materials. Take notes.
Get your Part 107 unmanned pilots license. Get your Technician or General class amateur radio license. Find other certifications that you can complete.
Update your python programming skills. Make a GUI multi-threaded frontend for a task that you use often. Post on website.
Take an AI/ML course: OCW or youtube or a book.
Read through all of the SBIR projects offered by NASA, DoD, DOE, etc. How do your skills match? Find and document a project that you could feasibly complete. Search through old SBIR funded announcements and see which company won similar projects. Send your project capabilities to this company. Voila; instant job opening.
Get a post-doc position.
Make a deadline. Complete on-time. Show deliverables.
80% of your colleagues won’t search for ways to improve.
Of those remaining, 80% won’t finish & document even one task.
The 4% (i.e. 20% ∙ 20%) are exactly what your future boss is searching for in a new employee. You demonstrate competency and are low-risk.
I believe that you should update your resume with a “Quarantine” work history showing what you accomplished. The key point for your future boss is demonstrating a strong work ethic at-home with no supervision. This requires documentation and links to delivered product/projects.
Q: Could you explain to me why the vortex does not appear to be coming from the tip of the wing, but rather several feet closer to the fuselage on this Boeing 777?
A: Good question. The answer is that the vortex is visible where the change in lift distribution -and thus, shed vorticity- is highest. The flaps are extended, which creates a sharp discontinuity in the wing geometry and lift distribution.
Here’s the physics:
The extended flaps increase both the wing area and the effective angle of attack for the inboard wing. (see: Thin airfoil theory)
The increased area and angle of attack increase the lift being generated on the inboard panel.
Shed vorticity is proportional to the spanwise derivative of the lift distribution.
The vortex rotation decreases the local air pressure and temperature below the dew point. Water vapor condenses into a fine mist. We see this fine mist.
The vorticity is transported downstream (i.e. Helmholtz rule #3)
Notice the spanwise lift coefficient is visually displayed with a vapor cloud above the upper wing. This cloud confirms that the spanwise lift coefficient has the largest decrease at the flap tips.
You should remember that the entire wing is shedding vorticity. We see the vortex at the flap tip. If the humidity were higher, we might see additional vorticies.
Ground effect is responsible for the slight outboard track of the visible vortex. As the aircraft descends further, the shed vortex will likely be pushed further outboard; induced drag (for a given CL) will decrease.
It is not true that a vortex is only generated at wingtips or flap tips. Physics demands a smooth lift distribution (regardless of what we see).
In 2019, I spent the summer in Greenland at EastGRIP on the permanent ice sheet. This is a overview of the deployment. The Remote Sensing Center where I worked received funding from the University of Copenhagen’s Niels Bohr Institute (NBI) and NSF to develop ice and snow radars. Our objective was to perform fine resolution ice layer measurements with radar systems mounted on a surface vehicle. At the end of the summer, our project deliverables were: 4 systems built and operated including the first known ice-layer survey in the L-band (1-2 GHz). This was a unique and enjoyable opportunity.
At the end of 8th grade, I anonymously received the 1989 Proceedings of the National Space Society’s Eighth Annual International Space Development Conference.
To this day, I have no idea who sent it.
Someone knew of my interest in aerospace. I have no idea why they picked these particular proceedings, as it was well past 1989. I still have the book. Thanks to anonymous! Sometimes the mysteries of life are never known.
The dutch roll flight mode shows up in a yaw only behavior driven in frequency by the yaw stiffness Nβ and in damping by yaw damping Nr. A pilot would identify the behavior as a snake dominated dutch roll behavior. With zero effective dihedral, we could also reasonably expect only little to modest yaw-roll coupling through the rate terms, which would be primarily driven by the vertical offsets of surfaces. For the engineers, this simplified 2DOF model of dutch roll has a frequency and damping term approximated as: (derivation)
Interestingly enough, the dutch roll behavior seems to appear even if the aircraft has zero effective dihedral AND zero effective yaw stiffness, provided the product of yaw damping and sideforce derivatives are positive. Both Nr and Yβ are almost always expected to be negative.
Coupled Roll-Yaw Analysis
The dutch roll flight modes show up in higher fidelity dynamics models. The lateral 4DOF model below contains the spiral, roll, and dutch roll modes with sideslip, roll rate, yaw rate, and roll angle perturbation states:
The USS Alabama Battleship Memorial Park in Mobile, AL displays an interesting collection of WW2 ships and aircraft not normally seen. The collection includes several rare museum items. The park is well worth the visit. https://www.ussalabama.com/
The Battleship Memorial Park visit is contained in 3 parts: