The adding of oxygen supply to the water mass is needed to promote the activity of microorganism such as bacteria and algae where it changes the colloid and other undissolved carbon based organic
materials into gases and other vaporizing material and other tissues.
3.2 The use of High Power in other Aerating Systems
Other aerating system is actually not highly efficient in terms of cost if compared to the value of energy cost that is used. A cascade aerator that is proposed in this research will ensure that maximum
efficiency in all aspects such as cost, aerating rate and space
.
3.3 High Operational Cost and Maintenance Cost of other Types of Aerating System other than Cascade Aerator
For the water that already has the potential energy like in the rivers and multi level lakes or positioned in a higher level, the cost of this collapses into zero because the water is no longer needed to be
pumped onto a higher level. While the operational cost of a cascade aerator is only on the cost of ensuring the aerating equipment functioning normally without any waste or floating solids from the
water that has been stuck on the cascade dam that may affect the transfer of oxygen into the water mass compared to other aerator that needs spare parts and also high expertise for maintenance.
3.4 The Need to Generate Bubbles or Air Balls without Cavitation to the Aerator
The increase in the space of the interphase between the air and the water will increase the rate of oxygen transfer to the water mass Robert Oscar 2002. Therefore, the increase in bubbles and air
balls in the water will increase the oxygen transfer rate in the interphase region and will be one of the main criterias that is needed to be analyzed and studied comprehensively to ensure the optimization of
the physical design on the cascade aerator.
3.5 Cavitation and Air Entrapment
The presence of air bubbles in the water flow will give an impact to the explosive cavitation ball mechanism, diverting the water hammer jet away from the surface of the solid. As an awareness to the
dangers that is caused by the activities of cavitation, this research has to take into account the effects of cavitation in the process of developing and designing so that the geometry of the cascade aerator that
will be designed does not allow the unexpected process of cavitation to happen.
4 METHODOLOGY
4.1 Formula and design of an efficient cascade aerator based on optimal values
The design of a cascade aerator based on a efficient cascade water jet plunge is governed by the optimum level that has been predefined from laboratory test and the restrictions or rules that has been
found by early researchers. The velocity of the impact or the velocity of the colliding water jet to the surface of the receiving water tank to give out a formula of the rate of water flow into the cascade
aerator.
Figure 1: Schematic cross section of the water flow cascade. With reference to Figure 1 and using the kinetic hydraulic fall formula, the velocity of the impact to the
lower water tank surface can be calculated .The velocity of the water jet as soon as it exits the nozzle is V
o
Refer figure 1 di above. While the velocity of the water jet velocity during the impact onto the surface of the receiving water is given by the equation below:
V
1
sin = V
o
sin + gt
1
Thus V
1
=
V sin φ+ gt
sin θ
2 With g gravitational acceleration,ms
-2
, t time taken for the water jet to reach the surface of the water, s, θ angle of the water jet with respect to the horizontal plane during impact, unit degrees,
angle of the water jet with the projection as it exits the nozzle, unit degrees.
Velocity V
o
can be obtained from the equation below: Velocity of Nozzle Exit, V
n
= C
v
2gh 3 with C
v
as coefficient of velocity of jet at nozzle = C
c
C
d
coefficient of contraction coefficient of exit , Coefficient of contraction = d
1 2
d
2 2
inner diameter of nozzle tube outer diameter of nozzle tube with the height of the cascade H and the initial jet velocity V
o
, the kinetic water cascade equation is,
H = V
o
sin t + ½ gt
2
4 On the optimal jet cascade, as soon as it exits the nozzle is
, and H know thus the time taken t taken to reach the surface os the lower surface of the water tank is the solver to the quadratic equation above.
Knowing the value of V
o
, a rate of the water flow through the nozzle can be determined using one given by the water flow equation as below:
Q
n
= V
o
x A
n
5 With A
n
the size of the inner diameter of the cascade nozzle and Q
n
= the rate of water in a nozzle jet cascade.
Thus the rate of water flow for a nozzle is given by the equation below:
Q
n
= V
o
x d
o 2
6 4
While the rate of water flow intake for the whole aerator dam is given by the equation as shown: Q
ov
= N x V
o
x d
o 2
7 4
with, Q
ov
Rate of water flow for the whole cascade aerator and N The no. of nozzle on the circumfrence of the first cascade tank.
5 RESULTS AND DISCUSSION
Based on empirical data through experimentation, a simplified result obtained were value for depth of lower water tank, 190.75 mm , inner diameter of the cascade jet nozzle, 18.62 mm, height of cascade ,
327.5 mm, angle of water cascade Incident angle of water surface, 55.5 , depth of upper water tank ,
515 mm. The optimal values above are again verified with a computational simulation study to ensure that the
validaty of the empirical results compared to the theoretical values. When it has been verified both research, the optimal levels above can be made as a baseline to designa cascade aerator based on an
efficient cascade water jet.
5.1 Computer simulation results for optimal parameter values that is obtained from the graphical verification from the optimization curve
The optimal value that was obtained from the curve that is the depth of the reservoir water tank is 190mm, Inner diameter of the cascade jet nozzle 19mm, height of the cascade 330mm, water cascade
angle 50 ° and depth of the upper water tank 515mm, is tested again by using simulation. The results that were obtained are as figure below:
Figure 2 : Graphical Computer Simulation of the Water Jet Cascade on The Depth of the Water Tank Below optimum levels which is at 190mm
Figure 3 : Graphical Computer Simulation of the Water Jet Cascade on the Inner Diameter Optimal Cascade Jet which is at 19 mm
Figure 4 : Graphical Computer Simulation of the Water Jet Cascade at the Optimal Height of Water Jet Cascade which is at 330 mm
Figure 5 : Graphical Computer Simulation of a Cascade Water Jet at the Optimal Cascade Water Jet Angle of 50°
Figure 6 : Graphical Computer Simulation of the Water Jet Cascade at the Optimal Water Tank Depth which is at 515mm
5.2 Optimal cascade aerator design based on the cascade water jet
