Experiment 1: February 20, 2010

Procedure

The main objective of the lab experiments was to measure the average water velocity coming out of the ports in the vena contracta region. Due to difficulty to ensure that the measured point was the point interest, three measurements were taken for each port. One measurement was done in the center of the port and one to each side of the port, 1cm apart. The purpose of the three measurements was to graph an approximate flow profile across each port and according to the results estimate what would be the water flow velocity in the vena contracta region. An example of the graph flow profile for each port is shown in the following graph.

The measurements were taken at 4 different points along the manifold, separated into at close to fourths as possible given the interference of bolts protruding from the walls of the flume. For each port, we maneuvered the ADV in front of each port until we thought we were in the the peak portion of the flow. We recorded data for 1 minute and then moved the ADV 1 cm to the left and 1 cm to the right of our first recording point to ensure that we captured the peak flow. We collected data at these points for 1 minute also.

In the analysis of our data, we took the mean of the velocities at each port for all 3 (and sometimes 4) measurements. Then we plotted the velocity profile for each port, assuming a Gaussian profile, 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 uniform manifold setup.

Results & Discussion

After collecting the data the way we did, we realized that there were many flaws in our procedure. First off, any 3 points can be fit to make a Gaussian curve so there was no real way to determine that we were at the peak flow for each port so we ran this experiment again with more accurate data collection techniques. For those results, check out Experiment 2. The results of this experiment are still displayed and discussed because they aren't necessarily bad, they just have the potential to be bad.

The results of our first experiment for a uniform manifold were not what we expected. Due to the expectation of pressure recovery dominating major losses (friction inside the manifold) we had expected the velocity coming out of the ports to actually increase along the length of the manifold. However, once the maximum velocity for each port was plotted against its distance down the manifold (see graph) it seemed that just the opposite trend was true. The velocity appeared to have peaked early on in the manifold and then gradually decreased after that.