h1. Lamella Design Program
h2. Lamella Design Program Inputs and Outputs
[Lamella Program Inputs|Lamella Design Program Inputs]
[Lamella Program Outputs|Lamella Design Program Outputs]
h2. Lamella Design Program Algorithm
The Lamella Design Program uses threefour constraints to determine design values, the critical velocity of 10 m/day, the upward velocity at the bottom of the tank of 70 m/day, the minimum space between the lamella and the predetermined length of the sedimentation tank. All of these constraints come together to determine the spacinglength of the lamella. The minimum whichspacing isbetween the most important value in terms of functionality. lamella was determine via laboratory experiments, at spacing closer than 2 cm failure occured. The length of the sedimentation tank is set by the [Sedimentation Program|Sedimentation Design program]. The critical velocity is the rate at which a particle must fall to ensure that it settles out within the plate settlers. If the critical velocity is too large, flocs will not settle out, and will remain in the water sent through the distribution system for drinking. However, a small critical velocity comes at the expense of a large cross sectional tank area (so it is not practical to have an unnecessarily small critical velocity). The upward velocity at the bottom of the tank is important for sludge blanket formation, too high and the blanket will form totoo thin and will not capture particles, too slow and the blanket will either settle out instead of remaining suspended or the shear value in the blanket will be so high that flocs will get broken up in the blanket. Either of these issues would result in the sludge blanket being detrimental to the sedimentation process.
The program starts by determining the height availableneeded for the lamella.launders Afterabove the available height is determined the length of the lamella can be found given an assumed angle of 60deg.
InThis orderheight toneeded findfor the verticallaunders heightis availablesame foras the lamella, first the heightdepth of the water needed above the lamella is found. This value is simply a function of leaving enough available headloss through the exit launder about the lamella to keep it properly submerged.
{include:H.SedAbove}
TheTo distancedetermine belowwhat the lamella, H.SedBelowSlope, was found in the sedimentation program and based offhow long the lamella need to be, firs the active length of the tank fraction givenand by the user.upward The vertical height available forvelocity under the lamella must isbe simplydetermined, thebut remainderboth of these thevalues waterare depthdependent inupon the sedimentationlength tank afterof the bottomlamella. slopesTherefore, andan theiterative spaceloop neededof abovethe thefollowing lamellathree hasequations beenwas accountedcreated for.
{include:H.SedPlate}
The lenghtto determine length of the lamella:
{include:L.SedPlate}.
The nextlength step is to determinefound in the spaceabove betweenloop theis lamellaan needed to satisfy the critical velocityestimated length, theThe activeactual upwardlamella velocitylength andis activedependent tankon length. The active length of the tankplastic issheeting thematerial lengththat inis which water will be able to flow up throughavailable.
From this number the actual upward velocity under the lamella. The 60ddeg angle and the channelsactual createspace anneeded inactive area inbetween the tanklamella through which water does not flow. The inactive length is found below.
{include:L.SedInactive}
The actvie upward velocity is the flow through the sedimentation tank divided by the cross sectional area of the active portion of the sedimentation tank.
Upward Velocity under the Active Area below theare recalculated.
Using the available active length in the sedimentation tank and the known length of the lamella the number of lamella that can fit in the tank can be calculated as follows.
The Number of Lamella:
{include:VN.SedUpActiveBelowSedPlate}
NowThe thethickness criticalof spacingthe betweenlamella thecontributes lamellaa cansmall bebut found.Thesignificant equationdead belowzone determinesto the perpendicular distance center to center between lamella. Typically the lamella spacing should be around 5cm apart. Closer distances are thought to possibly lead to improper floc settling and possible clogging.
Distance from Center to Center between Lamella:
{include:Btank. Now that the exact number of lamella has been calculated, more accurate values of active tank length, upward velocity, and critical velocity can be found. Calculations for these values are shown below.
Vertical height taken up by the lamella:
{include:H.SedPlate}
Horizontal Distance Center to Center between Lamella:
{include:B.SedPlateHorizontal}
TheOpen open spaceSpace between the lamella is the area for water to flow up through the lamella. This spacing is the center to center spacing between the lamella (B.SedPlate) minus the thickness of the lamella material.
Open Space between Lamella:
{include:S.SedPlate}
Active Length of the Tank:
{include:L.SedActive}
The Actual Upward Velocity at the Bottom of the Tank:
{include:V.SedUp}
The Critical Velocity Up through the Lamella:
{include:SV.SedPlateSedC}
The numberheight of lamellathe placedwater in the sedimentation tank can now isbe determined byas the maximummax numberheight oftaken lamella that can fit inup by the tank.inlet Thismanifold numberand isthe functionchannels, ofor the geometryinlet ofmanifold, thelamella, spacelamella availableframe, and the following equation is used.
The Number of Lamella:
{include:N.SedPlate}
Without knowing the exact number of lamella that will be placed in the tank it is not possible to calculate the exact parameters of the tank. Now that the exact number of lamella has been calculated, more accurate values of active tank length, upward velocity, and critical velocity can be found. Calculations for these values are shown below.
Active Length of the Tank:
{include:L.SedActive}
The Actual Upward Velocity at the Bottom of the Tank:
{include:V.SedUp}
The Critical Velocity Up through the Lamella:
{include:V.SedC}launder.
For tanks where there are more than one bay per tank, a wall is constructed to separate bays. This wall has height that comes up to the top of ledge that supports the lamella frame. This was done so that the wall can lend support to the center section of the lamella. The equation used is as follows.
The inlet manifold is formed by laying concrete plates next to each other. The width of each slope plate is defined by the user. If the length of the sedimentation tank is not equally divided by the width of the plate, there is a leftover space that needs to be filled by a fraction of a plate. This is used for construction purposes.
{latex}
\large
$$
{\rm{W}}_{{\rm{SedSlopePlateRemaining}}} = L_{Sed} - N_{SedPorts} \cdot W_{SedSlopePlate}
$$
{latex}
| 