Building 24

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In response to hurricane Katrina, the US Army Corps of Engineers decided to increase the frontal protection on four pump stations in the greater New Orleans area.  Two of the pump stations (Bonnabel and Duncan) required the construction of wave breaks in Lake Pontchartrain as well as additional frontal protection in the form a T-walls.  ALDEN provided wave break design assistance and analysis for using Computational Fluid Dynamics (CFD) tools to evaluate wave break performance. Hydraulic performance of the discharge flow with wave breaks and extended discharge due to the T-wall installation was confirmed with physical hydraulic models.

3-D CFD was used to evaluate the effectiveness of several different wave break designs for reducing the height of the wave impacting the front of the pump station.  The wave spectrum used at the model boundaries was derived from the ADCIRC model.  Model results were used to improve the wave break design with the objective of minimizing the structure length and maximizing wave height reduction.  The models were also used to evaluate the potential impacts of the wave breaks on the erosion and deposition of sediment in the pump discharge canal.  Modifications derived in the CFD models were evaluated in two 1:30 scale physical models for final design verification.

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{id=61570585113, createdAt=1639074811163, updatedAt=1686596927993, path='waller-creek-tunnel-diversion', name='Waller Creek Tunnel Diversion', 1='{type=string, value=Waller Creek Tunnel Diversion}', 33='{type=number, value=0}', 34='{type=list, value=[{id=10, name='Civil Infrastructure', order=4, label='Civil Infrastructure'}, {id=16, name='Hydrology Hydraulics and Fluids', order=10, label='Hydrology Hydraulics and Fluids'}]}', 4='{type=string, value=Read how Alden designed, constructed and tested an undistorted 1:33 scale comprehensive physical model of the proposed storm water tunnel at Waller Creek.}', 5='{type=list, value=[{id=18, name='Water', order=3, label='Water'}]}', 6='{type=list, value=[{id=2, name='Spillways', order=1, label='Spillways'}]}', 7='{type=list, value=[{id=1, name='Physical Modeling', order=0, label='Physical Modeling'}, {id=2, name='Numerical Modeling', order=1, label='Numerical Modeling'}]}', 39='{type=string, value=waller-creek-tunnel-diversion}', 8='{type=string, value=

As part of Austin, Texas, Waller Creek has historically had problems with flooding, erosion and water quality. The addition of a proposed storm water tunnel was evaluated for hydraulic capacity, air entrainment and flow patterns in the tunnel entrances. 

Testing was conducted on an undistorted, 1:33 scale comprehensive physical model of the Waller Creek Tunnel.  The main morning glory spillway, two secondary spillways and the tunnel discharge were modeled.  The model was used to evaluate flow patterns and flow splits approaching the morning glory spillway, the entrainment of air at the spillway and the pressure losses in the system. Modifications were derived that split the flow more evenly and improved the performance of the spillway and tunnel.

In addition to the physical model, a 3D numeric model using Flow-3D was developed to examine the flow patterns into the morning glory spillway and the flow patterns entering the tunnel from the downstream laterals.  Modifications were developed in CFD and tested in the physical model to minimize the number of modifications required to the physical model to arrive at acceptable flow patterns.

 

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{id=61570585123, createdAt=1639074811187, updatedAt=1646949412491, path='tarrant-regional-water-district-integrated-pipeline-project', name='Tarrant Regional Water District Integrated Pipeline', 1='{type=string, value=Tarrant Regional Water District Integrated Pipeline Project}', 33='{type=number, value=0}', 34='{type=list, value=[{id=10, name='Civil Infrastructure', order=4, label='Civil Infrastructure'}]}', 4='{type=string, value=A 1:7 scale physical model looked at the performance of the Integrated Pipeline Project Joint Cedar Creek PS in accordance with HI Standards}', 5='{type=list, value=[{id=15, name='Energy', order=0, label='Energy'}, {id=18, name='Water', order=3, label='Water'}]}', 37='{type=list, value=[{id=102, name='Hydropower Field Services', order=53, label='Hydropower Field Services'}]}', 6='{type=list, value=[{id=5, name='Pump Intake', order=4, label='Pump Intake'}, {id=30, name='Hydropower', order=29, label='Hydropower'}]}', 7='{type=list, value=[{id=1, name='Physical Modeling', order=0, label='Physical Modeling'}]}', 39='{type=string, value=tarrant-regional-water-district-integrated-pipeline-project}', 8='{type=string, value=

Alden designed, constructed and tested a ~1:7 Froude scale physical hydraulic model to evaluate the hydraulic performance of the Tarrant Regional Water District Integrated Pipeline Project Joint Cedar Creek Pump Station in accordance with the Hydraulic Institute Standards (HIS).

The pump station consists of six 66 inch tee screens and 7 vertical pumps, each with a rated capacity of 27 to 49.4 million gallons per day (mgd). The maximum total flow for the pump station is 277 mgd, which corresponds to all seven pumps operating. The design requires each of the seven pumps to be placed into a depressed pump can located in the wet well floor.

Work Performed

Baseline tests were conducted to evaluate the pump hydraulic performance in terms of vortex formation, swirl at the pump impeller, and the velocity distribution approaching the pump impeller. The tests were conducted at two water levels; the normal water surface elevation and the maximum pool elevation. The test results identified the presence of unacceptable dye cAre subsurface vortices emanating from the can walls.

Two design modifications were developed and evaluated each of which met the HIS acceptance criteria. The first design modification included can-wall roughness vanes at 10 degree intervals to dissipate the unacceptable vortices. The second design modification included an inverted torus dish installed on the can floor (under the pump suction) as well as shortening the existing vertical can vanes. The dish modification was selected as the preferred modification since it demonstrated the most streamlined flow entering the pump.

Project Highlights

• Baseline design was an innovative combination of a traditional wet well configuration with recessed pump suction cans to minimize overall excavation costs.
• Two design modifications were provided to the client that satisfied the HIS acceptance criteria and the most cost-effective design was selected.

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