Energy Dissipation Optimization For circular Culverts

Chi Zhang Author

04/04/2021 Added

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This is a poster presentation made by Chi Zhang for the Student Research Days 2021. For any questions, contact the author at: chi92667544@gmail.com

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[00:00:00.920]Hello everyone, welcome to my poster.
[00:00:04.140]My name is Chi Zhang,
[00:00:05.370]I'm a master's student in the Department
[00:00:08.260]of Civil and Environmental Engineering here
[00:00:11.070]at University of Nebraska Lincoln.
[00:00:13.770]Today my poster topic is, "Energy Dissipation Optimization
[00:00:17.570]For Circular Culverts."
[00:00:20.900]Let's go to the introduction section.
[00:00:24.550]What is a highway culvert?
[00:00:27.150]A highway culvert it is a conduit
[00:00:28.950]that allows water to flow through the highway embankment.
[00:00:33.000]In the star program below,
[00:00:34.040]you can see, this is a highway culvert.
[00:00:38.720]This one in particular is called a Broken Back Culvert
[00:00:42.380]because of this inclined section.
[00:00:48.140]In this diagram, you can see
[00:00:49.700]that the this top section is the highway embankment
[00:00:54.930]and this is the culvert.
[00:00:57.728]The culvert outflow can cause erosion
[00:01:00.260]and scour to the receiving channel
[00:01:02.157]and lead to negative impacts.
[00:01:04.660]To mitigate these impacts,
[00:01:06.820]energy dissipation structures need to be designed
[00:01:09.460]and implemented at the culvert outlets.
[00:01:12.725]Currently, some of the existing
[00:01:15.200]energy dissipation structures include riprap basins,
[00:01:19.140]and rigid concrete structures
[00:01:21.218]which requires a significant cost
[00:01:23.990]of construction maintenance and right-of-way.
[00:01:28.150]Objective, as we just mentioned,
[00:01:31.800]some of the current energy dissipation methods
[00:01:36.810]have some disadvantages
[00:01:38.880]so we need to find ways to improve them.
[00:01:43.610]The objective of our research is to design
[00:01:46.000]and improve energy dissipation designs
[00:01:48.720]for circular culverts
[00:01:49.990]to mitigate downstream erosion, lessen sedimentation
[00:01:53.081]and blockage by debris, minimize the footprint
[00:01:57.430]of energy dissipation structure and reduce cost.
[00:02:02.950]Tasks, in our research project,
[00:02:09.040]we identified four tasks.
[00:02:12.590]First review of literature
[00:02:14.437]and existing infrastructure.
[00:02:17.310]Review literature's on energy dissipation structures,
[00:02:20.830]visit and review existing culvert
[00:02:23.300]energy dissipation structures.
[00:02:25.949]We'll talk more about review of literature
[00:02:30.230]in the next section.
[00:02:33.240]Two, selection of energy dissipators.
[00:02:36.330]select types of energy dissipators for testing.
[00:02:39.685]Our focus is on weir energy dissipators
[00:02:42.241]and staggered weir walls.
[00:02:44.980]These two types of dissipators have already been used
[00:02:48.060]by NDOT, but formal design procedures are needed.
[00:02:52.360]If you're a wondering what is weir energy dissipator
[00:02:55.374]and staggered weir wall?
[00:02:57.810]I will be talking about in the last section of this poster.
[00:03:02.420]By the way,
[00:03:03.253]NDOT means Nebraska Department Of Transportation.
[00:03:09.040]Three, model construction and testing.
[00:03:12.650]Build models for the selected dissipators
[00:03:15.260]in a laboratory, test different geometries
[00:03:18.520]of each model under range of for design flows.
[00:03:22.350]Data analysis, use data collected in the laboratory
[00:03:26.280]to develop an optimized design methodology.
[00:03:29.953]Incorporate the research outcome
[00:03:32.500]into NDOT design procedure.
[00:03:36.170]Since this is an ongoing project, we are not yet done
[00:03:43.210]with all of the tasks, but currently we're almost done
[00:03:49.280]with the literature review and selection
[00:03:51.960]of energy dissipators.
[00:03:53.840]We are currently working on model construction.
[00:03:59.780]literature review, in the literature review.
[00:04:03.570]We have looked at different types
[00:04:05.730]of energy dissipation structures
[00:04:07.810]and compare their advantages and disadvantages.
[00:04:11.790]Here's a diagram of some of these types.
[00:04:16.070]A is a Free Hydraulic Jump.
[00:04:18.360]Most energy dissipators use hydraulic jumps
[00:04:21.120]to dissipate energy, but free jumps are the simplest way
[00:04:25.040]in the sense that no additional appurtenances are needed
[00:04:28.550]to induce this hydraulic jump.
[00:04:33.370]Additional appurtenances are appurtenances like Baffles
