Browse by Topic

# Date Archive: 2015 December

Products

## Wolfram SystemModeler in Rotor Dynamics: Internal Damping

Explore the contents of this article with a free Wolfram SystemModeler trial. In 1869, Rankine extended Euler and Bernoulli's century-old theory of lateral vibrations of bars to an understanding of rotating machinery that is out of balance. Classical dynamics had a new branch: rotor dynamics. Machine vibration caused by imbalance is one of the main characteristics of machinery in rotation. All structures have natural frequencies. The critical speed of a rotating machine occurs when the rotational speed matches one of these natural frequencies, often the lowest. Until the end of the nineteenth century the primary way of improving performance, increasing the maximum speed at which a machine rotates without an unacceptable level of vibration, was to increase the lowest critical speed: rotors became stiffer and stiffer. In 1889, the famous Swedish engineer Gustaf de Laval pursued the opposite strategy: he ran a machine faster than the critical speed, finding that at speeds above the critical threshold, vibration decreased. The trick was to accelerate fast through the critical speed. Thirty years later in 1929, the American Henry Jeffcott wrote the equation for a similar system, a simple shaft supported at its ends. Such a rotor is now called the de Laval rotor or Jeffcott rotor and is the standard rotor model used in most basic equations describing various phenomena.
Computation & Analysis

## Wolfram Community Highlights: Medicine, Drones, KenKen, and More!

With some impressive new features, new forums, and many new members, Wolfram Community has had a great year. As we approach the end of 2015, we wanted to share a few highlights from the last few months' excellent posts on the Wolfram Community site.

#### Drones

Interested in drones? Check out these posts. Connecting ROS to the Wolfram Language, Or Controlling a Parrot ArDrone 2.0 from Mathematica, by Loris Gliner, a student in aeronautical engineering. Loris Gliner used his time in the Wolfram mentorship program to work out how to connect the Wolfram Language to the Linux Robot Operating System. He includes code examples and a video showing the flight of a Parrot ArDrone 2.0 controlled via the Wolfram Language.
Announcements & Events

## The Wolfram Language Worldwide Translations Project

It has been quite a while since I graduated from college in Germany with a degree in mathematics. Of course, I have plenty of memories of long study nights, difficult homework assignments, and a general lack of a social life. But I also vividly remember having to take programming classes. I had done my best to avoid these for as long as I could. But when they became part of my curriculum, I could not continue ignoring them. Not being a native English speaker, I was not just dealing with the concept of programming, which was completely abstract to me---I also had to find my way around function names always given in English. Though I struggled in those classes, I successfully graduated, and years later am now part of a project that would have helped me tremendously back then: the Wolfram Language Worldwide Translations Project. The Wolfram Language Worldwide Translations Project provides any non-English-speaking programming novice with an effortless way into the Wolfram Language. It aims to introduce the Wolfram Language while at the same time addressing any lack of English language skills.
Products

## Background

Explore the contents of this article with a free Wolfram SystemModeler trial. Today, many helicopters launch from and land on ships at sea. Some are conventional helicopters, both commercial and military, and some are drones. In Wolfram SystemModeler, we now have a system for simulating helicopter landings and launches that includes waves and ships. The models have been used for the design of mechanical parts, autopilots, landing criteria, and operational limits.

## Major components of the system

The aim has been to develop a model with an accurate depiction of the waves, ship motion, and helicopters in such a way that the results can be used not only qualitatively but also quantitatively in real industrial applications. The first task is to calculate the motion of the landing platform mounted on the ship's deck. There is commercially available historical wave data for different seas and oceans. Since access to this data is expensive, we will instead describe the waves mathematically. A model of the forces on the ship's hull was developed with classical analytical theory. With the waves and ship hull forces, the motion of the ship's landing platform can be calculated. If we assume that the helicopter landing does not influence the landing platform motion, the system is simplified. We speed up the simulation by storing the motion in a database for the different wave heights, lengths, and directions, and the ship's speed. Typically the database will include wave heights of 1, 2, 3, and 4 m; wave directions 0, 30, 60, 90, 120, 150, and 180 degrees; wave lengths 100, 150, and 200 m; and ship speeds of 5 and 10 knots. The helicopter was modeled with the MultiBody library. It includes mechanical parts such as rotors with gyroscopic effects and landing gear with hydraulic dampers. Friction models for wheel-deck interface and flexible beams for the rotor blades have been developed. We have also developed a simple autopilot where the landing algorithm is implemented and tested. For one application, the model has been run with the actual autopilot as hardware in the loop.
Announcements & Events

## Wolfram Programming Lab Now Available in Beta

The Wolfram Language provides a unique opportunity to revolutionize programming education, and we've been working on ways to deliver the language for students and educators. Today we're making available a beta version of Wolfram Programming Lab. You can access it free on the web in our Wolfram Open Cloud. There are subscription versions that provide additional capabilities on the web and that include native desktop versions for Mac, Windows, and Linux. Wolfram Programming Lab is an interactive programming environment that contains dozens of "Explorations"---step-by-step guides to creating programs with tiny amounts of code. Each Exploration gives the starter code for a program, and students are encouraged to dive in and change the code to create something new. Students can also challenge their understanding by solving exercises in the Go Further sections available in most Explorations.

## I Wrote a Book—To Teach the Wolfram Language

An Elementary Introduction to the Wolfram Language is available in print, free on the web, etc. I wasn't sure if I was ever going to write another book. My last book---A New Kind of Science---took me more than a decade of intensely focused work, and is the largest personal project I've ever done. But a little while ago, I realized there was another book I had to write: a book that would introduce people with no knowledge of programming to the Wolfram Language and the kind of computational thinking it allows. The result is An Elementary Introduction to the Wolfram Language, published today in print, free on the web, etc.
Computation & Analysis

## A Year of Runkeeper: Analysis and Visualization

About a year ago, I decided to record every single move I make using Runkeeper, and now I want to make some visualizations of my activity throughout the whole year. This is a fairly straightforward project where I will download the data from Runkeeper, then use the Wolfram Language to process, analyze, and visualize my activities. I will show how to create animations like this one that superimposes 24 minutes of all my activities recorded in Barcelona: