Convection Loops in a Numerical Gas The problem with showing this in a numerical gas is that the speed of convection flow is of the order a few tenths of a meter per second and the speed of the atoms is of order 300 meters per second. So we have to greatly enhance the convective flow by applying an artificial vortex velocity increment to the atoms at each animation frame. Since the left side of the box is considered to be the hot side and the right side is cold, the heat will flow upward on the left side (to regions of lower density) and it will flow downward on the right side. In order to simulate heat flow at the boundaries, each time an atom hits the left side, its horizontal speed is not only reversed in sign but its magnitude is increased by a fraction which I've lableled Heat Flow. On the right side the sign is also reversed but its magnitude is decreased by the same fraction. To simulate the effect of gravity, the value of the slider "gravity acceleration" is added to the vertical component of the velocity. This results in a noticeable increase in density at the lower end of the box. The most important feature of convection is the net average vertical flow, vy, of the atoms. The bounding box is divided into cells of size 25 pixels square and the averaged direction of the atoms in each cell is shown by an arrow. After all iterations have been completed, or when "Show Contours" is checked, then a color coded contour plot of vy is shown. In order to get a stable value of the convection flow, at least a few minutes of run time is require for each set of parameters chosen. The small black arrows show the averaged direction of atom or disc velocity at each cell location. The plots Vs y show the density and energy. The plots Vs x show the averaged density, energy and vertical velocity.
rad nD g vort dvx nIts Single Step Show Discs Show Contours