2010 Inlet Manifold Research and PIV Measurements

Team Members

Rami Bechara
Gonzalo Caprario
Vanish Grover
Nicolas Pautassi
Julia Schoen
Arthur Shull

Introduction

The design challenge for the Inlet Manifold Research Team is to design an inlet manifold for the sedimentation tank that meets the following constraints:

• Maintain the velocity of the water high enough to prevent sedimentation prior to the tank
• Obtain an even distribution of the influent along the length of the sedimentation tank
• re-suspend the flocs in the bottom of the sedimentation tanks to promote a floc blanket
• prevent floc breakup
• test the theories of manifold flow and the effects of pressure recovery

The inlet manifold consists of a PVC pipe with a row of drilled holes facing down. The jets coming out of the ports will prevent floc accumulation in the bottom of the sedimentation tanks and hopefully the velocity will keep the floc in suspension to create a floc blanket.

Read more about the inlet manifold design.

Objectives

The objectives of this research team are to experimentally test the inlet manifold recreating the same conditions that will face in a real AguaClara plant, and modify the design based on the results.

To begin with, we calculated the manifold dimensions which include:

• Pipe diameter
• Ports' diameter
• Ports' spacing

The calculations for this experiment were based on the Agalteca design flow and tank dimensions.

Based on theoretical information about manifolds, the initial idea is to prove that to create an evenly distributed flow throughout the different ports of the manifold, we would have to taper the pipe to have the same velocity along the manifold and therefore the same flow in each port.

begin
By looking at this image on the right, we can observe that as the water runs through the manifold, the HGL decreases due to major head losses (friction losses along the pipe walls). But, as the water passes the port and the flow inside the manifold decreases, the velocity inside the manifold decreases as well. As a consequence we should observe a decrease in the HGL slope after each port. But the most interesting aspect of this study, is that as the velocity decreases we will have a pressure increase after each port (therefore an increase in the HGL if we keep the elevation constant, as is the case). This is what we call pressure recovery! Considering the major head loss along the manifold are small, due to the low velocities we have to prevent floc breakup,
with the study, we should calculate a manifold with a constant diameter for the design flow. The results of that calculation proposed a 6" PVC pipe with 1" ports spaced 5 cm center to center (total 57 ports). Drilling Process Images

These [calculations|Inlet Manifold Research and PIV measurements^Agalteca Manifold Design 1.xmcd] assumed that the sum of the areas of the vena contracta of the ports should equal the cross sectional area of the pipe.

The next step is to recreate in the lab the conditions of that manifold in the Agalteca plant. To do this, a submersible pump with the design flow will recreate the inlet flow and the whole manifold replica, will be installed in a flume to begin the flow testing.

The velocities coming out of the ports will be measured using an ADV as shown in the following image.

The results obtained by this measurements will be plotted and compared to the theoretical expected values.

Based on the obtained results, the manifold should be modified and the testing procedure should be repeated until even flow distribution is achieved.

Experimental Methods and Results

Setup and Procedure

The manifold we designed is a 10' long, 6" PVC pipe with 1" diameter holes drilled every 5cm. The manifold had water pumped through it at a rate of 3.8 L/sec (roughly 1 gallon/min) and the water flows through a whole 10' section of 6" PVC pipe before it gets to the manifold to ensure that the effects of the pump have dissipated in the pipe. The manifold is suspended 14" above the bed of the flume by U-clamps and the manifold is spaced 7" from the flume wall to make sure that it runs parallel to the flume bed and wall. We double checked this by measuring the distance from the flume wall and flume bed both at the beginning of the manifold and at the end of the manifold. The ports of the manifold are positioned so that the jets exiting from them run parallel to the bottom of the tank.

The Acoustic Doppler Velocimeter (ADV) used to take velocity readings was mounted to a beam running across the width of the flume. The ADV was positioned so that it was aimed head on into the ports (so it also lies parallel to the bed of the flume) at a fixed distance of 17 cm from the port openings.

The measurements were taken every 5-6 ports, which gave us 10 different data points along the manifold. For each port, we maneuvered the ADV to the edge of the port hole. We then took measurements as we moved the ADV across the port in steps of 0.5cm. We recorded data for approximately 1 minute and then moved the ADV 0.5cm further and measured again until we were sure we had captured the entire jet profile.

In the analysis of our data, we took the mean of the velocities at each port. Then we plotted the velocity profile for each port and estimated the maximum flow rate at each port. These calculations were then plotted along the length of the manifold to give a velocity profile for the each manifold setup.

Results

Experiment 1: 10' Uniform Manifold Am/Avenacontracta=1
Experiment 2: 10' Uniform Manifold Am/Avenacontracta=1, take 2
Experiment 3: 20' Uniform Manifold Am/Avenacontracta=0.5
Experiment 4: 10' Uniform Manifold Am/Avenacontracta=0.5
Experiment 5: Manifold Cross-Sectional Measurements

Stay up-to-date on this project by checking
the Meeting Minutes, [goals] and Challenges for Future Semesters.

Current Research Teams

Spring 2010 Inlet Manifold Research Team

• Redesigning the inlet manifold for the sedimentation tank in an effort to maintain constant flow out of all of the ports.