A novel Simulation model for working of heart using collapsible bladder
A LABORATORY SIMULATION
MODEL OF HEART USING A
LARGE COLLAPSIBLE BLADDER
Dr Uday Prashant
Why Pulsatile flow
• Development of atherosclerosis is dependant upon
the vessel geometries, branching points and fluid
• It has been observed that early atherosclerotic
lesions develop preferentially in the vicinity of
arterial branching and
• curvature where blood flow patterns are complex
• The most recent such studies implicate oscillatory shear stress
on vessel walls in the development of early lesions.
• Although the biological basis of these observations remains
to be determined, flow-induced vascular endothelial
dysfunction is thought to be involved.
• Therefore, studies of arterial flow fields that aim to generate
physiologically relevant flow information need to be based on
realistic geometries and
• to incorporate blood flow pulsatility
• There have been several experiments to produce pulsatile
flow in laboratory
Requirements of pulsatile flow generators
• It is quite challenging to give more realistic picture of
pulsatile flow in heart without resorting to actual
humans or animals for better understanding of
pathophysiology of atherosclerosis.
• They should be easily manufactured and not very
expensive and complicated.
• Should give actual rapid fluid pressure surges as seen in
• Same model should give wide pressure fluctuations seen
in various chambers like aorta, ventricles and atria
• Should not damage blood elements
Displacement and Vacuum pulsatile
pump but they fail to produce rapid
fluid transits seen in vivo
• The gear pumps used by Issartier et al.,
Petersen et al., etc produce cavitation and
damage to suspended particles.
• Peristaltic pumps which were developed later
to prevent particle damage of gear pumps
suffer the drawback of production of only
limited subset of waveforms even if they are
computer controlled and the systems lack
flexibility to operate under wide flow
• Microcomputer controlled piston pumps are
very complicated, difficult to set up and
cumbersome to operate
My discovery involves two basic concepts
1) Flow induced collapse in collapsible tubes
2) Fluid structure interactions in flexible tubes
Method of construction
• To a source water that has very negligible head is connected to
collapsing rubber bladder.
• This rubber bladder is highly elastic and the lower end is connected
to flexible thin garden hosepipe made of synthetic rubber or PVC.
• This flexible rubber tube hangs freely after taking initial ‘U’ shaped
• The distal end is open to atmosphere and all the connections are
• If the vertical height from the tap to balloon is less than from
ground to the balloon (h1 > ho) and during certain range of flow
• it exhibits an interesting phenomenon of alternate collapse
(buckling) and opening, along with generation of pulsatile flow of
Schematic diagram of novel pulsatile
Other Potential uses
• I postulated seeing the vigor of contractions of
• May be it can be used as a novel hydroelectric
• Did some initial experiments
• Awaiting funds for further research.
• Mainly used to provoke interest in investors
on this new technology which I developed
Principle of working
• Once the bladder and pipes are completely filled & flow is
fully established due to negative atmospheric pressure
created by Venturi effect, the rubber bladder collapses
and stops the flow.
• The flow is instantaneously reduced. Steady continuous
flow is converted to unsteady pulsatile flow by collapsible
• There is large negative pressure “WAVE” generated
travelling at speed of sound in water.
• This pressure wave interacts with specially designed
flexible tubes with elastic supports and transmits energy.
Types of Coupling
• The most significant mechanism is
- the junction coupling others are
- Poisson and
- friction coupling
• Wiggert D.C, Tijsseling, A. S (2001)- Junction coupling is taken place
due to unsupported discrete points of the piping systems such as
unrestrained valves, junctions, closed ends, pumps, etc.
• MOC (Method of Charecteristics) and FEM (Finite Element Method)
are used to solve structural equations.
Frequency and amplitude of oscillations
Frequency of oscillations per min
Amplitude of vibrations in mm
Flow rate in ml/sec
Variation of frequency with height at constant flow rate of
frequency and amplitude of oscillations
frequency of oscillatons
Amplitude of oscillations
Vertical height in cm
The figure below shows the deformation of a thin-walled elastic tube
which conveys a viscous flow (the direction of the flow is from left to
• In its undeformed state, the tube is cylindrical and the ends of the tube
are held open (think of a thin-walled rubber tube, mounted on two rigid
• As we increase the external pressure [from (a) to (d)], the tube buckles
and deforms strongly.
• The reduction in the tube's cross sectional area changes its flow resistance
and thereby the pressure distribution in the fluid, which in turn affects the
• This is a classical example for a large-displacement fluid-structure
interaction problem for which many applications exist in biomechanics
e.g. blood flow in veins and arteries, flow of air in the bronchial
airways, generation of wheeze, korokoff sounds during BP measurements
• The photograph below shows the experimental setup used to
investigate the viscous flow through elastic tubes:
• Inside a pressure chamber, a thin-walled rubber tube is
mounted on rigid tubes.
• A syringe pump at the upstream end pumps highly viscous
silicon oil through the tubes.
• The volume flux and the pressure inside the pressure
chamber can be controlled independently to induce the
The figure above shows an example of the two Finite Element meshes used
to solve the problem of Stokes flow in an elastic tube.
STEADY FLOW: CHOKING, FLOW LIMITATION AND ELASTIC
Theory of Waterhammer
• The bladder once collapsed must remain in same
state under ordinary conditions.
• But due to ingenious use of flexible tube, the ‘U’
shape bend and elastic supports lead to
• Complex fluid structure interactions which cause
the bladder to open automatically and produce
• Water hammer effect is produced because during
collapse of bladder the velocity of flow changes
too rapidly < 4L/C where L is length of tube and C
is velocity of sound in water (1200m/sec)
• Water hammer is produced commonly in
dams or in houses, hotels, train bathroom taps
or valves suddenly opened or closed loud
bang is heard with vibrations of pipes mostly
at bends and junctions
• Can be as loud as a thunder
• Hardly any useful applications described and
mostly engineers interest is to suppress it to
Similar to hydraulic ram pump
• A hydraulic ram or impulse pump is a device
which uses the energy of falling water to lift a
lesser amount of water to a higher elevation than
• Each impulse creates waterhammer which pumps
water high much above from which water flows.
• The water hammer and pulsatile flow are created
by operation of solid valves but it doesn’t
resemble to collapse produced by beating heart
The last terms in the Eqs (9B) and (10), modelling friction coupling, depend on the
relative velocity V - uz
p/ = 998.2 kg/m3, cr = 1257 m/s and AV = 0.3
m/s), but deviates from it when time proceeds
Wiggert DC and Tijsseling AS (2001), Fluid transients and fluid-structure
interaction in flexible liquid-filled piping,
ASME Applied Mechanics Reviews 54 455-481
• Our model also produces similar pressure
tracings depending upon location of pressure
• No need to separately construct different
prototypes for mimicking different chambers
• All can be analyzed in one model and
• By this model we develop alternative simulative in vitro
model for pulsatile flow fluid mechanics in both
These are very cheap and easy to construct than
complicated design models shown earlier.
More realistic reproduction of pressure waves than other
models without involving complex gears, piston
pumps, actuators, micro computers
Does not damage blood elements
• Can be used as micro pump in fuel injection
system and drug manufacturing units.
• Can be used in particulate filtration unit
where pulsatile flow enhances rate of
particulate filtration process.
• Can be used as novel mini hydroelectric
When something is new, they say
"it's not true".
When its truth becomes obvious, they say
"it's not important".
When its importance cannot be
denied, they reason, "it's not new".