Innovative Technology Solutions Corporation
ITSC Fluids Movie Archive
Computational Fluid Dynamics (CFD) and Thermal Analysis.
Scientific visualization and animation is becoming indispensable in
modern engineering analysis where enormous amounts of data must be processed
in order to better understand the output of typical CFD codes. Many engineering
analysis require complex fluid dynamic calculations to resolve pressures,
temperatures, densities and other field variables. In this page are several
animation's that demonstrate the wide variety of fluid flow problems that
ITS Corporation can address. The animation's chosen are those that are
encountered in classic fluid dynamics problems, as well as situations that
are familiar to many people.
Example 1a (150K)
A heated plate with a thick initial thermal boundary layer is suddenly
accelerated to 5 m/s in air. The thermal boundary layer is swept downstream
and rolls up into a pair of shed vorticies. Temperature contours are shown
in the movie making the flow visible. The Reynolds number of the flow is
200,000, well beyond the critical Reynolds number of 40 where vortex shedding
begins. Thus the wake region is unstable and breaks up into a Von Karman
vortex street. Vortex shedding from a rectangular bar is demonstrated in
Example 1b (75k).
The periodic nature of the Von-Karman vortex street is best illustrated
in Example 1c (63K)
which shows the vortex street created by a flat plate. This movie only
includes a single cycle of the phenomenon, therefore configure your (MPEG)
viewer to play the movie in a continuous loop.
Example 2a (84K)
A fire showing the formation of semi - periodic eddies. This animation
shows the location of hot spots and the cooler vapor dome overlaying a
pool of hydrocarbon fuel. In example
2b (187K) a solid object moves horizontally across the fire. The calculation
demonstrates the effect of moving structure in a flow calculation. In example
2c (132K) the object is oriented vertically demonstrating the phenomenon
of a flame holder, where a wake behind an object, created by the large
indraft of air, captures and holds a flame. Example
2d (536K) This calculation is identical to example 2-a except that
the structure is moving down to the base of the flame. At the base the
flame attaches itself completely to the object. Example
2E (321K) demonstrates a vortex shedding fire-object interaction. The
fire oscilliates about a cylinder due to the vortex shedding phenomenon
demonstrated in examples 1a-c. Example 2F
shows a rectagular object in an engulfing fire with a crosswind.
Example 3a (350K)
The classic Raleigh-Taylor instability is illustrated in this calculation.
When a high density fluid is placed over a low density fluid an unstable
condition exists. The instability causes the two fluids to exchange places.
In this example an initial perturbation is placed in the center in order
to initiate the instability. The size of the box is quite large so that
the exchange of fluids takes place in a fairly turbulent manner. An asymetric
fluid exchange occurs when a step in fluid level is used as an initial
condition, as shown in example
3b (321K). The large difference in the fluid behavior contrasted
in examples 3a and 3b demonstrates the high sensitivity to initial conditions
for this type of instability. The effect of fluid viscosity is demonstrated
in example 3c (266K).
The same parameters of size, initial perturbation, and density difference,
but a much higher viscosity was used. The high viscosity serves to damp
out the high degree of turbulence found in the previous examples allowing
the large wavelength instabilities to dominate the flow behavior.
The Kelvin-Helmholtz is another classic flow instability. This instability
is characterised by waves that appear between two superposed fluids of
differing densities and velocities. A familiar example are the ripples
that form when wind flows over a pool of water. Example
4a (44K) demonstrates the Kelvin instabiliy wherein two stably stratified
fluids are flowing from left to right with the uppermost low density fluid
traveling 3.5 times faster than the lower heavy fluid. Another example
of the Kelvin-Helmholtz instability are waves that grow on jets of high
or low density fluid, such as the hot bouyant jet of gas shown in example
When a layer of fluid is heated from below and cooled from above the
resulting convection patterns are often called the Benard instability.
The next example
(104K) illustrates the transition to convection of an initially quiescent
layer of fluid that has a vertically unstable temperature gradient. The
fluid is low Prandtl number (Pr = 0.0125 = high thermal conductivity).
Another example (120K)
shows the tempmerature contours from a slightly higher Prandtl number fluid
(Pr = 2.25 low thermal conductivity)
Compressible flow calculations usually involve shock wave dynamics.
In this set of examples shock wave diffraction and interaction with solid
objects will be demonstrated. Example
5a (81K) shows the density contours that result as a shock wave passes
by a cylinder. Example
5b (139K) shows the density contours that result when shock wave passes
over a wedge. A third example
5c (468K) shows the density contours resulting from the propagation
of a shock wave though a structure with partitions (such as a muffler).
The far right partition contains a combustible mixture with an ignition
point at the beginning of the calculation .This example demonstrates shock
induced flame propagation, explosive chemical reaction, in addition to
reflection, refraction, and dissipation of shock waves.
Gravity wave phenomena is a familiar process to virtually everyone.
The most common example is water waves at the beach. A less familiar example
are gravity waves in a fluid with a stable density stratification such
a two gas layers at different temperatures. Example
6a(248K) shows sloshing gravity waves in a tank with a sloping sidewall.
Another gravitational instability is the slumping of a high density fluid
into a low density fluid. Example 6b (357K) is very
similar to the Raleigh-Taylor instability examples except that the initial
condition is a vertical slab of cold dense gas surrounded by slabs of warmer
low desity gas.
Material transport involves the simultaeous solution of
the Navier Stokes equations along with a material transport equation. Debris
transport from a through a complex geometry is shown in this example