[00:04:38.520]or Sills.
[00:04:40.780]B are Baffles.
[00:04:42.930]Baffles are these concrete blocks you can see in the basin.
[00:04:48.120]Baffles sort of one of the most common methods
[00:04:51.230]for energy dissipation being used.
[00:04:53.800]When flow impacts the baffles,
[00:04:57.510]baffles can dissipate energy in three ways.
[00:05:00.080]First, they can dissipate flow energy by creating friction.
[00:05:04.710]Second, they can redirect flow
[00:05:06.790]into other flow streams dissipating additional energy.
[00:05:11.000]Three, the baffles can induce immediate formation
[00:05:14.810]of jump to dissipate energy.
[00:05:19.780]C is a Sill.
[00:05:21.600]Sills are walls across a channel that force the water
[00:05:25.810]to go upwards and over them.
[00:05:30.550]When a water goes up
[00:05:31.990]and over hydraulic jumps can be induced.
[00:05:37.090]D is a Drop.
[00:05:39.800]Drops dissipates energy by impaction full recirculation
[00:05:44.730]and air entraining.
[00:05:47.930]E is a plunge Basin.
[00:05:50.720]Plunge Basins are very similar
[00:05:53.620]to Drops, but Plunge Basins use a deep pool
[00:05:59.390]and use sheer stress between the plunging jet
[00:06:03.340]and the water in the pool to dissipate energy.
[00:06:09.670]F is a counter flow mechanism.
[00:06:12.550]A counter flow device can change flow direction
[00:06:15.880]or turbulence and sheer can dissipate most of the energy.
[00:06:20.480]And E are flip Buckets.
[00:06:23.688]Flip Buckets direct part of the flow upwards
[00:06:26.180]so to induce a hydraulic jump.
[00:06:30.020]And H is a Design Basin.
[00:06:32.510]Design Basins use a combination
[00:06:36.380]of different mechanisms that we mentioned above.
[00:06:42.290]In summary there are four ways to reduce flow energy.
[00:06:45.940]The first one is to impinge water,
[00:06:49.590]impinge the incoming flow on a solid surface.
[00:06:53.160]The second one is to cause one part
[00:06:56.620]of the flow to travel in a different direction
[00:06:59.450]that another part of the flow to induce sheer.
[00:07:06.454]the third method is to entrain air.
[00:07:08.980]The fourth method is to induce the formation
[00:07:12.020]of hydraulic jumps.
[00:07:15.230]Model construction, to run experiments
[00:07:19.320]to determine the efficiency
[00:07:21.440]of our selected energy dissipators.
[00:07:26.130]We will have to build a test system first.
[00:07:29.700]The test system consists of three parts.
[00:07:33.500]The head tank, the model pipe, and the test basin.
[00:07:37.570]The head tank has a head gate on it
[00:07:39.980]to regulate the incoming flow depth.
[00:07:43.540]The model pipe represents the broken back culvert
[00:07:48.150]and the test basin is where
[00:07:50.120]we will place our model energy dissipators in.
[00:07:56.750]And here are two pictures
[00:07:59.650]of the construction progress we took last week.
[00:08:03.720]Methodology, the experimental model design relies
[00:08:07.530]on Froude Similarity.
[00:08:09.882]Froude similarity means that Froude number are constraint
[00:08:13.100]to be the same in the model and the prototype.
[00:08:16.688]Froude-based similitude prevails
[00:08:18.430]when viscous forces, surface tension forces,
[00:08:21.710]and compressibility forces are all negligible compared
[00:08:25.630]to gravitational forces.
[00:08:28.520]Based on Froude similitude,
[00:08:32.360]we can come up with a chart of different parameter ratios.
[00:08:42.190]From what I mentioned before,
[00:08:44.470]we have two different energy dissipators
[00:08:48.210]that we selected for testing.
[00:08:51.440]The first one is a weir energy dissipator.
[00:08:55.430]This is a top view of the weir energy dissipator
[00:08:58.890]and we have a uniform weir wall across the whole basin.
[00:09:06.240]Note that we have three weep holes
[00:09:08.780]on the wall to allow water to drain.
[00:09:13.760]So when there isn't enough incoming flow
[00:09:20.030]the weep holes will prevent the water from pounding here.
[00:09:25.670]The second one is staggered weir walls energy dissipator.
[00:09:29.770]Unlike the weir energy dissipator
[00:09:31.730]that has a uniform wall across the whole basin,
[00:09:39.350]we have three different segments of the weir walls.
[00:09:43.440]Yeah these are the two types of energy dissipators
[00:09:46.890]that we'll be testing in our test system.
[00:09:52.780]As for results, we don't have any results yet
[00:09:57.870]because this is an ongoing project
[00:10:02.220]but hopefully we'll get some results and conclusion soon.
[00:10:06.820]Thanks for watching.

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Energy Dissipation Optimization For circular Culverts

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