Instructions
This Java applet (If you don't see anything above, please install Java 1.4) describes the spatiotemporal evolution of the KuramotoSivashinsky
equation and higher order variants. It is regulated by a number
of control buttons, of which the main button on top
regulate the type of equation.
Standard case is the
KuramotoSivashinsky equation. This can be directly exchanged ion the KuramotoS button
by a version
where the instability term is changed from a Laplacian to a Laplacian(Laplacian).
On the right of this main button is a number, which when negative,
replace the normal second order nonlinear term with a (dh/dx)**4.
When the number takes the absolute value of 2 then other variants comes into play:
Apart from the variation in possible equations, the applet allow
you to explore system size dependence, and whether boundaries are free
(1), periodic (0) or tilted to various degrees (>0).
Finally the applet allow you to play with artistic design of output,
with regulating
Color coding (numbers 1 to 7),
and what
criterium colors are assigned to interface (none(+1), height(+2), gradient(+3),
or growth speed(+4), sign switches background to black).
Finally you can adjust the drawing frequency and the speed of the simulations.
Good parameters for slow brning simulation is (system size=300,color=1,criterium=3,line density=2)

Philosophy
KuramotoSivashisky equation is the simplest model for a spatially
unstable system which, due to nonlinear couplings, reaches a steady
state dynamics where no parts is ahead all the time.
The equation describes how the front or interface h(x) develops in time.
x is here the spatial extent, and h the height.
The key idea in this equation is that if h(x) is ahead of its
immediate neighbors h(x1) and h(x+1), then h(x) advances faster.
This in itself is described by the equation
h(after)h(before) = (h(x)h(x1)) + (h(x)h(x+1))
or in formal equation form
dh/dt=Laplace(h)=dd(h)/ddx.
This instability is then ultimately remedied by corrections
associated to additional growth of h at positions where some
neighbors are very far ahead:
dh/dt = dd(h)/ddx  dddd(h)/ddddx + (dh/dx)(dh/dx)
In the applet we explore this equation as well as a number of
variants associated to higher order instability terms, as well as
higher order linear and non linear stabilization terms.
These particular variants are regulated by the number just right
on the to Kuramoto "botton" on the applet.
The large scale properties of the KS. equation
is similar to the KPZ equation, see Yakhot (1981)
and Sneppen et al (1992). Probably this is true for most
of the variants also.
Litterature:
Y. Kuramoto, T. Tsuzuki,
"Persistent propagation of concentration waves in
dissipative media far from thermal equilibrium"
Progr. Theoret. Phys. , 55 (1976) pp. 356–369
Sivashinsky, G. I. (1983)
"Instabilities, Pattern Formation and Turbulence in Flames"
Ann. Rev. Fluid Mech. 1B, 179.
V. Yakhot:
"Largescale properties of unstable systems governed by the KuramotoSivashinksi equation"
Phys. Rev. A 24, 642  644 (1981)
K.Sneppen, J.Krug, MHJensen, C.Jayaprakash, and T.Bohr.
"Dynamic scaling and crossover analysis for the Kuramoto  Sivashinsky equation."
Phys. Rev. A 46, R7351  R7354 (1992).
T. Sams, K. Sneppen, M.H. Jensen, C. Ellegaard, B.E.Christensen and U. Trane.
"Morphological instability in a growing yeast colony"
Physical Reviev Letters 79, 313 (1997).
