"Mega" Molecular Workbench applets

The Molecular Workbench software allows developers to create interlinked simulations. This allows many simulations in just one applet, which I call a "mega" applet. The following example, which provides simulations of physical phenomena at different scales, shows how this works.

 

[ Click to go to the applet ] 

Here is another example of molecular dynamics simulations of pressure conveyance in different settings through fluids:

[ Click to go to the applet ]

A Molecular Workbench "mega" applet provides rich user experiences similar to Web 2.0, which can be designed using the software's authoring system. This is similar to Macromedia's Flash software.

Comparing convection and conduction using Energy2D

The following are two Energy2D simulations that compare convection and conduction, which should run within this page if you have installed Java and Java applets are enabled with your browser. The first one shows the case of natural convection. The second one shows the case of forced convection.

Instruction: Click inside a simulation window. Press 'R' to  start or stop, 'T' to reset, 'L' to reload the initial configurations, and 'G' to open or close a graph. The virtual temperature sensors can be moved around, though most other pieces are locked to their positions. Right-click on the windows for more actions.

Natural convection (driven by thermal buoyancy):

Forced convection (driven by airflow):

A Von Kármán vortex street.

The following screenshot shows a typical Von Kármán vortex street produced from the second simulation. Energy2D is also capable of producing other interesting fluid patterns such as mushroom clouds, Bernard's Cell, and the Kelvin–Helmholtz instability.

More generally, Energy2D is a Java application that allows users to create interactive, real-time simulations of heat and mass flow. A simulation you create can be easily placed on the Internet just like what you saw above.

On a separate note, below are two results for conduction simulations using Energy2D that illustrate the circuit analogy: Ohm's Law is the electrical analogy of Fourier's Law of Heat Conduction. It is interesting to note that Ohm actually drew considerable inspiration from Fourier's work on heat conduction in the theoretical explanation of his work (see Ohm's Law in Wikipedia). Ironically, today's students seem to be more familiar with Ohm's Law than Fourier's Law. So the circuit analogy is used in textbooks to help students understand heat conduction.

The analogy to a parallel circuit.

The analogy to a series circuit.

Why do metals feel colder? An infrared view

Metals feel colder because they conduct heat faster, not because they are really "colder." This is often a misconception from students. A very simple IR experiment may dispel this misconception by visualizing what is going on when you touch a piece of metal and a piece of paper.

Lay a piece of aluminum on a foamcore board. Then cover it up with a piece of paper. Put one hand on top of the part of paper above the metal and the other on top of a part of paper that is not above the metal. Have your partner look at the hands on the plate through an IR camera. The reason that we want to cover the metal up with a piece of paper is because we want to make sure that the difference of temperature we observe has nothing to do with the difference of emissivity--the ability of a substance to emit infrared light--between metal and the base material.

The first IR image shows the initial temperature distribution when the hands were on. The second one shows the temperature distribution after two minutes. It clearly shows that the hand above the metal strip is losing more thermal energy than the hand above paper.

This simple experiment, once again, demonstrates the transformative power of IR imaging. IR imaging experiments such as this are much easier to do than conventional experiments. They provide more intuitive, richer results in a snap. Imagine how many other experiments out there that can be transformed by this new instrument!

Energy3D: Design, print, cut, assemble, and test

Figure 1: Designing a building with

Energy3D.

We have come close to release an alpha version of Energy3D, a computational building science laboratory for simulating energy flow and designing energy efficiency. This program will allow you to design a building in a What-You-See-Is-What-You-Get style in 3D, just like Google SketchUp, and then evaluate its energy performance.

The alpha version will feature the Blueprint Wizard, which automatically deconstructs a 3D structure into 2D pieces, figures out which pieces are on the same 2D plane, generates a layout of all the planes, calculates the necessary lengths and angles, and prints them on a sequence of pages. Every piece is numbered and annotated with calculated geometric information adequate to guide students to cut it from provided constructional materials such as paper or foam board. The entire deconstruction process is animated so that the user has an intuitive understanding of the relationship between a house and the pieces in the blueprint.

Figure 2: Cutting and assembling the
building shown in Figure 1.

Students also have an option of fitting designs to the dimensions of constructional materials. For example, one option is to assemble a house using printer paper. If students select this option, Energy3D will automatically rescale every piece to guarantee that the largest piece can fit an A4 page and all the others will be proportionally rescaled accordingly. In this case, the texture and all the marks on a piece will be printed out, making it possible for students to construct a physical scale model that looks just like its computer counterpart.

Figure 3: Testing the scale model under
a table light and observing its thermal
signature with an IR camera.

If students are not sure where a piece is located during assembly, they can go back to Energy3D and click on the corresponding virtual piece in the 3D computer model, which will then be highlighted to indicate its position. Thus, the software tool remains useful during the hands-on construction. If any revision is needed after a physical scale model has been constructed, Energy3D’s blueprint feature can help students evaluate whether a modification is feasible by calculating how many pieces will need to be changed and whether there will be enough materials to make the changes.

Energy3D is developed by Drs. Saeid Nourian and Charles Xie and made possible by a grant awarded to the Concord Consortium by the National Science Foundation.